On Tue, Mar 03, 2009 at 10:38:41PM -0600, Eric Sandeen wrote:
> I was seeing fsck errors on inode bitmaps after a 4 thread
> dbench run on a 4 cpu machine:
>
> Inode bitmap differences: -50736 -(50752--50753) etc...
>
> I believe that this is because ext4_free_inode() uses atomic
> bitops, and although ext4_new_inode() *used* to also use atomic
> bitops for synchronization, commit
> 393418676a7602e1d7d3f6e560159c65c8cbd50e changed this to use
> the sb_bgl_lock, so that we could also synchronize against
> read_inode_bitmap and initialization of uninit inode tables.
>
> However, that change left ext4_free_inode using atomic bitops,
> which I think leaves no synchronization between setting &
> unsetting bits in the inode table.
>
> The below patch fixes it for me, although I wonder if we're
> getting at all heavy-handed with this spinlock...
>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> ---
>
> Index: linux-2.6/fs/ext4/ialloc.c
> ===================================================================
> --- linux-2.6.orig/fs/ext4/ialloc.c
> +++ linux-2.6/fs/ext4/ialloc.c
> @@ -188,7 +188,7 @@ void ext4_free_inode(handle_t *handle, s
> struct ext4_group_desc *gdp;
> struct ext4_super_block *es;
> struct ext4_sb_info *sbi;
> - int fatal = 0, err, count;
> + int fatal = 0, err, count, cleared;
> ext4_group_t flex_group;
>
> if (atomic_read(&inode->i_count) > 1) {
> @@ -248,8 +248,10 @@ void ext4_free_inode(handle_t *handle, s
> goto error_return;
>
> /* Ok, now we can actually update the inode bitmaps.. */
> - if (!ext4_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
> - bit, bitmap_bh->b_data))
> + spin_lock(sb_bgl_lock(sbi, block_group));
> + cleared = ext4_clear_bit(bit, bitmap_bh->b_data);
> + spin_unlock(sb_bgl_lock(sbi, block_group));
> + if (!cleared)
> ext4_error(sb, "ext4_free_inode",
> "bit already cleared for inode %lu", ino);
> else {
>
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