Commit 19047087 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

block: put the same page when adding it to bio 



When the added page is merged to last same page in bio_add_pc_page(),
the user may need to put this page for avoiding page leak.

bio_map_user_iov() needs this kind of handling, and now it deals with
it by itself in hack style.

Moves the handling of put page into __bio_add_pc_page(), so
bio_map_user_iov() may be simplified a bit, and maybe more users
can benefit from this change.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 5919482e

block/bio.c

+16 −12
Original line number Diff line number Diff line
@@ -666,12 +666,13 @@ static inline bool page_is_mergeable(const struct bio_vec *bv, 
}



/**

 *	bio_add_pc_page	-	attempt to add page to passthrough bio

 *	__bio_add_pc_page	- attempt to add page to passthrough bio

 *	@q: the target queue

 *	@bio: destination bio

 *	@page: page to add

 *	@len: vec entry length

 *	@offset: vec entry offset

 *	@put_same_page: put the page if it is same with last added page

 *

 *	Attempt to add a page to the bio_vec maplist. This can fail for a

 *	number of reasons, such as the bio being full or target block device
@@ -680,8 +681,9 @@ static inline bool page_is_mergeable(const struct bio_vec *bv, 
 *

 *	This should only be used by passthrough bios.

 */

int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page

		    *page, unsigned int len, unsigned int offset)

int __bio_add_pc_page(struct request_queue *q, struct bio *bio,

		struct page *page, unsigned int len, unsigned int offset,

		bool put_same_page)

{

	int retried_segments = 0;

	struct bio_vec *bvec;
@@ -705,6 +707,8 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page 


		if (page == bvec->bv_page &&

		    offset == bvec->bv_offset + bvec->bv_len) {

			if (put_same_page)

				put_page(page);

			bvec->bv_len += len;

			bio->bi_iter.bi_size += len;

			goto done;
@@ -763,6 +767,13 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page 
	blk_recount_segments(q, bio);

	return 0;

}

EXPORT_SYMBOL(__bio_add_pc_page);



int bio_add_pc_page(struct request_queue *q, struct bio *bio,

		struct page *page, unsigned int len, unsigned int offset)

{

	return __bio_add_pc_page(q, bio, page, len, offset, false);

}

EXPORT_SYMBOL(bio_add_pc_page);



/**
@@ -1397,21 +1408,14 @@ struct bio *bio_map_user_iov(struct request_queue *q, 
			for (j = 0; j < npages; j++) {

				struct page *page = pages[j];

				unsigned int n = PAGE_SIZE - offs;

				unsigned short prev_bi_vcnt = bio->bi_vcnt;



				if (n > bytes)

					n = bytes;



				if (!bio_add_pc_page(q, bio, page, n, offs))

				if (!__bio_add_pc_page(q, bio, page, n, offs,

							true))

					break;



				/*

				 * check if vector was merged with previous

				 * drop page reference if needed

				 */

				if (bio->bi_vcnt == prev_bi_vcnt)

					put_page(page);



				added += n;

				bytes -= n;

				offs = 0;

include/linux/bio.h

+3 −0
Original line number Diff line number Diff line
@@ -432,6 +432,9 @@ void bio_chain(struct bio *, struct bio *); 
extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);

extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,

			   unsigned int, unsigned int);

extern int __bio_add_pc_page(struct request_queue *, struct bio *,

			     struct page *, unsigned int, unsigned int,

			     bool);

bool __bio_try_merge_page(struct bio *bio, struct page *page,

		unsigned int len, unsigned int off, bool same_page);

void __bio_add_page(struct bio *bio, struct page *page,

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