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

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=70d5098a4b1551864dd7df43f67b7f606a1a6438
Commit:     70d5098a4b1551864dd7df43f67b7f606a1a6438
Parent:     2ff5e1532dd37e1bd8ac72da3f7f0e2b310102fb
Author:     Alexander Stein <alexander.stein at systec-electronic.com>
AuthorDate: Tue Jan 10 13:26:58 2012 +0100
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Tue Mar 27 00:11:11 2012 +0100

    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 at systec-electronic.com>
    Signed-off-by: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/mtd_blkdevs.c    |    1 +
 drivers/mtd/mtdblock.c       |    8 ++++++--
 include/linux/mtd/blktrans.h |    1 +
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
index 424ca5f..f1f0671 100644
--- a/drivers/mtd/mtd_blkdevs.c
+++ b/drivers/mtd/mtd_blkdevs.c
@@ -233,6 +233,7 @@ static int blktrans_open(struct block_device *bdev, fmode_t mode)
 	ret = __get_mtd_device(dev->mtd);
 	if (ret)
 		goto error_release;
+	dev->file_mode = mode;
 
 unlock:
 	dev->open++;
diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c
index af65912..6c6d807 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);
 	}
 
diff --git a/include/linux/mtd/blktrans.h b/include/linux/mtd/blktrans.h
index 1bbd9f2..ed270bd 100644
--- a/include/linux/mtd/blktrans.h
+++ b/include/linux/mtd/blktrans.h
@@ -47,6 +47,7 @@ struct mtd_blktrans_dev {
 	struct request_queue *rq;
 	spinlock_t queue_lock;
 	void *priv;
+	fmode_t file_mode;
 };
 
 struct mtd_blktrans_ops {