ext3: Fix fsync error handling after filesystem abort.

If filesystem was aborted we will return success
due to (sb->s_flags & MS_RDONLY) which is incorrect and
results in data loss.
In order to handle fs abort correctly we have to check
fs state once we discover that it is in MS_RDONLY state

Test case: http://patchwork.ozlabs.org/patch/244297/
Changes from V1:
 - fix spelling
 - fix smp_rmb()/debug order

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Jan Kara <jack@suse.cz>

2 files changed, 18 insertions, 3 deletions

diff --git a/fs/ext3/fsync.c b/fs/ext3/fsync.c
index b31dbd4c46ad..1cb9c7e10c6f 100644
--- a/fs/ext3/fsync.c
+++ b/fs/ext3/fsync.c
@@ -48,9 +48,13 @@ int ext3_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 
         trace_ext3_sync_file_enter(file, datasync);
 
-        if (inode->i_sb->s_flags & MS_RDONLY)
+        if (inode->i_sb->s_flags & MS_RDONLY) {
+                /* Make sure that we read updated state */
+                smp_rmb();
+                if (EXT3_SB(inode->i_sb)->s_mount_state & EXT3_ERROR_FS)
+                        return -EROFS;
                 return 0;
-
+        }
         ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
         if (ret)
                 goto out;
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 6356665a74bb..c47f14750722 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -174,6 +174,11 @@ static void ext3_handle_error(struct super_block *sb)
         if (test_opt (sb, ERRORS_RO)) {
                 ext3_msg(sb, KERN_CRIT,
                         "error: remounting filesystem read-only");
+                /*
+                 * Make sure updated value of ->s_mount_state will be visible
+                 * before ->s_flags update.
+                 */
+                smp_wmb();
                 sb->s_flags |= MS_RDONLY;
         }
         ext3_commit_super(sb, es, 1);
@@ -291,8 +296,14 @@ void ext3_abort(struct super_block *sb, const char *function,
         ext3_msg(sb, KERN_CRIT,
                 "error: remounting filesystem read-only");
         EXT3_SB(sb)->s_mount_state |= EXT3_ERROR_FS;
-        sb->s_flags |= MS_RDONLY;
         set_opt(EXT3_SB(sb)->s_mount_opt, ABORT);
+        /*
+         * Make sure updated value of ->s_mount_state will be visible
+         * before ->s_flags update.
+         */
+        smp_wmb();
+        sb->s_flags |= MS_RDONLY;
+
         if (EXT3_SB(sb)->s_journal)
                 journal_abort(EXT3_SB(sb)->s_journal, -EIO);
 }