Date: Mon, 21 Dec 2015 20:55:10 -0900
From: Kent Overstreet <kent.overstreet@gmail.com>
To: "Artem S. Tashkinov" <t.artem@lycos.com>
Cc: Junichi Nomura <j-nomura@ce.jp.nec.com>, Tejun Heo <tj@kernel.org>,
        "Artem S. Tashkinov" <t.artem@mailcity.com>,
        Christoph Hellwig <hch@lst.de>, Ming Lin <ming.l@ssi.samsung.com>,
        Jens Axboe <axboe@fb.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Steven Whitehouse <swhiteho@redhat.com>,
        IDE-ML <linux-ide@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Ming Lei <tom.leiming@gmail.com>
Subject: Re: IO errors after "block: remove bio_get_nr_vecs()"
Message-ID: <20151222055510.GC26544@kmo-pixel>
References: <CA+55aFwLyGifsQFdYZcWHeaHptxMqO_G25fZjer4R_yk4NtCpA@mail.gmail.com>
 <20151221065528.GA3873@htj.duckdns.org>
 <e53cb2f9d5882b0fbe82c589259bf043@lycos.com>
 <20151221193550.GM4026@mtj.duckdns.org>
 <20151221200721.GN4026@mtj.duckdns.org>
 <20151221210811.GO4026@mtj.duckdns.org>
 <20151222035944.GG20661@kmo-pixel>
 <20151222052611.GA10487@xzibit.linux.bs1.fc.nec.co.jp>
 <20151222053849.GB26544@kmo-pixel>
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On Tue, Dec 22, 2015 at 10:52:37AM +0500, Artem S. Tashkinov wrote:
> On 2015-12-22 10:38, Kent Overstreet wrote:
> >On Tue, Dec 22, 2015 at 05:26:12AM +0000, Junichi Nomura wrote:
> >>On 12/22/15 12:59, Kent Overstreet wrote:
> >>> reproduced it with 32 bit pae:
> >>>
> >>>> 1. Exclude memory above 4G line with boot param "max_addr=4G".
> >>>
> >>> doesn't work - max_addr=1G doesn't work either
> >>>
> >>>> 2. Disable highmem with "highmem=0".
> >>>
> >>> works!
> >>>
> >>>> 3. Try booting 64bit kernel.
> >>>
> >>> works
> >>
> >>blk_queue_bio() does split then bounce, which makes the segment
> >>counting based on pages before bouncing and could go wrong.
> >>
> >>What do you think of a patch like this?
> >
> >Artem, can you give this patch a try?
> 
> 
> This patch ostensibly fixes the issue - at least I cannot immediately
> reproduce it. You can count me in as "Tested-by: Artem S. Tashkinov"

Let's all contemplate the fact that blk_segment_map_sg() _overrunning the end of
the provided sglist_ was this much of a clusterfuck to debug.
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