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/compat_ioctl.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'block/compat_ioctl.c') diff --git a/block/compat_ioctl.c b/block/compat_ioctl.c index 9bd086c1a4d5..4eb8e9ea4af5 100644 --- a/block/compat_ioctl.c +++ b/block/compat_ioctl.c @@ -747,6 +747,8 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg) return compat_put_uint(arg, bdev_io_opt(bdev)); case BLKALIGNOFF: return compat_put_int(arg, bdev_alignment_offset(bdev)); + case BLKDISCARDZEROES: + return compat_put_uint(arg, bdev_discard_zeroes_data(bdev)); case BLKFLSBUF: case BLKROSET: case BLKDISCARD: -- cgit v1.2.3