From: Seung-Woo Kim <sw0312.kim@samsung.com>
Date: Fri, 31 Jul 2020 06:19:08 +0000 (+0900)
Subject: Revert "brd: remove support for BLKFLSBUF"
X-Git-Tag: accepted/tizen/unified/20200806.062547^0
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f92b4570ea191cd1a53d375a883c8998849d70cb;p=platform%2Fkernel%2Flinux-rpi.git

Revert "brd: remove support for BLKFLSBUF"

This reverts commit ff26956875c2f05e12ecec9938411a2c7dfc767d.

To free ramdisk memory, BLKFLSBUF support is required.

Change-Id: Ib363fdcb65a21914c8baa2099e4b1ce6242428e2
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
---

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 502f72d..0b4dced 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -374,9 +374,44 @@ static int brd_rw_page(struct block_device *bdev, sector_t sector,
 	return err;
 }
 
+static int brd_ioctl(struct block_device *bdev, fmode_t mode,
+			unsigned int cmd, unsigned long arg)
+{
+	int error;
+	struct brd_device *brd = bdev->bd_disk->private_data;
+
+	if (cmd != BLKFLSBUF)
+		return -ENOTTY;
+
+	/*
+	 * ram device BLKFLSBUF has special semantics, we want to actually
+	 * release and destroy the ramdisk data.
+	 */
+	mutex_lock(&brd_mutex);
+	mutex_lock(&bdev->bd_mutex);
+	error = -EBUSY;
+	if (bdev->bd_openers <= 1) {
+		/*
+		 * Kill the cache first, so it isn't written back to the
+		 * device.
+		 *
+		 * Another thread might instantiate more buffercache here,
+		 * but there is not much we can do to close that race.
+		 */
+		kill_bdev(bdev);
+		brd_free_pages(brd);
+		error = 0;
+	}
+	mutex_unlock(&bdev->bd_mutex);
+	mutex_unlock(&brd_mutex);
+
+	return error;
+}
+
 static const struct block_device_operations brd_fops = {
 	.owner =		THIS_MODULE,
 	.rw_page =		brd_rw_page,
+	.ioctl =		brd_ioctl,
 };
 
 /*