Messages in this thread | | | From | "Elliott, Robert (Persistent Memory)" <> | Subject | RE: [PATCH] brd: Refuse improperly aligned discard requests | Date | Thu, 5 Nov 2015 04:18:49 +0000 |
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> -----Original Message----- > From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel- > owner@vger.kernel.org] On Behalf Of Jan Kara > Sent: Wednesday, November 4, 2015 10:14 AM > To: axboe@kernel.dk > Cc: LKML <linux-kernel@vger.kernel.org>; linux-fsdevel@vger.kernel.org; > Christoph Hellwig <hch@infradead.org>; Jan Kara <jack@suse.com> > 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.
--- Robert Elliott, HP Server Storage
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