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block: use normal I/O path for discard requests

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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>
This commit is contained in:
Christoph Hellwig 2009-09-30 13:52:12 +02:00 committed by Jens Axboe
parent 3bd0f0c763
commit 1122a26f2a
6 changed files with 39 additions and 43 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

35
block/blk-barrier.c
View file

@ -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);

3
block/blk-core.c
View file

@ -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;
}

17
block/blk-settings.c
View file

@ -33,23 +33,6 @@ 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

19
drivers/mtd/mtd_blkdevs.c
View file

@ -32,14 +32,6 @@ struct mtd_blkcore_priv {
spinlock_t queue_lock;
};
static int blktrans_discard_request(struct request_queue *q,
struct request *req)
{
req->cmd_type = REQ_TYPE_LINUX_BLOCK;
req->cmd[0] = REQ_LB_OP_DISCARD;
return 0;
}
static int do_blktrans_request(struct mtd_blktrans_ops *tr,
struct mtd_blktrans_dev *dev,
struct request *req)
@ -52,10 +44,6 @@ static int do_blktrans_request(struct mtd_blktrans_ops *tr,
buf = req->buffer;
if (req->cmd_type == REQ_TYPE_LINUX_BLOCK &&
req->cmd[0] == REQ_LB_OP_DISCARD)
return tr->discard(dev, block, nsect);
if (!blk_fs_request(req))
return -EIO;
@ -63,6 +51,9 @@ static int do_blktrans_request(struct mtd_blktrans_ops *tr,
get_capacity(req->rq_disk))
return -EIO;
if (blk_discard_rq(req))
return tr->discard(dev, block, nsect);
switch(rq_data_dir(req)) {
case READ:
for (; nsect > 0; nsect--, block++, buf += tr->blksize)
@ -380,8 +371,8 @@ int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
tr->blkcore_priv->rq->queuedata = tr;
blk_queue_logical_block_size(tr->blkcore_priv->rq, tr->blksize);
if (tr->discard)
blk_queue_set_discard(tr->blkcore_priv->rq,
blktrans_discard_request);
queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
tr->blkcore_priv->rq);
tr->blkshift = ffs(tr->blksize) - 1;

2
drivers/staging/dst/dcore.c
View file

@ -102,7 +102,7 @@ static int dst_request(struct request_queue *q, struct bio *bio)
struct dst_node *n = q->queuedata;
int err = -EIO;
if (bio_empty_barrier(bio) && !q->prepare_discard_fn) {
if (bio_empty_barrier(bio) && !blk_queue_discard(q)) {
/*
* This is a dirty^Wnice hack, but if we complete this
* operation with -EOPNOTSUPP like intended, XFS

6
include/linux/blkdev.h
View file

@ -82,7 +82,6 @@ enum rq_cmd_type_bits {
enum {
REQ_LB_OP_EJECT = 0x40, /* eject request */
REQ_LB_OP_FLUSH = 0x41, /* flush request */
REQ_LB_OP_DISCARD = 0x42, /* discard sectors */
};
/*
@ -261,7 +260,6 @@ typedef void (request_fn_proc) (struct request_queue *q);
typedef int (make_request_fn) (struct request_queue *q, struct bio *bio);
typedef int (prep_rq_fn) (struct request_queue *, struct request *);
typedef void (unplug_fn) (struct request_queue *);
typedef int (prepare_discard_fn) (struct request_queue *, struct request *);
struct bio_vec;
struct bvec_merge_data {
@ -340,7 +338,6 @@ struct request_queue
make_request_fn *make_request_fn;
prep_rq_fn *prep_rq_fn;
unplug_fn *unplug_fn;
prepare_discard_fn *prepare_discard_fn;
merge_bvec_fn *merge_bvec_fn;
prepare_flush_fn *prepare_flush_fn;
softirq_done_fn *softirq_done_fn;
@ -460,6 +457,7 @@ struct request_queue
#define QUEUE_FLAG_VIRT QUEUE_FLAG_NONROT /* paravirt device */
#define QUEUE_FLAG_IO_STAT 15 /* do IO stats */
#define QUEUE_FLAG_CQ 16 /* hardware does queuing */
#define QUEUE_FLAG_DISCARD 17 /* supports DISCARD */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_CLUSTER) | \
@ -591,6 +589,7 @@ enum {
#define blk_queue_flushing(q) ((q)->ordseq)
#define blk_queue_stackable(q) \
test_bit(QUEUE_FLAG_STACKABLE, &(q)->queue_flags)
#define blk_queue_discard(q) test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)
#define blk_fs_request(rq) ((rq)->cmd_type == REQ_TYPE_FS)
#define blk_pc_request(rq) ((rq)->cmd_type == REQ_TYPE_BLOCK_PC)
@ -955,7 +954,6 @@ extern void blk_queue_merge_bvec(struct request_queue *, merge_bvec_fn *);
extern void blk_queue_dma_alignment(struct request_queue *, int);
extern void blk_queue_update_dma_alignment(struct request_queue *, int);
extern void blk_queue_softirq_done(struct request_queue *, softirq_done_fn *);
extern void blk_queue_set_discard(struct request_queue *, prepare_discard_fn *);
extern void blk_queue_rq_timed_out(struct request_queue *, rq_timed_out_fn *);
extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);