Re: [PATCH v6 5/8] fs: xfs: replace BIO_MAX_SECTORS with BIO_MAX_PAGES

From	Ming Lei <ming.lei@canonical.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v6 5/8] fs: xfs: replace BIO_MAX_SECTORS with BIO_MAX_PAGES
Date	2016-06-02 05:40 +0200
Message-ID	<rFrEd-Dz-1@gated-at.bofh.it> (permalink)
References	<rEvAe-4Ni-11@gated-at.bofh.it> <rEvAe-4Ni-9@gated-at.bofh.it> <rFeH0-BQ-9@gated-at.bofh.it>
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On Wed, Jun 1, 2016 at 9:48 PM, Christoph Hellwig <hch@infradead.org> wrote:
> On Mon, May 30, 2016 at 09:34:33PM +0800, Ming Lei wrote:
>> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
>> index e71cfbd..e5d713b 100644
>> --- a/fs/xfs/xfs_buf.c
>> +++ b/fs/xfs/xfs_buf.c
>> @@ -1157,9 +1157,7 @@ xfs_buf_ioapply_map(
>>
>>  next_chunk:
>>       atomic_inc(&bp->b_io_remaining);
>> -     nr_pages = BIO_MAX_SECTORS >> (PAGE_SHIFT - BBSHIFT);
>> -     if (nr_pages > total_nr_pages)
>> -             nr_pages = total_nr_pages;
>> +     nr_pages = min(total_nr_pages, BIO_MAX_PAGES);
>>
>>       bio = bio_alloc(GFP_NOIO, nr_pages);
>
> While I think this is a useful cleanup on it's own I think
> you'd make everyones life easier if bio_alloc simply clamped down
> the passed nr_pages value to the maximum allowed.

Yes, that looks a good cleanup, but need be careful because the
passed 'nr_pages' can be used after returning from bio_alloc() in
the current function, and it is easy to see this usage.

So we can do that in another patchset instead of this one.

Thanks,

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Re: [PATCH v6 5/8] fs: xfs: replace BIO_MAX_SECTORS with  BIO_MAX_PAGES Christoph Hellwig <hch@infradead.org> - 2016-06-01 15:50 +0200
  Re: [PATCH v6 5/8] fs: xfs: replace BIO_MAX_SECTORS with BIO_MAX_PAGES Ming Lei <ming.lei@canonical.com> - 2016-06-02 05:40 +0200

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