On Tue, 2008-08-05 at 13:42 +0200, Jens Axboe wrote:
<some stuff>
Incremental patch below; I'll commit it to a git tree in discrete
patches, and publish those.
You can just pass NULL as your end_io function to blkdev_issue_discard()
and it'll set it to bio_put() for you.
We'll probably want to make the elevator capable of merging discard
requests -- and even letting them cross real read/write requests for
other sectors, and just dropping them if there's a subsequent write
request covering the same region, etc.
diff -u b/block/blk-barrier.c b/block/blk-barrier.c
--- b/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -320,17 +321,16 @@
* @bdev: blockdev to issue discard for
* @sector: start sector
* @nr_sects: number of sectors to discard
- * @error_sector: error sector
+ * @end_io: end_io function (or NULL)
*
* Description:
- * Issue a discard request for the sectors in question. Caller can supply
- * room for storing the error offset in case of a discard error, if they
- * wish to.
+ * Issue a discard request for the sectors in question. Caller can pass an
+ * end_io function (which must call bio_put()), if they really want to see
+ * the outcome. Most callers probably won't, and can just pass NULL.
*/
int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
- unsigned nr_sects, sector_t *error_sector)
+ unsigned nr_sects, bio_end_io_t end_io)
{
- DECLARE_COMPLETION_ONSTACK(wait);
struct request_queue *q;
struct bio *bio;
int ret;
@@ -343,33 +343,24 @@
return -ENXIO;
+ /* Many callers won't care at all about the outcome. After all,
+ this is just a hint to the underlying device. They'll just
+ ignore errors completely. So the end_io function can be just
+ a call to bio_put() */
+ if (!end_io)
+ end_io = (void *)&bio_put;
+
+ if (!q->discard_fn)
+ return -EOPNOTSUPP;
+
bio = bio_alloc(GFP_KERNEL, 0);
if (!bio)
return -ENOMEM;
- bio->bi_end_io = bio_end_empty_barrier;
- bio->bi_private = &wait;
+ bio->bi_end_io = end_io;
bio->bi_bdev = bdev;
bio->bi_sector = sector;
bio->bi_size = nr_sects << 9;
submit_bio(1 << BIO_RW_DISCARD, bio);
-
- wait_for_completion(&wait);
-
- /*
- * The driver must store the error location in ->bi_sector, if
- * it supports it. For non-stacked drivers, this should be copied
- * from rq->sector.
- */
- if (error_sector)
- *error_sector = bio->bi_sector;
-
- ret = 0;
- if (bio_flagged(bio, BIO_EOPNOTSUPP))
- ret = -EOPNOTSUPP;
- else if (!bio_flagged(bio, BIO_UPTODATE))
- ret = -EIO;
-
- bio_put(bio);
- return ret;
+ return 0;
}
EXPORT_SYMBOL(blkdev_issue_discard);
diff -u b/block/blk-core.c b/block/blk-core.c
--- b/block/blk-core.c
+++ b/block/blk-core.c
@@ -1502,10 +1501,9 @@
* If it's a regular read/write or a barrier with data attached,
* go through the normal accounting stuff before submission.
*/
- if (!bio_empty_barrier(bio) && !bio_discard(bio)) {
+ if (!bio_dataless(bio)) {
BIO_BUG_ON(!bio->bi_size);
- BIO_BUG_ON(!bio->bi_io_vec);
if (rw & WRITE) {
count_vm_events(PGPGOUT, count);
@@ -1576,12 +1574,13 @@
int nbytes;
/*
- * For an empty barrier request or sector discard request, the
- * low level driver must store a potential error location in
- * ->sector. We pass that back up in ->bi_sector.
+ * For an empty barrier request, the low level driver must
+ * store a potential error location in ->sector. We pass
+ * that back up in ->bi_sector.
*/
- if (blk_empty_barrier(req) || blk_discard_rq(req))
+ if (blk_empty_barrier(req))
bio->bi_sector = req->sector;
+
if (nr_bytes >= bio->bi_size) {
req->bio = bio->bi_next;
nbytes = bio->bi_size;
diff -u b/fs/fat/fatent.c b/fs/fat/fatent.c
--- b/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -528,15 +528,6 @@
return err;
}
-static void fat_discard_cluster(struct super_block *sb, int cluster)
-{
- struct msdos_sb_info *sbi = MSDOS_SB(sb);
- struct block_device *bdev = sb->s_bdev;
- unsigned long sector = fat_clus_to_blknr(sbi, cluster);
-
- blkdev_issue_discard(bdev, sector, sbi->sec_per_clus, NULL);
-}
-
int fat_free_clusters(struct inode *inode, int cluster)
{
struct super_block *sb = inode->i_sb;
@@ -550,8 +541,11 @@
fatent_init(&fatent);
lock_fat(sbi);
do {
- fat_discard_cluster(sb, cluster);
-
+ /* Issue discard for the sectors we no longer care about */
+ blkdev_issue_discard(sb->s_bdev,
+ fat_clus_to_blknr(sbi, cluster),
+ sbi->sec_per_clus, NULL);
+
cluster = fat_ent_read(inode, &fatent, cluster);
if (cluster < 0) {
err = cluster;
diff -u b/include/linux/bio.h b/include/linux/bio.h
--- b/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -191,6 +191,8 @@
#define bio_discard(bio) ((bio)->bi_rw & (1 << BIO_RW_DISCARD))
#define bio_empty_barrier(bio) (bio_barrier(bio) && !(bio)->bi_size)
+#define bio_dataless(bio) (!(bio)->bi_io_vec)
+
static inline unsigned int bio_cur_sectors(struct bio *bio)
{
if (unlikely(bio_discard(bio)))
diff -u b/include/linux/blkdev.h b/include/linux/blkdev.h
--- b/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -546,6 +546,7 @@
#define blk_empty_barrier(rq) (blk_barrier_rq(rq) && blk_fs_request(rq) && !(rq)->hard_nr_sectors)
/* rq->queuelist of dequeued request must be list_empty() */
#define blk_queued_rq(rq) (!list_empty(&(rq)->queuelist))
+#define blk_dataless_rq(rq) (!(rq)->buffer)
#define list_entry_rq(ptr) list_entry((ptr), struct request, queuelist)
@@ -836,7 +837,7 @@
}
extern int blkdev_issue_flush(struct block_device *, sector_t *);
-extern int blkdev_issue_discard(struct block_device *, sector_t, unsigned, sector_t *);
+extern int blkdev_issue_discard(struct block_device *, sector_t, unsigned, bio_end_io_t *);
/*
* command filter functions
--
David Woodhouse Open Source Technology Centre
David.Woodhouse@xxxxxxxxx Intel Corporation
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