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block: don't allocate a payload for discard request

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Allocating a fixed payload for discard requests always was a horrible hack,
and it's not coming to byte us when adding support for discard in DM/MD.

So change the code to leave the allocation of a payload to the lowlevel
driver.  Unfortunately that means we'll need another hack, which allows
us to update the various block layer length fields indicating that we
have a payload.  Instead of hiding this in sd.c, which we already partially
do for UNMAP support add a documented helper in the core block layer for it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Christoph Hellwig
2010-06-18 16:59:42 +02:00
committed by Jens Axboe
parent 082439004b
commit 66ac028019
4 changed files with 75 additions and 46 deletions
Download Patch File Download Diff File Expand all files Collapse all files
block/blk-core.c
+32
View File
@@ -1135,6 +1135,38 @@ void blk_put_request(struct request *req)
}
EXPORT_SYMBOL(blk_put_request);
/**
* blk_add_request_payload - add a payload to a request
* @rq: request to update
* @page: page backing the payload
* @len: length of the payload.
*
* This allows to later add a payload to an already submitted request by
* a block driver. The driver needs to take care of freeing the payload
* itself.
*
* Note that this is a quite horrible hack and nothing but handling of
* discard requests should ever use it.
*/
void blk_add_request_payload(struct request *rq, struct page *page,
unsigned int len)
{
struct bio *bio = rq->bio;
bio->bi_io_vec->bv_page = page;
bio->bi_io_vec->bv_offset = 0;
bio->bi_io_vec->bv_len = len;
bio->bi_size = len;
bio->bi_vcnt = 1;
bio->bi_phys_segments = 1;
rq->__data_len = rq->resid_len = len;
rq->nr_phys_segments = 1;
rq->buffer = bio_data(bio);
}
EXPORT_SYMBOL_GPL(blk_add_request_payload);
void init_request_from_bio(struct request *req, struct bio *bio)
{
req->cpu = bio->bi_comp_cpu;
block/blk-lib.c
+6 -27
View File
@@ -19,7 +19,6 @@ 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);
}
@@ -43,7 +42,6 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
int type = flags & BLKDEV_IFL_BARRIER ?
DISCARD_BARRIER : DISCARD_NOBARRIER;
struct bio *bio;
struct page *page;
int ret = 0;
if (!q)
@@ -53,35 +51,21 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
return -EOPNOTSUPP;
while (nr_sects && !ret) {
unsigned int sector_size = q->limits.logical_block_size;
unsigned int max_discard_sectors =
min(q->limits.max_discard_sectors, UINT_MAX >> 9);
bio = bio_alloc(gfp_mask, 1);
if (!bio)
goto out;
if (!bio) {
ret = -ENOMEM;
break;
}
bio->bi_sector = sector;
bio->bi_end_io = blkdev_discard_end_io;
bio->bi_bdev = bdev;
if (flags & BLKDEV_IFL_WAIT)
bio->bi_private = &wait;
/*
* 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_mask | __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 > max_discard_sectors) {
bio->bi_size = max_discard_sectors << 9;
nr_sects -= max_discard_sectors;
@@ -103,13 +87,8 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
ret = -EIO;
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);