5.4-stable review patch. If anyone has any objections, please let me know.
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From: Ojaswin Mujoo ojaswin@linux.ibm.com
commit bae76c035bf0852844151e68098c9b7cd63ef238 upstream.
With bigalloc enabled, the logic to report last extent has a bug since we try to use cluster units instead of block units. This can cause an issue where extra incorrect entries might be returned back to the user. This was flagged by generic/365 with 64k bs and -O bigalloc.
** Details of issue **
The issue was noticed on 5G 64k blocksize FS with -O bigalloc which has only 1 bg.
$ xfs_io -c "fsmap -d" /mnt/scratch
0: 253:48 [0..127]: static fs metadata 128 /* sb */ 1: 253:48 [128..255]: special 102:1 128 /* gdt */ 3: 253:48 [256..383]: special 102:3 128 /* block bitmap */ 4: 253:48 [384..2303]: unknown 1920 /* flex bg empty space */ 5: 253:48 [2304..2431]: special 102:4 128 /* inode bitmap */ 6: 253:48 [2432..4351]: unknown 1920 /* flex bg empty space */ 7: 253:48 [4352..6911]: inodes 2560 8: 253:48 [6912..538623]: unknown 531712 9: 253:48 [538624..10485759]: free space 9947136
The issue can be seen with:
$ xfs_io -c "fsmap -d 0 3" /mnt/scratch
0: 253:48 [0..127]: static fs metadata 128 1: 253:48 [384..2047]: unknown 1664
Only the first entry was expected to be returned but we get 2. This is because:
ext4_getfsmap_datadev() first_cluster, last_cluster = 0 ... info->gfi_last = true; ext4_getfsmap_datadev_helper(sb, end_ag, last_cluster + 1, 0, info); fsb = C2B(1) = 16 fslen = 0 ... /* Merge in any relevant extents from the meta_list */ list_for_each_entry_safe(p, tmp, &info->gfi_meta_list, fmr_list) { ... // since fsb = 16, considers all metadata which starts before 16 blockno iter 1: error = ext4_getfsmap_helper(sb, info, p); // p = sb (0,1), nop info->gfi_next_fsblk = 1 iter 2: error = ext4_getfsmap_helper(sb, info, p); // p = gdt (1,2), nop info->gfi_next_fsblk = 2 iter 3: error = ext4_getfsmap_helper(sb, info, p); // p = blk bitmap (2,3), nop info->gfi_next_fsblk = 3 iter 4: error = ext4_getfsmap_helper(sb, info, p); // p = ino bitmap (18,19) if (rec_blk > info->gfi_next_fsblk) { // (18 > 3) // emits an extra entry ** BUG ** } }
Fix this by directly calling ext4_getfsmap_datadev() with a dummy record that has fmr_physical set to (end_fsb + 1) instead of last_cluster + 1. By using the block instead of cluster we get the correct behavior.
Replacing ext4_getfsmap_datadev_helper() with ext4_getfsmap_helper() is okay since the gfi_lastfree and metadata checks in ext4_getfsmap_datadev_helper() are anyways redundant when we only want to emit the last allocated block of the range, as we have already taken care of emitting metadata and any last free blocks.
Cc: stable@kernel.org Reported-by: Disha Goel disgoel@linux.ibm.com Fixes: 4a622e4d477b ("ext4: fix FS_IOC_GETFSMAP handling") Signed-off-by: Ojaswin Mujoo ojaswin@linux.ibm.com Reviewed-by: Darrick J. Wong djwong@kernel.org Link: https://patch.msgid.link/e7472c8535c9c5ec10f425f495366864ea12c9da.1754377641... Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ext4/fsmap.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
--- a/fs/ext4/fsmap.c +++ b/fs/ext4/fsmap.c @@ -526,6 +526,7 @@ static int ext4_getfsmap_datadev(struct ext4_group_t end_ag; ext4_grpblk_t first_cluster; ext4_grpblk_t last_cluster; + struct ext4_fsmap irec; int error = 0;
bofs = le32_to_cpu(sbi->s_es->s_first_data_block); @@ -609,10 +610,18 @@ static int ext4_getfsmap_datadev(struct goto err; }
- /* Report any gaps at the end of the bg */ + /* + * The dummy record below will cause ext4_getfsmap_helper() to report + * any allocated blocks at the end of the range. + */ + irec.fmr_device = 0; + irec.fmr_physical = end_fsb + 1; + irec.fmr_length = 0; + irec.fmr_owner = EXT4_FMR_OWN_FREE; + irec.fmr_flags = 0; + info->gfi_last = true; - error = ext4_getfsmap_datadev_helper(sb, end_ag, last_cluster + 1, - 0, info); + error = ext4_getfsmap_helper(sb, info, &irec); if (error) goto err;