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block: put the same page when adding it to bio

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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: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2019-03-17 18:01:08 +08:00 committed by Jens Axboe
parent 5919482e22
commit 190470871a
2 changed files with 19 additions and 12 deletions
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28
block/bio.c
View File

@ -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;

3
include/linux/bio.h
View File

@ -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,