5.15-stable review patch. If anyone has any objections, please let me know.
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From: Ojaswin Mujoo ojaswin@linux.ibm.com
commit 46c22a8bb4cb03211da1100d7ee4a2005bf77c70 upstream.
Currently, our handling of metadata is _ambiguous_ in some scenarios, that is, we end up returning unknown if the range only covers the mapping partially.
For example, in the following case:
$ xfs_io -c fsmap -d
0: 254:16 [0..7]: static fs metadata 8 1: 254:16 [8..15]: special 102:1 8 2: 254:16 [16..5127]: special 102:2 5112 3: 254:16 [5128..5255]: special 102:3 128 4: 254:16 [5256..5383]: special 102:4 128 5: 254:16 [5384..70919]: inodes 65536 6: 254:16 [70920..70967]: unknown 48 ...
$ xfs_io -c fsmap -d 24 33
0: 254:16 [24..39]: unknown 16 <--- incomplete reporting
$ xfs_io -c fsmap -d 24 33 (With patch)
0: 254:16 [16..5127]: special 102:2 5112
This is because earlier in ext4_getfsmap_meta_helper, we end up ignoring any extent that starts before our queried range, but overlaps it. While the man page [1] is a bit ambiguous on this, this fix makes the output make more sense since we are anyways returning an "unknown" extent. This is also consistent to how XFS does it:
$ xfs_io -c fsmap -d
... 6: 254:16 [104..127]: free space 24 7: 254:16 [128..191]: inodes 64 ...
$ xfs_io -c fsmap -d 137 150
0: 254:16 [128..191]: inodes 64 <-- full extent returned
[1] https://man7.org/linux/man-pages/man2/ioctl_getfsmap.2.html
Reported-by: Ritesh Harjani (IBM) ritesh.list@gmail.com Cc: stable@kernel.org Signed-off-by: Ojaswin Mujoo ojaswin@linux.ibm.com Message-ID: 023f37e35ee280cd9baac0296cbadcbe10995cab.1757058211.git.ojaswin@linux.ibm.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ext4/fsmap.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
--- a/fs/ext4/fsmap.c +++ b/fs/ext4/fsmap.c @@ -74,7 +74,8 @@ static int ext4_getfsmap_dev_compare(con static bool ext4_getfsmap_rec_before_low_key(struct ext4_getfsmap_info *info, struct ext4_fsmap *rec) { - return rec->fmr_physical < info->gfi_low.fmr_physical; + return rec->fmr_physical + rec->fmr_length <= + info->gfi_low.fmr_physical; }
/* @@ -200,15 +201,18 @@ static int ext4_getfsmap_meta_helper(str ext4_group_first_block_no(sb, agno)); fs_end = fs_start + EXT4_C2B(sbi, len);
- /* Return relevant extents from the meta_list */ + /* + * Return relevant extents from the meta_list. We emit all extents that + * partially/fully overlap with the query range + */ list_for_each_entry_safe(p, tmp, &info->gfi_meta_list, fmr_list) { - if (p->fmr_physical < info->gfi_next_fsblk) { + if (p->fmr_physical + p->fmr_length <= info->gfi_next_fsblk) { list_del(&p->fmr_list); kfree(p); continue; } - if (p->fmr_physical <= fs_start || - p->fmr_physical + p->fmr_length <= fs_end) { + if (p->fmr_physical <= fs_end && + p->fmr_physical + p->fmr_length > fs_start) { /* Emit the retained free extent record if present */ if (info->gfi_lastfree.fmr_owner) { error = ext4_getfsmap_helper(sb, info,