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>
---
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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