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fallocate unshare mode explicitly breaks extent sharing. When a
command completes, it checks the data fork for any remaining shared
extents to determine whether the reflink inode flag and COW fork
preallocation can be removed. This logic doesn't consider in-core
pagecache and I/O state, however, which means we can unsafely remove
COW fork blocks that are still needed under certain conditions.
For example, consider the following command sequence:
xfs_io -fc "pwrite 0 1k" -c "reflink <file> 0 256k 1k" \
-c "pwrite 0 32k" -c "funshare 0 1k" <file>
This allocates a data block at offset 0, shares it, and then
overwrites it with a larger buffered write. The overwrite triggers
COW fork preallocation, 32 blocks by default, which maps the entire
32k write to delalloc in the COW fork. All but the shared block at
offset 0 remains hole mapped in the data fork. The unshare command
redirties and flushes the folio at offset 0, removing the only
shared extent from the inode. Since the inode no longer maps shared
extents, unshare purges the COW fork before the remaining 28k may
have written back.
This leaves dirty pagecache backed by holes, which writeback quietly
skips, thus leaving clean, non-zeroed pagecache over holes in the
file. To verify, fiemap shows holes in the first 32k of the file and
reads return different data across a remount:
$ xfs_io -c "fiemap -v" <file>
<file>:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
...
1: [8..511]: hole 504
...
$ xfs_io -c "pread -v 4k 8" <file>
00001000: cd cd cd cd cd cd cd cd ........
$ umount <mnt>; mount <dev> <mnt>
$ xfs_io -c "pread -v 4k 8" <file>
00001000: 00 00 00 00 00 00 00 00 ........
To avoid this problem, make unshare follow the same rules used for
background cowblock scanning and never purge the COW fork for inodes
with dirty pagecache or in-flight I/O.
Fixes: 46afb0628b86347 ("xfs: only flush the unshared range in xfs_reflink_unshare")
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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The background blockgc scanner runs on a 5m interval by default and
trims preallocation (post-eof and cow fork) from inodes that are
otherwise idle. Idle effectively means that iolock can be acquired
without blocking and that the inode has no dirty pagecache or I/O in
flight.
This simple mechanism and heuristic has worked fairly well for
post-eof speculative preallocations. Support for reflink and COW
fork preallocations came sometime later and plugged into the same
mechanism, with similar heuristics. Some recent testing has shown
that COW fork preallocation may be notably more sensitive to blockgc
processing than post-eof preallocation, however.
For example, consider an 8GB reflinked file with a COW extent size
hint of 1MB. A worst case fully randomized overwrite of this file
results in ~8k extents of an average size of ~1MB. If the same
workload is interrupted a couple times for blockgc processing
(assuming the file goes idle), the resulting extent count explodes
to over 100k extents with an average size <100kB. This is
significantly worse than ideal and essentially defeats the COW
extent size hint mechanism.
While this particular test is instrumented, it reflects a fairly
reasonable pattern in practice where random I/Os might spread out
over a large period of time with varying periods of (in)activity.
For example, consider a cloned disk image file for a VM or container
with long uptime and variable and bursty usage. A background blockgc
scan that races and processes the image file when it happens to be
clean and idle can have a significant effect on the future
fragmentation level of the file, even when still in use.
To help combat this, update the heuristic to skip cowblocks inodes
that are currently opened for write access during non-sync blockgc
scans. This allows COW fork preallocations to persist for as long as
possible unless otherwise needed for functional purposes (i.e. a
sync scan), the file is idle and closed, or the inode is being
evicted from cache. While here, update the comments to help
distinguish performance oriented heuristics from the logic that
exists to maintain functional correctness.
Suggested-by: Darrick Wong <djwong@kernel.org>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs
Pull vfs blocksize updates from Christian Brauner:
"This contains the vfs infrastructure as well as the xfs bits to enable
support for block sizes (bs) larger than page sizes (ps) plus a few
fixes to related infrastructure.
There has been efforts over the last 16 years to enable enable Large
Block Sizes (LBS), that is block sizes in filesystems where bs > page
size. Through these efforts we have learned that one of the main
blockers to supporting bs > ps in filesystems has been a way to
allocate pages that are at least the filesystem block size on the page
cache where bs > ps.
Thanks to various previous efforts it is possible to support bs > ps
in XFS with only a few changes in XFS itself. Most changes are to the
page cache to support minimum order folio support for the target block
size on the filesystem.
A motivation for Large Block Sizes today is to support high-capacity
(large amount of Terabytes) QLC SSDs where the internal Indirection
Unit (IU) are typically greater than 4k to help reduce DRAM and so in
turn cost and space. In practice this then allows different
architectures to use a base page size of 4k while still enabling
support for block sizes aligned to the larger IUs by relying on high
order folios on the page cache when needed.
It also allows to take advantage of the drive's support for atomics
larger than 4k with buffered IO support in Linux. As described this
year at LSFMM, supporting large atomics greater than 4k enables
databases to remove the need to rely on their own journaling, so they
can disable double buffered writes, which is a feature different cloud
providers are already enabling through custom storage solutions"
* tag 'vfs-6.12.blocksize' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs: (22 commits)
Documentation: iomap: fix a typo
iomap: remove the iomap_file_buffered_write_punch_delalloc return value
iomap: pass the iomap to the punch callback
iomap: pass flags to iomap_file_buffered_write_punch_delalloc
iomap: improve shared block detection in iomap_unshare_iter
iomap: handle a post-direct I/O invalidate race in iomap_write_delalloc_release
docs:filesystems: fix spelling and grammar mistakes in iomap design page
filemap: fix htmldoc warning for mapping_align_index()
iomap: make zero range flush conditional on unwritten mappings
iomap: fix handling of dirty folios over unwritten extents
iomap: add a private argument for iomap_file_buffered_write
iomap: remove set_memor_ro() on zero page
xfs: enable block size larger than page size support
xfs: make the calculation generic in xfs_sb_validate_fsb_count()
xfs: expose block size in stat
xfs: use kvmalloc for xattr buffers
iomap: fix iomap_dio_zero() for fs bs > system page size
filemap: cap PTE range to be created to allowed zero fill in folio_map_range()
mm: split a folio in minimum folio order chunks
readahead: allocate folios with mapping_min_order in readahead
...
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Page cache now has the ability to have a minimum order when allocating
a folio which is a prerequisite to add support for block size > page
size.
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20240827-xfs-fix-wformat-bs-gt-ps-v1-1-aec6717609e0@kernel.org # fix folded
Link: https://lore.kernel.org/r/20240822135018.1931258-11-kernel@pankajraghav.com
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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xfs_reclaim_inodes_count iterates over all AGs to sum up the reclaimable
inodes counts. There is no point in grabbing a reference to the them or
unlock the RCU critical section for each iteration, so switch to the
more efficient xas_for_each_marked iterator.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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Convert the perag lookup from the legacy radix tree to the xarray,
which allows for much nicer iteration and bulk lookup semantics.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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Pass the old perag structure to the tagged loop helpers so that they can
grab the old agno before releasing the reference. This removes the need
to separately track the agno and the iterator macro, and thus also
obsoletes the for_each_perag_tag syntactic sugar.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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The tagged perag helpers are only used in xfs_icache.c in the kernel code
and not at all in xfsprogs. Move them to xfs_icache.c in preparation for
switching to an xarray, for which I have no plan to implement the tagged
lookup functions for userspace.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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The XFS XFS_DIFLAG_APPEND maps to the VFS S_APPEND flag, which forbids
writes that don't append at the current EOF.
But the commit originally adding XFS_DIFLAG_APPEND support (commit
a23321e766d in xfs xfs-import repository) also checked it to skip
releasing speculative preallocations, which doesn't make any sense.
Another commit (dd9f438e3290 in the xfs-import repository) later extended
that flag to also report these speculation preallocations which should
not exist in getbmap.
Remove these checks as nothing XFS_DIFLAG_APPEND implies that
preallocations beyond EOF should exist, but explicitly check for
XFS_DIFLAG_APPEND in xfs_file_release to bypass the algorithm that
discard preallocations on the first close as append only files aren't
expected to be written to only once.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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Actually use the inumber validator to check the argument passed in here.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs inode / dentry updates from Christian Brauner:
"This contains smaller performance improvements to inodes and dentries:
inode:
- Add rcu based inode lookup variants.
They avoid one inode hash lock acquire in the common case thereby
significantly reducing contention. We already support RCU-based
operations but didn't take advantage of them during inode
insertion.
Callers of iget_locked() get the improvement without any code
changes. Callers that need a custom callback can switch to
iget5_locked_rcu() as e.g., did btrfs.
With 20 threads each walking a dedicated 1000 dirs * 1000 files
directory tree to stat(2) on a 32 core + 24GB ram vm:
before: 3.54s user 892.30s system 1966% cpu 45.549 total
after: 3.28s user 738.66s system 1955% cpu 37.932 total (-16.7%)
Long-term we should pick up the effort to introduce more
fine-grained locking and possibly improve on the currently used
hash implementation.
- Start zeroing i_state in inode_init_always() instead of doing it in
individual filesystems.
This allows us to remove an unneeded lock acquire in new_inode()
and not burden individual filesystems with this.
dcache:
- Move d_lockref out of the area used by RCU lookup to avoid
cacheline ping poing because the embedded name is sharing a
cacheline with d_lockref.
- Fix dentry size on 32bit with CONFIG_SMP=y so it does actually end
up with 128 bytes in total"
* tag 'vfs-6.11.inode' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
fs: fix dentry size
vfs: move d_lockref out of the area used by RCU lookup
bcachefs: remove now spurious i_state initialization
xfs: remove now spurious i_state initialization in xfs_inode_alloc
vfs: partially sanitize i_state zeroing on inode creation
xfs: preserve i_state around inode_init_always in xfs_reinit_inode
btrfs: use iget5_locked_rcu
vfs: add rcu-based find_inode variants for iget ops
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xfs_can_free_eofblocks returns false for files that have persistent
preallocations unless the force flag is passed and there are delayed
blocks. This means it won't free delalloc reservations for files
with persistent preallocations unless the force flag is set, and it
will also free the persistent preallocations if the force flag is
set and the file happens to have delayed allocations.
Both of these are bad, so do away with the force flag and always free
only post-EOF delayed allocations for files with the XFS_DIFLAG_PREALLOC
or APPEND flags set.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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inode_init_always started setting the field to 0.
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20240611120626.513952-4-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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This is in preparation for the routine starting to zero the field.
De facto coded by Dave Chinner, see:
https://lore.kernel.org/linux-fsdevel/ZmgtaGglOL33Wkzr@dread.disaster.area/
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20240611120626.513952-2-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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xfs_inode.i_flags is an unsigned long, so make these helpers take that
as the flags argument instead of unsigned short. This is needed for the
next patch.
While we're at it, remove the iflags variable from xfs_iget_cache_miss
because we no longer need it.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
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syzbot reported an ext4 panic during a page fault where found a
journal handle when it didn't expect to find one. The structure
it tripped over had a value of 'TRAN' in the first entry in the
structure, and that indicates it tripped over a struct xfs_trans
instead of a jbd2 handle.
The reason for this is that the page fault was taken during a
copy-out to a user buffer from an xfs bulkstat operation. XFS uses
an "empty" transaction context for bulkstat to do automated metadata
buffer cleanup, and so the transaction context is valid across the
copyout of the bulkstat info into the user buffer.
We are using empty transaction contexts like this in XFS to reduce
the risk of failing to release objects we reference during the
operation, especially during error handling. Hence we really need to
ensure that we can take page faults from these contexts without
leaving landmines for the code processing the page fault to trip
over.
However, this same behaviour could happen from any other filesystem
that triggers a page fault or any other exception that is handled
on-stack from within a task context that has current->journal_info
set. Having a page fault from some other filesystem bounce into XFS
where we have to run a transaction isn't a bug at all, but the usage
of current->journal_info means that this could result corruption of
the outer task's journal_info structure.
The problem is purely that we now have two different contexts that
now think they own current->journal_info. IOWs, no filesystem can
allow page faults or on-stack exceptions while current->journal_info
is set by the filesystem because the exception processing might use
current->journal_info itself.
If we end up with nested XFS transactions whilst holding an empty
transaction, then it isn't an issue as the outer transaction does
not hold a log reservation. If we ignore the current->journal_info
usage, then the only problem that might occur is a deadlock if the
exception tries to take the same locks the upper context holds.
That, however, is not a problem that setting current->journal_info
would solve, so it's largely an irrelevant concern here.
IOWs, we really only use current->journal_info for a warning check
in xfs_vm_writepages() to ensure we aren't doing writeback from a
transaction context. Writeback might need to do allocation, so it
can need to run transactions itself. Hence it's a debug check to
warn us that we've done something silly, and largely it is not all
that useful.
So let's just remove all the use of current->journal_info in XFS and
get rid of all the potential issues from nested contexts where
current->journal_info might get misused by another filesystem
context.
Reported-by: syzbot+cdee56dbcdf0096ef605@syzkaller.appspotmail.com
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Mark Tinguely <mark.tinguely@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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Whenever we encounter corrupt inode records, we should report that to
the health monitoring system for later reporting.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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In the past we've had problems with lockdep false positives stemming
from inode locking occurring in memory reclaim contexts (e.g. from
superblock shrinkers). Lockdep doesn't know that inodes access from
above memory reclaim cannot be accessed from below memory reclaim
(and vice versa) but there has never been a good solution to solving
this problem with lockdep annotations.
This situation isn't unique to inode locks - buffers are also locked
above and below memory reclaim, and we have to maintain lock
ordering for them - and against inodes - appropriately. IOWs, the
same code paths and locks are taken both above and below memory
reclaim and so we always need to make sure the lock orders are
consistent. We are spared the lockdep problems this might cause
by the fact that semaphores and bit locks aren't covered by lockdep.
In general, this sort of lockdep false positive detection is cause
by code that runs GFP_KERNEL memory allocation with an actively
referenced inode locked. When it is run from a transaction, memory
allocation is automatically GFP_NOFS, so we don't have reclaim
recursion issues. So in the places where we do memory allocation
with inodes locked outside of a transaction, we have explicitly set
them to use GFP_NOFS allocations to prevent lockdep false positives
from being reported if the allocation dips into direct memory
reclaim.
More recently, __GFP_NOLOCKDEP was added to the memory allocation
flags to tell lockdep not to track that particular allocation for
the purposes of reclaim recursion detection. This is a much better
way of preventing false positives - it allows us to use GFP_KERNEL
context outside of transactions, and allows direct memory reclaim to
proceed normally without throwing out false positive deadlock
warnings.
The obvious places that lock inodes and do memory allocation are the
lookup paths and inode extent list initialisation. These occur in
non-transactional GFP_KERNEL contexts, and so can run direct reclaim
and lock inodes.
This patch makes a first path through all the explicit GFP_NOFS
allocations in XFS and converts the obvious ones to GFP_KERNEL |
__GFP_NOLOCKDEP as a first step towards removing explicit GFP_NOFS
allocations from the XFS code.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the xfs-inodegc shrinker, so that it can be freed
asynchronously via RCU. Then it doesn't need to wait for RCU read-side
critical section when releasing the struct xfs_mount.
Link: https://lkml.kernel.org/r/20230911094444.68966-36-zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Chandan Babu R <chandan.babu@oracle.com>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Anna Schumaker <anna@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Carlos Llamas <cmllamas@google.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Chris Mason <clm@fb.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: Chuck Lever <cel@kernel.org>
Cc: Coly Li <colyli@suse.de>
Cc: Dai Ngo <Dai.Ngo@oracle.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Airlie <airlied@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Gao Xiang <hsiangkao@linux.alibaba.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jeffle Xu <jefflexu@linux.alibaba.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Kirill Tkhai <tkhai@ya.ru>
Cc: Marijn Suijten <marijn.suijten@somainline.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Mike Snitzer <snitzer@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nadav Amit <namit@vmware.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Olga Kornievskaia <kolga@netapp.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sean Paul <sean@poorly.run>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Song Liu <song@kernel.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: Yue Hu <huyue2@coolpad.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Alter the definition of i_prev_unlinked slightly to make it more obvious
when an inode with 0 link count is not part of the iunlink bucket lists
rooted in the AGI. This distinction is necessary because it is not
sufficient to check inode.i_nlink to decide if an inode is on the
unlinked list. Updates to i_nlink can happen while holding only
ILOCK_EXCL, but updates to an inode's position in the AGI unlinked list
(which happen after the nlink update) requires both ILOCK_EXCL and the
AGI buffer lock.
The next few patches will make it possible to reload an entire unlinked
bucket list when we're walking the inode table or performing handle
operations and need more than the ability to iget the last inode in the
chain.
The upcoming directory repair code also needs to be able to make this
distinction to decide if a zero link count directory should be moved to
the orphanage or allowed to inactivate. An upcoming enhancement to the
online AGI fsck code will need this distinction to check and rebuild the
AGI unlinked buckets.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Directly track which CPUs have contributed to the inodegc percpu lists
instead of trusting the cpu online mask. This eliminates a theoretical
problem where the inodegc flush functions might fail to flush a CPU's
inodes if that CPU happened to be dying at exactly the same time. Most
likely nobody's noticed this because the CPU dead hook moves the percpu
inodegc list to another CPU and schedules that worker immediately. But
it's quite possible that this is a subtle race leading to UAF if the
inodegc flush were part of an unmount.
Further benefits: This reduces the overhead of the inodegc flush code
slightly by allowing us to ignore CPUs that have empty lists. Better
yet, it reduces our dependence on the cpu online masks, which have been
the cause of confusion and drama lately.
Fixes: ab23a7768739 ("xfs: per-cpu deferred inode inactivation queues")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
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This function is only used by online fsck, so let's move it there.
In the next patch, we'll fix it to work properly and to require that the
caller hold the AGI buffer locked. No major changes aside from
adjusting the signature a bit.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
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Unlinked list recovery requires errors removing the inode the from
the unlinked list get fed back to the main recovery loop. Now that
we offload the unlinking to the inodegc work, we don't get errors
being fed back when we trip over a corruption that prevents the
inode from being removed from the unlinked list.
This means we never clear the corrupt unlinked list bucket,
resulting in runtime operations eventually tripping over it and
shutting down.
Fix this by collecting inodegc worker errors and feed them
back to the flush caller. This is largely best effort - the only
context that really cares is log recovery, and it only flushes a
single inode at a time so we don't need complex synchronised
handling. Essentially the inodegc workers will capture the first
error that occurs and the next flush will gather them and clear
them. The flush itself will only report the first gathered error.
In the cases where callers can return errors, propagate the
collected inodegc flush error up the error handling chain.
In the case of inode unlinked list recovery, there are several
superfluous calls to flush queued unlinked inodes -
xlog_recover_iunlink_bucket() guarantees that it has flushed the
inodegc and collected errors before it returns. Hence nothing in the
calling path needs to run a flush, even when an error is returned.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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syzbot reported this warning from the faux inodegc shrinker that tries
to kick off inodegc work:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 102 at kernel/workqueue.c:1445 __queue_work+0xd44/0x1120 kernel/workqueue.c:1444
RIP: 0010:__queue_work+0xd44/0x1120 kernel/workqueue.c:1444
Call Trace:
__queue_delayed_work+0x1c8/0x270 kernel/workqueue.c:1672
mod_delayed_work_on+0xe1/0x220 kernel/workqueue.c:1746
xfs_inodegc_shrinker_scan fs/xfs/xfs_icache.c:2212 [inline]
xfs_inodegc_shrinker_scan+0x250/0x4f0 fs/xfs/xfs_icache.c:2191
do_shrink_slab+0x428/0xaa0 mm/vmscan.c:853
shrink_slab+0x175/0x660 mm/vmscan.c:1013
shrink_one+0x502/0x810 mm/vmscan.c:5343
shrink_many mm/vmscan.c:5394 [inline]
lru_gen_shrink_node mm/vmscan.c:5511 [inline]
shrink_node+0x2064/0x35f0 mm/vmscan.c:6459
kswapd_shrink_node mm/vmscan.c:7262 [inline]
balance_pgdat+0xa02/0x1ac0 mm/vmscan.c:7452
kswapd+0x677/0xd60 mm/vmscan.c:7712
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
This warning corresponds to this code in __queue_work:
/*
* For a draining wq, only works from the same workqueue are
* allowed. The __WQ_DESTROYING helps to spot the issue that
* queues a new work item to a wq after destroy_workqueue(wq).
*/
if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq))))
return;
For this to trip, we must have a thread draining the inodedgc workqueue
and a second thread trying to queue inodegc work to that workqueue.
This can happen if freezing or a ro remount race with reclaim poking our
faux inodegc shrinker and another thread dropping an unlinked O_RDONLY
file:
Thread 0 Thread 1 Thread 2
xfs_inodegc_stop
xfs_inodegc_shrinker_scan
xfs_is_inodegc_enabled
<yes, will continue>
xfs_clear_inodegc_enabled
xfs_inodegc_queue_all
<list empty, do not queue inodegc worker>
xfs_inodegc_queue
<add to list>
xfs_is_inodegc_enabled
<no, returns>
drain_workqueue
<set WQ_DRAINING>
llist_empty
<no, will queue list>
mod_delayed_work_on(..., 0)
__queue_work
<sees WQ_DRAINING, kaboom>
In other words, everything between the access to inodegc_enabled state
and the decision to poke the inodegc workqueue requires some kind of
coordination to avoid the WQ_DRAINING state. We could perhaps introduce
a lock here, but we could also try to eliminate WQ_DRAINING from the
picture.
We could replace the drain_workqueue call with a loop that flushes the
workqueue and queues workers as long as there is at least one inode
present in the per-cpu inodegc llists. We've disabled inodegc at this
point, so we know that the number of queued inodes will eventually hit
zero as long as xfs_inodegc_start cannot reactivate the workers.
There are four callers of xfs_inodegc_start. Three of them come from the
VFS with s_umount held: filesystem thawing, failed filesystem freezing,
and the rw remount transition. The fourth caller is mounting rw (no
remount or freezing possible).
There are three callers ofs xfs_inodegc_stop. One is unmounting (no
remount or thaw possible). Two of them come from the VFS with s_umount
held: fs freezing and ro remount transition.
Hence, it is correct to replace the drain_workqueue call with a loop
that drains the inodegc llists.
Fixes: 6191cf3ad59f ("xfs: flush inodegc workqueue tasks before cancel")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Now that we've allegedly worked out the problem of the per-cpu inodegc
workers being scheduled on the wrong cpu, let's put in a debugging knob
to let us know if a worker ever gets mis-scheduled again.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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I've been noticing odd racing behavior in the inodegc code that could
only be explained by one cpu adding an inode to its inactivation llist
at the same time that another cpu is processing that cpu's llist.
Preemption is disabled between get/put_cpu_ptr, so the only explanation
is scheduler mayhem. I inserted the following debug code into
xfs_inodegc_worker (see the next patch):
ASSERT(gc->cpu == smp_processor_id());
This assertion tripped during overnight tests on the arm64 machines, but
curiously not on x86_64. I think we haven't observed any resource leaks
here because the lockfree list code can handle simultaneous llist_add
and llist_del_all functions operating on the same list. However, the
whole point of having percpu inodegc lists is to take advantage of warm
memory caches by inactivating inodes on the last processor to touch the
inode.
The incorrect scheduling seems to occur after an inodegc worker is
subjected to mod_delayed_work(). This wraps mod_delayed_work_on with
WORK_CPU_UNBOUND specified as the cpu number. Unbound allows for
scheduling on any cpu, not necessarily the same one that scheduled the
work.
Because preemption is disabled for as long as we have the gc pointer, I
think it's safe to use current_cpu() (aka smp_processor_id) to queue the
delayed work item on the correct cpu.
Fixes: 7cf2b0f9611b ("xfs: bound maximum wait time for inodegc work")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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In commit d658e, we tried to improve the robustnes of xchk_get_inode in
the face of EINVAL returns from iget by calling xfs_imap to see if the
inobt itself thinks that the inode is allocated. Unfortunately, that
commit didn't consider the possibility that the inode gets allocated
after iget but before imap. In this case, the imap call will succeed,
but we turn that into a corruption error and tell userspace the inode is
corrupt.
Avoid this false corruption report by grabbing the AGI header and
retrying the iget before calling imap. If the iget succeeds, we can
proceed with the usual scrub-by-handle code. Fix all the incorrect
comments too, since unreadable/corrupt inodes no longer result in EINVAL
returns.
Fixes: d658e72b4a09 ("xfs: distinguish between corrupt inode and invalid inum in xfs_scrub_get_inode")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
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Callers have referenced perags but they don't pass it into
xfs_imap() so it takes it's own reference. Fix that so we can change
inode allocation over to using active references.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
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So that they all output the same information in the traces to make
debugging refcount issues easier.
This means that all the lookup/drop functions no longer need to use
the full memory barrier atomic operations (atomic*_return()) so
will have less overhead when tracing is off. The set/clear tag
tracepoints no longer abuse the reference count to pass the tag -
the tag being cleared is obvious from the _RET_IP_ that is recorded
in the trace point.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
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We need to be able to dynamically remove instantiated AGs from
memory safely, either for shrinking the filesystem or paging AG
state in and out of memory (e.g. supporting millions of AGs). This
means we need to be able to safely exclude operations from accessing
perags while dynamic removal is in progress.
To do this, introduce the concept of active and passive references.
Active references are required for high level operations that make
use of an AG for a given operation (e.g. allocation) and pin the
perag in memory for the duration of the operation that is operating
on the perag (e.g. transaction scope). This means we can fail to get
an active reference to an AG, hence callers of the new active
reference API must be able to handle lookup failure gracefully.
Passive references are used in low level code, where we might need
to access the perag structure for the purposes of completing high
level operations. For example, buffers need to use passive
references because:
- we need to be able to do metadata IO during operations like grow
and shrink transactions where high level active references to the
AG have already been blocked
- buffers need to pin the perag until they are reclaimed from
memory, something that high level code has no direct control over.
- unused cached buffers should not prevent a shrink from being
started.
Hence we have active references that will form exclusion barriers
for operations to be performed on an AG, and passive references that
will prevent reclaim of the perag until all objects with passive
references have been reclaimed themselves.
This patch introduce xfs_perag_grab()/xfs_perag_rele() as the API
for active AG reference functionality. We also need to convert the
for_each_perag*() iterators to use active references, which will
start the process of converting high level code over to using active
references. Conversion of non-iterator based code to active
references will be done in followup patches.
Note that the implementation using reference counting is really just
a development vehicle for the API to ensure we don't have any leaks
in the callers. Once we need to remove perag structures from memory
dyanmically, we will need a much more robust per-ag state transition
mechanism for preventing new references from being taken while we
wait for existing references to drain before removal from memory can
occur....
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
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|
We are doing a test about deleting a large number of files
when memory is low. A deadlock problem was found.
[ 1240.279183] -> #1 (fs_reclaim){+.+.}-{0:0}:
[ 1240.280450] lock_acquire+0x197/0x460
[ 1240.281548] fs_reclaim_acquire.part.0+0x20/0x30
[ 1240.282625] kmem_cache_alloc+0x2b/0x940
[ 1240.283816] xfs_trans_alloc+0x8a/0x8b0
[ 1240.284757] xfs_inactive_ifree+0xe4/0x4e0
[ 1240.285935] xfs_inactive+0x4e9/0x8a0
[ 1240.286836] xfs_inodegc_worker+0x160/0x5e0
[ 1240.287969] process_one_work+0xa19/0x16b0
[ 1240.289030] worker_thread+0x9e/0x1050
[ 1240.290131] kthread+0x34f/0x460
[ 1240.290999] ret_from_fork+0x22/0x30
[ 1240.291905]
[ 1240.291905] -> #0 ((work_completion)(&gc->work)){+.+.}-{0:0}:
[ 1240.293569] check_prev_add+0x160/0x2490
[ 1240.294473] __lock_acquire+0x2c4d/0x5160
[ 1240.295544] lock_acquire+0x197/0x460
[ 1240.296403] __flush_work+0x6bc/0xa20
[ 1240.297522] xfs_inode_mark_reclaimable+0x6f0/0xdc0
[ 1240.298649] destroy_inode+0xc6/0x1b0
[ 1240.299677] dispose_list+0xe1/0x1d0
[ 1240.300567] prune_icache_sb+0xec/0x150
[ 1240.301794] super_cache_scan+0x2c9/0x480
[ 1240.302776] do_shrink_slab+0x3f0/0xaa0
[ 1240.303671] shrink_slab+0x170/0x660
[ 1240.304601] shrink_node+0x7f7/0x1df0
[ 1240.305515] balance_pgdat+0x766/0xf50
[ 1240.306657] kswapd+0x5bd/0xd20
[ 1240.307551] kthread+0x34f/0x460
[ 1240.308346] ret_from_fork+0x22/0x30
[ 1240.309247]
[ 1240.309247] other info that might help us debug this:
[ 1240.309247]
[ 1240.310944] Possible unsafe locking scenario:
[ 1240.310944]
[ 1240.312379] CPU0 CPU1
[ 1240.313363] ---- ----
[ 1240.314433] lock(fs_reclaim);
[ 1240.315107] lock((work_completion)(&gc->work));
[ 1240.316828] lock(fs_reclaim);
[ 1240.318088] lock((work_completion)(&gc->work));
[ 1240.319203]
[ 1240.319203] *** DEADLOCK ***
...
[ 2438.431081] Workqueue: xfs-inodegc/sda xfs_inodegc_worker
[ 2438.432089] Call Trace:
[ 2438.432562] __schedule+0xa94/0x1d20
[ 2438.435787] schedule+0xbf/0x270
[ 2438.436397] schedule_timeout+0x6f8/0x8b0
[ 2438.445126] wait_for_completion+0x163/0x260
[ 2438.448610] __flush_work+0x4c4/0xa40
[ 2438.455011] xfs_inode_mark_reclaimable+0x6ef/0xda0
[ 2438.456695] destroy_inode+0xc6/0x1b0
[ 2438.457375] dispose_list+0xe1/0x1d0
[ 2438.458834] prune_icache_sb+0xe8/0x150
[ 2438.461181] super_cache_scan+0x2b3/0x470
[ 2438.461950] do_shrink_slab+0x3cf/0xa50
[ 2438.462687] shrink_slab+0x17d/0x660
[ 2438.466392] shrink_node+0x87e/0x1d40
[ 2438.467894] do_try_to_free_pages+0x364/0x1300
[ 2438.471188] try_to_free_pages+0x26c/0x5b0
[ 2438.473567] __alloc_pages_slowpath.constprop.136+0x7aa/0x2100
[ 2438.482577] __alloc_pages+0x5db/0x710
[ 2438.485231] alloc_pages+0x100/0x200
[ 2438.485923] allocate_slab+0x2c0/0x380
[ 2438.486623] ___slab_alloc+0x41f/0x690
[ 2438.490254] __slab_alloc+0x54/0x70
[ 2438.491692] kmem_cache_alloc+0x23e/0x270
[ 2438.492437] xfs_trans_alloc+0x88/0x880
[ 2438.493168] xfs_inactive_ifree+0xe2/0x4e0
[ 2438.496419] xfs_inactive+0x4eb/0x8b0
[ 2438.497123] xfs_inodegc_worker+0x16b/0x5e0
[ 2438.497918] process_one_work+0xbf7/0x1a20
[ 2438.500316] worker_thread+0x8c/0x1060
[ 2438.504938] ret_from_fork+0x22/0x30
When the memory is insufficient, xfs_inonodegc_worker will trigger memory
reclamation when memory is allocated, then flush_work() may be called to
wait for the work to complete. This causes a deadlock.
So use memalloc_nofs_save() to avoid triggering memory reclamation in
xfs_inodegc_worker.
Signed-off-by: Wu Guanghao <wuguanghao3@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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The following error occurred during the fsstress test:
XFS: Assertion failed: VFS_I(ip)->i_nlink >= 2, file: fs/xfs/xfs_inode.c, line: 2452
The problem was that inode race condition causes incorrect i_nlink to be
written to disk, and then it is read into memory. Consider the following
call graph, inodes that are marked as both XFS_IFLUSHING and
XFS_IRECLAIMABLE, i_nlink will be reset to 1 and then restored to original
value in xfs_reinit_inode(). Therefore, the i_nlink of directory on disk
may be set to 1.
xfsaild
xfs_inode_item_push
xfs_iflush_cluster
xfs_iflush
xfs_inode_to_disk
xfs_iget
xfs_iget_cache_hit
xfs_iget_recycle
xfs_reinit_inode
inode_init_always
xfs_reinit_inode() needs to hold the ILOCK_EXCL as it is changing internal
inode state and can race with other RCU protected inode lookups. On the
read side, xfs_iflush_cluster() grabs the ILOCK_SHARED while under rcu +
ip->i_flags_lock, and so xfs_iflush/xfs_inode_to_disk() are protected from
racing inode updates (during transactions) by that lock.
Fixes: ff7bebeb91f8 ("xfs: refactor the inode recycling code") # goes further back than this
Signed-off-by: Long Li <leo.lilong@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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The prandom_u32() function has been a deprecated inline wrapper around
get_random_u32() for several releases now, and compiles down to the
exact same code. Replace the deprecated wrapper with a direct call to
the real function. The same also applies to get_random_int(), which is
just a wrapper around get_random_u32(). This was done as a basic find
and replace.
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz> # for ext4
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk> # for sch_cake
Acked-by: Chuck Lever <chuck.lever@oracle.com> # for nfsd
Acked-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com> # for thunderbolt
Acked-by: Darrick J. Wong <djwong@kernel.org> # for xfs
Acked-by: Helge Deller <deller@gmx.de> # for parisc
Acked-by: Heiko Carstens <hca@linux.ibm.com> # for s390
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
"Most of the MM queue. A few things are still pending.
Liam's maple tree rework didn't make it. This has resulted in a few
other minor patch series being held over for next time.
Multi-gen LRU still isn't merged as we were waiting for mapletree to
stabilize. The current plan is to merge MGLRU into -mm soon and to
later reintroduce mapletree, with a view to hopefully getting both
into 6.1-rc1.
Summary:
|
