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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>
This commit is contained in:
Mike Snitzer 2016-10-25 08:46:23 -06:00 committed by Jens Axboe
parent 366f4aea64
commit ff26956875
1 changed files with 0 additions and 35 deletions
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35
drivers/block/brd.c
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@ -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,
};