kernel/linux.git/fs/file.c, branch v7.0-rc7

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

fs/file: optimize close_range() complexity from O(N) to O(Sparse)

2026-01-23T10:31:49+00:00

In close_range(), the kernel traditionally performs a linear scan over the [fd, max_fd] range, resulting in O(N) complexity where N is the range size. For processes with sparse FD tables, this is inefficient as it checks many unallocated slots. This patch optimizes __range_close() by using find_next_bit() on the open_fds bitmap to skip holes. This shifts the algorithmic complexity from O(Range Size) to O(Active FDs), providing a significant performance boost for large-range close operations on sparse file descriptor tables. Signed-off-by: Qiliang Yuan Signed-off-by: Qiliang Yuan Link: https://patch.msgid.link/20260123081221.659125-1-realwujing@gmail.com Signed-off-by: Christian Brauner

Merge tag 'vfs-6.19-rc1.fd_prepare.fs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-12-02T01:32:07+00:00

Pull fd prepare updates from Christian Brauner: "This adds the FD_ADD() and FD_PREPARE() primitive. They simplify the common pattern of get_unused_fd_flags() + create file + fd_install() that is used extensively throughout the kernel and currently requires cumbersome cleanup paths. FD_ADD() - For simple cases where a file is installed immediately: fd = FD_ADD(O_CLOEXEC, vfio_device_open_file(device)); if (fd < 0) vfio_device_put_registration(device); return fd; FD_PREPARE() - For cases requiring access to the fd or file, or additional work before publishing: FD_PREPARE(fdf, O_CLOEXEC, sync_file->file); if (fdf.err) { fput(sync_file->file); return fdf.err; } data.fence = fd_prepare_fd(fdf); if (copy_to_user((void __user *)arg, &data, sizeof(data))) return -EFAULT; return fd_publish(fdf); The primitives are centered around struct fd_prepare. FD_PREPARE() encapsulates all allocation and cleanup logic and must be followed by a call to fd_publish() which associates the fd with the file and installs it into the caller's fdtable. If fd_publish() isn't called, both are deallocated automatically. FD_ADD() is a shorthand that does fd_publish() immediately and never exposes the struct to the caller. I've implemented this in a way that it's compatible with the cleanup infrastructure while also being usable separately. IOW, it's centered around struct fd_prepare which is aliased to class_fd_prepare_t and so we can make use of all the basica guard infrastructure" * tag 'vfs-6.19-rc1.fd_prepare.fs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (42 commits) io_uring: convert io_create_mock_file() to FD_PREPARE() file: convert replace_fd() to FD_PREPARE() vfio: convert vfio_group_ioctl_get_device_fd() to FD_ADD() tty: convert ptm_open_peer() to FD_ADD() ntsync: convert ntsync_obj_get_fd() to FD_PREPARE() media: convert media_request_alloc() to FD_PREPARE() hv: convert mshv_ioctl_create_partition() to FD_ADD() gpio: convert linehandle_create() to FD_PREPARE() pseries: port papr_rtas_setup_file_interface() to FD_ADD() pseries: convert papr_platform_dump_create_handle() to FD_ADD() spufs: convert spufs_gang_open() to FD_PREPARE() papr-hvpipe: convert papr_hvpipe_dev_create_handle() to FD_PREPARE() spufs: convert spufs_context_open() to FD_PREPARE() net/socket: convert __sys_accept4_file() to FD_ADD() net/socket: convert sock_map_fd() to FD_ADD() net/kcm: convert kcm_ioctl() to FD_PREPARE() net/handshake: convert handshake_nl_accept_doit() to FD_PREPARE() secretmem: convert memfd_secret() to FD_ADD() memfd: convert memfd_create() to FD_ADD() bpf: convert bpf_token_create() to FD_PREPARE() ...

file: convert replace_fd() to FD_PREPARE()

2025-11-28T11:42:36+00:00

Link: https://patch.msgid.link/20251123-work-fd-prepare-v4-44-b6efa1706cfd@kernel.org Signed-off-by: Christian Brauner

fs: move fd_install() slowpath into a dedicated routine and provide commentary

2025-11-12T11:19:09+00:00

On stock kernel gcc 14 emits avoidable register spillage: endbr64 call ffffffff81374630 <__fentry__> push %r13 push %r12 push %rbx sub $0x8,%rsp [snip] Total fast path is 99 bytes. Moving the slowpath out avoids it and shortens the fast path to 74 bytes. Signed-off-by: Mateusz Guzik Link: https://patch.msgid.link/20251110095634.1433061-1-mjguzik@gmail.com Signed-off-by: Christian Brauner

fs: always return zero on success from replace_fd()

2025-08-11T12:52:25+00:00

replace_fd() returns the number of the new file descriptor through the return value of do_dup2(). However its callers never care about the specific returned number. In fact the caller in receive_fd_replace() treats any non-zero return value as an error and therefore never calls __receive_sock() for most file descriptors, which is a bug. To fix the bug in receive_fd_replace() and to avoid the same issue happening in future callers, signal success through a plain zero. Suggested-by: Al Viro Link: https://lore.kernel.org/lkml/20250801220215.GS222315@ZenIV/ Fixes: 173817151b15 ("fs: Expand __receive_fd() to accept existing fd") Fixes: 42eb0d54c08a ("fs: split receive_fd_replace from __receive_fd") Cc: stable@vger.kernel.org Signed-off-by: Thomas Weißschuh Link: https://lore.kernel.org/20250805-fix-receive_fd_replace-v3-1-b72ba8b34bac@linutronix.de Signed-off-by: Christian Brauner

Merge tag 'vfs-6.17-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-07-28T18:22:56+00:00

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 ...

fs: Prevent file descriptor table allocations exceeding INT_MAX

2025-07-08T14:48:12+00:00

When sysctl_nr_open is set to a very high value (for example, 1073741816 as set by systemd), processes attempting to use file descriptors near the limit can trigger massive memory allocation attempts that exceed INT_MAX, resulting in a WARNING in mm/slub.c: WARNING: CPU: 0 PID: 44 at mm/slub.c:5027 __kvmalloc_node_noprof+0x21a/0x288 This happens because kvmalloc_array() and kvmalloc() check if the requested size exceeds INT_MAX and emit a warning when the allocation is not flagged with __GFP_NOWARN. Specifically, when nr_open is set to 1073741816 (0x3ffffff8) and a process calls dup2(oldfd, 1073741880), the kernel attempts to allocate: - File descriptor array: 1073741880 * 8 bytes = 8,589,935,040 bytes - Multiple bitmaps: ~400MB - Total allocation size: > 8GB (exceeding INT_MAX = 2,147,483,647) Reproducer: 1. Set /proc/sys/fs/nr_open to 1073741816: # echo 1073741816 > /proc/sys/fs/nr_open 2. Run a program that uses a high file descriptor: #include #include int main() { struct rlimit rlim = {1073741824, 1073741824}; setrlimit(RLIMIT_NOFILE, &rlim); dup2(2, 1073741880); // Triggers the warning return 0; } 3. Observe WARNING in dmesg at mm/slub.c:5027 systemd commit a8b627a introduced automatic bumping of fs.nr_open to the maximum possible value. The rationale was that systems with memory control groups (memcg) no longer need separate file descriptor limits since memory is properly accounted. However, this change overlooked that: 1. The kernel's allocation functions still enforce INT_MAX as a maximum size regardless of memcg accounting 2. Programs and tests that legitimately test file descriptor limits can inadvertently trigger massive allocations 3. The resulting allocations (>8GB) are impractical and will always fail systemd's algorithm starts with INT_MAX and keeps halving the value until the kernel accepts it. On most systems, this results in nr_open being set to 1073741816 (0x3ffffff8), which is just under 1GB of file descriptors. While processes rarely use file descriptors near this limit in normal operation, certain selftests (like tools/testing/selftests/core/unshare_test.c) and programs that test file descriptor limits can trigger this issue. Fix this by adding a check in alloc_fdtable() to ensure the requested allocation size does not exceed INT_MAX. This causes the operation to fail with -EMFILE instead of triggering a kernel warning and avoids the impractical >8GB memory allocation request. Fixes: 9cfe015aa424 ("get rid of NR_OPEN and introduce a sysctl_nr_open") Cc: stable@vger.kernel.org Signed-off-by: Sasha Levin Link: https://lore.kernel.org/20250629074021.1038845-1-sashal@kernel.org Signed-off-by: Christian Brauner

fs: drop assert in file_seek_cur_needs_f_lock

2025-06-16T07:59:24+00:00

The assert in function file_seek_cur_needs_f_lock() can be triggered very easily because there are many users of vfs_llseek() (such as overlayfs) that do their custom locking around llseek instead of relying on fdget_pos(). Just drop the overzealous assertion. Fixes: da06e3c51794 ("fs: don't needlessly acquire f_lock") Suggested-by: Jan Kara Suggested-by: Mateusz Guzik Signed-off-by: Luis Henriques Link: https://lore.kernel.org/20250613101111.17716-1-luis@igalia.com Signed-off-by: Christian Brauner

fs: fall back to file_ref_put() for non-last reference

2025-04-22T16:16:09+00:00

This reduces the slowdown in face of multiple callers issuing close on what turns out to not be the last reference. Signed-off-by: Mateusz Guzik Link: https://lore.kernel.org/20250418125756.59677-1-mjguzik@gmail.com Reviewed-by: Jan Kara Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202504171513.6d6f8a16-lkp@intel.com Signed-off-by: Christian Brauner