Skip to content

K
Kernel

openeuler / Kernel
1 年多 前同步成功

通知 8
Star 0
Fork 0
K
Kernel
切换分支/标签
  1. 10 5月, 2018 1 次提交
  3. 10 4月, 2018 1 次提交
  5. 12 3月, 2018 1 次提交
  7. 29 1月, 2018 1 次提交
  9. 10 1月, 2018 1 次提交
  11. 09 1月, 2018 2 次提交
  13. 29 11月, 2017 1 次提交
  15. 02 11月, 2017 1 次提交
  17. 28 10月, 2017 1 次提交
  19. 27 10月, 2017 1 次提交
    • B
      xfs: buffer lru reference count error injection tag · 7561d27e
      由 Brian Foster 提交于 
      XFS uses a fixed reference count for certain types of buffers in the
internal LRU cache. These reference counts dictate how aggressively
certain buffers are reclaimed vs. others. While the reference counts
implements priority across different buffer types, all buffers
(other than uncached buffers) are typically cached for at least one
reclaim cycle.

We've had at least one bug recently that has been hidden by a
released buffer sitting around in the LRU. Users hitting the problem
were able to reproduce under enough memory pressure to cause
aggressive reclaim in a particular window of time.

To support future xfstests cases, add an error injection tag to
hardcode the buffer reference count to zero. When enabled, this
bypasses caching of associated buffers and facilitates test cases
that depend on this behavior.
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
      7561d27e
  21. 26 9月, 2017 1 次提交
  23. 01 9月, 2017 1 次提交
  25. 24 8月, 2017 1 次提交
    • C
      block: replace bi_bdev with a gendisk pointer and partitions index · 74d46992
      由 Christoph Hellwig 提交于 
      This way we don't need a block_device structure to submit I/O.  The
block_device has different life time rules from the gendisk and
request_queue and is usually only available when the block device node
is open.  Other callers need to explicitly create one (e.g. the lightnvm
passthrough code, or the new nvme multipathing code).

For the actual I/O path all that we need is the gendisk, which exists
once per block device.  But given that the block layer also does
partition remapping we additionally need a partition index, which is
used for said remapping in generic_make_request.

Note that all the block drivers generally want request_queue or
sometimes the gendisk, so this removes a layer of indirection all
over the stack.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      74d46992
  27. 20 6月, 2017 1 次提交
    • D
      xfs: remove double-underscore integer types · c8ce540d
      由 Darrick J. Wong 提交于 
      This is a purely mechanical patch that removes the private
__{u,}int{8,16,32,64}_t typedefs in favor of using the system
{u,}int{8,16,32,64}_t typedefs.  This is the sed script used to perform
the transformation and fix the resulting whitespace and indentation
errors:

s/typedef\t__uint8_t/typedef __uint8_t\t/g
s/typedef\t__uint/typedef __uint/g
s/typedef\t__int\([0-9]*\)_t/typedef int\1_t\t/g
s/__uint8_t\t/__uint8_t\t\t/g
s/__uint/uint/g
s/__int\([0-9]*\)_t\t/__int\1_t\t\t/g
s/__int/int/g
/^typedef.*int[0-9]*_t;$/d
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
      c8ce540d
  29. 19 6月, 2017 1 次提交
    • B
      xfs: push buffer of flush locked dquot to avoid quotacheck deadlock · 7912e7fe
      由 Brian Foster 提交于 
      Reclaim during quotacheck can lead to deadlocks on the dquot flush
lock:

 - Quotacheck populates a local delwri queue with the physical dquot
   buffers.
 - Quotacheck performs the xfs_qm_dqusage_adjust() bulkstat and
   dirties all of the dquots.
 - Reclaim kicks in and attempts to flush a dquot whose buffer is
   already queud on the quotacheck queue. The flush succeeds but
   queueing to the reclaim delwri queue fails as the backing buffer is
   already queued. The flush unlock is now deferred to I/O completion
   of the buffer from the quotacheck queue.
 - The dqadjust bulkstat continues and dirties the recently flushed
   dquot once again.
 - Quotacheck proceeds to the xfs_qm_flush_one() walk which requires
   the flush lock to update the backing buffers with the in-core
   recalculated values. It deadlocks on the redirtied dquot as the
   flush lock was already acquired by reclaim, but the buffer resides
   on the local delwri queue which isn't submitted until the end of
   quotacheck.

This is reproduced by running quotacheck on a filesystem with a
couple million inodes in low memory (512MB-1GB) situations. This is
a regression as of commit 43ff2122 ("xfs: on-stack delayed write
buffer lists"), which removed a trylock and buffer I/O submission
from the quotacheck dquot flush sequence.

Quotacheck first resets and collects the physical dquot buffers in a
delwri queue. Then, it traverses the filesystem inodes via bulkstat,
updates the in-core dquots, flushes the corrected dquots to the
backing buffers and finally submits the delwri queue for I/O. Since
the backing buffers are queued across the entire quotacheck
operation, dquot reclaim cannot possibly complete a dquot flush
before quotacheck completes.

Therefore, quotacheck must submit the buffer for I/O in order to
cycle the flush lock and flush the dirty in-core dquot to the
buffer. Add a delwri queue buffer push mechanism to submit an
individual buffer for I/O without losing the delwri queue status and
use it from quotacheck to avoid the deadlock. This restores
quotacheck behavior to as before the regression was introduced.
Reported-by: NMartin Svec <martin.svec@zoner.cz>
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
      7912e7fe
  31. 09 6月, 2017 1 次提交
  33. 08 6月, 2017 1 次提交
  35. 31 5月, 2017 1 次提交
    • B
      xfs: use ->b_state to fix buffer I/O accounting release race · 63db7c81
      由 Brian Foster 提交于 
      We've had user reports of unmount hangs in xfs_wait_buftarg() that
analysis shows is due to btp->bt_io_count == -1. bt_io_count
represents the count of in-flight asynchronous buffers and thus
should always be >= 0. xfs_wait_buftarg() waits for this value to
stabilize to zero in order to ensure that all untracked (with
respect to the lru) buffers have completed I/O processing before
unmount proceeds to tear down in-core data structures.

The value of -1 implies an I/O accounting decrement race. Indeed,
the fact that xfs_buf_ioacct_dec() is called from xfs_buf_rele()
(where the buffer lock is no longer held) means that bp->b_flags can
be updated from an unsafe context. While a user-level reproducer is
currently not available, some intrusive hacks to run racing buffer
lookups/ioacct/releases from multiple threads was used to
successfully manufacture this problem.

Existing callers do not expect to acquire the buffer lock from
xfs_buf_rele(). Therefore, we can not safely update ->b_flags from
this context. It turns out that we already have separate buffer
state bits and associated serialization for dealing with buffer LRU
state in the form of ->b_state and ->b_lock. Therefore, replace the
_XBF_IN_FLIGHT flag with a ->b_state variant, update the I/O
accounting wrappers appropriately and make sure they are used with
the correct locking. This ensures that buffer in-flight state can be
modified at buffer release time without racing with modifications
from a buffer lock holder.

Fixes: 9c7504aa ("xfs: track and serialize in-flight async buffers against unmount")
Cc: <stable@vger.kernel.org> # v4.8+
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Tested-by: NLibor Pechacek <lpechacek@suse.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
      63db7c81
  37. 04 5月, 2017 1 次提交
  39. 26 4月, 2017 1 次提交
  41. 02 3月, 2017 1 次提交
  43. 02 2月, 2017 1 次提交
  45. 26 1月, 2017 1 次提交
    • D
      xfs: clear _XBF_PAGES from buffers when readahead page · 2aa6ba7b
      由 Darrick J. Wong 提交于 
      If we try to allocate memory pages to back an xfs_buf that we're trying
to read, it's possible that we'll be so short on memory that the page
allocation fails.  For a blocking read we'll just wait, but for
readahead we simply dump all the pages we've collected so far.

Unfortunately, after dumping the pages we neglect to clear the
_XBF_PAGES state, which means that the subsequent call to xfs_buf_free
thinks that b_pages still points to pages we own.  It then double-frees
the b_pages pages.

This results in screaming about negative page refcounts from the memory
manager, which xfs oughtn't be triggering.  To reproduce this case,
mount a filesystem where the size of the inodes far outweighs the
availalble memory (a ~500M inode filesystem on a VM with 300MB memory
did the trick here) and run bulkstat in parallel with other memory
eating processes to put a huge load on the system.  The "check summary"
phase of xfs_scrub also works for this purpose.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NEric Sandeen <sandeen@redhat.com>
      2aa6ba7b
  47. 09 12月, 2016 1 次提交
  49. 07 12月, 2016 1 次提交
    • L
      xfs: use rhashtable to track buffer cache · 6031e73a
      由 Lucas Stach 提交于 
      On filesystems with a lot of metadata and in metadata intensive workloads
xfs_buf_find() is showing up at the top of the CPU cycles trace. Most of
the CPU time is spent on CPU cache misses while traversing the rbtree.

As the buffer cache does not need any kind of ordering, but fast lookups
a hashtable is the natural data structure to use. The rhashtable
infrastructure provides a self-scaling hashtable implementation and
allows lookups to proceed while the table is going through a resize
operation.

This reduces the CPU-time spent for the lookups to 1/3 even for small
filesystems with a relatively small number of cached buffers, with
possibly much larger gains on higher loaded filesystems.

[dchinner: reduce minimum hash size to an acceptable size for large
	   filesystems with many AGs with no active use.]
[dchinner: remove stale rbtree asserts.]
[dchinner: use xfs_buf_map for compare function argument.]
[dchinner: make functions static.]
[dchinner: remove redundant comments.]
Signed-off-by: NLucas Stach <dev@lynxeye.de>
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDave Chinner <david@fromorbit.com>
      6031e73a
  51. 01 11月, 2016 1 次提交
  53. 26 8月, 2016 1 次提交
    • B
      xfs: prevent dropping ioend completions during buftarg wait · 800b2694
      由 Brian Foster 提交于 
      xfs_wait_buftarg() waits for all pending I/O, drains the ioend
completion workqueue and walks the LRU until all buffers in the cache
have been released. This is traditionally an unmount operation` but the
mechanism is also reused during filesystem freeze.

xfs_wait_buftarg() invokes drain_workqueue() as part of the quiesce,
which is intended more for a shutdown sequence in that it indicates to
the queue that new operations are not expected once the drain has begun.
New work jobs after this point result in a WARN_ON_ONCE() and are
otherwise dropped.

With filesystem freeze, however, read operations are allowed and can
proceed during or after the workqueue drain. If such a read occurs
during the drain sequence, the workqueue infrastructure complains about
the queued ioend completion work item and drops it on the floor. As a
result, the buffer remains on the LRU and the freeze never completes.

Despite the fact that the overall buffer cache cleanup is not necessary
during freeze, fix up this operation such that it is safe to invoke
during non-unmount quiesce operations. Replace the drain_workqueue()
call with flush_workqueue(), which runs a similar serialization on
pending workqueue jobs without causing new jobs to be dropped. This is
safe for unmount as unmount independently locks out new operations by
the time xfs_wait_buftarg() is invoked.

cc: <stable@vger.kernel.org>
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDave Chinner <david@fromorbit.com>
      800b2694
  55. 17 8月, 2016 1 次提交
    • B
      xfs: don't assert fail on non-async buffers on ioacct decrement · 4dd3fd71
      由 Brian Foster 提交于 
      The buffer I/O accounting mechanism tracks async buffers under I/O.  As
an optimization, the buffer I/O count is incremented only once on the
first async I/O for a given hold cycle of a buffer and decremented once
the buffer is released to the LRU (or freed).

xfs_buf_ioacct_dec() has an ASSERT() check for an XBF_ASYNC buffer, but
we have one or two corner cases where a buffer can be submitted for I/O
multiple times via different methods in a single hold cycle. If an async
I/O occurs first, the I/O count is incremented. If a sync I/O occurs
before the hold count drops, XBF_ASYNC is cleared by the time the I/O
count is decremented.

Remove the async assert check from xfs_buf_ioacct_dec() as this is a
perfectly valid scenario. For the purposes of I/O accounting, we really
only care about the buffer async state at I/O submission time.
Discovered-and-analyzed-by: NDave Chinner <david@fromorbit.com>
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>
      4dd3fd71
  57. 20 7月, 2016 3 次提交
    • B
      xfs: track and serialize in-flight async buffers against unmount · 9c7504aa
      由 Brian Foster 提交于 
      Newly allocated XFS metadata buffers are added to the LRU once the hold
count is released, which typically occurs after I/O completion. There is
no other mechanism at current that tracks the existence or I/O state of
a new buffer. Further, readahead I/O tends to be submitted
asynchronously by nature, which means the I/O can remain in flight and
actually complete long after the calling context is gone. This means
that file descriptors or any other holds on the filesystem can be
released, allowing the filesystem to be unmounted while I/O is still in
flight. When I/O completion occurs, core data structures may have been
freed, causing completion to run into invalid memory accesses and likely
to panic.

This problem is reproduced on XFS via directory readahead. A filesystem
is mounted, a directory is opened/closed and the filesystem immediately
unmounted. The open/close cycle triggers a directory readahead that if
delayed long enough, runs buffer I/O completion after the unmount has
completed.

To address this problem, add a mechanism to track all in-flight,
asynchronous buffers using per-cpu counters in the buftarg. The buffer
is accounted on the first I/O submission after the current reference is
acquired and unaccounted once the buffer is returned to the LRU or
freed. Update xfs_wait_buftarg() to wait on all in-flight I/O before
walking the LRU list. Once in-flight I/O has completed and the workqueue
has drained, all new buffers should have been released onto the LRU.
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>
      9c7504aa
    • B
      xfs: exclude never-released buffers from buftarg I/O accounting · c891c30a
      由 Brian Foster 提交于 
      The upcoming buftarg I/O accounting mechanism maintains a count of
all buffers that have undergone I/O in the current hold-release
cycle.  Certain buffers associated with core infrastructure (e.g.,
the xfs_mount superblock buffer, log buffers) are never released,
however. This means that accounting I/O submission on such buffers
elevates the buftarg count indefinitely and could lead to lockup on
unmount.

Define a new buffer flag to explicitly exclude buffers from buftarg
I/O accounting. Set the flag on the superblock and associated log
buffers.
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>
      c891c30a
    • E
      xfs: remove extraneous buffer flag changes · 0b4db5df
      由 Eric Sandeen 提交于 
      Fix up a couple places where extra flag manipulation occurs.

In the first case we clear XBF_ASYNC and then immediately reset it -
so don't bother clearing in the first place.

In the 2nd case we are at a point in the function where the buffer
must already be async, so there is no need to reset it.

Add consistent spacing around the " | " while we're at it.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Reviewed-by: NCarlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>
      0b4db5df
  59. 21 6月, 2016 1 次提交
  61. 10 6月, 2016 1 次提交
  63. 08 6月, 2016 3 次提交
  65. 01 6月, 2016 1 次提交
    • D
      xfs: reduce lock hold times in buffer writeback · 26f1fe85
      由 Dave Chinner 提交于 
      When we have a lot of metadata to flush from the AIL, the buffer
list can get very long. The current submission code tries to batch
submission to optimise IO order of the metadata (i.e. ascending
block order) to maximise block layer merging or IO to adjacent
metadata blocks.

Unfortunately, the method used can result in long lock times
occurring as buffers locked early on in the buffer list might not be
dispatched until the end of the IO licst processing. This is because
sorting does not occur util after the buffer list has been processed
and the buffers that are going to be submitted are locked. Hence
when the buffer list is several thousand buffers long, the lock hold
times before IO dispatch can be significant.

To fix this, sort the buffer list before we start trying to lock and
submit buffers. This means we can now submit buffers immediately
after they are locked, allowing merging to occur immediately on the
plug and dispatch to occur as quickly as possible. This means there
is minimal delay between locking the buffer and IO submission
occuring, hence reducing the worst case lock hold times seen during
delayed write buffer IO submission signficantly.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NCarlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>
      26f1fe85
  67. 18 5月, 2016 1 次提交
    • B
      xfs: buffer ->bi_end_io function requires irq-safe lock · 9bdd9bd6
      由 Brian Foster 提交于 
      Reports have surfaced of a lockdep splat complaining about an
irq-safe -> irq-unsafe locking order in the xfs_buf_bio_end_io() bio
completion handler. This only occurs when I/O errors are present
because bp->b_lock is only acquired in this context to protect
setting an error on the buffer. The problem is that this lock can be
acquired with the (request_queue) q->queue_lock held. See
scsi_end_request() or ata_qc_schedule_eh(), for example.

Replace the locked test/set of b_io_error with a cmpxchg() call.
This eliminates the need for the lock and thus the lock ordering
problem goes away.
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>
      9bdd9bd6
  69. 10 2月, 2016 1 次提交