[PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Ming Lei]

Commit 6dc4f100c175 ("block: allow bio_for_each_segment_all() to
iterate over multi-page bvec") changes bio_for_each_segment_all()
to use for-inside-for.

This way breaks all bio_for_each_segment_all() call with error out
branch via 'break', since now 'break' can only break from the inner
loop.

Fixes this issue by implementing bio_for_each_segment_all() via
single 'for' loop, and now the logic is very similar with normal
bvec iterator.

Cc: Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc: linux-btrfs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: Omar Sandoval <osandov@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Reported-and-Tested-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
Fixes: 6dc4f100c175 ("block: allow bio_for_each_segment_all() to iterate over multi-page bvec")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/bio.h  | 14 +++++---------
 include/linux/bvec.h | 20 +++++++++++++-------
 2 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index bb6090aa165d..7bd7e64e02f8 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -120,19 +120,15 @@ static inline bool bio_full(struct bio *bio)
 	return bio->bi_vcnt >= bio->bi_max_vecs;
 }
 
-#define mp_bvec_for_each_segment(bv, bvl, i, iter_all)			\
-	for (bv = bvec_init_iter_all(&iter_all);			\
-		(iter_all.done < (bvl)->bv_len) &&			\
-		(mp_bvec_next_segment((bvl), &iter_all), 1);		\
-		iter_all.done += bv->bv_len, i += 1)
-
 /*
  * drivers should _never_ use the all version - the bio may have been split
  * before it got to the driver and the driver won't own all of it
  */
-#define bio_for_each_segment_all(bvl, bio, i, iter_all)		\
-	for (i = 0, iter_all.idx = 0; iter_all.idx < (bio)->bi_vcnt; iter_all.idx++)	\
-		mp_bvec_for_each_segment(bvl, &((bio)->bi_io_vec[iter_all.idx]), i, iter_all)
+#define bio_for_each_segment_all(bvl, bio, i, iter_all)			\
+	for (i = 0, bvl = bvec_init_iter_all(&iter_all);		\
+		iter_all.idx < (bio)->bi_vcnt &&			\
+		(mp_bvec_advance(&((bio)->bi_io_vec[iter_all.idx]),	\
+				 &iter_all), 1); i++)
 
 static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
 				    unsigned bytes)
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index f6275c4da13a..6e4996dfc847 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -48,7 +48,7 @@ struct bvec_iter {
 struct bvec_iter_all {
 	struct bio_vec	bv;
 	int		idx;
-	unsigned	done;
+	unsigned	bv_done;
 };
 
 static inline struct page *bvec_nth_page(struct page *page, int idx)
@@ -145,18 +145,18 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
 
 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
 {
-	iter_all->bv.bv_page = NULL;
-	iter_all->done = 0;
+	iter_all->bv_done = 0;
+	iter_all->idx = 0;
 
 	return &iter_all->bv;
 }
 
-static inline void mp_bvec_next_segment(const struct bio_vec *bvec,
-					struct bvec_iter_all *iter_all)
+static inline void mp_bvec_advance(const struct bio_vec *bvec,
+				   struct bvec_iter_all *iter_all)
 {
 	struct bio_vec *bv = &iter_all->bv;
 
-	if (bv->bv_page) {
+	if (iter_all->bv_done) {
 		bv->bv_page = nth_page(bv->bv_page, 1);
 		bv->bv_offset = 0;
 	} else {
@@ -164,7 +164,13 @@ static inline void mp_bvec_next_segment(const struct bio_vec *bvec,
 		bv->bv_offset = bvec->bv_offset;
 	}
 	bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
-			   bvec->bv_len - iter_all->done);
+			   bvec->bv_len - iter_all->bv_done);
+	iter_all->bv_done += bv->bv_len;
+
+	if (iter_all->bv_done == bvec->bv_len) {
+		iter_all->idx++;
+		iter_all->bv_done = 0;
+	}
 }
 
 /*
-- 
2.9.5

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Christoph Hellwig]

The change itself looks fine to be, but a few comments on semingly
unrelated changes:

> +#define bio_for_each_segment_all(bvl, bio, i, iter_all)			\
> +	for (i = 0, bvl = bvec_init_iter_all(&iter_all);		\
> +		iter_all.idx < (bio)->bi_vcnt &&			\
> +		(mp_bvec_advance(&((bio)->bi_io_vec[iter_all.idx]),	\
> +				 &iter_all), 1); i++)

Instead of the complicated expression inside the for loop test
expression can't we move the index check into mp_bvec_advance and let
it return a bool?

> diff --git a/include/linux/bvec.h b/include/linux/bvec.h
> index f6275c4da13a..6e4996dfc847 100644
> --- a/include/linux/bvec.h
> +++ b/include/linux/bvec.h
> @@ -48,7 +48,7 @@ struct bvec_iter {
>  struct bvec_iter_all {
>  	struct bio_vec	bv;
>  	int		idx;
> -	unsigned	done;
> +	unsigned	bv_done;

Why the rename here?

> +static inline void mp_bvec_advance(const struct bio_vec *bvec,
> +				   struct bvec_iter_all *iter_all)

If we rename this we should probably drop the mp_ prefix..

Also not for this patch, but we should really consider moving this
function out of line given how big it is.


Here is how I'd do this with my slight changes:


diff --git a/include/linux/bio.h b/include/linux/bio.h
index bb915591557b..fd7629ac9f11 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -120,19 +120,42 @@ static inline bool bio_full(struct bio *bio)
 	return bio->bi_vcnt >= bio->bi_max_vecs;
 }
 
-#define mp_bvec_for_each_segment(bv, bvl, i, iter_all)			\
-	for (bv = bvec_init_iter_all(&iter_all);			\
-		(iter_all.done < (bvl)->bv_len) &&			\
-		(mp_bvec_next_segment((bvl), &iter_all), 1);		\
-		iter_all.done += bv->bv_len, i += 1)
+static inline bool __bio_next_segment_all(struct bio *bio,
+		struct bvec_iter_all *iter_all)
+{
+	struct bio_vec *bvec = &bio->bi_io_vec[iter_all->idx];
+	struct bio_vec *bv = &iter_all->bv;
+
+	if (iter_all->idx >= bio->bi_vcnt)
+		return false;
+
+	if (iter_all->done) {
+		bv->bv_page = nth_page(bv->bv_page, 1);
+		bv->bv_offset = 0;
+	} else {
+		bv->bv_page = bvec->bv_page;
+		bv->bv_offset = bvec->bv_offset;
+	}
+	bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
+			   bvec->bv_len - iter_all->done);
+	iter_all->done += bv->bv_len;
+
+	if (iter_all->done == bvec->bv_len) {
+		iter_all->idx++;
+		iter_all->done = 0;
+	}
+
+	return true;
+}
 
 /*
  * drivers should _never_ use the all version - the bio may have been split
  * before it got to the driver and the driver won't own all of it
  */
-#define bio_for_each_segment_all(bvl, bio, i, iter_all)		\
-	for (i = 0, iter_all.idx = 0; iter_all.idx < (bio)->bi_vcnt; iter_all.idx++)	\
-		mp_bvec_for_each_segment(bvl, &((bio)->bi_io_vec[iter_all.idx]), i, iter_all)
+#define bio_for_each_segment_all(bvl, bio, i, iter_all)			\
+	for (i = 0, bvl = bvec_init_iter_all(&iter_all);		\
+	     __bio_next_segment_all(bio, &iter_all);			\
+	     i++)
 
 static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
 				    unsigned bytes)
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index f6275c4da13a..bcebfc522498 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -145,28 +145,12 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
 
 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
 {
-	iter_all->bv.bv_page = NULL;
 	iter_all->done = 0;
+	iter_all->idx = 0;
 
 	return &iter_all->bv;
 }
 
-static inline void mp_bvec_next_segment(const struct bio_vec *bvec,
-					struct bvec_iter_all *iter_all)
-{
-	struct bio_vec *bv = &iter_all->bv;
-
-	if (bv->bv_page) {
-		bv->bv_page = nth_page(bv->bv_page, 1);
-		bv->bv_offset = 0;
-	} else {
-		bv->bv_page = bvec->bv_page;
-		bv->bv_offset = bvec->bv_offset;
-	}
-	bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
-			   bvec->bv_len - iter_all->done);
-}
-
 /*
  * Get the last single-page segment from the multi-page bvec and store it
  * in @seg

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Ming Lei]

On Sun, Apr 7, 2019 at 2:53 PM Christoph Hellwig <hch@lst.de> wrote:
>
> The change itself looks fine to be, but a few comments on semingly
> unrelated changes:
>
> > +#define bio_for_each_segment_all(bvl, bio, i, iter_all)                      \
> > +     for (i = 0, bvl = bvec_init_iter_all(&iter_all);                \
> > +             iter_all.idx < (bio)->bi_vcnt &&                        \
> > +             (mp_bvec_advance(&((bio)->bi_io_vec[iter_all.idx]),     \
> > +                              &iter_all), 1); i++)
>
> Instead of the complicated expression inside the for loop test
> expression can't we move the index check into mp_bvec_advance and let
> it return a bool?

OK, will move index check into mp_bvec_advance.

>
> > diff --git a/include/linux/bvec.h b/include/linux/bvec.h
> > index f6275c4da13a..6e4996dfc847 100644
> > --- a/include/linux/bvec.h
> > +++ b/include/linux/bvec.h
> > @@ -48,7 +48,7 @@ struct bvec_iter {
> >  struct bvec_iter_all {
> >       struct bio_vec  bv;
> >       int             idx;
> > -     unsigned        done;
> > +     unsigned        bv_done;
>
> Why the rename here?

'done' may be a bit misleading given we know this field is for recording how
many bytes we have done on the current bvec. Or .bvec_done?

>
> > +static inline void mp_bvec_advance(const struct bio_vec *bvec,
> > +                                struct bvec_iter_all *iter_all)
>
> If we rename this we should probably drop the mp_ prefix..

OK.

>
> Also not for this patch, but we should really consider moving this
> function out of line given how big it is.

It  is fine for me, but I think they shouldn't belong to this fix.


Thanks,
Ming Lei

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Christoph Hellwig]

On Sun, Apr 07, 2019 at 03:37:00PM +0800, Ming Lei wrote:
> > > @@ -48,7 +48,7 @@ struct bvec_iter {
> > >  struct bvec_iter_all {
> > >       struct bio_vec  bv;
> > >       int             idx;
> > > -     unsigned        done;
> > > +     unsigned        bv_done;
> >
> > Why the rename here?
> 
> 'done' may be a bit misleading given we know this field is for recording how
> many bytes we have done on the current bvec. Or .bvec_done?

I doubt add a comment..

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Ming Lei]

On Sun, Apr 7, 2019 at 3:37 PM Ming Lei <tom.leiming@gmail.com> wrote:
>
> On Sun, Apr 7, 2019 at 2:53 PM Christoph Hellwig <hch@lst.de> wrote:
> >
> > The change itself looks fine to be, but a few comments on semingly
> > unrelated changes:
> >
> > > +#define bio_for_each_segment_all(bvl, bio, i, iter_all)                      \
> > > +     for (i = 0, bvl = bvec_init_iter_all(&iter_all);                \
> > > +             iter_all.idx < (bio)->bi_vcnt &&                        \
> > > +             (mp_bvec_advance(&((bio)->bi_io_vec[iter_all.idx]),     \
> > > +                              &iter_all), 1); i++)
> >
> > Instead of the complicated expression inside the for loop test
> > expression can't we move the index check into mp_bvec_advance and let
> > it return a bool?
>
> OK, will move index check into mp_bvec_advance.

oops, I recall the above line, because:

1) the index check expression is quite straight-forward

2) it has been in my todo list to re-use bvec_advance() to re-write
iterate_bvec()
given bvec_advance() is much light-weight than for_each_bvec(). If we
move the index check into bvec_advance(), the helper has to be moved
to bio.h, then we can't use that for iterate_bvec().

thanks,
Ming Lei

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Christoph Hellwig]

On Sun, Apr 07, 2019 at 03:54:16PM +0800, Ming Lei wrote:
> > OK, will move index check into mp_bvec_advance.
> 
> oops, I recall the above line, because:
> 
> 1) the index check expression is quite straight-forward
> 
> 2) it has been in my todo list to re-use bvec_advance() to re-write
> iterate_bvec()
> given bvec_advance() is much light-weight than for_each_bvec(). If we
> move the index check into bvec_advance(), the helper has to be moved
> to bio.h, then we can't use that for iterate_bvec().

You can always create a tiny wrapper around bvec_advance() that sits
in bio.h.  Which in general is much better style than complex
expressions inside of loops inside of macros..

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Ming Lei]

On Sun, Apr 7, 2019 at 3:58 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Sun, Apr 07, 2019 at 03:54:16PM +0800, Ming Lei wrote:
> > > OK, will move index check into mp_bvec_advance.
> >
> > oops, I recall the above line, because:
> >
> > 1) the index check expression is quite straight-forward
> >
> > 2) it has been in my todo list to re-use bvec_advance() to re-write
> > iterate_bvec()
> > given bvec_advance() is much light-weight than for_each_bvec(). If we
> > move the index check into bvec_advance(), the helper has to be moved
> > to bio.h, then we can't use that for iterate_bvec().
>
> You can always create a tiny wrapper around bvec_advance() that sits
> in bio.h.  Which in general is much better style than complex
> expressions inside of loops inside of macros..

OK, fair enough.


Thanks,
Ming Lei

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Hannes Reinecke]

On 4/7/19 8:52 AM, Christoph Hellwig wrote:
> The change itself looks fine to be, but a few comments on semingly
> unrelated changes:
> 
>> +#define bio_for_each_segment_all(bvl, bio, i, iter_all)			\
>> +	for (i = 0, bvl = bvec_init_iter_all(&iter_all);		\
>> +		iter_all.idx < (bio)->bi_vcnt &&			\
>> +		(mp_bvec_advance(&((bio)->bi_io_vec[iter_all.idx]),	\
>> +				 &iter_all), 1); i++)
> 
> Instead of the complicated expression inside the for loop test
> expression can't we move the index check into mp_bvec_advance and let
> it return a bool?
> 
>> diff --git a/include/linux/bvec.h b/include/linux/bvec.h
>> index f6275c4da13a..6e4996dfc847 100644
>> --- a/include/linux/bvec.h
>> +++ b/include/linux/bvec.h
>> @@ -48,7 +48,7 @@ struct bvec_iter {
>>   struct bvec_iter_all {
>>   	struct bio_vec	bv;
>>   	int		idx;
>> -	unsigned	done;
>> +	unsigned	bv_done;
> 
> Why the rename here?
> 
>> +static inline void mp_bvec_advance(const struct bio_vec *bvec,
>> +				   struct bvec_iter_all *iter_all)
> 
> If we rename this we should probably drop the mp_ prefix..
> 
> Also not for this patch, but we should really consider moving this
> function out of line given how big it is.
> 
> 
> Here is how I'd do this with my slight changes:
> 
> 
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index bb915591557b..fd7629ac9f11 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -120,19 +120,42 @@ static inline bool bio_full(struct bio *bio)
>   	return bio->bi_vcnt >= bio->bi_max_vecs;
>   }
>   
> -#define mp_bvec_for_each_segment(bv, bvl, i, iter_all)			\
> -	for (bv = bvec_init_iter_all(&iter_all);			\
> -		(iter_all.done < (bvl)->bv_len) &&			\
> -		(mp_bvec_next_segment((bvl), &iter_all), 1);		\
> -		iter_all.done += bv->bv_len, i += 1)
> +static inline bool __bio_next_segment_all(struct bio *bio,
> +		struct bvec_iter_all *iter_all)
> +{
> +	struct bio_vec *bvec = &bio->bi_io_vec[iter_all->idx];
> +	struct bio_vec *bv = &iter_all->bv;
> +
> +	if (iter_all->idx >= bio->bi_vcnt)
> +		return false;
> +
> +	if (iter_all->done) {
> +		bv->bv_page = nth_page(bv->bv_page, 1);
> +		bv->bv_offset = 0;
> +	} else {
> +		bv->bv_page = bvec->bv_page;
> +		bv->bv_offset = bvec->bv_offset;
> +	}
> +	bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
> +			   bvec->bv_len - iter_all->done);
> +	iter_all->done += bv->bv_len;
> +
> +	if (iter_all->done == bvec->bv_len) {
> +		iter_all->idx++;
> +		iter_all->done = 0;
> +	}
> +
> +	return true;
> +}
>   
>   /*
>    * drivers should _never_ use the all version - the bio may have been split
>    * before it got to the driver and the driver won't own all of it
>    */
> -#define bio_for_each_segment_all(bvl, bio, i, iter_all)		\
> -	for (i = 0, iter_all.idx = 0; iter_all.idx < (bio)->bi_vcnt; iter_all.idx++)	\
> -		mp_bvec_for_each_segment(bvl, &((bio)->bi_io_vec[iter_all.idx]), i, iter_all)
> +#define bio_for_each_segment_all(bvl, bio, i, iter_all)			\
> +	for (i = 0, bvl = bvec_init_iter_all(&iter_all);		\
> +	     __bio_next_segment_all(bio, &iter_all);			\
> +	     i++)
>   
>   static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
>   				    unsigned bytes)
> diff --git a/include/linux/bvec.h b/include/linux/bvec.h
> index f6275c4da13a..bcebfc522498 100644
> --- a/include/linux/bvec.h
> +++ b/include/linux/bvec.h
> @@ -145,28 +145,12 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
>   
>   static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
>   {
> -	iter_all->bv.bv_page = NULL;
>   	iter_all->done = 0;
> +	iter_all->idx = 0;
>   
>   	return &iter_all->bv;
>   }
>   
> -static inline void mp_bvec_next_segment(const struct bio_vec *bvec,
> -					struct bvec_iter_all *iter_all)
> -{
> -	struct bio_vec *bv = &iter_all->bv;
> -
> -	if (bv->bv_page) {
> -		bv->bv_page = nth_page(bv->bv_page, 1);
> -		bv->bv_offset = 0;
> -	} else {
> -		bv->bv_page = bvec->bv_page;
> -		bv->bv_offset = bvec->bv_offset;
> -	}
> -	bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
> -			   bvec->bv_len - iter_all->done);
> -}
> -
>   /*
>    * Get the last single-page segment from the multi-page bvec and store it
>    * in @seg
> 
Oh yes, please do.
The macros are fast becoming unparseable :-)

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Matthew Wilcox]

On Mon, Apr 08, 2019 at 08:07:55AM +0200, Hannes Reinecke wrote:
> Oh yes, please do.
> The macros are fast becoming unparseable :-)

I think something that would help is removing the mandatory 'i' parameter
to this iterator.  Most of the users don't use it, and the ones that do
can implement it themselves.  eg:


                int j;
                struct bio_vec *bv;
                void *base = (void *) ((unsigned long) i & ~(PAGE_SIZE - 1));
                struct bvec_iter_all iter_all;

                bio_for_each_segment_all(bv, b->bio, j, iter_all)
                        memcpy(page_address(bv->bv_page),
                               base + j * PAGE_SIZE, PAGE_SIZE);

could become

                struct bio_vec *bv;
                void *addr = (void *) ((unsigned long) i & ~(PAGE_SIZE - 1));
                struct bvec_iter_all iter_all;

                bio_for_each_segment_all(bv, b->bio, iter_all) {
                        memcpy(page_address(bv->bv_page), addr, PAGE_SIZE);
			addr += PAGE_SIZE;
		}

eg2:

                bio_for_each_segment_all(bi, sbio, j, iter_all)
                        page_len[j] = bi->bv_len;

could become:
                bio_for_each_segment_all(bi, sbio, iter_all)
                        page_len[j++] = bi->bv_len;

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Christoph Hellwig]

On Mon, Apr 08, 2019 at 07:12:04AM -0700, Matthew Wilcox wrote:
> On Mon, Apr 08, 2019 at 08:07:55AM +0200, Hannes Reinecke wrote:
> > Oh yes, please do.
> > The macros are fast becoming unparseable :-)
> 
> I think something that would help is removing the mandatory 'i' parameter
> to this iterator.  Most of the users don't use it, and the ones that do
> can implement it themselves.  eg:

Yeah, I quickly hacked this up during a meeting yesterday and we have
exactly two users of the iterator.  Patch against the for-linus tree
below, although it conflicts with some of the 5.2 work.  Maybe it is
best to merge this just after the next rc1..

--
From 6a872f0186846a64a898b149be54d385f9f03f8b Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Mon, 8 Apr 2019 18:11:44 +0200
Subject: block: remove the i argument to bio_for_each_segment_all

We only have two callers that need the simple loop iterator, and
they can easily do it themselves.

Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/bio.c                       | 26 +++++++++-----------------
 block/bounce.c                    |  3 +--
 drivers/md/bcache/btree.c         |  6 ++++--
 drivers/md/dm-crypt.c             |  3 +--
 drivers/md/raid1.c                |  6 +++---
 drivers/staging/erofs/data.c      |  3 +--
 drivers/staging/erofs/unzip_vle.c |  3 +--
 fs/block_dev.c                    |  6 ++----
 fs/btrfs/compression.c            |  3 +--
 fs/btrfs/disk-io.c                |  4 ++--
 fs/btrfs/extent_io.c              | 10 ++++------
 fs/btrfs/inode.c                  |  8 ++++----
 fs/btrfs/raid56.c                 |  3 +--
 fs/crypto/bio.c                   |  3 +--
 fs/direct-io.c                    |  3 +--
 fs/ext4/page-io.c                 |  3 +--
 fs/ext4/readpage.c                |  3 +--
 fs/f2fs/data.c                    |  9 +++------
 fs/gfs2/lops.c                    |  3 +--
 fs/gfs2/meta_io.c                 |  3 +--
 fs/iomap.c                        |  6 ++----
 fs/mpage.c                        |  3 +--
 fs/xfs/xfs_aops.c                 |  3 +--
 include/linux/bio.h               |  5 ++---
 24 files changed, 49 insertions(+), 79 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index b64cedc7f87c..8620ba0487e2 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1127,11 +1127,10 @@ static struct bio_map_data *bio_alloc_map_data(struct iov_iter *data,
  */
 static int bio_copy_from_iter(struct bio *bio, struct iov_iter *iter)
 {
-	int i;
 	struct bio_vec *bvec;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		ssize_t ret;
 
 		ret = copy_page_from_iter(bvec->bv_page,
@@ -1159,11 +1158,10 @@ static int bio_copy_from_iter(struct bio *bio, struct iov_iter *iter)
  */
 static int bio_copy_to_iter(struct bio *bio, struct iov_iter iter)
 {
-	int i;
 	struct bio_vec *bvec;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		ssize_t ret;
 
 		ret = copy_page_to_iter(bvec->bv_page,
@@ -1184,10 +1182,9 @@ static int bio_copy_to_iter(struct bio *bio, struct iov_iter iter)
 void bio_free_pages(struct bio *bio)
 {
 	struct bio_vec *bvec;
-	int i;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all)
+	bio_for_each_segment_all(bvec, bio, iter_all)
 		__free_page(bvec->bv_page);
 }
 EXPORT_SYMBOL(bio_free_pages);
@@ -1429,7 +1426,7 @@ struct bio *bio_map_user_iov(struct request_queue *q,
 	return bio;
 
  out_unmap:
-	bio_for_each_segment_all(bvec, bio, j, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		put_page(bvec->bv_page);
 	}
 	bio_put(bio);
@@ -1439,13 +1436,12 @@ struct bio *bio_map_user_iov(struct request_queue *q,
 static void __bio_unmap_user(struct bio *bio)
 {
 	struct bio_vec *bvec;
-	int i;
 	struct bvec_iter_all iter_all;
 
 	/*
 	 * make sure we dirty pages we wrote to
 	 */
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		if (bio_data_dir(bio) == READ)
 			set_page_dirty_lock(bvec->bv_page);
 
@@ -1536,10 +1532,9 @@ static void bio_copy_kern_endio_read(struct bio *bio)
 {
 	char *p = bio->bi_private;
 	struct bio_vec *bvec;
-	int i;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		memcpy(p, page_address(bvec->bv_page), bvec->bv_len);
 		p += bvec->bv_len;
 	}
@@ -1647,10 +1642,9 @@ struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
 void bio_set_pages_dirty(struct bio *bio)
 {
 	struct bio_vec *bvec;
-	int i;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		if (!PageCompound(bvec->bv_page))
 			set_page_dirty_lock(bvec->bv_page);
 	}
@@ -1659,10 +1653,9 @@ void bio_set_pages_dirty(struct bio *bio)
 static void bio_release_pages(struct bio *bio)
 {
 	struct bio_vec *bvec;
-	int i;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all)
+	bio_for_each_segment_all(bvec, bio, iter_all)
 		put_page(bvec->bv_page);
 }
 
@@ -1709,10 +1702,9 @@ void bio_check_pages_dirty(struct bio *bio)
 {
 	struct bio_vec *bvec;
 	unsigned long flags;
-	int i;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		if (!PageDirty(bvec->bv_page) && !PageCompound(bvec->bv_page))
 			goto defer;
 	}
diff --git a/block/bounce.c b/block/bounce.c
index 47eb7e936e22..f8ed677a1bf7 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -163,14 +163,13 @@ static void bounce_end_io(struct bio *bio, mempool_t *pool)
 {
 	struct bio *bio_orig = bio->bi_private;
 	struct bio_vec *bvec, orig_vec;
-	int i;
 	struct bvec_iter orig_iter = bio_orig->bi_iter;
 	struct bvec_iter_all iter_all;
 
 	/*
 	 * free up bounce indirect pages used
 	 */
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		orig_vec = bio_iter_iovec(bio_orig, orig_iter);
 		if (bvec->bv_page != orig_vec.bv_page) {
 			dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 64def336f053..aa793fef52eb 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -429,14 +429,16 @@ static void do_btree_node_write(struct btree *b)
 		       bset_sector_offset(&b->keys, i));
 
 	if (!bch_bio_alloc_pages(b->bio, __GFP_NOWARN|GFP_NOWAIT)) {
-		int j;
+		int j = 0;
 		struct bio_vec *bv;
 		void *base = (void *) ((unsigned long) i & ~(PAGE_SIZE - 1));
 		struct bvec_iter_all iter_all;
 
-		bio_for_each_segment_all(bv, b->bio, j, iter_all)
+		bio_for_each_segment_all(bv, b->bio, iter_all) {
 			memcpy(page_address(bv->bv_page),
 			       base + j * PAGE_SIZE, PAGE_SIZE);
+			j++;
+		}
 
 		bch_submit_bbio(b->bio, b->c, &k.key, 0);
 
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index dd6565798778..cca68546945b 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1445,11 +1445,10 @@ static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned size)
 
 static void crypt_free_buffer_pages(struct crypt_config *cc, struct bio *clone)
 {
-	unsigned int i;
 	struct bio_vec *bv;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bv, clone, i, iter_all) {
+	bio_for_each_segment_all(bv, clone, iter_all) {
 		BUG_ON(!bv->bv_page);
 		mempool_free(bv->bv_page, &cc->page_pool);
 	}
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index fdf451aac369..0c8a098d220e 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -2110,7 +2110,7 @@ static void process_checks(struct r1bio *r1_bio)
 		}
 	r1_bio->read_disk = primary;
 	for (i = 0; i < conf->raid_disks * 2; i++) {
-		int j;
+		int j = 0;
 		struct bio *pbio = r1_bio->bios[primary];
 		struct bio *sbio = r1_bio->bios[i];
 		blk_status_t status = sbio->bi_status;
@@ -2125,8 +2125,8 @@ static void process_checks(struct r1bio *r1_bio)
 		/* Now we can 'fixup' the error value */
 		sbio->bi_status = 0;
 
-		bio_for_each_segment_all(bi, sbio, j, iter_all)
-			page_len[j] = bi->bv_len;
+		bio_for_each_segment_all(bi, sbio, iter_all)
+			page_len[j++] = bi->bv_len;
 
 		if (!status) {
 			for (j = vcnt; j-- ; ) {
diff --git a/drivers/staging/erofs/data.c b/drivers/staging/erofs/data.c
index 526e0dbea5b5..1116bb630f2a 100644
--- a/drivers/staging/erofs/data.c
+++ b/drivers/staging/erofs/data.c
@@ -17,12 +17,11 @@
 
 static inline void read_endio(struct bio *bio)
 {
-	int i;
 	struct bio_vec *bvec;
 	const blk_status_t err = bio->bi_status;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		struct page *page = bvec->bv_page;
 
 		/* page is already locked */
diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index 31eef8395774..59b9f37d5c00 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -844,14 +844,13 @@ static void z_erofs_vle_unzip_kickoff(void *ptr, int bios)
 static inline void z_erofs_vle_read_endio(struct bio *bio)
 {
 	const blk_status_t err = bio->bi_status;
-	unsigned int i;
 	struct bio_vec *bvec;
 #ifdef EROFS_FS_HAS_MANAGED_CACHE
 	struct address_space *mc = NULL;
 #endif
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		struct page *page = bvec->bv_page;
 		bool cachemngd = false;
 
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 78d3257435c0..2bddc2339ab1 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -210,7 +210,6 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 	struct bio bio;
 	ssize_t ret;
 	blk_qc_t qc;
-	int i;
 	struct bvec_iter_all iter_all;
 
 	if ((pos | iov_iter_alignment(iter)) &
@@ -261,7 +260,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 	}
 	__set_current_state(TASK_RUNNING);
 
-	bio_for_each_segment_all(bvec, &bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, &bio, iter_all) {
 		if (should_dirty && !PageCompound(bvec->bv_page))
 			set_page_dirty_lock(bvec->bv_page);
 		put_page(bvec->bv_page);
@@ -339,9 +338,8 @@ static void blkdev_bio_end_io(struct bio *bio)
 		if (!bio_flagged(bio, BIO_NO_PAGE_REF)) {
 			struct bvec_iter_all iter_all;
 			struct bio_vec *bvec;
-			int i;
 
-			bio_for_each_segment_all(bvec, bio, i, iter_all)
+			bio_for_each_segment_all(bvec, bio, iter_all)
 				put_page(bvec->bv_page);
 		}
 		bio_put(bio);
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 4f2a8ae0aa42..6313dc65209e 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -160,7 +160,6 @@ static void end_compressed_bio_read(struct bio *bio)
 	if (cb->errors) {
 		bio_io_error(cb->orig_bio);
 	} else {
-		int i;
 		struct bio_vec *bvec;
 		struct bvec_iter_all iter_all;
 
@@ -169,7 +168,7 @@ static void end_compressed_bio_read(struct bio *bio)
 		 * checked so the end_io handlers know about it
 		 */
 		ASSERT(!bio_flagged(bio, BIO_CLONED));
-		bio_for_each_segment_all(bvec, cb->orig_bio, i, iter_all)
+		bio_for_each_segment_all(bvec, cb->orig_bio, iter_all)
 			SetPageChecked(bvec->bv_page);
 
 		bio_endio(cb->orig_bio);
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 6fe9197f6ee4..c333e79408ff 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -832,11 +832,11 @@ static blk_status_t btree_csum_one_bio(struct bio *bio)
 {
 	struct bio_vec *bvec;
 	struct btrfs_root *root;
-	int i, ret = 0;
+	int ret = 0;
 	struct bvec_iter_all iter_all;
 
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		root = BTRFS_I(bvec->bv_page->mapping->host)->root;
 		ret = csum_dirty_buffer(root->fs_info, bvec->bv_page);
 		if (ret)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index ca8b8e785cf3..c85505c36fa6 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2451,11 +2451,10 @@ static void end_bio_extent_writepage(struct bio *bio)
 	struct bio_vec *bvec;
 	u64 start;
 	u64 end;
-	int i;
 	struct bvec_iter_all iter_all;
 
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		struct page *page = bvec->bv_page;
 		struct inode *inode = page->mapping->host;
 		struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
@@ -2523,11 +2522,10 @@ static void end_bio_extent_readpage(struct bio *bio)
 	u64 extent_len = 0;
 	int mirror;
 	int ret;
-	int i;
 	struct bvec_iter_all iter_all;
 
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		struct page *page = bvec->bv_page;
 		struct inode *inode = page->mapping->host;
 		struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
@@ -3643,11 +3641,11 @@ static void end_bio_extent_buffer_writepage(struct bio *bio)
 {
 	struct bio_vec *bvec;
 	struct extent_buffer *eb;
-	int i, done;
+	int done;
 	struct bvec_iter_all iter_all;
 
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		struct page *page = bvec->bv_page;
 
 		eb = (struct extent_buffer *)page->private;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 82fdda8ff5ab..10a8d08d3d29 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7828,7 +7828,6 @@ static void btrfs_retry_endio_nocsum(struct bio *bio)
 	struct inode *inode = done->inode;
 	struct bio_vec *bvec;
 	struct extent_io_tree *io_tree, *failure_tree;
-	int i;
 	struct bvec_iter_all iter_all;
 
 	if (bio->bi_status)
@@ -7841,7 +7840,7 @@ static void btrfs_retry_endio_nocsum(struct bio *bio)
 
 	done->uptodate = 1;
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
-	bio_for_each_segment_all(bvec, bio, i, iter_all)
+	bio_for_each_segment_all(bvec, bio, iter_all)
 		clean_io_failure(BTRFS_I(inode)->root->fs_info, failure_tree,
 				 io_tree, done->start, bvec->bv_page,
 				 btrfs_ino(BTRFS_I(inode)), 0);
@@ -7919,7 +7918,7 @@ static void btrfs_retry_endio(struct bio *bio)
 	struct bio_vec *bvec;
 	int uptodate;
 	int ret;
-	int i;
+	int i = 0;
 	struct bvec_iter_all iter_all;
 
 	if (bio->bi_status)
@@ -7934,7 +7933,7 @@ static void btrfs_retry_endio(struct bio *bio)
 	failure_tree = &BTRFS_I(inode)->io_failure_tree;
 
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		ret = __readpage_endio_check(inode, io_bio, i, bvec->bv_page,
 					     bvec->bv_offset, done->start,
 					     bvec->bv_len);
@@ -7946,6 +7945,7 @@ static void btrfs_retry_endio(struct bio *bio)
 					 bvec->bv_offset);
 		else
 			uptodate = 0;
+		i++;
 	}
 
 	done->uptodate = uptodate;
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 67a6f7d47402..f3d0576dd327 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -1442,12 +1442,11 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
 static void set_bio_pages_uptodate(struct bio *bio)
 {
 	struct bio_vec *bvec;
-	int i;
 	struct bvec_iter_all iter_all;
 
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all)
+	bio_for_each_segment_all(bvec, bio, iter_all)
 		SetPageUptodate(bvec->bv_page);
 }
 
diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
index 5759bcd018cd..8f3a8bc15d98 100644
--- a/fs/crypto/bio.c
+++ b/fs/crypto/bio.c
@@ -29,10 +29,9 @@
 static void __fscrypt_decrypt_bio(struct bio *bio, bool done)
 {
 	struct bio_vec *bv;
-	int i;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bv, bio, i, iter_all) {
+	bio_for_each_segment_all(bv, bio, iter_all) {
 		struct page *page = bv->bv_page;
 		int ret = fscrypt_decrypt_page(page->mapping->host, page,
 				PAGE_SIZE, 0, page->index);
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 9bb015bc4a83..fbe885d68035 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -538,7 +538,6 @@ static struct bio *dio_await_one(struct dio *dio)
 static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio)
 {
 	struct bio_vec *bvec;
-	unsigned i;
 	blk_status_t err = bio->bi_status;
 
 	if (err) {
@@ -553,7 +552,7 @@ static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio)
 	} else {
 		struct bvec_iter_all iter_all;
 
-		bio_for_each_segment_all(bvec, bio, i, iter_all) {
+		bio_for_each_segment_all(bvec, bio, iter_all) {
 			struct page *page = bvec->bv_page;
 
 			if (dio->op == REQ_OP_READ && !PageCompound(page) &&
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 3e9298e6a705..4690618a92e9 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -61,11 +61,10 @@ static void buffer_io_error(struct buffer_head *bh)
 
 static void ext4_finish_bio(struct bio *bio)
 {
-	int i;
 	struct bio_vec *bvec;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		struct page *page = bvec->bv_page;
 #ifdef CONFIG_FS_ENCRYPTION
 		struct page *data_page = NULL;
diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index 3adadf461825..3629a74b7f94 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -71,7 +71,6 @@ static inline bool ext4_bio_encrypted(struct bio *bio)
 static void mpage_end_io(struct bio *bio)
 {
 	struct bio_vec *bv;
-	int i;
 	struct bvec_iter_all iter_all;
 
 	if (ext4_bio_encrypted(bio)) {
@@ -82,7 +81,7 @@ static void mpage_end_io(struct bio *bio)
 			return;
 		}
 	}
-	bio_for_each_segment_all(bv, bio, i, iter_all) {
+	bio_for_each_segment_all(bv, bio, iter_all) {
 		struct page *page = bv->bv_page;
 
 		if (!bio->bi_status) {
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 9727944139f2..64040e998439 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -86,10 +86,9 @@ static void __read_end_io(struct bio *bio)
 {
 	struct page *page;
 	struct bio_vec *bv;
-	int i;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bv, bio, i, iter_all) {
+	bio_for_each_segment_all(bv, bio, iter_all) {
 		page = bv->bv_page;
 
 		/* PG_error was set if any post_read step failed */
@@ -164,7 +163,6 @@ static void f2fs_write_end_io(struct bio *bio)
 {
 	struct f2fs_sb_info *sbi = bio->bi_private;
 	struct bio_vec *bvec;
-	int i;
 	struct bvec_iter_all iter_all;
 
 	if (time_to_inject(sbi, FAULT_WRITE_IO)) {
@@ -172,7 +170,7 @@ static void f2fs_write_end_io(struct bio *bio)
 		bio->bi_status = BLK_STS_IOERR;
 	}
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		struct page *page = bvec->bv_page;
 		enum count_type type = WB_DATA_TYPE(page);
 
@@ -349,7 +347,6 @@ static bool __has_merged_page(struct f2fs_bio_info *io, struct inode *inode,
 {
 	struct bio_vec *bvec;
 	struct page *target;
-	int i;
 	struct bvec_iter_all iter_all;
 
 	if (!io->bio)
@@ -358,7 +355,7 @@ static bool __has_merged_page(struct f2fs_bio_info *io, struct inode *inode,
 	if (!inode && !page && !ino)
 		return true;
 
-	bio_for_each_segment_all(bvec, io->bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, io->bio, iter_all) {
 
 		if (bvec->bv_page->mapping)
 			target = bvec->bv_page;
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 8722c60b11fe..6f09b5e3dd6e 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -207,7 +207,6 @@ static void gfs2_end_log_write(struct bio *bio)
 	struct gfs2_sbd *sdp = bio->bi_private;
 	struct bio_vec *bvec;
 	struct page *page;
-	int i;
 	struct bvec_iter_all iter_all;
 
 	if (bio->bi_status) {
@@ -216,7 +215,7 @@ static void gfs2_end_log_write(struct bio *bio)
 		wake_up(&sdp->sd_logd_waitq);
 	}
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		page = bvec->bv_page;
 		if (page_has_buffers(page))
 			gfs2_end_log_write_bh(sdp, bvec, bio->bi_status);
diff --git a/fs/gfs2/meta_io.c b/fs/gfs2/meta_io.c
index 3201342404a7..ff86e1d4f8ff 100644
--- a/fs/gfs2/meta_io.c
+++ b/fs/gfs2/meta_io.c
@@ -189,10 +189,9 @@ struct buffer_head *gfs2_meta_new(struct gfs2_glock *gl, u64 blkno)
 static void gfs2_meta_read_endio(struct bio *bio)
 {
 	struct bio_vec *bvec;
-	int i;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all) {
+	bio_for_each_segment_all(bvec, bio, iter_all) {
 		struct page *page = bvec->bv_page;
 		struct buffer_head *bh = page_buffers(page);
 		unsigned int len = bvec->bv_len;
diff --git a/fs/iomap.c b/fs/iomap.c
index abdd18e404f8..12a656271076 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -273,10 +273,9 @@ iomap_read_end_io(struct bio *bio)
 {
 	int error = blk_status_to_errno(bio->bi_status);
 	struct bio_vec *bvec;
-	int i;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bvec, bio, i, iter_all)
+	bio_for_each_segment_all(bvec, bio, iter_all)
 		iomap_read_page_end_io(bvec, error);
 	bio_put(bio);
 }
@@ -1592,9 +1591,8 @@ static void iomap_dio_bio_end_io(struct bio *bio)
 		if (!bio_flagged(bio, BIO_NO_PAGE_REF)) {
 			struct bvec_iter_all iter_all;
 			struct bio_vec *bvec;
-			int i;
 
-			bio_for_each_segment_all(bvec, bio, i, iter_all)
+			bio_for_each_segment_all(bvec, bio, iter_all)
 				put_page(bvec->bv_page);
 		}
 		bio_put(bio);
diff --git a/fs/mpage.c b/fs/mpage.c
index 3f19da75178b..436a85260394 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -47,10 +47,9 @@
 static void mpage_end_io(struct bio *bio)
 {
 	struct bio_vec *bv;
-	int i;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bv, bio, i, iter_all) {
+	bio_for_each_segment_all(bv, bio, iter_all) {
 		struct page *page = bv->bv_page;
 		page_endio(page, bio_op(bio),
 			   blk_status_to_errno(bio->bi_status));
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 3619e9e8d359..47941bbaac02 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -98,7 +98,6 @@ xfs_destroy_ioend(
 
 	for (bio = &ioend->io_inline_bio; bio; bio = next) {
 		struct bio_vec	*bvec;
-		int		i;
 		struct bvec_iter_all iter_all;
 
 		/*
@@ -111,7 +110,7 @@ xfs_destroy_ioend(
 			next = bio->bi_private;
 
 		/* walk each page on bio, ending page IO on them */
-		bio_for_each_segment_all(bvec, bio, i, iter_all)
+		bio_for_each_segment_all(bvec, bio, iter_all)
 			xfs_finish_page_writeback(inode, bvec, error);
 		bio_put(bio);
 	}
diff --git a/include/linux/bio.h b/include/linux/bio.h
index e584673c1881..077cecdf9437 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -134,9 +134,8 @@ static inline bool bio_next_segment(const struct bio *bio,
  * drivers should _never_ use the all version - the bio may have been split
  * before it got to the driver and the driver won't own all of it
  */
-#define bio_for_each_segment_all(bvl, bio, i, iter)			\
-	for (i = 0, bvl = bvec_init_iter_all(&iter);			\
-	     bio_next_segment((bio), &iter); i++)
+#define bio_for_each_segment_all(bvl, bio, iter) \
+	for (bvl = bvec_init_iter_all(&iter); bio_next_segment((bio), &iter); )
 
 static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
 				    unsigned bytes)
-- 
2.20.1

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Johannes Thumshirn]

On Tue, Apr 09, 2019 at 11:48:39AM +0200, Christoph Hellwig wrote:
> On Mon, Apr 08, 2019 at 07:12:04AM -0700, Matthew Wilcox wrote:
> > On Mon, Apr 08, 2019 at 08:07:55AM +0200, Hannes Reinecke wrote:
> > > Oh yes, please do.
> > > The macros are fast becoming unparseable :-)
> > 
> > I think something that would help is removing the mandatory 'i' parameter
> > to this iterator.  Most of the users don't use it, and the ones that do
> > can implement it themselves.  eg:
> 
> Yeah, I quickly hacked this up during a meeting yesterday and we have
> exactly two users of the iterator.  Patch against the for-linus tree
> below, although it conflicts with some of the 5.2 work.  Maybe it is
> best to merge this just after the next rc1..
> 
> --
> From 6a872f0186846a64a898b149be54d385f9f03f8b Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch@lst.de>
> Date: Mon, 8 Apr 2019 18:11:44 +0200
> Subject: block: remove the i argument to bio_for_each_segment_all
> 
> We only have two callers that need the simple loop iterator, and
> they can easily do it themselves.
> 
> Suggested-by: Matthew Wilcox <willy@infradead.org>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Nice cleanup!

Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
-- 
Johannes Thumshirn                            SUSE Labs Filesystems
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[Matthew Wilcox]

On Tue, Apr 09, 2019 at 11:48:39AM +0200, Christoph Hellwig wrote:
> On Mon, Apr 08, 2019 at 07:12:04AM -0700, Matthew Wilcox wrote:
> > On Mon, Apr 08, 2019 at 08:07:55AM +0200, Hannes Reinecke wrote:
> > > Oh yes, please do.
> > > The macros are fast becoming unparseable :-)
> > 
> > I think something that would help is removing the mandatory 'i' parameter
> > to this iterator.  Most of the users don't use it, and the ones that do
> > can implement it themselves.  eg:
> 
> Yeah, I quickly hacked this up during a meeting yesterday and we have
> exactly two users of the iterator.  Patch against the for-linus tree

three in the below patch ...

> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
> index 64def336f053..aa793fef52eb 100644
> --- a/drivers/md/bcache/btree.c
> +++ b/drivers/md/bcache/btree.c
> @@ -429,14 +429,16 @@ static void do_btree_node_write(struct btree *b)
>  		       bset_sector_offset(&b->keys, i));
>  
>  	if (!bch_bio_alloc_pages(b->bio, __GFP_NOWARN|GFP_NOWAIT)) {
> -		int j;
> +		int j = 0;
>  		struct bio_vec *bv;
>  		void *base = (void *) ((unsigned long) i & ~(PAGE_SIZE - 1));
>  		struct bvec_iter_all iter_all;
>  
> -		bio_for_each_segment_all(bv, b->bio, j, iter_all)
> +		bio_for_each_segment_all(bv, b->bio, iter_all) {
>  			memcpy(page_address(bv->bv_page),
>  			       base + j * PAGE_SIZE, PAGE_SIZE);
> +			j++;
> +		}

I think this one works better to replace 'base' with 'addr':

@@ -429,14 +429,14 @@ static void do_btree_node_write(struct btree *b)
                       bset_sector_offset(&b->keys, i));
 
        if (!bch_bio_alloc_pages(b->bio, __GFP_NOWARN|GFP_NOWAIT)) {
-               int j;
                struct bio_vec *bv;
-               void *base = (void *) ((unsigned long) i & ~(PAGE_SIZE - 1));
+               void *addr = (void *) ((unsigned long) i & ~(PAGE_SIZE - 1));
                struct bvec_iter_all iter_all;
 
-               bio_for_each_segment_all(bv, b->bio, j, iter_all)
-                       memcpy(page_address(bv->bv_page),
-                              base + j * PAGE_SIZE, PAGE_SIZE);
+               bio_for_each_segment_all(bv, b->bio, iter_all) {
+                       memcpy(page_address(bv->bv_page), addr, PAGE_SIZE);
+                       addr += PAGE_SIZE;
+               }
 
                bch_submit_bbio(b->bio, b->c, &k.key, 0);
 
> +++ b/drivers/md/raid1.c
> @@ -2110,7 +2110,7 @@ static void process_checks(struct r1bio *r1_bio)
>  		}
>  	r1_bio->read_disk = primary;
>  	for (i = 0; i < conf->raid_disks * 2; i++) {
> -		int j;
> +		int j = 0;
>  		struct bio *pbio = r1_bio->bios[primary];
>  		struct bio *sbio = r1_bio->bios[i];
>  		blk_status_t status = sbio->bi_status;
> @@ -2125,8 +2125,8 @@ static void process_checks(struct r1bio *r1_bio)
>  		/* Now we can 'fixup' the error value */
>  		sbio->bi_status = 0;
>  
> -		bio_for_each_segment_all(bi, sbio, j, iter_all)
> -			page_len[j] = bi->bv_len;
> +		bio_for_each_segment_all(bi, sbio, iter_all)
> +			page_len[j++] = bi->bv_len;

Yes.

> +++ b/fs/btrfs/inode.c
> @@ -7919,7 +7918,7 @@ static void btrfs_retry_endio(struct bio *bio)
>  	struct bio_vec *bvec;
>  	int uptodate;
>  	int ret;
> -	int i;
> +	int i = 0;
>  	struct bvec_iter_all iter_all;
>  
>  	if (bio->bi_status)
> @@ -7934,7 +7933,7 @@ static void btrfs_retry_endio(struct bio *bio)
>  	failure_tree = &BTRFS_I(inode)->io_failure_tree;
>  
>  	ASSERT(!bio_flagged(bio, BIO_CLONED));
> -	bio_for_each_segment_all(bvec, bio, i, iter_all) {
> +	bio_for_each_segment_all(bvec, bio, iter_all) {
>  		ret = __readpage_endio_check(inode, io_bio, i, bvec->bv_page,
>  					     bvec->bv_offset, done->start,
>  					     bvec->bv_len);
> @@ -7946,6 +7945,7 @@ static void btrfs_retry_endio(struct bio *bio)
>  					 bvec->bv_offset);
>  		else
>  			uptodate = 0;
> +		i++;
>  	}

I'd be tempted to instead:

@@ -7935,7 +7935,7 @@ static void btrfs_retry_endio(struct bio *bio)
 
        ASSERT(!bio_flagged(bio, BIO_CLONED));
        bio_for_each_segment_all(bvec, bio, i, iter_all) {
-               ret = __readpage_endio_check(inode, io_bio, i, bvec->bv_page,
+               ret = __readpage_endio_check(inode, io_bio, i++, bvec->bv_page,
                                             bvec->bv_offset, done->start,
                                             bvec->bv_len);
                if (!ret)

(i is used nowhere else in this loop, and it's a mercifully short loop with
no breaks or continues).

Thanks for turning this musing into a patch.

Re: [PATCH] block: don't use for-inside-for in bio_for_each_segment_all

[David Sterba]

On Tue, Apr 09, 2019 at 04:38:41AM -0700, Matthew Wilcox wrote:
> > +++ b/fs/btrfs/inode.c
> > @@ -7919,7 +7918,7 @@ static void btrfs_retry_endio(struct bio *bio)
> >  	struct bio_vec *bvec;
> >  	int uptodate;
> >  	int ret;
> > -	int i;
> > +	int i = 0;
> >  	struct bvec_iter_all iter_all;
> >  
> >  	if (bio->bi_status)
> > @@ -7934,7 +7933,7 @@ static void btrfs_retry_endio(struct bio *bio)
> >  	failure_tree = &BTRFS_I(inode)->io_failure_tree;
> >  
> >  	ASSERT(!bio_flagged(bio, BIO_CLONED));
> > -	bio_for_each_segment_all(bvec, bio, i, iter_all) {
> > +	bio_for_each_segment_all(bvec, bio, iter_all) {
> >  		ret = __readpage_endio_check(inode, io_bio, i, bvec->bv_page,
> >  					     bvec->bv_offset, done->start,
> >  					     bvec->bv_len);
> > @@ -7946,6 +7945,7 @@ static void btrfs_retry_endio(struct bio *bio)
> >  					 bvec->bv_offset);
> >  		else
> >  			uptodate = 0;
> > +		i++;
> >  	}
> 
> I'd be tempted to instead:
> 
> @@ -7935,7 +7935,7 @@ static void btrfs_retry_endio(struct bio *bio)
>  
>         ASSERT(!bio_flagged(bio, BIO_CLONED));
>         bio_for_each_segment_all(bvec, bio, i, iter_all) {
> -               ret = __readpage_endio_check(inode, io_bio, i, bvec->bv_page,
> +               ret = __readpage_endio_check(inode, io_bio, i++, bvec->bv_page,
>                                              bvec->bv_offset, done->start,
>                                              bvec->bv_len);
>                 if (!ret)
> 
> (i is used nowhere else in this loop, and it's a mercifully short loop with
> no breaks or continues).

I'd rather keep the separate statement than having parameters with
sideefects.