UBIFS: make space fixup work in the remount case

The UBIFS space fixup is a useful feature which allows to fixup the "broken"
flash space at the time of the first mount. The "broken" space is usually the
result of using a "dumb" industrial flasher which is not able to skip empty
NAND pages and just writes all 0xFFs to the empty space, which has grave
side-effects for UBIFS when UBIFS trise to write useful data to those empty
pages.

The fix-up feature works roughly like this:
1. mkfs.ubifs sets the fixup flag in UBIFS superblock when creating the image
   (see -F option)
2. when the file-system is mounted for the first time, UBIFS notices the fixup
   flag and re-writes the entire media atomically, which may take really a lot
   of time.
3. UBIFS clears the fixup flag in the superblock.

This works fine when the file system is mounted R/W for the very first time.
But it did not really work in the case when we first mount the file-system R/O,
and then re-mount R/W. The reason was that we started the fixup procedure too
late, which we cannot really do because we have to fixup the space before it
starts being used.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Reported-by: Mark Jackson <mpfj-list@mimc.co.uk>
Cc: stable@vger.kernel.org # 3.0+

1 files changed, 6 insertions, 6 deletions

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index ac838b844936..f21acf0ef01f 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -1568,6 +1568,12 @@ static int ubifs_remount_rw(struct ubifs_info *c)
         c->remounting_rw = 1;
         c->ro_mount = 0;
 
+        if (c->space_fixup) {
+                err = ubifs_fixup_free_space(c);
+                if (err)
+                        return err;
+        }
+
         err = check_free_space(c);
         if (err)
                 goto out;
@@ -1684,12 +1690,6 @@ static int ubifs_remount_rw(struct ubifs_info *c)
                 err = dbg_check_space_info(c);
         }
 
-        if (c->space_fixup) {
-                err = ubifs_fixup_free_space(c);
-                if (err)
-                        goto out;
-        }
-
         mutex_unlock(&c->umount_mutex);
         return err;