# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1225967340 0
# Node ID 61ab98b5cc0ebf20dd766ec67a84319f058ef6f0
# Parent 0729cb8b1292c9168db0b8e3f2251fd0a9d531b8
blkback: Do not queue up bio structs before submitting them.
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
drivers/xen/blkback/blkback.c | 44 +++++++++++++++++++++++++-----------------
1 files changed, 27 insertions(+), 17 deletions(-)
diff -r 0729cb8b1292 -r 61ab98b5cc0e drivers/xen/blkback/blkback.c
--- a/drivers/xen/blkback/blkback.c Wed Nov 05 15:43:55 2008 +0000
+++ b/drivers/xen/blkback/blkback.c Thu Nov 06 10:29:00 2008 +0000
@@ -151,9 +151,9 @@ static void unplug_queue(blkif_t *blkif)
blkif->plug = NULL;
}
-static void plug_queue(blkif_t *blkif, struct bio *bio)
-{
- request_queue_t *q = bdev_get_queue(bio->bi_bdev);
+static void plug_queue(blkif_t *blkif, struct block_device *bdev)
+{
+ request_queue_t *q = bdev_get_queue(bdev);
if (q == blkif->plug)
return;
@@ -389,8 +389,8 @@ static void dispatch_rw_block_io(blkif_t
unsigned long buf; unsigned int nsec;
} seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
unsigned int nseg;
- struct bio *bio = NULL, *biolist[BLKIF_MAX_SEGMENTS_PER_REQUEST];
- int ret, i, nbio = 0;
+ struct bio *bio = NULL;
+ int ret, i;
int operation;
switch (req->operation) {
@@ -477,6 +477,10 @@ static void dispatch_rw_block_io(blkif_t
goto fail_flush;
}
+ plug_queue(blkif, preq.bdev);
+ atomic_set(&pending_req->pendcnt, 1);
+ blkif_get(blkif);
+
for (i = 0; i < nseg; i++) {
if (((int)preq.sector_number|(int)seg[i].nsec) &
((bdev_hardsect_size(preq.bdev) >> 9) - 1)) {
@@ -490,7 +494,12 @@ static void dispatch_rw_block_io(blkif_t
virt_to_page(vaddr(pending_req, i)),
seg[i].nsec << 9,
seg[i].buf & ~PAGE_MASK) == 0)) {
- bio = biolist[nbio++] = bio_alloc(GFP_KERNEL, nseg-i);
+ if (bio) {
+ atomic_inc(&pending_req->pendcnt);
+ submit_bio(operation, bio);
+ }
+
+ bio = bio_alloc(GFP_KERNEL, nseg-i);
if (unlikely(bio == NULL))
goto fail_put_bio;
@@ -505,7 +514,7 @@ static void dispatch_rw_block_io(blkif_t
if (!bio) {
BUG_ON(operation != WRITE_BARRIER);
- bio = biolist[nbio++] = bio_alloc(GFP_KERNEL, 0);
+ bio = bio_alloc(GFP_KERNEL, 0);
if (unlikely(bio == NULL))
goto fail_put_bio;
@@ -515,12 +524,7 @@ static void dispatch_rw_block_io(blkif_t
bio->bi_sector = -1;
}
- plug_queue(blkif, bio);
- atomic_set(&pending_req->pendcnt, nbio);
- blkif_get(blkif);
-
- for (i = 0; i < nbio; i++)
- submit_bio(operation, biolist[i]);
+ submit_bio(operation, bio);
if (operation == READ)
blkif->st_rd_sect += preq.nr_sects;
@@ -529,16 +533,22 @@ static void dispatch_rw_block_io(blkif_t
return;
- fail_put_bio:
- for (i = 0; i < (nbio-1); i++)
- bio_put(biolist[i]);
fail_flush:
fast_flush_area(pending_req);
fail_response:
make_response(blkif, req->id, req->operation, BLKIF_RSP_ERROR);
free_req(pending_req);
msleep(1); /* back off a bit */
-}
+ return;
+
+ fail_put_bio:
+ __end_block_io_op(pending_req, -EINVAL);
+ if (bio)
+ bio_put(bio);
+ unplug_queue(blkif);
+ msleep(1); /* back off a bit */
+ return;
+}
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