Subjectively, CHECK_INTEGRITY_INCLUDING_EXTENT_DATA is quite long and
calling it CHECK_INTEGRITY_DATA still keeps the meaning and matches the
mount option name.
Reviewed-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

While stress testing our error handling I noticed that sometimes we
would still commit the transaction even though we had aborted the
transaction.

Currently we track if a trans handle has dirtied any metadata, and if it
hasn't we mark the filesystem as having an error (so no new transactions
can be started), but we will allow the current transaction to complete
as we do not mark the transaction itself as having been aborted.

This sounds good in theory, but we were not properly tracking IO errors
in btrfs_finish_ordered_io, and thus committing the transaction with
bogus free space data.  This isn't necessarily a problem per-se with the
free space cache, as the other guards in place would have kept us from
accepting the free space cache as valid, but highlights a real world
case where we had a bug and could have corrupted the filesystem because
of it.

This "skip abort on empty trans handle" is nice in theory, but assumes
we have perfect error handling everywhere, which we clearly do not.
Also we do not allow further transactions to be started, so all this
does is save the last transaction that was happening, which doesn't
necessarily gain us anything other than the potential for real
corruption.

Remove this particular bit of code, if we decide we need to abort the
transaction then abort the current one and keep us from doing real harm
to the file system, regardless of whether this specific trans handle
dirtied anything or not.
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Btrfs uses internally mapped u64 address space for all its metadata.
Due to the page cache limit on 32bit systems, btrfs can't access
metadata at or beyond (ULONG_MAX + 1) << PAGE_SHIFT. See
how MAX_LFS_FILESIZE and page::index are defined.  This is 16T for 4K
page size while 256T for 64K page size.

Users can have a filesystem which doesn't have metadata beyond the
boundary at mount time, but later balance can cause it to create
metadata beyond the boundary.

And modification to MM layer is unrealistic just for such minor use
case. We can't do more than to prevent mounting such filesystem or warn
early when the numbers are still within the limits.

To address such problem, this patch will introduce the following checks:

- Mount time rejection
  This will reject any fs which has metadata chunk at or beyond the
  boundary.

- Mount time early warning
  If there is any metadata chunk beyond 5/8th of the boundary, we do an
  early warning and hope the end user will see it.

- Runtime extent buffer rejection
  If we're going to allocate an extent buffer at or beyond the boundary,
  reject such request with EOVERFLOW.
  This is definitely going to cause problems like transaction abort, but
  we have no better ways.

- Runtime extent buffer early warning
  If an extent buffer beyond 5/8th of the max file size is allocated, do
  an early warning.

Above error/warning message will only be printed once for each fs to
reduce dmesg flood.

If the mount is rejected, the filesystem will be mountable only on a
64bit host.

Link: https://lore.kernel.org/linux-btrfs/1783f16d-7a28-80e6-4c32-fdf19b705ed0@gmx.com/Reported-by: NErik Jensen <erikjensen@rkjnsn.net>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The intended logic of the check is to catch cases where the desired
free_space_tree setting doesn't match the mounted setting, and the
remount is anything but ro->rw. However, it makes the mistake of
checking equality on a masked integer (btrfs_test_opt) against a boolean
(btrfs_fs_compat_ro).

If you run the reproducer:
  $ mount -o space_cache=v2 dev mnt
  $ mount -o remount,ro mnt

you would expect no warning, because the remount is not attempting to
change the free space tree setting, but we do see the warning.

To fix this, add explicit bool type casts to the condition.

I tested a variety of transitions:
sudo mount -o space_cache=v2 /dev/vg0/lv0 mnt/lol
(fst enabled)
mount -o remount,ro mnt/lol
(no warning, no fst change)
sudo mount -o remount,rw,space_cache=v1,clear_cache
(no warning, ro->rw)
sudo mount -o remount,rw,space_cache=v2 mnt
(warning, rw->rw with change)
sudo mount -o remount,ro mnt
(no warning, no fst change)
sudo mount -o remount,rw,space_cache=v2 mnt
(no warning, no fst change)
Reported-by: NChris Murphy <lists@colorremedies.com>
CC: stable@vger.kernel.org # 5.11
Signed-off-by: NBoris Burkov <boris@bur.io>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

This adds the basic RO mount ability for 4K sector size on 64K page
system.

Currently we only plan to support 4K and 64K page system.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

For sectorsize < page size support, we need a structure to record extra
status info for each sector of a page.

Introduce the skeleton structure, all subpage related code would go to
subpage.[ch].
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

When remounting RO, after setting the superblock with the RO flag, the
cleaner task will start sleeping and do nothing, since the call to
btrfs_need_cleaner_sleep() keeps returning 'true'. However, when the
cleaner task goes to sleep, the list of delayed iputs may not be empty.

As long as we are in RO mode, the cleaner task will keep sleeping and
never run the delayed iputs. This means that if a filesystem unmount
is started, we get into close_ctree() with a non-empty list of delayed
iputs, and because the filesystem is in RO mode and is not in an error
state (or a transaction aborted), btrfs_error_commit_super() and
btrfs_commit_super(), which run the delayed iputs, are never called,
and later we fail the assertion that checks if the delayed iputs list
is empty:

  assertion failed: list_empty(&fs_info->delayed_iputs), in fs/btrfs/disk-io.c:4049
  ------------[ cut here ]------------
  kernel BUG at fs/btrfs/ctree.h:3153!
  invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
  CPU: 1 PID: 3780621 Comm: umount Tainted: G             L    5.6.0-rc2-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
  RIP: 0010:assertfail.constprop.0+0x18/0x26 [btrfs]
  Code: 8b 7b 58 48 85 ff 74 (...)
  RSP: 0018:ffffb748c89bbdf8 EFLAGS: 00010246
  RAX: 0000000000000051 RBX: ffff9608f2584000 RCX: 0000000000000000
  RDX: 0000000000000000 RSI: ffffffff91998988 RDI: 00000000ffffffff
  RBP: ffff9608f25870d8 R08: 0000000000000000 R09: 0000000000000001
  R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffc0cbc500
  R13: ffffffff92411750 R14: 0000000000000000 R15: ffff9608f2aab250
  FS:  00007fcbfaa66c80(0000) GS:ffff960936c80000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007fffc2c2dd38 CR3: 0000000235e54002 CR4: 00000000003606e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   close_ctree+0x1a2/0x2e6 [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x93/0xc0
   exit_to_usermode_loop+0xf9/0x100
   do_syscall_64+0x20d/0x260
   entry_SYSCALL_64_after_hwframe+0x49/0xbe
  RIP: 0033:0x7fcbfaca6307
  Code: eb 0b 00 f7 d8 64 89 (...)
  RSP: 002b:00007fffc2c2ed68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 0000558203b559b0 RCX: 00007fcbfaca6307
  RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000558203b55bc0
  RBP: 0000000000000000 R08: 0000000000000001 R09: 00007fffc2c2dad0
  R10: 0000558203b55bf0 R11: 0000000000000246 R12: 0000558203b55bc0
  R13: 00007fcbfadcc204 R14: 0000558203b55aa8 R15: 0000000000000000
  Modules linked in: btrfs dm_flakey dm_log_writes (...)
  ---[ end trace d44d303790049ef6 ]---

So fix this by making the remount RO path run any remaining delayed iputs
after waiting for the cleaner to become inactive.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

When we are remounting a filesystem in RO mode we can race with the cleaner
task and result in leaking a transaction if the filesystem is unmounted
shortly after, before the transaction kthread had a chance to commit that
transaction. That also results in a crash during unmount, due to a
use-after-free, if hardware acceleration is not available for crc32c.

The following sequence of steps explains how the race happens.

1) The filesystem is mounted in RW mode and the cleaner task is running.
   This means that currently BTRFS_FS_CLEANER_RUNNING is set at
   fs_info->flags;

2) The cleaner task is currently running delayed iputs for example;

3) A filesystem RO remount operation starts;

4) The RO remount task calls btrfs_commit_super(), which commits any
   currently open transaction, and it finishes;

5) At this point the cleaner task is still running and it creates a new
   transaction by doing one of the following things:

   * When running the delayed iput() for an inode with a 0 link count,
     in which case at btrfs_evict_inode() we start a transaction through
     the call to evict_refill_and_join(), use it and then release its
     handle through btrfs_end_transaction();

   * When deleting a dead root through btrfs_clean_one_deleted_snapshot(),
     a transaction is started at btrfs_drop_snapshot() and then its handle
     is released through a call to btrfs_end_transaction_throttle();

   * When the remount task was still running, and before the remount task
     called btrfs_delete_unused_bgs(), the cleaner task also called
     btrfs_delete_unused_bgs() and it picked and removed one block group
     from the list of unused block groups. Before the cleaner task started
     a transaction, through btrfs_start_trans_remove_block_group() at
     btrfs_delete_unused_bgs(), the remount task had already called
     btrfs_commit_super();

6) So at this point the filesystem is in RO mode and we have an open
   transaction that was started by the cleaner task;

7) Shortly after a filesystem unmount operation starts. At close_ctree()
   we stop the transaction kthread before it had a chance to commit the
   transaction, since less than 30 seconds (the default commit interval)
   have elapsed since the last transaction was committed;

8) We end up calling iput() against the btree inode at close_ctree() while
   there is an open transaction, and since that transaction was used to
   update btrees by the cleaner, we have dirty pages in the btree inode
   due to COW operations on metadata extents, and therefore writeback is
   triggered for the btree inode.

   So btree_write_cache_pages() is invoked to flush those dirty pages
   during the final iput() on the btree inode. This results in creating a
   bio and submitting it, which makes us end up at
   btrfs_submit_metadata_bio();

9) At btrfs_submit_metadata_bio() we end up at the if-then-else branch
   that calls btrfs_wq_submit_bio(), because check_async_write() returned
   a value of 1. This value of 1 is because we did not have hardware
   acceleration available for crc32c, so BTRFS_FS_CSUM_IMPL_FAST was not
   set in fs_info->flags;

10) Then at btrfs_wq_submit_bio() we call btrfs_queue_work() against the
    workqueue at fs_info->workers, which was already freed before by the
    call to btrfs_stop_all_workers() at close_ctree(). This results in an
    invalid memory access due to a use-after-free, leading to a crash.

When this happens, before the crash there are several warnings triggered,
since we have reserved metadata space in a block group, the delayed refs
reservation, etc:

  ------------[ cut here ]------------
  WARNING: CPU: 4 PID: 1729896 at fs/btrfs/block-group.c:125 btrfs_put_block_group+0x63/0xa0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 4 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_put_block_group+0x63/0xa0 [btrfs]
  Code: f0 01 00 00 48 39 c2 75 (...)
  RSP: 0018:ffffb270826bbdd8 EFLAGS: 00010206
  RAX: 0000000000000001 RBX: ffff947ed73e4000 RCX: ffff947ebc8b29c8
  RDX: 0000000000000001 RSI: ffffffffc0b150a0 RDI: ffff947ebc8b2800
  RBP: ffff947ebc8b2800 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ed73e4110
  R13: ffff947ed73e4160 R14: ffff947ebc8b2988 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481ad600000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f37e2893320 CR3: 0000000138f68001 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_free_block_groups+0x17f/0x2f0 [btrfs]
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 01 48 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c6 ]---
  ------------[ cut here ]------------
  WARNING: CPU: 2 PID: 1729896 at fs/btrfs/block-rsv.c:459 btrfs_release_global_block_rsv+0x70/0xc0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 2 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_release_global_block_rsv+0x70/0xc0 [btrfs]
  Code: 48 83 bb b0 03 00 00 00 (...)
  RSP: 0018:ffffb270826bbdd8 EFLAGS: 00010206
  RAX: 000000000033c000 RBX: ffff947ed73e4000 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffffffffc0b0d8c1 RDI: 00000000ffffffff
  RBP: ffff947ebc8b7000 R08: 0000000000000001 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ed73e4110
  R13: ffff947ed73e5278 R14: dead000000000122 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481aca00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000561a79f76e20 CR3: 0000000138f68006 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_free_block_groups+0x24c/0x2f0 [btrfs]
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 01 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c7 ]---
  ------------[ cut here ]------------
  WARNING: CPU: 2 PID: 1729896 at fs/btrfs/block-group.c:3377 btrfs_free_block_groups+0x25d/0x2f0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 5 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_free_block_groups+0x25d/0x2f0 [btrfs]
  Code: ad de 49 be 22 01 00 (...)
  RSP: 0018:ffffb270826bbde8 EFLAGS: 00010206
  RAX: ffff947ebeae1d08 RBX: ffff947ed73e4000 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffff947e9d823ae8 RDI: 0000000000000246
  RBP: ffff947ebeae1d08 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ebeae1c00
  R13: ffff947ed73e5278 R14: dead000000000122 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481ad200000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f1475d98ea8 CR3: 0000000138f68005 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c8 ]---
  BTRFS info (device sdc): space_info 4 has 268238848 free, is not full
  BTRFS info (device sdc): space_info total=268435456, used=114688, pinned=0, reserved=16384, may_use=0, readonly=65536
  BTRFS info (device sdc): global_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): trans_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): chunk_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): delayed_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): delayed_refs_rsv: size 524288 reserved 0

And the crash, which only happens when we do not have crc32c hardware
acceleration, produces the following trace immediately after those
warnings:

  stack segment: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
  CPU: 2 PID: 1749129 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_queue_work+0x36/0x190 [btrfs]
  Code: 54 55 53 48 89 f3 (...)
  RSP: 0018:ffffb27082443ae8 EFLAGS: 00010282
  RAX: 0000000000000004 RBX: ffff94810ee9ad90 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffff94810ee9ad90 RDI: ffff947ed8ee75a0
  RBP: a56b6b6b6b6b6b6b R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000007 R11: 0000000000000001 R12: ffff947fa9b435a8
  R13: ffff94810ee9ad90 R14: 0000000000000000 R15: ffff947e93dc0000
  FS:  00007f3cfe974840(0000) GS:ffff9481ac600000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f1b42995a70 CR3: 0000000127638003 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_wq_submit_bio+0xb3/0xd0 [btrfs]
   btrfs_submit_metadata_bio+0x44/0xc0 [btrfs]
   submit_one_bio+0x61/0x70 [btrfs]
   btree_write_cache_pages+0x414/0x450 [btrfs]
   ? kobject_put+0x9a/0x1d0
   ? trace_hardirqs_on+0x1b/0xf0
   ? _raw_spin_unlock_irqrestore+0x3c/0x60
   ? free_debug_processing+0x1e1/0x2b0
   do_writepages+0x43/0xe0
   ? lock_acquired+0x199/0x490
   __writeback_single_inode+0x59/0x650
   writeback_single_inode+0xaf/0x120
   write_inode_now+0x94/0xd0
   iput+0x187/0x2b0
   close_ctree+0x2c6/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f3cfebabee7
  Code: ff 0b 00 f7 d8 64 89 01 (...)
  RSP: 002b:00007ffc9c9a05f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f3cfecd1264 RCX: 00007f3cfebabee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 0000562b6b478000
  RBP: 0000562b6b473a30 R08: 0000000000000000 R09: 00007f3cfec6cbe0
  R10: 0000562b6b479fe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 0000562b6b478000 R14: 0000562b6b473b40 R15: 0000562b6b473c60
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  ---[ end trace dd74718fef1ed5cc ]---

Finally when we remove the btrfs module (rmmod btrfs), there are several
warnings about objects that were allocated from our slabs but were never
freed, consequence of the transaction that was never committed and got
leaked:

  =============================================================================
  BUG btrfs_delayed_ref_head (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_ref_head on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------

  INFO: Slab 0x0000000094c2ae56 objects=24 used=2 fp=0x000000002bfa2521 flags=0x17fffc000010200
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? lock_release+0x20e/0x4c0
   kmem_cache_destroy+0x55/0x120
   btrfs_delayed_ref_exit+0x11/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x0000000050cbdd61 @offset=12104
  INFO: Allocated in btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs] age=1894 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs]
        btrfs_free_tree_block+0x128/0x360 [btrfs]
        __btrfs_cow_block+0x489/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
        btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs] age=4292 cpu=2 pid=1729526
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        commit_cowonly_roots+0xfb/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        sync_filesystem+0x74/0x90
        generic_shutdown_super+0x22/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  INFO: Object 0x0000000086e9b0ff @offset=12776
  INFO: Allocated in btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs] age=1900 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs]
        btrfs_alloc_tree_block+0x2bf/0x360 [btrfs]
        alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
        __btrfs_cow_block+0x12d/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
  INFO: Freed in __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs] age=3141 cpu=6 pid=1729803
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        btrfs_write_dirty_block_groups+0x17d/0x3d0 [btrfs]
        commit_cowonly_roots+0x248/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        close_ctree+0x113/0x2fa [btrfs]
        generic_shutdown_super+0x6c/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_ref_head: Slab cache still has objects
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   btrfs_delayed_ref_exit+0x11/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 0b (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  =============================================================================
  BUG btrfs_delayed_tree_ref (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_tree_ref on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------

  INFO: Slab 0x0000000011f78dc0 objects=37 used=2 fp=0x0000000032d55d91 flags=0x17fffc000010200
  CPU: 3 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? lock_release+0x20e/0x4c0
   kmem_cache_destroy+0x55/0x120
   btrfs_delayed_ref_exit+0x1d/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x000000001a340018 @offset=4408
  INFO: Allocated in btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs] age=1917 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs]
        btrfs_free_tree_block+0x128/0x360 [btrfs]
        __btrfs_cow_block+0x489/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
        btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs] age=4167 cpu=4 pid=1729795
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        btrfs_commit_transaction+0x60/0xc40 [btrfs]
        create_subvol+0x56a/0x990 [btrfs]
        btrfs_mksubvol+0x3fb/0x4a0 [btrfs]
        __btrfs_ioctl_snap_create+0x119/0x1a0 [btrfs]
        btrfs_ioctl_snap_create+0x58/0x80 [btrfs]
        btrfs_ioctl+0x1a92/0x36f0 [btrfs]
        __x64_sys_ioctl+0x83/0xb0
        do_syscall_64+0x33/0x80
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  INFO: Object 0x000000002b46292a @offset=13648
  INFO: Allocated in btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs] age=1923 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs]
        btrfs_alloc_tree_block+0x2bf/0x360 [btrfs]
        alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
        __btrfs_cow_block+0x12d/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
  INFO: Freed in __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs] age=3164 cpu=6 pid=1729803
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        commit_cowonly_roots+0xfb/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        close_ctree+0x113/0x2fa [btrfs]
        generic_shutdown_super+0x6c/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_tree_ref: Slab cache still has objects
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   btrfs_delayed_ref_exit+0x1d/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  =============================================================================
  BUG btrfs_delayed_extent_op (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_extent_op on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------
  INFO: Slab 0x00000000f145ce2f objects=22 used=1 fp=0x00000000af0f92cf flags=0x17fffc000010200
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? __mutex_unlock_slowpath+0x45/0x2a0
   kmem_cache_destroy+0x55/0x120
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x000000004cf95ea8 @offset=6264
  INFO: Allocated in btrfs_alloc_tree_block+0x1e0/0x360 [btrfs] age=1931 cpu=6 pid=1729873
        __slab_alloc.isra.0+0x109/0x1c0
        kmem_cache_alloc+0x7bb/0x830
        btrfs_alloc_tree_block+0x1e0/0x360 [btrfs]
        alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
        __btrfs_cow_block+0x12d/0x5f0 [btrfs]
        btrfs_cow_block+0xf7/0x220 [btrfs]
        btrfs_search_slot+0x62a/0xc40 [btrfs]
        btrfs_del_orphan_item+0x65/0xd0 [btrfs]
        btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
        open_ctree+0x125a/0x18a0 [btrfs]
        btrfs_mount_root.cold+0x13/0xed [btrfs]
        legacy_get_tree+0x30/0x60
        vfs_get_tree+0x28/0xe0
        fc_mount+0xe/0x40
        vfs_kern_mount.part.0+0x71/0x90
        btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0xabd/0x1290 [btrfs] age=3173 cpu=6 pid=1729803
        kmem_cache_free+0x34c/0x3c0
        __btrfs_run_delayed_refs+0xabd/0x1290 [btrfs]
        btrfs_run_delayed_refs+0x81/0x210 [btrfs]
        commit_cowonly_roots+0xfb/0x300 [btrfs]
        btrfs_commit_transaction+0x367/0xc40 [btrfs]
        close_ctree+0x113/0x2fa [btrfs]
        generic_shutdown_super+0x6c/0x100
        kill_anon_super+0x14/0x30
        btrfs_kill_super+0x12/0x20 [btrfs]
        deactivate_locked_super+0x31/0x70
        cleanup_mnt+0x100/0x160
        task_work_run+0x68/0xb0
        exit_to_user_mode_prepare+0x1bb/0x1c0
        syscall_exit_to_user_mode+0x4b/0x260
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_extent_op: Slab cache still has objects
  CPU: 3 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  BTRFS: state leak: start 30408704 end 30425087 state 1 in tree 1 refs 1

So fix this by making the remount path to wait for the cleaner task before
calling btrfs_commit_super(). The remount path now waits for the bit
BTRFS_FS_CLEANER_RUNNING to be cleared from fs_info->flags before calling
btrfs_commit_super() and this ensures the cleaner can not start a
transaction after that, because it sleeps when the filesystem is in RO
mode and we have already flagged the filesystem as RO before waiting for
BTRFS_FS_CLEANER_RUNNING to be cleared.

This also introduces a new flag BTRFS_FS_STATE_RO to be used for
fs_info->fs_state when the filesystem is in RO mode. This is because we
were doing the RO check using the flags of the superblock and setting the
RO mode simply by ORing into the superblock's flags - those operations are
not atomic and could result in the cleaner not seeing the update from the
remount task after it clears BTRFS_FS_CLEANER_RUNNING.
Tested-by: NFabian Vogt <fvogt@suse.com>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

If we remount a filesystem in RO mode while the qgroup rescan worker is
running, we can end up having it still running after the remount is done,
and at unmount time we may end up with an open transaction that ends up
never getting committed. If that happens we end up with several memory
leaks and can crash when hardware acceleration is unavailable for crc32c.
Possibly it can lead to other nasty surprises too, due to use-after-free
issues.

The following steps explain how the problem happens.

1) We have a filesystem mounted in RW mode and the qgroup rescan worker is
   running;

2) We remount the filesystem in RO mode, and never stop/pause the rescan
   worker, so after the remount the rescan worker is still running. The
   important detail here is that the rescan task is still running after
   the remount operation committed any ongoing transaction through its
   call to btrfs_commit_super();

3) The rescan is still running, and after the remount completed, the
   rescan worker started a transaction, after it finished iterating all
   leaves of the extent tree, to update the qgroup status item in the
   quotas tree. It does not commit the transaction, it only releases its
   handle on the transaction;

4) A filesystem unmount operation starts shortly after;

5) The unmount task, at close_ctree(), stops the transaction kthread,
   which had not had a chance to commit the open transaction since it was
   sleeping and the commit interval (default of 30 seconds) has not yet
   elapsed since the last time it committed a transaction;

6) So after stopping the transaction kthread we still have the transaction
   used to update the qgroup status item open. At close_ctree(), when the
   filesystem is in RO mode and no transaction abort happened (or the
   filesystem is in error mode), we do not expect to have any transaction
   open, so we do not call btrfs_commit_super();

7) We then proceed to destroy the work queues, free the roots and block
   groups, etc. After that we drop the last reference on the btree inode
   by calling iput() on it. Since there are dirty pages for the btree
   inode, corresponding to the COWed extent buffer for the quotas btree,
   btree_write_cache_pages() is invoked to flush those dirty pages. This
   results in creating a bio and submitting it, which makes us end up at
   btrfs_submit_metadata_bio();

8) At btrfs_submit_metadata_bio() we end up at the if-then-else branch
   that calls btrfs_wq_submit_bio(), because check_async_write() returned
   a value of 1. This value of 1 is because we did not have hardware
   acceleration available for crc32c, so BTRFS_FS_CSUM_IMPL_FAST was not
   set in fs_info->flags;

9) Then at btrfs_wq_submit_bio() we call btrfs_queue_work() against the
   workqueue at fs_info->workers, which was already freed before by the
   call to btrfs_stop_all_workers() at close_ctree(). This results in an
   invalid memory access due to a use-after-free, leading to a crash.

When this happens, before the crash there are several warnings triggered,
since we have reserved metadata space in a block group, the delayed refs
reservation, etc:

  ------------[ cut here ]------------
  WARNING: CPU: 4 PID: 1729896 at fs/btrfs/block-group.c:125 btrfs_put_block_group+0x63/0xa0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 4 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_put_block_group+0x63/0xa0 [btrfs]
  Code: f0 01 00 00 48 39 c2 75 (...)
  RSP: 0018:ffffb270826bbdd8 EFLAGS: 00010206
  RAX: 0000000000000001 RBX: ffff947ed73e4000 RCX: ffff947ebc8b29c8
  RDX: 0000000000000001 RSI: ffffffffc0b150a0 RDI: ffff947ebc8b2800
  RBP: ffff947ebc8b2800 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ed73e4110
  R13: ffff947ed73e4160 R14: ffff947ebc8b2988 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481ad600000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f37e2893320 CR3: 0000000138f68001 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_free_block_groups+0x17f/0x2f0 [btrfs]
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 01 48 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c6 ]---
  ------------[ cut here ]------------
  WARNING: CPU: 2 PID: 1729896 at fs/btrfs/block-rsv.c:459 btrfs_release_global_block_rsv+0x70/0xc0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 2 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_release_global_block_rsv+0x70/0xc0 [btrfs]
  Code: 48 83 bb b0 03 00 00 00 (...)
  RSP: 0018:ffffb270826bbdd8 EFLAGS: 00010206
  RAX: 000000000033c000 RBX: ffff947ed73e4000 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffffffffc0b0d8c1 RDI: 00000000ffffffff
  RBP: ffff947ebc8b7000 R08: 0000000000000001 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ed73e4110
  R13: ffff947ed73e5278 R14: dead000000000122 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481aca00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000561a79f76e20 CR3: 0000000138f68006 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_free_block_groups+0x24c/0x2f0 [btrfs]
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 01 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c7 ]---
  ------------[ cut here ]------------
  WARNING: CPU: 2 PID: 1729896 at fs/btrfs/block-group.c:3377 btrfs_free_block_groups+0x25d/0x2f0 [btrfs]
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  CPU: 5 PID: 1729896 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_free_block_groups+0x25d/0x2f0 [btrfs]
  Code: ad de 49 be 22 01 00 (...)
  RSP: 0018:ffffb270826bbde8 EFLAGS: 00010206
  RAX: ffff947ebeae1d08 RBX: ffff947ed73e4000 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffff947e9d823ae8 RDI: 0000000000000246
  RBP: ffff947ebeae1d08 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: ffff947ebeae1c00
  R13: ffff947ed73e5278 R14: dead000000000122 R15: dead000000000100
  FS:  00007f15edfea840(0000) GS:ffff9481ad200000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f1475d98ea8 CR3: 0000000138f68005 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   close_ctree+0x2ba/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f15ee221ee7
  Code: ff 0b 00 f7 d8 64 89 (...)
  RSP: 002b:00007ffe9470f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f15ee347264 RCX: 00007f15ee221ee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 000056169701d000
  RBP: 0000561697018a30 R08: 0000000000000000 R09: 00007f15ee2e2be0
  R10: 000056169701efe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 000056169701d000 R14: 0000561697018b40 R15: 0000561697018c60
  irq event stamp: 0
  hardirqs last  enabled at (0): [<0000000000000000>] 0x0
  hardirqs last disabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last  enabled at (0): [<ffffffff8bcae560>] copy_process+0x8a0/0x1d70
  softirqs last disabled at (0): [<0000000000000000>] 0x0
  ---[ end trace dd74718fef1ed5c8 ]---
  BTRFS info (device sdc): space_info 4 has 268238848 free, is not full
  BTRFS info (device sdc): space_info total=268435456, used=114688, pinned=0, reserved=16384, may_use=0, readonly=65536
  BTRFS info (device sdc): global_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): trans_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): chunk_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): delayed_block_rsv: size 0 reserved 0
  BTRFS info (device sdc): delayed_refs_rsv: size 524288 reserved 0

And the crash, which only happens when we do not have crc32c hardware
acceleration, produces the following trace immediately after those
warnings:

  stack segment: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
  CPU: 2 PID: 1749129 Comm: umount Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  RIP: 0010:btrfs_queue_work+0x36/0x190 [btrfs]
  Code: 54 55 53 48 89 f3 (...)
  RSP: 0018:ffffb27082443ae8 EFLAGS: 00010282
  RAX: 0000000000000004 RBX: ffff94810ee9ad90 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: ffff94810ee9ad90 RDI: ffff947ed8ee75a0
  RBP: a56b6b6b6b6b6b6b R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000007 R11: 0000000000000001 R12: ffff947fa9b435a8
  R13: ffff94810ee9ad90 R14: 0000000000000000 R15: ffff947e93dc0000
  FS:  00007f3cfe974840(0000) GS:ffff9481ac600000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f1b42995a70 CR3: 0000000127638003 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   btrfs_wq_submit_bio+0xb3/0xd0 [btrfs]
   btrfs_submit_metadata_bio+0x44/0xc0 [btrfs]
   submit_one_bio+0x61/0x70 [btrfs]
   btree_write_cache_pages+0x414/0x450 [btrfs]
   ? kobject_put+0x9a/0x1d0
   ? trace_hardirqs_on+0x1b/0xf0
   ? _raw_spin_unlock_irqrestore+0x3c/0x60
   ? free_debug_processing+0x1e1/0x2b0
   do_writepages+0x43/0xe0
   ? lock_acquired+0x199/0x490
   __writeback_single_inode+0x59/0x650
   writeback_single_inode+0xaf/0x120
   write_inode_now+0x94/0xd0
   iput+0x187/0x2b0
   close_ctree+0x2c6/0x2fa [btrfs]
   generic_shutdown_super+0x6c/0x100
   kill_anon_super+0x14/0x30
   btrfs_kill_super+0x12/0x20 [btrfs]
   deactivate_locked_super+0x31/0x70
   cleanup_mnt+0x100/0x160
   task_work_run+0x68/0xb0
   exit_to_user_mode_prepare+0x1bb/0x1c0
   syscall_exit_to_user_mode+0x4b/0x260
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f3cfebabee7
  Code: ff 0b 00 f7 d8 64 89 01 (...)
  RSP: 002b:00007ffc9c9a05f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
  RAX: 0000000000000000 RBX: 00007f3cfecd1264 RCX: 00007f3cfebabee7
  RDX: ffffffffffffff78 RSI: 0000000000000000 RDI: 0000562b6b478000
  RBP: 0000562b6b473a30 R08: 0000000000000000 R09: 00007f3cfec6cbe0
  R10: 0000562b6b479fe0 R11: 0000000000000246 R12: 0000000000000000
  R13: 0000562b6b478000 R14: 0000562b6b473b40 R15: 0000562b6b473c60
  Modules linked in: btrfs dm_snapshot dm_thin_pool (...)
  ---[ end trace dd74718fef1ed5cc ]---

Finally when we remove the btrfs module (rmmod btrfs), there are several
warnings about objects that were allocated from our slabs but were never
freed, consequence of the transaction that was never committed and got
leaked:

  =============================================================================
  BUG btrfs_delayed_ref_head (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_ref_head on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------

  INFO: Slab 0x0000000094c2ae56 objects=24 used=2 fp=0x000000002bfa2521 flags=0x17fffc000010200
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? lock_release+0x20e/0x4c0
   kmem_cache_destroy+0x55/0x120
   btrfs_delayed_ref_exit+0x11/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x0000000050cbdd61 @offset=12104
  INFO: Allocated in btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs] age=1894 cpu=6 pid=1729873
	__slab_alloc.isra.0+0x109/0x1c0
	kmem_cache_alloc+0x7bb/0x830
	btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs]
	btrfs_free_tree_block+0x128/0x360 [btrfs]
	__btrfs_cow_block+0x489/0x5f0 [btrfs]
	btrfs_cow_block+0xf7/0x220 [btrfs]
	btrfs_search_slot+0x62a/0xc40 [btrfs]
	btrfs_del_orphan_item+0x65/0xd0 [btrfs]
	btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
	open_ctree+0x125a/0x18a0 [btrfs]
	btrfs_mount_root.cold+0x13/0xed [btrfs]
	legacy_get_tree+0x30/0x60
	vfs_get_tree+0x28/0xe0
	fc_mount+0xe/0x40
	vfs_kern_mount.part.0+0x71/0x90
	btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs] age=4292 cpu=2 pid=1729526
	kmem_cache_free+0x34c/0x3c0
	__btrfs_run_delayed_refs+0x1117/0x1290 [btrfs]
	btrfs_run_delayed_refs+0x81/0x210 [btrfs]
	commit_cowonly_roots+0xfb/0x300 [btrfs]
	btrfs_commit_transaction+0x367/0xc40 [btrfs]
	sync_filesystem+0x74/0x90
	generic_shutdown_super+0x22/0x100
	kill_anon_super+0x14/0x30
	btrfs_kill_super+0x12/0x20 [btrfs]
	deactivate_locked_super+0x31/0x70
	cleanup_mnt+0x100/0x160
	task_work_run+0x68/0xb0
	exit_to_user_mode_prepare+0x1bb/0x1c0
	syscall_exit_to_user_mode+0x4b/0x260
	entry_SYSCALL_64_after_hwframe+0x44/0xa9
  INFO: Object 0x0000000086e9b0ff @offset=12776
  INFO: Allocated in btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs] age=1900 cpu=6 pid=1729873
	__slab_alloc.isra.0+0x109/0x1c0
	kmem_cache_alloc+0x7bb/0x830
	btrfs_add_delayed_tree_ref+0xbb/0x480 [btrfs]
	btrfs_alloc_tree_block+0x2bf/0x360 [btrfs]
	alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
	__btrfs_cow_block+0x12d/0x5f0 [btrfs]
	btrfs_cow_block+0xf7/0x220 [btrfs]
	btrfs_search_slot+0x62a/0xc40 [btrfs]
	btrfs_del_orphan_item+0x65/0xd0 [btrfs]
	btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
	open_ctree+0x125a/0x18a0 [btrfs]
	btrfs_mount_root.cold+0x13/0xed [btrfs]
	legacy_get_tree+0x30/0x60
	vfs_get_tree+0x28/0xe0
	fc_mount+0xe/0x40
	vfs_kern_mount.part.0+0x71/0x90
  INFO: Freed in __btrfs_run_delayed_refs+0x1117/0x1290 [btrfs] age=3141 cpu=6 pid=1729803
	kmem_cache_free+0x34c/0x3c0
	__btrfs_run_delayed_refs+0x1117/0x1290 [btrfs]
	btrfs_run_delayed_refs+0x81/0x210 [btrfs]
	btrfs_write_dirty_block_groups+0x17d/0x3d0 [btrfs]
	commit_cowonly_roots+0x248/0x300 [btrfs]
	btrfs_commit_transaction+0x367/0xc40 [btrfs]
	close_ctree+0x113/0x2fa [btrfs]
	generic_shutdown_super+0x6c/0x100
	kill_anon_super+0x14/0x30
	btrfs_kill_super+0x12/0x20 [btrfs]
	deactivate_locked_super+0x31/0x70
	cleanup_mnt+0x100/0x160
	task_work_run+0x68/0xb0
	exit_to_user_mode_prepare+0x1bb/0x1c0
	syscall_exit_to_user_mode+0x4b/0x260
	entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_ref_head: Slab cache still has objects
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   btrfs_delayed_ref_exit+0x11/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 0b (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  =============================================================================
  BUG btrfs_delayed_tree_ref (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_tree_ref on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------

  INFO: Slab 0x0000000011f78dc0 objects=37 used=2 fp=0x0000000032d55d91 flags=0x17fffc000010200
  CPU: 3 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? lock_release+0x20e/0x4c0
   kmem_cache_destroy+0x55/0x120
   btrfs_delayed_ref_exit+0x1d/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x000000001a340018 @offset=4408
  INFO: Allocated in btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs] age=1917 cpu=6 pid=1729873
	__slab_alloc.isra.0+0x109/0x1c0
	kmem_cache_alloc+0x7bb/0x830
	btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs]
	btrfs_free_tree_block+0x128/0x360 [btrfs]
	__btrfs_cow_block+0x489/0x5f0 [btrfs]
	btrfs_cow_block+0xf7/0x220 [btrfs]
	btrfs_search_slot+0x62a/0xc40 [btrfs]
	btrfs_del_orphan_item+0x65/0xd0 [btrfs]
	btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
	open_ctree+0x125a/0x18a0 [btrfs]
	btrfs_mount_root.cold+0x13/0xed [btrfs]
	legacy_get_tree+0x30/0x60
	vfs_get_tree+0x28/0xe0
	fc_mount+0xe/0x40
	vfs_kern_mount.part.0+0x71/0x90
	btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs] age=4167 cpu=4 pid=1729795
	kmem_cache_free+0x34c/0x3c0
	__btrfs_run_delayed_refs+0x63d/0x1290 [btrfs]
	btrfs_run_delayed_refs+0x81/0x210 [btrfs]
	btrfs_commit_transaction+0x60/0xc40 [btrfs]
	create_subvol+0x56a/0x990 [btrfs]
	btrfs_mksubvol+0x3fb/0x4a0 [btrfs]
	__btrfs_ioctl_snap_create+0x119/0x1a0 [btrfs]
	btrfs_ioctl_snap_create+0x58/0x80 [btrfs]
	btrfs_ioctl+0x1a92/0x36f0 [btrfs]
	__x64_sys_ioctl+0x83/0xb0
	do_syscall_64+0x33/0x80
	entry_SYSCALL_64_after_hwframe+0x44/0xa9
  INFO: Object 0x000000002b46292a @offset=13648
  INFO: Allocated in btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs] age=1923 cpu=6 pid=1729873
	__slab_alloc.isra.0+0x109/0x1c0
	kmem_cache_alloc+0x7bb/0x830
	btrfs_add_delayed_tree_ref+0x9e/0x480 [btrfs]
	btrfs_alloc_tree_block+0x2bf/0x360 [btrfs]
	alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
	__btrfs_cow_block+0x12d/0x5f0 [btrfs]
	btrfs_cow_block+0xf7/0x220 [btrfs]
	btrfs_search_slot+0x62a/0xc40 [btrfs]
	btrfs_del_orphan_item+0x65/0xd0 [btrfs]
	btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
	open_ctree+0x125a/0x18a0 [btrfs]
	btrfs_mount_root.cold+0x13/0xed [btrfs]
	legacy_get_tree+0x30/0x60
	vfs_get_tree+0x28/0xe0
	fc_mount+0xe/0x40
	vfs_kern_mount.part.0+0x71/0x90
  INFO: Freed in __btrfs_run_delayed_refs+0x63d/0x1290 [btrfs] age=3164 cpu=6 pid=1729803
	kmem_cache_free+0x34c/0x3c0
	__btrfs_run_delayed_refs+0x63d/0x1290 [btrfs]
	btrfs_run_delayed_refs+0x81/0x210 [btrfs]
	commit_cowonly_roots+0xfb/0x300 [btrfs]
	btrfs_commit_transaction+0x367/0xc40 [btrfs]
	close_ctree+0x113/0x2fa [btrfs]
	generic_shutdown_super+0x6c/0x100
	kill_anon_super+0x14/0x30
	btrfs_kill_super+0x12/0x20 [btrfs]
	deactivate_locked_super+0x31/0x70
	cleanup_mnt+0x100/0x160
	task_work_run+0x68/0xb0
	exit_to_user_mode_prepare+0x1bb/0x1c0
	syscall_exit_to_user_mode+0x4b/0x260
	entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_tree_ref: Slab cache still has objects
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   btrfs_delayed_ref_exit+0x1d/0x35 [btrfs]
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  =============================================================================
  BUG btrfs_delayed_extent_op (Tainted: G    B   W        ): Objects remaining in btrfs_delayed_extent_op on __kmem_cache_shutdown()
  -----------------------------------------------------------------------------

  INFO: Slab 0x00000000f145ce2f objects=22 used=1 fp=0x00000000af0f92cf flags=0x17fffc000010200
  CPU: 5 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   slab_err+0xb7/0xdc
   ? lock_acquired+0x199/0x490
   __kmem_cache_shutdown+0x1ac/0x3c0
   ? __mutex_unlock_slowpath+0x45/0x2a0
   kmem_cache_destroy+0x55/0x120
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 f5 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  INFO: Object 0x000000004cf95ea8 @offset=6264
  INFO: Allocated in btrfs_alloc_tree_block+0x1e0/0x360 [btrfs] age=1931 cpu=6 pid=1729873
	__slab_alloc.isra.0+0x109/0x1c0
	kmem_cache_alloc+0x7bb/0x830
	btrfs_alloc_tree_block+0x1e0/0x360 [btrfs]
	alloc_tree_block_no_bg_flush+0x4f/0x60 [btrfs]
	__btrfs_cow_block+0x12d/0x5f0 [btrfs]
	btrfs_cow_block+0xf7/0x220 [btrfs]
	btrfs_search_slot+0x62a/0xc40 [btrfs]
	btrfs_del_orphan_item+0x65/0xd0 [btrfs]
	btrfs_find_orphan_roots+0x1bf/0x200 [btrfs]
	open_ctree+0x125a/0x18a0 [btrfs]
	btrfs_mount_root.cold+0x13/0xed [btrfs]
	legacy_get_tree+0x30/0x60
	vfs_get_tree+0x28/0xe0
	fc_mount+0xe/0x40
	vfs_kern_mount.part.0+0x71/0x90
	btrfs_mount+0x13b/0x3e0 [btrfs]
  INFO: Freed in __btrfs_run_delayed_refs+0xabd/0x1290 [btrfs] age=3173 cpu=6 pid=1729803
	kmem_cache_free+0x34c/0x3c0
	__btrfs_run_delayed_refs+0xabd/0x1290 [btrfs]
	btrfs_run_delayed_refs+0x81/0x210 [btrfs]
	commit_cowonly_roots+0xfb/0x300 [btrfs]
	btrfs_commit_transaction+0x367/0xc40 [btrfs]
	close_ctree+0x113/0x2fa [btrfs]
	generic_shutdown_super+0x6c/0x100
	kill_anon_super+0x14/0x30
	btrfs_kill_super+0x12/0x20 [btrfs]
	deactivate_locked_super+0x31/0x70
	cleanup_mnt+0x100/0x160
	task_work_run+0x68/0xb0
	exit_to_user_mode_prepare+0x1bb/0x1c0
	syscall_exit_to_user_mode+0x4b/0x260
	entry_SYSCALL_64_after_hwframe+0x44/0xa9
  kmem_cache_destroy btrfs_delayed_extent_op: Slab cache still has objects
  CPU: 3 PID: 1729921 Comm: rmmod Tainted: G    B   W         5.10.0-rc4-btrfs-next-73 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  Call Trace:
   dump_stack+0x8d/0xb5
   kmem_cache_destroy+0x119/0x120
   exit_btrfs_fs+0xa/0x59 [btrfs]
   __x64_sys_delete_module+0x194/0x260
   ? fpregs_assert_state_consistent+0x1e/0x40
   ? exit_to_user_mode_prepare+0x55/0x1c0
   ? trace_hardirqs_on+0x1b/0xf0
   do_syscall_64+0x33/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f693e305897
  Code: 73 01 c3 48 8b 0d f9 (...)
  RSP: 002b:00007ffcf73eb508 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
  RAX: ffffffffffffffda RBX: 0000559df504f760 RCX: 00007f693e305897
  RDX: 000000000000000a RSI: 0000000000000800 RDI: 0000559df504f7c8
  RBP: 00007ffcf73eb568 R08: 0000000000000000 R09: 0000000000000000
  R10: 00007f693e378ac0 R11: 0000000000000206 R12: 00007ffcf73eb740
  R13: 00007ffcf73ec5a6 R14: 0000559df504f2a0 R15: 0000559df504f760
  BTRFS: state leak: start 30408704 end 30425087 state 1 in tree 1 refs 1

Fix this issue by having the remount path stop the qgroup rescan worker
when we are remounting RO and teach the rescan worker to stop when a
remount is in progress. If later a remount in RW mode happens, we are
already resuming the qgroup rescan worker through the call to
btrfs_qgroup_rescan_resume(), so we do not need to worry about that.
Tested-by: NFabian Vogt <fvogt@suse.com>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

If the remount is ro->ro, rw->ro, or rw->rw, we will not create or
clear the free space tree. This can be surprising, so print a warning
to dmesg to make the failure more visible. It is also important to
ensure that the space cache options (SPACE_CACHE, FREE_SPACE_TREE) are
consistent, so ensure those are set to properly match the current on
disk state (which won't be changing).
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NBoris Burkov <boris@bur.io>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

To make the contents of /proc/mounts better match the actual state of
the filesystem, base the display of the space cache mount options off
the contents of the super block rather than the last mount options
passed in. Since there are many scenarios where the mount will ignore a
space cache option, simply showing the passed in option is misleading.

For example, if we mount with -o remount,space_cache=v2 on a read-write
file system without an existing free space tree, we won't build a free
space tree, but /proc/mounts will read space_cache=v2 (until we mount
again and it goes away)

cache_generation is set iff space_cache=v1, FREE_SPACE_TREE is set iff
space_cache=v2, and if neither is the case, we print nospace_cache.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NBoris Burkov <boris@bur.io>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

When mounting, btrfs uses the cache_generation in the super block to
determine if space cache v1 is in use. However, by mounting with
nospace_cache or space_cache=v2, it is possible to disable space cache
v1, which does not result in un-setting cache_generation back to 0.

In order to base some logic, like mount option printing in /proc/mounts,
on the current state of the space cache rather than just the values of
the mount option, keep the value of cache_generation consistent with the
status of space cache v1.

We ensure that cache_generation > 0 iff the file system is using
space_cache v1. This requires committing a transaction on any mount
which changes whether we are using v1. (v1->nospace_cache, v1->v2,
nospace_cache->v1, v2->v1).

Since the mechanism for writing out the cache generation is transaction
commit, but we want some finer grained control over when we un-set it,
we can't just rely on the SPACE_CACHE mount option, and introduce an
fs_info flag that mount can use when it wants to unset the generation.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NBoris Burkov <boris@bur.io>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Some options only apply during mount time and are cleared at the end
of mount. For now, the example is USEBACKUPROOT, but CLEAR_CACHE also
fits the bill, and this is a preparation patch for also clearing that
option.

One subtlety is that the current code only resets USEBACKUPROOT on rw
mounts, but the option is meaningfully "consumed" by a ro mount, so it
feels appropriate to clear in that case as well. A subsequent read-write
remount would not go through open_ctree, which is the only place that
checks the option, so the change should be benign.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NBoris Burkov <boris@bur.io>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Mounting rw and remounting from ro to rw naturally share invariants and
functionality which result in a correctly setup rw filesystem. Luckily,
there is even a strong unity in the code which implements them. In
mount's open_ctree, these operations mostly happen after an early return
for ro file systems, and in remount, they happen in a section devoted to
remounting ro->rw, after some remount specific validation passes.

However, there are unfortunately a few differences. There are small
deviations in the order of some of the operations, remount does not
start orphan cleanup in root_tree or fs_tree, remount does not create
the free space tree, and remount does not handle "one-shot" mount
options like clear_cache and uuid tree rescan.

Since we want to add building the free space tree to remount, and also
to start the same orphan cleanup process on a filesystem mounted as ro
then remounted rw, we would benefit from unifying the logic between the
two code paths.

This patch only lifts the existing common functionality, and leaves a
natural path for fixing the discrepancies.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NBoris Burkov <boris@bur.io>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

It's been deprecated since commit b547a88e ("btrfs: start
deprecation of mount option inode_cache") which enumerates the reasons.

A filesystem that uses the feature (mount -o inode_cache) tracks the
inode numbers in bitmaps, that data stay on the filesystem after this
patch. The size is roughly 5MiB for 1M inodes [1], which is considered
small enough to be left there. Removal of the change can be implemented
in btrfs-progs if needed.

[1] https://lore.kernel.org/linux-btrfs/20201127145836.GZ6430@twin.jikos.cz/Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: NDavid Sterba <dsterba@suse.com>

As updates to the space cache v1 are in-place, the space cache cannot be
located over sequential zones and there is no guarantees that the device
will have enough conventional zones to store this cache. Resolve this
problem by disabling completely the space cache v1.  This does not
introduce any problems with sequential block groups: all the free space
is located after the allocation pointer and no free space before the
pointer.  There is no need to have such cache.

Note: we can technically use free-space-tree (space cache v2) on ZONED
mode. But, since ZONED mode now always allocates extents in a block
group sequentially regardless of underlying device zone type, it's no
use to enable and maintain the tree.

For the same reason, NODATACOW is also disabled.

In summary, ZONED will disable:

| Disabled features | Reason                                              |
|-------------------+-----------------------------------------------------|
| RAID/DUP          | Cannot handle two zone append writes to different   |
|                   | zones                                               |
|-------------------+-----------------------------------------------------|
| space_cache (v1)  | In-place updating                                   |
| NODATACOW         | In-place updating                                   |
|-------------------+-----------------------------------------------------|
| fallocate         | Reserved extent will be a write hole                |
|-------------------+-----------------------------------------------------|
| MIXED_BG          | Allocated metadata region will be write holes for   |
|                   | data writes                                         |
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NNaohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Introduce function btrfs_check_zoned_mode() to check if ZONED flag is
enabled on the file system and if the file system consists of zoned
devices with equal zone size.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: NNaohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

If a zoned block device is found, get its zone information (number of
zones and zone size).  To avoid costly run-time zone report
commands to test the device zones type during block allocation, attach
the seq_zones bitmap to the device structure to indicate if a zone is
sequential or accept random writes. Also it attaches the empty_zones
bitmap to indicate if a zone is empty or not.

This patch also introduces the helper function btrfs_dev_is_sequential()
to test if the zone storing a block is a sequential write required zone
and btrfs_dev_is_empty_zone() to test if the zone is a empty zone.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: NNaohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Without a NULL fs_info the helpers will print something like

	BTRFS error (device <unknown>): ...

This can happen in contexts where fs_info is not available at all or
it's potentially unsafe due to object lifetime. The <unknown> stub does
not bring much information and with the prefix makes the message
unnecessarily longer.

Remove it for the NULL fs_info case.

	BTRFS error: ...

Callers can add the device information to the message itself if needed.
Reviewed-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

We no longer distinguish between blocking and spinning, so rip out all
this code.
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The value of super_block::s_blocksize_bits is the same as
fs_info::sectorsize_bits, but we don't need to do the extra dereferences
in many functions and storing the bits as u32 (in fs_info) generates
shorter assembly.
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: NQu Wenruo <wqu@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The names in btrfs_lockdep_keysets are generated from a simple pattern
using snprintf but we can generate them directly with some macro magic
and remove the helpers.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Now that we have the building blocks for some better recovery options
with corrupted file systems, add a rescue=all option to enable all of
the relevant rescue options.  This will allow distros to simply default
to rescue=all for the "oh dear lord the world's on fire" recovery
without needing to know all the different options that we have and may
add in the future.
Reviewed-by: NQu Wenruo <wqu@suse.com>
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

There are cases where you can end up with bad data csums because of
misbehaving applications.  This happens when an application modifies a
buffer in-flight when doing an O_DIRECT write.  In order to recover the
file we need a way to turn off data checksums so you can copy the file
off, and then you can delete the file and restore it properly later.
Reviewed-by: NQu Wenruo <wqu@suse.com>
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

In the face of extent root corruption, or any other core fs wide root
corruption we will fail to mount the file system.  This makes recovery
kind of a pain, because you need to fall back to userspace tools to
scrape off data.  Instead provide a mechanism to gracefully handle bad
roots, so we can at least mount read-only and possibly recover data from
the file system.
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The standalone option usebackuproot was intended as one-time use and it
was not necessary to keep it in the option list. Now that we're going to
have more rescue options, it's desirable to keep them intact as it could
be confusing why the option disappears.
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
[ remove the btrfs_clear_opt part from open_ctree ]
Signed-off-by: NDavid Sterba <dsterba@suse.com>

We're going to have a lot of rescue options, add a helper to collapse
the /proc/mounts output to rescue=option1:option2:option3 format.
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

We're going to be adding more options that require RDONLY, so add a
helper to do the check and error out if we don't have RDONLY set.
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: NQu Wenruo <wqu@suse.com>
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

We have this thing wrapped in an RCU lock, but it's really not needed.
We create all the space_info's on mount, and we destroy them on unmount.
The list never changes and we're protected from messing with it by the
normal mount/umount path, so kill the RCU stuff around it.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Now that we have the data ticketing stuff in place, move normal data
reservations to use an async reclaim helper to satisfy tickets.  Before
we could have multiple tasks race in and both allocate chunks, resulting
in more data chunks than we would necessarily need.  Serializing these
allocations and making a single thread responsible for flushing will
only allocate chunks as needed, as well as cut down on transaction
commits and other flush related activities.

Priority reservations will still work as they have before, simply
trying to allocate a chunk until they can make their reservation.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Tested-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Currently a user can set mount "-o compress" which will set the
compression algorithm to zlib, and use the default compress level for
zlib (3):

  relatime,compress=zlib:3,space_cache

If the user remounts the fs using "-o compress=lzo", then the old
compress_level is used:

  relatime,compress=lzo:3,space_cache

But lzo does not expose any tunable compression level. The same happens
if we set any compress argument with different level, also with zstd.

Fix this by resetting the compress_level when compress=lzo is
specified.  With the fix applied, lzo is shown without compress level:

  relatime,compress=lzo,space_cache

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: NMarcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

There's some inconsistency around SB_I_VERSION handling with mount and
remount.  Since we don't really want it to be off ever just work around
this by making sure we don't get the flag cleared on remount.

There's a tiny cpu cost of setting the bit, otherwise all changes to
i_version also change some of the times (ctime/mtime) so the inode needs
to be synced. We wouldn't save anything by disabling it.
Reported-by: NEric Sandeen <sandeen@redhat.com>
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
[ add perf impact analysis ]
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Chris Murphy reported a problem where rpm ostree will bind mount a bunch
of things for whatever voodoo it's doing.  But when it does this
/proc/mounts shows something like

  /dev/sda /mnt/test btrfs rw,relatime,subvolid=256,subvol=/foo 0 0
  /dev/sda /mnt/test/baz btrfs rw,relatime,subvolid=256,subvol=/foo/bar 0 0

Despite subvolid=256 being subvol=/foo.  This is because we're just
spitting out the dentry of the mount point, which in the case of bind
mounts is the source path for the mountpoint.  Instead we should spit
out the path to the actual subvol.  Fix this by looking up the name for
the subvolid we have mounted.  With this fix the same test looks like
this

  /dev/sda /mnt/test btrfs rw,relatime,subvolid=256,subvol=/foo 0 0
  /dev/sda /mnt/test/baz btrfs rw,relatime,subvolid=256,subvol=/foo 0 0
Reported-by: NChris Murphy <chris@colorremedies.com>
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Reported by Forza on IRC that remounting with compression options does
not reflect the change in level, or at least it does not appear to do so
according to the messages:

  mount -o compress=zstd:1 /dev/sda /mnt
  mount -o remount,compress=zstd:15 /mnt

does not print the change to the level to syslog:

  [   41.366060] BTRFS info (device vda): use zstd compression, level 1
  [   41.368254] BTRFS info (device vda): disk space caching is enabled
  [   41.390429] BTRFS info (device vda): disk space caching is enabled

What really happens is that the message is lost but the level is actualy
changed.

There's another weird output, if compression is reset to 'no':

  [   45.413776] BTRFS info (device vda): use no compression, level 4

To fix that, save the previous compression level and print the message
in that case too and use separate message for 'no' compression.

CC: stable@vger.kernel.org # 4.19+
Signed-off-by: NDavid Sterba <dsterba@suse.com>

When we're (re)mounting a btrfs filesystem we set the
BTRFS_FS_STATE_REMOUNTING state in fs_info to serialize against async
reclaim or defrags.

This flag is set in btrfs_remount_prepare() called by btrfs_remount().
As btrfs_remount_prepare() does nothing but setting this flag and
doesn't have a second caller, we can just open-code the flag setting in
btrfs_remount().

Similarly do for so clearing of the flag by moving it out of
btrfs_remount_cleanup() into btrfs_remount() to be symmetrical.
Signed-off-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

We've had some discussions about what to do in certain scenarios for
error codes, specifically EUCLEAN and EROFS.  Document these near the
error handling code so its clear what their intentions are.
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

->show_devname currently shows the lowest devid in the list. As the seed
devices have the lowest devid in the sprouted filesystem, the userland
tool such as findmnt end up seeing seed device instead of the device from
the read-writable sprouted filesystem. As shown below.

 mount /dev/sda /btrfs
 mount: /btrfs: WARNING: device write-protected, mounted read-only.

 findmnt --output SOURCE,TARGET,UUID /btrfs
 SOURCE   TARGET UUID
 /dev/sda /btrfs 899f7027-3e46-4626-93e7-7d4c9ad19111

 btrfs dev add -f /dev/sdb /btrfs

 umount /btrfs
 mount /dev/sdb /btrfs

 findmnt --output SOURCE,TARGET,UUID /btrfs
 SOURCE   TARGET UUID
 /dev/sda /btrfs 899f7027-3e46-4626-93e7-7d4c9ad19111

All sprouts from a single seed will show the same seed device and the
same fsid. That's confusing.
This is causing problems in our prototype as there isn't any reference
to the sprout file-system(s) which is being used for actual read and
write.

This was added in the patch which implemented the show_devname in btrfs
commit 9c5085c1 ("Btrfs: implement ->show_devname").
I tried to look for any particular reason that we need to show the seed
device, there isn't any.

So instead, do not traverse through the seed devices, just show the
lowest devid in the sprouted fsid.

After the patch:

 mount /dev/sda /btrfs
 mount: /btrfs: WARNING: device write-protected, mounted read-only.

 findmnt --output SOURCE,TARGET,UUID /btrfs
 SOURCE   TARGET UUID
 /dev/sda /btrfs 899f7027-3e46-4626-93e7-7d4c9ad19111

 btrfs dev add -f /dev/sdb /btrfs
 mount -o rw,remount /dev/sdb /btrfs

 findmnt --output SOURCE,TARGET,UUID /btrfs
 SOURCE   TARGET UUID
 /dev/sdb /btrfs 595ca0e6-b82e-46b5-b9e2-c72a6928be48

 mount /dev/sda /btrfs1
 mount: /btrfs1: WARNING: device write-protected, mounted read-only.

 btrfs dev add -f /dev/sdc /btrfs1

 findmnt --output SOURCE,TARGET,UUID /btrfs1
 SOURCE   TARGET  UUID
 /dev/sdc /btrfs1 ca1dbb7a-8446-4f95-853c-a20f3f82bdbb

 cat /proc/self/mounts | grep btrfs
 /dev/sdb /btrfs btrfs rw,relatime,noacl,space_cache,subvolid=5,subvol=/ 0 0
 /dev/sdc /btrfs1 btrfs ro,relatime,noacl,space_cache,subvolid=5,subvol=/ 0 0
Reported-by: NMartin K. Petersen <martin.petersen@oracle.com>
CC: stable@vger.kernel.org # 4.19+
Tested-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The option subvolrootid used to be a workaround for mounting subvolumes
and ineffective since 5e2a4b25 ("btrfs: deprecate subvolrootid mount
option"). We have subvol= that works and we don't need to keep the
cruft, let's remove it.
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The mount option alloc_start has no effect since 0d0c71b3 ("btrfs:
obsolete and remove mount option alloc_start") which has details why
it's been deprecated. We can remove it.
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Estimated time of removal of the functionality is 5.11, the option will
be still parsed but will have no effect.

Reasons for deprecation and removal:

- very poor naming choice of the mount option, it's supposed to cache
  and reuse the inode _numbers_, but it sounds a some generic cache for
  inodes

- the only known usecase where this option would make sense is on a
  32bit architecture where inode numbers in one subvolume would be
  exhausted due to 32bit inode::i_ino

- the cache is stored on disk, consumes space, needs to be loaded and
  written back

- new inode number allocation is slower due to lookups into the cache
  (compared to a simple increment which is the default)

- uses the free-space-cache code that is going to be deprecated as well
  in the future

Known problems:

- since 2011, returning EEXIST when there's not enough space in a page
  to store all checksums, see commit 4b9465cb ("Btrfs: add mount -o
  inode_cache")

Remaining issues:

- if the option was enabled, new inodes created, the option disabled
  again, the cache is still stored on the devices and there's currently
  no way to remove it
Signed-off-by: NDavid Sterba <dsterba@suse.com>