bio_add_hw_page currently always fails or succeeds. This is fine for
the existing callers that always add PAGE_SIZE worth given that the
max_segment_size and max_sectors must always allow at least a page
worth of data. But when we want to add it for bigger amounts of data
this means it can also fail when adding the data to a bio, and creating
a fallback for that becomes really annoying in the callers.
Make use of the existing API design that allows to return a smaller
length than the one passed in and add up to max_segment_size worth
of data from a larger input. All the existing callers are fine with
this - not because they handle this return correctly, but because they
never pass more than a page in.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
block/bio.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/block/bio.c b/block/bio.c
index cef830adbc06e0..335d81398991b3 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -966,10 +966,13 @@ int bio_add_hw_page(struct request_queue *q, struct bio *bio,
struct page *page, unsigned int len, unsigned int offset,
unsigned int max_sectors, bool *same_page)
{
+ unsigned int max_size = max_sectors << SECTOR_SHIFT;
+
if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
return 0;
- if (((bio->bi_iter.bi_size + len) >> SECTOR_SHIFT) > max_sectors)
+ len = min3(len, max_size, queue_max_segment_size(q));
+ if (len > max_size - bio->bi_iter.bi_size)
return 0;
if (bio->bi_vcnt > 0) {
--
2.39.2
