From: Al Viro <viro@ZenIV.linux.org.uk>
To: linux-block@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@lst.de>,
Vitaly Mayatskikh <v.mayatskih@gmail.com>
Subject: Re: [PATCH] fix unbalanced page refcounting in bio_map_user_iov
Date: Sun, 24 Sep 2017 18:15:46 +0100 [thread overview]
Message-ID: <20170924171545.GU32076@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20170924142739.GS32076@ZenIV.linux.org.uk>
On Sun, Sep 24, 2017 at 03:27:39PM +0100, Al Viro wrote:
> At the very least, we need bmd->iter = *iter; bmd->iter.iov = bmd->iov;
> instead of that iov_iter_init() in there. I'm not sure how far back does
> it go; looks like "block: support large requests in blk_rq_map_user_iov"
> is the earliest possible point, but it might need more digging to make
> sure. v4.5+, if that's when the problems began...
>
> Anyway, I'd added the obvious fix to #work.iov_iter, reordered it and
> force-pushed the result.
While we are at it, calculation of nr_pages in bio_copy_user_iov() is bloody
odd - why, in the name of everything unholy, does it care about the iovec
boundaries in there? We are copying data anyway; why does allocation of bio
care about the fragmentation of the other end of copying? Shouldn't it be
simply max(DIV_ROUND_UP(offset + len, PAGE_SIZE), BIO_MAX_PAGES)?
next prev parent reply other threads:[~2017-09-24 17:15 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
2017-09-24 14:27 ` Al Viro
2017-09-24 17:15 ` Al Viro [this message]
2017-09-25 1:48 ` Vitaly Mayatskikh
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