The delayed inode code batches up changes to the btree in hopes of doing
them in bulk.  As the changes build up, processes kick off worker
threads and wait for them to make progress.

The current code kicks off an async work queue item for each delayed
node, which creates a lot of churn.  It also uses a fixed 1 HZ waiting
period for the throttle, which allows us to build a lot of pending
work and can slow down the commit.

This changes us to watch a sequence counter as it is bumped during the
operations.  We kick off fewer work items and have each work item do
more work.
Signed-off-by: NChris Mason <chris.mason@fusionio.com>

We're running into having 50-100 orphans left over with xfstests 83
because of ENOSPC when trying to start the transaction for the inode update.
But in fact, it makes no sense in updating the inode for the new size while
we're deleting the stupid thing. This patch fixes this problem.
Reported-by: NJosef Bacik <jbacik@fusionio.com>
Signed-off-by: NMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: NJosef Bacik <jbacik@fusionio.com>

Those crazy gentoo guys have been complaining about ENOSPC errors on their
portage volumes.  This is because doing things like untar tends to create
lots of new files which will soak up all the reservation space in the
delayed inodes.  Usually this gets papered over by the fact that we will try
and commit the transaction, however if this happens in the wrong spot or we
choose not to commit the transaction you will be screwed.  So add the
ability to expclitly flush delayed inodes to free up space.  Please test
this out guys to make sure it works since as usual I cannot reproduce.
Thanks,
Signed-off-by: NJosef Bacik <jbacik@fusionio.com>

the items of the delayed inodes were forgotten to be freed, this patch
fixes it.
Signed-off-by: NMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: NChris Mason <chris.mason@fusionio.com>

This allows us to move duplicated code in <asm/atomic.h>
(atomic_inc_not_zero() for now) to <linux/atomic.h>
Signed-off-by: NArun Sharma <asharma@fb.com>
Reviewed-by: NEric Dumazet <eric.dumazet@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: NMike Frysinger <vapier@gentoo.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When iputting the inode, We may leave the delayed nodes if they have some
delayed items that have not been dealt with. So when the inode is read again,
we must look up the relative delayed node, and use the information in it to
initialize the inode. Or we will get inconsonant inode information, it may
cause that the same directory index number is allocated again, and hit the
following oops:

[ 5447.554187] err add delayed dir index item(name: pglog_0.965_0) into the
insertion tree of the delayed node(root id: 262, inode id: 258, errno: -17)
[ 5447.569766] ------------[ cut here ]------------
[ 5447.575361] kernel BUG at fs/btrfs/delayed-inode.c:1301!
[SNIP]
[ 5447.790721] Call Trace:
[ 5447.793191]  [<ffffffffa0641c4e>] btrfs_insert_dir_item+0x189/0x1bb [btrfs]
[ 5447.800156]  [<ffffffffa0651a45>] btrfs_add_link+0x12b/0x191 [btrfs]
[ 5447.806517]  [<ffffffffa0651adc>] btrfs_add_nondir+0x31/0x58 [btrfs]
[ 5447.812876]  [<ffffffffa0651d6a>] btrfs_create+0xf9/0x197 [btrfs]
[ 5447.818961]  [<ffffffff8111f840>] vfs_create+0x72/0x92
[ 5447.824090]  [<ffffffff8111fa8c>] do_last+0x22c/0x40b
[ 5447.829133]  [<ffffffff8112076a>] path_openat+0xc0/0x2ef
[ 5447.834438]  [<ffffffff810c58e2>] ? __perf_event_task_sched_out+0x24/0x44
[ 5447.841216]  [<ffffffff8103ecdd>] ? perf_event_task_sched_out+0x59/0x67
[ 5447.847846]  [<ffffffff81121a79>] do_filp_open+0x3d/0x87
[ 5447.853156]  [<ffffffff811e126c>] ? strncpy_from_user+0x43/0x4d
[ 5447.859072]  [<ffffffff8111f1f5>] ? getname_flags+0x2e/0x80
[ 5447.864636]  [<ffffffff8111f179>] ? do_getname+0x14b/0x173
[ 5447.870112]  [<ffffffff8111f1b7>] ? audit_getname+0x16/0x26
[ 5447.875682]  [<ffffffff8112b1ab>] ? spin_lock+0xe/0x10
[ 5447.880882]  [<ffffffff81112d39>] do_sys_open+0x69/0xae
[ 5447.886153]  [<ffffffff81112db1>] sys_open+0x20/0x22
[ 5447.891114]  [<ffffffff813b9aab>] system_call_fastpath+0x16/0x1b

Fix it by reusing the old delayed node.
Reported-by: NJim Schutt <jaschut@sandia.gov>
Signed-off-by: NMiao Xie <miaox@cn.fujitsu.com>
Tested-by: NJim Schutt <jaschut@sandia.gov>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Snapshot creation has two phases.  One is the initial snapshot setup,
and the second is done during commit, while nobody is allowed to modify
the root we are snapshotting.

The delayed metadata insertion code can break that rule, it does a
delayed inode update on the inode of the parent of the snapshot,
and delayed directory item insertion.

This makes sure to run the pending delayed operations before we
record the snapshot root, which avoids corruptions.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

We have migrated the space for the delayed inode items from
trans_block_rsv to global_block_rsv, but we forgot to set trans->block_rsv to
global_block_rsv when we doing delayed inode operations, and the following Oops
happened:

[ 9792.654889] ------------[ cut here ]------------
[ 9792.654898] WARNING: at fs/btrfs/extent-tree.c:5681
btrfs_alloc_free_block+0xca/0x27c [btrfs]()
[ 9792.654899] Hardware name: To Be Filled By O.E.M.
[ 9792.654900] Modules linked in: btrfs zlib_deflate libcrc32c
ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables
arc4 rt61pci rt2x00pci rt2x00lib snd_hda_codec_hdmi mac80211
snd_hda_codec_realtek cfg80211 snd_hda_intel edac_core snd_seq rfkill
pcspkr serio_raw snd_hda_codec eeprom_93cx6 edac_mce_amd sp5100_tco
i2c_piix4 k10temp snd_hwdep snd_seq_device snd_pcm floppy r8169 xhci_hcd
mii snd_timer snd soundcore snd_page_alloc ipv6 firewire_ohci pata_acpi
ata_generic firewire_core pata_via crc_itu_t radeon ttm drm_kms_helper
drm i2c_algo_bit i2c_core [last unloaded: scsi_wait_scan]
[ 9792.654919] Pid: 2762, comm: rm Tainted: G        W   2.6.39+ #1
[ 9792.654920] Call Trace:
[ 9792.654922]  [<ffffffff81053c4a>] warn_slowpath_common+0x83/0x9b
[ 9792.654925]  [<ffffffff81053c7c>] warn_slowpath_null+0x1a/0x1c
[ 9792.654933]  [<ffffffffa038e747>] btrfs_alloc_free_block+0xca/0x27c [btrfs]
[ 9792.654945]  [<ffffffffa03b8562>] ? map_extent_buffer+0x6e/0xa8 [btrfs]
[ 9792.654953]  [<ffffffffa038189b>] __btrfs_cow_block+0xfc/0x30c [btrfs]
[ 9792.654963]  [<ffffffffa0396aa6>] ? btrfs_buffer_uptodate+0x47/0x58 [btrfs]
[ 9792.654970]  [<ffffffffa0382e48>] ? read_block_for_search+0x94/0x368 [btrfs]
[ 9792.654978]  [<ffffffffa0381ba9>] btrfs_cow_block+0xfe/0x146 [btrfs]
[ 9792.654986]  [<ffffffffa03848b0>] btrfs_search_slot+0x14d/0x4b6 [btrfs]
[ 9792.654997]  [<ffffffffa03b8562>] ? map_extent_buffer+0x6e/0xa8 [btrfs]
[ 9792.655022]  [<ffffffffa03938e8>] btrfs_lookup_inode+0x2f/0x8f [btrfs]
[ 9792.655025]  [<ffffffff8147afac>] ? _cond_resched+0xe/0x22
[ 9792.655027]  [<ffffffff8147b892>] ? mutex_lock+0x29/0x50
[ 9792.655039]  [<ffffffffa03d41b1>] btrfs_update_delayed_inode+0x72/0x137 [btrfs]
[ 9792.655051]  [<ffffffffa03d4ea2>] btrfs_run_delayed_items+0x90/0xdb [btrfs]
[ 9792.655062]  [<ffffffffa039a69b>] btrfs_commit_transaction+0x228/0x654 [btrfs]
[ 9792.655064]  [<ffffffff8106e8da>] ? remove_wait_queue+0x3a/0x3a
[ 9792.655075]  [<ffffffffa03a2fa5>] btrfs_evict_inode+0x14d/0x202 [btrfs]
[ 9792.655077]  [<ffffffff81132bd6>] evict+0x71/0x111
[ 9792.655079]  [<ffffffff81132de0>] iput+0x12a/0x132
[ 9792.655081]  [<ffffffff8112aa3a>] do_unlinkat+0x106/0x155
[ 9792.655083]  [<ffffffff81127b83>] ? path_put+0x1f/0x23
[ 9792.655085]  [<ffffffff8109c53c>] ? audit_syscall_entry+0x145/0x171
[ 9792.655087]  [<ffffffff81128410>] ? putname+0x34/0x36
[ 9792.655090]  [<ffffffff8112b441>] sys_unlinkat+0x29/0x2b
[ 9792.655092]  [<ffffffff81482c42>] system_call_fastpath+0x16/0x1b
[ 9792.655093] ---[ end trace 02b696eb02b3f768 ]---

This patch fix it by setting the reservation of the transaction handle to the
correct one.
Reported-by: NJosef Bacik <josef@redhat.com>
Signed-off-by: NMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Changelog V5 -> V6:
- Fix oom when the memory load is high, by storing the delayed nodes into the
  root's radix tree, and letting btrfs inodes go.

Changelog V4 -> V5:
- Fix the race on adding the delayed node to the inode, which is spotted by
  Chris Mason.
- Merge Chris Mason's incremental patch into this patch.
- Fix deadlock between readdir() and memory fault, which is reported by
  Itaru Kitayama.

Changelog V3 -> V4:
- Fix nested lock, which is reported by Itaru Kitayama, by updating space cache
  inode in time.

Changelog V2 -> V3:
- Fix the race between the delayed worker and the task which does delayed items
  balance, which is reported by Tsutomu Itoh.
- Modify the patch address David Sterba's comment.
- Fix the bug of the cpu recursion spinlock, reported by Chris Mason

Changelog V1 -> V2:
- break up the global rb-tree, use a list to manage the delayed nodes,
  which is created for every directory and file, and used to manage the
  delayed directory name index items and the delayed inode item.
- introduce a worker to deal with the delayed nodes.

Compare with Ext3/4, the performance of file creation and deletion on btrfs
is very poor. the reason is that btrfs must do a lot of b+ tree insertions,
such as inode item, directory name item, directory name index and so on.

If we can do some delayed b+ tree insertion or deletion, we can improve the
performance, so we made this patch which implemented delayed directory name
index insertion/deletion and delayed inode update.

Implementation:
- introduce a delayed root object into the filesystem, that use two lists to
  manage the delayed nodes which are created for every file/directory.
  One is used to manage all the delayed nodes that have delayed items. And the
  other is used to manage the delayed nodes which is waiting to be dealt with
  by the work thread.
- Every delayed node has two rb-tree, one is used to manage the directory name
  index which is going to be inserted into b+ tree, and the other is used to
  manage the directory name index which is going to be deleted from b+ tree.
- introduce a worker to deal with the delayed operation. This worker is used
  to deal with the works of the delayed directory name index items insertion
  and deletion and the delayed inode update.
  When the delayed items is beyond the lower limit, we create works for some
  delayed nodes and insert them into the work queue of the worker, and then
  go back.
  When the delayed items is beyond the upper bound, we create works for all
  the delayed nodes that haven't been dealt with, and insert them into the work
  queue of the worker, and then wait for that the untreated items is below some
  threshold value.
- When we want to insert a directory name index into b+ tree, we just add the
  information into the delayed inserting rb-tree.
  And then we check the number of the delayed items and do delayed items
  balance. (The balance policy is above.)
- When we want to delete a directory name index from the b+ tree, we search it
  in the inserting rb-tree at first. If we look it up, just drop it. If not,
  add the key of it into the delayed deleting rb-tree.
  Similar to the delayed inserting rb-tree, we also check the number of the
  delayed items and do delayed items balance.
  (The same to inserting manipulation)
- When we want to update the metadata of some inode, we cached the data of the
  inode into the delayed node. the worker will flush it into the b+ tree after
  dealing with the delayed insertion and deletion.
- We will move the delayed node to the tail of the list after we access the
  delayed node, By this way, we can cache more delayed items and merge more
  inode updates.
- If we want to commit transaction, we will deal with all the delayed node.
- the delayed node will be freed when we free the btrfs inode.
- Before we log the inode items, we commit all the directory name index items
  and the delayed inode update.

I did a quick test by the benchmark tool[1] and found we can improve the
performance of file creation by ~15%, and file deletion by ~20%.

Before applying this patch:
Create files:
        Total files: 50000
        Total time: 1.096108
        Average time: 0.000022
Delete files:
        Total files: 50000
        Total time: 1.510403
        Average time: 0.000030

After applying this patch:
Create files:
        Total files: 50000
        Total time: 0.932899
        Average time: 0.000019
Delete files:
        Total files: 50000
        Total time: 1.215732
        Average time: 0.000024

[1] http://marc.info/?l=linux-btrfs&m=128212635122920&q=p3

Many thanks for Kitayama-san's help!
Signed-off-by: NMiao Xie <miaox@cn.fujitsu.com>
Reviewed-by: NDavid Sterba <dave@jikos.cz>
Tested-by: NTsutomu Itoh <t-itoh@jp.fujitsu.com>
Tested-by: NItaru Kitayama <kitayama@cl.bb4u.ne.jp>
Signed-off-by: NChris Mason <chris.mason@oracle.com>