ext4: fix warning when submitting superblock in ext4_commit_super()

We have already check the io_error and uptodate flag before submitting
the superblock buffer, and re-set the uptodate flag if it has been
failed to write out. But it was lockless and could be raced by another
ext4_commit_super(), and finally trigger '!uptodate' WARNING when
marking buffer dirty. Fix it by submit buffer directly.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ritesh Harjani <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20220520023216.3065073-1-yi.zhang@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 450c918..b2ecae8 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5898,7 +5898,6 @@ static void ext4_update_super(struct super_block *sb)
 static int ext4_commit_super(struct super_block *sb)
 {
        struct buffer_head *sbh = EXT4_SB(sb)->s_sbh;
-       int error = 0;
 
        if (!sbh)
                return -EINVAL;
@@ -5907,6 +5906,13 @@ static int ext4_commit_super(struct super_block *sb)
 
        ext4_update_super(sb);
 
+       lock_buffer(sbh);
+       /* Buffer got discarded which means block device got invalidated */
+       if (!buffer_mapped(sbh)) {
+               unlock_buffer(sbh);
+               return -EIO;
+       }
+
        if (buffer_write_io_error(sbh) || !buffer_uptodate(sbh)) {
                /*
                 * Oh, dear.  A previous attempt to write the
@@ -5921,17 +5927,21 @@ static int ext4_commit_super(struct super_block *sb)
                clear_buffer_write_io_error(sbh);
                set_buffer_uptodate(sbh);
        }
-       BUFFER_TRACE(sbh, "marking dirty");
-       mark_buffer_dirty(sbh);
-       error = __sync_dirty_buffer(sbh,
-               REQ_SYNC | (test_opt(sb, BARRIER) ? REQ_FUA : 0));
+       get_bh(sbh);
+       /* Clear potential dirty bit if it was journalled update */
+       clear_buffer_dirty(sbh);
+       sbh->b_end_io = end_buffer_write_sync;
+       submit_bh(REQ_OP_WRITE,
+                 REQ_SYNC | (test_opt(sb, BARRIER) ? REQ_FUA : 0), sbh);
+       wait_on_buffer(sbh);
        if (buffer_write_io_error(sbh)) {
                ext4_msg(sb, KERN_ERR, "I/O error while writing "
                       "superblock");
                clear_buffer_write_io_error(sbh);
                set_buffer_uptodate(sbh);
+               return -EIO;
        }
-       return error;
+       return 0;
 }
 
 /*