From: Christoph Hellwig <hch@infradead.org>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@infradead.org>,
linux-block@vger.kernel.org,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
xfs <linux-xfs@vger.kernel.org>
Subject: Re: [PATCH] loop: fix no-unmap write-zeroes request behavior
Date: Fri, 11 Oct 2019 00:51:44 -0700 [thread overview]
Message-ID: <20191011075144.GA26033@infradead.org> (raw)
In-Reply-To: <20191010170239.GC13098@magnolia>
On Thu, Oct 10, 2019 at 10:02:39AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> Currently, if the loop device receives a WRITE_ZEROES request, it asks
> the underlying filesystem to punch out the range. This behavior is
> correct if unmapping is allowed. However, a NOUNMAP request means that
> the caller forbids us from freeing the storage backing the range, so
> punching out the range is incorrect behavior.
It doesn't really forbid, as most protocols don't have a way for forbid
deallocation. It requests not to.
Otherwise this looks fine, although I would have implemented it slightly
differently:
> case REQ_OP_FLUSH:
> return lo_req_flush(lo, rq);
> case REQ_OP_DISCARD:
> - case REQ_OP_WRITE_ZEROES:
> return lo_discard(lo, rq, pos);
> + case REQ_OP_WRITE_ZEROES:
> + return lo_zeroout(lo, rq, pos);
This could just become:
case REQ_OP_WRITE_ZEROES:
if (rq->cmd_flags & REQ_NOUNMAP))
return lo_zeroout(lo, rq, pos);
/*FALLTHRU*/
case REQ_OP_DISCARD:
return lo_discard(lo, rq, pos);
next prev parent reply other threads:[~2019-10-11 7:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-10 17:02 [PATCH] loop: fix no-unmap write-zeroes request behavior Darrick J. Wong
2019-10-11 7:51 ` Christoph Hellwig [this message]
2019-10-11 16:05 ` [PATCH v2] " Darrick J. Wong
2019-10-14 7:28 ` Christoph Hellwig
2019-10-14 15:50 ` [PATCH v3] " Darrick J. Wong
2019-10-14 16:39 ` Eric Sandeen
2019-10-14 17:00 ` Darrick J. Wong
2019-10-15 7:58 ` Christoph Hellwig
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