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RE: [PATCH] brd: Refuse improperly aligned discard requests

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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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Thread

[PATCH] brd: Refuse improperly aligned discard requests Jan Kara <jack@suse.com> - 2015-11-04 17:20 +0100
  RE: [PATCH] brd: Refuse improperly aligned discard requests "Elliott, Robert (Persistent Memory)" <elliott@hpe.com> - 2015-11-05 05:30 +0100
    Re: [PATCH] brd: Refuse improperly aligned discard requests Jan Kara <jack@suse.cz> - 2015-11-05 09:10 +0100
  Re: [PATCH] brd: Refuse improperly aligned discard requests Jens Axboe <axboe@kernel.dk> - 2015-11-05 21:20 +0100

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