On Tue, Sep 25, 2012 at 01:54:52PM +0200, Lars Ellenberg wrote:

On Mon, Sep 24, 2012 at 03:34:46PM -0700, Kent Overstreet wrote:

quoted

Just a little convenience macro - main reason to add it now is preparing
for immutable bio vecs, it'll reduce the size of the patch that puts
bi_sector/bi_size/bi_idx into a struct bvec_iter.

For the DRBD part:

quoted

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 01b2ac6..d90a1fd 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c

@@ -1144,7 +1144,7 @@ void drbd_make_request(struct request_queue *q, struct bio *bio)
 	/* to make some things easier, force alignment of requests within the
 	 * granularity of our hash tables */
 	s_enr = bio->bi_sector >> HT_SHIFT;
-	e_enr = bio->bi_size ? (bio->bi_sector+(bio->bi_size>>9)-1) >> HT_SHIFT : s_enr;
+	e_enr = (bio_end_sector(bio) - 1) >> HT_SHIFT;

You ignored the bio->bi_size ? : ;

#define bio_end_sector(bio)	((bio)->bi_sector + bio_sectors(bio))
which turns out (bio->bi_sector + (bio->bi_size >> 9))

Note that bi_size may be 0, bio_end_sector(bio)-1 then is bi_sector -1,
for an empty flush with bi_sector == 0, this ends up as (sector_t)-1ULL,
and this code path breaks horribly.

Man, that was dumb of me - thanks for catching it. Version below look
good?

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 01b2ac6..47f55db 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c

@@ -1144,7 +1144,7 @@ void drbd_make_request(struct request_queue *q, struct bio *bio)
 	/* to make some things easier, force alignment of requests within the
 	 * granularity of our hash tables */
 	s_enr = bio->bi_sector >> HT_SHIFT;
-	e_enr = bio->bi_size ? (bio->bi_sector+(bio->bi_size>>9)-1) >> HT_SHIFT : s_enr;
+	e_enr = bio->bi_size ? (bio_end_sector(bio) - 1) >> HT_SHIFT : s_enr;
 
 	if (likely(s_enr == e_enr)) {
 		do {