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authorJens Axboe <jens.axboe@oracle.com>2007-10-23 09:49:25 +0200
committerJens Axboe <jens.axboe@oracle.com>2007-10-23 09:49:25 +0200
commit7aeacf982203fb4dea2f3434eefdc268cfd5d6d9 (patch)
tree93a3991d5ab854fce477d9e28e55b720fd6ac81a
parentad0d4083e65d9f223275adbfb9a7927e2120dc6c (diff)
[BLOCK] blk_rq_map_sg: force clear termination bit
Since blk_rq_map_sg() sets the termination bit at the end of the sg table, we could see it prematurely on the next mapping unless we force drivers to do a full sg_init_table() prior to each mapping. So force clear the termination bit to avoid having to put that clear in the driver for every mapping. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
-rw-r--r--block/ll_rw_blk.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index fb8fb8852c3..de5ba479c22 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -1351,8 +1351,20 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
new_segment:
if (!sg)
sg = sglist;
- else
+ else {
+ /*
+ * If the driver previously mapped a shorter
+ * list, we could see a termination bit
+ * prematurely unless it fully inits the sg
+ * table on each mapping. We KNOW that there
+ * must be more entries here or the driver
+ * would be buggy, so force clear the
+ * termination bit to avoid doing a full
+ * sg_init_table() in drivers for each command.
+ */
+ sg->page_link &= ~0x02;
sg = sg_next(sg);
+ }
sg_set_page(sg, bvec->bv_page);
sg->length = nbytes;