From 98262f2762f0067375f83824d81ea929e37e6bfe Mon Sep 17 00:00:00 2001 From: "Martin K. Petersen" Date: Thu, 3 Dec 2009 09:24:48 +0100 Subject: block: Allow devices to indicate whether discarded blocks are zeroed The discard ioctl is used by mkfs utilities to clear a block device prior to putting metadata down. However, not all devices return zeroed blocks after a discard. Some drives return stale data, potentially containing old superblocks. It is therefore important to know whether discarded blocks are properly zeroed. Both ATA and SCSI drives have configuration bits that indicate whether zeroes are returned after a discard operation. Implement a block level interface that allows this information to be bubbled up the stack and queried via a new block device ioctl. Signed-off-by: Martin K. Petersen Signed-off-by: Jens Axboe --- block/ioctl.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'block/ioctl.c') diff --git a/block/ioctl.c b/block/ioctl.c index 1f4d1de12b09..be48ea51faee 100644 --- a/block/ioctl.c +++ b/block/ioctl.c @@ -280,6 +280,8 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd, return put_uint(arg, bdev_io_opt(bdev)); case BLKALIGNOFF: return put_int(arg, bdev_alignment_offset(bdev)); + case BLKDISCARDZEROES: + return put_uint(arg, bdev_discard_zeroes_data(bdev)); case BLKSECTGET: return put_ushort(arg, queue_max_sectors(bdev_get_queue(bdev))); case BLKRASET: -- cgit v1.2.3-59-g8ed1b