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From: "Elliott, Robert (Persistent Memory)" <elliott@hpe.com>
To: Jan Kara <jack@suse.com>, "axboe@kernel.dk" <axboe@kernel.dk>
Cc: LKML <linux-kernel@vger.kernel.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>
Subject: RE: [PATCH] brd: Refuse improperly aligned discard requests
Date: Thu, 5 Nov 2015 04:18:49 +0000	[thread overview]
Message-ID: <94D0CD8314A33A4D9D801C0FE68B40295BE0AFAA@G4W3202.americas.hpqcorp.net> (raw)
In-Reply-To: <1446653619-22880-1-git-send-email-jack@suse.com>


> -----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


  reply	other threads:[~2015-11-05  4:20 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-04 16:13 [PATCH] brd: Refuse improperly aligned discard requests Jan Kara
2015-11-05  4:18 ` Elliott, Robert (Persistent Memory) [this message]
2015-11-05  8:06   ` Jan Kara
2015-11-05 20:11 ` Jens Axboe

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