From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@infradead.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Kent Overstreet <kent.overstreet@gmail.com>
Cc: David Sterba <dsterba@suse.cz>, Huang Ying <ying.huang@intel.com>,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
Theodore Ts'o <tytso@mit.edu>,
"Darrick J . Wong" <darrick.wong@oracle.com>,
Coly Li <colyli@suse.de>, Filipe Manana <fdmanana@gmail.com>,
Randy Dunlap <rdunlap@infradead.org>,
Christoph Hellwig <hch@lst.de>
Subject: [PATCH V6 03/30] block: use bio_add_page in bio_iov_iter_get_pages
Date: Sat, 9 Jun 2018 20:29:47 +0800 [thread overview]
Message-ID: <20180609123014.8861-4-ming.lei@redhat.com> (raw)
In-Reply-To: <20180609123014.8861-1-ming.lei@redhat.com>
From: Christoph Hellwig <hch@lst.de>
Replace a nasty hack with a different nasty hack to prepare for multipage
bio_vecs. By moving the temporary page array as far up as possible in
the space allocated for the bio_vec array we can iterate forward over it
and thus use bio_add_page. Using bio_add_page means we'll be able to
merge physically contiguous pages once support for multipath bio_vecs is
merged.
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/bio.c | 45 +++++++++++++++++++++------------------------
1 file changed, 21 insertions(+), 24 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index ebd3ca62e037..cb0f46e2752b 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -902,6 +902,8 @@ int bio_add_page(struct bio *bio, struct page *page,
}
EXPORT_SYMBOL(bio_add_page);
+#define PAGE_PTRS_PER_BVEC (sizeof(struct bio_vec) / sizeof(struct page *))
+
/**
* bio_iov_iter_get_pages - pin user or kernel pages and add them to a bio
* @bio: bio to add pages to
@@ -913,38 +915,33 @@ EXPORT_SYMBOL(bio_add_page);
int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
{
unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
+ unsigned short entries_left = bio->bi_max_vecs - bio->bi_vcnt;
struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
struct page **pages = (struct page **)bv;
- size_t offset, diff;
- ssize_t size;
+ ssize_t size, left;
+ unsigned len, i;
+ size_t offset;
+
+ /*
+ * Move page array up in the allocated memory for the bio vecs as
+ * far as possible so that we can start filling biovecs from the
+ * beginning without overwriting the temporary page array.
+ */
+ BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
+ pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
if (unlikely(size <= 0))
return size ? size : -EFAULT;
- nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE;
- /*
- * Deep magic below: We need to walk the pinned pages backwards
- * because we are abusing the space allocated for the bio_vecs
- * for the page array. Because the bio_vecs are larger than the
- * page pointers by definition this will always work. But it also
- * means we can't use bio_add_page, so any changes to it's semantics
- * need to be reflected here as well.
- */
- bio->bi_iter.bi_size += size;
- bio->bi_vcnt += nr_pages;
-
- diff = (nr_pages * PAGE_SIZE - offset) - size;
- while (nr_pages--) {
- bv[nr_pages].bv_page = pages[nr_pages];
- bv[nr_pages].bv_len = PAGE_SIZE;
- bv[nr_pages].bv_offset = 0;
- }
+ for (left = size, i = 0; left > 0; left -= len, i++) {
+ struct page *page = pages[i];
- bv[0].bv_offset += offset;
- bv[0].bv_len -= offset;
- if (diff)
- bv[bio->bi_vcnt - 1].bv_len -= diff;
+ len = min_t(size_t, PAGE_SIZE - offset, left);
+ if (WARN_ON_ONCE(bio_add_page(bio, page, len, offset) != len))
+ return -EINVAL;
+ offset = 0;
+ }
iov_iter_advance(iter, size);
return 0;
--
2.9.5
next prev parent reply other threads:[~2018-06-09 12:29 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-09 12:29 [PATCH V6 00/30] block: support multipage bvec Ming Lei
2018-06-09 12:29 ` [PATCH V6 01/30] block: simplify bio_check_pages_dirty Ming Lei
2018-06-09 12:29 ` [PATCH V6 02/30] block: bio_set_pages_dirty can't see NULL bv_page in a valid bio_vec Ming Lei
2018-06-09 12:29 ` Ming Lei [this message]
2018-06-09 12:29 ` [PATCH V6 04/30] block: introduce multipage page bvec helpers Ming Lei
2018-06-09 12:29 ` [PATCH V6 05/30] block: introduce bio_for_each_chunk() Ming Lei
2018-06-09 12:29 ` [PATCH V6 06/30] block: use bio_for_each_chunk() to compute multipage bvec count Ming Lei
2018-06-09 12:29 ` [PATCH V6 07/30] block: use bio_for_each_chunk() to map sg Ming Lei
2018-06-09 12:29 ` [PATCH V6 08/30] block: introduce chunk_last_segment() Ming Lei
2018-06-11 17:19 ` Christoph Hellwig
2018-06-12 3:24 ` Ming Lei
2018-06-09 12:29 ` [PATCH V6 09/30] fs/buffer.c: use bvec iterator to truncate the bio Ming Lei
2018-06-09 12:29 ` [PATCH V6 10/30] btrfs: use chunk_last_segment to get bio's last page Ming Lei
2018-06-09 12:29 ` [PATCH V6 11/30] block: implement bio_pages_all() via bio_for_each_segment_all() Ming Lei
2018-06-13 14:44 ` Christoph Hellwig
2018-06-14 1:23 ` Ming Lei
2018-06-14 6:20 ` Christoph Hellwig
2018-06-09 12:29 ` [PATCH V6 12/30] block: introduce bio_chunks() Ming Lei
2018-06-13 14:47 ` Christoph Hellwig
2018-06-13 14:57 ` Kent Overstreet
2018-06-09 12:29 ` [PATCH V6 13/30] block: introduce rq_for_each_chunk() Ming Lei
2018-06-13 14:48 ` Christoph Hellwig
2018-06-14 1:52 ` Ming Lei
2018-06-09 12:29 ` [PATCH V6 14/30] block: loop: pass multipage chunks to iov_iter Ming Lei
2018-06-09 12:29 ` [PATCH V6 15/30] block: introduce bio_clone_chunk_bioset() Ming Lei
2018-06-13 14:56 ` Christoph Hellwig
2018-06-14 2:01 ` Ming Lei
2018-06-14 6:39 ` Christoph Hellwig
2018-06-14 7:28 ` Ming Lei
2018-06-09 12:30 ` [PATCH V6 16/30] dm: clone bio via bio_clone_chunk_bioset Ming Lei
2018-06-09 12:30 ` [PATCH V6 17/30] block: introduce bio_for_each_chunk_all and bio_for_each_chunk_segment_all Ming Lei
2018-06-09 12:30 ` [PATCH V6 18/30] block: convert to bio_for_each_chunk_segment_all() Ming Lei
2018-06-09 12:30 ` [PATCH V6 19/30] md/dm/bcache: conver to bio_for_each_chunk_segment_all and bio_for_each_chunk_all Ming Lei
2018-06-10 12:38 ` Coly Li
2018-06-13 14:57 ` Christoph Hellwig
2018-06-09 12:30 ` [PATCH V6 20/30] fs: conver to bio_for_each_chunk_segment_all() Ming Lei
2018-06-09 12:30 ` [PATCH V6 21/30] btrfs: conver to bio_for_each_chunk_segment_all Ming Lei
2018-06-09 12:30 ` [PATCH V6 22/30] ext4: " Ming Lei
2018-06-09 12:30 ` [PATCH V6 23/30] f2fs: " Ming Lei
2018-06-09 12:30 ` [PATCH V6 24/30] xfs: " Ming Lei
2018-06-09 12:30 ` [PATCH V6 25/30] exofs: " Ming Lei
2018-06-09 12:30 ` [PATCH V6 26/30] gfs2: " Ming Lei
2018-06-09 12:30 ` [PATCH V6 27/30] block: kill bio_for_each_segment_all() Ming Lei
2018-06-09 12:30 ` [PATCH V6 28/30] block: enable multipage bvecs Ming Lei
2018-06-09 12:30 ` [PATCH V6 29/30] block: always define BIO_MAX_PAGES as 256 Ming Lei
2018-06-09 12:30 ` [PATCH V6 30/30] block: document usage of bio iterator helpers Ming Lei
2018-06-15 15:43 ` Gi-Oh Kim
2018-06-11 16:48 ` [PATCH V6 00/30] block: support multipage bvec Christoph Hellwig
2018-06-12 3:42 ` Ming Lei
2018-06-13 14:42 ` Christoph Hellwig
2018-06-14 1:18 ` Ming Lei
2018-06-14 6:18 ` Christoph Hellwig
2018-06-13 14:59 ` Kent Overstreet
2018-06-14 1:20 ` Ming Lei
2018-06-15 12:59 ` Gi-Oh Kim
2018-06-21 1:17 ` Ming Lei
2018-06-21 8:40 ` Gi-Oh Kim
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