After updating bb_free in mb_free_blocks, it is possible to return without updating bb_fragments because the block being freed is found to have already been freed, which leads to inconsistency between bb_free and bb_fragments.
Since the group may be unlocked in ext4_grp_locked_error(), this can lead to problems such as dividing by zero when calculating the average fragment length. Hence move the update of bb_free to after the block double-free check guarantees that the corresponding statistics are updated only after the core block bitmap is modified.
Fixes: eabe0444df90 ("ext4: speed-up releasing blocks on commit") CC: stable@vger.kernel.org # 3.10 Signed-off-by: Baokun Li libaokun1@huawei.com --- fs/ext4/mballoc.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index f6131ba514c8..1f15774971d7 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -1910,11 +1910,6 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b, mb_check_buddy(e4b); mb_free_blocks_double(inode, e4b, first, count);
- this_cpu_inc(discard_pa_seq); - e4b->bd_info->bb_free += count; - if (first < e4b->bd_info->bb_first_free) - e4b->bd_info->bb_first_free = first; - /* access memory sequentially: check left neighbour, * clear range and then check right neighbour */ @@ -1941,10 +1936,16 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b, EXT4_GROUP_INFO_BBITMAP_CORRUPT); } else { mb_regenerate_buddy(e4b); + goto check; } - goto done; + return; }
+ this_cpu_inc(discard_pa_seq); + e4b->bd_info->bb_free += count; + if (first < e4b->bd_info->bb_first_free) + e4b->bd_info->bb_first_free = first; + /* let's maintain fragments counter */ if (left_is_free && right_is_free) e4b->bd_info->bb_fragments--; @@ -1969,9 +1970,9 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b, if (first <= last) mb_buddy_mark_free(e4b, first >> 1, last >> 1);
-done: mb_set_largest_free_order(sb, e4b->bd_info); mb_update_avg_fragment_size(sb, e4b->bd_info); +check: mb_check_buddy(e4b); }
On Thu 21-12-23 23:05:54, Baokun Li wrote:
After updating bb_free in mb_free_blocks, it is possible to return without updating bb_fragments because the block being freed is found to have already been freed, which leads to inconsistency between bb_free and bb_fragments.
Since the group may be unlocked in ext4_grp_locked_error(), this can lead to problems such as dividing by zero when calculating the average fragment length. Hence move the update of bb_free to after the block double-free check guarantees that the corresponding statistics are updated only after the core block bitmap is modified.
Fixes: eabe0444df90 ("ext4: speed-up releasing blocks on commit") CC: stable@vger.kernel.org # 3.10 Signed-off-by: Baokun Li libaokun1@huawei.com
Just one nit below but regardless of that feel free to add:
Reviewed-by: Jan Kara jack@suse.cz
@@ -1941,10 +1936,16 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b, EXT4_GROUP_INFO_BBITMAP_CORRUPT); } else { mb_regenerate_buddy(e4b);
goto check;
goto done;
return;
I think this might be more readable when we revert the condition like:
/* * Fastcommit replay can free already freed blocks which * corrupts allocation info. Regenerate it. */ if (sbi->s_mount_state & EXT4_FC_REPLAY) { mb_regenerate_buddy(e4b); goto check; } ext4_grp_locked_error(sb, e4b->bd_group, inode ? inode->i_ino : 0, blocknr, "freeing already freed block (bit %u); block bitmap corrupt.", block); ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group, EXT4_GROUP_INFO_BBITMAP_CORRUPT); return; }
Honza
On 2024/1/4 18:42, Jan Kara wrote:
On Thu 21-12-23 23:05:54, Baokun Li wrote:
After updating bb_free in mb_free_blocks, it is possible to return without updating bb_fragments because the block being freed is found to have already been freed, which leads to inconsistency between bb_free and bb_fragments.
Since the group may be unlocked in ext4_grp_locked_error(), this can lead to problems such as dividing by zero when calculating the average fragment length. Hence move the update of bb_free to after the block double-free check guarantees that the corresponding statistics are updated only after the core block bitmap is modified.
Fixes: eabe0444df90 ("ext4: speed-up releasing blocks on commit") CC: stable@vger.kernel.org # 3.10 Signed-off-by: Baokun Li libaokun1@huawei.com
Just one nit below but regardless of that feel free to add:
Reviewed-by: Jan Kara jack@suse.cz
@@ -1941,10 +1936,16 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b, EXT4_GROUP_INFO_BBITMAP_CORRUPT); } else { mb_regenerate_buddy(e4b);
goto check;
goto done;
return;I think this might be more readable when we revert the condition like:
/* * Fastcommit replay can free already freed blocks which * corrupts allocation info. Regenerate it. */ if (sbi->s_mount_state & EXT4_FC_REPLAY) { mb_regenerate_buddy(e4b); goto check; } ext4_grp_locked_error(sb, e4b->bd_group, inode ? inode->i_ino : 0, blocknr, "freeing already freed block (bit %u); block bitmap corrupt.", block); ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group, EXT4_GROUP_INFO_BBITMAP_CORRUPT); return;}
Honza
Yes, it looks much clearer that way! I will switch to it in the next version.
Thanks a lot!
linux-stable-mirror@lists.linaro.org
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Baokun Li -
Jan Kara