Allow block device drivers to opt-in to receiving bio(s) where the
bio_vec(s) point to memory that is not backed by struct page entries.
When a driver opts in it asserts that it will use the pfn version of the
dma mapping routines and does not use pfn_to_page() in its submission
path.
TODO: add kmap_pfn() and kmap_atomic_pfn() for drivers that want to
touch bio_vec buffers with the cpu prior to submission to a
low-level-device-driver.
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
block/bio.c | 48 ++++++++++++++++++++++++++++++++++++++-------
block/blk-core.c | 5 +++++
include/linux/blk_types.h | 1 +
include/linux/blkdev.h | 2 ++
4 files changed, 48 insertions(+), 8 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index 3d494e85e16d..091c0071e360 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -568,6 +568,7 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
bio->bi_rw = bio_src->bi_rw;
bio->bi_iter = bio_src->bi_iter;
bio->bi_io_vec = bio_src->bi_io_vec;
+ bio->bi_flags |= bio_src->bi_flags & (1 << BIO_PFN);
}
EXPORT_SYMBOL(__bio_clone_fast);
@@ -659,6 +660,8 @@ struct bio *bio_clone_bioset(struct bio *bio_src, gfp_t gfp_mask,
goto integrity_clone;
}
+ bio->bi_flags |= bio_src->bi_flags & (1 << BIO_PFN);
+
bio_for_each_segment(bv, bio_src, iter)
bio->bi_io_vec[bio->bi_vcnt++] = bv;
@@ -700,9 +703,9 @@ 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)
+static int __bio_add_pfn(struct request_queue *q, struct bio *bio,
+ __pfn_t pfn, unsigned int len, unsigned int offset,
+ unsigned int max_sectors)
{
int retried_segments = 0;
struct bio_vec *bvec;
@@ -724,7 +727,7 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
if (bio->bi_vcnt > 0) {
struct bio_vec *prev = &bio->bi_io_vec[bio->bi_vcnt - 1];
- if (page == bvec_page(prev) &&
+ if (pfn.pfn == prev->bv_pfn.pfn &&
offset == prev->bv_offset + prev->bv_len) {
unsigned int prev_bv_len = prev->bv_len;
prev->bv_len += len;
@@ -769,7 +772,7 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
* cannot add the page
*/
bvec = &bio->bi_io_vec[bio->bi_vcnt];
- bvec_set_page(bvec, page);
+ bvec->bv_pfn = pfn;
bvec->bv_len = len;
bvec->bv_offset = offset;
bio->bi_vcnt++;
@@ -819,7 +822,7 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
return len;
failed:
- bvec_set_page(bvec, NULL);
+ bvec->bv_pfn.pfn = 0;
bvec->bv_len = 0;
bvec->bv_offset = 0;
bio->bi_vcnt--;
@@ -846,7 +849,7 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct 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_page(q, bio, page, len, offset,
+ return __bio_add_pfn(q, bio, page_to_pfn_typed(page), len, offset,
queue_max_hw_sectors(q));
}
EXPORT_SYMBOL(bio_add_pc_page);
@@ -873,10 +876,39 @@ int bio_add_page(struct bio *bio, struct page *page, unsigned int len,
if ((max_sectors < (len >> 9)) && !bio->bi_iter.bi_size)
max_sectors = len >> 9;
- return __bio_add_page(q, bio, page, len, offset, max_sectors);
+ return __bio_add_pfn(q, bio, page_to_pfn_typed(page), len, offset,
+ max_sectors);
}
EXPORT_SYMBOL(bio_add_page);
+/**
+ * bio_add_pfn - attempt to add pfn to bio
+ * @bio: destination bio
+ * @pfn: pfn to add
+ * @len: vec entry length
+ * @offset: vec entry offset
+ *
+ * Identical to bio_add_page() except this variant flags the bio as
+ * not have struct page backing. A given request_queue must assert
+ * that it is prepared to handle this constraint before bio(s)
+ * flagged in the manner can be passed.
+ */
+int bio_add_pfn(struct bio *bio, __pfn_t pfn, unsigned int len,
+ unsigned int offset)
+{
+ struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+ unsigned int max_sectors;
+
+ if (!blk_queue_pfn(q))
+ return 0;
+ set_bit(BIO_PFN, &bio->bi_flags);
+ 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;
+
+ return __bio_add_pfn(q, bio, pfn, len, offset, max_sectors);
+}
+
struct submit_bio_ret {
struct completion event;
int error;
diff --git a/block/blk-core.c b/block/blk-core.c
index 7830ce00cbf5..8bafb4c87c96 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1843,6 +1843,11 @@ generic_make_request_checks(struct bio *bio)
goto end_io;
}
+ if (bio_flagged(bio, BIO_PFN) && !blk_queue_pfn(q)) {
+ err = -EOPNOTSUPP;
+ goto end_io;
+ }
+
/*
* Various block parts want %current->io_context and lazy ioc
* allocation ends up trading a lot of pain for a small amount of
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 7f63fa3e4fda..653bb4fd0706 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -140,6 +140,7 @@ struct bio {
#define BIO_NULL_MAPPED 8 /* contains invalid user pages */
#define BIO_QUIET 9 /* Make BIO Quiet */
#define BIO_SNAP_STABLE 10 /* bio data must be snapshotted during write */
+#define BIO_PFN 11 /* bio_vec references memory without struct page */
/*
* Flags starting here get preserved by bio_reset() - this includes
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7f9a516f24de..e17ecefba80a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -513,6 +513,7 @@ struct request_queue {
#define QUEUE_FLAG_INIT_DONE 20 /* queue is initialized */
#define QUEUE_FLAG_NO_SG_MERGE 21 /* don't attempt to merge SG segments*/
#define QUEUE_FLAG_SG_GAPS 22 /* queue doesn't support SG gaps */
+#define QUEUE_FLAG_PFN 23 /* queue supports pfn-only bio_vec(s) */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \
@@ -594,6 +595,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
#define blk_queue_noxmerges(q) \
test_bit(QUEUE_FLAG_NOXMERGES, &(q)->queue_flags)
#define blk_queue_nonrot(q) test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags)
+#define blk_queue_pfn(q) test_bit(QUEUE_FLAG_PFN, &(q)->queue_flags)
#define blk_queue_io_stat(q) test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)
#define blk_queue_add_random(q) test_bit(QUEUE_FLAG_ADD_RANDOM, &(q)->queue_flags)
#define blk_queue_stackable(q) \
--
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