From: Alexander Stein <alexander.stein@systec-electronic.com>
Date: Tue, 10 Jan 2012 12:26:58 +0000 (+0100)
Subject: mtd: mtdblock: call mtd_sync() only if opened for write
X-Git-Tag: v3.4-rc1~16^2~117
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=70d5098a4b1551864dd7df43f67b7f606a1a6438;p=linux.git

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>
---

diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
index 424ca5f93c6c..f1f06715d4e0 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 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);
 	}
 
diff --git a/include/linux/mtd/blktrans.h b/include/linux/mtd/blktrans.h
index 1bbd9f289245..ed270bd2e4df 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 {