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, 9 insertions, 0 deletions

diff --git a/include/linux/ext2_fs_sb.h b/include/linux/ext2_fs_sb.h
index 1cdb66367c98..db4d9f586bb6 100644
--- a/include/linux/ext2_fs_sb.h
+++ b/include/linux/ext2_fs_sb.h
@@ -106,6 +106,15 @@ struct ext2_sb_info {
         spinlock_t s_rsv_window_lock;
         struct rb_root s_rsv_window_root;
         struct ext2_reserve_window_node s_rsv_window_head;
+        /*
+         * s_lock protects against concurrent modifications of s_mount_state,
+         * s_blocks_last, s_overhead_last and the content of superblock's
+         * buffer pointed to by sbi->s_es.
+         *
+         * Note: It is used in ext2_show_options() to provide a consistent view
+         * of the mount options.
+         */
+        spinlock_t s_lock;
 };
 
 static inline spinlock_t *