kernel/linux.git/fs/dcache.c, branch v6.12.80

nfs/vfs: discard d_exact_alias()

2025-12-18T12:55:17+00:00

[ Upstream commit 3ff6c8707c9a0116d00982851ec1216a42053ace ] d_exact_alias() is a descendent of d_add_unique() which was introduced 20 years ago mostly likely to work around problems with NFS servers of the time. It is now not used in several situations were it was originally needed and there have been no reports of problems - presumably the old NFS servers have been improved. This only place it is now use is in NFSv4 code and the old problematic servers are thought to have been v2/v3 only. There is no clear benefit in reusing a unhashed() dentry which happens to have the same name as the dentry we are adding. So this patch removes d_exact_alias() and the one place that it is used. Cc: Trond Myklebust Signed-off-by: NeilBrown Link: https://lore.kernel.org/r/20250226062135.2043651-2-neilb@suse.de Signed-off-by: Christian Brauner Stable-dep-of: 0f900f11002f ("NFS: Initialise verifiers for visible dentries in _nfs4_open_and_get_state") Signed-off-by: Sasha Levin

vfs: Don't leak disconnected dentries on umount

2025-10-23T14:20:43+00:00

[ Upstream commit 56094ad3eaa21e6621396cc33811d8f72847a834 ] When user calls open_by_handle_at() on some inode that is not cached, we will create disconnected dentry for it. If such dentry is a directory, exportfs_decode_fh_raw() will then try to connect this dentry to the dentry tree through reconnect_path(). It may happen for various reasons (such as corrupted fs or race with rename) that the call to lookup_one_unlocked() in reconnect_one() will fail to find the dentry we are trying to reconnect and instead create a new dentry under the parent. Now this dentry will not be marked as disconnected although the parent still may well be disconnected (at least in case this inconsistency happened because the fs is corrupted and .. doesn't point to the real parent directory). This creates inconsistency in disconnected flags but AFAICS it was mostly harmless. At least until commit f1ee616214cb ("VFS: don't keep disconnected dentries on d_anon") which removed adding of most disconnected dentries to sb->s_anon list. Thus after this commit cleanup of disconnected dentries implicitely relies on the fact that dput() will immediately reclaim such dentries. However when some leaf dentry isn't marked as disconnected, as in the scenario described above, the reclaim doesn't happen and the dentries are "leaked". Memory reclaim can eventually reclaim them but otherwise they stay in memory and if umount comes first, we hit infamous "Busy inodes after unmount" bug. Make sure all dentries created under a disconnected parent are marked as disconnected as well. Reported-by: syzbot+1d79ebe5383fc016cf07@syzkaller.appspotmail.com Fixes: f1ee616214cb ("VFS: don't keep disconnected dentries on d_anon") CC: stable@vger.kernel.org Signed-off-by: Jan Kara Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

d_alloc_parallel(): set DCACHE_PAR_LOOKUP earlier

2025-10-23T14:20:43+00:00

[ Upstream commit e95db51c81f54dd12ea465b5127e4786f62a1095 ] Do that before new dentry is visible anywhere. It does create a new possible state for dentries present in ->d_children/->d_sib - DCACHE_PAR_LOOKUP present, negative, unhashed, not in in-lookup hash chains, refcount positive. Those are going to be skipped by all tree-walkers (both d_walk() callbacks in fs/dcache.c and explicit loops over children/sibling lists elsewhere) and dput() is fine with those. NOTE: dropping the final reference to a "normal" in-lookup dentry (in in-lookup hash) is a bug - somebody must've forgotten to call d_lookup_done() on it and bad things will happen. With those it's OK; if/when we get around to making __dentry_kill() complain about such breakage, remember that predicate to check should *not* be just d_in_lookup(victim) but rather a combination of that with !hlist_bl_unhashed(&victim->d_u.d_in_lookup_hash). Might be worth considering later... Reviewed-by: Christian Brauner Signed-off-by: Al Viro Stable-dep-of: 56094ad3eaa2 ("vfs: Don't leak disconnected dentries on umount") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

Merge tag 'vfs-6.12.misc' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs

2024-09-16T06:35:09+00:00

Pull misc vfs updates from Christian Brauner: "This contains the usual pile of misc updates: Features: - Add F_CREATED_QUERY fcntl() that allows userspace to query whether a file was actually created. Often userspace wants to know whether an O_CREATE request did actually create a file without using O_EXCL. The current logic is that to first attempts to open the file without O_CREAT | O_EXCL and if ENOENT is returned userspace tries again with both flags. If that succeeds all is well. If it now reports EEXIST it retries. That works fairly well but some corner cases make this more involved. If this operates on a dangling symlink the first openat() without O_CREAT | O_EXCL will return ENOENT but the second openat() with O_CREAT | O_EXCL will fail with EEXIST. The reason is that openat() without O_CREAT | O_EXCL follows the symlink while O_CREAT | O_EXCL doesn't for security reasons. So it's not something we can really change unless we add an explicit opt-in via O_FOLLOW which seems really ugly. All available workarounds are really nasty (fanotify, bpf lsm etc) so add a simple fcntl(). - Try an opportunistic lookup for O_CREAT. Today, when opening a file we'll typically do a fast lookup, but if O_CREAT is set, the kernel always takes the exclusive inode lock. This was likely done with the expectation that O_CREAT means that we always expect to do the create, but that's often not the case. Many programs set O_CREAT even in scenarios where the file already exists (see related F_CREATED_QUERY patch motivation above). The series contained in the pr rearranges the pathwalk-for-open code to also attempt a fast_lookup in certain O_CREAT cases. If a positive dentry is found, the inode_lock can be avoided altogether and it can stay in rcuwalk mode for the last step_into. - Expose the 64 bit mount id via name_to_handle_at() Now that we provide a unique 64-bit mount ID interface in statx(2), we can now provide a race-free way for name_to_handle_at(2) to provide a file handle and corresponding mount without needing to worry about racing with /proc/mountinfo parsing or having to open a file just to do statx(2). While this is not necessary if you are using AT_EMPTY_PATH and don't care about an extra statx(2) call, users that pass full paths into name_to_handle_at(2) need to know which mount the file handle comes from (to make sure they don't try to open_by_handle_at a file handle from a different filesystem) and switching to AT_EMPTY_PATH would require allocating a file for every name_to_handle_at(2) call - Add a per dentry expire timeout to autofs There are two fairly well known automounter map formats, the autofs format and the amd format (more or less System V and Berkley). Some time ago Linux autofs added an amd map format parser that implemented a fair amount of the amd functionality. This was done within the autofs infrastructure and some functionality wasn't implemented because it either didn't make sense or required extra kernel changes. The idea was to restrict changes to be within the existing autofs functionality as much as possible and leave changes with a wider scope to be considered later. One of these changes is implementing the amd options: 1) "unmount", expire this mount according to a timeout (same as the current autofs default). 2) "nounmount", don't expire this mount (same as setting the autofs timeout to 0 except only for this specific mount) . 3) "utimeout=", expire this mount using the specified timeout (again same as setting the autofs timeout but only for this mount) To implement these options per-dentry expire timeouts need to be implemented for autofs indirect mounts. This is because all map keys (mounts) for autofs indirect mounts use an expire timeout stored in the autofs mount super block info. structure and all indirect mounts use the same expire timeout. Fixes: - Fix missing fput for FSCONFIG_SET_FD in autofs - Use param->file for FSCONFIG_SET_FD in coda - Delete the 'fs/netfs' proc subtreee when netfs module exits - Make sure that struct uid_gid_map fits into a single cacheline - Don't flush in-flight wb switches for superblocks without cgroup writeback - Correcting the idmapping mount example in the idmapping documentation - Fix a race between evice_inodes() and find_inode() and iput() - Refine the show_inode_state() macro definition in writeback code - Prevent dump_mapping() from accessing invalid dentry.d_name.name - Show actual source for debugfs in /proc/mounts - Annotate data-race of busy_poll_usecs in eventpoll - Don't WARN for racy path_noexec check in exec code - Handle OOM on mnt_warn_timestamp_expiry() - Fix some spelling in the iomap design documentation - Fix typo in procfs comment - Fix typo in fs/namespace.c comment Cleanups: - Add the VFS git tree to the MAINTAINERS file - Move FMODE_UNSIGNED_OFFSET to fop_flags freeing up another f_mode bit in struct file bringing us to 5 free f_mode bits - Remove the __I_DIO_WAKEUP bit from i_state flags as we can simplify the wait mechanism - Remove the unused path_put_init() helper - Replace a __u32 with u32 for s_fsnotify_mask as __u32 is uapi specific - Replace the unsigned long i_state member with a u32 i_state member in struct inode freeing up 4 bytes in struct inode. Instead of using the bit based wait apis we're now using the var event apis and using the individual bytes of the i_state member to wait on state changes - Explain how per-syscall AT_* flags should be allocated - Use in_group_or_capable() helper to simplify the posix acl mode update code - Switch to LIST_HEAD() in fsync_buffers_list() to simplify the code - Removed comment about d_rcu_to_refcount() as that function doesn't exist anymore - Add kernel documentation for lookup_fast() - Don't re-zero evenpoll fields - Remove outdated comment after close_fd() - Fix imprecise wording in comment about the pipe filesystem - Drop GFP_NOFAIL mode from alloc_page_buffers - Missing blank line warnings and struct declaration improved in file_table - Annotate struct poll_list with __counted_by() - Remove the unused read parameter in percpu-rwsem - Remove linux/prefetch.h include from direct-io code - Use kmemdup_array instead of kmemdup for multiple allocation in mnt_idmapping code - Remove unused mnt_cursor_del() declaration Performance tweaks: - Dodge smp_mb in break_lease and break_deleg in the common case - Only read fops once in fops_{get,put}() - Use RCU in ilookup() - Elide smp_mb in iversion handling in the common case - Drop one lock trip in evict()" * tag 'vfs-6.12.misc' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs: (58 commits) uidgid: make sure we fit into one cacheline proc: Fix typo in the comment fs/pipe: Correct imprecise wording in comment fhandle: expose u64 mount id to name_to_handle_at(2) uapi: explain how per-syscall AT_* flags should be allocated fs: drop GFP_NOFAIL mode from alloc_page_buffers writeback: Refine the show_inode_state() macro definition fs/inode: Prevent dump_mapping() accessing invalid dentry.d_name.name mnt_idmapping: Use kmemdup_array instead of kmemdup for multiple allocation netfs: Delete subtree of 'fs/netfs' when netfs module exits fs: use LIST_HEAD() to simplify code inode: make i_state a u32 inode: port __I_LRU_ISOLATING to var event vfs: fix race between evice_inodes() and find_inode()&iput() inode: port __I_NEW to var event inode: port __I_SYNC to var event fs: reorder i_state bits fs: add i_state helpers MAINTAINERS: add the VFS git tree fs: s/__u32/u32/ for s_fsnotify_mask ...

inode: port __I_NEW to var event

2024-08-30T06:22:39+00:00

Port the __I_NEW mechanism to use the new var event mechanism. Link: https://lore.kernel.org/r/20240823-work-i_state-v3-4-5cd5fd207a57@kernel.org Reviewed-by: Josef Bacik Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

fs: remove comment about d_rcu_to_refcount

2024-08-30T06:22:32+00:00

This function no longer exists. Signed-off-by: Jeff Layton Link: https://lore.kernel.org/r/20240802-openfast-v1-1-a1cff2a33063@kernel.org Signed-off-by: Christian Brauner

dcache: keep dentry_hashtable or d_hash_shift even when not used

2024-08-30T00:25:50+00:00

The runtime constant feature removes all the users of these variables, allowing the compiler to optimize them away. It's quite difficult to extract their values from the kernel text, and the memory saved by removing them is tiny, and it was never the point of this optimization. Since the dentry_hashtable is a core data structure, it's valuable for debugging tools to be able to read it easily. For instance, scripts built on drgn, like the dentrycache script[1], rely on it to be able to perform diagnostics on the contents of the dcache. Annotate it as used, so the compiler doesn't discard it. Link: https://github.com/oracle-samples/drgn-tools/blob/3afc56146f54d09dfd1f6d3c1b7436eda7e638be/drgn_tools/dentry.py#L325-L355 [1] Fixes: e3c92e81711d ("runtime constants: add x86 architecture support") Signed-off-by: Stephen Brennan Signed-off-by: Linus Torvalds

sysctl: treewide: constify the ctl_table argument of proc_handlers

2024-07-24T18:59:29+00:00

const qualify the struct ctl_table argument in the proc_handler function signatures. This is a prerequisite to moving the static ctl_table structs into .rodata data which will ensure that proc_handler function pointers cannot be modified. This patch has been generated by the following coccinelle script: ``` virtual patch @r1@ identifier ctl, write, buffer, lenp, ppos; identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)"; @@ int func( - struct ctl_table *ctl + const struct ctl_table *ctl ,int write, void *buffer, size_t *lenp, loff_t *ppos); @r2@ identifier func, ctl, write, buffer, lenp, ppos; @@ int func( - struct ctl_table *ctl + const struct ctl_table *ctl ,int write, void *buffer, size_t *lenp, loff_t *ppos) { ... } @r3@ identifier func; @@ int func( - struct ctl_table * + const struct ctl_table * ,int , void *, size_t *, loff_t *); @r4@ identifier func, ctl; @@ int func( - struct ctl_table *ctl + const struct ctl_table *ctl ,int , void *, size_t *, loff_t *); @r5@ identifier func, write, buffer, lenp, ppos; @@ int func( - struct ctl_table * + const struct ctl_table * ,int write, void *buffer, size_t *lenp, loff_t *ppos); ``` * Code formatting was adjusted in xfs_sysctl.c to comply with code conventions. The xfs_stats_clear_proc_handler, xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where adjusted. * The ctl_table argument in proc_watchdog_common was const qualified. This is called from a proc_handler itself and is calling back into another proc_handler, making it necessary to change it as part of the proc_handler migration. Co-developed-by: Thomas Weißschuh Signed-off-by: Thomas Weißschuh Co-developed-by: Joel Granados Signed-off-by: Joel Granados

Merge tag 'vfs-6.11.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2024-07-15T17:52:51+00:00

Pull misc vfs updates from Christian Brauner: "Features: - Support passing NULL along AT_EMPTY_PATH for statx(). NULL paths with any flag value other than AT_EMPTY_PATH go the usual route and end up with -EFAULT to retain compatibility (Rust is abusing calls of the sort to detect availability of statx) This avoids path lookup code, lockref management, memory allocation and in case of NULL path userspace memory access (which can be quite expensive with SMAP on x86_64) - Don't block i_writecount during exec. Remove the deny_write_access() mechanism for executables - Relax open_by_handle_at() permissions in specific cases where we can prove that the caller had sufficient privileges to open a file - Switch timespec64 fields in struct inode to discrete integers freeing up 4 bytes Fixes: - Fix false positive circular locking warning in hfsplus - Initialize hfs_inode_info after hfs_alloc_inode() in hfs - Avoid accidental overflows in vfs_fallocate() - Don't interrupt fallocate with EINTR in tmpfs to avoid constantly restarting shmem_fallocate() - Add missing quote in comment in fs/readdir Cleanups: - Don't assign and test in an if statement in mqueue. Move the assignment out of the if statement - Reflow the logic in may_create_in_sticky() - Remove the usage of the deprecated ida_simple_xx() API from procfs - Reject FSCONFIG_CMD_CREATE_EXCL requets that depend on the new mount api early - Rename variables in copy_tree() to make it easier to understand - Replace WARN(down_read_trylock, ...) abuse with proper asserts in various places in the VFS - Get rid of user_path_at_empty() and drop the empty argument from getname_flags() - Check for error while copying and no path in one branch in getname_flags() - Avoid redundant smp_mb() for THP handling in do_dentry_open() - Rename parent_ino to d_parent_ino and make it use RCU - Remove unused header include in fs/readdir - Export in_group_capable() helper and switch f2fs and fuse over to it instead of open-coding the logic in both places" * tag 'vfs-6.11.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (27 commits) ipc: mqueue: remove assignment from IS_ERR argument vfs: rename parent_ino to d_parent_ino and make it use RCU vfs: support statx(..., NULL, AT_EMPTY_PATH, ...) stat: use vfs_empty_path() helper fs: new helper vfs_empty_path() fs: reflow may_create_in_sticky() vfs: remove redundant smp_mb for thp handling in do_dentry_open fuse: Use in_group_or_capable() helper f2fs: Use in_group_or_capable() helper fs: Export in_group_or_capable() vfs: reorder checks in may_create_in_sticky hfs: fix to initialize fields of hfs_inode_info after hfs_alloc_inode() proc: Remove usage of the deprecated ida_simple_xx() API hfsplus: fix to avoid false alarm of circular locking Improve readability of copy_tree vfs: shave a branch in getname_flags vfs: retire user_path_at_empty and drop empty arg from getname_flags vfs: stop using user_path_at_empty in do_readlinkat tmpfs: don't interrupt fallocate with EINTR fs: don't block i_writecount during exec ...

Merge branch 'runtime-constants'

2024-07-15T15:36:13+00:00

Merge runtime constants infrastructure with implementations for x86 and arm64. This is one of four branches that came out of me looking at profiles of my kernel build filesystem load on my 128-core Altra arm64 system, where pathname walking and the user copies (particularly strncpy_from_user() for fetching the pathname from user space) is very hot. This is a very specialized "instruction alternatives" model where the dentry hash pointer and hash count will be constants for the lifetime of the kernel, but the allocation are not static but done early during the kernel boot. In order to avoid the pointer load and dynamic shift, we just rewrite the constants in the instructions in place. We can't use the "generic" alternative instructions infrastructure, because different architectures do it very differently, and it's actually simpler to just have very specific helpers, with a fallback to the generic ("old") model of just using variables for architectures that do not implement the runtime constant patching infrastructure. Link: https://lore.kernel.org/all/CAHk-=widPe38fUNjUOmX11ByDckaeEo9tN4Eiyke9u1SAtu9sA@mail.gmail.com/ * runtime-constants: arm64: add 'runtime constant' support runtime constants: add x86 architecture support runtime constants: add default dummy infrastructure vfs: dcache: move hashlen_hash() from callers into d_hash()