bio allocation failure due to bio_get_nr_vecs()

commit f908ee9463b09ddd05e1c1a0111132212dc05fac upstream.

The number of bio_get_nr_vecs() is passed down via bio_alloc() to
bvec_alloc_bs(), which fails the bio allocation if
nr_iovecs > BIO_MAX_PAGES. For the underlying caller this causes an
unexpected bio allocation failure.
Limiting to queue_max_segments() is not sufficient, as max_segments
also might be very large.

bvec_alloc_bs(gfp_mask, nr_iovecs, ) => NULL when nr_iovecs  > BIO_MAX_PAGES
bio_alloc_bioset(gfp_mask, nr_iovecs, ...)
bio_alloc(GFP_NOIO, nvecs)
xfs_alloc_ioend_bio()

Signed-off-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/bio.c b/fs/bio.c
index b980ecd..4fc4dbb 100644 (file)
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -505,9 +505,14 @@ EXPORT_SYMBOL(bio_clone);
 int bio_get_nr_vecs(struct block_device *bdev)
 {
        struct request_queue *q = bdev_get_queue(bdev);
-       return min_t(unsigned,
+       int nr_pages;
+
+       nr_pages = min_t(unsigned,
                     queue_max_segments(q),
                     queue_max_sectors(q) / (PAGE_SIZE >> 9) + 1);
+
+       return min_t(unsigned, nr_pages, BIO_MAX_PAGES);
+
 }
 EXPORT_SYMBOL(bio_get_nr_vecs);