In commit 8d3d7e2b, we changed xfs_qm_dqpurge to bail out if we
can't lock the dquot buf to flush the dquot.  This prevents the AIL from
blocking on the dquot, but it also forgets to clear the FREEING flag on
its way out.  A subsequent purge attempt will see the FREEING flag is
set and bail out, which leads to dqpurge_all failing to purge all the
dquots.

(copy-pasting from Dave Chinner's identical patch)

This was found by inspection after having xfs/305 hang 1 in ~50
iterations in a quotaoff operation:

[ 8872.301115] xfs_quota       D13888 92262  91813 0x00004002
[ 8872.302538] Call Trace:
[ 8872.303193]  __schedule+0x2d2/0x780
[ 8872.304108]  ? do_raw_spin_unlock+0x57/0xd0
[ 8872.305198]  schedule+0x6e/0xe0
[ 8872.306021]  schedule_timeout+0x14d/0x300
[ 8872.307060]  ? __next_timer_interrupt+0xe0/0xe0
[ 8872.308231]  ? xfs_qm_dqusage_adjust+0x200/0x200
[ 8872.309422]  schedule_timeout_uninterruptible+0x2a/0x30
[ 8872.310759]  xfs_qm_dquot_walk.isra.0+0x15a/0x1b0
[ 8872.311971]  xfs_qm_dqpurge_all+0x7f/0x90
[ 8872.313022]  xfs_qm_scall_quotaoff+0x18d/0x2b0
[ 8872.314163]  xfs_quota_disable+0x3a/0x60
[ 8872.315179]  kernel_quotactl+0x7e2/0x8d0
[ 8872.316196]  ? __do_sys_newstat+0x51/0x80
[ 8872.317238]  __x64_sys_quotactl+0x1e/0x30
[ 8872.318266]  do_syscall_64+0x46/0x90
[ 8872.319193]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 8872.320490] RIP: 0033:0x7f46b5490f2a
[ 8872.321414] Code: Bad RIP value.

Returning -EAGAIN from xfs_qm_dqpurge() without clearing the
XFS_DQ_FREEING flag means the xfs_qm_dqpurge_all() code can never
free the dquot, and we loop forever waiting for the XFS_DQ_FREEING
flag to go away on the dquot that leaked it via -EAGAIN.

Fixes: 8d3d7e2b ("xfs: trylock underlying buffer on dquot flush")
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NAllison Collins <allison.henderson@oracle.com>
Reviewed-by: NChandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>

The block reservation calculation for inode allocation is supposed
to consist of the blocks required for the inode chunk plus
(maxlevels-1) of the inode btree multiplied by the number of inode
btrees in the fs (2 when finobt is enabled, 1 otherwise).

Instead, the macro returns (ialloc_blocks + 2) due to a precedence
error in the calculation logic. This leads to block reservation
overruns via generic/531 on small block filesystems with finobt
enabled. Add braces to fix the calculation and reserve the
appropriate number of blocks.

Fixes: 9d43b180 ("xfs: update inode allocation/free transaction reservations for finobt")
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

xfsaild is racy with respect to transaction abort and shutdown in
that the task can idle or exit with an empty AIL but buffers still
on the delwri queue. This was partly addressed by cancelling the
delwri queue before the task exits to prevent memory leaks, but it's
also possible for xfsaild to empty and idle with buffers on the
delwri queue. For example, a transaction that pins a buffer that
also happens to sit on the AIL delwri queue will explicitly remove
the associated log item from the AIL if the transaction aborts. The
side effect of this is an unmount hang in xfs_wait_buftarg() as the
associated buffers remain held by the delwri queue indefinitely.
This is reproduced on repeated runs of generic/531 with an fs format
(-mrmapbt=1 -bsize=1k) that happens to also reproduce transaction
aborts.

Update xfsaild to not idle until both the AIL and associated delwri
queue are empty and update the push code to continue delwri queue
submission attempts even when the AIL is empty. This allows the AIL
to eventually release aborted buffers stranded on the delwri queue
when they are unlocked by the associated transaction. This should
have no significant effect on normal runtime behavior because the
xfsaild currently idles only when the AIL is empty and in practice
the AIL is rarely empty with a populated delwri queue. The items
must be AIL resident to land in the queue in the first place and
generally aren't removed until writeback completes.

Note that the pre-existing delwri queue cancel logic in the exit
path is retained because task stop is external, could technically
come at any point, and xfsaild is still responsible to release its
buffer references before it exits.
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

The MS_I_VERSION mount flag is exposed via the VFS, as documented
in the mount manpages etc; see the iversion and noiversion mount
options in mount(8).

As a result, mount -o remount looks for this option in /proc/mounts
and will only send the I_VERSION flag back in during remount it it
is present.  Since it's not there, a remount will /remove/ the
I_VERSION flag at the vfs level, and iversion functionality is lost.

xfs v5 superblocks intend to always have i_version enabled; it is
set as a default at mount time, but is lost during remount for the
reasons above.

The generic fix would be to expose this documented option in
/proc/mounts, but since that was rejected, fix it up again in the
xfs remount path instead, so that at least xfs won't suffer from
this misbehavior.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

Remove duplicated include.
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>

These two definitions are unused now.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>

In the course of some operations, we look up the perag from
the mount multiple times to get or change perag information.
These are often very short pieces of code, so while the
lookup cost is generally low, the cost of the lookup is far
higher than the cost of the operation we are doing on the
perag.

Since we changed buffers to hold references to the perag
they are cached in, many modification contexts already hold
active references to the perag that are held across these
operations. This is especially true for any operation that
is serialised by an allocation group header buffer.

In these cases, we can just use the buffer's reference to
the perag to avoid needing to do lookups to access the
perag. This means that many operations don't need to do
perag lookups at all to access the perag because they've
already looked up objects that own persistent references
and hence can use that reference instead.

Cc: Dave Chinner <dchinner@redhat.com>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Signed-off-by: NGao Xiang <hsiangkao@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Depending on the workloads, the following circular locking dependency
warning between sb_internal (a percpu rwsem) and fs_reclaim (a pseudo
lock) may show up:

======================================================
WARNING: possible circular locking dependency detected
5.0.0-rc1+ #60 Tainted: G        W
------------------------------------------------------
fsfreeze/4346 is trying to acquire lock:
0000000026f1d784 (fs_reclaim){+.+.}, at:
fs_reclaim_acquire.part.19+0x5/0x30

but task is already holding lock:
0000000072bfc54b (sb_internal){++++}, at: percpu_down_write+0xb4/0x650

which lock already depends on the new lock.
  :
 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_internal);
                               lock(fs_reclaim);
                               lock(sb_internal);
  lock(fs_reclaim);

 *** DEADLOCK ***

4 locks held by fsfreeze/4346:
 #0: 00000000b478ef56 (sb_writers#8){++++}, at: percpu_down_write+0xb4/0x650
 #1: 000000001ec487a9 (&type->s_umount_key#28){++++}, at: freeze_super+0xda/0x290
 #2: 000000003edbd5a0 (sb_pagefaults){++++}, at: percpu_down_write+0xb4/0x650
 #3: 0000000072bfc54b (sb_internal){++++}, at: percpu_down_write+0xb4/0x650

stack backtrace:
Call Trace:
 dump_stack+0xe0/0x19a
 print_circular_bug.isra.10.cold.34+0x2f4/0x435
 check_prev_add.constprop.19+0xca1/0x15f0
 validate_chain.isra.14+0x11af/0x3b50
 __lock_acquire+0x728/0x1200
 lock_acquire+0x269/0x5a0
 fs_reclaim_acquire.part.19+0x29/0x30
 fs_reclaim_acquire+0x19/0x20
 kmem_cache_alloc+0x3e/0x3f0
 kmem_zone_alloc+0x79/0x150
 xfs_trans_alloc+0xfa/0x9d0
 xfs_sync_sb+0x86/0x170
 xfs_log_sbcount+0x10f/0x140
 xfs_quiesce_attr+0x134/0x270
 xfs_fs_freeze+0x4a/0x70
 freeze_super+0x1af/0x290
 do_vfs_ioctl+0xedc/0x16c0
 ksys_ioctl+0x41/0x80
 __x64_sys_ioctl+0x73/0xa9
 do_syscall_64+0x18f/0xd23
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

This is a false positive as all the dirty pages are flushed out before
the filesystem can be frozen.

One way to avoid this splat is to add GFP_NOFS to the affected allocation
calls by using the memalloc_nofs_save()/memalloc_nofs_restore() pair.
This shouldn't matter unless the system is really running out of memory.
In that particular case, the filesystem freeze operation may fail while
it was succeeding previously.

Without this patch, the command sequence below will show that the lock
dependency chain sb_internal -> fs_reclaim exists.

 # fsfreeze -f /home
 # fsfreeze --unfreeze /home
 # grep -i fs_reclaim -C 3 /proc/lockdep_chains | grep -C 5 sb_internal

After applying the patch, such sb_internal -> fs_reclaim lock dependency
chain can no longer be found. Because of that, the locking dependency
warning will not be shown.
Suggested-by: NDave Chinner <david@fromorbit.com>
Signed-off-by: NWaiman Long <longman@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

Make sure the rtbitmap is large enough to store the entire bitmap.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NAllison Collins <allison.henderson@oracle.com>

Ensure that the realtime bitmap file is backed entirely by written
extents.  No holes, no unwritten blocks, etc.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NAllison Collins <allison.henderson@oracle.com>

This debug code is called on every xfs_iflush() call, which then
checks every inode in the buffer for non-zero unlinked list field.
Hence it checks every inode in the cluster buffer every time a
single inode on that cluster it flushed. This is resulting in:

-   38.91%     5.33%  [kernel]  [k] xfs_iflush
   - 17.70% xfs_iflush
      - 9.93% xfs_inobp_check
           4.36% xfs_buf_offset

10% of the CPU time spent flushing inodes is repeatedly checking
unlinked fields in the buffer. We don't need to do this.

The other place we call xfs_inobp_check() is
xfs_iunlink_update_dinode(), and this is after we've done this
assert for the agino we are about to write into that inode:

	ASSERT(xfs_verify_agino_or_null(mp, agno, next_agino));

which means we've already checked that the agino we are about to
write is not 0 on debug kernels. The inode buffer verifiers do
everything else we need, so let's just remove this debug code.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

xfs_iflush_done() does 3 distinct operations to the inodes attached
to the buffer. Separate these operations out into functions so that
it is easier to modify these operations independently in future.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Now that we have all the dirty inodes attached to the cluster
buffer, we don't actually have to do radix tree lookups to find
them. Sure, the radix tree is efficient, but walking a linked list
of just the dirty inodes attached to the buffer is much better.

We are also no longer dependent on having a locked inode passed into
the function to determine where to start the lookup. This means we
can drop it from the function call and treat all inodes the same.

We also make xfs_iflush_cluster skip inodes marked with
XFS_IRECLAIM. This we avoid races with inodes that reclaim is
actively referencing or are being re-initialised by inode lookup. If
they are actually dirty, they'll get written by a future cluster
flush....

We also add a shutdown check after obtaining the flush lock so that
we catch inodes that are dirty in memory and may have inconsistent
state due to the shutdown in progress. We abort these inodes
directly and so they remove themselves directly from the buffer list
and the AIL rather than having to wait for the buffer to be failed
and callbacks run to be processed correctly.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

with xfs_iflush() gone, we can rename xfs_iflush_int() back to
xfs_iflush(). Also move it up above xfs_iflush_cluster() so we don't
need the forward definition any more.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NAmir Goldstein <amir73il@gmail.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Now we have a cached buffer on inode log items, we don't need
to do buffer lookups when flushing inodes anymore - all we need
to do is lock the buffer and we are ready to go.

This largely gets rid of the need for xfs_iflush(), which is
essentially just a mechanism to look up the buffer and flush the
inode to it. Instead, we can just call xfs_iflush_cluster() with a
few modifications to ensure it also flushes the inode we already
hold locked.

This allows the AIL inode item pushing to be almost entirely
non-blocking in XFS - we won't block unless memory allocation
for the cluster inode lookup blocks or the block device queues are
full.

Writeback during inode reclaim becomes a little more complex because
we now have to lock the buffer ourselves, but otherwise this change
is largely a functional no-op that removes a whole lot of code.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Rather than attach inodes to the cluster buffer just when we are
doing IO, attach the inodes to the cluster buffer when they are
dirtied. The means the buffer always carries a list of dirty inodes
that reference it, and we can use that list to make more fundamental
changes to inode writeback that aren't otherwise possible.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Once we have inodes pinning the cluster buffer and attached whenever
they are dirty, we no longer have a guarantee that the items are
flush locked when we lock the cluster buffer. Hence we cannot just
walk the buffer log item list and modify the attached inodes.

If the inode is not flush locked, we have to ILOCK it first and then
flush lock it to do all the prerequisite checks needed to avoid
races with other code. This is already handled by
xfs_ifree_get_one_inode(), so rework the inode iteration loop and
function to update all inodes in cache whether they are attached to
the buffer or not.

Note: we also remove the copying of the log item lsn to the
ili_flush_lsn as xfs_iflush_done() now uses the XFS_ISTALE flag to
trigger aborts and so flush lsn matching is not needed in IO
completion for processing freed inodes.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Inode reclaim is quite different now to the way described in various
comments, so update all the comments explaining what it does and how
it works.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Clean up xfs_reclaim_inodes() callers. Most callers want blocking
behaviour, so just make the existing SYNC_WAIT behaviour the
default.

For the xfs_reclaim_worker(), just call xfs_reclaim_inodes_ag()
directly because we just want optimistic clean inode reclaim to be
done in the background.

For xfs_quiesce_attr() we can just remove the inode reclaim calls as
they are a historic relic that was required to flush dirty inodes
that contained unlogged changes. We now log all changes to the
inodes, so the sync AIL push from xfs_log_quiesce() called by
xfs_quiesce_attr() will do all the required inode writeback for
freeze.

Seeing as we now want to loop until all reclaimable inodes have been
reclaimed, make xfs_reclaim_inodes() loop on the XFS_ICI_RECLAIM_TAG
tag rather than having xfs_reclaim_inodes_ag() tell it that inodes
were skipped. This is much more reliable and will always loop until
all reclaimable inodes are reclaimed.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

All background reclaim is SYNC_TRYLOCK already, and even blocking
reclaim (SYNC_WAIT) can use trylock mechanisms as
xfs_reclaim_inodes_ag() will keep cycling until there are no more
reclaimable inodes. Hence we can kill SYNC_TRYLOCK from inode
reclaim and make everything unconditionally non-blocking.

We remove all the optimistic "avoid blocking on locks" checks done
in xfs_reclaim_inode_grab() as nothing blocks on locks anymore.
Further, checking XFS_IFLOCK optimistically can result in detecting
inodes in the process of being cleaned (i.e. between being removed
from the AIL and having the flush lock dropped), so for
xfs_reclaim_inodes() to reliably reclaim all inodes we need to drop
these checks anyway.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

When we attempt to reclaim an inode, the first thing we do is take
the inode lock. This is blocking right now, so if the inode being
accessed by something else (e.g. being flushed to the cluster
buffer) we will block here.

Change this to a trylock so that we do not block inode reclaim
unnecessarily here.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Inode reclaim will still throttle direct reclaim on the per-ag
reclaim locks. This is no longer necessary as reclaim can run
non-blocking now. Hence we can remove these locks so that we don't
arbitrarily block reclaimers just because there are more direct
reclaimers than there are AGs.

This can result in multiple reclaimers working on the same range of
an AG, but this doesn't cause any apparent issues. Optimising the
spread of concurrent reclaimers for best efficiency can be done in a
future patchset.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

We no longer need to issue IO from shrinker based inode reclaim to
prevent spurious OOM killer invocation. This leaves only the global
filesystem management operations such as unmount needing to
writeback dirty inodes and reclaim them.

Instead of using the reclaim pass to write dirty inodes before
reclaiming them, use the AIL to push all the dirty inodes before we
try to reclaim them. This allows us to remove all the conditional
SYNC_WAIT locking and the writeback code from xfs_reclaim_inode()
and greatly simplify the checks we need to do to reclaim an inode.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Now that dirty inode writeback doesn't cause read-modify-write
cycles on the inode cluster buffer under memory pressure, the need
to throttle memory reclaim to the rate at which we can clean dirty
inodes goes away. That is due to the fact that we no longer thrash
inode cluster buffers under memory pressure to clean dirty inodes.

This means inode writeback no longer stalls on memory allocation
or read IO, and hence can be done asynchronously without generating
memory pressure. As a result, blocking inode writeback in reclaim is
no longer necessary to prevent reclaim priority windup as cleaning
dirty inodes is no longer dependent on having memory reserves
available for the filesystem to make progress reclaiming inodes.

Hence we can convert inode reclaim to be non-blocking for shrinker
callouts, both for direct reclaim and kswapd.

On a vanilla kernel, running a 16-way fsmark create workload on a
4 node/16p/16GB RAM machine, I can reliably pin 14.75GB of RAM via
userspace mlock(). The OOM killer gets invoked at 15GB of
pinned RAM.

Without the inode cluster pinning, this non-blocking reclaim patch
triggers premature OOM killer invocation with the same memory
pinning, sometimes with as much as 45% of RAM being free.  It's
trivially easy to trigger the OOM killer when reclaim does not
block.

With pinning inode clusters in RAM and then adding this patch, I can
reliably pin 14.5GB of RAM and still have the fsmark workload run to
completion. The OOM killer gets invoked 14.75GB of pinned RAM, which
is only a small amount of memory less than the vanilla kernel. It is
much more reliable than just with async reclaim alone.

simoops shows that allocation stalls go away when async reclaim is
used. Vanilla kernel:

Run time: 1924 seconds
Read latency (p50: 3,305,472) (p95: 3,723,264) (p99: 4,001,792)
Write latency (p50: 184,064) (p95: 553,984) (p99: 807,936)
Allocation latency (p50: 2,641,920) (p95: 3,911,680) (p99: 4,464,640)
work rate = 13.45/sec (avg 13.44/sec) (p50: 13.46) (p95: 13.58) (p99: 13.70)
alloc stall rate = 3.80/sec (avg: 2.59) (p50: 2.54) (p95: 2.96) (p99: 3.02)

With inode cluster pinning and async reclaim:

Run time: 1924 seconds
Read latency (p50: 3,305,472) (p95: 3,715,072) (p99: 3,977,216)
Write latency (p50: 187,648) (p95: 553,984) (p99: 789,504)
Allocation latency (p50: 2,748,416) (p95: 3,919,872) (p99: 4,448,256)
work rate = 13.28/sec (avg 13.32/sec) (p50: 13.26) (p95: 13.34) (p99: 13.34)
alloc stall rate = 0.02/sec (avg: 0.02) (p50: 0.01) (p95: 0.03) (p99: 0.03)

Latencies don't really change much, nor does the work rate. However,
allocation almost never stalls with these changes, whilst the
vanilla kernel is sometimes reporting 20 stalls/s over a 60s sample
period. This difference is due to inode reclaim being largely
non-blocking now.

IOWs, once we have pinned inode cluster buffers, we can make inode
reclaim non-blocking without a major risk of premature and/or
spurious OOM killer invocation, and without any changes to memory
reclaim infrastructure.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NAmir Goldstein <amir73il@gmail.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

When we dirty an inode, we are going to have to write it disk at
some point in the near future. This requires the inode cluster
backing buffer to be present in memory. Unfortunately, under severe
memory pressure we can reclaim the inode backing buffer while the
inode is dirty in memory, resulting in stalling the AIL pushing
because it has to do a read-modify-write cycle on the cluster
buffer.

When we have no memory available, the read of the cluster buffer
blocks the AIL pushing process, and this causes all sorts of issues
for memory reclaim as it requires inode writeback to make forwards
progress. Allocating a cluster buffer causes more memory pressure,
and results in more cluster buffers to be reclaimed, resulting in
more RMW cycles to be done in the AIL context and everything then
backs up on AIL progress. Only the synchronous inode cluster
writeback in the the inode reclaim code provides some level of
forwards progress guarantees that prevent OOM-killer rampages in
this situation.

Fix this by pinning the inode backing buffer to the inode log item
when the inode is first dirtied (i.e. in xfs_trans_log_inode()).
This may mean the first modification of an inode that has been held
in cache for a long time may block on a cluster buffer read, but
we can do that in transaction context and block safely until the
buffer has been allocated and read.

Once we have the cluster buffer, the inode log item takes a
reference to it, pinning it in memory, and attaches it to the log
item for future reference. This means we can always grab the cluster
buffer from the inode log item when we need it.

When the inode is finally cleaned and removed from the AIL, we can
drop the reference the inode log item holds on the cluster buffer.
Once all inodes on the cluster buffer are clean, the cluster buffer
will be unpinned and it will be available for memory reclaim to
reclaim again.

This avoids the issues with needing to do RMW cycles in the AIL
pushing context, and hence allows complete non-blocking inode
flushing to be performed by the AIL pushing context.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

xfs_ail_delete_one() is called directly from dquot and inode IO
completion, as well as from the generic xfs_trans_ail_delete()
function. Inodes are about to have their own failure handling, and
dquots will in future, too. Pull the clearing of the LI_FAILED flag
up into the callers so we can customise the code appropriately.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

When an buffer IO error occurs, we want to mark all
the log items attached to the buffer as failed. Open code
the error handling loop so that we can modify the flagging for the
different types of objects directly and independently of each other.

This also allows us to remove the ->iop_error method from the log
item operations.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Currently when a buffer with attached log items has an IO error
it called ->iop_error for each attched log item. These all call
xfs_set_li_failed() to handle the error, but we are about to change
the way log items manage buffers. hence we first need to remove the
per-item dependency on buffer handling done by xfs_set_li_failed().

We already have specific buffer type IO completion routines, so move
the log item error handling out of the generic error handling and
into the log item specific functions so we can implement per-type
error handling easily.

This requires a more complex return value from the error handling
code so that we can take the correct action the failure handling
requires.  This results in some repeated boilerplate in the
functions, but that can be cleaned up later once all the changes
cascade through this code.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

They are not used anymore, so remove them from the log item and the
buffer iodone attachment interfaces.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Now that we've sorted inode and dquot buffers, we can apply the same
cleanups to dirty buffers with buffer log items. They only have one
callback, too, so we don't need the log item callback. Collapse the
iodone functions and remove all the now unnecessary infrastructure
around callback processing.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Similar to inodes, we can call the dquot IO completion functions
directly from the buffer completion code, removing another user of
log item callbacks for IO completion processing.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Having different io completion callbacks for different inode states
makes things complex. We can detect if the inode is stale via the
XFS_ISTALE flag in IO completion, so we don't need a special
callback just for this.

This means inodes only have a single iodone callback, and inode IO
completion is entirely buffer centric at this point. Hence we no
longer need to use a log item callback at all as we can just call
xfs_iflush_done() directly from the buffer completions and walk the
buffer log item list to complete the all inodes under IO.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

When we've emptied the buffer log item list, it does a list_del_init
on itself to reset it's pointers to itself. This is unnecessary as
the list is already empty at this point - it was a left-over
fragment from the list_head conversion of the buffer log item list.
Remove them.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

All unmarked dirty buffers should be in the AIL and have log items
attached to them. Hence when they are written, we will run a
callback to remove the item from the AIL if appropriate. Now that
we've handled inode and dquot buffers, all remaining calls are to
xfs_buf_iodone() and so we can hard code this rather than use an
indirect call.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NAmir Goldstein <amir73il@gmail.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Log recovery has it's own buffer write completion handler for
buffers that it directly recovers. Convert these to direct calls by
flagging these buffers as being log recovery buffers. The flag will
get cleared by the log recovery IO completion routine, so it will
never leak out of log recovery.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

dquot buffers always have write IO callbacks, so by marking them
directly we can avoid needing to attach ->b_iodone functions to
them. This avoids an indirect call, and makes future modifications
much simpler.

This is largely a rearrangement of the code at this point - no IO
completion functionality changes at this point, just how the
code is run is modified.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Inode buffers always have write IO callbacks, so by marking them
directly we can avoid needing to attach ->b_iodone functions to
them. This avoids an indirect call, and makes future modifications
much simpler.

While this is largely a refactor of existing functionality, we
broaden the scope of the flag to beyond where inodes are explicitly
attached because future changes need to know what type of log items
are attached to the buffer. Adding this buffer flag may invoke the
inode iodone callback in cases where it wouldn't have been
previously, but this is not a functional change because the callback
is identical to the normal buffer write iodone callback when inodes
are not attached.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

The inode log item is kind of special in that it can be aggregating
new changes in memory at the same time time existing changes are
being written back to disk. This means there are fields in the log
item that are accessed concurrently from contexts that don't share
any locking at all.

e.g. updating ili_last_fields occurs at flush time under the
ILOCK_EXCL and flush lock at flush time, under the flush lock at IO
completion time, and is read under the ILOCK_EXCL when the inode is
logged.  Hence there is no actual serialisation between reading the
field during logging of the inode in transactions vs clearing the
field in IO completion.

We currently get away with this by the fact that we are only
clearing fields in IO completion, and nothing bad happens if we
accidentally log more of the inode than we actually modify. Worst
case is we consume a tiny bit more memory and log bandwidth.

However, if we want to do more complex state manipulations on the
log item that requires updates at all three of these potential
locations, we need to have some mechanism of serialising those
operations. To do this, introduce a spinlock into the log item to
serialise internal state.

This could be done via the xfs_inode i_flags_lock, but this then
leads to potential lock inversion issues where inode flag updates
need to occur inside locks that best nest inside the inode log item
locks (e.g. marking inodes stale during inode cluster freeing).
Using a separate spinlock avoids these sorts of problems and
simplifies future code.

This does not touch the use of ili_fields in the item formatting
code - that is entirely protected by the ILOCK_EXCL at this point in
time, so it remains untouched.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

This was used to track if the item had logged fields being flushed
to disk. We log everything in the inode these days, so this logic is
no longer needed. Remove it.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

In tracking down a problem in this patchset, I discovered we are
reclaiming dirty stale inodes. This wasn't discovered until inodes
were always attached to the cluster buffer and then the rcu callback
that freed inodes was assert failing because the inode still had an
active pointer to the cluster buffer after it had been reclaimed.

Debugging the issue indicated that this was a pre-existing issue
resulting from the way the inodes are handled in xfs_inactive_ifree.
When we free a cluster buffer from xfs_ifree_cluster, all the inodes
in cache are marked XFS_ISTALE. Those that are clean have nothing
else done to them and so eventually get cleaned up by background
reclaim. i.e. it is assumed we'll never dirty/relog an inode marked
XFS_ISTALE.

On journal commit dirty stale inodes as are handled by both
buffer and inode log items to run though xfs_istale_done() and
removed from the AIL (buffer log item commit) or the log item will
simply unpin it because the buffer log item will clean it. What happens
to any specific inode is entirely dependent on which log item wins
the commit race, but the result is the same - stale inodes are
clean, not attached to the cluster buffer, and not in the AIL. Hence
inode reclaim can just free these inodes without further care.

However, if the stale inode is relogged, it gets dirtied again and
relogged into the CIL. Most of the time this isn't an issue, because
relogging simply changes the inode's location in the current
checkpoint. Problems arise, however, when the CIL checkpoints
between two transactions in the xfs_inactive_ifree() deferops
processing. This results in the XFS_ISTALE inode being redirtied
and inserted into the CIL without any of the other stale cluster
buffer infrastructure being in place.

Hence on journal commit, it simply gets unpinned, so it remains
dirty in memory. Everything in inode writeback avoids XFS_ISTALE
inodes so it can't be written back, and it is not tracked in the AIL
so there's not even a trigger to attempt to clean the inode. Hence
the inode just sits dirty in memory until inode reclaim comes along,
sees that it is XFS_ISTALE, and goes to reclaim it. This reclaiming
of a dirty inode caused use after free, list corruptions and other
nasty issues later in this patchset.

Hence this patch addresses a violation of the "never log XFS_ISTALE
inodes" caused by the deferops processing rolling a transaction
and relogging a stale inode in xfs_inactive_free. It also adds a
bunch of asserts to catch this problem in debug kernels so that
we don't reintroduce this problem in future.

Reproducer for this issue was generic/558 on a v4 filesystem.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>