diff options
| author | Zhang Yi <yi.zhang@huawei.com> | 2025-04-23 16:52:52 +0800 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2025-05-14 10:42:12 -0400 |
| commit | 151ff9325e5e17c97839a00b740726656b04647b (patch) | |
| tree | 99a1e8872870295a56bef15de744f55f9b4c1414 | |
| parent | 402e38e6b71f5739119ca3107f375e112d63c7c5 (diff) | |
ext4: prevent stale extent cache entries caused by concurrent fiemap
The ext4_fiemap() currently invokes ext4_ext_precache() and
iomap_fiemap() to preload the extent cache and query mapping information
without holding the inode's i_rwsem. This can result in stale extent
cache entries when competing with operations such as
ext4_collapse_range() which calls ext4_ext_remove_space() or
ext4_ext_shift_extents().
The problem arises when ext4_ext_remove_space() temporarily releases
i_data_sem due to insufficient journal credits. During this interval, a
concurrent ext4_fiemap() may cache extent entries that are about to be
deleted. As a result, these cached entries become stale and inconsistent
with the actual extents.
Loading the extents cache without holding the inode's i_rwsem or the
mapping's invalidate_lock is not permitted besides during the writeback.
Fix this by holding the i_rwsem in ext4_fiemap().
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20250423085257.122685-5-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
| -rw-r--r-- | fs/ext4/extents.c | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 8a5724b2dc517..3adf05fbdd591 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4963,10 +4963,11 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, { int error = 0; + inode_lock_shared(inode); if (fieinfo->fi_flags & FIEMAP_FLAG_CACHE) { error = ext4_ext_precache(inode); if (error) - return error; + goto unlock; fieinfo->fi_flags &= ~FIEMAP_FLAG_CACHE; } @@ -4977,15 +4978,19 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, */ error = ext4_fiemap_check_ranges(inode, start, &len); if (error) - return error; + goto unlock; if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR) { fieinfo->fi_flags &= ~FIEMAP_FLAG_XATTR; - return iomap_fiemap(inode, fieinfo, start, len, - &ext4_iomap_xattr_ops); + error = iomap_fiemap(inode, fieinfo, start, len, + &ext4_iomap_xattr_ops); + } else { + error = iomap_fiemap(inode, fieinfo, start, len, + &ext4_iomap_report_ops); } - - return iomap_fiemap(inode, fieinfo, start, len, &ext4_iomap_report_ops); +unlock: + inode_unlock_shared(inode); + return error; } int ext4_get_es_cache(struct inode *inode, struct fiemap_extent_info *fieinfo, |