linux-kernel - Re: [PATCH 11/11] block: don't check for BIO_MAX_PAGES in blk_bio_segment

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Date:   Fri, 21 Apr 2017 23:48:59 +0800
From:   Ming Lei <tom.leiming@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     NeilBrown <neilb@...e.com>, Jens Axboe <axboe@...nel.dk>,
        linux-block <linux-block@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 11/11] block: don't check for BIO_MAX_PAGES in blk_bio_segment_split()

On Fri, Apr 21, 2017 at 7:34 PM, Christoph Hellwig <hch@...radead.org> wrote:
> On Thu, Apr 20, 2017 at 03:38:50PM +1000, NeilBrown wrote:
>> blk_bio_segment_split() makes sure bios have no more than
>> BIO_MAX_PAGES entries in the bi_io_vec.
>> This was done because bio_clone_bioset() (when given a
>> mempool bioset) could not handle larger io_vecs.
>>
>> No driver uses bio_clone_bioset() any more, they all
>> use bio_clone_fast() if anything, and bio_clone_fast()
>> doesn't clone the bi_io_vec.
>
> Hmm.  From Jens tree:
>
> drivers/lightnvm/pblk-read.c:           int_bio = bio_clone_bioset(bio, GFP_KERNEL, fs_bio_set);
> drivers/md/raid1.c:                             mbio = bio_clone_bioset_partial(bio, GFP_NOIO,
> drivers/md/raid1.c:                             mbio = bio_clone_bioset_partial(bio, GFP_NOIO,

Btrfs use bio_clone_bioset() too:

     fs/btrfs/extent_io.c:2703:      new = bio_clone_bioset(bio,
gfp_mask, btrfs_bioset);

Thanks,
Ming Lei