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/xattr.c b/fs/ext2/xattr.c
index e44dc92609b..3b96045a00c 100644
--- a/fs/ext2/xattr.c
+++ b/fs/ext2/xattr.c
@@ -345,7 +345,9 @@ static void ext2_xattr_update_super_block(struct super_block *sb)
         if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
                 return;
 
+        spin_lock(&EXT2_SB(sb)->s_lock);
         EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
+        spin_unlock(&EXT2_SB(sb)->s_lock);
         sb->s_dirt = 1;
         mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 }