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ext4: fix ext4_free_inode() vs. ext4_claim_inode() race

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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 
393418676a 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@redhat.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Eric Sandeen 2009-03-04 18:38:18 -05:00 committed by Theodore Ts'o
parent fec6c6fec3
commit 7ce9d5d1f3
1 changed files with 5 additions and 3 deletions
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8
fs/ext4/ialloc.c
View file

@ -188,7 +188,7 @@ void ext4_free_inode(handle_t *handle, struct inode *inode)
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, struct inode *inode)
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 {