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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs async directory updates from Christian Brauner:
"This contains further preparatory changes for the asynchronous directory
locking scheme:
- Add lookup_one_positive_killable() which allows overlayfs to
perform lookup that won't block on a fatal signal
- Unify the mount idmap handling in struct renamedata as a rename can
only happen within a single mount
- Introduce kern_path_parent() for audit which sets the path to the
parent and returns a dentry for the target without holding any
locks on return
- Rename kern_path_locked() as it is only used to prepare for the
removal of an object from the filesystem:
kern_path_locked() => start_removing_path()
kern_path_create() => start_creating_path()
user_path_create() => start_creating_user_path()
user_path_locked_at() => start_removing_user_path_at()
done_path_create() => end_creating_path()
NA => end_removing_path()"
* tag 'vfs-6.18-rc1.async' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
debugfs: rename start_creating() to debugfs_start_creating()
VFS: rename kern_path_locked() and related functions.
VFS/audit: introduce kern_path_parent() for audit
VFS: unify old_mnt_idmap and new_mnt_idmap in renamedata
VFS: discard err2 in filename_create()
VFS/ovl: add lookup_one_positive_killable()
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kern_path_locked() is now only used to prepare for removing an object
from the filesystem (and that is the only credible reason for wanting a
positive locked dentry). Thus it corresponds to kern_path_create() and
so should have a corresponding name.
Unfortunately the name "kern_path_create" is somewhat misleading as it
doesn't actually create anything. The recently added
simple_start_creating() provides a better pattern I believe. The
"start" can be matched with "end" to bracket the creating or removing.
So this patch changes names:
kern_path_locked -> start_removing_path
kern_path_create -> start_creating_path
user_path_create -> start_creating_user_path
user_path_locked_at -> start_removing_user_path_at
done_path_create -> end_creating_path
and also introduces end_removing_path() which is identical to
end_creating_path().
__start_removing_path (which was __kern_path_locked) is enhanced to
call mnt_want_write() for consistency with the start_creating_path().
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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audit_alloc_mark() and audit_get_nd() both need to perform a path
lookup getting the parent dentry (which must exist) and the final
target (following a LAST_NORM name) which sometimes doesn't need to
exist.
They don't need the parent to be locked, but use kern_path_locked() or
kern_path_locked_negative() anyway. This is somewhat misleading to the
casual reader.
This patch introduces a more targeted function, kern_path_parent(),
which returns not holding locks. On success the "path" will
be set to the parent, which must be found, and the return value is the
dentry of the target, which might be negative.
This will clear the way to rename kern_path_locked() which is
otherwise only used to prepare for removing something.
It also allows us to remove kern_path_locked_negative(), which is
transformed into the new kern_path_parent().
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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A rename operation can only rename within a single mount. Callers of
vfs_rename() must and do ensure this is the case.
So there is no point in having two mnt_idmaps in renamedata as they are
always the same. Only one of them is passed to ->rename in any case.
This patch replaces both with a single "mnt_idmap" and changes all
callers.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Since 204a575e91f3 "VFS: add common error checks to lookup_one_qstr_excl()"
filename_create() does not need to stash the error value from mnt_want_write()
into a separate variable - the logic that used to clobber 'error' after the
call of mnt_want_write() has migrated into lookup_one_qstr_excl().
So there is no need for two different err variables.
This patch discards "err2" and uses "error' throughout.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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ovl wants a lookup which won't block on a fatal signal. It currently
uses down_write_killable() and then repeatedly calls to lookup_one()
The lock may not be needed if the name is already in the dcache and it
aids proposed future changes if the locking is kept internal to namei.c
So this patch adds lookup_one_positive_killable() which is like
lookup_one_positive() but will abort in the face of a fatal signal.
overlayfs is changed to use this.
Note that instead of always getting an exclusive lock, ovl now only gets
a shared lock, and only sometimes. The exclusive lock was never needed.
However down_read_killable() was only added in v4.15 but overlayfs started
using down_write_killable() here in v4.7.
Note that the linked list ->first_maybe_whiteout ->next_maybe_white is
local to the thread so there is no concurrency in that list which could
be threatened by removing the locking.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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openat2 had a bug: if we pass RESOLVE_NO_XDEV, then openat2
doesn't traverse through automounts, but may still trigger them.
(See the link for full bug report with reproducer.)
This commit fixes this bug.
Link: https://lore.kernel.org/linux-fsdevel/20250817075252.4137628-1-safinaskar@zohomail.com/
Fixes: fddb5d430ad9fa91b49b1 ("open: introduce openat2(2) syscall")
Reviewed-by: Aleksa Sarai <cyphar@cyphar.com>
Cc: stable@vger.kernel.org
Signed-off-by: Askar Safin <safinaskar@zohomail.com>
Link: https://lore.kernel.org/20250825181233.2464822-5-safinaskar@zohomail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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This is preparation to RESOLVE_NO_XDEV fix in following commits.
Also this commit makes LOOKUP_NO_XDEV logic more clear: now we
immediately fail with EXDEV on first mount crossing
instead of waiting for very end.
No functional change intended
Signed-off-by: Askar Safin <safinaskar@zohomail.com>
Link: https://lore.kernel.org/20250825181233.2464822-4-safinaskar@zohomail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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This is preparation to RESOLVE_NO_XDEV fix in following commits.
No functional change intended.
The only place that ever looks at
ND_JUMPED in nd->state is complete_walk()
and we are not going to reach
it if handle_mounts() returns an error
Signed-off-by: Askar Safin <safinaskar@zohomail.com>
Link: https://lore.kernel.org/20250825181233.2464822-3-safinaskar@zohomail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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This is preparation to RESOLVE_NO_XDEV fix in following commits.
No functional change intended
Signed-off-by: Askar Safin <safinaskar@zohomail.com>
Link: https://lore.kernel.org/20250825181233.2464822-2-safinaskar@zohomail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Trivial fix to spelling mistake in comment text.
Signed-off-by: Xichao Zhao <zhao.xichao@vivo.com>
Link: https://lore.kernel.org/20250808083758.229563-1-zhao.xichao@vivo.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 pidfs updates from Christian Brauner:
- persistent info
Persist exit and coredump information independent of whether anyone
currently holds a pidfd for the struct pid.
The current scheme allocated pidfs dentries on-demand repeatedly.
This scheme is reaching it's limits as it makes it impossible to pin
information that needs to be available after the task has exited or
coredumped and that should not be lost simply because the pidfd got
closed temporarily. The next opener should still see the stashed
information.
This is also a prerequisite for supporting extended attributes on
pidfds to allow attaching meta information to them.
If someone opens a pidfd for a struct pid a pidfs dentry is allocated
and stashed in pid->stashed. Once the last pidfd for the struct pid
is closed the pidfs dentry is released and removed from pid->stashed.
So if 10 callers create a pidfs dentry for the same struct pid
sequentially, i.e., each closing the pidfd before the other creates a
new one then a new pidfs dentry is allocated every time.
Because multiple tasks acquiring and releasing a pidfd for the same
struct pid can race with each another a task may still find a valid
pidfs entry from the previous task in pid->stashed and reuse it. Or
it might find a dead dentry in there and fail to reuse it and so
stashes a new pidfs dentry. Multiple tasks may race to stash a new
pidfs dentry but only one will succeed, the other ones will put their
dentry.
The current scheme aims to ensure that a pidfs dentry for a struct
pid can only be created if the task is still alive or if a pidfs
dentry already existed before the task was reaped and so exit
information has been was stashed in the pidfs inode.
That's great except that it's buggy. If a pidfs dentry is stashed in
pid->stashed after pidfs_exit() but before __unhash_process() is
called we will return a pidfd for a reaped task without exit
information being available.
The pidfds_pid_valid() check does not guard against this race as it
doens't sync at all with pidfs_exit(). The pid_has_task() check might
be successful simply because we're before __unhash_process() but
after pidfs_exit().
Introduce a new scheme where the lifetime of information associated
with a pidfs entry (coredump and exit information) isn't bound to the
lifetime of the pidfs inode but the struct pid itself.
The first time a pidfs dentry is allocated for a struct pid a struct
pidfs_attr will be allocated which will be used to store exit and
coredump information.
If all pidfs for the pidfs dentry are closed the dentry and inode can
be cleaned up but the struct pidfs_attr will stick until the struct
pid itself is freed. This will ensure minimal memory usage while
persisting relevant information.
The new scheme has various advantages. First, it allows to close the
race where we end up handing out a pidfd for a reaped task for which
no exit information is available. Second, it minimizes memory usage.
Third, it allows to remove complex lifetime tracking via dentries
when registering a struct pid with pidfs. There's no need to get or
put a reference. Instead, the lifetime of exit and coredump
information associated with a struct pid is bound to the lifetime of
struct pid itself.
- extended attributes
Now that we have a way to persist information for pidfs dentries we
can start supporting extended attributes on pidfds. This will allow
userspace to attach meta information to tasks.
One natural extension would be to introduce a custom pidfs.* extended
attribute space and allow for the inheritance of extended attributes
across fork() and exec().
The first simple scheme will allow privileged userspace to set
trusted extended attributes on pidfs inodes.
- Allow autonomous pidfs file handles
Various filesystems such as pidfs and drm support opening file
handles without having to require a file descriptor to identify the
filesystem. The filesystem are global single instances and can be
trivially identified solely on the information encoded in the file
handle.
This makes it possible to not have to keep or acquire a sentinal file
descriptor just to pass it to open_by_handle_at() to identify the
filesystem. That's especially useful when such sentinel file
descriptor cannot or should not be acquired.
For pidfs this means a file handle can function as full replacement
for storing a pid in a file. Instead a file handle can be stored and
reopened purely based on the file handle.
Such autonomous file handles can be opened with or without specifying
a a file descriptor. If no proper file descriptor is used the
FD_PIDFS_ROOT sentinel must be passed. This allows us to define
further special negative fd sentinels in the future.
Userspace can trivially test for support by trying to open the file
handle with an invalid file descriptor.
- Allow pidfds for reaped tasks with SCM_PIDFD messages
This is a logical continuation of the earlier work to create pidfds
for reaped tasks through the SO_PEERPIDFD socket option merged in
923ea4d4482b ("Merge patch series "net, pidfs: enable handing out
pidfds for reaped sk->sk_peer_pid"").
- Two minor fixes:
* Fold fs_struct->{lock,seq} into a seqlock
* Don't bother with path_{get,put}() in unix_open_file()
* tag 'vfs-6.17-rc1.pidfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (37 commits)
don't bother with path_get()/path_put() in unix_open_file()
fold fs_struct->{lock,seq} into a seqlock
selftests: net: extend SCM_PIDFD test to cover stale pidfds
af_unix: enable handing out pidfds for reaped tasks in SCM_PIDFD
af_unix: stash pidfs dentry when needed
af_unix/scm: fix whitespace errors
af_unix: introduce and use scm_replace_pid() helper
af_unix: introduce unix_skb_to_scm helper
af_unix: rework unix_maybe_add_creds() to allow sleep
selftests/pidfd: decode pidfd file handles withou having to specify an fd
fhandle, pidfs: support open_by_handle_at() purely based on file handle
uapi/fcntl: add FD_PIDFS_ROOT
uapi/fcntl: add FD_INVALID
fcntl/pidfd: redefine PIDFD_SELF_THREAD_GROUP
uapi/fcntl: mark range as reserved
fhandle: reflow get_path_anchor()
pidfs: add pidfs_root_path() helper
fhandle: rename to get_path_anchor()
fhandle: hoist copy_from_user() above get_path_from_fd()
fhandle: raise FILEID_IS_DIR in handle_type
...
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull async directory updates from Christian Brauner:
"This contains preparatory changes for the asynchronous directory
locking scheme.
While the locking scheme is still very much controversial and we're
still far away from landing any actual changes in that area the
preparatory work that we've been upstreaming for a while now has been
very useful. This is another set of minor changes and cleanups"
* tag 'vfs-6.17-rc1.async.dir' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
exportfs: use lookup_one_unlocked()
coda: use iterate_dir() in coda_readdir()
VFS: Minor fixes for porting.rst
VFS: merge lookup_one_qstr_excl_raw() back into lookup_one_qstr_excl()
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull misc VFS updates from Christian Brauner:
"This contains the usual selections of misc updates for this cycle.
Features:
- Add ext4 IOCB_DONTCACHE support
This refactors the address_space_operations write_begin() and
write_end() callbacks to take const struct kiocb * as their first
argument, allowing IOCB flags such as IOCB_DONTCACHE to propagate
to the filesystem's buffered I/O path.
Ext4 is updated to implement handling of the IOCB_DONTCACHE flag
and advertises support via the FOP_DONTCACHE file operation flag.
Additionally, the i915 driver's shmem write paths are updated to
bypass the legacy write_begin/write_end interface in favor of
directly calling write_iter() with a constructed synchronous kiocb.
Another i915 change replaces a manual write loop with
kernel_write() during GEM shmem object creation.
Cleanups:
- don't duplicate vfs_open() in kernel_file_open()
- proc_fd_getattr(): don't bother with S_ISDIR() check
- fs/ecryptfs: replace snprintf with sysfs_emit in show function
- vfs: Remove unnecessary list_for_each_entry_safe() from
evict_inodes()
- filelock: add new locks_wake_up_waiter() helper
- fs: Remove three arguments from block_write_end()
- VFS: change old_dir and new_dir in struct renamedata to dentrys
- netfs: Remove unused declaration netfs_queue_write_request()
Fixes:
- eventpoll: Fix semi-unbounded recursion
- eventpoll: fix sphinx documentation build warning
- fs/read_write: Fix spelling typo
- fs: annotate data race between poll_schedule_timeout() and
pollwake()
- fs/pipe: set FMODE_NOWAIT in create_pipe_files()
- docs/vfs: update references to i_mutex to i_rwsem
- fs/buffer: remove comment about hard sectorsize
- fs/buffer: remove the min and max limit checks in __getblk_slow()
- fs/libfs: don't assume blocksize <= PAGE_SIZE in
generic_check_addressable
- fs_context: fix parameter name in infofc() macro
- fs: Prevent file descriptor table allocations exceeding INT_MAX"
* tag 'vfs-6.17-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (24 commits)
netfs: Remove unused declaration netfs_queue_write_request()
eventpoll: fix sphinx documentation build warning
ext4: support uncached buffered I/O
mm/pagemap: add write_begin_get_folio() helper function
fs: change write_begin/write_end interface to take struct kiocb *
drm/i915: Refactor shmem_pwrite() to use kiocb and write_iter
drm/i915: Use kernel_write() in shmem object create
eventpoll: Fix semi-unbounded recursion
vfs: Remove unnecessary list_for_each_entry_safe() from evict_inodes()
fs/libfs: don't assume blocksize <= PAGE_SIZE in generic_check_addressable
fs/buffer: remove the min and max limit checks in __getblk_slow()
fs: Prevent file descriptor table allocations exceeding INT_MAX
fs: Remove three arguments from block_write_end()
fs/ecryptfs: replace snprintf with sysfs_emit in show function
fs: annotate suspected data race between poll_schedule_timeout() and pollwake()
docs/vfs: update references to i_mutex to i_rwsem
fs/buffer: remove comment about hard sectorsize
fs_context: fix parameter name in infofc() macro
VFS: change old_dir and new_dir in struct renamedata to dentrys
proc_fd_getattr(): don't bother with S_ISDIR() check
...
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The combination of spinlock_t lock and seqcount_spinlock_t seq
in struct fs_struct is an open-coded seqlock_t (see linux/seqlock_types.h).
Combine and switch to equivalent seqlock_t primitives. AFAICS,
that does end up with the same sequence of underlying operations in all
cases.
While we are at it, get_fs_pwd() is open-coded verbatim in
get_path_from_fd(); rather than applying conversion to it, replace with
the call of get_fs_pwd() there. Not worth splitting the commit for that,
IMO...
A bit of historical background - conversion of seqlock_t to
use of seqcount_spinlock_t happened several months after the same
had been done to struct fs_struct; switching fs_struct to seqlock_t
could've been done immediately after that, but it looks like nobody
had gotten around to that until now.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/20250702053437.GC1880847@ZenIV
Acked-by: Ahmed S. Darwish <darwi@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Christian Brauner <brauner@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 fixes from Christian Brauner:
- Fix a regression caused by the anonymous inode rework. Making them
regular files causes various places in the kernel to tip over
starting with io_uring.
Revert to the former status quo and port our assertion to be based on
checking the inode so we don't lose the valuable VFS_*_ON_*()
assertions that have already helped discover weird behavior our
outright bugs.
- Fix the the upper bound calculation in fuse_fill_write_pages()
- Fix priority inversion issues in the eventpoll code
- Make secretmen use anon_inode_make_secure_inode() to avoid bypassing
the LSM layer
- Fix a netfs hang due to missing case in final DIO read result
collection
- Fix a double put of the netfs_io_request struct
- Provide some helpers to abstract out NETFS_RREQ_IN_PROGRESS flag
wrangling
- Fix infinite looping in netfs_wait_for_pause/request()
- Fix a netfs ref leak on an extra subrequest inserted into a request's
list of subreqs
- Fix various cifs RPC callbacks to set NETFS_SREQ_NEED_RETRY if a
subrequest fails retriably
- Fix a cifs warning in the workqueue code when reconnecting a channel
- Fix the updating of i_size in netfs to avoid a race between testing
if we should have extended the file with a DIO write and changing
i_size
- Merge the places in netfs that update i_size on write
- Fix coredump socket selftests
* tag 'vfs-6.16-rc5.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
anon_inode: rework assertions
netfs: Update tracepoints in a number of ways
netfs: Renumber the NETFS_RREQ_* flags to make traces easier to read
netfs: Merge i_size update functions
netfs: Fix i_size updating
smb: client: set missing retry flag in cifs_writev_callback()
smb: client: set missing retry flag in cifs_readv_callback()
smb: client: set missing retry flag in smb2_writev_callback()
netfs: Fix ref leak on inserted extra subreq in write retry
netfs: Fix looping in wait functions
netfs: Provide helpers to perform NETFS_RREQ_IN_PROGRESS flag wangling
netfs: Fix double put of request
netfs: Fix hang due to missing case in final DIO read result collection
eventpoll: Fix priority inversion problem
fuse: fix fuse_fill_write_pages() upper bound calculation
fs: export anon_inode_make_secure_inode() and fix secretmem LSM bypass
selftests/coredump: Fix "socket_detect_userspace_client" test failure
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Making anonymous inodes regular files comes with a lot of risk and
regression potential as evidenced by a recent hickup in io_uring. We're
better of continuing to not have them be regular files. Since we have
S_ANON_INODE we can port all of our assertions easily.
Link: https://lore.kernel.org/20250702-work-fixes-v1-1-ff76ea589e33@kernel.org
Fixes: cfd86ef7e8e7 ("anon_inode: use a proper mode internally")
Acked-by: Jens Axboe <axboe@kernel.dk>
Cc: stable@kernel.org
Reported-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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VFS has switched to i_rwsem for ten years now (9902af79c01a: parallel
lookups actual switch to rwsem), but the VFS documentation and comments
still has references to i_mutex.
Signed-off-by: Junxuan Liao <ljx@cs.wisc.edu>
Link: https://lore.kernel.org/72223729-5471-474a-af3c-f366691fba82@cs.wisc.edu
Signed-off-by: Christian Brauner <brauner@kernel.org>
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all users of 'struct renamedata' have the dentry for the old and new
directories, and often have no use for the inode except to store it in
the renamedata.
This patch changes struct renamedata to hold the dentry, rather than
the inode, for the old and new directories, and changes callers to
match. The names are also changed from a _dir suffix to _parent. This
is consistent with other usage in namei.c and elsewhere.
This results in the removal of several local variables and several
dereferences of ->d_inode at the cost of adding ->d_inode dereferences
to vfs_rename().
Acked-by: Miklos Szeredi <miklos@szeredi.hu>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/174977089072.608730.4244531834577097454@noble.neil.brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The effect of lookup_one_qstr_excl_raw() can be achieved by passing
LOOKUP_CREATE() to lookup_one_qstr_excl() - we don't need a separate
function.
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/20250608230952.20539-2-neil@brown.name
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The recent change from using d_hash_and_lookup() to using
try_lookup_noperm() inadvertently introduce a d_revalidate() call when
the lookup was successful. Steven French reports that this resulted in
worse than halving of performance in some cases.
Prior to the offending patch the only caller of try_lookup_noperm() was
autofs which does not need the d_revalidate(). So it is safe to remove
the d_revalidate() call providing we stop using try_lookup_noperm() to
implement lookup_noperm().
The "try_" in the name is strongly suggestive that the caller isn't
expecting much effort, so it seems reasonable to avoid the effort of
d_revalidate().
Fixes: 06c567403ae5 ("Use try_lookup_noperm() instead of d_hash_and_lookup() outside of VFS")
Reported-by: Steve French <smfrench@gmail.com>
Link: https://lore.kernel.org/all/CAH2r5mu5SfBrdc2CFHwzft8=n9koPMk+Jzwpy-oUMx-wCRCesQ@mail.gmail.com/
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/174951744454.608730.18354002683881684261@noble.neil.brown.name
Tested-by: Steve French <stfrench@microsoft.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 misc vfs updates from Christian Brauner:
"This contains the usual selections of misc updates for this cycle.
Features:
- Use folios for symlinks in the page cache
FUSE already uses folios for its symlinks. Mirror that conversion
in the generic code and the NFS code. That lets us get rid of a few
folio->page->folio conversions in this path, and some of the few
remaining users of read_cache_page() / read_mapping_page()
- Try and make a few filesystem operations killable on the VFS
inode->i_mutex level
- Add sysctl vfs_cache_pressure_denom for bulk file operations
Some workloads need to preserve more dentries than we currently
allow through out sysctl interface
A HDFS servers with 12 HDDs per server, on a HDFS datanode startup
involves scanning all files and caching their metadata (including
dentries and inodes) in memory. Each HDD contains approximately 2
million files, resulting in a total of ~20 million cached dentries
after initialization
To minimize dentry reclamation, they set vfs_cache_pressure to 1.
Despite this configuration, memory pressure conditions can still
trigger reclamation of up to 50% of cached dentries, reducing the
cache from 20 million to approximately 10 million entries. During
the subsequent cache rebuild period, any HDFS datanode restart
operation incurs substantial latency penalties until full cache
recovery completes
To maintain service stability, more dentries need to be preserved
during memory reclamation. The current minimum reclaim ratio (1/100
of total dentries) remains too aggressive for such workload. This
patch introduces vfs_cache_pressure_denom for more granular cache
pressure control
The configuration [vfs_cache_pressure=1,
vfs_cache_pressure_denom=10000] effectively maintains the full 20
million dentry cache under memory pressure, preventing datanode
restart performance degradation
- Avoid some jumps in inode_permission() using likely()/unlikely()
- Avid a memory access which is most likely a cache miss when
descending into devcgroup_inode_permission()
- Add fastpath predicts for stat() and fdput()
- Anonymous inodes currently don't come with a proper mode causing
issues in the kernel when we want to add useful VFS debug assert.
Fix that by giving them a proper mode and masking it off when we
report it to userspace which relies on them not having any mode
- Anonymous inodes currently allow to change inode attributes because
the VFS falls back to simple_setattr() if i_op->setattr isn't
implemented. This means the ownership and mode for every single
user of anon_inode_inode can be changed. Block that as it's either
useless or actively harmful. If specific ownership is needed the
respective subsystem should allocate anonymous inodes from their
own private superblock
- Raise SB_I_NODEV and SB_I_NOEXEC on the anonymous inode superblock
- Add proper tests for anonymous inode behavior
- Make it easy to detect proper anonymous inodes and to ensure that
we can detect them in codepaths such as readahead()
Cleanups:
- Port pidfs to the new anon_inode_{g,s}etattr() helpers
- Try to remove the uselib() system call
- Add unlikely branch hint return path for poll
- Add unlikely branch hint on return path for core_sys_select
- Don't allow signals to interrupt getdents copying for fuse
- Provide a size hint to dir_context for during readdir()
- Use writeback_iter directly in mpage_writepages
- Update compression and mtime descriptions in initramfs
documentation
- Update main netfs API document
- Remove useless plus one in super_cache_scan()
- Remove unnecessary NULL-check guards during setns()
- Add separate separate {get,put}_cgroup_ns no-op cases
Fixes:
- Fix typo in root= kernel parameter description
- Use KERN_INFO for infof()|info_plog()|infofc()
- Correct comments of fs_validate_description()
- Mark an unlikely if condition with unlikely() in
vfs_parse_monolithic_sep()
- Delete macro fsparam_u32hex()
- Remove unused and problematic validate_constant_table()
- Fix potential unsigned integer underflow in fs_name()
- Make file-nr output the total allocated file handles"
* tag 'vfs-6.16-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (43 commits)
fs: Pass a folio to page_put_link()
nfs: Use a folio in nfs_get_link()
fs: Convert __page_get_link() to use a folio
fs/read_write: make default_llseek() killable
fs/open: make do_truncate() killable
fs/open: make chmod_common() and chown_common() killable
include/linux/fs.h: add inode_lock_killable()
readdir: supply dir_context.count as readdir buffer size hint
vfs: Add sysctl vfs_cache_pressure_denom for bulk file operations
fuse: don't allow signals to interrupt getdents copying
Documentation: fix typo in root= kernel parameter description
include/cgroup: separate {get,put}_cgroup_ns no-op case
kernel/nsproxy: remove unnecessary guards
fs: use writeback_iter directly in mpage_writepages
fs: remove useless plus one in super_cache_scan()
fs: add S_ANON_INODE
fs: remove uselib() system call
device_cgroup: avoid access to ->i_rdev in the common case in devcgroup_inode_permission()
fs/fs_parse: Remove unused and problematic validate_constant_table()
fs: touch up predicts in inode_permission()
...
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs directory lookup updates from Christian Brauner:
"This contains cleanups for the lookup_one*() family of helpers.
We expose a set of functions with names containing "lookup_one_len"
and others without the "_len". This difference has nothing to do with
"len". It's rater a historical accident that can be confusing.
The functions without "_len" take a "mnt_idmap" pointer. This is found
in the "vfsmount" and that is an important question when choosing
which to use: do you have a vfsmount, or are you "inside" the
filesystem. A related question is "is permission checking relevant
here?".
nfsd and cachefiles *do* have a vfsmount but *don't* use the non-_len
functions. They pass nop_mnt_idmap and refuse to work on filesystems
which have any other idmap.
This work changes nfsd and cachefile to use the lookup_one family of
functions and to explictily pass &nop_mnt_idmap which is consistent
with all other vfs interfaces used where &nop_mnt_idmap is explicitly
passed.
The remaining uses of the "_one" functions do not require permission
checks so these are renamed to be "_noperm" and the permission
checking is removed.
This series also changes these lookup function to take a qstr instead
of separate name and len. In many cases this simplifies the call"
* tag 'vfs-6.16-rc1.async.dir' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
VFS: change lookup_one_common and lookup_noperm_common to take a qstr
Use try_lookup_noperm() instead of d_hash_and_lookup() outside of VFS
VFS: rename lookup_one_len family to lookup_noperm and remove permission check
cachefiles: Use lookup_one() rather than lookup_one_len()
nfsd: Use lookup_one() rather than lookup_one_len()
VFS: improve interface for lookup_one functions
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All callers now have a folio. Pass it to page_put_link(), saving a
hidden call to compound_head(). Also add kernel-doc for page_get_link()
and page_put_link().
Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Link: https://lore.kernel.org/20250514171316.3002934-4-willy@infradead.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Retrieve a folio from the page cache instead of a page and operate
on it. Removes two hidden calls to compound_head().
Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Link: https://lore.kernel.org/20250514171316.3002934-2-willy@infradead.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The routine only encounters errors when people try to access things they
can't, which is a negligible amount of calls.
The only questionable bit might be the pre-existing predict around
MAY_WRITE. Currently the routine is predominantly used for MAY_EXEC, so
this makes some sense.
I verified this straightens out the asm.
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/20250416221626.2710239-2-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Looking at the asm produced by gcc 13.3 for x86-64:
1. may_lookup() usage was not optimized for succeeding, despite the
routine being inlined and rightfully starting with likely(!err)
2. the compiler assumed the path will have an indefinite amount of
slashes to skip, after which the result will be an empty name
As such:
1. predict may_lookup() succeeding
2. check for one slash, no explicit predicts. do roll forward with
skipping more slashes while predicting there is only one
3. predict the path to find was not a mere slash
This also has a side effect of shrinking the file:
add/remove: 1/1 grow/shrink: 0/3 up/down: 934/-1012 (-78)
Function old new delta
link_path_walk - 934 +934
path_parentat 138 112 -26
path_openat 4864 4823 -41
path_lookupat 418 374 -44
link_path_walk.part.constprop 901 - -901
Total: Before=46639, After=46561, chg -0.17%
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/20250412110935.2267703-1-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The functions currently leaving dangling pointers in the passed-in path
leading to hard to debug bugs in the long run. Ensure that the path is
left in pristine state just like we do in e.g., path_parentat() and
other helpers.
Link: https://lore.kernel.org/20250414-rennt-wimmeln-f186c3a780f1@brauner
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The audit code relies on the fact that kern_path_locked() returned a
path even for a negative dentry. If it doesn't find a valid dentry it
immediately calls:
audit_find_parent(d_backing_inode(parent_path.dentry));
which assumes that parent_path.dentry is still valid. But it isn't since
kern_path_locked() has been changed to path_put() also for a negative
dentry.
Fix this by adding a helper that implements the required audit semantics
and allows us to fix the immediate bleeding. We can find a unified
solution for this afterwards.
Link: https://lore.kernel.org/20250414-rennt-wimmeln-f186c3a780f1@brauner
Fixes: 1c3cb50b58c3 ("VFS: change kern_path_locked() and user_path_locked_at() to never return negative dentry")
Reported-and-tested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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getname_flags() should save __user pointer "filename" in filename->uptr.
However, this logic is broken by a recent refactoring. Fix it by passing
__user pointer filename to helper initname().
Fixes: 611851010c74 ("fs: dedup handling of struct filename init and refcounts bumps")
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/20250409220534.3635801-1-song@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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These function already take a qstr of course, but they also currently
take a name/len was well and fill in the qstr.
Now they take a qstr that is already filled in, which is what all the
callers have.
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250319031545.2999807-7-neil@brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The lookup_one_len family of functions is (now) only used internally by
a filesystem on itself either
- in a context where permission checking is irrelevant such as by a
virtual filesystem populating itself, or xfs accessing its ORPHANAGE
or dquota accessing the quota file; or
- in a context where a permission check (MAY_EXEC on the parent) has just
been performed such as a network filesystem finding in "silly-rename"
file in the same directory. This is also the context after the
_parentat() functions where currently lookup_one_qstr_excl() is used.
So the permission check is pointless.
The name "one_len" is unhelpful in understanding the purpose of these
functions and should be changed. Most of the callers pass the len as
"strlen()" so using a qstr and QSTR() can simplify the code.
This patch renames these functions (include lookup_positive_unlocked()
which is part of the family despite the name) to have a name based on
"lookup_noperm". They are changed to receive a 'struct qstr' instead
of separate name and len. In a few cases the use of QSTR() results in a
new call to strlen().
try_lookup_noperm() takes a pointer to a qstr instead of the whole
qstr. This is consistent with d_hash_and_lookup() (which is nearly
identical) and useful for lookup_noperm_unlocked().
The new lookup_noperm_common() doesn't take a qstr yet. That will be
tidied up in a subsequent patch.
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/r/20250319031545.2999807-5-neil@brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>
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|
Vast majority of the time the func returns false.
This avoids a branch to determine whether we are in RCU mode.
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/20250408073641.1799151-1-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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|
The family of functions:
lookup_one()
lookup_one_unlocked()
lookup_one_positive_unlocked()
appear designed to be used by external clients of the filesystem rather
than by filesystems acting on themselves as the lookup_one_len family
are used.
They are used by:
btrfs/ioctl - which is a user-space interface rather than an internal
activity
exportfs - i.e. from nfsd or the open_by_handle_at interface
overlayfs - at access the underlying filesystems
smb/server - for file service
They should be used by nfsd (more than just the exportfs path) and
cachefs but aren't.
It would help if the documentation didn't claim they should "not be
called by generic code".
Also the path component name is passed as "name" and "len" which are
(confusingly?) separate by the "base". In some cases the len in simply
"strlen" and so passing a qstr using QSTR() would make the calling
clearer.
Other callers do pass separate name and len which are stored in a
struct. Sometimes these are already stored in a qstr, other times it
easily could be.
So this patch changes these three functions to receive a 'struct qstr *',
and improves the documentation.
QSTR_LEN() is added to make it easy to pass a QSTR containing a known
len.
[brauner@kernel.org: take a struct qstr pointer]
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/r/20250319031545.2999807-2-neil@brown.name
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 file handling updates from Christian Brauner:
"This contains performance improvements for struct file's new refcount
mechanism and various other performance work:
- The stock kernel transitioning the file to no refs held penalizes
the caller with an extra atomic to block any increments. For cases
where the file is highly likely to be going away this is easily
avoidable.
Add file_ref_put_close() to better handle the common case where
closing a file descriptor also operates on the last reference and
build fput_close_sync() and fput_close() on top of it. This brings
about 1% performance improvement by eliding one atomic in the
common case.
- Predict no error in close() since the vast majority of the time
system call returns 0.
- Reduce the work done in fdget_pos() by predicting that the file was
found and by explicitly comparing the reference count to one and
ignoring the dead zone"
* tag 'vfs-6.15-rc1.file' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
fs: reduce work in fdget_pos()
fs: use fput_close() in path_openat()
fs: use fput_close() in filp_close()
fs: use fput_close_sync() in close()
file: add fput and file_ref_put routines optimized for use when closing a fd
fs: predict no error in close()
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs async dir updates from Christian Brauner:
"This contains cleanups that fell out of the work from async directory
handling:
- Change kern_path_locked() and user_path_locked_at() to never return
a negative dentry. This simplifies the usability of these helpers
in various places
- Drop d_exact_alias() from the remaining place in NFS where it is
still used. This also allows us to drop the d_exact_alias() helper
completely
- Drop an unnecessary call to fh_update() from nfsd_create_locked()
- Change i_op->mkdir() to return a struct dentry
Change vfs_mkdir() to return a dentry provided by the filesystems
which is hashed and positive. This allows us to reduce the number
of cases where the resulting dentry is not positive to very few
cases. The code in these places becomes simpler and easier to
understand.
- Repack DENTRY_* and LOOKUP_* flags"
* tag 'vfs-6.15-rc1.async.dir' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
doc: fix inline emphasis warning
VFS: Change vfs_mkdir() to return the dentry.
nfs: change mkdir inode_operation to return alternate dentry if needed.
fuse: return correct dentry for ->mkdir
ceph: return the correct dentry on mkdir
hostfs: store inode in dentry after mkdir if possible.
Change inode_operations.mkdir to return struct dentry *
nfsd: drop fh_update() from S_IFDIR branch of nfsd_create_locked()
nfs/vfs: discard d_exact_alias()
VFS: add common error checks to lookup_one_qstr_excl()
VFS: change kern_path_locked() and user_path_locked_at() to never return negative dentry
VFS: repack LOOKUP_ bit flags.
VFS: repack DENTRY_ flags.
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull misc vfs updates from Christian Brauner:
"Features:
- Add CONFIG_DEBUG_VFS infrastucture:
- Catch invalid modes in open
- Use the new debug macros in inode_set_cached_link()
- Use debug-only asserts around fd allocation and install
- Place f_ref to 3rd cache line in struct file to resolve false
sharing
Cleanups:
- Start using anon_inode_getfile_fmode() helper in various places
- Don't take f_lock during SEEK_CUR if exclusion is guaranteed by
f_pos_lock
- Add unlikely() to kcmp()
- Remove legacy ->remount_fs method from ecryptfs after port to the
new mount api
- Remove invalidate_inodes() in favour of evict_inodes()
- Simplify ep_busy_loopER by removing unused argument
- Avoid mmap sem relocks when coredumping with many missing pages
- Inline getname()
- Inline new_inode_pseudo() and de-staticize alloc_inode()
- Dodge an atomic in putname if ref == 1
- Consistently deref the files table with rcu_dereference_raw()
- Dedup handling of struct filename init and refcounts bumps
- Use wq_has_sleeper() in end_dir_add()
- Drop the lock trip around I_NEW wake up in evict()
- Load the ->i_sb pointer once in inode_sb_list_{add,del}
- Predict not reaching the limit in alloc_empty_file()
- Tidy up do_sys_openat2() with likely/unlikely
- Call inode_sb_list_add() outside of inode hash lock
- Sort out fd allocation vs dup2 race commentary
- Turn page_offset() into a wrapper around folio_pos()
- Remove locking in exportfs around ->get_parent() call
- try_lookup_one_len() does not need any locks in autofs
- Fix return type of several functions from long to int in open
- Fix return type of several functions from long to int in ioctls
Fixes:
- Fix watch queue accounting mismatch"
* tag 'vfs-6.15-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (30 commits)
fs: sort out fd allocation vs dup2 race commentary, take 2
fs: call inode_sb_list_add() outside of inode hash lock
fs: tidy up do_sys_openat2() with likely/unlikely
fs: predict not reaching the limit in alloc_empty_file()
fs: load the ->i_sb pointer once in inode_sb_list_{add,del}
fs: drop the lock trip around I_NEW wake up in evict()
fs: use wq_has_sleeper() in end_dir_add()
VFS/autofs: try_lookup_one_len() does not need any locks
fs: dedup handling of struct filename init and refcounts bumps
fs: consistently deref the files table with rcu_dereference_raw()
exportfs: remove locking around ->get_parent() call.
fs: use debug-only asserts around fd allocation and install
fs: dodge an atomic in putname if ref == 1
vfs: Remove invalidate_inodes()
ecryptfs: remove NULL remount_fs from super_operations
watch_queue: fix pipe accounting mismatch
fs: place f_ref to 3rd cache line in struct file to resolve false sharing
epoll: simplify ep_busy_loop by removing always 0 argument
fs: Turn page_offset() into a wrapper around folio_pos()
kcmp: improve performance adding an unlikely hint to task comparisons
...
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try_lookup_one_len() is identical to lookup_one_unlocked() except that
it doesn't include the call to lookup_slow(). The latter doesn't need
the inode to be locked, so the former cannot either.
So fix the documentation, remove the WARN_ON and fix the only caller to
not take the lock.
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/174190517441.9342.5956460781380903128@noble.neil.brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>
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No functional changes.
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20250313142744.1323281-1-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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While the structure is refcounted, the only consumer incrementing it is
audit and even then the atomic operation is only needed when it
interacts with io_uring.
If putname spots a count of 1, there is no legitimate way for anyone to
bump it.
If audit is disabled, the count is guaranteed to be 1, which
consistently elides the atomic for all path lookups. If audit is
enabled, it still manages to elide the last decrement.
Note the patch does not do anything to prevent audit from suffering
atomics. See [1] and [2] for a different approach.
Benchmarked on Sapphire Rapids issuing access() (ops/s):
before: 5106246
after: 5269678 (+3%)
Link 1: https://lore.kernel.org/linux-fsdevel/20250307161155.760949-1-mjguzik@gmail.com/
Link 2: https://lore.kernel.org/linux-fsdevel/20250307164216.GI2023217@ZenIV/
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20250311181804.1165758-1-mjguzik@gmail.com
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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This bumps failing open rate by 1.7% on Sapphire Rapids by avoiding one
atomic.
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20250305123644.554845-5-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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vfs_mkdir() does not guarantee to leave the child dentry hashed or make
it positive on success, and in many such cases the filesystem had to use
a different dentry which it can now return.
This patch changes vfs_mkdir() to return the dentry provided by the
filesystems which is hashed and positive when provided. This reduces
the number of cases where the resulting dentry is not positive to a
handful which don't deserve extra efforts.
The only callers of vfs_mkdir() which are interested in the resulting
inode are in-kernel filesystem clients: cachefiles, nfsd, smb/server.
The only filesystems that don't reliably provide the inode are:
- kernfs, tracefs which these clients are unlikely to be interested in
- cifs in some configurations would need to do a lookup to find the
created inode, but doesn't. cifs cannot be exported via NFS, is
unlikely to be used by cachefiles, and smb/server only has a soft
requirement for the inode, so this is unlikely to be a problem in
practice.
- hostfs, nfs, cifs may need to do a lookup (rarely for NFS) and it is
possible for a race to make that lookup fail. Actual failure
is unlikely and providing callers handle negative dentries graceful
they will fail-safe.
So this patch removes the lookup code in nfsd and smb/server and adjusts
them to fail safe if a negative dentry is provided:
- cache-files already fails safe by restarting the task from the
top - it still does with this change, though it no longer calls
cachefiles_put_directory() as that will crash if the dentry is
negative.
- nfsd reports "Server-fault" which it what it used to do if the lookup
failed. This will never happen on any file-systems that it can actually
export, so this is of no consequence. I removed the fh_update()
call as that is not needed and out-of-place. A subsequent
nfsd_create_setattr() call will call fh_update() when needed.
- smb/server only wants the inode to call ksmbd_smb_inherit_owner()
which updates ->i_uid (without calling notify_change() or similar)
which can be safely skipping on cifs (I hope).
If a different dentry is returned, the first one is put. If necessary
the fact that it is new can be determined by comparing pointers. A new
dentry will certainly have a new pointer (as the old is put after the
new is obtained).
Similarly if an error is returned (via ERR_PTR()) the original dentry is
put.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250227013949.536172-7-neilb@suse.de
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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Some filesystems, such as NFS, cifs, ceph, and fuse, do not have
complete control of sequencing on the actual filesystem (e.g. on a
different server) and may find that the inode created for a mkdir
request already exists in the icache and dcache by the time the mkdir
request returns. For example, if the filesystem is mounted twice the
directory could be visible on the other mount before it is on the
original mount, and a pair of name_to_handle_at(), open_by_handle_at()
calls could instantiate the directory inode with an IS_ROOT() dentry
before the first mkdir returns.
This means that the dentry passed to ->mkdir() may not be the one that
is associated with the inode after the ->mkdir() completes. Some
callers need to interact with the inode after the ->mkdir completes and
they currently need to perform a lookup in the (rare) case that the
dentry is no longer hashed.
This lookup-after-mkdir requires that the directory remains locked to
avoid races. Planned future patches to lock the dentry rather than the
directory will mean that this lookup cannot be performed atomically with
the mkdir.
To remove this barrier, this patch changes ->mkdir to return the
resulting dentry if it is different from the one passed in.
Possible returns are:
NULL - the directory was created and no other dentry was used
ERR_PTR() - an error occurred
non-NULL - this other dentry was spliced in
This patch only changes file-systems to return "ERR_PTR(err)" instead of
"err" or equivalent transformations. Subsequent patches will make
further changes to some file-systems to return a correct dentry.
Not all filesystems reliably result in a positive hashed dentry:
- NFS, cifs, hostfs will sometimes need to perform a lookup of
the name to get inode information. Races could result in this
returning something different. Note that this lookup is
non-atomic which is what we are trying to avoid. Placing the
lookup in filesystem code means it only happens when the filesystem
has no other option.
- kernfs and tracefs leave the dentry negative and the ->revalidate
operation ensures that lookup will be called to correctly populate
the dentry. This could be fixed but I don't think it is important
to any of the users of vfs_mkdir() which look at the dentry.
The recommendation to use
d_drop();d_splice_alias()
is ugly but fits with current practice. A planned future patch will
change this.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250227013949.536172-2-neilb@suse.de
Signed-off-by: Christian Brauner <brauner@kernel.org>
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It is merely a trivial wrapper around getname_flags which adds a zeroed
argument, no point paying for an extra call.
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20250206000105.432528-1-mjguzik@gmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20250209185523.745956-3-mjguzik@gmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Fuse allows the value of a symlink to change and this property is exploited
by some filesystems (e.g. CVMFS).
It has been observed, that sometimes after changing the symlink contents,
the value is truncated to the old size.
This is caused by fuse_getattr() racing with fuse_reverse_inval_inode().
fuse_reverse_inval_inode() updates the fuse_inode's attr_version, which
results in fuse_change_attributes() exiting before updating the cached
attributes
This is okay, as the cached attributes remain invalid and the next call to
fuse_change_attributes() will likely update the inode with the correct
values.
The reason this causes problems is that cached symlinks will be
returned through page_get_link(), which truncates the symlink to
inode->i_size. This is correct for filesystems that don't mutate
symlinks, but in this case it causes bad behavior.
The solution is to just remove this truncation. This can cause a
regression in a filesystem that relies on supplying a symlink larger than
the file size, but this is unlikely. If that happens we'd need to make
this behavior conditional.
Reported-by: Laura Promberger <laura.promberger@cern.ch>
Tested-by: Sam Lewis <samclewis@google.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Link: https://lore.kernel.org/r/20250220100258.793363-1-mszeredi@redhat.com
Reviewed-by: Bernd Schubert <bschubert@ddn.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Callers of lookup_one_qstr_excl() often check if the result is negative or
positive.
These changes can easily be moved into lookup_one_qstr_excl() by checking the
lookup flags:
LOOKUP_CREATE means it is NOT an error if the name doesn't exist.
LOOKUP_EXCL means it IS an error if the name DOES exist.
This patch adds these checks, then removes error checks from callers,
and ensures that appropriate flags are passed.
This subtly changes the meaning of LOOKUP_EXCL. Previously it could
only accompany LOOKUP_CREATE. Now it can accompany LOOKUP_RENAME_TARGET
as well. A couple of small changes are needed to accommodate this. The
NFS change is functionally a no-op but ensures nfs_is_exclusive_create() does
exactly what the name says.
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250217003020.3170652-3-neilb@suse.de
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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negative dentry
No callers of kern_path_locked() or user_path_locked_at() want a
negative dentry. So change them to return -ENOENT instead. This
simplifies callers.
This results in a subtle change to bcachefs in that an ioctl will now
return -ENOENT in preference to -EXDEV. I believe this restores the
behaviour to what it was prior to
Commit bbe6a7c899e7 ("bch2_ioctl_subvolume_destroy(): fix locking")
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250217003020.3170652-2-neilb@suse.de
Acked-by: Paul Moore <paul@paul-moore.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs d_revalidate updates from Al Viro:
"Provide stable parent and name to ->d_revalidate() instances
Most of the filesystem methods where we care about dentry name and
parent have their stability guaranteed by the callers;
->d_revalidate() is the major exception.
It's easy enough for callers to supply stable values for expected name
and expected parent of the dentry being validated. That kills quite a
bit of boilerplate in ->d_revalidate() instances, along with a bunch
of races where they used to access ->d_name without sufficient
precautions"
* tag 'pull-revalidate' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
9p: fix ->rename_sem exclusion
orangefs_d_revalidate(): use stable parent inode and name passed by caller
ocfs2_dentry_revalidate(): use stable parent inode and name passed by caller
nfs: fix ->d_revalidate() UAF on ->d_name accesses
nfs{,4}_lookup_validate(): use stable parent inode passed by caller
gfs2_drevalidate(): use stable parent inode and name passed by caller
fuse_dentry_revalidate(): use stable parent inode and name passed by caller
vfat_revalidate{,_ci}(): use stable parent inode passed by caller
exfat_d_revalidate(): use stable parent inode passed by caller
fscrypt_d_revalidate(): use stable parent inode passed by caller
ceph_d_revalidate(): propagate stable name down into request encoding
ceph_d_revalidate(): use stable parent inode passed by caller
afs_d_revalidate(): use stable name and parent inode passed by caller
Pass parent directory inode and expected name to ->d_revalidate()
generic_ci_d_compare(): use shortname_storage
ext4 fast_commit: make use of name_snapshot primitives
dissolve external_name.u into separate members
make take_dentry_name_snapshot() lockless
dcache: back inline names with a struct-wrapped array of unsigned long
make sure that DNAME_INLINE_LEN is a multiple of word size
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Add the const qualifier to all the ctl_tables in the tree except for
watchdog_hardlockup_sysctl, memory_allocation_profiling_sysctls,
loadpin_sysctl_table and the ones calling register_net_sysctl (./net,
drivers/inifiniband dirs). These are special cases as they use a
registration function with a non-const qualified ctl_table argument or
modify the arrays before passing them on to the registration function.
Constifying ctl_table structs will prevent the modification of
proc_handler function pointers as the arrays would reside in .rodata.
This is made possible after commit 78eb4ea25cd5 ("sysctl: treewide:
constify the ctl_table argument of proc_handlers") constified all the
proc_handlers.
Created this by running an spatch followed by a sed command:
Spatch:
virtual patch
@
depends on !(file in "net")
disable optional_qualifier
@
identifier table_name != {
watchdog_hardlockup_sysctl,
iwcm_ctl_table,
ucma_ctl_table,
memory_allocation_profiling_sysctls,
loadpin_sysctl_table
};
@@
+ const
struct ctl_table table_name [] = { ... };
sed:
sed --in-place \
-e "s/struct ctl_table .table = &uts_kern/const struct ctl_table *table = \&uts_kern/" \
kernel/utsname_sysctl.c
Reviewed-by: Song Liu <song@kernel.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org> # for kernel/trace/
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> # SCSI
Reviewed-by: Darrick J. Wong <djwong@kernel.org> # xfs
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Corey Minyard <cminyard@mvista.com>
Acked-by: Wei Liu <wei.liu@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Bill O'Donnell <bodonnel@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Acked-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Joel Granados <joel.granados@kernel.org>
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