Add 'discard' request handling
Some block devices benefit from a hint that they can forget the contents
of certain sectors. Add basic support for this to the block core, along
with a 'blkdev_issue_discard()' helper function which issues such
requests.
The caller doesn't get to provide an end_io functio, since
blkdev_issue_discard() will automatically split the request up into
multiple bios if appropriate. Neither does the function wait for
completion -- it's expected that callers won't care about when, or even
_if_, the request completes. It's only a hint to the device anyway. By
definition, the file system doesn't _care_ about these sectors any more.
[With feedback from OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> and
Jens Axboe <jens.axboe@oracle.com]
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-core.c b/block/blk-core.c
index a496727..1e143c4 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1079,6 +1079,10 @@
*/
if (unlikely(bio_barrier(bio)))
req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
+ if (unlikely(bio_discard(bio))) {
+ req->cmd_flags |= (REQ_SOFTBARRIER | REQ_DISCARD);
+ req->q->prepare_discard_fn(req->q, req);
+ }
if (bio_sync(bio))
req->cmd_flags |= REQ_RW_SYNC;
@@ -1095,7 +1099,7 @@
static int __make_request(struct request_queue *q, struct bio *bio)
{
struct request *req;
- int el_ret, nr_sectors, barrier, err;
+ int el_ret, nr_sectors, barrier, discard, err;
const unsigned short prio = bio_prio(bio);
const int sync = bio_sync(bio);
int rw_flags;
@@ -1115,6 +1119,12 @@
goto end_io;
}
+ discard = bio_discard(bio);
+ if (unlikely(discard) && !q->prepare_discard_fn) {
+ err = -EOPNOTSUPP;
+ goto end_io;
+ }
+
spin_lock_irq(q->queue_lock);
if (unlikely(barrier) || elv_queue_empty(q))
@@ -1405,7 +1415,8 @@
if (bio_check_eod(bio, nr_sectors))
goto end_io;
- if (bio_empty_barrier(bio) && !q->prepare_flush_fn) {
+ if ((bio_empty_barrier(bio) && !q->prepare_flush_fn) ||
+ (bio_discard(bio) && !q->prepare_discard_fn)) {
err = -EOPNOTSUPP;
goto end_io;
}
@@ -1487,7 +1498,6 @@
* go through the normal accounting stuff before submission.
*/
if (bio_has_data(bio)) {
-
if (rw & WRITE) {
count_vm_events(PGPGOUT, count);
} else {
@@ -1881,7 +1891,7 @@
struct request_queue *q = rq->q;
unsigned long flags = 0UL;
- if (bio_has_data(rq->bio)) {
+ if (bio_has_data(rq->bio) || blk_discard_rq(rq)) {
if (__end_that_request_first(rq, error, nr_bytes))
return 1;
@@ -1939,7 +1949,7 @@
**/
int __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
{
- if (bio_has_data(rq->bio) &&
+ if ((bio_has_data(rq->bio) || blk_discard_rq(rq)) &&
__end_that_request_first(rq, error, nr_bytes))
return 1;
@@ -2012,12 +2022,14 @@
we want BIO_RW_AHEAD (bit 1) to imply REQ_FAILFAST (bit 1). */
rq->cmd_flags |= (bio->bi_rw & 3);
- rq->nr_phys_segments = bio_phys_segments(q, bio);
- rq->nr_hw_segments = bio_hw_segments(q, bio);
+ if (bio_has_data(bio)) {
+ rq->nr_phys_segments = bio_phys_segments(q, bio);
+ rq->nr_hw_segments = bio_hw_segments(q, bio);
+ rq->buffer = bio_data(bio);
+ }
rq->current_nr_sectors = bio_cur_sectors(bio);
rq->hard_cur_sectors = rq->current_nr_sectors;
rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
- rq->buffer = bio_data(bio);
rq->data_len = bio->bi_size;
rq->bio = rq->biotail = bio;
