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>
There is no reason for this wrapper existing anymore. All the places
that use KM_NOFS allocation are within transaction contexts and
hence covered by memalloc_nofs_save/restore contexts. Hence we don't
need any special handling of vmalloc for large IOs anymore and
so special casing this code isn't necessary.
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>
Since commit 59bb47985c ("mm, sl[aou]b: guarantee natural alignment
for kmalloc(power-of-two)"), the core slab code now guarantees slab
alignment in all situations sufficient for IO purposes (i.e. minimum
of 512 byte alignment of >= 512 byte sized heap allocations) we no
longer need the workaround in the XFS code to provide this
guarantee.
Replace the use of kmem_alloc_io() with kmem_alloc() or
kmem_alloc_large() appropriately, and remove the kmem_alloc_io()
interface altogether.
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>
From the department of "generic/482 keeps on giving", we bring you
another tail update race condition:
iclog:
S1 C1
+-----------------------+-----------------------+
S2 EOIC
Two checkpoints in a single iclog. One is complete, the other just
contains the start record and overruns into a new iclog.
Timeline:
Before S1: Cache flush, log tail = X
At S1: Metadata stable, write start record and checkpoint
At C1: Write commit record, set NEED_FUA
Single iclog checkpoint, so no need for NEED_FLUSH
Log tail still = X, so no need for NEED_FLUSH
After C1,
Before S2: Cache flush, log tail = X
At S2: Metadata stable, write start record and checkpoint
After S2: Log tail moves to X+1
At EOIC: End of iclog, more journal data to write
Releases iclog
Not a commit iclog, so no need for NEED_FLUSH
Writes log tail X+1 into iclog.
At this point, the iclog has tail X+1 and NEED_FUA set. There has
been no cache flush for the metadata between X and X+1, and the
iclog writes the new tail permanently to the log. THis is sufficient
to violate on disk metadata/journal ordering.
We have two options here. The first is to detect this case in some
manner and ensure that the partial checkpoint write sets NEED_FLUSH
when the iclog is already marked NEED_FUA and the log tail changes.
This seems somewhat fragile and quite complex to get right, and it
doesn't actually make it obvious what underlying problem it is
actually addressing from reading the code.
The second option seems much cleaner to me, because it is derived
directly from the requirements of the C1 commit record in the iclog.
That is, when we write this commit record to the iclog, we've
guaranteed that the metadata/data ordering is correct for tail
update purposes. Hence if we only write the log tail into the iclog
for the *first* commit record rather than the log tail at the last
release, we guarantee that the log tail does not move past where the
the first commit record in the log expects it to be.
IOWs, taking the first option means that replay of C1 becomes
dependent on future operations doing the right thing, not just the
C1 checkpoint itself doing the right thing. This makes log recovery
almost impossible to reason about because now we have to take into
account what might or might not have happened in the future when
looking at checkpoints in the log rather than just having to
reconstruct the past...
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>
Before waiting on a iclog in xfs_log_force_lsn(), we don't check to
see if the iclog has already been completed and the contents on
stable storage. We check for completed iclogs in xfs_log_force(), so
we should do the same thing for xfs_log_force_lsn().
This fixed some random up-to-30s pauses seen in unmounting
filesystems in some tests. A log force ends up waiting on completed
iclog, and that doesn't then get flushed (and hence the log force
get completed) until the background log worker issues a log force
that flushes the iclog in question. Then the unmount unblocks and
continues.
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>
After fixing the tail_lsn vs cache flush race, generic/482 continued
to fail in a similar way where cache flushes were missing before
iclog FUA writes. Tracing of iclog state changes during the fsstress
workload portion of the test (via xlog_iclog* events) indicated that
iclog writes were coming from two sources - CIL pushes and log
forces (due to fsync/O_SYNC operations). All of the cases where a
recovery problem was triggered indicated that the log force was the
source of the iclog write that was not preceeded by a cache flush.
This was an oversight in the modifications made in commit
eef983ffea ("xfs: journal IO cache flush reductions"). Log forces
for fsync imply a data device cache flush has been issued if an
iclog was flushed to disk and is indicated to the caller via the
log_flushed parameter so they can elide the device cache flush if
the journal issued one.
The change in eef983ffea results in iclogs only issuing a cache
flush if XLOG_ICL_NEED_FLUSH is set on the iclog, but this was not
added to the iclogs that the log force code flushes to disk. Hence
log forces are no longer guaranteeing that a cache flush is issued,
hence opening up a potential on-disk ordering failure.
Log forces should also set XLOG_ICL_NEED_FUA as well to ensure that
the actual iclogs it forces to the journal are also on stable
storage before it returns to the caller.
This patch introduces the xlog_force_iclog() helper function to
encapsulate the process of taking a reference to an iclog, switching
its state if WANT_SYNC and flushing it to stable storage correctly.
Both xfs_log_force() and xfs_log_force_lsn() are converted to use
it, as is xlog_unmount_write() which has an elaborate method of
doing exactly the same "write this iclog to stable storage"
operation.
Further, if the log force code needs to wait on a iclog in the
WANT_SYNC state, it needs to ensure that iclog also results in a
cache flush being issued. This covers the case where the iclog
contains the commit record of the CIL flush that the log force
triggered, but it hasn't been written yet because there is still an
active reference to the iclog.
Note: this whole cache flush whack-a-mole patch is a result of log
forces still being iclog state centric rather than being CIL
sequence centric. Most of this nasty code will go away in future
when log forces are converted to wait on CIL sequence push
completion rather than iclog completion. With the CIL push algorithm
guaranteeing that the CIL checkpoint is fully on stable storage when
it completes, we no longer need to iterate iclogs and push them to
ensure a CIL sequence push has completed and so all this nasty iclog
iteration and flushing code will go away.
Fixes: eef983ffea ("xfs: journal IO cache flush reductions")
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 force iclogs in several places - we need them all to have the
same cache flush semantics, so start by factoring out the iclog
force into a common helper.
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>
There is a race between the new CIL async data device metadata IO
completion cache flush and the log tail in the iclog the flush
covers being updated. This can be seen by repeating generic/482 in a
loop and eventually log recovery fails with a failures such as this:
XFS (dm-3): Starting recovery (logdev: internal)
XFS (dm-3): bad inode magic/vsn daddr 228352 #0 (magic=0)
XFS (dm-3): Metadata corruption detected at xfs_inode_buf_verify+0x180/0x190, xfs_inode block 0x37c00 xfs_inode_buf_verify
XFS (dm-3): Unmount and run xfs_repair
XFS (dm-3): First 128 bytes of corrupted metadata buffer:
00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
XFS (dm-3): metadata I/O error in "xlog_recover_items_pass2+0x55/0xc0" at daddr 0x37c00 len 32 error 117
Analysis of the logwrite replay shows that there were no writes to
the data device between the FUA @ write 124 and the FUA at write @
125, but log recovery @ 125 failed. The difference was the one log
write @ 125 moved the tail of the log forwards from (1,8) to (1,32)
and so the inode create intent in (1,8) was not replayed and so the
inode cluster was zero on disk when replay of the first inode item
in (1,32) was attempted.
What this meant was that the journal write that occurred at @ 125
did not ensure that metadata completed before the iclog was written
was correctly on stable storage. The tail of the log moved forward,
so IO must have been completed between the two iclog writes. This
means that there is a race condition between the unconditional async
cache flush in the CIL push work and the tail LSN that is written to
the iclog. This happens like so:
CIL push work AIL push work
------------- -------------
Add to committing list
start async data dev cache flush
.....
<flush completes>
<all writes to old tail lsn are stable>
xlog_write
.... push inode create buffer
<start IO>
.....
xlog_write(commit record)
.... <IO completes>
log tail moves
xlog_assign_tail_lsn()
start_lsn == commit_lsn
<no iclog preflush!>
xlog_state_release_iclog
__xlog_state_release_iclog()
<writes *new* tail_lsn into iclog>
xlog_sync()
....
submit_bio()
<tail in log moves forward without flushing written metadata>
Essentially, this can only occur if the commit iclog is issued
without a cache flush. If the iclog bio is submitted with
REQ_PREFLUSH, then it will guarantee that all the completed IO is
one stable storage before the iclog bio with the new tail LSN in it
is written to the log.
IOWs, the tail lsn that is written to the iclog needs to be sampled
*before* we issue the cache flush that guarantees all IO up to that
LSN has been completed.
To fix this without giving up the performance advantage of the
flush/FUA optimisations (e.g. g/482 runtime halves with 5.14-rc1
compared to 5.13), we need to ensure that we always issue a cache
flush if the tail LSN changes between the initial async flush and
the commit record being written. THis requires sampling the tail_lsn
before we start the flush, and then passing the sampled tail LSN to
xlog_state_release_iclog() so it can determine if the the tail LSN
has changed while writing the checkpoint. If the tail LSN has
changed, then it needs to set the NEED_FLUSH flag on the iclog and
we'll issue another cache flush before writing the iclog.
Fixes: eef983ffea ("xfs: journal IO cache flush reductions")
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>
Fold __xlog_state_release_iclog into its only caller to prepare
make an upcoming fix easier.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
[hch: split from a larger patch]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
The recent journal flush/FUA changes replaced the flushing of the
data device on every iclog write with an up-front async data device
cache flush. Unfortunately, the assumption of which this was based
on has been proven incorrect by the flush vs log tail update
ordering issue. As the fix for that issue uses the
XLOG_ICL_NEED_FLUSH flag to indicate that data device needs a cache
flush, we now need to (once again) ensure that an iclog write to
external logs that need a cache flush to be issued actually issue a
cache flush to the data device as well as the log device.
Fixes: eef983ffea ("xfs: journal IO cache flush reductions")
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 incorrectly flush the log device instead of the data device when
trying to ensure metadata is correctly on disk before writing the
unmount record.
Fixes: eef983ffea ("xfs: journal IO cache flush reductions")
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>
- Refactor the buffer cache to use bulk page allocation
- Convert agnumber-based AG iteration to walk per-AG structures
- Clean up some unit conversions and other code warts
- Reduce spinlock contention in the directio fastpath
- Collapse all the inode cache walks into a single function
- Remove indirect function calls from the inode cache walk code
- Dramatically reduce the number of cache flushes sent when writing log
buffers
- Preserve inode sickness reports for longer
- Rename xfs_eofblocks since it controls inode cache walks
- Refactor the extended attribute code to prepare it for the addition
of log intent items to make xattrs fully transactional
- A few fixes to earlier large patchsets
- Log recovery fixes so that we don't accidentally mark the log clean
when log intent recovery fails
- Fix some latent SOB errors
- Clean up shutdown messages that get logged to dmesg
- Fix a regression in the online shrink code
- Fix a UAF in the buffer logging code if the fs goes offline
- Fix uninitialized error variables
- Fix a UAF in the CIL when commited log item callbacks race with a
shutdown
- Fix a bug where the CIL could hang trying to push part of the log ring
buffer that hasn't been filled yet
-----BEGIN PGP SIGNATURE-----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=08Q9
-----END PGP SIGNATURE-----
Merge tag 'xfs-5.14-merge-6' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux
Pull xfs updates from Darrick Wong:
"Most of the work this cycle has been on refactoring various parts of
the codebase. The biggest non-cleanup changes are (1) reducing the
number of cache flushes sent when writing the log; (2) a substantial
number of log recovery fixes; and (3) I started accepting pull
requests from contributors if the commits in their branches match
what's been sent to the list.
For a week or so I /had/ staged a major cleanup of the logging code
from Dave Chinner, but it exposed so many lurking bugs in other parts
of the logging and log recovery code that I decided to defer that
patchset until we can address those latent bugs.
Larger cleanups this time include walking the incore inode cache (me)
and rework of the extended attribute code (Allison) to prepare it for
adding logged xattr updates (and directory tree parent pointers) in
future releases.
Summary:
- Refactor the buffer cache to use bulk page allocation
- Convert agnumber-based AG iteration to walk per-AG structures
- Clean up some unit conversions and other code warts
- Reduce spinlock contention in the directio fastpath
- Collapse all the inode cache walks into a single function
- Remove indirect function calls from the inode cache walk code
- Dramatically reduce the number of cache flushes sent when writing
log buffers
- Preserve inode sickness reports for longer
- Rename xfs_eofblocks since it controls inode cache walks
- Refactor the extended attribute code to prepare it for the addition
of log intent items to make xattrs fully transactional
- A few fixes to earlier large patchsets
- Log recovery fixes so that we don't accidentally mark the log clean
when log intent recovery fails
- Fix some latent SOB errors
- Clean up shutdown messages that get logged to dmesg
- Fix a regression in the online shrink code
- Fix a UAF in the buffer logging code if the fs goes offline
- Fix uninitialized error variables
- Fix a UAF in the CIL when commited log item callbacks race with a
shutdown
- Fix a bug where the CIL could hang trying to push part of the log
ring buffer that hasn't been filled yet"
* tag 'xfs-5.14-merge-6' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux: (102 commits)
xfs: don't wait on future iclogs when pushing the CIL
xfs: Fix a CIL UAF by getting get rid of the iclog callback lock
xfs: remove callback dequeue loop from xlog_state_do_iclog_callbacks
xfs: don't nest icloglock inside ic_callback_lock
xfs: Initialize error in xfs_attr_remove_iter
xfs: fix endianness issue in xfs_ag_shrink_space
xfs: remove dead stale buf unpin handling code
xfs: hold buffer across unpin and potential shutdown processing
xfs: force the log offline when log intent item recovery fails
xfs: fix log intent recovery ENOSPC shutdowns when inactivating inodes
xfs: shorten the shutdown messages to a single line
xfs: print name of function causing fs shutdown instead of hex pointer
xfs: fix type mismatches in the inode reclaim functions
xfs: separate primary inode selection criteria in xfs_iget_cache_hit
xfs: refactor the inode recycling code
xfs: add iclog state trace events
xfs: xfs_log_force_lsn isn't passed a LSN
xfs: Fix CIL throttle hang when CIL space used going backwards
xfs: journal IO cache flush reductions
xfs: remove need_start_rec parameter from xlog_write()
...
The iclog callback chain has it's own lock. That was added way back
in 2008 by myself to alleviate severe lock contention on the
icloglock in commit 114d23aae5 ("[XFS] Per iclog callback chain
lock"). This was long before delayed logging took the icloglock out
of the hot transaction commit path and removed all contention on it.
Hence the separate ic_callback_lock doesn't serve any scalability
purpose anymore, and hasn't for close on a decade.
Further, we only attach callbacks to iclogs in one place where we
are already taking the icloglock soon after attaching the callbacks.
We also have to drop the icloglock to run callbacks and grab it
immediately afterwards again. So given that the icloglock is no
longer hot, making it cover callbacks again doesn't really change
the locking patterns very much at all.
We also need to extend the icloglock to cover callback addition to
fix a zero-day UAF in the CIL push code. This occurs when shutdown
races with xlog_cil_push_work() and the shutdown runs the callbacks
before the push releases the iclog. This results in the CIL context
structure attached to the iclog being freed by the callback before
the CIL push has finished referencing it, leading to UAF bugs.
Hence, to avoid this UAF, we need the callback attachment to be
atomic with post processing of the commit iclog and references to
the structures being attached to the iclog. This requires holding
the icloglock as that's the only way to serialise iclog state
against a shutdown in progress.
The result is we need to be using the icloglock to protect the
callback list addition and removal and serialise them with shutdown.
That makes the ic_callback_lock redundant and so it can be removed.
Fixes: 71e330b593 ("xfs: Introduce delayed logging core code")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
If we are processing callbacks on an iclog, nothing can be
concurrently adding callbacks to the loop. We only add callbacks to
the iclog when they are in ACTIVE or WANT_SYNC state, and we
explicitly do not add callbacks if the iclog is already in IOERROR
state.
The only way to have a dequeue racing with an enqueue is to be
processing a shutdown without a direct reference to an iclog in
ACTIVE or WANT_SYNC state. As the enqueue avoids this race
condition, we only ever need a single dequeue operation in
xlog_state_do_iclog_callbacks(). Hence we can remove the loop.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
It's completely unnecessary because callbacks are added to iclogs
without holding the icloglock, hence no amount of ordering between
the icloglock and ic_callback_lock will order the removal of
callbacks from the iclog.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
If any part of log intent item recovery fails, we should shut down the
log immediately to stop the log from writing a clean unmount record to
disk, because the metadata is not consistent. The inability to cancel a
dirty transaction catches most of these cases, but there are a few
things that have slipped through the cracks, such as ENOSPC from a
transaction allocation, or runtime errors that result in cancellation of
a non-dirty transaction.
This solves some weird behaviors reported by customers where a system
goes down, the first mount fails, the second succeeds, but then the fs
goes down later because of inconsistent metadata.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
For the DEBUGS!
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>
In doing an investigation into AIL push stalls, I was looking at the
log force code to see if an async CIL push could be done instead.
This lead me to xfs_log_force_lsn() and looking at how it works.
xfs_log_force_lsn() is only called from inode synchronisation
contexts such as fsync(), and it takes the ip->i_itemp->ili_last_lsn
value as the LSN to sync the log to. This gets passed to
xlog_cil_force_lsn() via xfs_log_force_lsn() to flush the CIL to the
journal, and then used by xfs_log_force_lsn() to flush the iclogs to
the journal.
The problem is that ip->i_itemp->ili_last_lsn does not store a
log sequence number. What it stores is passed to it from the
->iop_committing method, which is called by xfs_log_commit_cil().
The value this passes to the iop_committing method is the CIL
context sequence number that the item was committed to.
As it turns out, xlog_cil_force_lsn() converts the sequence to an
actual commit LSN for the related context and returns that to
xfs_log_force_lsn(). xfs_log_force_lsn() overwrites it's "lsn"
variable that contained a sequence with an actual LSN and then uses
that to sync the iclogs.
This caused me some confusion for a while, even though I originally
wrote all this code a decade ago. ->iop_committing is only used by
a couple of log item types, and only inode items use the sequence
number it is passed.
Let's clean up the API, CIL structures and inode log item to call it
a sequence number, and make it clear that the high level code is
using CIL sequence numbers and not on-disk LSNs for integrity
synchronisation purposes.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@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>
Currently every journal IO is issued as REQ_PREFLUSH | REQ_FUA to
guarantee the ordering requirements the journal has w.r.t. metadata
writeback. THe two ordering constraints are:
1. we cannot overwrite metadata in the journal until we guarantee
that the dirty metadata has been written back in place and is
stable.
2. we cannot write back dirty metadata until it has been written to
the journal and guaranteed to be stable (and hence recoverable) in
the journal.
The ordering guarantees of #1 are provided by REQ_PREFLUSH. This
causes the journal IO to issue a cache flush and wait for it to
complete before issuing the write IO to the journal. Hence all
completed metadata IO is guaranteed to be stable before the journal
overwrites the old metadata.
The ordering guarantees of #2 are provided by the REQ_FUA, which
ensures the journal writes do not complete until they are on stable
storage. Hence by the time the last journal IO in a checkpoint
completes, we know that the entire checkpoint is on stable storage
and we can unpin the dirty metadata and allow it to be written back.
This is the mechanism by which ordering was first implemented in XFS
way back in 2002 by commit 95d97c36e5155075ba2eb22b17562cfcc53fcf96
("Add support for drive write cache flushing") in the xfs-archive
tree.
A lot has changed since then, most notably we now use delayed
logging to checkpoint the filesystem to the journal rather than
write each individual transaction to the journal. Cache flushes on
journal IO are necessary when individual transactions are wholly
contained within a single iclog. However, CIL checkpoints are single
transactions that typically span hundreds to thousands of individual
journal writes, and so the requirements for device cache flushing
have changed.
That is, the ordering rules I state above apply to ordering of
atomic transactions recorded in the journal, not to the journal IO
itself. Hence we need to ensure metadata is stable before we start
writing a new transaction to the journal (guarantee #1), and we need
to ensure the entire transaction is stable in the journal before we
start metadata writeback (guarantee #2).
Hence we only need a REQ_PREFLUSH on the journal IO that starts a
new journal transaction to provide #1, and it is not on any other
journal IO done within the context of that journal transaction.
The CIL checkpoint already issues a cache flush before it starts
writing to the log, so we no longer need the iclog IO to issue a
REQ_REFLUSH for us. Hence if XLOG_START_TRANS is passed
to xlog_write(), we no longer need to mark the first iclog in
the log write with REQ_PREFLUSH for this case. As an added bonus,
this ordering mechanism works for both internal and external logs,
meaning we can remove the explicit data device cache flushes from
the iclog write code when using external logs.
Given the new ordering semantics of commit records for the CIL, we
need iclogs containing commit records to issue a REQ_PREFLUSH. We
also require unmount records to do this. Hence for both
XLOG_COMMIT_TRANS and XLOG_UNMOUNT_TRANS xlog_write() calls we need
to mark the first iclog being written with REQ_PREFLUSH.
For both commit records and unmount records, we also want them
immediately on stable storage, so we want to also mark the iclogs
that contain these records to be marked REQ_FUA. That means if a
record is split across multiple iclogs, they are all marked REQ_FUA
and not just the last one so that when the transaction is completed
all the parts of the record are on stable storage.
And for external logs, unmount records need a pre-write data device
cache flush similar to the CIL checkpoint cache pre-flush as the
internal iclog write code does not do this implicitly anymore.
As an optimisation, when the commit record lands in the same iclog
as the journal transaction starts, we don't need to wait for
anything and can simply use REQ_FUA to provide guarantee #2. This
means that for fsync() heavy workloads, the cache flush behaviour is
completely unchanged and there is no degradation in performance as a
result of optimise the multi-IO transaction case.
The most notable sign that there is less IO latency on my test
machine (nvme SSDs) is that the "noiclogs" rate has dropped
substantially. This metric indicates that the CIL push is blocking
in xlog_get_iclog_space() waiting for iclog IO completion to occur.
With 8 iclogs of 256kB, the rate is appoximately 1 noiclog event to
every 4 iclog writes. IOWs, every 4th call to xlog_get_iclog_space()
is blocking waiting for log IO. With the changes in this patch, this
drops to 1 noiclog event for every 100 iclog writes. Hence it is
clear that log IO is completing much faster than it was previously,
but it is also clear that for large iclog sizes, this isn't the
performance limiting factor on this hardware.
With smaller iclogs (32kB), however, there is a substantial
difference. With the cache flush modifications, the journal is now
running at over 4000 write IOPS, and the journal throughput is
largely identical to the 256kB iclogs and the noiclog event rate
stays low at about 1:50 iclog writes. The existing code tops out at
about 2500 IOPS as the number of cache flushes dominate performance
and latency. The noiclog event rate is about 1:4, and the
performance variance is quite large as the journal throughput can
fall to less than half the peak sustained rate when the cache flush
rate prevents metadata writeback from keeping up and the log runs
out of space and throttles reservations.
As a result:
logbsize fsmark create rate rm -rf
before 32kb 152851+/-5.3e+04 5m28s
patched 32kb 221533+/-1.1e+04 5m24s
before 256kb 220239+/-6.2e+03 4m58s
patched 256kb 228286+/-9.2e+03 5m06s
The rm -rf times are included because I ran them, but the
differences are largely noise. This workload is largely metadata
read IO latency bound and the changes to the journal cache flushing
doesn't really make any noticable difference to behaviour apart from
a reduction in noiclog events from background CIL pushing.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.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>
The CIL push is the only call to xlog_write that sets this variable
to true. The other callers don't need a start rec, and they tell
xlog_write what to do by passing the type of ophdr they need written
in the flags field. The need_start_rec parameter essentially tells
xlog_write to to write an extra ophdr with a XLOG_START_TRANS type,
so get rid of the variable to do this and pass XLOG_START_TRANS as
the flag value into xlog_write() from the CIL push.
$ size fs/xfs/xfs_log.o*
text data bss dec hex filename
27595 560 8 28163 6e03 fs/xfs/xfs_log.o.orig
27454 560 8 28022 6d76 fs/xfs/xfs_log.o.patched
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.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>
It's a one line wrapper around blkdev_issue_flush(). Just replace it
with direct calls to blkdev_issue_flush().
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
To allow for iclog IO device cache flush behaviour to be optimised,
we first need to separate out the commit record iclog IO from the
rest of the checkpoint so we can wait for the checkpoint IO to
complete before we issue the commit record.
This separation is only necessary if the commit record is being
written into a different iclog to the start of the checkpoint as the
upcoming cache flushing changes requires completion ordering against
the other iclogs submitted by the checkpoint.
If the entire checkpoint and commit is in the one iclog, then they
are both covered by the one set of cache flush primitives on the
iclog and hence there is no need to separate them for ordering.
Otherwise, we need to wait for all the previous iclogs to complete
so they are ordered correctly and made stable by the REQ_PREFLUSH
that the commit record iclog IO issues. This guarantees that if a
reader sees the commit record in the journal, they will also see the
entire checkpoint that commit record closes off.
This also provides the guarantee that when the commit record IO
completes, we can safely unpin all the log items in the checkpoint
so they can be written back because the entire checkpoint is stable
in the journal.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
On 32-bit (e.g. m68k):
ERROR: modpost: "__udivdi3" [fs/xfs/xfs.ko] undefined!
Fix this by using a uint32_t intermediate, like before.
Reported-by: noreply@ellerman.id.au
Fixes: 7660a5b48fbef958 ("xfs: log stripe roundoff is a property of the log")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
We don't need to look at the xfs_mount and superblock every time we
need to do an iclog roundoff calculation. The property is fixed for
the life of the log, so store the roundoff in the log at mount time
and use that everywhere.
On a debug build:
$ size fs/xfs/xfs_log.o.*
text data bss dec hex filename
27360 560 8 27928 6d18 fs/xfs/xfs_log.o.orig
27219 560 8 27787 6c8b fs/xfs/xfs_log.o.patched
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
In preparation to enable -Wimplicit-fallthrough for Clang, fix
the following warnings by replacing /* fall through */ comments,
and its variants, with the new pseudo-keyword macro fallthrough:
fs/xfs/libxfs/xfs_alloc.c:3167:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/libxfs/xfs_da_btree.c:286:3: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/libxfs/xfs_ag_resv.c:346:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/libxfs/xfs_ag_resv.c:388:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/xfs_bmap_util.c:246:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/xfs_export.c:88:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/xfs_export.c:96:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/xfs_file.c:867:3: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/xfs_ioctl.c:562:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/xfs_ioctl.c:1548:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/xfs_iomap.c:1040:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/xfs_inode.c:852:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/xfs_log.c:2627:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/xfs_trans_buf.c:298:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/scrub/bmap.c:275:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/scrub/btree.c:48:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/scrub/common.c:85:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/scrub/common.c:138:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/scrub/common.c:698:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/scrub/dabtree.c:51:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/scrub/repair.c:951:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
fs/xfs/scrub/agheader.c:89:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
Notice that Clang doesn't recognize /* fall through */ comments as
implicit fall-through markings, so in order to globally enable
-Wimplicit-fallthrough for Clang, these comments need to be
replaced with fallthrough; in the whole codebase.
Link: https://github.com/KSPP/linux/issues/115
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
While running generic/050 with an external log, I observed this warning
in dmesg:
Trying to write to read-only block-device sda4 (partno 4)
WARNING: CPU: 2 PID: 215677 at block/blk-core.c:704 submit_bio_checks+0x256/0x510
Call Trace:
submit_bio_noacct+0x2c/0x430
_xfs_buf_ioapply+0x283/0x3c0 [xfs]
__xfs_buf_submit+0x6a/0x210 [xfs]
xfs_buf_delwri_submit_buffers+0xf8/0x270 [xfs]
xfsaild+0x2db/0xc50 [xfs]
kthread+0x14b/0x170
I think this happened because we tried to cover the log after a readonly
mount, and the AIL tried to write the primary superblock to the data
device. The test marks the data device readonly, but it doesn't do the
same to the external log device. Therefore, XFS thinks that the log is
writable, even though AIL writes whine to dmesg because the data device
is read only.
Fix this by amending xfs_log_writable to prevent writes when the AIL
can't possible write anything into the filesystem.
Note: As for the external log or the rt devices being readonly--
xfs_blkdev_get will complain about that if we aren't doing a norecovery
mount.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
fs/xfs/xfs_log.c:1062:9-10: WARNING: return of 0/1 in function 'xfs_log_need_covered' with return type bool
Return statements in functions returning bool should use
true/false instead of 1/0.
Generated by: scripts/coccinelle/misc/boolreturn.cocci
Fixes: 37444fc4cc ("xfs: lift writable fs check up into log worker task")
CC: Brian Foster <bfoster@redhat.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: kernel test robot <lkp@intel.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
When CONFIG_XFS_DEBUG=y, set WQ_SYSFS on all workqueues that we create
so that we (developers) have a means to monitor cpu affinity and whatnot
for background workers. In the next patchset we'll expose knobs for
more of the workqueues publicly and document it, but not now.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
The log variable is only used in kernels with asserts enabled.
Remove it and open code the dereference to avoid unused variable
warnings.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
xfs_log_sbcount() calls xfs_sync_sb() to sync superblock counters to
disk when lazy superblock accounting is enabled. This occurs on
unmount, freeze, and read-only (re)mount and ensures the final
values are calculated and persisted to disk before each form of
quiesce completes.
Now that log covering occurs in all of these contexts and uses the
same xfs_sync_sb() mechanism to update log state, there is no need
to log the superblock separately for any reason. Update the log
quiesce path to sync the superblock at least once for any mount
where lazy superblock accounting is enabled. If the log is already
covered, it will remain in the covered state. Otherwise, the next
sync as part of the normal covering sequence will carry the
associated superblock update with it. Remove xfs_log_sbcount() now
that it is no longer needed.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Now that log covering occurs on quiesce, we'd like to reuse the
underlying superblock sync for final superblock updates. This
includes things like lazy superblock counter updates, log feature
incompat bits in the future, etc. One quirk to this approach is that
once the log is in the IDLE (i.e. already covered) state, any
subsequent log write resets the state back to NEED. This means that
a final superblock sync to an already covered log requires two more
sb syncs to return the log back to IDLE again.
For example, if a lazy superblock enabled filesystem is mount cycled
without any modifications, the unmount path syncs the superblock
once and writes an unmount record. With the desired log quiesce
covering behavior, we sync the superblock three times at unmount
time: once for the lazy superblock counter update and twice more to
cover the log. By contrast, if the log is active or only partially
covered at unmount time, a final superblock sync would doubly serve
as the one or two remaining syncs required to cover the log.
This duplicate covering sequence is unnecessary because the
filesystem remains consistent if a crash occurs at any point. The
superblock will either be recovered in the event of a crash or
written back before the log is quiesced and potentially cleaned with
an unmount record.
Update the log covering state machine to remain in the IDLE state if
additional covering checkpoints pass through the log. This
facilitates final superblock updates (such as lazy superblock
counters) via a single sb sync without losing covered status. This
provides some consistency with the active and partially covered
cases and also avoids harmless, but spurious checkpoints when
quiescing the log.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
The log quiesce mechanism historically terminates by marking the log
clean with an unmount record. The primary objective is to indicate
that log recovery is no longer required after the quiesce has
flushed all in-core changes and written back filesystem metadata.
While this is perfectly fine, it is somewhat hacky as currently used
in certain contexts. For example, filesystem freeze quiesces (i.e.
cleans) the log and immediately redirties it with a dummy superblock
transaction to ensure that log recovery runs in the event of a
crash.
While this functions correctly, cleaning the log from freeze context
is clearly superfluous given the current redirtying behavior.
Instead, the desired behavior can be achieved by simply covering the
log. This effectively retires all on-disk log items from the active
range of the log by issuing two synchronous and sequential dummy
superblock update transactions that serve to update the on-disk log
head and tail. The subtle difference is that the log technically
remains dirty due to the lack of an unmount record, though recovery
is effectively a no-op due to the content of the checkpoints being
clean (i.e. the unmodified on-disk superblock).
Log covering currently runs in the background and only triggers once
the filesystem and log has idled. The purpose of the background
mechanism is to prevent log recovery from replaying the most
recently logged items long after those items may have been written
back. In the quiesce path, the log has been deliberately idled by
forcing the log and pushing the AIL until empty in a context where
no further mutable filesystem operations are allowed. Therefore, we
can cover the log as the final step in the log quiesce codepath to
reflect that all previously active items have been successfully
written back.
This facilitates selective log covering from certain contexts (i.e.
freeze) that only seek to quiesce, but not necessarily clean the
log. Note that as a side effect of this change, log covering now
occurs when cleaning the log as well. This is harmless, facilitates
subsequent cleanups, and is mostly temporary as various operations
switch to use explicit log covering.
Signed-off-by: Brian Foster <bfoster@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>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Log quiesce is currently associated with cleaning the log, which is
accomplished by writing an unmount record as the last step of the
quiesce sequence. The quiesce codepath is a bit convoluted in this
regard due to how it is reused from various contexts. In preparation
to create separate log cleaning and log covering interfaces, lift
the write of the unmount record into a new cleaning helper and call
that wherever xfs_log_quiesce() is currently invoked. No functional
changes.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.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 log covering helper checks whether the filesystem is writable to
determine whether to cover the log. The helper is currently only
called from the background log worker. In preparation to reuse the
helper from freezing contexts, lift the check into xfs_log_worker().
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.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_sbcount() syncs the superblock specifically to accumulate
the in-core percpu superblock counters and commit them to disk. This
is required to maintain filesystem consistency across quiesce
(freeze, read-only mount/remount) or unmount when lazy superblock
accounting is enabled because individual transactions do not update
the superblock directly.
This mechanism works as expected for writable mounts, but
xfs_log_sbcount() skips the update for read-only mounts. Read-only
mounts otherwise still allow log recovery and write out an unmount
record during log quiesce. If a read-only mount performs log
recovery, it can modify the in-core superblock counters and write an
unmount record when the filesystem unmounts without ever syncing the
in-core counters. This leaves the filesystem with a clean log but in
an inconsistent state with regard to lazy sb counters.
Update xfs_log_sbcount() to use the same logic
xfs_log_unmount_write() uses to determine when to write an unmount
record. This ensures that lazy accounting is always synced before
the log is cleaned. Refactor this logic into a new helper to
distinguish between a writable filesystem and a writable log.
Specifically, the log is writable unless the filesystem is mounted
with the norecovery mount option, the underlying log device is
read-only, or the filesystem is shutdown. Drop the freeze state
check because the update is already allowed during the freezing
process and no context calls this function on an already frozen fs.
Also, retain the shutdown check in xfs_log_unmount_write() to catch
the case where the preceding log force might have triggered a
shutdown.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Bill O'Donnell <billodo@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Dave Chinner