Commit 6f2e9f0e authored May 28, 2012 by Tao Ma Committed by Theodore Ts'o May 28, 2012

ext4: protect group inode free counting with group lock



Now when we set the group inode free count, we don't have a proper
group lock so that multiple threads may decrease the inode free
count at the same time. And e2fsck will complain something like:

Free inodes count wrong for group #1 (1, counted=0).
Fix? no

Free inodes count wrong for group #2 (3, counted=0).
Fix? no

Directories count wrong for group #2 (780, counted=779).
Fix? no

Free inodes count wrong for group #3 (2272, counted=2273).
Fix? no

So this patch try to protect it with the ext4_lock_group.

btw, it is found by xfstests test case 269 and the volume is
mkfsed with the parameter
"-O ^resize_inode,^uninit_bg,extent,meta_bg,flex_bg,ext_attr"
and I have run it 100 times and the error in e2fsck doesn't
show up again.

Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

parent 8563000d

fs/ext4/ialloc.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -797,7 +797,10 @@ got:
		ext4_itable_unused_set(sb, gdp,
		(EXT4_INODES_PER_GROUP(sb) - ino));
		up_read(&grp->alloc_sem);
		} else {
		ext4_lock_group(sb, group);
		}

		ext4_free_inodes_set(sb, gdp, ext4_free_inodes_count(sb, gdp) - 1);
		if (S_ISDIR(mode)) {
		ext4_used_dirs_set(sb, gdp, ext4_used_dirs_count(sb, gdp) + 1);
		@@ -811,8 +814,8 @@ got:
		ext4_inode_bitmap_csum_set(sb, group, gdp, inode_bitmap_bh,
		EXT4_INODES_PER_GROUP(sb) / 8);
		ext4_group_desc_csum_set(sb, group, gdp);
		ext4_unlock_group(sb, group);
		}
		ext4_unlock_group(sb, group);

		BUFFER_TRACE(inode_bitmap_bh, "call ext4_handle_dirty_metadata");
		err = ext4_handle_dirty_metadata(handle, NULL, inode_bitmap_bh);

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