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authorDavid Woodhouse <David.Woodhouse@intel.com>2008-08-05 19:01:53 +0200
committerJens Axboe <jens.axboe@oracle.com>2008-10-09 08:56:01 +0200
commitfb2dce862d9f9a68e6b9374579056ec9eca02a63 (patch)
tree888e0fd7248c9329fa1aa3981043a2dc2457d488 /block/blk-core.c
parentFix up comments about matching flags between bio and rq (diff)
downloadlinux-fb2dce862d9f9a68e6b9374579056ec9eca02a63.tar.xz
linux-fb2dce862d9f9a68e6b9374579056ec9eca02a63.zip
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>
Diffstat (limited to 'block/blk-core.c')
-rw-r--r--block/blk-core.c28
1 files changed, 20 insertions, 8 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index a496727df7ef..1e143c4f9d34 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1079,6 +1079,10 @@ void init_request_from_bio(struct request *req, struct bio *bio)
*/
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 @@ void init_request_from_bio(struct request *req, struct bio *bio)
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 @@ static int __make_request(struct request_queue *q, struct bio *bio)
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 @@ end_io:
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 @@ void submit_bio(int rw, struct bio *bio)
* 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 @@ static int blk_end_io(struct request *rq, int error, unsigned int nr_bytes,
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 @@ EXPORT_SYMBOL_GPL(blk_end_request);
**/
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 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
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;