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Subject[PATCH 3/5] block: Gut bio_add_page()
Date
Since generic_make_request() can now handle arbitrary size bios, all we
have to do is make sure the bvec array doesn't overflow.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
---
fs/bio.c | 137 ++++++++++++++++++++++++++-------------------------------------
1 file changed, 57 insertions(+), 80 deletions(-)

diff --git a/fs/bio.c b/fs/bio.c
index 75c49a3..da27557 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -690,9 +690,23 @@ int bio_get_nr_vecs(struct block_device *bdev)
}
EXPORT_SYMBOL(bio_get_nr_vecs);

-static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
- *page, unsigned int len, unsigned int offset,
- unsigned int max_sectors)
+/**
+ * bio_add_pc_page - attempt to add page to bio
+ * @q: the target queue
+ * @bio: destination bio
+ * @page: page to add
+ * @len: vec entry length
+ * @offset: vec entry offset
+ *
+ * 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
+ * limitations. The target block device must allow bio's up to PAGE_SIZE,
+ * so it is always possible to add a single page to an empty bio.
+ *
+ * This should only be used by REQ_PC bios.
+ */
+int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
+ *page, unsigned int len, unsigned int offset)
{
int retried_segments = 0;
struct bio_vec *bvec;
@@ -703,7 +717,7 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
if (unlikely(bio_flagged(bio, BIO_CLONED)))
return 0;

- if (((bio->bi_iter.bi_size + len) >> 9) > max_sectors)
+ if (((bio->bi_iter.bi_size + len) >> 9) > queue_max_hw_sectors(q))
return 0;

/*
@@ -716,28 +730,7 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page

if (page == prev->bv_page &&
offset == prev->bv_offset + prev->bv_len) {
- unsigned int prev_bv_len = prev->bv_len;
prev->bv_len += len;
-
- if (q->merge_bvec_fn) {
- struct bvec_merge_data bvm = {
- /* prev_bvec is already charged in
- bi_size, discharge it in order to
- simulate merging updated prev_bvec
- as new bvec. */
- .bi_bdev = bio->bi_bdev,
- .bi_sector = bio->bi_iter.bi_sector,
- .bi_size = bio->bi_iter.bi_size -
- prev_bv_len,
- .bi_rw = bio->bi_rw,
- };
-
- if (q->merge_bvec_fn(q, &bvm, prev) < prev->bv_len) {
- prev->bv_len -= len;
- return 0;
- }
- }
-
goto done;
}
}
@@ -768,31 +761,6 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
bvec->bv_len = len;
bvec->bv_offset = offset;

- /*
- * if queue has other restrictions (eg varying max sector size
- * depending on offset), it can specify a merge_bvec_fn in the
- * queue to get further control
- */
- if (q->merge_bvec_fn) {
- struct bvec_merge_data bvm = {
- .bi_bdev = bio->bi_bdev,
- .bi_sector = bio->bi_iter.bi_sector,
- .bi_size = bio->bi_iter.bi_size,
- .bi_rw = bio->bi_rw,
- };
-
- /*
- * merge_bvec_fn() returns number of bytes it can accept
- * at this offset
- */
- if (q->merge_bvec_fn(q, &bvm, bvec) < bvec->bv_len) {
- bvec->bv_page = NULL;
- bvec->bv_len = 0;
- bvec->bv_offset = 0;
- return 0;
- }
- }
-
/* If we may be able to merge these biovecs, force a recount */
if (bio->bi_vcnt && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec)))
bio->bi_flags &= ~(1 << BIO_SEG_VALID);
@@ -803,28 +771,6 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
bio->bi_iter.bi_size += len;
return len;
}
-
-/**
- * bio_add_pc_page - attempt to add page to bio
- * @q: the target queue
- * @bio: destination bio
- * @page: page to add
- * @len: vec entry length
- * @offset: vec entry offset
- *
- * 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
- * limitations. The target block device must allow bio's up to PAGE_SIZE,
- * so it is always possible to add a single page to an empty bio.
- *
- * This should only be used by REQ_PC bios.
- */
-int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page *page,
- unsigned int len, unsigned int offset)
-{
- return __bio_add_page(q, bio, page, len, offset,
- queue_max_hw_sectors(q));
-}
EXPORT_SYMBOL(bio_add_pc_page);

/**
@@ -834,16 +780,47 @@ EXPORT_SYMBOL(bio_add_pc_page);
* @len: vec entry length
* @offset: vec entry offset
*
- * 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
- * limitations. The target block device must allow bio's up to PAGE_SIZE,
- * so it is always possible to add a single page to an empty bio.
+ * Attempt to add a page to the bio_vec maplist. This will only fail if
+ * bio->bi_vcnt == bio->bi_max_vecs.
*/
-int bio_add_page(struct bio *bio, struct page *page, unsigned int len,
- unsigned int offset)
+int bio_add_page(struct bio *bio, struct page *page,
+ unsigned int len, unsigned int offset)
{
- struct request_queue *q = bdev_get_queue(bio->bi_bdev);
- return __bio_add_page(q, bio, page, len, offset, queue_max_sectors(q));
+ struct bio_vec *bv;
+
+ /*
+ * cloned bio must not modify vec list
+ */
+ if (unlikely(bio_flagged(bio, BIO_CLONED)))
+ return 0;
+
+ /*
+ * For filesystems with a blocksize smaller than the pagesize
+ * we will often be called with the same page as last time and
+ * a consecutive offset. Optimize this special case.
+ */
+ if (bio->bi_vcnt > 0) {
+ bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
+
+ if (page == bv->bv_page &&
+ offset == bv->bv_offset + bv->bv_len) {
+ bv->bv_len += len;
+ goto done;
+ }
+ }
+
+ if (bio->bi_vcnt >= bio->bi_max_vecs)
+ return 0;
+
+ bv = &bio->bi_io_vec[bio->bi_vcnt];
+ bv->bv_page = page;
+ bv->bv_len = len;
+ bv->bv_offset = offset;
+
+ bio->bi_vcnt++;
+done:
+ bio->bi_iter.bi_size += len;
+ return len;
}
EXPORT_SYMBOL(bio_add_page);

--
1.8.4.3


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