From: Al Viro <viro@ZenIV.linux.org.uk>
To: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH] fix unbalanced page refcounting in bio_map_user_iov
Date: Sat, 23 Sep 2017 21:33:23 +0100 [thread overview]
Message-ID: <20170923203323.GR32076@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20170923171925.GQ32076@ZenIV.linux.org.uk>
On Sat, Sep 23, 2017 at 06:19:26PM +0100, Al Viro wrote:
> On Sat, Sep 23, 2017 at 05:55:37PM +0100, Al Viro wrote:
>
> > IOW, the loop on failure exit should go through the bio, like __bio_unmap_user()
> > does. We *also* need to put everything left unused in pages[], but only from the
> > last iteration through iov_for_each().
> >
> > Frankly, I would prefer to reuse the pages[], rather than append to it on each
> > iteration. Used iov_iter_get_pages_alloc(), actually.
>
> Something like completely untested diff below, perhaps...
> + unsigned n = PAGE_SIZE - offs;
> + unsigned prev_bi_vcnt = bio->bi_vcnt;
Sorry, that should've been followed by
if (n > bytes)
n = bytes;
Anyway, a carved-up variant is in vfs.git#work.iov_iter. It still needs
review and testing; the patch Vitaly has posted in this thread plus 6
followups, hopefully more readable than aggregate diff.
Comments?
next prev parent reply other threads:[~2017-09-23 20:33 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-22 5:18 [PATCH] fix unbalanced page refcounting in bio_map_user_iov Vitaly Mayatskikh
2017-09-22 5:24 ` Vitaly Mayatskikh
2017-09-23 16:39 ` Al Viro
2017-09-23 16:55 ` Al Viro
2017-09-23 17:19 ` Al Viro
2017-09-23 20:33 ` Al Viro [this message]
2017-09-24 14:27 ` Al Viro
2017-09-24 17:15 ` Al Viro
2017-09-25 1:48 ` Vitaly Mayatskikh
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