On Thu 05-11-15 04:18:49, Elliott, Robert (Persistent Memory) wrote: > > > -----Original Message----- > > From: linux-kernel-owner@xxxxxxxxxxxxxxx [mailto:linux-kernel- > > owner@xxxxxxxxxxxxxxx] On Behalf Of Jan Kara > > Sent: Wednesday, November 4, 2015 10:14 AM > > To: axboe@xxxxxxxxx > > Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>; linux-fsdevel@xxxxxxxxxxxxxxx; > > Christoph Hellwig <hch@xxxxxxxxxxxxx>; Jan Kara <jack@xxxxxxxx> > > Subject: [PATCH] brd: Refuse improperly aligned discard requests > > > > Currently when improperly aligned discard request is submitted, we just > > silently discard more / less data which results in filesystem corruption > > in some cases. Refuse such misaligned requests. > > I agree discarding more than requested is very bad. > > If they are routed to SCSI or ATA devices, though, the discard commands > (SCSI UNMAP or ATA DATA SET MANAGEMENT/TRIM) are just hints, so there > is no guarantee the discard will do anything. Are you finding > filesystems that still don't understand that? dm-raid held that > mistaken assumption for a long time. So there is blkdev_issue_zeroout() which uses blkdev_issue_discard() if 'discard_zeroes_data' is set. I'd hope that in that case zeroing really happens as submitted or error is returned... Filesystems definitely depend on blkdev_issue_zeroout() doing what it is told. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
