ext4: add checks for errors from jbd2

If the journal has aborted due to a checkpointing failure, we
have to keep the contents of the journal space.  Otherwise, the
filesystem will lose uncheckpointed metadata completely and
become inconsistent.  To avoid this, we need to keep needs_recovery
flag if checkpoint has failed.

With this patch, ext4_put_super() detects a checkpointing failure
from the return value of journal_destroy(), then it invokes
ext4_abort() to make the filesystem read only and keep
needs_recovery flag.  Errors from jbd2_journal_flush() are also
handled by this patch in some places.

Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 0e661c5..79bd398 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -507,7 +507,8 @@
 	ext4_mb_release(sb);
 	ext4_ext_release(sb);
 	ext4_xattr_put_super(sb);
-	jbd2_journal_destroy(sbi->s_journal);
+	if (jbd2_journal_destroy(sbi->s_journal) < 0)
+		ext4_abort(sb, __func__, "Couldn't clean up the journal");
 	sbi->s_journal = NULL;
 	if (!(sb->s_flags & MS_RDONLY)) {
 		EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
@@ -2853,7 +2854,9 @@
 	journal_t *journal = EXT4_SB(sb)->s_journal;
 
 	jbd2_journal_lock_updates(journal);
-	jbd2_journal_flush(journal);
+	if (jbd2_journal_flush(journal) < 0)
+		goto out;
+
 	lock_super(sb);
 	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER) &&
 	    sb->s_flags & MS_RDONLY) {
@@ -2862,6 +2865,8 @@
 		ext4_commit_super(sb, es, 1);
 	}
 	unlock_super(sb);
+
+out:
 	jbd2_journal_unlock_updates(journal);
 }
 
@@ -2962,7 +2967,13 @@
 
 		/* Now we set up the journal barrier. */
 		jbd2_journal_lock_updates(journal);
-		jbd2_journal_flush(journal);
+
+		/*
+		 * We don't want to clear needs_recovery flag when we failed
+		 * to flush the journal.
+		 */
+		if (jbd2_journal_flush(journal) < 0)
+			return;
 
 		/* Journal blocked and flushed, clear needs_recovery flag. */
 		EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
@@ -3402,8 +3413,12 @@
 		 * otherwise be livelocked...
 		 */
 		jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal);
-		jbd2_journal_flush(EXT4_SB(sb)->s_journal);
+		err = jbd2_journal_flush(EXT4_SB(sb)->s_journal);
 		jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
+		if (err) {
+			path_put(&nd.path);
+			return err;
+		}
 	}
 
 	err = vfs_quota_on_path(sb, type, format_id, &nd.path);