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authorChristoph Hellwig <hch@infradead.org>2009-09-30 13:52:12 +0200
committerJens Axboe <jens.axboe@oracle.com>2009-10-01 21:19:30 +0200
commitc15227de132f1295f3db6b7df9079956b1020fd8 (patch)
treead06f119f283cf8a6313681055e8132ba2851ddb /block
parent3bd0f0c763e497c8674b28e3df2732f48683dabd (diff)
block: use normal I/O path for discard requests
prepare_discard_fn() was being called in a place where memory allocation was effectively impossible. This makes it inappropriate for all but the most trivial translations of Linux's DISCARD operation to the block command set. Additionally adding a payload there makes the ownership of the bio backing unclear as it's now allocated by the device driver and not the submitter as usual. It is replaced with QUEUE_FLAG_DISCARD which is used to indicate whether the queue supports discard operations or not. blkdev_issue_discard now allocates a one-page, sector-length payload which is the right thing for the common ATA and SCSI implementations. The mtd implementation of prepare_discard_fn() is replaced with simply checking for the request being a discard. Largely based on a previous patch from Matthew Wilcox <matthew@wil.cx> which did the prepare_discard_fn but not the different payload allocation yet. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block')
-rw-r--r--block/blk-barrier.c35
-rw-r--r--block/blk-core.c3
-rw-r--r--block/blk-settings.c17
3 files changed, 31 insertions, 24 deletions
diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index 6593ab39cfe..21f5025c394 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -350,6 +350,7 @@ static void blkdev_discard_end_io(struct bio *bio, int err)
if (bio->bi_private)
complete(bio->bi_private);
+ __free_page(bio_page(bio));
bio_put(bio);
}
@@ -372,26 +373,44 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
struct request_queue *q = bdev_get_queue(bdev);
int type = flags & DISCARD_FL_BARRIER ?
DISCARD_BARRIER : DISCARD_NOBARRIER;
+ struct bio *bio;
+ struct page *page;
int ret = 0;
if (!q)
return -ENXIO;
- if (!q->prepare_discard_fn)
+ if (!blk_queue_discard(q))
return -EOPNOTSUPP;
while (nr_sects && !ret) {
- struct bio *bio = bio_alloc(gfp_mask, 0);
- if (!bio)
- return -ENOMEM;
+ unsigned int sector_size = q->limits.logical_block_size;
+ bio = bio_alloc(gfp_mask, 1);
+ if (!bio)
+ goto out;
+ bio->bi_sector = sector;
bio->bi_end_io = blkdev_discard_end_io;
bio->bi_bdev = bdev;
if (flags & DISCARD_FL_WAIT)
bio->bi_private = &wait;
- bio->bi_sector = sector;
+ /*
+ * Add a zeroed one-sector payload as that's what
+ * our current implementations need. If we'll ever need
+ * more the interface will need revisiting.
+ */
+ page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (!page)
+ goto out_free_bio;
+ if (bio_add_pc_page(q, bio, page, sector_size, 0) < sector_size)
+ goto out_free_page;
+ /*
+ * And override the bio size - the way discard works we
+ * touch many more blocks on disk than the actual payload
+ * length.
+ */
if (nr_sects > queue_max_hw_sectors(q)) {
bio->bi_size = queue_max_hw_sectors(q) << 9;
nr_sects -= queue_max_hw_sectors(q);
@@ -414,5 +433,11 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
bio_put(bio);
}
return ret;
+out_free_page:
+ __free_page(page);
+out_free_bio:
+ bio_put(bio);
+out:
+ return -ENOMEM;
}
EXPORT_SYMBOL(blkdev_issue_discard);
diff --git a/block/blk-core.c b/block/blk-core.c
index 8135228e4b2..80a020dd158 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1124,7 +1124,6 @@ void init_request_from_bio(struct request *req, struct bio *bio)
req->cmd_flags |= REQ_DISCARD;
if (bio_rw_flagged(bio, BIO_RW_BARRIER))
req->cmd_flags |= REQ_SOFTBARRIER;
- req->q->prepare_discard_fn(req->q, req);
} else if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER)))
req->cmd_flags |= REQ_HARDBARRIER;
@@ -1470,7 +1469,7 @@ static inline void __generic_make_request(struct bio *bio)
goto end_io;
if (bio_rw_flagged(bio, BIO_RW_DISCARD) &&
- !q->prepare_discard_fn) {
+ !blk_queue_discard(q)) {
err = -EOPNOTSUPP;
goto end_io;
}
diff --git a/block/blk-settings.c b/block/blk-settings.c
index eaf122ff5f1..d29498ef1eb 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -34,23 +34,6 @@ void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
EXPORT_SYMBOL(blk_queue_prep_rq);
/**
- * blk_queue_set_discard - set a discard_sectors function for queue
- * @q: queue
- * @dfn: prepare_discard function
- *
- * It's possible for a queue to register a discard callback which is used
- * to transform a discard request into the appropriate type for the
- * hardware. If none is registered, then discard requests are failed
- * with %EOPNOTSUPP.
- *
- */
-void blk_queue_set_discard(struct request_queue *q, prepare_discard_fn *dfn)
-{
- q->prepare_discard_fn = dfn;
-}
-EXPORT_SYMBOL(blk_queue_set_discard);
-
-/**
* blk_queue_merge_bvec - set a merge_bvec function for queue
* @q: queue
* @mbfn: merge_bvec_fn