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linux/fs/f2fs
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wangzijie 0a6b2ed51a f2fs: fix zero-sized extent for precache extents 
[ Upstream commit 8175c86439 ]

Script to reproduce:
f2fs_io write 1 0 1881 rand dsync testfile
f2fs_io fallocate 0 7708672 4096 testfile
f2fs_io write 1 1881 1 rand buffered testfile
fsync testfile
umount
mount
f2fs_io precache_extents testfile

When the data layout is something like this:
dnode1:                     dnode2:
[0]      A                  [0]    NEW_ADDR
[1]      A+1                [1]    0x0
...
[1016]   A+1016
[1017]   B (B!=A+1017)      [1017] 0x0

During precache_extents, we map the last block(valid blkaddr) in dnode1:
map->m_flags |= F2FS_MAP_MAPPED;
map->m_pblk = blkaddr(valid blkaddr);
map->m_len = 1;
then we goto next_dnode, meet the first block in dnode2(hole), goto sync_out:
map->m_flags & F2FS_MAP_MAPPED == true, and we make zero-sized extent:

map->m_len = 1
ofs = start_pgofs - map->m_lblk = 1882 - 1881 = 1
ei.fofs = start_pgofs = 1882
ei.len = map->m_len - ofs = 1 - 1 = 0

Rebased on patch[1], this patch can cover these cases to avoid zero-sized extent:
A,B,C is valid blkaddr
case1:
dnode1:                     dnode2:
[0]      A                  [0]    NEW_ADDR
[1]      A+1                [1]    0x0
...                         ....
[1016]   A+1016
[1017]   B (B!=A+1017)      [1017] 0x0

case2:
dnode1:                     dnode2:
[0]      A                  [0]    C (C!=B+1)
[1]      A+1                [1]    C+1
...                         ....
[1016]   A+1016
[1017]   B (B!=A+1017)      [1017] 0x0

case3:
dnode1:                     dnode2:
[0]      A                  [0]    C (C!=B+2)
[1]      A+1                [1]    C+1
...                         ....
[1015]   A+1015
[1016]   B (B!=A+1016)
[1017]   B+1                [1017] 0x0

[1] https://lore.kernel.org/linux-f2fs-devel/20250912081250.44383-1-chao@kernel.org/

Fixes: c4020b2da4 ("f2fs: support F2FS_IOC_PRECACHE_EXTENTS")
Signed-off-by: wangzijie <wangzijie1@honor.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-10-15 11:56:34 +02:00
..
acl.c f2fs: port to vfs{g,u}id_t and associated helpers 2022-10-04 13:31:43 -07:00
acl.h vfs: add rcu argument to ->get_acl() callback 2021-08-18 22:08:24 +02:00
checkpoint.c f2fs: fix to update user block counts in block_operations() 2024-08-03 08:49:48 +02:00
compress.c f2fs: fix typos in comments 2024-06-12 11:03:37 +02:00
data.c f2fs: fix zero-sized extent for precache extents 2025-10-15 11:56:34 +02:00
debug.c f2fs: refactor extent_cache to support for read and more 2023-05-17 11:53:52 +02:00
dir.c f2fs: Introduce linear search for dentries 2025-02-21 13:49:25 +01:00
extent_cache.c f2fs: fix KMSAN uninit-value in extent_info usage 2025-08-15 12:05:06 +02:00
f2fs.h f2fs: fix to call clear_page_private_reference in .{release,invalid}_folio 2025-08-28 16:26:15 +02:00
file.c f2fs: fix to wait dio completion 2025-02-21 13:50:12 +01:00
gc.c f2fs: fix to avoid use GC_AT when setting gc_mode as GC_URGENT_LOW or GC_URGENT_MID 2024-12-14 19:53:45 +01:00
gc.h f2fs: Fix system crash due to lack of free space in LFS 2023-05-24 17:32:38 +01:00
hash.c f2fs: don't use casefolded comparison for "." and ".." 2022-05-17 11:19:23 -07:00
inline.c f2fs: Introduce linear search for dentries 2025-02-21 13:49:25 +01:00
inode.c f2fs: fix to do sanity check on ino and xnid 2025-08-28 16:26:09 +02:00
iostat.c f2fs: fix to avoid potential memory corruption in __update_iostat_latency() 2023-03-11 13:55:21 +01:00
iostat.h f2fs: iostat: support accounting compressed IO 2022-08-29 21:15:51 -07:00
Kconfig f2fs: introduce F2FS_UNFAIR_RWSEM to support unfair rwsem 2022-03-04 09:15:53 -08:00
Makefile f2fs: separate out iostat feature 2021-08-23 10:25:51 -07:00
namei.c f2fs: prevent kernel warning due to negative i_nlink from corrupted image 2025-06-27 11:07:29 +01:00
node.c f2fs: fix to avoid out-of-boundary access in dnode page 2025-08-28 16:26:15 +02:00
node.h f2fs: convert to use bitmap API 2024-01-10 17:10:30 +01:00
recovery.c f2fs: fix to avoid potential panic during recovery 2024-03-26 18:20:55 -04:00
segment.c f2fs: check curseg->inited before write_sum_page in change_curseg 2024-12-14 19:53:45 +01:00
segment.h f2fs: fix to calculate dirty data during has_not_enough_free_secs() 2025-08-15 12:05:07 +02:00
shrinker.c f2fs: refactor extent_cache to support for read and more 2023-05-17 11:53:52 +02:00
super.c f2fs: don't over-report free space or inodes in statvfs 2025-07-06 10:57:57 +02:00
sysfs.c f2fs: check validation of fault attrs in f2fs_build_fault_attr() 2024-07-11 12:47:09 +02:00
verity.c fs: f2fs: initialize fsdata in pagecache_write() 2023-03-11 13:55:18 +01:00
xattr.c f2fs: reduce expensive checkpoint trigger frequency 2024-10-17 15:21:09 +02:00
xattr.h f2fs: code cleanup by removing ifdef macro surrounding 2020-05-26 18:56:10 -07:00