For data inodes this hook does nothing but to return -EAGAIN which is
used to signal to the endio routines that this bio belongs to a data
inode. If this is the case the actual retrying is handled by
bio_readpage_error. Alternatively, if this bio belongs to the btree
inode then btree_io_failed_hook just does some cleanup and doesn't retry
anything.

This patch simplifies the code flow by eliminating
readpage_io_failed_hook and instead open-coding btree_io_failed_hook in
end_bio_extent_readpage. Also eliminate some needless checks since IO is
always performed on either data inode or btree inode, both of which are
guaranteed to have their extent_io_tree::ops set.
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The btrfs_bio_end_io_t typedef was introduced with commit
a1d3c478 ("btrfs: btrfs_multi_bio replaced with btrfs_bio")
but never used anywhere. This commit also introduced a forward declaration
of 'struct btrfs_bio' which is only needed for btrfs_bio_end_io_t.

Remove both as they're not needed anywhere.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The end_io callback implemented as btrfs_io_bio_endio_readpage only
calls kfree. Also the callback is set only in case the csum buffer is
allocated and not pointing to the inline buffer. We can use that
information to drop the indirection and call a helper that will free the
csums only in the right case.

This shrinks struct btrfs_io_bio by 8 bytes.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The io_bio tracks checksums and has an inline buffer or an allocated
one. And there's a third member that points to the right one, but we
don't need to use an extra pointer for that. Let btrfs_io_bio::csum
point to the right buffer and check that the inline buffer is not
accidentally freed.

This shrinks struct btrfs_io_bio by 8 bytes.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The async_cow::root is used to propagate fs_info to async_cow_submit.
We can't use inode to reach it because it could become NULL after
write without compression in async_cow_start.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

There's one caller and its code is simple, we can open code it in
run_one_async_done. The errors are passed through bio.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Print a kernel log message when the balance ends, either for cancel or
completed or if it is paused.
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 information about balance arguments is important for system audit,
this patch prints the textual representation when balance starts or is
resumed.

Example command:

 $ btrfs balance start -f -mprofiles=raid1,convert=single,soft -dlimit=10..20,usage=50 /btrfs

Example kernel log output:

 BTRFS info (device sdb): balance: start -f -dusage=50,limit=10..20 -mconvert=single,soft,profiles=raid1 -sconvert=single,soft,profiles=raid1
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
[ update changelog, simplify code ]
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Factor out helper that describes block group flags from
describe_relocation. The result will not be longer than the given size.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
[ add comments ]
Signed-off-by: NDavid Sterba <dsterba@suse.com>

If the quota enable and snapshot creation ioctls are called concurrently
we can get into a deadlock where the task enabling quotas will deadlock
on the fs_info->qgroup_ioctl_lock mutex because it attempts to lock it
twice, or the task creating a snapshot tries to commit the transaction
while the task enabling quota waits for the former task to commit the
transaction while holding the mutex. The following time diagrams show how
both cases happen.

First scenario:

           CPU 0                                    CPU 1

 btrfs_ioctl()
  btrfs_ioctl_quota_ctl()
   btrfs_quota_enable()
    mutex_lock(fs_info->qgroup_ioctl_lock)
    btrfs_start_transaction()

                                             btrfs_ioctl()
                                              btrfs_ioctl_snap_create_v2
                                               create_snapshot()
                                                --> adds snapshot to the
                                                    list pending_snapshots
                                                    of the current
                                                    transaction

    btrfs_commit_transaction()
     create_pending_snapshots()
       create_pending_snapshot()
        qgroup_account_snapshot()
         btrfs_qgroup_inherit()
	   mutex_lock(fs_info->qgroup_ioctl_lock)
	    --> deadlock, mutex already locked
	        by this task at
		btrfs_quota_enable()

Second scenario:

           CPU 0                                    CPU 1

 btrfs_ioctl()
  btrfs_ioctl_quota_ctl()
   btrfs_quota_enable()
    mutex_lock(fs_info->qgroup_ioctl_lock)
    btrfs_start_transaction()

                                             btrfs_ioctl()
                                              btrfs_ioctl_snap_create_v2
                                               create_snapshot()
                                                --> adds snapshot to the
                                                    list pending_snapshots
                                                    of the current
                                                    transaction

                                                btrfs_commit_transaction()
                                                 --> waits for task at
                                                     CPU 0 to release
                                                     its transaction
                                                     handle

    btrfs_commit_transaction()
     --> sees another task started
         the transaction commit first
     --> releases its transaction
         handle
     --> waits for the transaction
         commit to be completed by
         the task at CPU 1

                                                 create_pending_snapshot()
                                                  qgroup_account_snapshot()
                                                   btrfs_qgroup_inherit()
                                                    mutex_lock(fs_info->qgroup_ioctl_lock)
                                                     --> deadlock, task at CPU 0
                                                         has the mutex locked but
                                                         it is waiting for us to
                                                         finish the transaction
                                                         commit

So fix this by setting the quota enabled flag in fs_info after committing
the transaction at btrfs_quota_enable(). This ends up serializing quota
enable and snapshot creation as if the snapshot creation happened just
before the quota enable request. The quota rescan task, scheduled after
committing the transaction in btrfs_quote_enable(), will do the accounting.

Fixes: 6426c7ad ("btrfs: qgroup: Fix qgroup accounting when creating snapshot")
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The available allocation bits members from struct btrfs_fs_info are
protected by a sequence lock, and when starting balance we access them
incorrectly in two different ways:

1) In the read sequence lock loop at btrfs_balance() we use the values we
   read from fs_info->avail_*_alloc_bits and we can immediately do actions
   that have side effects and can not be undone (printing a message and
   jumping to a label). This is wrong because a retry might be needed, so
   our actions must not have side effects and must be repeatable as long
   as read_seqretry() returns a non-zero value. In other words, we were
   essentially ignoring the sequence lock;

2) Right below the read sequence lock loop, we were reading the values
   from avail_metadata_alloc_bits and avail_data_alloc_bits without any
   protection from concurrent writers, that is, reading them outside of
   the read sequence lock critical section.

So fix this by making sure we only read the available allocation bits
while in a read sequence lock critical section and that what we do in the
critical section is repeatable (has nothing that can not be undone) so
that any eventual retry that is needed is handled properly.

Fixes: de98ced9 ("Btrfs: use seqlock to protect fs_info->avail_{data, metadata, system}_alloc_bits")
Fixes: 14506127 ("btrfs: fix a bogus warning when converting only data or metadata")
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

We can have a lot freed extents during the life span of transaction, so
the red black tree that keeps track of the ranges of each freed extent
(fs_info->freed_extents[]) can get quite big. When finishing a
transaction commit we find each range, process it (discard the extents,
unpin them) and then remove it from the red black tree.

We can use an extent state record as a cache when searching for a range,
so that when we clean the range we can use the cached extent state we
passed to the search function instead of iterating the red black tree
again. Doing things as fast as possible when finishing a transaction (in
state TRANS_STATE_UNBLOCKED) is convenient as it reduces the time we
block another task that wants to commit the next transaction.

So change clear_extent_dirty() to allow an optional extent state record to
be passed as an argument, which will be passed down to __clear_extent_bit.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

This patch lands the last case which needs to be handled by the fsid
change code. Namely, this is the case where a multidisk filesystem has
already undergone at least one successful fsid change i.e all disks
have the METADATA_UUID incompat bit and power failure occurs as another
fsid change is in progress. When such an event occurs, disks could be
split in 2 groups. One of the groups will have both METADATA_UUID and
CHANGING_FSID_V2 flags set coupled with old fsid/metadata_uuid pairs.
The other group of disks will have only METADATA_UUID bit set and their
fsid will be different than the one in disks in the first group. Here
we look at the following cases:

  a) A disk from the first group is scanned first, so fs_devices is
  created with stale fsid/metdata_uuid. Then when a disk from the
  second group is scanned it needs to first check whether there exists
  such an fs_devices that has fsid_change set to true (because it was
  created with a disk having the CHANGING_FSID_V2 flag), the
  metadata_uuid and fsid of the fs_devices will be different (since it was
  created by a disk which already has had at least 1 successful fsid change)
  and finally the metadata_uuid of the fs_devices will equal that of the
  currently scanned disk (because metadata_uuid never really changes).
  When the correct fs_devices is found the information from the scanned
  disk will replace the current one in fs_devices since the scanned disk
  will have higher generation number.

  b) A disk from the second group is scanned so fs_devices is created
  as usual with differing fsid/metdata_uid. Then when a disk from the
  first group is scanned the code detects that it has both
  CHANGING_FSID_V2 and METADATA_UUID flags set and will search for
  fs_devices that has differing metadata_uuid/fsid and whose
  metadata_uuid is the same as that of the scanned device.
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

This commit continues hardening the scanning code to handle cases where
power loss could have caused disks in a multi-disk filesystem to be
in inconsistent state. Namely handle the situation that can occur when
some of the disks in multi-disk fs have completed their fsid change i.e
they have METADATA_UUID incompat flag set, have cleared the
CHANGING_FSID_V2 flag and their fsid/metadata_uuid are different. At
the same time the other half of the disks will have their
fsid/metadata_uuid unchanged and will only have CHANGING_FSID_V2 flag.

This is handled by introducing code in the scan path which:

 a) Handles the case when a device with CHANGING_FSID_V2 flag is
 scanned and as a result btrfs_fs_devices is created with matching
 fsid/metdata_uuid. Subsequently, when a device with completed fsid
 change is scanned it will detect this via the new code in find_fsid
 i.e that such an fs_devices exist that fsid_change flag is set to true,
 it's metadata_uuid/fsid match and the metadata_uuid of the scanned
 device matches that of the fs_devices. In this case, it's important to
 note that the devices which has its fsid change completed will have a
 higher generation number than the device with FSID_CHANGING_V2 flag
 set, so its superblock block will be used during mount. To prevent an
 assertion triggering because the sb used for mounting will have
 differing fsid/metadata_uuid than the ones in the fs_devices struct
 also add code in device_list_add which overwrites the values in
 fs_devices.

 b) Alternatively we can end up with a device that completed its
 fsid change be scanned first which will create the respective
 btrfs_fs_devices struct with differing fsid/metadata_uuid. In this
 case when a device with FSID_CHANGING_V2 flag set is scanned it will
 call the newly added find_fsid_inprogress function which will return
 the correct fs_devices.
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

In order to gracefully handle split-brain scenario during fsid change
(which are very unlikely, yet possible), two more pieces of information
will be necessary:

1. The highest generation number among all devices registered to a
   particular btrfs_fs_devices

2. A boolean flag whether a given btrfs_fs_devices was created by a
   device which had the FSID_CHANGING_V2 flag set.

This is a preparatory patch and just introduces the variables as well
as code which sets them, their actual use is going to happen in a later
patch.
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Even though fsid change without rewrite is a very quick operation it's
still possible to experience a split-brain scenario if power loss occurs
at the most inconvenient time. This patch handles the case where power
failure occurs while the first transaction (the one setting
CHANGING_FSID_V2) flag is being persisted on disk. This can cause the
btrfs_fs_devices of this filesystem to be created by a device which:

 a) has the CHANGING_FSID_V2 flag set but its fsid value is intact

 b) or a device which doesn't have CHANGING_FSID_V2 flag set and its
    fsid value is intact

This situation is trivially handled by the current find_fsid code since
in both cases the devices are going to be treated like ordinary devices.
Since btrfs is always mounted using the superblock of the latest
device (the one with highest generation number), meaning it will have
the CHANGING_FSID_V2 flag set, ensure it's being cleared on mount. On
the first transaction commit following mount all disks will have it
cleared.
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Currently btrfs_fs_info structure contains a copy of the
fsid/metadata_uuid fields. Same values are also contained in the
btrfs_fs_devices structure which fs_info has a reference to. Let's
reduce duplication by removing the fields from fs_info and always refer
to the ones in fs_devices. No functional changes.
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Since the metadata_uuid is a new incompat feature it requires the
respective sysfs hooks. This patch adds the 'metdata_uuid' feature to
be shown if it supported by the kernel. Additionally it adds
/sys/fs/btrfs/UUID/metadata_uuid attribute which allows one to read
the current metadata_uuid.
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

This field is going to be used when the user wants to change the UUID
of the filesystem without having to rewrite all metadata blocks. This
field adds another level of indirection such that when the FSID is
changed what really happens is the current UUID (the one with which the
fs was created) is copied to the 'metadata_uuid' field in the superblock
as well as a new incompat flag is set METADATA_UUID. When the kernel
detects this flag is set it knows that the superblock in fact has 2
UUIDs:

1. Is the UUID which is user-visible, currently known as FSID.
2. Metadata UUID - this is the UUID which is stamped into all on-disk
   datastructures belonging to this file system.

When the new incompat flag is present device scanning checks whether
both fsid/metadata_uuid of the scanned device match any of the
registered filesystems. When the flag is not set then both UUIDs are
equal and only the FSID is retained on disk, metadata_uuid is set only
in-memory during mount.

Additionally a new metadata_uuid field is also added to the fs_info
struct. It's initialised either with the FSID in case METADATA_UUID
incompat flag is not set or with the metdata_uuid of the superblock
otherwise.

This commit introduces the new fields as well as the new incompat flag
and switches all users of the fsid to the new logic.
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
[ minor updates in comments ]
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Several functions in BTRFS are only used inside the source file they are
declared if CONFIG_BTRFS_FS_RUN_SANITY_TESTS is not defined. However if
CONFIG_BTRFS_FS_RUN_SANITY_TESTS is defined these functions are shared
with the unit tests code.

Before the introduction of the EXPORT_FOR_TESTS macro, these functions
could not be declared as static and the compiler had a harder task when
optimizing and inlining them.

As we have EXPORT_FOR_TESTS now, use it where appropriate to support the
compiler.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NJohannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Depending on whether CONFIG_BTRFS_FS_RUN_SANITY_TESTS is set, some BTRFS
functions are either local to the file they are implemented in and thus
should be declared static or are called from within the test
implementation defined in a different file.

Introduce an EXPORT_FOR_TESTS macro which depending on
CONFIG_BTRFS_FS_RUN_SANITY_TESTS either adds the 'static' keyword to a
function or not.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Up to commit 32955c54 ("btrfs: switch to discard_new_inode()") the
drop_on_err variable in btrfs_mkdir() was used to check whether the
inode had to be dropped via iput().

After commit 32955c54 ("btrfs: switch to discard_new_inode()")
discard_new_inode() is called when err is set and inode is non NULL.
Therefore drop_on_err is not used anymore and thus causes a warning when
building with -Wunused-but-set-variable.
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NQu Wenruo <wqu@suse.com>
Signed-off-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

lock_delalloc_pages should only return 2 values - 0 in case of success
and -EAGAIN if the range of pages to be locked should be shrunk due to
some of gone. Manual inspections confirms that this is indeed the case
since __process_pages_contig is where lock_delalloc_pages gets its
return value. The latter always returns 0  or -EAGAIN so the invariant
holds. No functional changes.
Reviewed-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

All callers of this function pass BTRFS_MAX_EXTENT_SIZE (128M) so let's
reduce the argument count and make that a local variable. No functional
changes.
Reviewed-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

It's unnecessary to check map->stripes[i].dev for NULL given its value
is already set and dereferenced above the the check. No functional
changes.
Reviewed-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

As of now only user requested replace cancel can cancel the
replace-scrub so no need to log the error.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

When we successfully cancel the device replace, its scrub worker returns
-ECANCELED, which is then passed to btrfs_dev_replace_finishing.

It cleans up based on the returned status and propagates the same
-ECANCELED back the parent function. As of now only user can cancel the
replace-scrub, so its ok to silence the warning here.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

We recast the replace return status
BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS to 0, to indicate no
error.
And since BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR should also return 0,
which is also declared as 0, so we just return. Instead add it to the if
statement so that there is enough clarity while reading the code.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

When the replace state is in the suspended state, btrfs_scrub_cancel()
should fail with -ENOTCONN as there is no scrub running. As a safety
catch check if btrfs_scrub_cancel() returns -ENOTCONN and assert if it
doesn't.
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 device-replace needs to check the result code of the scrub workers
in btrfs_dev_replace_cancel and distinguish if successful cancel
operation and when the there was no operation running.

If btrfs_scrub_cancel() fails, return
BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED so that user can try
to cancel the replace again.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The device replace cancel thread can race with the replace start thread
and if fs_info::scrubs_running is not yet set, btrfs_scrub_cancel() will
fail to stop the scrub thread.

The scrub thread continues with the scrub for replace which then will
try to write to the target device and which is already freed by the
cancel thread.

scrub_setup_ctx() warns as tgtdev is NULL.

  struct scrub_ctx *scrub_setup_ctx(struct btrfs_device *dev, int is_dev_replace)
  {
  ...
	  if (is_dev_replace) {
		  WARN_ON(!fs_info->dev_replace.tgtdev);  <===
		  sctx->pages_per_wr_bio = SCRUB_PAGES_PER_WR_BIO;
		  sctx->wr_tgtdev = fs_info->dev_replace.tgtdev;
		  sctx->flush_all_writes = false;
	  }

  [ 6724.497655] BTRFS info (device sdb): dev_replace from /dev/sdb (devid 1) to /dev/sdc started
  [ 6753.945017] BTRFS info (device sdb): dev_replace from /dev/sdb (devid 1) to /dev/sdc canceled
  [ 6852.426700] WARNING: CPU: 0 PID: 4494 at fs/btrfs/scrub.c:622 scrub_setup_ctx.isra.19+0x220/0x230 [btrfs]
  ...
  [ 6852.428928] RIP: 0010:scrub_setup_ctx.isra.19+0x220/0x230 [btrfs]
  ...
  [ 6852.432970] Call Trace:
  [ 6852.433202]  btrfs_scrub_dev+0x19b/0x5c0 [btrfs]
  [ 6852.433471]  btrfs_dev_replace_start+0x48c/0x6a0 [btrfs]
  [ 6852.433800]  btrfs_dev_replace_by_ioctl+0x3a/0x60 [btrfs]
  [ 6852.434097]  btrfs_ioctl+0x2476/0x2d20 [btrfs]
  [ 6852.434365]  ? do_sigaction+0x7d/0x1e0
  [ 6852.434623]  do_vfs_ioctl+0xa9/0x6c0
  [ 6852.434865]  ? syscall_trace_enter+0x1c8/0x310
  [ 6852.435124]  ? syscall_trace_enter+0x1c8/0x310
  [ 6852.435387]  ksys_ioctl+0x60/0x90
  [ 6852.435663]  __x64_sys_ioctl+0x16/0x20
  [ 6852.435907]  do_syscall_64+0x50/0x180
  [ 6852.436150]  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Further, as the replace thread enters scrub_write_page_to_dev_replace()
without the target device it panics:

  static int scrub_add_page_to_wr_bio(struct scrub_ctx *sctx,
				      struct scrub_page *spage)
  {
  ...
	bio_set_dev(bio, sbio->dev->bdev); <======

  [ 6929.715145] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0
  ..
  [ 6929.717106] Workqueue: btrfs-scrub btrfs_scrub_helper [btrfs]
  [ 6929.717420] RIP: 0010:scrub_write_page_to_dev_replace+0xb4/0x260
  [btrfs]
  ..
  [ 6929.721430] Call Trace:
  [ 6929.721663]  scrub_write_block_to_dev_replace+0x3f/0x60 [btrfs]
  [ 6929.721975]  scrub_bio_end_io_worker+0x1af/0x490 [btrfs]
  [ 6929.722277]  normal_work_helper+0xf0/0x4c0 [btrfs]
  [ 6929.722552]  process_one_work+0x1f4/0x520
  [ 6929.722805]  ? process_one_work+0x16e/0x520
  [ 6929.723063]  worker_thread+0x46/0x3d0
  [ 6929.723313]  kthread+0xf8/0x130
  [ 6929.723544]  ? process_one_work+0x520/0x520
  [ 6929.723800]  ? kthread_delayed_work_timer_fn+0x80/0x80
  [ 6929.724081]  ret_from_fork+0x3a/0x50

Fix this by letting the btrfs_dev_replace_finishing() to do the job of
cleaning after the cancel, including freeing of the target device.
btrfs_dev_replace_finishing() is called when btrfs_scub_dev() returns
along with the scrub return status.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

In a secnario where balance and replace co-exists as below,

  - start balance
  - pause balance
  - start replace
  - reboot

and when system restarts, balance resumes first. Then the replace is
attempted to restart but will fail as the EXCL_OP lock is already held
by the balance. If so place the replace state back to
BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED state.

Fixes: 010a47bd ("btrfs: add proper safety check before resuming dev-replace")
CC: stable@vger.kernel.org # 4.18+
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

At the time of forced unmount we place the running replace to
BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED state, so when the system comes
back and expect the target device is missing.

Then let the replace state continue to be in
BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED state instead of
BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED as there isn't any matching scrub
running as part of replace.

Fixes: e93c89c1 ("Btrfs: add new sources for device replace code")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

There isn't any other consumer other than in its own file dev-replace.c.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

It's not that impossible to imagine that a device OR a btrfs image is
copied just by using the dd or the cp command. Which in case both the
copies of the btrfs will have the same fsid. If on the system with
automount enabled, the copied FS gets scanned.

We have a known bug in btrfs, that we let the device path be changed
after the device has been mounted. So using this loop hole the new
copied device would appears as if its mounted immediately after it's
been copied.

For example:

Initially.. /dev/mmcblk0p4 is mounted as /

  $ lsblk
  NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
  mmcblk0     179:0    0 29.2G  0 disk
  |-mmcblk0p4 179:4    0    4G  0 part /
  |-mmcblk0p2 179:2    0  500M  0 part /boot
  |-mmcblk0p3 179:3    0  256M  0 part [SWAP]
  `-mmcblk0p1 179:1    0  256M  0 part /boot/efi

  $ btrfs fi show
     Label: none  uuid: 07892354-ddaa-4443-90ea-f76a06accaba
     Total devices 1 FS bytes used 1.40GiB
     devid    1 size 4.00GiB used 3.00GiB path /dev/mmcblk0p4

Copy mmcblk0 to sda

  $ dd if=/dev/mmcblk0 of=/dev/sda

And immediately after the copy completes the change in the device
superblock is notified which the automount scans using btrfs device scan
and the new device sda becomes the mounted root device.

  $ lsblk
  NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
  sda           8:0    1 14.9G  0 disk
  |-sda4        8:4    1    4G  0 part /
  |-sda2        8:2    1  500M  0 part
  |-sda3        8:3    1  256M  0 part
  `-sda1        8:1    1  256M  0 part
  mmcblk0     179:0    0 29.2G  0 disk
  |-mmcblk0p4 179:4    0    4G  0 part
  |-mmcblk0p2 179:2    0  500M  0 part /boot
  |-mmcblk0p3 179:3    0  256M  0 part [SWAP]
  `-mmcblk0p1 179:1    0  256M  0 part /boot/efi

  $ btrfs fi show /
    Label: none  uuid: 07892354-ddaa-4443-90ea-f76a06accaba
    Total devices 1 FS bytes used 1.40GiB
    devid    1 size 4.00GiB used 3.00GiB path /dev/sda4

The bug is quite nasty that you can't either unmount /dev/sda4 or
/dev/mmcblk0p4. And the problem does not get solved until you take sda
out of the system on to another system to change its fsid using the
'btrfstune -u' command.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Instead of hardcoding exceptions for RAID5 and RAID6 in the code, use an
nparity field in raid_attr.
Signed-off-by: NHans van Kranenburg <hans.van.kranenburg@mendix.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

RAID5 and RAID6 profile store one copy of the data, not 2 or 3. These
values are not yet used anywhere so there's no change.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NHans van Kranenburg <hans.van.kranenburg@mendix.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

Commit 92e222df "btrfs: alloc_chunk: fix DUP stripe size handling"
fixed calculating the stripe_size for a new DUP chunk.

However, the same calculation reappears a bit later, and that one was
not changed yet. The resulting bug that is exposed is that the newly
allocated device extents ('stripes') can have a few MiB overlap with the
next thing stored after them, which is another device extent or the end
of the disk.

The scenario in which this can happen is:
* The block device for the filesystem is less than 10GiB in size.
* The amount of contiguous free unallocated disk space chosen to use for
  chunk allocation is 20% of the total device size, or a few MiB more or
  less.

An example:
- The filesystem device is 7880MiB (max_chunk_size gets set to 788MiB)
- There's 1578MiB unallocated raw disk space left in one contiguous
  piece.

In this case stripe_size is first calculated as 789MiB, (half of
1578MiB).

Since 789MiB (stripe_size * data_stripes) > 788MiB (max_chunk_size), we
enter the if block. Now stripe_size value is immediately overwritten
while calculating an adjusted value based on max_chunk_size, which ends
up as 788MiB.

Next, the value is rounded up to a 16MiB boundary, 800MiB, which is
actually more than the value we had before. However, the last comparison
fails to detect this, because it's comparing the value with the total
amount of free space, which is about twice the size of stripe_size.

In the example above, this means that the resulting raw disk space being
allocated is 1600MiB, while only a gap of 1578MiB has been found. The
second device extent object for this DUP chunk will overlap for 22MiB
with whatever comes next.

The underlying problem here is that the stripe_size is reused all the
time for different things. So, when entering the code in the if block,
stripe_size is immediately overwritten with something else. If later we
decide we want to have the previous value back, then the logic to
compute it was copy pasted in again.

With this change, the value in stripe_size is not unnecessarily
destroyed, so the duplicated calculation is not needed any more.
Signed-off-by: NHans van Kranenburg <hans.van.kranenburg@mendix.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The variable num_bytes is really a way too generic name for a variable
in this function. There are a dozen other variables that hold a number
of bytes as value.

Give it a name that actually describes what it does, which is holding
the size of the chunk that we're allocating.
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NHans van Kranenburg <hans.van.kranenburg@mendix.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

The variable num_bytes is used to store the chunk length of the chunk
that we're allocating. Do not reuse it for something really different in
the same function.
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NHans van Kranenburg <hans.van.kranenburg@mendix.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>