kernel/linux.git/fs/exfat/file.c, branch linux-7.1.y

Merge tag 'exfat-for-7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/linkinjeon/exfat

2026-04-13T23:57:31+00:00

Pull exfat updates from Namjae Jeon: - Implement FALLOC_FL_ALLOCATE_RANGE to add support for preallocating clusters without zeroing, helping to reduce file fragmentation - Add a unified block readahead helper for FAT chain conversion, bitmap allocation, and directory entry lookups - Optimize exfat_chain_cont_cluster() by caching buffer heads to minimize mark_buffer_dirty() and mirroring overhead during NO_FAT_CHAIN to FAT_CHAIN conversion - Switch to truncate_inode_pages_final() in evict_inode() to prevent BUG_ON caused by shadow entries during reclaim - Fix a 32-bit truncation bug in directory entry calculations by ensuring proper bitwise coercion - Fix sb->s_maxbytes calculation to correctly reflect the maximum possible volume size for a given cluster size, resolving xfstests generic/213 - Introduced exfat_cluster_walk() helper to traverse FAT chains by a specified step, handling both ALLOC_NO_FAT_CHAIN and ALLOC_FAT_CHAIN modes - Introduced exfat_chain_advance() helper to advance an exfat_chain structure, updating both the current cluster and remaining size - Remove dead assignments and fix Smatch warnings * tag 'exfat-for-7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/linkinjeon/exfat: exfat: use exfat_chain_advance helper exfat: introduce exfat_chain_advance helper exfat: remove NULL cache pointer case in exfat_ent_get exfat: use exfat_cluster_walk helper exfat: introduce exfat_cluster_walk helper exfat: fix incorrect directory checksum after rename to shorter name exfat: fix s_maxbytes exfat: fix passing zero to ERR_PTR() in exfat_mkdir() exfat: fix error handling for FAT table operations exfat: optimize exfat_chain_cont_cluster with cached buffer heads exfat: drop redundant sec parameter from exfat_mirror_bh exfat: use readahead helper in exfat_get_dentry exfat: use readahead helper in exfat_allocate_bitmap exfat: add block readahead in exfat_chain_cont_cluster exfat: add fallocate FALLOC_FL_ALLOCATE_RANGE support exfat: Fix bitwise operation having different size exfat: Drop dead assignment of num_clusters exfat: use truncate_inode_pages_final() at evict_inode()

exfat: fix s_maxbytes

2026-03-31T14:01:07+00:00

With fallocate support, xfstest unit generic/213 fails with QA output created by 213 We should get: fallocate: No space left on device Strangely, xfs_io sometimes says "Success" when something went wrong -fallocate: No space left on device +fallocate: File too large because sb->s_maxbytes is set to the volume size. To be in line with other non-extent-based filesystems, set to max volume size possible with the cluster size of the volume. Signed-off-by: David Timber Signed-off-by: Namjae Jeon

fs: Rename generic_file_fsync() to simple_fsync()

2026-03-26T14:03:28+00:00

The implementation is now really basic so rename generic_file_fsync() simple_fsync() and __generic_file_fsync() to simple_fsync_noflush(). Signed-off-by: Jan Kara Link: https://patch.msgid.link/20260326095354.16340-56-jack@suse.cz Signed-off-by: Christian Brauner

exfat: add fallocate FALLOC_FL_ALLOCATE_RANGE support

2026-03-04T10:29:27+00:00

Currently, the Linux (ex)FAT drivers do not employ any cluster allocation strategy to keep fragmentation at bay. As a result, when multiple processes are competing for new clusters to expand files in exfat filesystem on Linux simultaneously, the files end up heavily fragmented. HDDs are most impacted, but this could also have some negative impact on various forms of flash memory depending on the type of underlying technology. For instance, modern digital cameras produce multiple media files for a single video stream. If the application does not take the fragmentation issue into account or the system is under memory pressure, the kernel end up allocating clusters in said files in a interleaved manner. Demo script: for (( i = 0; i < 4; i += 1 )); do dd if=/dev/urandom iflag=fullblock bs=1M count=64 of=frag-$i & done for (( i = 0; i < 4; i += 1 )); do wait done filefrag frag-* Result - Linux kernel native exfat, async mount: 780 extents found 740 extents found 809 extents found 712 extents found Result - Linux kernel native exfat, sync mount: 1852 extents found 1836 extents found 1846 extents found 1881 extents found Result - Windows XP: 3 extents found 3 extents found 3 extents found 2 extents found Windows kernel, on the other hand, regardless of the underlying storage interface or the medium, seems to space out clusters for each file. Similar strategy has to be employed by Linux fat filesystems for efficient utilisation of storage backend. In the meantime, userspace applications like rsync may use fallocate to combat this issue. This patch may introduce a regression-like behaviour to some niche filesystem-agnostic applications that use fallocate and proceed to non-sequentially write to the file. Examples: - libtorrent's use of posix_fallocate() and the first fragment from a peer is near the end of the file - "Download accelerators" that do partial content requests(HTTP 206) in multiple threads writing to the same file The delay incurred in such use cases is documented in WinAPI. Patches that add the ioctl equivalents to the WinAPI function SetFileValidData() and `fsutil file queryvaliddata ...` will follow. Signed-off-by: David Timber Signed-off-by: Namjae Jeon

exfat: add blank line after declarations

2026-02-12T12:21:51+00:00

Add a blank line after variable declarations in fatent.c and file.c. This improves readability and makes code style more consistent across the exfat subsystem. Signed-off-by: William Hansen-Baird Signed-off-by: Namjae Jeon

exfat: reduce unnecessary writes during mmap write

2026-02-12T12:21:47+00:00

During mmap write, exfat_page_mkwrite() currently extends valid_size to the end of the VMA range. For a large mapping, this can push valid_size far beyond the page that actually triggered the fault, resulting in unnecessary writes. valid_size only needs to extend to the end of the page being written. Signed-off-by: Yuling Dong Reviewed-by: Yuezhang Mo Signed-off-by: Namjae Jeon

exfat: add setlease file operation

2026-01-12T09:55:46+00:00

Add the setlease file_operation to exfat_file_operations and exfat_dir_operations, pointing to generic_setlease. A future patch will change the default behavior to reject lease attempts with -EINVAL when there is no setlease file operation defined. Add generic_setlease to retain the ability to set leases on this filesystem. Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20260108-setlease-6-20-v1-7-ea4dec9b67fa@kernel.org Acked-by: Namjae Jeon Acked-by: Al Viro Acked-by: Christoph Hellwig Signed-off-by: Christian Brauner

exfat: zero out post-EOF page cache on file extension

2025-12-03T01:00:16+00:00

xfstests generic/363 was failing due to unzeroed post-EOF page cache that allowed mmap writes beyond EOF to become visible after file extension. For example, in following xfs_io sequence, 0x22 should not be written to the file but would become visible after the extension: xfs_io -f -t -c "pwrite -S 0x11 0 8" \ -c "mmap 0 4096" \ -c "mwrite -S 0x22 32 32" \ -c "munmap" \ -c "pwrite -S 0x33 512 32" \ $testfile This violates the expected behavior where writes beyond EOF via mmap should not persist after the file is extended. Instead, the extended region should contain zeros. Fix this by using truncate_pagecache() to truncate the page cache after the current EOF when extending the file. Signed-off-by: Yuezhang Mo Signed-off-by: Namjae Jeon

exfat: fix out-of-bounds in exfat_nls_to_ucs2()

2025-10-15T08:53:20+00:00

Since the len argument value passed to exfat_ioctl_set_volume_label() from exfat_nls_to_utf16() is passed 1 too large, an out-of-bounds read occurs when dereferencing p_cstring in exfat_nls_to_ucs2() later. And because of the NLS_NAME_OVERLEN macro, another error occurs when creating a file with a period at the end using utf8 and other iocharsets. So to avoid this, you should remove the code that uses NLS_NAME_OVERLEN macro and make the len argument value be the length of the label string, but with a maximum length of FSLABEL_MAX - 1. Reported-by: syzbot+98cc76a76de46b3714d4@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=98cc76a76de46b3714d4 Fixes: d01579d590f7 ("exfat: Add support for FS_IOC_{GET,SET}FSLABEL") Suggested-by: Pali Rohár Signed-off-by: Jeongjun Park Signed-off-by: Namjae Jeon

exfat: Add support for FS_IOC_{GET,SET}FSLABEL

2025-09-30T04:49:31+00:00

Add support for reading / writing to the exfat volume label from the FS_IOC_GETFSLABEL and FS_IOC_SETFSLABEL ioctls Co-developed-by: Yuezhang Mo Signed-off-by: Yuezhang Mo Signed-off-by: Ethan Ferguson Reviewed-by: Sungjong Seo Signed-off-by: Namjae Jeon