KASAN reported the following use after free bug when running
generic/475:
XFS (dm-0): Mounting V5 Filesystem
XFS (dm-0): Starting recovery (logdev: internal)
XFS (dm-0): Ending recovery (logdev: internal)
Buffer I/O error on dev dm-0, logical block 20639616, async page read
Buffer I/O error on dev dm-0, logical block 20639617, async page read
XFS (dm-0): log I/O error -5
XFS (dm-0): Filesystem has been shut down due to log error (0x2).
XFS (dm-0): Unmounting Filesystem
XFS (dm-0): Please unmount the filesystem and rectify the problem(s).
==================================================================
BUG: KASAN: use-after-free in do_raw_spin_lock+0x246/0x270
Read of size 4 at addr ffff888109dd84c4 by task 3:1H/136
CPU: 3 PID: 136 Comm: 3:1H Not tainted 5.19.0-rc4-xfsx #rc4 8e53ab5ad0fddeb31cee5e7063ff9c361915a9c4
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
Workqueue: xfs-log/dm-0 xlog_ioend_work [xfs]
Call Trace:
<TASK>
dump_stack_lvl+0x34/0x44
print_report.cold+0x2b8/0x661
? do_raw_spin_lock+0x246/0x270
kasan_report+0xab/0x120
? do_raw_spin_lock+0x246/0x270
do_raw_spin_lock+0x246/0x270
? rwlock_bug.part.0+0x90/0x90
xlog_force_shutdown+0xf6/0x370 [xfs 4ad76ae0d6add7e8183a553e624c31e9ed567318]
xlog_ioend_work+0x100/0x190 [xfs 4ad76ae0d6add7e8183a553e624c31e9ed567318]
process_one_work+0x672/0x1040
worker_thread+0x59b/0xec0
? __kthread_parkme+0xc6/0x1f0
? process_one_work+0x1040/0x1040
? process_one_work+0x1040/0x1040
kthread+0x29e/0x340
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x1f/0x30
</TASK>
Allocated by task 154099:
kasan_save_stack+0x1e/0x40
__kasan_kmalloc+0x81/0xa0
kmem_alloc+0x8d/0x2e0 [xfs]
xlog_cil_init+0x1f/0x540 [xfs]
xlog_alloc_log+0xd1e/0x1260 [xfs]
xfs_log_mount+0xba/0x640 [xfs]
xfs_mountfs+0xf2b/0x1d00 [xfs]
xfs_fs_fill_super+0x10af/0x1910 [xfs]
get_tree_bdev+0x383/0x670
vfs_get_tree+0x7d/0x240
path_mount+0xdb7/0x1890
__x64_sys_mount+0x1fa/0x270
do_syscall_64+0x2b/0x80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
Freed by task 154151:
kasan_save_stack+0x1e/0x40
kasan_set_track+0x21/0x30
kasan_set_free_info+0x20/0x30
____kasan_slab_free+0x110/0x190
slab_free_freelist_hook+0xab/0x180
kfree+0xbc/0x310
xlog_dealloc_log+0x1b/0x2b0 [xfs]
xfs_unmountfs+0x119/0x200 [xfs]
xfs_fs_put_super+0x6e/0x2e0 [xfs]
generic_shutdown_super+0x12b/0x3a0
kill_block_super+0x95/0xd0
deactivate_locked_super+0x80/0x130
cleanup_mnt+0x329/0x4d0
task_work_run+0xc5/0x160
exit_to_user_mode_prepare+0xd4/0xe0
syscall_exit_to_user_mode+0x1d/0x40
entry_SYSCALL_64_after_hwframe+0x46/0xb0
This appears to be a race between the unmount process, which frees the
CIL and waits for in-flight iclog IO; and the iclog IO completion. When
generic/475 runs, it starts fsstress in the background, waits a few
seconds, and substitutes a dm-error device to simulate a disk falling
out of a machine. If the fsstress encounters EIO on a pure data write,
it will exit but the filesystem will still be online.
The next thing the test does is unmount the filesystem, which tries to
clean the log, free the CIL, and wait for iclog IO completion. If an
iclog was being written when the dm-error switch occurred, it can race
with log unmounting as follows:
Thread 1 Thread 2
xfs_log_unmount
xfs_log_clean
xfs_log_quiesce
xlog_ioend_work
<observe error>
xlog_force_shutdown
test_and_set_bit(XLOG_IOERROR)
xfs_log_force
<log is shut down, nop>
xfs_log_umount_write
<log is shut down, nop>
xlog_dealloc_log
xlog_cil_destroy
<wait for iclogs>
spin_lock(&log->l_cilp->xc_push_lock)
<KABOOM>
Therefore, free the CIL after waiting for the iclogs to complete. I
/think/ this race has existed for quite a few years now, though I don't
remember the ~2014 era logging code well enough to know if it was a real
threat then or if the actual race was exposed only more recently.
Fixes: ac983517ec ("xfs: don't sleep in xlog_cil_force_lsn on shutdown")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
The LARP patchset added an awkward coupling point between libxfs and
what would be libxlog, if the XFS log were actually its own library.
Move the code that enables logged xattr updates out of "lib"xlog and into
xfs_xattr.c so that it no longer has to know about xlog_* functions.
While we're at it, give xfs_xattr.c its own header file.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Since LARP is an experimental debug-only feature, we should try to warn
about it being in use once per mount, not once per reboot.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
These routines set up and queue a new deferred attribute operations.
These functions are meant to be called by any routine needing to
initiate a deferred attribute operation as opposed to the existing
inline operations. New helper function xfs_attr_item_init also added.
Finally enable delayed attributes in xfs_attr_set and xfs_attr_remove.
Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
5.18 w/ std=gnu11 compiled with gcc-5 wants flags stored in unsigned
fields to be unsigned.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
So remove it from the interface and callers.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
The rework of xlog_write() no longer requires xlog_get_iclog_state()
to tell it about internal iclog space reservation state to direct it
on what to do. Remove this parameter.
$ size fs/xfs/xfs_log.o.*
text data bss dec hex filename
26520 560 8 27088 69d0 fs/xfs/xfs_log.o.orig
26384 560 8 26952 6948 fs/xfs/xfs_log.o.patched
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Just check that the offset in xlog_write_vec is smaller than the iclog
size and remove the expensive cycling through all iclogs.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Re-implement writing of a log vector that does not fit into the
current iclog. The iclog will already be in XLOG_STATE_WANT_SYNC
because xlog_get_iclog_space() will have reserved all the remaining
iclog space for us, hence we can simply iterate over the iovecs in
the log vector getting more iclog space until the entire log vector
is written.
Handling this partial write case separately means we do need to pass
unnecessary state around for the common, fast path case when the log
vector fits entirely within the current iclog. It isolates the
complexity and allows us to modify and improve the partial write
case without impacting the simple fast path.
This change includes several improvements incorporated from patches
written by Christoph Hellwig.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Introduce an optimised version of xlog_write() that is used when the
entire write will fit in a single iclog. This greatly simplifies the
implementation of writing a log vector chain into an iclog, and sets
the ground work for a much more understandable xlog_write()
implementation.
This incorporates some factoring and simplifications proposed by
Christoph Hellwig.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Turn ic_datap from a char into a void pointer given that it points
to arbitrary data.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[dgc: also remove (char *) cast in xlog_alloc_log()]
Signed-off-by: Dave Chinner <david@fromorbit.com>
The caller of xlog_write() usually has a close accounting of the
aggregated vector length contained in the log vector chain passed to
xlog_write(). There is no need to iterate the chain to calculate he
length of the data in xlog_write_calculate_len() if the caller is
already iterating that chain to build it.
Passing in the vector length avoids doing an extra chain iteration,
which can be a significant amount of work given that large CIL
commits can have hundreds of thousands of vectors attached to the
chain.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
xlog_tic_add_region() is used to trace the regions being added to a
log ticket to provide information in the situation where a ticket
reservation overrun occurs. The information gathered is stored int
the ticket, and dumped if xlog_print_tic_res() is called.
For a front end struct xfs_trans overrun, the ticket only contains
reservation tracking information - the ticket is never handed to the
log so has no regions attached to it. The overrun debug information in this
case comes from xlog_print_trans(), which walks the items attached
to the transaction and dumps their attached formatted log vectors
directly. It also dumps the ticket state, but that only contains
reservation accounting and nothing else. Hence xlog_print_tic_res()
never dumps region or overrun information from this path.
xlog_tic_add_region() is actually called from xlog_write(), which
means it is being used to track the regions seen in a
CIL checkpoint log vector chain. In looking at CIL behaviour
recently, I've seen 32MB checkpoints regularly exceed 250,000
regions in the LV chain. The log ticket debug code can track *15*
regions. IOWs, if there is a ticket overrun in the CIL code, the
ticket region tracking code is going to be completely useless for
determining what went wrong. The only thing it can tell us is how
much of an overrun occurred, and we really don't need extra debug
information in the log ticket to tell us that.
Indeed, the main place we call xlog_tic_add_region() is also adding
up the number of regions and the space used so that xlog_write()
knows how much will be written to the log. This is exactly the same
information that log ticket is storing once we take away the useless
region tracking array. Hence xlog_tic_add_region() is not useful,
but can be called 250,000 times a CIL push...
Just strip all that debug "information" out of the of the log ticket
and only have it report reservation space information when an
overrun occurs. This also reduces the size of a log ticket down by
about 150 bytes...
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Current xlog_write() adds op headers to the log manually for every
log item region that is in the vector passed to it. While
xlog_write() needs to stamp the transaction ID into the ophdr, we
already know it's length, flags, clientid, etc at CIL commit time.
This means the only time that xlog write really needs to format and
reserve space for a new ophdr is when a region is split across two
iclogs. Adding the opheader and accounting for it as part of the
normal formatted item region means we simplify the accounting
of space used by a transaction and we don't have to special case
reserving of space in for the ophdrs in xlog_write(). It also means
we can largely initialise the ophdr in transaction commit instead
of xlog_write, making the xlog_write formatting inner loop much
tighter.
xlog_prepare_iovec() is now too large to stay as an inline function,
so we move it out of line and into xfs_log.c.
Object sizes:
text data bss dec hex filename
1125934 305951 484 1432369 15db31 fs/xfs/built-in.a.before
1123360 305951 484 1429795 15d123 fs/xfs/built-in.a.after
So the code is a roughly 2.5kB smaller with xlog_prepare_iovec() now
out of line, even though it grew in size itself.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
We currently set the log ticket client ID when we reserve a
transaction. This client ID is only ever written to the log by
a CIL checkpoint or unmount records, and so anything using a high
level transaction allocated through xfs_trans_alloc() does not need
a log ticket client ID to be set.
For the CIL checkpoint, the client ID written to the journal is
always XFS_TRANSACTION, and for the unmount record it is always
XFS_LOG, and nothing else writes to the log. All of these operations
tell xlog_write() exactly what they need to write to the log (the
optype) and build their own opheaders for start, commit and unmount
records. Hence we no longer need to set the client id in either the
log ticket or the xfs_trans.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Remove the final case where xlog_write() has to prepend an opheader
to a log transaction. Similar to the start record, the commit record
is just an empty opheader with a XLOG_COMMIT_TRANS type, so we can
just make this the payload for the region being passed to
xlog_write() and remove the special handling in xlog_write() for
the commit record.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Remove another case where xlog_write() has to prepend an opheader to
a log transaction. The unmount record + ophdr is smaller than the
minimum amount of space guaranteed to be free in an iclog (2 *
sizeof(ophdr)) and so we don't have to care about an unmount record
being split across 2 iclogs.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
So move the one-off start record writing in xlog_write() out into
the static header that the CIL push builds to write into the log
initially. This simplifes the xlog_write() logic a lot.
pahole on x86-64 confirms that the xlog_cil_trans_hdr is correctly
32 bit aligned and packed for copying the log op and transaction
headers directly into the log as a single log region copy.
struct xlog_cil_trans_hdr {
struct xlog_op_header oph[2]; /* 0 24 */
struct xfs_trans_header thdr; /* 24 16 */
struct xfs_log_iovec lhdr[2]; /* 40 32 */
/* size: 72, cachelines: 2, members: 3 */
/* last cacheline: 8 bytes */
};
A wart is needed to handle the fact that length of the region the
opheader points to doesn't include the opheader length. hence if
we embed the opheader, we have to substract the opheader length from
the length written into the opheader by the generic copying code.
This will eventually go away when everything is converted to
embedded opheaders.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
- Fix an incorrect free space calculation in xfs_reserve_blocks that
could lead to a request for free blocks that will never succeed.
- Fix a hang in xfs_reserve_blocks caused by an infinite loop and the
incorrect free space calculation.
- Fix yet a third problem in xfs_reserve_blocks where multiple racing
threads can overfill the reserve pool.
- Fix an accounting error that lead to us reporting reserved space as
"available".
- Fix a race condition during abnormal fs shutdown that could cause UAF
problems when memory reclaim and log shutdown try to clean up inodes.
- Fix a bug where log shutdown can race with unmount to tear down the
log, thereby causing UAF errors.
- Disentangle log and filesystem shutdown to reduce confusion.
- Fix some confusion in xfs_trans_commit such that a race between
transaction commit and filesystem shutdown can cause unlogged dirty
inode metadata to be committed, thereby corrupting the filesystem.
- Remove a performance optimization in the log as it was discovered that
certain storage hardware handle async log flushes so poorly as to
cause serious performance regressions. Recent restructuring of other
parts of the logging code mean that no performance benefit is seen on
hardware that handle it well.
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Merge tag 'xfs-5.18-merge-4' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux
Pull xfs fixes from Darrick Wong:
"This fixes multiple problems in the reserve pool sizing functions: an
incorrect free space calculation, a pointless infinite loop, and even
more braindamage that could result in the pool being overfilled. The
pile of patches from Dave fix myriad races and UAF bugs in the log
recovery code that much to our mutual surprise nobody's tripped over.
Dave also fixed a performance optimization that had turned into a
regression.
Dave Chinner is taking over as XFS maintainer starting Sunday and
lasting until 5.19-rc1 is tagged so that I can focus on starting a
massive design review for the (feature complete after five years)
online repair feature. From then on, he and I will be moving XFS to a
co-maintainership model by trading duties every other release.
NOTE: I hope very strongly that the other pieces of the (X)FS
ecosystem (fstests and xfsprogs) will make similar changes to spread
their maintenance load.
Summary:
- Fix an incorrect free space calculation in xfs_reserve_blocks that
could lead to a request for free blocks that will never succeed.
- Fix a hang in xfs_reserve_blocks caused by an infinite loop and the
incorrect free space calculation.
- Fix yet a third problem in xfs_reserve_blocks where multiple racing
threads can overfill the reserve pool.
- Fix an accounting error that lead to us reporting reserved space as
"available".
- Fix a race condition during abnormal fs shutdown that could cause
UAF problems when memory reclaim and log shutdown try to clean up
inodes.
- Fix a bug where log shutdown can race with unmount to tear down the
log, thereby causing UAF errors.
- Disentangle log and filesystem shutdown to reduce confusion.
- Fix some confusion in xfs_trans_commit such that a race between
transaction commit and filesystem shutdown can cause unlogged dirty
inode metadata to be committed, thereby corrupting the filesystem.
- Remove a performance optimization in the log as it was discovered
that certain storage hardware handle async log flushes so poorly as
to cause serious performance regressions. Recent restructuring of
other parts of the logging code mean that no performance benefit is
seen on hardware that handle it well"
* tag 'xfs-5.18-merge-4' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
xfs: drop async cache flushes from CIL commits.
xfs: shutdown during log recovery needs to mark the log shutdown
xfs: xfs_trans_commit() path must check for log shutdown
xfs: xfs_do_force_shutdown needs to block racing shutdowns
xfs: log shutdown triggers should only shut down the log
xfs: run callbacks before waking waiters in xlog_state_shutdown_callbacks
xfs: shutdown in intent recovery has non-intent items in the AIL
xfs: aborting inodes on shutdown may need buffer lock
xfs: don't report reserved bnobt space as available
xfs: fix overfilling of reserve pool
xfs: always succeed at setting the reserve pool size
xfs: remove infinite loop when reserving free block pool
xfs: don't include bnobt blocks when reserving free block pool
xfs: document the XFS_ALLOC_AGFL_RESERVE constant
Jan Kara reported a performance regression in dbench that he
bisected down to commit bad77c375e ("xfs: CIL checkpoint
flushes caches unconditionally").
Whilst developing the journal flush/fua optimisations this cache was
part of, it appeared to made a significant difference to
performance. However, now that this patchset has settled and all the
correctness issues fixed, there does not appear to be any
significant performance benefit to asynchronous cache flushes.
In fact, the opposite is true on some storage types and workloads,
where additional cache flushes that can occur from fsync heavy
workloads have measurable and significant impact on overall
throughput.
Local dbench testing shows little difference on dbench runs with
sync vs async cache flushes on either fast or slow SSD storage, and
no difference in streaming concurrent async transaction workloads
like fs-mark.
Fast NVME storage.
From `dbench -t 30`, CIL scale:
clients async sync
BW Latency BW Latency
1 935.18 0.855 915.64 0.903
8 2404.51 6.873 2341.77 6.511
16 3003.42 6.460 2931.57 6.529
32 3697.23 7.939 3596.28 7.894
128 7237.43 15.495 7217.74 11.588
512 5079.24 90.587 5167.08 95.822
fsmark, 32 threads, create w/ 64 byte xattr w/32k logbsize
create chown unlink
async 1m41s 1m16s 2m03s
sync 1m40s 1m19s 1m54s
Slower SATA SSD storage:
From `dbench -t 30`, CIL scale:
clients async sync
BW Latency BW Latency
1 78.59 15.792 83.78 10.729
8 367.88 92.067 404.63 59.943
16 564.51 72.524 602.71 76.089
32 831.66 105.984 870.26 110.482
128 1659.76 102.969 1624.73 91.356
512 2135.91 223.054 2603.07 161.160
fsmark, 16 threads, create w/32k logbsize
create unlink
async 5m06s 4m15s
sync 5m00s 4m22s
And on Jan's test machine:
5.18-rc8-vanilla 5.18-rc8-patched
Amean 1 71.22 ( 0.00%) 64.94 * 8.81%*
Amean 2 93.03 ( 0.00%) 84.80 * 8.85%*
Amean 4 150.54 ( 0.00%) 137.51 * 8.66%*
Amean 8 252.53 ( 0.00%) 242.24 * 4.08%*
Amean 16 454.13 ( 0.00%) 439.08 * 3.31%*
Amean 32 835.24 ( 0.00%) 829.74 * 0.66%*
Amean 64 1740.59 ( 0.00%) 1686.73 * 3.09%*
Performance and cache flush behaviour is restored to pre-regression
levels.
As such, we can now consider the async cache flush mechanism an
unnecessary exercise in premature optimisation and hence we can
now remove it and the infrastructure it requires completely.
Fixes: bad77c375e ("xfs: CIL checkpoint flushes caches unconditionally")
Reported-and-tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
When a checkpoint writeback is run by log recovery, corruption
propagated from the log can result in writeback verifiers failing
and calling xfs_force_shutdown() from
xfs_buf_delwri_submit_buffers().
This results in the mount being marked as shutdown, but the log does
not get marked as shut down because:
/*
* If this happens during log recovery then we aren't using the runtime
* log mechanisms yet so there's nothing to shut down.
*/
if (!log || xlog_in_recovery(log))
return false;
If there are other buffers that then fail (say due to detecting the
mount shutdown), they will now hang in xfs_do_force_shutdown()
waiting for the log to shut down like this:
__schedule+0x30d/0x9e0
schedule+0x55/0xd0
xfs_do_force_shutdown+0x1cd/0x200
? init_wait_var_entry+0x50/0x50
xfs_buf_ioend+0x47e/0x530
__xfs_buf_submit+0xb0/0x240
xfs_buf_delwri_submit_buffers+0xfe/0x270
xfs_buf_delwri_submit+0x3a/0xc0
xlog_do_recovery_pass+0x474/0x7b0
? do_raw_spin_unlock+0x30/0xb0
xlog_do_log_recovery+0x91/0x140
xlog_do_recover+0x38/0x1e0
xlog_recover+0xdd/0x170
xfs_log_mount+0x17e/0x2e0
xfs_mountfs+0x457/0x930
xfs_fs_fill_super+0x476/0x830
xlog_force_shutdown() always needs to mark the log as shut down,
regardless of whether recovery is in progress or not, so that
multiple calls to xfs_force_shutdown() during recovery don't end
up waiting for the log to be shut down like this.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
When we call xfs_forced_shutdown(), the caller often expects the
filesystem to be completely shut down when it returns. However,
if we have racing xfs_forced_shutdown() calls, the first caller sets
the mount shutdown flag then goes to shutdown the log. The second
caller sees the mount shutdown flag and returns immediately - it
does not wait for the log to be shut down.
Unfortunately, xfs_forced_shutdown() is used in some places that
expect it to completely shut down the filesystem before it returns
(e.g. xfs_trans_log_inode()). As such, returning before the log has
been shut down leaves us in a place where the transaction failed to
complete correctly but we still call xfs_trans_commit(). This
situation arises because xfs_trans_log_inode() does not return an
error and instead calls xfs_force_shutdown() to ensure that the
transaction being committed is aborted.
Unfortunately, we have a race condition where xfs_trans_commit()
needs to check xlog_is_shutdown() because it can't abort log items
before the log is shut down, but it needs to use xfs_is_shutdown()
because xfs_forced_shutdown() does not block waiting for the log to
shut down.
To fix this conundrum, first we make all calls to
xfs_forced_shutdown() block until the log is also shut down. This
means we can then safely use xfs_forced_shutdown() as a mechanism
that ensures the currently running transaction will be aborted by
xfs_trans_commit() regardless of the shutdown check it uses.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
We've got a mess on our hands.
1. xfs_trans_commit() cannot cancel transactions because the mount is
shut down - that causes dirty, aborted, unlogged log items to sit
unpinned in memory and potentially get written to disk before the
log is shut down. Hence xfs_trans_commit() can only abort
transactions when xlog_is_shutdown() is true.
2. xfs_force_shutdown() is used in places to cause the current
modification to be aborted via xfs_trans_commit() because it may be
impractical or impossible to cancel the transaction directly, and
hence xfs_trans_commit() must cancel transactions when
xfs_is_shutdown() is true in this situation. But we can't do that
because of #1.
3. Log IO errors cause log shutdowns by calling xfs_force_shutdown()
to shut down the mount and then the log from log IO completion.
4. xfs_force_shutdown() can result in a log force being issued,
which has to wait for log IO completion before it will mark the log
as shut down. If #3 races with some other shutdown trigger that runs
a log force, we rely on xfs_force_shutdown() silently ignoring #3
and avoiding shutting down the log until the failed log force
completes.
5. To ensure #2 always works, we have to ensure that
xfs_force_shutdown() does not return until the the log is shut down.
But in the case of #4, this will result in a deadlock because the
log Io completion will block waiting for a log force to complete
which is blocked waiting for log IO to complete....
So the very first thing we have to do here to untangle this mess is
dissociate log shutdown triggers from mount shutdowns. We already
have xlog_forced_shutdown, which will atomically transistion to the
log a shutdown state. Due to internal asserts it cannot be called
multiple times, but was done simply because the only place that
could call it was xfs_do_force_shutdown() (i.e. the mount shutdown!)
and that could only call it once and once only. So the first thing
we do is remove the asserts.
We then convert all the internal log shutdown triggers to call
xlog_force_shutdown() directly instead of xfs_force_shutdown(). This
allows the log shutdown triggers to shut down the log without
needing to care about mount based shutdown constraints. This means
we shut down the log independently of the mount and the mount may
not notice this until it's next attempt to read or modify metadata.
At that point (e.g. xfs_trans_commit()) it will see that the log is
shutdown, error out and shutdown the mount.
To ensure that all the unmount behaviours and asserts track
correctly as a result of a log shutdown, propagate the shutdown up
to the mount if it is not already set. This keeps the mount and log
state in sync, and saves a huge amount of hassle where code fails
because of a log shutdown but only checks for mount shutdowns and
hence ends up doing the wrong thing. Cleaning up that mess is
an exercise for another day.
This enables us to address the other problems noted above in
followup patches.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Brian reported a null pointer dereference failure during unmount in
xfs/006. He tracked the problem down to the AIL being torn down
before a log shutdown had completed and removed all the items from
the AIL. The failure occurred in this path while unmount was
proceeding in another task:
xfs_trans_ail_delete+0x102/0x130 [xfs]
xfs_buf_item_done+0x22/0x30 [xfs]
xfs_buf_ioend+0x73/0x4d0 [xfs]
xfs_trans_committed_bulk+0x17e/0x2f0 [xfs]
xlog_cil_committed+0x2a9/0x300 [xfs]
xlog_cil_process_committed+0x69/0x80 [xfs]
xlog_state_shutdown_callbacks+0xce/0xf0 [xfs]
xlog_force_shutdown+0xdf/0x150 [xfs]
xfs_do_force_shutdown+0x5f/0x150 [xfs]
xlog_ioend_work+0x71/0x80 [xfs]
process_one_work+0x1c5/0x390
worker_thread+0x30/0x350
kthread+0xd7/0x100
ret_from_fork+0x1f/0x30
This is processing an EIO error to a log write, and it's
triggering a force shutdown. This causes the log to be shut down,
and then it is running attached iclog callbacks from the shutdown
context. That means the fs and log has already been marked as
xfs_is_shutdown/xlog_is_shutdown and so high level code will abort
(e.g. xfs_trans_commit(), xfs_log_force(), etc) with an error
because of shutdown.
The umount would have been blocked waiting for a log force
completion inside xfs_log_cover() -> xfs_sync_sb(). The first thing
for this situation to occur is for xfs_sync_sb() to exit without
waiting for the iclog buffer to be comitted to disk. The
above trace is the completion routine for the iclog buffer, and
it is shutting down the filesystem.
xlog_state_shutdown_callbacks() does this:
{
struct xlog_in_core *iclog;
LIST_HEAD(cb_list);
spin_lock(&log->l_icloglock);
iclog = log->l_iclog;
do {
if (atomic_read(&iclog->ic_refcnt)) {
/* Reference holder will re-run iclog callbacks. */
continue;
}
list_splice_init(&iclog->ic_callbacks, &cb_list);
>>>>>> wake_up_all(&iclog->ic_write_wait);
>>>>>> wake_up_all(&iclog->ic_force_wait);
} while ((iclog = iclog->ic_next) != log->l_iclog);
wake_up_all(&log->l_flush_wait);
spin_unlock(&log->l_icloglock);
>>>>>> xlog_cil_process_committed(&cb_list);
}
This wakes any thread waiting on IO completion of the iclog (in this
case the umount log force) before shutdown processes all the pending
callbacks. That means the xfs_sync_sb() waiting on a sync
transaction in xfs_log_force() on iclog->ic_force_wait will get
woken before the callbacks attached to that iclog are run. This
results in xfs_sync_sb() returning an error, and so unmount unblocks
and continues to run whilst the log shutdown is still in progress.
Normally this is just fine because the force waiter has nothing to
do with AIL operations. But in the case of this unmount path, the
log force waiter goes on to tear down the AIL because the log is now
shut down and so nothing ever blocks it again from the wait point in
xfs_log_cover().
Hence it's a race to see who gets to the AIL first - the unmount
code or xlog_cil_process_committed() killing the superblock buffer.
To fix this, we just have to change the order of processing in
xlog_state_shutdown_callbacks() to run the callbacks before it wakes
any task waiting on completion of the iclog.
Reported-by: Brian Foster <bfoster@redhat.com>
Fixes: aad7272a92 ("xfs: separate out log shutdown callback processing")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
- Fix some incorrect mapping state being passed to iomap during COW
- Don't create bogus selinux audit messages when deciding to degrade
gracefully due to lack of privilege
- Fix setattr implementation to use VFS helpers so that we drop setgid
consistently with the other filesystems
- Fix link/unlink/rename to check quota limits
- Constify xfs_name_dotdot to prevent abuse of in-kernel symbols
- Fix log livelock between the AIL and inodegc threads during recovery
- Fix a log stall when the AIL races with pushers
- Fix stalls in CIL flushes due to pinned inode cluster buffers during
recovery
- Fix log corruption due to incorrect usage of xfs_is_shutdown vs
xlog_is_shutdown because during an induced fs shutdown, AIL writeback
must continue until the log is shut down, even if the filesystem has
already shut down
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Merge tag 'xfs-5.18-merge-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux
Pull xfs updates from Darrick Wong:
"The biggest change this cycle is bringing XFS' inode attribute setting
code back towards alignment with what the VFS does. IOWs, setgid bit
handling should be a closer match with ext4 and btrfs behavior.
The rest of the branch is bug fixes around the filesystem -- patching
gaps in quota enforcement, removing bogus selinux audit messages, and
fixing log corruption and problems with log recovery. There will be a
second pull request later on in the merge window with more bug fixes.
Dave Chinner will be taking over as XFS maintainer for one release
cycle, starting from the day 5.18-rc1 drops until 5.19-rc1 is tagged
so that I can focus on starting a massive design review for the
(feature complete after five years) online repair feature.
Summary:
- Fix some incorrect mapping state being passed to iomap during COW
- Don't create bogus selinux audit messages when deciding to degrade
gracefully due to lack of privilege
- Fix setattr implementation to use VFS helpers so that we drop
setgid consistently with the other filesystems
- Fix link/unlink/rename to check quota limits
- Constify xfs_name_dotdot to prevent abuse of in-kernel symbols
- Fix log livelock between the AIL and inodegc threads during
recovery
- Fix a log stall when the AIL races with pushers
- Fix stalls in CIL flushes due to pinned inode cluster buffers
during recovery
- Fix log corruption due to incorrect usage of xfs_is_shutdown vs
xlog_is_shutdown because during an induced fs shutdown, AIL
writeback must continue until the log is shut down, even if the
filesystem has already shut down"
* tag 'xfs-5.18-merge-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
xfs: xfs_is_shutdown vs xlog_is_shutdown cage fight
xfs: AIL should be log centric
xfs: log items should have a xlog pointer, not a mount
xfs: async CIL flushes need pending pushes to be made stable
xfs: xfs_ail_push_all_sync() stalls when racing with updates
xfs: check buffer pin state after locking in delwri_submit
xfs: log worker needs to start before intent/unlink recovery
xfs: constify xfs_name_dotdot
xfs: constify the name argument to various directory functions
xfs: reserve quota for target dir expansion when renaming files
xfs: reserve quota for dir expansion when linking/unlinking files
xfs: refactor user/group quota chown in xfs_setattr_nonsize
xfs: use setattr_copy to set vfs inode attributes
xfs: don't generate selinux audit messages for capability testing
xfs: add missing cmap->br_state = XFS_EXT_NORM update
Log items belong to the log, not the xfs_mount. Convert the mount
pointer in the log item to a xlog pointer in preparation for
upcoming log centric changes to the log items.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
After 963 iterations of generic/530, it deadlocked during recovery
on a pinned inode cluster buffer like so:
XFS (pmem1): Starting recovery (logdev: internal)
INFO: task kworker/8:0:306037 blocked for more than 122 seconds.
Not tainted 5.17.0-rc6-dgc+ #975
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/8:0 state:D stack:13024 pid:306037 ppid: 2 flags:0x00004000
Workqueue: xfs-inodegc/pmem1 xfs_inodegc_worker
Call Trace:
<TASK>
__schedule+0x30d/0x9e0
schedule+0x55/0xd0
schedule_timeout+0x114/0x160
__down+0x99/0xf0
down+0x5e/0x70
xfs_buf_lock+0x36/0xf0
xfs_buf_find+0x418/0x850
xfs_buf_get_map+0x47/0x380
xfs_buf_read_map+0x54/0x240
xfs_trans_read_buf_map+0x1bd/0x490
xfs_imap_to_bp+0x4f/0x70
xfs_iunlink_map_ino+0x66/0xd0
xfs_iunlink_map_prev.constprop.0+0x148/0x2f0
xfs_iunlink_remove_inode+0xf2/0x1d0
xfs_inactive_ifree+0x1a3/0x900
xfs_inode_unlink+0xcc/0x210
xfs_inodegc_worker+0x1ac/0x2f0
process_one_work+0x1ac/0x390
worker_thread+0x56/0x3c0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
</TASK>
task:mount state:D stack:13248 pid:324509 ppid:324233 flags:0x00004000
Call Trace:
<TASK>
__schedule+0x30d/0x9e0
schedule+0x55/0xd0
schedule_timeout+0x114/0x160
__down+0x99/0xf0
down+0x5e/0x70
xfs_buf_lock+0x36/0xf0
xfs_buf_find+0x418/0x850
xfs_buf_get_map+0x47/0x380
xfs_buf_read_map+0x54/0x240
xfs_trans_read_buf_map+0x1bd/0x490
xfs_imap_to_bp+0x4f/0x70
xfs_iget+0x300/0xb40
xlog_recover_process_one_iunlink+0x4c/0x170
xlog_recover_process_iunlinks.isra.0+0xee/0x130
xlog_recover_finish+0x57/0x110
xfs_log_mount_finish+0xfc/0x1e0
xfs_mountfs+0x540/0x910
xfs_fs_fill_super+0x495/0x850
get_tree_bdev+0x171/0x270
xfs_fs_get_tree+0x15/0x20
vfs_get_tree+0x24/0xc0
path_mount+0x304/0xba0
__x64_sys_mount+0x108/0x140
do_syscall_64+0x35/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
</TASK>
task:xfsaild/pmem1 state:D stack:14544 pid:324525 ppid: 2 flags:0x00004000
Call Trace:
<TASK>
__schedule+0x30d/0x9e0
schedule+0x55/0xd0
io_schedule+0x4b/0x80
xfs_buf_wait_unpin+0x9e/0xf0
__xfs_buf_submit+0x14a/0x230
xfs_buf_delwri_submit_buffers+0x107/0x280
xfs_buf_delwri_submit_nowait+0x10/0x20
xfsaild+0x27e/0x9d0
kthread+0xf6/0x120
ret_from_fork+0x1f/0x30
We have the mount process waiting on an inode cluster buffer read,
inodegc doing unlink waiting on the same inode cluster buffer, and
the AIL push thread blocked in writeback waiting for the inode
cluster buffer to become unpinned.
What has happened here is that the AIL push thread has raced with
the inodegc process modifying, committing and pinning the inode
cluster buffer here in xfs_buf_delwri_submit_buffers() here:
blk_start_plug(&plug);
list_for_each_entry_safe(bp, n, buffer_list, b_list) {
if (!wait_list) {
if (xfs_buf_ispinned(bp)) {
pinned++;
continue;
}
Here >>>>>>
if (!xfs_buf_trylock(bp))
continue;
Basically, the AIL has found the buffer wasn't pinned and got the
lock without blocking, but then the buffer was pinned. This implies
the processing here was pre-empted between the pin check and the
lock, because the pin count can only be increased while holding the
buffer locked. Hence when it has gone to submit the IO, it has
blocked waiting for the buffer to be unpinned.
With all executing threads now waiting on the buffer to be unpinned,
we normally get out of situations like this via the background log
worker issuing a log force which will unpinned stuck buffers like
this. But at this point in recovery, we haven't started the log
worker. In fact, the first thing we do after processing intents and
unlinked inodes is *start the log worker*. IOWs, we start it too
late to have it break deadlocks like this.
Avoid this and any other similar deadlock vectors in intent and
unlinked inode recovery by starting the log worker before we recover
intents and unlinked inodes. This part of recovery runs as though
the filesystem is fully active, so we really should have the same
infrastructure running as we normally do at runtime.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Pass the block_device that we plan to use this bio for and the
operation to bio_init to optimize the assignment. A NULL block_device
can be passed, both for the passthrough case on a raw request_queue and
to temporarily avoid refactoring some nasty code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220124091107.642561-19-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that we've gotten rid of the kmem_zone_t typedef, rename the
variables to _cache since that's what they are.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Remove these typedefs by referencing kmem_cache directly.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
The remaining mount flags kept in m_flags are actually runtime state
flags. These change dynamically, so they really should be updated
atomically so we don't potentially lose an update due to racing
modifications.
Convert these remaining flags to be stored in m_opstate and use
atomic bitops to set and clear the flags. This also adds a couple of
simple wrappers for common state checks - read only and shutdown.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Replace m_flags feature checks with xfs_has_<feature>() calls and
rework the setup code to set flags in m_features.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Convert the xfs_sb_version_hasfoo() to checks against
mp->m_features. Checks of the superblock itself during disk
operations (e.g. in the read/write verifiers and the to/from disk
formatters) are not converted - they operate purely on the
superblock state. Everything else should use the mount features.
Large parts of this conversion were done with sed with commands like
this:
for f in `git grep -l xfs_sb_version_has fs/xfs/*.c`; do
sed -i -e 's/xfs_sb_version_has\(.*\)(&\(.*\)->m_sb)/xfs_has_\1(\2)/' $f
done
With manual cleanups for things like "xfs_has_extflgbit" and other
little inconsistencies in naming.
The result is ia lot less typing to check features and an XFS binary
size reduced by a bit over 3kB:
$ size -t fs/xfs/built-in.a
text data bss dec hex filenam
before 1130866 311352 484 1442702 16038e (TOTALS)
after 1127727 311352 484 1439563 15f74b (TOTALS)
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
The AIL pushing is stalling on log forces when it comes across
pinned items. This is happening on removal workloads where the AIL
is dominated by stale items that are removed from AIL when the
checkpoint that marks the items stale is committed to the journal.
This results is relatively few items in the AIL, but those that are
are often pinned as directories items are being removed from are
still being logged.
As a result, many push cycles through the CIL will first issue a
blocking log force to unpin the items. This can take some time to
complete, with tracing regularly showing push delays of half a
second and sometimes up into the range of several seconds. Sequences
like this aren't uncommon:
....
399.829437: xfsaild: last lsn 0x11002dd000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 270ms delay>
400.099622: xfsaild: target 0x11002f3600, prev 0x11002f3600, last lsn 0x0
400.099623: xfsaild: first lsn 0x11002f3600
400.099679: xfsaild: last lsn 0x1100305000 count 16 stuck 11 flushing 0 tout 50
<wanted 50ms, got 500ms delay>
400.589348: xfsaild: target 0x110032e600, prev 0x11002f3600, last lsn 0x0
400.589349: xfsaild: first lsn 0x1100305000
400.589595: xfsaild: last lsn 0x110032e600 count 156 stuck 101 flushing 30 tout 50
<wanted 50ms, got 460ms delay>
400.950341: xfsaild: target 0x1100353000, prev 0x110032e600, last lsn 0x0
400.950343: xfsaild: first lsn 0x1100317c00
400.950436: xfsaild: last lsn 0x110033d200 count 105 stuck 101 flushing 0 tout 20
<wanted 20ms, got 200ms delay>
401.142333: xfsaild: target 0x1100361600, prev 0x1100353000, last lsn 0x0
401.142334: xfsaild: first lsn 0x110032e600
401.142535: xfsaild: last lsn 0x1100353000 count 122 stuck 101 flushing 8 tout 10
<wanted 10ms, got 10ms delay>
401.154323: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x1100353000
401.154328: xfsaild: first lsn 0x1100353000
401.154389: xfsaild: last lsn 0x1100353000 count 101 stuck 101 flushing 0 tout 20
<wanted 20ms, got 300ms delay>
401.451525: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
401.451526: xfsaild: first lsn 0x1100353000
401.451804: xfsaild: last lsn 0x1100377200 count 170 stuck 22 flushing 122 tout 50
<wanted 50ms, got 500ms delay>
401.933581: xfsaild: target 0x1100361600, prev 0x1100361600, last lsn 0x0
....
In each of these cases, every AIL pass saw 101 log items stuck on
the AIL (pinned) with very few other items being found. Each pass, a
log force was issued, and delay between last/first is the sleep time
+ the sync log force time.
Some of these 101 items pinned the tail of the log. The tail of the
log does slowly creep forward (first lsn), but the problem is that
the log is actually out of reservation space because it's been
running so many transactions that stale items that never reach the
AIL but consume log space. Hence we have a largely empty AIL, with
long term pins on items that pin the tail of the log that don't get
pushed frequently enough to keep log space available.
The problem is the hundreds of milliseconds that we block in the log
force pushing the CIL out to disk. The AIL should not be stalled
like this - it needs to run and flush items that are at the tail of
the log with minimal latency. What we really need to do is trigger a
log flush, but then not wait for it at all - we've already done our
waiting for stuff to complete when we backed off prior to the log
force being issued.
Even if we remove the XFS_LOG_SYNC from the xfs_log_force() call, we
still do a blocking flush of the CIL and that is what is causing the
issue. Hence we need a new interface for the CIL to trigger an
immediate background push of the CIL to get it moving faster but not
to wait on that to occur. While the CIL is pushing, the AIL can also
be pushing.
We already have an internal interface to do this -
xlog_cil_push_now() - but we need a wrapper for it to be used
externally. xlog_cil_force_seq() can easily be extended to do what
we need as it already implements the synchronous CIL push via
xlog_cil_push_now(). Add the necessary flags and "push current
sequence" semantics to xlog_cil_force_seq() and convert the AIL
pushing to use it.
One of the complexities here is that the CIL push does not guarantee
that the commit record for the CIL checkpoint is written to disk.
The current log force ensures this by submitting the current ACTIVE
iclog that the commit record was written to. We need the CIL to
actually write this commit record to disk for an async push to
ensure that the checkpoint actually makes it to disk and unpins the
pinned items in the checkpoint on completion. Hence we need to pass
down to the CIL push that we are doing an async flush so that it can
switch out the commit_iclog if necessary to get written to disk when
the commit iclog is finally released.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Because log recovery depends on strictly ordered start records as
well as strictly ordered commit records.
This is a zero day bug in the way XFS writes pipelined transactions
to the journal which is exposed by fixing the zero day bug that
prevents the CIL from pipelining checkpoints. This re-introduces
explicit concurrent commits back into the on-disk journal and hence
out of order start records.
The XFS journal commit code has never ordered start records and we
have relied on strict commit record ordering for correct recovery
ordering of concurrently written transactions. Unfortunately, root
cause analysis uncovered the fact that log recovery uses the LSN of
the start record for transaction commit processing. Hence, whilst
the commits are processed in strict order by recovery, the LSNs
associated with the commits can be out of order and so recovery may
stamp incorrect LSNs into objects and/or misorder intents in the AIL
for later processing. This can result in log recovery failures
and/or on disk corruption, sometimes silent.
Because this is a long standing log recovery issue, we can't just
fix log recovery and call it good. This still leaves older kernels
susceptible to recovery failures and corruption when replaying a log
from a kernel that pipelines checkpoints. There is also the issue
that in-memory ordering for AIL pushing and data integrity
operations are based on checkpoint start LSNs, and if the start LSN
is incorrect in the journal, it is also incorrect in memory.
Hence there's really only one choice for fixing this zero-day bug:
we need to strictly order checkpoint start records in ascending
sequence order in the log, the same way we already strictly order
commit records.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Now that we have a mechanism to guarantee that the callbacks
attached to an iclog are owned by the context that attaches them
until they drop their reference to the iclog via
xlog_state_release_iclog(), we can attach callbacks to the iclog at
any time we have an active reference to the iclog.
xlog_state_get_iclog_space() always guarantees that the commit
record will fit in the iclog it returns, so we can move this IO
callback setting to xlog_cil_set_ctx_write_state(), record the
commit iclog in the context and remove the need for the commit iclog
to be returned by xlog_write() altogether.
This, in turn, allows us to move the wakeup for ordered commit
record writes up into xlog_cil_set_ctx_write_state(), too, because
we have been guaranteed that this commit record will be physically
located in the iclog before any waiting commit record at a higher
sequence number will be granted iclog space.
This further cleans up the post commit record write processing in
the CIL push code, especially as xlog_state_release_iclog() will now
clean up the context when shutdown errors occur.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Pass the CIL context to xlog_write() rather than a pointer to a LSN
variable. Only the CIL checkpoint calls to xlog_write() need to know
about the start LSN of the writes, so rework xlog_write to directly
write the LSNs into the CIL context structure.
This removes the commit_lsn variable from xlog_cil_push_work(), so
now we only have to issue the commit record ordering wakeup from
there.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
It is only used by the CIL checkpoints, and is the counterpart to
start record formatting and writing that is already local to
xfs_log_cil.c.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
I'm seeing assert failures from xlog_space_left() after a shutdown
has begun that look like:
XFS (dm-0): log I/O error -5
XFS (dm-0): xfs_do_force_shutdown(0x2) called from line 1338 of file fs/xfs/xfs_log.c. Return address = xlog_ioend_work+0x64/0xc0
XFS (dm-0): Log I/O Error Detected.
XFS (dm-0): Shutting down filesystem. Please unmount the filesystem and rectify the problem(s)
XFS (dm-0): xlog_space_left: head behind tail
XFS (dm-0): tail_cycle = 6, tail_bytes = 2706944
XFS (dm-0): GH cycle = 6, GH bytes = 1633867
XFS: Assertion failed: 0, file: fs/xfs/xfs_log.c, line: 1310
------------[ cut here ]------------
Call Trace:
xlog_space_left+0xc3/0x110
xlog_grant_push_threshold+0x3f/0xf0
xlog_grant_push_ail+0x12/0x40
xfs_log_reserve+0xd2/0x270
? __might_sleep+0x4b/0x80
xfs_trans_reserve+0x18b/0x260
.....
There are two things here. Firstly, after a shutdown, the log head
and tail can be out of whack as things abort and release (or don't
release) resources, so checking them for sanity doesn't make much
sense. Secondly, xfs_log_reserve() can race with shutdown and so it
can still fail like this even though it has already checked for a
log shutdown before calling xlog_grant_push_ail().
So, before ASSERT failing in xlog_space_left(), make sure we haven't
already shut down....
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
When the log is shutdown, it currently walks all the iclogs and runs
callbacks that are attached to the iclogs, regardless of whether the
iclog is queued for IO completion or not. This creates a problem for
contexts attaching callbacks to iclogs in that a racing shutdown can
run the callbacks even before the attaching context has finished
processing the iclog and releasing it for IO submission.
If the callback processing of the iclog frees the structure that is
attached to the iclog, then this leads to an UAF scenario that can
only be protected against by holding the icloglock from the point
callbacks are attached through to the release of the iclog. While we
currently do this, it is not practical or sustainable.
Hence we need to make shutdown processing the responsibility of the
context that holds active references to the iclog. We know that the
contexts attaching callbacks to the iclog must have active
references to the iclog, and that means they must be in either
ACTIVE or WANT_SYNC states. xlog_state_do_callback() will skip over
iclogs in these states -except- when the log is shut down.
xlog_state_do_callback() checks the state of the iclogs while
holding the icloglock, therefore the reference count/state change
that occurs in xlog_state_release_iclog() after the callbacks are
atomic w.r.t. shutdown processing.
We can't push the responsibility of callback cleanup onto the CIL
context because we can have ACTIVE iclogs that have callbacks
attached that have already been released. Hence we really need to
internalise the cleanup of callbacks into xlog_state_release_iclog()
processing.
Indeed, we already have that internalisation via:
xlog_state_release_iclog
drop last reference
->SYNCING
xlog_sync
xlog_write_iclog
if (log_is_shutdown)
xlog_state_done_syncing()
xlog_state_do_callback()
<process shutdown on iclog that is now in SYNCING state>
The problem is that xlog_state_release_iclog() aborts before doing
anything if the log is already shut down. It assumes that the
callbacks have already been cleaned up, and it doesn't need to do
any cleanup.
Hence the fix is to remove the xlog_is_shutdown() check from
xlog_state_release_iclog() so that reference counts are correctly
released from the iclogs, and when the reference count is zero we
always transition to SYNCING if the log is shut down. Hence we'll
always enter the xlog_sync() path in a shutdown and eventually end
up erroring out the iclog IO and running xlog_state_do_callback() to
process the callbacks attached to the iclog.
This allows us to stop processing referenced ACTIVE/WANT_SYNC iclogs
directly in the shutdown code, and in doing so gets rid of the UAF
vector that currently exists. This then decouples the adding of
callbacks to the iclogs from xlog_state_release_iclog() as we
guarantee that xlog_state_release_iclog() will process the callbacks
if the log has been shut down before xlog_state_release_iclog() has
been called.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
The iclog callback processing done during a forced log shutdown has
different logic to normal runtime IO completion callback processing.
Separate out the shutdown callbacks into their own function and call
that from the shutdown code instead.
We don't need this shutdown specific logic in the normal runtime
completion code - we'll always run the shutdown version on shutdown,
and it will do what shutdown needs regardless of whether there are
racing IO completion callbacks scheduled or in progress. Hence we
can also simplify the normal IO completion callpath and only abort
if shutdown occurred while we actively were processing callbacks.
Further, separating out the IO completion logic from the shutdown
logic avoids callback race conditions from being triggered by log IO
completion after a shutdown. IO completion will now only run
callbacks on iclogs that are in the correct state for a callback to
be run, avoiding the possibility of running callbacks on a
referenced iclog that hasn't yet been submitted for IO.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Clean it up a bit by factoring and rearranging some of the code.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
The running of a forced shutdown is a bit of a mess. It does racy
checks for XFS_MOUNT_SHUTDOWN in xfs_do_force_shutdown(), then
does more racy checks in xfs_log_force_unmount() before finally
setting XFS_MOUNT_SHUTDOWN and XLOG_IO_ERROR under the
log->icloglock.
Move the checking and setting of XFS_MOUNT_SHUTDOWN into
xfs_do_force_shutdown() so we only process a shutdown once and once
only. Serialise this with the mp->m_sb_lock spinlock so that the
state change is atomic and won't race. Move all the mount specific
shutdown state changes from xfs_log_force_unmount() to
xfs_do_force_shutdown() so they are done atomically with setting
XFS_MOUNT_SHUTDOWN.
Then get rid of the racy xlog_is_shutdown() check from
xlog_force_shutdown(), and gate the log shutdown on the
test_and_set_bit(XLOG_IO_ERROR) test under the icloglock. This
means that the log is shutdown once and once only, and code that
needs to prevent races with shutdown can do so by holding the
icloglock and checking the return value of xlog_is_shutdown().
This results in a predictable shutdown execution process - we set the
shutdown flags once and process the shutdown once rather than the
current "as many concurrent shutdowns as can race to the flag
setting" situation we have now.
Also, now that shutdown is atomic, alway emit a stack trace when the
error level for the filesystem is high enough. This means that we
always get a stack trace when trying to diagnose the cause of
shutdowns in the field, rather than just for SHUTDOWN_CORRUPT_INCORE
cases.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
log->l_flags doesn't actually contain "flags" as such, it contains
operational state information that can change at runtime. For the
shutdown state, this at least should be an atomic bit because
it is read without holding locks in many places and so using atomic
bitops for the state field modifications makes sense.
This allows us to use things like test_and_set_bit() on state
changes (e.g. setting XLOG_TAIL_WARN) to avoid races in setting the
state when we aren't holding locks.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
xfs_log_mount_finish() needs to know if recovery is needed or not to
make decisions on whether to flush the log and AIL. Move the
handling of the NEED_RECOVERY state out to this function rather than
needing a temporary variable to store this state over the call to
xlog_recover_finish().
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
We don't need an iclog state field to tell us the log has been shut
down. We can just check the xlog_is_shutdown() instead. The avoids
the need to have shutdown overwrite the current iclog state while
being active used by the log code and so having to ensure that every
iclog state check handles XLOG_STATE_IOERROR appropriately.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Make it less shouty and a static inline before adding more calls
through the log code.
Also convert internal log code that uses XFS_FORCED_SHUTDOWN(mount)
to use xlog_is_shutdown(log) as well.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
When there are no ongoing transactions and the log contents have been
checkpointed back into the filesystem, the log performs 'covering',
which is to say that it log a dummy transaction to record the fact that
the tail has caught up with the head. This is a good time to clear log
incompat feature flags, because they are flags that are temporarily set
to limit the range of kernels that can replay a dirty log.
Since it's possible that some other higher level thread is about to
start logging items protected by a log incompat flag, we create a rwsem
so that upper level threads can coordinate this with the log. It would
probably be more performant to use a percpu rwsem, but the ability to
/try/ taking the write lock during covering is critical, and percpu
rwsems do not provide that.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Log incompat feature flags in the superblock exist for one purpose: to
protect the contents of a dirty log from replay on a kernel that isn't
prepared to handle those dirty contents. This means that they can be
cleared if (a) we know the log is clean and (b) we know that there
aren't any other threads in the system that might be setting or relying
upon a log incompat flag.
Therefore, clear the log incompat flags when we've finished recovering
the log, when we're unmounting cleanly, remounting read-only, or
freezing; and provide a function so that subsequent patches can start
using this.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
