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authorJens Axboe <jens.axboe@oracle.com>2007-10-23 03:49:25 -0400
committerJens Axboe <jens.axboe@oracle.com>2007-10-23 03:49:25 -0400
commit7aeacf982203fb4dea2f3434eefdc268cfd5d6d9 (patch)
tree93a3991d5ab854fce477d9e28e55b720fd6ac81a /block/ll_rw_blk.c
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>
Diffstat (limited to 'block/ll_rw_blk.c')
-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 fb8fb8852c3b..de5ba479c224 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,
1351new_segment: 1351new_segment:
1352 if (!sg) 1352 if (!sg)
1353 sg = sglist; 1353 sg = sglist;
1354 else 1354 else {
1355 /*
1356 * If the driver previously mapped a shorter
1357 * list, we could see a termination bit
1358 * prematurely unless it fully inits the sg
1359 * table on each mapping. We KNOW that there
1360 * must be more entries here or the driver
1361 * would be buggy, so force clear the
1362 * termination bit to avoid doing a full
1363 * sg_init_table() in drivers for each command.
1364 */
1365 sg->page_link &= ~0x02;
1355 sg = sg_next(sg); 1366 sg = sg_next(sg);
1367 }
1356 1368
1357 sg_set_page(sg, bvec->bv_page); 1369 sg_set_page(sg, bvec->bv_page);
1358 sg->length = nbytes; 1370 sg->length = nbytes;