mtd: mtdblock: call mtd_sync() only if opened for write

Because it is useless to call it if the device is opened in R/O mode, and also
harmful: on CFI NOR flash it may block for long time waiting for erase
operations to complete is another partition with a R/W file-system on this
chip.

Artem Bityutskiy: write commit message, amend the patch to match the latest
tree (we use mtd_sync(), not mtd->sync() nowadays).

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c
index af6591237b9b..6c6d80736fad 100644
--- a/drivers/mtd/mtdblock.c
+++ b/drivers/mtd/mtdblock.c
@@ -321,8 +321,12 @@ static int mtdblock_release(struct mtd_blktrans_dev *mbd)
         mutex_unlock(&mtdblk->cache_mutex);
 
         if (!--mtdblk->count) {
-                /* It was the last usage. Free the cache */
-                mtd_sync(mbd->mtd);
+                /*
+                 * It was the last usage. Free the cache, but only sync if
+                 * opened for writing.
+                 */
+                if (mbd->file_mode & FMODE_WRITE)
+                        mtd_sync(mbd->mtd);
                 vfree(mtdblk->cache_data);
         }