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| author | Christoph Hellwig <hch@infradead.org> | 2009-09-30 13:52:12 +0200 |
|---|---|---|
| committer | Jens Axboe <jens.axboe@oracle.com> | 2009-10-01 21:19:30 +0200 |
| commit | c15227de132f1295f3db6b7df9079956b1020fd8 (patch) | |
| tree | ad06f119f283cf8a6313681055e8132ba2851ddb /block/blk-barrier.c | |
| parent | 3bd0f0c763e497c8674b28e3df2732f48683dabd (diff) | |
| download | lwn-c15227de132f1295f3db6b7df9079956b1020fd8.tar.gz lwn-c15227de132f1295f3db6b7df9079956b1020fd8.zip | |
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/blk-barrier.c')
| -rw-r--r-- | block/blk-barrier.c | 35 |
1 files changed, 30 insertions, 5 deletions
diff --git a/block/blk-barrier.c b/block/blk-barrier.c index 6593ab39cfe9..21f5025c3945 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); |