diff options
| -rw-r--r-- | drivers/block/ll_rw_blk.c | 8 | ||||
| -rw-r--r-- | fs/bio.c | 4 |
2 files changed, 8 insertions, 4 deletions
diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c index 530f6c5962aa..c23382abd4f5 100644 --- a/drivers/block/ll_rw_blk.c +++ b/drivers/block/ll_rw_blk.c @@ -173,9 +173,11 @@ EXPORT_SYMBOL(blk_queue_prep_rq); * are dynamic, and thus we have to query the queue whether it is ok to * add a new bio_vec to a bio at a given offset or not. If the block device * has such limitations, it needs to register a merge_bvec_fn to control - * the size of bio's sent to it. Per default now merge_bvec_fn is defined for - * a queue, and only the fixed limits are honored. - * + * the size of bio's sent to it. Note that a block device *must* allow a + * single page to be added to an empty bio. The block device driver may want + * to use the bio_split() function to deal with these bio's. By default + * no merge_bvec_fn is defined for a queue, and only the fixed limits are + * honored. */ void blk_queue_merge_bvec(request_queue_t *q, merge_bvec_fn *mbfn) { @@ -290,7 +290,9 @@ int bio_get_nr_vecs(struct block_device *bdev) * * Attempt to add a page to the bio_vec maplist. This can fail for a * number of reasons, such as the bio being full or target block - * device limitations. + * device limitations. The target block device must allow bio's + * smaller than PAGE_SIZE, so it is always possible to add a single + * page to an empty bio. */ int bio_add_page(struct bio *bio, struct page *page, unsigned int len, unsigned int offset) |