Commit 7ce9d5d1 authored Mar 04, 2009 by Eric Sandeen Committed by Theodore Ts'o Mar 04, 2009

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



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 
39341867 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>

parent fec6c6fe

fs/ext4/ialloc.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -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 {

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