diff mbox

[V7,10/24] block: introduce multipage page bvec helpers

Message ID 20180627124548.3456-11-ming.lei@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Ming Lei June 27, 2018, 12:45 p.m. UTC 
This patch introduces helpers of 'mp_bvec_iter_*' for multipage
bvec support.

The introduced interfaces treate one bvec as real multipage segment,
for example, .bv_len is the total length of the multipage bvec.

The existed helpers of bvec_iter_* are interfaces for supporting current
bvec iterator which is thought as singlepage only by drivers, fs, dm and
etc. These introduced helpers will build singlepage bvec in flight, so
users of current bio/bvec iterator still can work well and needn't any
change even though we store real multipage io vector into bvec table.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/bvec.h | 63 +++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 60 insertions(+), 3 deletions(-)

Comments

kernel test robot June 27, 2018, 3:59 p.m. UTC | #1 
Hi Ming,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.18-rc2]
[cannot apply to next-20180627]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Ming-Lei/block-support-multipage-bvec/20180627-214022
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)

   net/ceph/messenger.c:842:25: sparse: expression using sizeof(void)
   net/ceph/messenger.c:842:25: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
   include/linux/bvec.h:140:32: sparse: expression using sizeof(void)
   include/linux/bvec.h:140:32: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
   net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>> net/ceph/messenger.c:890:47: sparse: too many warnings

vim +890 net/ceph/messenger.c

6aaa4511 Alex Elder      2013-03-06  862  
8ae4f4f5 Alex Elder      2013-03-14  863  static bool ceph_msg_data_bio_advance(struct ceph_msg_data_cursor *cursor,
8ae4f4f5 Alex Elder      2013-03-14  864  					size_t bytes)
6aaa4511 Alex Elder      2013-03-06  865  {
5359a17d Ilya Dryomov    2018-01-20  866  	struct ceph_bio_iter *it = &cursor->bio_iter;
6aaa4511 Alex Elder      2013-03-06  867  
5359a17d Ilya Dryomov    2018-01-20  868  	BUG_ON(bytes > cursor->resid);
5359a17d Ilya Dryomov    2018-01-20  869  	BUG_ON(bytes > bio_iter_len(it->bio, it->iter));
25aff7c5 Alex Elder      2013-03-11  870  	cursor->resid -= bytes;
5359a17d Ilya Dryomov    2018-01-20  871  	bio_advance_iter(it->bio, &it->iter, bytes);
f38a5181 Kent Overstreet 2013-08-07  872  
5359a17d Ilya Dryomov    2018-01-20  873  	if (!cursor->resid) {
5359a17d Ilya Dryomov    2018-01-20  874  		BUG_ON(!cursor->last_piece);
5359a17d Ilya Dryomov    2018-01-20  875  		return false;   /* no more data */
5359a17d Ilya Dryomov    2018-01-20  876  	}
f38a5181 Kent Overstreet 2013-08-07  877  
5359a17d Ilya Dryomov    2018-01-20  878  	if (!bytes || (it->iter.bi_size && it->iter.bi_bvec_done))
6aaa4511 Alex Elder      2013-03-06  879  		return false;	/* more bytes to process in this segment */
6aaa4511 Alex Elder      2013-03-06  880  
5359a17d Ilya Dryomov    2018-01-20  881  	if (!it->iter.bi_size) {
5359a17d Ilya Dryomov    2018-01-20  882  		it->bio = it->bio->bi_next;
5359a17d Ilya Dryomov    2018-01-20  883  		it->iter = it->bio->bi_iter;
5359a17d Ilya Dryomov    2018-01-20  884  		if (cursor->resid < it->iter.bi_size)
5359a17d Ilya Dryomov    2018-01-20  885  			it->iter.bi_size = cursor->resid;
25aff7c5 Alex Elder      2013-03-11  886  	}
6aaa4511 Alex Elder      2013-03-06  887  
5359a17d Ilya Dryomov    2018-01-20  888  	BUG_ON(cursor->last_piece);
5359a17d Ilya Dryomov    2018-01-20  889  	BUG_ON(cursor->resid < bio_iter_len(it->bio, it->iter));
5359a17d Ilya Dryomov    2018-01-20 @890  	cursor->last_piece = cursor->resid == bio_iter_len(it->bio, it->iter);
6aaa4511 Alex Elder      2013-03-06  891  	return true;
6aaa4511 Alex Elder      2013-03-06  892  }
ea96571f Alex Elder      2013-04-05  893  #endif /* CONFIG_BLOCK */
df6ad1f9 Alex Elder      2012-06-11  894  

:::::: The code at line 890 was first introduced by commit
:::::: 5359a17d2706b86da2af83027343d5eb256f7670 libceph, rbd: new bio handling code (aka don't clone bios)

:::::: TO: Ilya Dryomov <idryomov@gmail.com>
:::::: CC: Ilya Dryomov <idryomov@gmail.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
Ming Lei Nov. 9, 2018, 11:15 a.m. UTC | #2 
On Wed, Jun 27, 2018 at 11:59:37PM +0800, kbuild test robot wrote:
> Hi Ming,
> 
> Thank you for the patch! Perhaps something to improve:
> 
> [auto build test WARNING on linus/master]
> [also build test WARNING on v4.18-rc2]
> [cannot apply to next-20180627]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> 
> url:    https://github.com/0day-ci/linux/commits/Ming-Lei/block-support-multipage-bvec/20180627-214022
> reproduce:
>         # apt-get install sparse
>         make ARCH=x86_64 allmodconfig
>         make C=1 CF=-D__CHECK_ENDIAN__
> 
> 
> sparse warnings: (new ones prefixed by >>)
> 
>    net/ceph/messenger.c:842:25: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:842:25: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:847:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:848:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:855:29: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:869:9: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:139:37: sparse: expression using sizeof(void)
>    include/linux/bvec.h:140:32: sparse: expression using sizeof(void)
>    include/linux/bvec.h:140:32: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:889:9: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
>    net/ceph/messenger.c:890:47: sparse: expression using sizeof(void)
> >> net/ceph/messenger.c:890:47: sparse: too many warnings
> 
> vim +890 net/ceph/messenger.c
> 
> 6aaa4511 Alex Elder      2013-03-06  862  
> 8ae4f4f5 Alex Elder      2013-03-14  863  static bool ceph_msg_data_bio_advance(struct ceph_msg_data_cursor *cursor,
> 8ae4f4f5 Alex Elder      2013-03-14  864  					size_t bytes)
> 6aaa4511 Alex Elder      2013-03-06  865  {
> 5359a17d Ilya Dryomov    2018-01-20  866  	struct ceph_bio_iter *it = &cursor->bio_iter;
> 6aaa4511 Alex Elder      2013-03-06  867  
> 5359a17d Ilya Dryomov    2018-01-20  868  	BUG_ON(bytes > cursor->resid);
> 5359a17d Ilya Dryomov    2018-01-20  869  	BUG_ON(bytes > bio_iter_len(it->bio, it->iter));
> 25aff7c5 Alex Elder      2013-03-11  870  	cursor->resid -= bytes;
> 5359a17d Ilya Dryomov    2018-01-20  871  	bio_advance_iter(it->bio, &it->iter, bytes);
> f38a5181 Kent Overstreet 2013-08-07  872  
> 5359a17d Ilya Dryomov    2018-01-20  873  	if (!cursor->resid) {
> 5359a17d Ilya Dryomov    2018-01-20  874  		BUG_ON(!cursor->last_piece);
> 5359a17d Ilya Dryomov    2018-01-20  875  		return false;   /* no more data */
> 5359a17d Ilya Dryomov    2018-01-20  876  	}
> f38a5181 Kent Overstreet 2013-08-07  877  
> 5359a17d Ilya Dryomov    2018-01-20  878  	if (!bytes || (it->iter.bi_size && it->iter.bi_bvec_done))
> 6aaa4511 Alex Elder      2013-03-06  879  		return false;	/* more bytes to process in this segment */
> 6aaa4511 Alex Elder      2013-03-06  880  
> 5359a17d Ilya Dryomov    2018-01-20  881  	if (!it->iter.bi_size) {
> 5359a17d Ilya Dryomov    2018-01-20  882  		it->bio = it->bio->bi_next;
> 5359a17d Ilya Dryomov    2018-01-20  883  		it->iter = it->bio->bi_iter;
> 5359a17d Ilya Dryomov    2018-01-20  884  		if (cursor->resid < it->iter.bi_size)
> 5359a17d Ilya Dryomov    2018-01-20  885  			it->iter.bi_size = cursor->resid;
> 25aff7c5 Alex Elder      2013-03-11  886  	}
> 6aaa4511 Alex Elder      2013-03-06  887  
> 5359a17d Ilya Dryomov    2018-01-20  888  	BUG_ON(cursor->last_piece);
> 5359a17d Ilya Dryomov    2018-01-20  889  	BUG_ON(cursor->resid < bio_iter_len(it->bio, it->iter));
> 5359a17d Ilya Dryomov    2018-01-20 @890  	cursor->last_piece = cursor->resid == bio_iter_len(it->bio, it->iter);
> 6aaa4511 Alex Elder      2013-03-06  891  	return true;
> 6aaa4511 Alex Elder      2013-03-06  892  }
> ea96571f Alex Elder      2013-04-05  893  #endif /* CONFIG_BLOCK */
> df6ad1f9 Alex Elder      2012-06-11  894  
> 
> :::::: The code at line 890 was first introduced by commit
> :::::: 5359a17d2706b86da2af83027343d5eb256f7670 libceph, rbd: new bio handling code (aka don't clone bios)
> 
> :::::: TO: Ilya Dryomov <idryomov@gmail.com>
> :::::: CC: Ilya Dryomov <idryomov@gmail.com>
> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Actually this sparse warning on bio_iter_len() can be triggered without this patch
too. This patch changes code in bvec.h, just causes the warned line changed. 


thanks,
Ming
diff mbox

Patch

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index fe7a22dd133b..03a12fbb90d8 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -23,6 +23,44 @@ 
 #include <linux/kernel.h>
 #include <linux/bug.h>
 #include <linux/errno.h>
+#include <linux/mm.h>
+
+/*
+ * What is multipage bvecs?
+ *
+ * - bvec stored in bio->bi_io_vec is always multipage(mp) style
+ *
+ * - bvec(struct bio_vec) represents one physically contiguous I/O
+ *   buffer, now the buffer may include more than one pages since
+ *   multipage(mp) bvec is supported, and all these pages represented
+ *   by one bvec is physically contiguous. Before mp support, at most
+ *   one page can be included in one bvec, we call it singlepage(sp)
+ *   bvec.
+ *
+ * - .bv_page of the bvec represents the 1st page in the mp bvec
+ *
+ * - .bv_offset of the bvec represents offset of the buffer in the bvec
+ *
+ * The effect on the current drivers/filesystem/dm/bcache/...:
+ *
+ * - almost everyone supposes that one bvec only includes one single
+ *   page, so we keep the sp interface not changed, for example,
+ *   bio_for_each_segment() still returns bvec with single page
+ *
+ * - bio_for_each_segment*() will be changed to return singlepage
+ *   bvec too
+ *
+ * - during iterating, iterator variable(struct bvec_iter) is always
+ *   updated in multipage bvec style and that means bvec_iter_advance()
+ *   is kept not changed
+ *
+ * - returned(copied) singlepage bvec is generated in flight by bvec
+ *   helpers from the stored multipage bvec
+ *
+ * - In case that some components(such as iov_iter) need to support
+ *   multipage bvec, we introduce new helpers(mp_bvec_iter_*) for
+ *   them.
+ */
 
 /*
  * was unsigned short, but we might as well be ready for > 64kB I/O pages
@@ -52,16 +90,35 @@  struct bvec_iter {
  */
 #define __bvec_iter_bvec(bvec, iter)	(&(bvec)[(iter).bi_idx])
 
-#define bvec_iter_page(bvec, iter)				\
+#define mp_bvec_iter_page(bvec, iter)				\
 	(__bvec_iter_bvec((bvec), (iter))->bv_page)
 
-#define bvec_iter_len(bvec, iter)				\
+#define mp_bvec_iter_len(bvec, iter)				\
 	min((iter).bi_size,					\
 	    __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
 
-#define bvec_iter_offset(bvec, iter)				\
+#define mp_bvec_iter_offset(bvec, iter)				\
 	(__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
 
+#define mp_bvec_iter_page_idx(bvec, iter)			\
+	(mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
+
+/*
+ * <page, offset,length> of singlepage(sp) segment.
+ *
+ * This helpers are for building sp bvec in flight.
+ */
+#define bvec_iter_offset(bvec, iter)					\
+	(mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
+
+#define bvec_iter_len(bvec, iter)					\
+	min_t(unsigned, mp_bvec_iter_len((bvec), (iter)),		\
+	    (PAGE_SIZE - (bvec_iter_offset((bvec), (iter)))))
+
+#define bvec_iter_page(bvec, iter)					\
+	nth_page(mp_bvec_iter_page((bvec), (iter)),		\
+		 mp_bvec_iter_page_idx((bvec), (iter)))
+
 #define bvec_iter_bvec(bvec, iter)				\
 ((struct bio_vec) {						\
 	.bv_page	= bvec_iter_page((bvec), (iter)),	\