From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sergei Antonov <saproj@gmail.com>
Subject: Re: [PATCH] hfsplus: fix cross-page bio requests
Date: Sun, 7 Jun 2015 22:09:21 +0200
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Cc: "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	Anton Altaparmakov <aia21@cam.ac.uk>,
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To: Viacheslav Dubeyko <slava@dubeyko.com>
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On 7 June 2015 at 22:05, Sergei Antonov <saproj@gmail.com> wrote:
> On 10 April 2015 at 18:48, Viacheslav Dubeyko <slava@dubeyko.com> wrote:
>> On Fri, 2015-04-10 at 11:02 +0200, Sergei Antonov wrote:
>>> Function hfsplus_submit_bio() did not work when the passed buffer spanned
>>> over more than one page. That was because bio_alloc() is passed 1 as a number
>>> of vectors but more than one vector were added inside the 'while' loop.
>>> It periodically caused a mount error when the volume header could not be read.
>>>
>>> This patch modifies the code so that only one vector is used. It works for
>>> multiple pages too. Also adds a return code check after bio_alloc().
>>
>> I think that it really makes sense to describe the issue's reproducing
>> way. It will be really precious for understanding of symptoms and
>> reasons of the issue.
>>
>> Could you add more detailed description?
>>
>> Then, I will have opportunity to test your patch.
>
> Well, the description says it all. To put it bluntly, when this line
> from wrapper.c
>   sbi->s_vhdr_buf = kmalloc(hfsplus_min_io_size(sb), GFP_KERNEL);
> assigns s_vhdr_buf a value satisfying condition (PAGE_SIZE - (value &
> PAGE_SIZE) < 512) then this call (also from wrapper.c) returns an

I'm sorry, the right condition is (PAGE_SIZE - (value & (PAGE_SIZE - 1)) < 512).

> error:
>   error = hfsplus_submit_bio(sb, part_start + HFSPLUS_VOLHEAD_SECTOR,
>     sbi->s_vhdr_buf, (void **)&sbi->s_vhdr,
>     READ);
>
> To give a specific example, sbi->s_vhdr_buf equal to
> 0xffff8804085acec0 spans two pages and hfsplus_submit_bio() can not
> read into such a buffer, returns an error, mount operation fails.