UBIFS: synchronize write-buffer before switching to the next bud

Currently when UBIFS fills up the current bud (which is the last in the journal
head) and switches to the next bud, it first writes the log reference node for
the next bud and only after this synchronizes the write-buffer of the previous
bud. This is not a big deal, but an unclean power cut may lead to a situation
when we have corruption in a next-to-last bud, although it is much more logical
that we have to have corruption only in the last bud.

This patch also removes write-buffer synchronization from
'ubifs_wbuf_seek_nolock()' because this is not needed anymore (we synchronize
the write-buffer explicitly everywhere now) and also because this is just
prone to various errors.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 3 insertions, 9 deletions

diff --git a/fs/ubifs/io.c b/fs/ubifs/io.c
index 67bbde3550c..166951e0dcd 100644
--- a/fs/ubifs/io.c
+++ b/fs/ubifs/io.c
@@ -452,8 +452,8 @@ int ubifs_wbuf_sync_nolock(struct ubifs_wbuf *wbuf)
  * @dtype: data type
  *
  * This function targets the write-buffer to logical eraseblock @lnum:@offs.
- * The write-buffer is synchronized if it is not empty. Returns zero in case of
- * success and a negative error code in case of failure.
+ * The write-buffer has to be empty. Returns zero in case of success and a
+ * negative error code in case of failure.
  */
 int ubifs_wbuf_seek_nolock(struct ubifs_wbuf *wbuf, int lnum, int offs,
 			   int dtype)
@@ -465,13 +465,7 @@ int ubifs_wbuf_seek_nolock(struct ubifs_wbuf *wbuf, int lnum, int offs,
 	ubifs_assert(offs >= 0 && offs <= c->leb_size);
 	ubifs_assert(offs % c->min_io_size == 0 && !(offs & 7));
 	ubifs_assert(lnum != wbuf->lnum);
-
-	if (wbuf->used > 0) {
-		int err = ubifs_wbuf_sync_nolock(wbuf);
-
-		if (err)
-			return err;
-	}
+	ubifs_assert(wbuf->used == 0);
 
 	spin_lock(&wbuf->lock);
 	wbuf->lnum = lnum;