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Pull fscrypt updates from Eric Biggers:
"The main change this cycle is a significant simplification that's been
overdue for a while now: standardizing on a single file contents
encryption implementation in ext4 and f2fs, instead of having two.
Specifically, the original filesystem-layer file contents encryption
implementation is removed, and the blk-crypto implementation is now
used unconditionally. blk-crypto delegates either to inline crypto
hardware or to the CPU via blk-crypto-fallback. The latter is
functionally equivalent to the original filesystem-layer code.
The blk-crypto implementation already existed, but previously it was
used only when the filesystem was mounted with "-o inlinecrypt". Now,
"-o inlinecrypt" just selects whether inline crypto hardware is used.
To allow maintaining that user control over hardware use, the
blk-crypto API is extended with a new flag BLK_CRYPTO_CFG_ALLOW_HW.
Overall, this removes quite a bit of redundant code from ext4, f2fs,
and fs/crypto/. It should make things easier for ongoing filesystem
efforts such as iomap support, large folios, and btrfs encryption
(btrfs had already been planning to use blk-crypto exclusively.)
There are two small behavior changes of note:
- Direct I/O now works on encrypted files even without "-o inlinecrypt",
rather than falling back to buffered I/O. This is effectively a
bugfix, though I'll continue to keep an eye out for any user that
may have been depending on the buffered I/O fallback.
- IV_INO_LBLK_32 policies are no longer supported in certain cases
that didn't make sense and have no known uses.
This has been in linux-next since July 22 with no reported issues. All
encryption xfstests pass on ext4 and f2fs. As usual I've also been
using it on a system with an fscrypt-encrypted home directory. Of
course, the blk-crypto code paths also aren't new and were already
being used on many systems via the inlinecrypt mount option.
In addition to the main change described above, there are a few other
cleanups such as using lock guards for mutexes, improving
documentation, and removing a workaround for outdated gcc versions"
* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/linux: (29 commits)
blk-crypto: Update docs for blk-crypto-fallback motivation
blk-crypto: Remove unused function blk_crypto_config_supported()
fscrypt: Update docs for data path
fscrypt: Remove unused function fscrypt_finalize_bounce_page()
f2fs: Update outdated comment in f2fs_write_begin()
fs: Update outdated comment for SB_INLINECRYPT
fscrypt: Update encryption policy version docs
fscrypt: Replace some variable-size memsets with fixed-size
fscrypt: Add safety checks to non-block-based en/decryption
fscrypt: Merge bio.c and inline_crypt.c into block.c
fscrypt: Remove unused functions and workqueue
fscrypt: Remove fs-layer zeroout code
fscrypt: Remove fscrypt_dio_supported()
fscrypt: Replace calls to fscrypt_inode_uses_inline_crypto()
fs/buffer: Remove fs-layer decryption code
f2fs: Remove fs-layer file contents en/decryption code
ext4: Further de-generalize the bio postprocessing code
ext4: Make ext4_bio_write_folio() return void
ext4: Remove fs-layer file contents en/decryption code
Documentation: fscrypt: Update docs for inlinecrypt
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs writeback updates from Christian Brauner:
"This makes sync_inode_metadata() and writeback_single_inode() persist
not only the inode but all metadata associated with it.
A new .sync_inode_metadata superblock operation is called from
__writeback_single_inode(). Alongside it a new I_METADATA_WRITEBACK
state flag is added.
Filesystems no longer need their own mmb_fsync() implementations and
can just use simple_fsync(). All metadata is now written for IS_SYNC
and IS_DIRSYNC inodes. Races where several fsyncs raced and mmb_sync()
could return before all buffers were really persisted are fixed since
I_SYNC now serializes properly.
The I_METADATA_WRITEBACK scheme also fixes the case where a
WB_SYNC_NONE writeback landing between write(2) and fsync(2) left
fsync(2) failing to persist the inode. That problem is not specific to
filesystems using the generic metadata bh tracking, and the ones that
do not are left alone.
ext2, udf, bfs, minix, fat and ext4 in nojournal mode have their data
integrity writeout fixed and are converted. affs drops metadata bh
tracking and mmb_fsync() is removed.
A few other fixes came out of this:
- a UAF in mark_buffer_write_io_error()
- missed inode writeback when racing with __writeback_single_inode()
- ext4 allocating the mapping_metadata_bhs struct on demand
- three fat fixes: a lost inode update in do_msdos_rename() with
DIRSYNC, inode buffer write errors not propagating out of
fat_sync_inode_metadata() and directory entries not being
persisted on fsync(2) of the root directory"
* tag 'vfs-7.3-rc1.sync' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (24 commits)
writeback: Export __inode_attach_wb()
fat: Fix persisting directory entries on fsync(2) of the root directory
fat: Propagate inode buffer write errors from fat_sync_inode_metadata()
fat: Fix lost inode update in do_msdos_rename() with DIRSYNC
vfs: Remove mmb_fsync()
fat: Replace fat_sync_inode() with sync_inode_metadata()
fat: Fix missed inode writeback during fsync(2)
ext4: Fix data integrity writeout issues in nojournal mode
minix: Fix data integrity writeout issues
bfs: Fix data integrity writeout issues
udf: Fold udf_update_inode() into udf_write_inode()
udf: Use sync_inode_metadata() in udf_evict_inode()
udf: Drop udf_sync_inode()
udf: Use sync_inode_metadata() to writeout IS_SYNC inode
udf: Fix data integrity writeout issues
ext2: Fix data integrity writeout issues
ext2: Avoid unnecessary inode buffer writeback for sync(2)
ext2: Drop __ext2_write_inode()
ext2: Fix lost inode updates for IS_SYNC inodes
fs: Provide way for filesystem to wait for metadata writeback
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Currently, inode and in general metadata writeback is handled in a lazy
manner. When inode is dirty, __writeback_single_inode() calls
.write_inode method which for lots of filesystems just copies inode
metadata into the underlying block buffer. Writeback of other metadata
associated with the inode (as well as buffers underlying inodes) is
usually handled completely separately and implicitely during writeback
of block device inode. This is good for efficiency of WB_SYNC_NONE
writeback or sync(2). However it becomes problematic for situations
where we want to make sure inode and its metadata is really persistent
on disk. fsync(2) is the most pronounced example of this and thus we
have grown a special file operation and various helper functions to
assist with this task. However fsync(2) is not the only case, For
example directories with DIRSYNC flag need similar functionality and
current use of sync_inode_metadata() for this task in filesystems
generally misses writeout of necessary metadata.
Furthermore even fsync(2) handling as implemented by simple_fsync() or
similar helpers is racy and can fail to properly persist the inode. The
problem is that WB_SYNC_NONE writeback can copy inode metadata into
underlying buffer and clean inode dirty bits. Following fsync(2) will
see inode is clean and will fail to make sure underlying buffer is
written out.
When multiple fsync(2) calls race, there's also another type of race
involving mmb_fsync(). There the problem is buffers already submitted to
the disk are no longer tracked in the mmb list and so racing mmb_sync()
can return before all of the IO completes.
Provide a new inode state bit I_METADATA_WRITEBACK tracking whether
writeback of inode related metadata may be needed for successful data
integrity sync and if this bit is set __writeback_single_inode() for
data integrity writeback will call new superblock operation
.sync_inode_metadata whose task is to make sure all metadata associated
with the inode (including the inode itself) is properly persisted. This
will allow filesystems to address the data integrity issues described
above and at the same time somewhat simplify our fsync implementations.
Issues with racing fsync(2) calls will be addressed by synchronization on
I_SYNC inode state which is set while calling .sync_inode_metadata, issues
with missed inode buffer writeback are fixed by filesystems looking up
corresponding buffer head and writing it out if needed.
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260727104923.3828017-25-jack@suse.cz
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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Update the comment for SB_INLINECRYPT to match the latest code, where
SB_INLINECRYPT now controls whether blk-crypto uses inline encryption
hardware rather than whether blk-crypto is used.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260718214655.63186-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Switch the fs_holder_ops callbacks from recovering the single owning
superblock out of bdev->bd_holder to walking the device-to-superblock
table and acting on every superblock registered for the device. The
holder argument becomes purely the block layer's exclusivity token and
is no longer needed by the fs specific callbacks.
All devices opened with fs_holder_ops are registered by now: the main
device since setup_bdev_super() switched to fs_bdev_file_open_by_dev()
and the extra devices (xfs log and realtime devices, btrfs member
devices, the ext4 external journal) since the preceding per-filesystem
conversions. So no event is lost in the switchover.
The walk uses a refcount-pinning cursor: each step takes a reference on
the entry via sd_ref and resumes from its sd_node. Unlinking an entry
is deferred to the last unpin, so a cursor never resumes from a removed
node.
mark_dead and sync only need the passive reference the entry holds plus
s_umount, which they take with super_lock_shared(). freeze and thaw
additionally need an active reference and acquire it with
get_active_super(), which waits for the superblock to be born before
taking s_active. Taking s_active before the superblock is born would
pin a still-mounting superblock so a racing mount that aborts could
never drop s_active to zero and reach SB_DYING, deadlocking the wait
for SB_BORN. This is how filesystems_freeze() and filesystems_thaw()
acquire it too.
One semantic change: when no live superblock uses the device anymore
(the holder is dying or was never registered), fs_bdev_freeze() and
fs_bdev_thaw() now return 0 - freeze after syncing the block device -
where they used to return -EINVAL.
The freeze-deny release path moves to the table in the same switchover.
A device made unfreezable for a btrfs membership change must drop its
table entry before re-allowing freezing; otherwise a freeze racing the
release reaches the superblock through the still-registered entry and is
stranded once the release unlinks it. Split fs_bdev_unregister() out of
fs_bdev_file_release() - the inverse of fs_bdev_register() - so
btrfs_release_device_allow_freeze() can drop the {dev, sb} entry, re-allow
freezing on the still-open device, then close it. Re-allowing only after
the entry is gone keeps a racing freeze from reaching the superblock, and
doing it while the file is still open avoids touching the block device
after the close. btrfs previously yielded bd_holder before re-allowing,
which this commit makes irrelevant to freeze resolution.
Link: https://patch.msgid.link/20260616-work-super-bdev_holder_global-v2-12-7df6b864028e@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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Add fs_bdev_file_open_by_{dev,path}() and fs_bdev_file_release(). They
open the device with fs_holder_ops and register a claim in the
device-to-superblock table. Claims on the same (device, superblock)
pair share one entry, so when a filesystem claims a device it already
uses (xfs with its log on the data device), no second entry is added
and each superblock will be acted on once.
The holder argument remains purely the block layer's exclusivity token:
a superblock, or a file_system_type for a device shared by several
superblocks of that type. The shared case only becomes usable once the
fs_holder_ops callbacks resolve superblocks through the table instead
of bdev->bd_holder.
Convert the main device, setup_bdev_super() and kill_block_super(),
over: the open finds the entry registered by sget_fc() and claims it
again. cramfs and romfs bypass kill_block_super() so they can handle
MTD mounts and release the main device with a plain bdev_fput(), which
would leave the claim behind: the (dev, sb) entry would never be
unregistered and the passive reference it holds would keep the
superblock alive forever. Convert their release paths in the same
step.
The frozen-device check stays in setup_bdev_super() for the primary
device and is added to fs_bdev_register() for new claims, i.e. every
additional device a filesystem opens through the helpers. Only a
(device, superblock) pair the superblock claimed earlier may be
reopened while frozen (xfs with its log on the data device): the freeze
already covers that superblock through the existing claim, so nothing
escapes it. Without the setup_bdev_super() check a device frozen before
the mount even started (dm lock_fs, loop) could be mounted and written
to (journal replay) under an active freeze, because the primary open
reuses the entry registered by sget_fc() and never takes the new-claim
path.
Both checks read bd_fsfreeze_count only after the entry is published
(by sget_fc() for the primary, by fs_bdev_register() for new claims)
and pair with bdev_freeze() incrementing the count before walking the
table: either the mount sees the elevated freeze count and fails with
EBUSY, or the freeze finds the published entry and converges once
SB_BORN is set.
Link: https://patch.msgid.link/20260616-work-super-bdev_holder_global-v2-8-7df6b864028e@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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fs_holder_ops recovers the owning superblock from bdev->bd_holder, which
forces the holder to be exactly one superblock and prevents several
superblocks from sharing one block device. That's what erofs is doing.
As a first step introduce a global dev_t-keyed rhltable mapping each
device to the superblock(s) using it. The entry is preallocated in
alloc_super() and registered under sb->s_dev by the set callback through
set_anon_super() and set_bdev_super(), the two helpers every set
callback assigns s_dev through. Registration is the final fallible act
of a set callback, so an insert failure unwinds through sget_fc()'s
existing set-failure path: the fs_context keeps ownership of s_fs_info
and the callers' error paths stay correct. set_anon_super() releases
the anonymous dev it allocated when registration fails. Unwinding
through deactivate_locked_super() instead would run kill_sb() and free
s_fs_info behind the caller's back: nfs and ceph free that object
through a local pointer when sget_fc() fails and would double-free.
The superblock stashes the entry in sb->s_super_dev and
kill_super_notify() drops the claim through it, so teardown doesn't
depend on s_dev staying stable; an entry that was never registered is
freed together with the superblock in destroy_super_work().
Each table entry holds a passive reference (s_passive) on its
superblock, so the struct stays valid for as long as the entry is
reachable. Entries are claim-counted through sd_ref: additional claims
on the same (device, superblock) pair share the entry, and the unlink
is deferred to the last put, so a later iteration cursor never resumes
from a removed node.
The table is initialized from mnt_init(): the first superblocks (the
tmpfs shm mount and rootfs) are created from start_kernel() long before
any initcall runs, so an initcall would be too late.
The table has no readers yet; the fs_holder_ops callbacks are switched
over once all devices a filesystem claims are registered.
Link: https://patch.msgid.link/20260616-work-super-bdev_holder_global-v2-7-7df6b864028e@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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The superblock carries two counters: s_active, the active reference
count that keeps the filesystem usable, and s_count, the passive
reference count that merely keeps the structure itself alive. Turn the
passive count into a refcount_t and rename it to s_passive to make the
pairing with s_active obvious.
Everything is still serialized by sb_lock, so there is no functional
change; the conversion buys the usual refcount_t saturation and
underflow checking. The following patches start dropping passive
references without holding sb_lock and make the device-to-superblock
table hold one passive reference per registered entry, which a plain
integer cannot support.
Link: https://patch.msgid.link/20260616-work-super-bdev_holder_global-v2-2-7df6b864028e@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse
Pull fuse updates from Miklos Szeredi:
- Fix lots of bugs, most from the late 6.x era, but some going back
to 2.6.x
- Add subsystems (io-uring, passthrough) and respective maintainers
(Bernd, Joanne and Amir)
- Separate transport and fs layers (Miklos)
- Don't block on cat /dev/fuse (Joanne)
- Perform some refactoring in fuse-uring (Joanne)
- Don't use bounce-buffer for READDIR reply in virtio-fs (Matthew Ochs)
- Clean up documentation (Randy)
- Improve tracing (Amir)
- Extend page cache invalidation after DIO (Cheng Ding)
- Invalidate readdir cache on epoch change (Jun Wu)
- Misc cleanups
* tag 'fuse-update-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (81 commits)
fuse-uring: clear ent->fuse_req in commit_fetch error path
fuse-uring: use named constants for io-uring iovec indices
fuse-uring: refactor setting up copy state for payload copying
fuse-uring: use enum types for header copying
fuse-uring: refactor io-uring header copying from ring
fuse-uring: refactor io-uring header copying to ring
fuse-uring: separate next request fetching from sending logic
fuse: invalidate readdir cache on epoch bump
virtio-fs: avoid double-free on failed queue setup
fuse: invalidate page cache after DIO and async DIO writes
fuse: set ff->flock only on success
fuse: clean up interrupt reading
fuse: remove stray newline in fuse_dev_do_read()
fuse: use READ_ONCE in fuse_chan_num_background()
fuse: dax: Move long delayed work on system_dfl_long_wq
fuse: add fuse_request_sent tracepoint
fuse: Add SPDX ID lines to some files
fuse: use QSTR() instead of QSTR_INIT() in fuse_get_dentry
fuse: convert page array allocation to kcalloc()
fuse: use current creds for backing files
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This fixe does page cache invalidation after DIO and async DIO writes for
both O_DIRECT and FOPEN_DIRECT_IO cases.
Commit b359af8275a9 ("fuse: Invalidate the page cache after FOPEN_DIRECT_IO
write") fixed xfstests generic/209 for DIO writes in the FOPEN_DIRECT_IO
path. DIO writes without FOPEN_DIRECT_IO are already handled by
generic_file_direct_write().
However, async DIO writes (xfstests generic/451) remain unhandled.
After this fix:
- Async write with FUSE_ASYNC_DIO:
invalidate in fuse_aio_invalidate_worker()
- Otherwise (Sync or async write without FUSE_ASYNC_DIO):
- With FOPEN_DIRECT_IO:
invalidate in fuse_direct_write_iter()
- Without FOPEN_DIRECT_IO:
invalidate in generic_file_direct_write()
Workqueue is required for async write invalidation to prevent deadlock:
calling it directly in the I/O end routine (which is in fuse worker thread
context) can block on a folio lock held by a buffered I/O thread waiting
for the same fuse worker thread.
Co-developed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Cheng Ding <cding@ddn.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull dcache updates from Al Viro:
- d_alloc_parallel() API change (Neil's with my changes)
- NORCU fixes
- Reorganization and simplification of dentry eviction logic
- Simplifying rcu_read_lock() scopes in fs/dcache.c
- Secondary roots work - getting rid of NFS fake root dentries and
dealing with remaining shrink_dcache_for_umount() and
shrink_dentry_list() races
- making cursors NORCU (surprisingly easy)
* tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (22 commits)
make cursors NORCU
nfs: get rid of fake root dentries
wind ->s_roots via ->d_sib instead of ->d_hash
shrink_dentry_tree(): unify the calls of shrink_dentry_list()
shrinking rcu_read_lock() scope in d_alloc_parallel()
d_walk(): shrink rcu_read_lock() scope
document dentry_kill()
adjust calling conventions of lock_for_kill(), fold __dentry_kill() into dentry_kill()
Document rcu_read_lock() use in select_collect2()
Shift rcu_read_{,un}lock() inside fast_dput()
simplify safety for lock_for_kill() slowpath
fold lock_for_kill() and __dentry_kill() into common helper
fold lock_for_kill() into shrink_kill()
shrink_dentry_list(): start with removing from shrink list
d_prune_aliases(): make sure to skip NORCU aliases
kill d_dispose_if_unused()
make to_shrink_list() return whether it has moved dentry to list
select_collect(): ignore dentries on shrink lists if they have positive refcounts
find_acceptable_alias(): skip NORCU aliases with zero refcount
fix a race between d_find_any_alias() and final dput() of NORCU dentries
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull procfs updates from Christian Brauner:
- Revamp fs/filesystems.c
The file was a mess with a hand-rolled linked list in desperate need
of a cleanup. The filesystems list is now RCU-ified, /proc files can
be marked permanent from outside fs/proc/, and the string emitted
when reading /proc/filesystems is pre-generated and cached instead of
pointer-chasing and printfing entry by entry on every read.
The file is read frequently because libselinux reads it and is linked
into numerous frequently used programs (even ones you would not
suspect, like sed!). Scalability also improves since reference
maintenance on open/close is bypassed.
open+read+close cycle single-threaded (ops/s):
before: 442732
after: 1063462 (+140%)
open+read+close cycle with 20 processes (ops/s):
before: 606177
after: 3300576 (+444%)
A follow-up patch adds missing unlocks in some corner cases and
tidies things up.
- Relax the mount visibility check for subset=pid mounts
When procfs is mounted with subset=pid, all static files become
unavailable and only the dynamic pid information is accessible. In
that case there is no point in imposing the full mount visibility
restrictions on the mounter - everything that can be hidden in procfs
is already inaccessible. These restrictions prevented procfs from
being mounted inside rootless containers since almost all container
implementations overmount parts of procfs to hide certain
directories.
As part of this /proc/self/net is only shown in subset=pid mounts for
CAP_NET_ADMIN, reconfiguring subset=pid is rejected, the
SB_I_USERNS_VISIBLE superblock flag is replaced with an
FS_USERNS_MOUNT_RESTRICTED filesystem flag, fully visible mounts are
recorded in a list, and the mount restrictions are finally
documented.
- Protect ptrace_may_access() with exec_update_lock in procfs
Most uses of ptrace_may_access() in procfs should hold
exec_update_lock to avoid TOCTOU issues with concurrent privileged
execve() (like setuid binary execution).
This fixes the easy cases - the owner and visibility checks and the
FD link permission checks - with the gnarlier ones to follow later.
* tag 'vfs-7.2-rc1.procfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
fs: fix ups and tidy ups to /proc/filesystems caching
proc: protect ptrace_may_access() with exec_update_lock (FD links)
proc: protect ptrace_may_access() with exec_update_lock (part 1)
docs: proc: add documentation about mount restrictions
proc: handle subset=pid separately in userns visibility checks
proc: prevent reconfiguring subset=pid
proc: subset=pid: Show /proc/self/net only for CAP_NET_ADMIN
fs: cache the string generated by reading /proc/filesystems
sysfs: remove trivial sysfs_get_tree() wrapper
fs: RCU-ify filesystems list
fs: move SB_I_USERNS_VISIBLE to FS_USERNS_MOUNT_RESTRICTED
proc: allow to mark /proc files permanent outside of fs/proc/
namespace: record fully visible mounts in list
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shrink_dcache_for_umount() is supposed to handle the possibility of
some of the dentries to be evicted being in other threads shrink
lists; it either kills them, leaving an empty husk to be freed by
the owner of shrink list whenever it gets around to that, or it
waits for the eviction in progress to get completed.
That relies upon dentry remaining attached to the tree until the
eviction reaches dentry_unlist() and its ->d_sib gets removed
from the list. Unfortunately, the secondary roots are linked
via ->d_hash, rather than ->d_sib and they become removed from
that list before their inode references are dropped.
If shrink_dentry_list() from another thread ends up evicting
one of the secondary roots and gets to that point in dentry_kill()
when shrink_dcache_for_umount() is looking for secondary roots,
the latter will *not* notice anything, possibly leading to
warnings about busy inodes at umount time and all kinds of breakage
after that.
Moreover, shrink_dcache_for_umount() walks the list of secondary
roots with no protection whatsoever, so it might end up calling
dget() on a dentry that already passed through
lockref_mark_dead(&dentry->d_lockref);
ending up with corrupted refcount and possible UAF.
AFAICS, the most straightforward way to deal with that would be
to have secondary roots linked via ->d_sib rather than ->d_hash;
then they would remain on the list until killed, and we could
use d_add_waiter() machinery to wait for eviction in progress.
Changes:
* secondary roots look the same as ->s_root from d_unhashed()
and d_unlinked() POV now.
* secondary roots are represented as "no parent, but on ->d_sib"
instead of "no parent, but on ->d_hash".
* since ->d_sib is a plain hlist, we protect it with per-superblock
spinlock (sb->s_roots_lock) instead of the LSB of the head pointer (for
non-root dentries it would be protected by ->d_lock of parent).
* __d_obtain_alias() uses ->d_sib for linkage when allocating
a secondary root.
* d_splice_alias_ops() detects splicing of a secondary root and
removes it from the list before calling __d_move().
* dentry_unlist() detects eviction of a secondary root and
removes it from the list; no need to play the games for d_walk() sake,
since the latter is not going to look for the next sibling of those
anyway.
* ___d_drop() doesn't care about ->s_roots anymore.
* shrink_dcache_for_umount() uses proper locking for access to
the list of secondary roots and if it runs into one that is in the middle
of eviction waits for that to finish.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Tracking in-flight inode wb switches with a single global counter
(isw_nr_in_flight) plus a synchronize_rcu() based wait in
cgroup_writeback_umount() forces every umount to take a global hit
whenever any other superblock on the system has wb switches in flight,
even if the superblock being unmounted has none of its own.
Replace the global synchronize_rcu()/flush_workqueue() pair with a
per-sb counter, s_isw_nr_in_flight, plus three small helpers:
- cgroup_writeback_pin(sb) - increment counter
- cgroup_writeback_unpin(sb) - decrement and wake drainer if last
- cgroup_writeback_drain(sb) - wait for counter to reach zero
The wiring is:
- inode_prepare_wbs_switch() pins before checking SB_ACTIVE and
grabbing the inode; failure paths unpin before returning. A
lockless SB_ACTIVE check at the top of the function lets us skip
the atomic_inc/smp_mb dance once SB_ACTIVE has been cleared (it
is monotonic and never set back).
- process_inode_switch_wbs() unpins after the matching iput().
- cgroup_writeback_umount() drains the per-sb counter via
wait_var_event().
The smp_mb() pair between inode_prepare_wbs_switch() and
cgroup_writeback_umount() keeps the SB_ACTIVE / counter ordering:
either the umounter sees a non-zero counter and waits, or the
switcher sees SB_ACTIVE cleared and aborts before grabbing the
inode.
The global isw_nr_in_flight is left in place, since it is still used
to throttle in-flight switches via WB_FRN_MAX_IN_FLIGHT.
The rcu_read_lock() extension in inode_switch_wbs() and
cleanup_offline_cgwb() that the race fix added is no longer needed
and is reverted; the synchronize_rcu() that the race fix added to
cgroup_writeback_umount() is dropped as well.
The following numbers were measured on a 16 vCPU QEMU guest with 4
background superblocks each churning "create memcg -> write 1 MiB ->
rmdir memcg" to keep the global isw_nr_in_flight non-zero. Latencies
are wall-clock around umount(8); only the target sb's umount is
measured.
Target sb runs its own cgwb churn:
p50 p95 p99 max
global synchronize_rcu() 67.6 ms 88.3 ms 88.3 ms 96.8 ms
per-sb counter (this) 7.9 ms 10.0 ms 10.0 ms 10.1 ms
Idle target umount latency under cross-sb cgwb-switch pressure:
p50 p95 p99 max
global synchronize_rcu() 62.7 ms 95.4 ms 108.1 ms 108.6 ms
per-sb counter (this) 5.3 ms 6.9 ms 7.4 ms 7.4 ms
no-pressure baseline 4.9 ms 5.9 ms 6.3 ms 6.7 ms
8 concurrent umounts of idle sbs under the same pressure:
p50 p95 max
global synchronize_rcu() 61.3 ms 99.5 ms 113.7 ms
per-sb counter (this) 8.1 ms 9.1 ms 9.5 ms
In-kernel cgroup_writeback_umount() time across the same run
(bpftrace, ~340 calls covering all scenarios):
global synchronize_rcu() 12371 ms total (~36 ms / call)
per-sb counter (this) 1.37 ms total ( ~4 us / call)
Suggested-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/r/177910456953.488929.2169908940676707307.b4-review@b4
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Baokun Li <libaokun@linux.alibaba.com>
Link: https://patch.msgid.link/20260521095016.2791354-4-libaokun@linux.alibaba.com
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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When procfs is mounted with subset=pid, only the dynamic process-related
part of the filesystem remains visible. That part cannot be hidden by
overmounts, so checking whether an existing procfs mount is fully
visible does not make sense for this mode.
At the same time, a subset=pid procfs mount must not be used as evidence
that a later procfs mount would not reveal additional information. It
provides a restricted view of procfs, not the full filesystem view.
Mark subset=pid procfs instances as restricted variants. Ignore
restricted variants when looking for an already-visible mount, and allow
new restricted variants without consulting mnt_already_visible().
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://patch.msgid.link/4d5e760c3d534dd2e05578d119cc408450053a98.1777278334.git.legion@kernel.org
Reviewed-by: Aleksa Sarai <aleksa@amutable.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Whether a filesystem's mounts need to undergo a visibility check in user
namespaces is a static property of the filesystem type, not a runtime
property of each superblock instance. Both proc and sysfs always set
SB_I_USERNS_VISIBLE on their superblocks unconditionally (sysfs does so
on first creation, and subsequent mounts reuse the same superblock).
Move this flag from sb->s_iflags (SB_I_USERNS_VISIBLE) to
file_system_type->fs_flags (FS_USERNS_MOUNT_RESTRICTED) so the intent
is expressed at the filesystem type level where it belongs.
All check sites are updated to test sb->s_type->fs_flags instead of
sb->s_iflags. The SB_I_NOEXEC and SB_I_NODEV flags remain on the
superblock as they are runtime properties set during fill_super.
Link: https://patch.msgid.link/72887c5b6204dc3adf5a53104f0be6bd8bc4f6cd.1777278334.git.legion@kernel.org
Reviewed-by: Aleksa Sarai <aleksa@amutable.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Add a SB_I_NO_DATA_INTEGRITY superblock flag for filesystems that cannot
guarantee data persistence on sync (eg fuse). For superblocks with this
flag set, sync kicks off writeback of dirty inodes but does not wait
for the flusher threads to complete the writeback.
This replaces the per-inode AS_NO_DATA_INTEGRITY mapping flag added in
commit f9a49aa302a0 ("fs/writeback: skip AS_NO_DATA_INTEGRITY mappings
in wait_sb_inodes()"). The flag belongs at the superblock level because
data integrity is a filesystem-wide property, not a per-inode one.
Having this flag at the superblock level also allows us to skip having
to iterate every dirty inode in wait_sb_inodes() only to skip each inode
individually.
Prior to this commit, mappings with no data integrity guarantees skipped
waiting on writeback completion but still waited on the flusher threads
to finish initiating the writeback. Waiting on the flusher threads is
unnecessary. This commit kicks off writeback but does not wait on the
flusher threads. This change properly addresses a recent report [1] for
a suspend-to-RAM hang seen on fuse-overlayfs that was caused by waiting
on the flusher threads to finish:
Workqueue: pm_fs_sync pm_fs_sync_work_fn
Call Trace:
<TASK>
__schedule+0x457/0x1720
schedule+0x27/0xd0
wb_wait_for_completion+0x97/0xe0
sync_inodes_sb+0xf8/0x2e0
__iterate_supers+0xdc/0x160
ksys_sync+0x43/0xb0
pm_fs_sync_work_fn+0x17/0xa0
process_one_work+0x193/0x350
worker_thread+0x1a1/0x310
kthread+0xfc/0x240
ret_from_fork+0x243/0x280
ret_from_fork_asm+0x1a/0x30
</TASK>
On fuse this is problematic because there are paths that may cause the
flusher thread to block (eg if systemd freezes the user session cgroups
first, which freezes the fuse daemon, before invoking the kernel
suspend. The kernel suspend triggers ->write_node() which on fuse issues
a synchronous setattr request, which cannot be processed since the
daemon is frozen. Or if the daemon is buggy and cannot properly complete
writeback, initiating writeback on a dirty folio already under writeback
leads to writeback_get_folio() -> folio_prepare_writeback() ->
unconditional wait on writeback to finish, which will cause a hang).
This commit restores fuse to its prior behavior before tmp folios were
removed, where sync was essentially a no-op.
[1] https://lore.kernel.org/linux-fsdevel/CAJnrk1a-asuvfrbKXbEwwDSctvemF+6zfhdnuzO65Pt8HsFSRw@mail.gmail.com/T/#m632c4648e9cafc4239299887109ebd880ac6c5c1
Fixes: 0c58a97f919c ("fuse: remove tmp folio for writebacks and internal rb tree")
Reported-by: John <therealgraysky@proton.me>
Cc: stable@vger.kernel.org
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://patch.msgid.link/20260320005145.2483161-2-joannelkoong@gmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs mount updates from Christian Brauner:
- statmount: accept fd as a parameter
Extend struct mnt_id_req with a file descriptor field and a new
STATMOUNT_BY_FD flag. When set, statmount() returns mount information
for the mount the fd resides on — including detached mounts
(unmounted via umount2(MNT_DETACH)).
For detached mounts the STATMOUNT_MNT_POINT and STATMOUNT_MNT_NS_ID
mask bits are cleared since neither is meaningful. The capability
check is skipped for STATMOUNT_BY_FD since holding an fd already
implies prior access to the mount and equivalent information is
available through fstatfs() and /proc/pid/mountinfo without
privilege. Includes comprehensive selftests covering both attached
and detached mount cases.
- fs: Remove internal old mount API code (1 patch)
Now that every in-tree filesystem has been converted to the new
mount API, remove all the legacy shim code in fs_context.c that
handled unconverted filesystems. This deletes ~280 lines including
legacy_init_fs_context(), the legacy_fs_context struct, and
associated wrappers. The mount(2) syscall path for userspace remains
untouched. Documentation references to the legacy callbacks are
cleaned up.
- mount: add OPEN_TREE_NAMESPACE to open_tree()
Container runtimes currently use CLONE_NEWNS to copy the caller's
entire mount namespace — only to then pivot_root() and recursively
unmount everything they just copied. With large mount tables and
thousands of parallel container launches this creates significant
contention on the namespace semaphore.
OPEN_TREE_NAMESPACE copies only the specified mount tree (like
OPEN_TREE_CLONE) but returns a mount namespace fd instead of a
detached mount fd. The new namespace contains the copied tree mounted
on top of a clone of the real rootfs.
This functions as a combined unshare(CLONE_NEWNS) + pivot_root() in a
single syscall. Works with user namespaces: an unshare(CLONE_NEWUSER)
followed by OPEN_TREE_NAMESPACE creates a mount namespace owned by
the new user namespace. Mount namespace file mounts are excluded from
the copy to prevent cycles. Includes ~1000 lines of selftests"
* tag 'vfs-7.0-rc1.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
selftests/open_tree: add OPEN_TREE_NAMESPACE tests
mount: add OPEN_TREE_NAMESPACE
fs: Remove internal old mount API code
selftests: statmount: tests for STATMOUNT_BY_FD
statmount: accept fd as a parameter
statmount: permission check should return EPERM
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Create some wrapper code around struct super_block so that filesystems
have a standard way to queue filesystem metadata and file I/O error
reports to have them sent to fsnotify.
If a filesystem wants to provide an error number, it must supply only
negative error numbers. These are stored internally as negative
numbers, but they are converted to positive error numbers before being
passed to fanotify, per the fanotify(7) manpage. Implementations of
super_operations::report_error are passed the raw internal event data.
Note that we have to play some shenanigans with mempools and queue_work
so that the error handling doesn't happen outside of process context,
and the event handler functions (both ->report_error and fsnotify) can
handle file I/O error messages without having to worry about whatever
locks might be held. This asynchronicity requires that unmount wait for
pending events to clear.
Add a new callback to the superblock operations structure so that
filesystem drivers can themselves respond to file I/O errors if they so
desire. This will be used for an upcoming self-healing patchset for
XFS.
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://patch.msgid.link/176826402610.3490369.4378391061533403171.stgit@frogsfrogsfrogs
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Now that the last in-tree filesystem has been converted to the new mount
API, remove all legacy mount API code designed to handle un-converted
filesystems, and remove associated documentation as well.
(The code to handle the legacy mount(2) syscall from userspace is still
in place, of course.)
Tested with an allmodconfig build on x86_64, and a sanity check of an
old mount(2) syscall mount.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Link: https://patch.msgid.link/20251212174403.2882183-1-sandeen@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull superblock lock guard updates from Christian Brauner:
"This starts the work of introducing guards for superblock related
locks.
Introduce super_write_guard for scoped superblock write protection.
This provides a guard-based alternative to the manual sb_start_write()
and sb_end_write() pattern, allowing the compiler to automatically
handle the cleanup"
* tag 'vfs-6.19-rc1.guards' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
xfs: use super write guard in xfs_file_ioctl()
open: use super write guard in do_ftruncate()
btrfs: use super write guard in relocating_repair_kthread()
ext4: use super write guard in write_mmp_block()
btrfs: use super write guard in sb_start_write()
btrfs: use super write guard btrfs_run_defrag_inode()
btrfs: use super write guard in btrfs_reclaim_bgs_work()
fs: add super_write_guard
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull fs header updates from Christian Brauner:
"This contains initial work to start splitting up fs.h.
Begin the long-overdue work of splitting up the monolithic fs.h
header. The header has grown to over 3000 lines and includes types and
functions for many different subsystems, making it difficult to
navigate and causing excessive compilation dependencies.
This series introduces new focused headers for superblock-related
code:
- Rename fs_types.h to fs_dirent.h to better reflect its actual
content (directory entry types)
- Add fs/super_types.h containing superblock type definitions
- Add fs/super.h containing superblock function declarations
This is the first step in a longer effort to modularize the VFS
headers.
Cleanups:
- Inode Field Layout Optimization (Mateusz Guzik)
Move inode fields used during fast path lookup closer together to
improve cache locality during path resolution.
- current_umask() Optimization (Mateusz Guzik)
Inline current_umask() and move it to fs_struct.h. This improves
performance by avoiding function call overhead for this
frequently-used function, and places it in a more appropriate
header since it operates on fs_struct"
* tag 'vfs-6.19-rc1.fs_header' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
fs: move inode fields used during fast path lookup closer together
fs: inline current_umask() and move it to fs_struct.h
fs: add fs/super.h header
fs: add fs/super_types.h header
fs: rename fs_types.h to fs_dirent.h
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Link: https://patch.msgid.link/20251104-work-guards-v1-1-5108ac78a171@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Split out super block associated functions into a separate header.
Link: https://patch.msgid.link/20251104-work-fs-header-v1-3-fb39a2efe39e@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Split out super block associated structures into a separate header.
Link: https://patch.msgid.link/20251104-work-fs-header-v1-2-fb39a2efe39e@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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