block: fix "check bi_size overflow before merge"

This partially reverts commit b317ba860223d834737892f9b2d8e7d22fb45f92.

Commit b317ba860223 ("check bi_size overflow before merge") adds a bio_full
check to __bio_try_merge_page.  This will cause __bio_try_merge_page to fail
when the last bi_io_vec has been reached.  Instead, what we want here is only
the bi_size overflow check.

Fixes: b317ba860223 ("block: check bi_size overflow before merge")
Cc: stable@vger.kernel.org # v5.4+
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bio.c b/block/bio.c
index 9d54aa37ce6c7074be56e99a14bc60d0bc058edd..a5d75f6bf4c7eedc96454bade72dbc9fe88af74d 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -754,10 +754,12 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
        if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
                return false;
 
-       if (bio->bi_vcnt > 0 && !bio_full(bio, len)) {
+       if (bio->bi_vcnt > 0) {
                struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
 
                if (page_is_mergeable(bv, page, len, off, same_page)) {
+                       if (bio->bi_iter.bi_size > UINT_MAX - len)
+                               return false;
                        bv->bv_len += len;
                        bio->bi_iter.bi_size += len;
                        return true;