Re: [PATCH 11/11] block: don't check for BIO_MAX_PAGES in blk_bio_segment_split()

From	NeilBrown <neilb@suse.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 11/11] block: don't check for BIO_MAX_PAGES in blk_bio_segment_split()
Date	2017-04-24 05:20 +0200
Message-ID	<tzCHD-1ce-5@gated-at.bofh.it> (permalink)
References	<tyd8C-4Wq-7@gated-at.bofh.it> <tyd8C-4Wq-5@gated-at.bofh.it> <tyF4S-5fu-29@gated-at.bofh.it> <tyLN0-Pg-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

[Multipart message — attachments visible in raw view] - view raw

On Fri, Apr 21 2017, Ming Lei wrote:

> On Fri, Apr 21, 2017 at 7:34 PM, Christoph Hellwig <hch@infradead.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);
>

btrfs is a filesystem, not a driver.  So it doesn't count.
The bios it uses were not yet processed by blk_bio_segment_split(),
so changes there cannot be relevant to btrfs.

Thanks,
NeilBrown

Thread

[PATCH 11/11] block: don't check for BIO_MAX_PAGES in  blk_bio_segment_split() NeilBrown <neilb@suse.com> - 2017-04-20 07:50 +0200
  Re: [PATCH 11/11] block: don't check for BIO_MAX_PAGES in  blk_bio_segment_split() Christoph Hellwig <hch@infradead.org> - 2017-04-21 13:40 +0200
    Re: [PATCH 11/11] block: don't check for BIO_MAX_PAGES in blk_bio_segment_split() Ming Lei <tom.leiming@gmail.com> - 2017-04-21 20:50 +0200
      Re: [PATCH 11/11] block: don't check for BIO_MAX_PAGES in blk_bio_segment_split() NeilBrown <neilb@suse.com> - 2017-04-24 05:20 +0200
    Re: [PATCH 11/11] block: don't check for BIO_MAX_PAGES in blk_bio_segment_split() NeilBrown <neilb@suse.com> - 2017-04-24 05:20 +0200

csiph-web