brd: remove support for BLKFLSBUF

Discontinue having the brd driver destructively free all pages in the
ramdisk in response to the BLKFLSBUF ioctl.  Doing so allows a BLKFLSBUF
ioctl issued to a logical partition to destroy pages of the parent brd
device (and all other partitions of that brd device).

This change breaks compatibility - but in this case the compatibility
breaks more than it helps.

Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 0 insertions, 35 deletions

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 9d5335857191..ad793f35632c 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -395,44 +395,9 @@ static long brd_direct_access(struct block_device *bdev, sector_t sector,
 #define brd_direct_access NULL
 #endif
 
-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,
         .direct_access =        brd_direct_access,
 };