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Message-Id: <1269842965-4700-6-git-send-email-dmonakhov@openvz.org>
Date: Mon, 29 Mar 2010 10:09:24 +0400
From: Dmitry Monakhov <dmonakhov@...nvz.org>
To: linux-kernel@...r.kernel.org
Cc: jens.axboe@...cle.com, Dmitry Monakhov <dmonakhov@...nvz.org>
Subject: [PATCH 5/6] blkdev: optimize discard request logic
Current submit procedure is suboptimal. Each bio is flagged with
barrier flag, so we will end up with following trace:
for_each_bio(discar_bios) {
q->pre_flush
handle(bio);
disk->flush_cache
q->post_flush
}
But in fact user want following semantics:
q->pre_flush()
for_each_bio(discar_bios)
handle(bio)
q->pre_flush()
Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
---
block/blk-lib.c | 141 +++++++++++++++++++++++++++++++-----------------------
1 files changed, 81 insertions(+), 60 deletions(-)
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 4c5a278..5326d91 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -129,17 +129,22 @@ EXPORT_SYMBOL(__blkdev_issue_zeroout);
static void blkdev_discard_end_io(struct bio *bio, int err)
{
- if (err) {
- if (err == -EOPNOTSUPP)
- set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
- clear_bit(BIO_UPTODATE, &bio->bi_flags);
- }
-
- if (bio->bi_private)
- complete(bio->bi_private);
- __free_page(bio_page(bio));
+ if (bio_page(bio))
+ put_page(bio_page(bio));
+}
- bio_put(bio);
+static int add_discard_payload(struct bio *bio, gfp_t gfp_mask, int len)
+{
+ struct page *page;
+ struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+
+ page = alloc_page(gfp_mask | __GFP_ZERO);
+ if (!page)
+ return -ENOMEM;
+ if (bio_add_pc_page(q, bio, page, len, 0) < len)
+ BUG();
+ get_page(page);
+ return 0;
}
/**
@@ -153,16 +158,18 @@ static void blkdev_discard_end_io(struct bio *bio, int err)
* Description:
* Issue a discard request for the sectors in question.
*/
+
int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
- sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
+ sector_t nr_sects, gfp_t gfp_mask, unsigned long flags)
{
+ int ret = 0;
+ struct bio *bio;
+ struct bio_batch bb;
+ unsigned int sz, issued = 0;
DECLARE_COMPLETION_ONSTACK(wait);
struct request_queue *q = bdev_get_queue(bdev);
- int type = flags & BLKDEV_IFL_BARRIER ?
- DISCARD_BARRIER : DISCARD_NOBARRIER;
- struct bio *bio;
- struct page *page;
- int ret = 0;
+ unsigned int sect_sz;
+ sector_t max_discard_sectors;
if (!q)
return -ENXIO;
@@ -170,65 +177,79 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
if (!blk_queue_discard(q))
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);
+ sect_sz = q->limits.logical_block_size;
+ max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
+ atomic_set(&bb.done, 0);
+ bb.flags = 1 << BIO_UPTODATE;
+ bb.wait = &wait;
+ bb.end_io = blkdev_discard_end_io;
- bio = bio_alloc(gfp_mask, 1);
+ if (flags & BLKDEV_IFL_BARRIER) {
+ /* issue async barrier before the data */
+ ret = blkdev_issue_flush(bdev, gfp_mask, NULL, 0);
+ if (ret)
+ return ret;
+ }
+submit:
+ while (nr_sects != 0) {
+ bio = bio_alloc(gfp_mask,
+ min(nr_sects, (sector_t)BIO_MAX_PAGES));
if (!bio)
- goto out;
+ break;
+
bio->bi_sector = sector;
- bio->bi_end_io = blkdev_discard_end_io;
- bio->bi_bdev = bdev;
- if (flags & BLKDEV_IFL_BARRIER)
- bio->bi_private = &wait;
+ bio->bi_bdev = bdev;
+ bio->bi_end_io = bio_batch_end_io;
+
+ if (flags && BLKDEV_IFL_WAIT)
+ bio->bi_private = &bb;
if (blk_queue_discard_mem(q)) {
/*
* Add a zeroed one-sector payload as that's what
- * our current implementations need. If we'll ever
+ * 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;
- sector += max_discard_sectors;
- } else {
- bio->bi_size = nr_sects << 9;
- nr_sects = 0;
+ ret = add_discard_payload(bio, gfp_mask, sect_sz);
+ if (ret) {
+ bio_put(bio);
+ break;
+ }
}
+ sz = min(max_discard_sectors , nr_sects);
+ bio->bi_size = sz << 9;
+ nr_sects -= sz;
+ sector += sz;
- bio_get(bio);
- submit_bio(type, bio);
+ issued++;
+ submit_bio(DISCARD_NOBARRIER, bio);
+ }
+ /*
+ * When all data bios are in flight. Send final barrier if requeted.
+ */
+ if (nr_sects == 0 && flags & BLKDEV_IFL_BARRIER)
+ ret = blkdev_issue_flush(bdev, gfp_mask, NULL,
+ flags & BLKDEV_IFL_WAIT);
- if (flags & BLKDEV_IFL_BARRIER)
+ if (flags & BLKDEV_IFL_WAIT)
+ /* Wait for submitted bios and then continue */
+ while ( issued != atomic_read(&bb.done))
wait_for_completion(&wait);
- if (bio_flagged(bio, BIO_EOPNOTSUPP))
- ret = -EOPNOTSUPP;
- else if (!bio_flagged(bio, BIO_UPTODATE))
- ret = -EIO;
- bio_put(bio);
+ if (!test_bit(BIO_UPTODATE, &bb.flags))
+ /* One of bios in the batch was completed with error.*/
+ ret = -EIO;
+
+ if (ret)
+ goto out;
+
+ if (test_bit(BIO_EOPNOTSUPP, &bb.flags)) {
+ ret = -EOPNOTSUPP;
+ goto out;
}
- return ret;
-out_free_page:
- __free_page(page);
-out_free_bio:
- bio_put(bio);
+ if (nr_sects != 0)
+ goto submit;
out:
- return -ENOMEM;
+ return ret;
}
EXPORT_SYMBOL(blkdev_issue_discard);
--
1.6.6.1
--
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