ext4: avoid allocate block from corrupted group in ext4_mb_find_by_goal()

There's issue as follows:
...
EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 2243 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 2239 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): error count since last fsck: 1
EXT4-fs (mmcblk0p1): initial error at time 1765597433: ext4_mb_generate_buddy:760
EXT4-fs (mmcblk0p1): last error at time 1765597433: ext4_mb_generate_buddy:760
...

According to the log analysis, blocks are always requested from the
corrupted block group. This may happen as follows:
ext4_mb_find_by_goal
  ext4_mb_load_buddy
   ext4_mb_load_buddy_gfp
     ext4_mb_init_cache
      ext4_read_block_bitmap_nowait
      ext4_wait_block_bitmap
       ext4_validate_block_bitmap
        if (!grp || EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
         return -EFSCORRUPTED; // There's no logs.
 if (err)
  return err;  // Will return error
ext4_lock_group(ac->ac_sb, group);
  if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info))) // Unreachable
   goto out;

After commit 9008a58e5dce ("ext4: make the bitmap read routines return
real error codes") merged, Commit 163a203ddb36 ("ext4: mark block group
as corrupt on block bitmap error") is no real solution for allocating
blocks from corrupted block groups. This is because if
'EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info)' is true, then
'ext4_mb_load_buddy()' may return an error. This means that the block
allocation will fail.
Therefore, check block group if corrupted when ext4_mb_load_buddy()
returns error.

Fixes: 163a203ddb36 ("ext4: mark block group as corrupt on block bitmap error")
Fixes: 9008a58e5dce ("ext4: make the bitmap read routines return real error codes")
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260302134619.3145520-1-yebin@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 20e9fdaf4301b61c9d54401ed95067db6b6b8173..705a879f13d3387af7281755764c174d672d08af 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2443,8 +2443,12 @@ int ext4_mb_find_by_goal(struct ext4_allocation_context *ac,
                return 0;
 
        err = ext4_mb_load_buddy(ac->ac_sb, group, e4b);
-       if (err)
+       if (err) {
+               if (EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info) &&
+                   !(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
+                       return 0;
                return err;
+       }
 
        ext4_lock_group(ac->ac_sb, group);
        if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info)))