ext2: Add ext2_sb_info s_lock spinlock

Add a spinlock that protects against concurrent modifications of
s_mount_state, s_blocks_last, s_overhead_last and the content of the
superblock's buffer pointed to by sbi->s_es. The spinlock is now used in
ext2_xattr_update_super_block() which was setting the
EXT2_FEATURE_COMPAT_EXT_ATTR flag on the superblock without protection
before. Likewise the spinlock is used in ext2_show_options() to have a
consistent view of the mount options.

This is a preparation patch for removing the BKL from ext2 in the next
patch.

Signed-off-by: Jan Blunck <jblunck@suse.de>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jan Kara <jack@suse.cz>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index fc13cc119aad..5d15442abbd0 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -1407,9 +1407,11 @@ static int __ext2_write_inode(struct inode *inode, int do_sync)
                                 * created, add a flag to the superblock.
                                 */
                                 lock_kernel();
+                                spin_lock(&EXT2_SB(sb)->s_lock);
                                 ext2_update_dynamic_rev(sb);
                                 EXT2_SET_RO_COMPAT_FEATURE(sb,
                                         EXT2_FEATURE_RO_COMPAT_LARGE_FILE);
+                                spin_unlock(&EXT2_SB(sb)->s_lock);
                                 unlock_kernel();
                                 ext2_write_super(sb);
                         }