From: Ming Lin <mlin@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
Kent Overstreet <kent.overstreet@gmail.com>,
Dongsu Park <dongsu.park@profitbricks.com>,
Ming Lin <mlin@kernel.org>, Christoph Hellwig <hch@infradead.org>
Subject: [PATCH 02/10] block: simplify bio_add_page()
Date: Mon, 27 Apr 2015 23:48:29 -0700 [thread overview]
Message-ID: <1430203717-13307-3-git-send-email-mlin@kernel.org> (raw)
In-Reply-To: <1430203717-13307-1-git-send-email-mlin@kernel.org>
From: Kent Overstreet <kent.overstreet@gmail.com>
Since generic_make_request() can now handle arbitrary size bios, all we
have to do is make sure the bvec array doesn't overflow.
__bio_add_page() doesn't need to call ->merge_bvec_fn(), where
we can get rid of unnecessary code paths.
Note that removing call to ->merge_bvec_fn() is fine for
bio_add_pc_page(), as SCSI devices usually don't even need that.
Few exceptional cases like pscsi or osd are not affected either.
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
[dpark: rebase and resolve merge conflicts, change a couple of comments,
make bio_add_page() warn once upon a cloned bio.]
Signed-off-by: Dongsu Park <dongsu.park@profitbricks.com>
Signed-off-by: Ming Lin <mlin@kernel.org>
---
block/bio.c | 135 +++++++++++++++++++++++++-----------------------------------
1 file changed, 55 insertions(+), 80 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index f66a4ea..ae31cdb 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -699,9 +699,23 @@ 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;
@@ -712,7 +726,7 @@ 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;
/*
@@ -725,28 +739,7 @@ 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;
- }
- }
-
bio->bi_iter.bi_size += len;
goto done;
}
@@ -789,27 +782,6 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
blk_recount_segments(q, bio);
}
- /*
- * 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 - len,
- .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)
- goto failed;
- }
-
/* If we may be able to merge these biovecs, force a recount */
if (bio->bi_vcnt > 1 && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec)))
bio->bi_flags &= ~(1 << BIO_SEG_VALID);
@@ -826,28 +798,6 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
blk_recount_segments(q, bio);
return 0;
}
-
-/**
- * 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);
/**
@@ -857,22 +807,47 @@ 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 either bio->bi_vcnt == bio->bi_max_vecs or it's a cloned bio.
*/
-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);
- unsigned int max_sectors;
+ struct bio_vec *bv;
- max_sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
- if ((max_sectors < (len >> 9)) && !bio->bi_iter.bi_size)
- max_sectors = len >> 9;
+ /*
+ * cloned bio must not modify vec list
+ */
+ if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
+ return 0;
- return __bio_add_page(q, bio, page, len, offset, max_sectors);
+ /*
+ * 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);
--
1.9.1
next prev parent reply other threads:[~2015-04-28 6:49 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-28 6:48 [RFC PATCH v2 00/10] simplify block layer based on immutable biovecs Ming Lin
2015-04-28 6:48 ` [PATCH 01/10] block: make generic_make_request handle arbitrarily sized bios Ming Lin
2015-04-28 11:43 ` Christoph Hellwig
2015-04-28 16:01 ` Keith Busch
2015-05-06 6:08 ` Ming Lin
2015-05-06 6:48 ` Christoph Hellwig
2015-05-06 7:13 ` Ming Lin
2015-04-28 6:48 ` Ming Lin [this message]
2015-04-28 12:12 ` [PATCH 02/10] block: simplify bio_add_page() Christoph Hellwig
2015-04-29 5:42 ` Ming Lin
2015-04-28 6:48 ` [PATCH 03/10] block: allow __blk_queue_bounce() to handle bios larger than BIO_MAX_PAGES Ming Lin
2015-04-28 6:48 ` [PATCH 04/10] bcache: clean up hacks around bio_split_pool Ming Lin
2015-04-28 12:14 ` Christoph Hellwig
2015-04-29 5:43 ` Ming Lin
2015-04-28 6:48 ` [PATCH 05/10] btrfs: remove bio splitting and merge_bvec_fn() calls Ming Lin
2015-04-28 6:48 ` [PATCH 06/10] md/raid5: get rid of bio_fits_rdev() Ming Lin
2015-04-28 6:48 ` [PATCH 07/10] block: kill merge_bvec_fn() completely Ming Lin
2015-04-28 17:31 ` Alasdair G Kergon
2015-04-29 6:32 ` Ming Lin
2015-04-28 22:09 ` NeilBrown
2015-05-04 7:47 ` Ming Lin
2015-05-06 7:10 ` Ming Lin
2015-05-06 7:26 ` Christoph Hellwig
2015-05-06 17:05 ` Ming Lin
2015-04-28 6:48 ` [PATCH 08/10] fs: use helper bio_add_page() instead of open coding on bi_io_vec Ming Lin
2015-04-28 6:48 ` [PATCH 09/10] md/raid10: make sync_request_write() call bio_copy_data() Ming Lin
2015-04-28 6:48 ` [PATCH 10/10] Documentation: update notes in biovecs about arbitrarily sized bios Ming Lin
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