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authorRoger Pau Monne <roger.pau@citrix.com>2013-05-02 10:58:50 +0200
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-05-08 08:46:51 -0400
commitb7649158a0d241f8d53d13ff7441858539e16656 (patch)
treeacee055fae1b48f1c986dec29481d2b999dd3127 /drivers/block/xen-blkfront.c
parentbb642e8315fd573795e8b6fa9b9629064d73add1 (diff)
xen-blkfront: use a different scatterlist for each request
In blkif_queue_request blkfront iterates over the scatterlist in order to set the segments of the request, and in blkif_completion blkfront iterates over the raw request, which makes it hard to know the exact position of the source and destination memory positions. This can be solved by allocating a scatterlist for each request, that will be keep until the request is finished, allowing us to copy the data back to the original memory without having to iterate over the raw request. Oracle-Bug: 16660413 - LARGE ASYNCHRONOUS READS APPEAR BROKEN ON 2.6.39-400 CC: stable@vger.kernel.org Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Reported-and-Tested-by: Anne Milicia <anne.milicia@oracle.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/block/xen-blkfront.c')
-rw-r--r--drivers/block/xen-blkfront.c43
1 files changed, 18 insertions, 25 deletions
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 82d63d5b1750..bac8cf31319b 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -76,6 +76,7 @@ struct blk_shadow {
struct request *request;
struct grant **grants_used;
struct grant **indirect_grants;
+ struct scatterlist *sg;
};
struct split_bio {
@@ -113,7 +114,6 @@ struct blkfront_info
enum blkif_state connected;
int ring_ref;
struct blkif_front_ring ring;
- struct scatterlist *sg;
unsigned int evtchn, irq;
struct request_queue *rq;
struct work_struct work;
@@ -438,7 +438,7 @@ static int blkif_queue_request(struct request *req)
req->nr_phys_segments > BLKIF_MAX_SEGMENTS_PER_REQUEST);
BUG_ON(info->max_indirect_segments &&
req->nr_phys_segments > info->max_indirect_segments);
- nseg = blk_rq_map_sg(req->q, req, info->sg);
+ nseg = blk_rq_map_sg(req->q, req, info->shadow[id].sg);
ring_req->u.rw.id = id;
if (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST) {
/*
@@ -469,7 +469,7 @@ static int blkif_queue_request(struct request *req)
}
ring_req->u.rw.nr_segments = nseg;
}
- for_each_sg(info->sg, sg, nseg, i) {
+ for_each_sg(info->shadow[id].sg, sg, nseg, i) {
fsect = sg->offset >> 9;
lsect = fsect + (sg->length >> 9) - 1;
@@ -914,8 +914,6 @@ static void blkif_free(struct blkfront_info *info, int suspend)
}
BUG_ON(info->persistent_gnts_c != 0);
- kfree(info->sg);
- info->sg = NULL;
for (i = 0; i < BLK_RING_SIZE; i++) {
/*
* Clear persistent grants present in requests already
@@ -953,6 +951,8 @@ free_shadow:
info->shadow[i].grants_used = NULL;
kfree(info->shadow[i].indirect_grants);
info->shadow[i].indirect_grants = NULL;
+ kfree(info->shadow[i].sg);
+ info->shadow[i].sg = NULL;
}
/* No more gnttab callback work. */
@@ -979,12 +979,9 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
struct blkif_response *bret)
{
int i = 0;
- struct bio_vec *bvec;
- struct req_iterator iter;
- unsigned long flags;
+ struct scatterlist *sg;
char *bvec_data;
void *shared_data;
- unsigned int offset = 0;
int nseg;
nseg = s->req.operation == BLKIF_OP_INDIRECT ?
@@ -997,19 +994,16 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
* than PAGE_SIZE, we have to keep track of the current offset,
* to be sure we are copying the data from the right shared page.
*/
- rq_for_each_segment(bvec, s->request, iter) {
- BUG_ON((bvec->bv_offset + bvec->bv_len) > PAGE_SIZE);
- if (bvec->bv_offset < offset)
- i++;
- BUG_ON(i >= nseg);
+ for_each_sg(s->sg, sg, nseg, i) {
+ BUG_ON(sg->offset + sg->length > PAGE_SIZE);
shared_data = kmap_atomic(
pfn_to_page(s->grants_used[i]->pfn));
- bvec_data = bvec_kmap_irq(bvec, &flags);
- memcpy(bvec_data, shared_data + bvec->bv_offset,
- bvec->bv_len);
- bvec_kunmap_irq(bvec_data, &flags);
+ bvec_data = kmap_atomic(sg_page(sg));
+ memcpy(bvec_data + sg->offset,
+ shared_data + sg->offset,
+ sg->length);
+ kunmap_atomic(bvec_data);
kunmap_atomic(shared_data);
- offset = bvec->bv_offset + bvec->bv_len;
}
}
/* Add the persistent grant into the list of free grants */
@@ -1656,10 +1650,6 @@ static int blkfront_setup_indirect(struct blkfront_info *info)
xen_blkif_max_segments);
segs = info->max_indirect_segments;
}
- info->sg = kzalloc(sizeof(info->sg[0]) * segs, GFP_KERNEL);
- if (info->sg == NULL)
- goto out_of_memory;
- sg_init_table(info->sg, segs);
err = fill_grant_buffer(info, (segs + INDIRECT_GREFS(segs)) * BLK_RING_SIZE);
if (err)
@@ -1669,26 +1659,29 @@ static int blkfront_setup_indirect(struct blkfront_info *info)
info->shadow[i].grants_used = kzalloc(
sizeof(info->shadow[i].grants_used[0]) * segs,
GFP_NOIO);
+ info->shadow[i].sg = kzalloc(sizeof(info->shadow[i].sg[0]) * segs, GFP_NOIO);
if (info->max_indirect_segments)
info->shadow[i].indirect_grants = kzalloc(
sizeof(info->shadow[i].indirect_grants[0]) *
INDIRECT_GREFS(segs),
GFP_NOIO);
if ((info->shadow[i].grants_used == NULL) ||
+ (info->shadow[i].sg == NULL) ||
(info->max_indirect_segments &&
(info->shadow[i].indirect_grants == NULL)))
goto out_of_memory;
+ sg_init_table(info->shadow[i].sg, segs);
}
return 0;
out_of_memory:
- kfree(info->sg);
- info->sg = NULL;
for (i = 0; i < BLK_RING_SIZE; i++) {
kfree(info->shadow[i].grants_used);
info->shadow[i].grants_used = NULL;
+ kfree(info->shadow[i].sg);
+ info->shadow[i].sg = NULL;
kfree(info->shadow[i].indirect_grants);
info->shadow[i].indirect_grants = NULL;
}