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Date: Sat, 07 Jan 2023 00:34:21 +0000
From: David Howells <dhowells@...hat.com>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
Matthew Wilcox <willy@...radead.org>,
Logan Gunthorpe <logang@...tatee.com>, dhowells@...hat.com,
Christoph Hellwig <hch@...radead.org>,
Matthew Wilcox <willy@...radead.org>,
Jens Axboe <axboe@...nel.dk>, Jeff Layton <jlayton@...nel.org>,
Logan Gunthorpe <logang@...tatee.com>,
linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v4 7/7] iov_iter,
block: Make bio structs pin pages rather than ref'ing if appropriate
Convert the block layer's bio code to use iov_iter_extract_pages() instead
of iov_iter_get_pages(). This will pin pages or leave them unaltered
rather than getting a ref on them as appropriate to the source iterator.
A field, bi_cleanup_mode, is added to the bio struct that gets set by
iov_iter_extract_pages() with FOLL_* flags indicating what cleanup is
necessary. FOLL_GET -> put_page(), FOLL_PIN -> unpin_user_page(). Other
flags could also be used in future.
Newly allocated bio structs have bi_cleanup_mode set to FOLL_GET to
indicate that attached pages are ref'd by default. Cloning sets it to 0.
__bio_iov_iter_get_pages() overrides it to what iov_iter_extract_pages()
indicates.
[!] Note that this is tested a bit with ext4, but nothing else.
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Al Viro <viro@...iv.linux.org.uk>
cc: Jens Axboe <axboe@...nel.dk>
cc: Christoph Hellwig <hch@....de>
cc: Matthew Wilcox <willy@...radead.org>
cc: Logan Gunthorpe <logang@...tatee.com>
---
block/bio.c | 47 +++++++++++++++++++++++++++++++++------------
include/linux/blk_types.h | 1 +
2 files changed, 35 insertions(+), 13 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index 5f96fcae3f75..eafcbeba0bab 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -243,6 +243,11 @@ static void bio_free(struct bio *bio)
* Users of this function have their own bio allocation. Subsequently,
* they must remember to pair any call to bio_init() with bio_uninit()
* when IO has completed, or when the bio is released.
+ *
+ * We set the initial assumption that pages attached to the bio will be
+ * released with put_page() by setting bi_cleanup_mode to FOLL_GET, but this
+ * should be set to FOLL_PIN if the page should be unpinned instead; if the
+ * pages should not be put or unpinned, this should be set to 0
*/
void bio_init(struct bio *bio, struct block_device *bdev, struct bio_vec *table,
unsigned short max_vecs, blk_opf_t opf)
@@ -274,6 +279,7 @@ void bio_init(struct bio *bio, struct block_device *bdev, struct bio_vec *table,
#ifdef CONFIG_BLK_DEV_INTEGRITY
bio->bi_integrity = NULL;
#endif
+ bio->bi_cleanup_mode = FOLL_GET;
bio->bi_vcnt = 0;
atomic_set(&bio->__bi_remaining, 1);
@@ -302,6 +308,7 @@ void bio_reset(struct bio *bio, struct block_device *bdev, blk_opf_t opf)
{
bio_uninit(bio);
memset(bio, 0, BIO_RESET_BYTES);
+ bio->bi_cleanup_mode = FOLL_GET;
atomic_set(&bio->__bi_remaining, 1);
bio->bi_bdev = bdev;
if (bio->bi_bdev)
@@ -814,6 +821,7 @@ static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp)
bio_set_flag(bio, BIO_CLONED);
bio->bi_ioprio = bio_src->bi_ioprio;
bio->bi_iter = bio_src->bi_iter;
+ bio->bi_cleanup_mode = 0;
if (bio->bi_bdev) {
if (bio->bi_bdev == bio_src->bi_bdev &&
@@ -1168,6 +1176,18 @@ bool bio_add_folio(struct bio *bio, struct folio *folio, size_t len,
return bio_add_page(bio, &folio->page, len, off) > 0;
}
+/*
+ * Clean up a page according to the mode indicated by iov_iter_extract_pages(),
+ * where the page is may be pinned or may have a ref taken on it.
+ */
+static void bio_release_page(struct bio *bio, struct page *page)
+{
+ if (bio->bi_cleanup_mode & FOLL_PIN)
+ unpin_user_page(page);
+ if (bio->bi_cleanup_mode & FOLL_GET)
+ put_page(page);
+}
+
void __bio_release_pages(struct bio *bio, bool mark_dirty)
{
struct bvec_iter_all iter_all;
@@ -1176,7 +1196,7 @@ void __bio_release_pages(struct bio *bio, bool mark_dirty)
bio_for_each_segment_all(bvec, bio, iter_all) {
if (mark_dirty && !PageCompound(bvec->bv_page))
set_page_dirty_lock(bvec->bv_page);
- put_page(bvec->bv_page);
+ bio_release_page(bio, bvec->bv_page);
}
}
EXPORT_SYMBOL_GPL(__bio_release_pages);
@@ -1213,7 +1233,7 @@ static int bio_iov_add_page(struct bio *bio, struct page *page,
}
if (same_page)
- put_page(page);
+ bio_release_page(bio, page);
return 0;
}
@@ -1227,7 +1247,7 @@ static int bio_iov_add_zone_append_page(struct bio *bio, struct page *page,
queue_max_zone_append_sectors(q), &same_page) != len)
return -EINVAL;
if (same_page)
- put_page(page);
+ bio_release_page(bio, page);
return 0;
}
@@ -1238,10 +1258,10 @@ static int bio_iov_add_zone_append_page(struct bio *bio, struct page *page,
* @bio: bio to add pages to
* @iter: iov iterator describing the region to be mapped
*
- * Pins pages from *iter and appends them to @bio's bvec array. The
- * pages will have to be released using put_page() when done.
- * For multi-segment *iter, this function only adds pages from the
- * next non-empty segment of the iov iterator.
+ * Pins pages from *iter and appends them to @bio's bvec array. The pages will
+ * have to be released using put_page() or unpin_user_page() when done as
+ * according to bi_cleanup_mode. For multi-segment *iter, this function only
+ * adds pages from the next non-empty segment of the iov iterator.
*/
static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
{
@@ -1273,9 +1293,10 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
* result to ensure the bio's total size is correct. The remainder of
* the iov data will be picked up in the next bio iteration.
*/
- size = iov_iter_get_pages(iter, pages,
- UINT_MAX - bio->bi_iter.bi_size,
- nr_pages, &offset, gup_flags);
+ size = iov_iter_extract_pages(iter, &pages,
+ UINT_MAX - bio->bi_iter.bi_size,
+ nr_pages, gup_flags,
+ &offset, &bio->bi_cleanup_mode);
if (unlikely(size <= 0))
return size ? size : -EFAULT;
@@ -1308,7 +1329,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
iov_iter_revert(iter, left);
out:
while (i < nr_pages)
- put_page(pages[i++]);
+ bio_release_page(bio, pages[i++]);
return ret;
}
@@ -1489,8 +1510,8 @@ void bio_set_pages_dirty(struct bio *bio)
* the BIO and re-dirty the pages in process context.
*
* It is expected that bio_check_pages_dirty() will wholly own the BIO from
- * here on. It will run one put_page() against each page and will run one
- * bio_put() against the BIO.
+ * here on. It will run one put_page() or unpin_user_page() against each page
+ * and will run one bio_put() against the BIO.
*/
static void bio_dirty_fn(struct work_struct *work);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 99be590f952f..883f873a01ef 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -289,6 +289,7 @@ struct bio {
#endif
};
+ unsigned int bi_cleanup_mode; /* How to clean up pages */
unsigned short bi_vcnt; /* how many bio_vec's */
/*
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