diff options
| author | Roger Pau Monne <roger.pau@citrix.com> | 2013-08-12 12:53:43 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2013-11-08 09:10:27 -0700 |
| commit | c47206e25f28232ff979994c32758c82841d81cd (patch) | |
| tree | 5b3a5b0830778f0bffaa97eee715f7a99ac3f01b /drivers/block/xen-blkfront.c | |
| parent | fbe363c476afe8ec992d3baf682670a4bd1b6ce6 (diff) | |
xen-blkfront: improve aproximation of required grants per request
Improve the calculation of required grants to process a request by
using nr_phys_segments instead of always assuming a request is going
to use all posible segments.
nr_phys_segments contains the number of scatter-gather DMA addr+len
pairs, which is basically what we put at every granted page.
for_each_sg iterates over the DMA addr+len pairs and uses a grant
page for each of them.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/block/xen-blkfront.c')
| -rw-r--r-- | drivers/block/xen-blkfront.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 429d52640940..5b8a15483a4c 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -400,10 +400,13 @@ static int blkif_queue_request(struct request *req) if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) return 1; - max_grefs = info->max_indirect_segments ? - info->max_indirect_segments + - INDIRECT_GREFS(info->max_indirect_segments) : - BLKIF_MAX_SEGMENTS_PER_REQUEST; + max_grefs = req->nr_phys_segments; + if (max_grefs > BLKIF_MAX_SEGMENTS_PER_REQUEST) + /* + * If we are using indirect segments we need to account + * for the indirect grefs used in the request. + */ + max_grefs += INDIRECT_GREFS(req->nr_phys_segments); /* Check if we have enough grants to allocate a requests */ if (info->persistent_gnts_c < max_grefs) { |