kernel.git/Documentation/filesystems/porting.rst, branch master

Merge tag 'vfs-7.0-rc1.misc.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2026-02-16T21:00:36Z

Pull more misc vfs updates from Christian Brauner: "Features: - Optimize close_range() from O(range size) to O(active FDs) by using find_next_bit() on the open_fds bitmap instead of linearly scanning the entire requested range. This is a significant improvement for large-range close operations on sparse file descriptor tables. - Add FS_XFLAG_VERITY file attribute for fs-verity files, retrievable via FS_IOC_FSGETXATTR and file_getattr(). The flag is read-only. Add tracepoints for fs-verity enable and verify operations, replacing the previously removed debug printk's. - Prevent nfsd from exporting special kernel filesystems like pidfs and nsfs. These filesystems have custom ->open() and ->permission() export methods that are designed for open_by_handle_at(2) only and are incompatible with nfsd. Update the exportfs documentation accordingly. Fixes: - Fix KMSAN uninit-value in ovl_fill_real() where strcmp() was used on a non-null-terminated decrypted directory entry name from fscrypt. This triggered on encrypted lower layers when the decrypted name buffer contained uninitialized tail data. The fix also adds VFS-level name_is_dot(), name_is_dotdot(), and name_is_dot_dotdot() helpers, replacing various open-coded "." and ".." checks across the tree. - Fix read-only fsflags not being reset together with xflags in vfs_fileattr_set(). Currently harmless since no read-only xflags overlap with flags, but this would cause inconsistencies for any future shared read-only flag - Return -EREMOTE instead of -ESRCH from PIDFD_GET_INFO when the target process is in a different pid namespace. This lets userspace distinguish "process exited" from "process in another namespace", matching glibc's pidfd_getpid() behavior Cleanups: - Use C-string literals in the Rust seq_file bindings, replacing the kernel::c_str!() macro (available since Rust 1.77) - Fix typo in d_walk_ret enum comment, add porting notes for the readlink_copy() calling convention change" * tag 'vfs-7.0-rc1.misc.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: fs: add porting notes about readlink_copy() pidfs: return -EREMOTE when PIDFD_GET_INFO is called on another ns nfsd: do not allow exporting of special kernel filesystems exportfs: clarify the documentation of open()/permission() expotrfs ops fsverity: add tracepoints fs: add FS_XFLAG_VERITY for fs-verity files rust: seq_file: replace `kernel::c_str!` with C-Strings fs: dcache: fix typo in enum d_walk_ret comment ovl: use name_is_dot* helpers in readdir code fs: add helpers name_is_dot{,dot,_dotdot} ovl: Fix uninit-value in ovl_fill_real fs: reset read-only fsflags together with xflags fs/file: optimize close_range() complexity from O(N) to O(Sparse)

Merge tag 'pull-filename' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2026-02-10T00:58:28Z

Pull vfs 'struct filename' updates from Al Viro: "[Mostly] sanitize struct filename handling" * tag 'pull-filename' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (68 commits) sysfs(2): fs_index() argument is _not_ a pathname alpha: switch osf_mount() to strndup_user() ksmbd: use CLASS(filename_kernel) mqueue: switch to CLASS(filename) user_statfs(): switch to CLASS(filename) statx: switch to CLASS(filename_maybe_null) quotactl_block(): switch to CLASS(filename) chroot(2): switch to CLASS(filename) move_mount(2): switch to CLASS(filename_maybe_null) namei.c: switch user pathname imports to CLASS(filename{,_flags}) namei.c: convert getname_kernel() callers to CLASS(filename_kernel) do_f{chmod,chown,access}at(): use CLASS(filename_uflags) do_readlinkat(): switch to CLASS(filename_flags) do_sys_truncate(): switch to CLASS(filename) do_utimes_path(): switch to CLASS(filename_uflags) chdir(2): unspaghettify a bit... do_fchownat(): unspaghettify a bit... fspick(2): use CLASS(filename_flags) name_to_handle_at(): use CLASS(filename_uflags) vfs_open_tree(): use CLASS(filename_uflags) ...

Merge tag 'vfs-7.0-rc1.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2026-02-09T22:43:47Z

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

fs: add porting notes about readlink_copy()

2026-02-03T14:17:34Z

Calling convention has changed in ea382199071931d1 ("vfs: support caching symlink lengths in inodes") Signed-off-by: Mateusz Guzik Link: https://patch.msgid.link/20260203130032.315177-1-mjguzik@gmail.com Signed-off-by: Christian Brauner

non-consuming variants of do_{unlinkat,rmdir}()

2026-01-16T17:51:50Z

similar to previous commit; replacements are filename_{unlinkat,rmdir}() Signed-off-by: Al Viro

non-consuming variant of do_mknodat()

2026-01-16T17:49:26Z

similar to previous commit; replacement is filename_mknodat() Signed-off-by: Al Viro

non-consuming variant of do_mkdirat()

2026-01-16T17:48:49Z

similar to previous commit; replacement is filename_mkdirat() Signed-off-by: Al Viro

non-consuming variant of do_symlinkat()

2026-01-16T17:48:16Z

similar to previous commit; replacement is filename_symlinkat() Signed-off-by: Al Viro

non-consuming variant of do_linkat()

2026-01-16T17:47:42Z

similar to previous commit; replacement is filename_linkat() Signed-off-by: Al Viro

non-consuming variant of do_renameat2()

2026-01-16T17:46:57Z

filename_renameat2() replaces do_renameat2(); unlike the latter, it does not drop filename references - these days it can be just as easily arranged in the caller. Signed-off-by: Al Viro