On 10/04/2012 05:55 PM, Ben Hutchings wrote:
> On Tue, Oct 02, 2012 at 12:53:47AM +0200, Willy Tarreau wrote:
>> 2.6.32-longterm review patch. If anyone has any objections, please let me
>> know.
>>
>> ------------------
>>
>> From: Brian Foster <bfos...@redhat.com>
>>
>> commit 97795d2a5b8d3c8dc4365d4bd3404191840453ba upstream.
>>
>> If we hit a condition where we have allocated metadata blocks that
>> were not appropriately reserved, we risk underflow of
>> ei->i_reserved_meta_blocks. In turn, this can throw
>> sbi->s_dirtyclusters_counter significantly out of whack and undermine
>> the nondelalloc fallback logic in ext4_nonda_switch(). Warn if this
>> occurs and set i_allocated_meta_blocks to avoid this problem.
>>
>> This condition is reproduced by xfstests 270 against ext2 with
>> delalloc enabled:
>>
>> Mar 28 08:58:02 localhost kernel: [ 171.526344] EXT4-fs (loop1): delayed
>> block allocation failed for inode 14 at logical offset 64486 with max blocks
>> 64 with error -28
>> Mar 28 08:58:02 localhost kernel: [ 171.526346] EXT4-fs (loop1): This
>> should not happen!! Data will be lost
>>
>> 270 ultimately fails with an inconsistent filesystem and requires an
>> fsck to repair. The cause of the error is an underflow in
>> ext4_da_update_reserve_space() due to an unreserved meta block
>> allocation.
> [...]
>> + if (unlikely(ei->i_allocated_meta_blocks > ei->i_reserved_meta_blocks))
>> {
>> + ext4_msg(inode->i_sb, KERN_NOTICE, "%s: ino %lu, allocated %d "
>> + "with only %d reserved metadata blocks\n", __func__,
>> + inode->i_ino, ei->i_allocated_meta_blocks,
>> + ei->i_reserved_meta_blocks);
>> + WARN_ON(1);
>> + ei->i_allocated_meta_blocks = ei->i_reserved_meta_blocks;
>> + }
> [...]
>
> This seems to be working around a bug elsewhere. Has the underlying
> bug been fixed in mainline yet?
>
Yes, the bug was fixed in:
03179fe92318e7934c180d96f12eff2cb36ef7b6
ext4: undo ext4_calc_metadata_amount if we fail to claim space
Brian
> Ben.
>
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