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[BLOCK] blk_rq_map_sg: force clear termination bit

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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>
This commit is contained in:
Jens Axboe 2007-10-23 09:49:25 +02:00
parent ad0d4083e6
commit 7aeacf9822
1 changed files with 13 additions and 1 deletions
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14
block/ll_rw_blk.c
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@ -1351,8 +1351,20 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
new_segment: new_segment:
if (!sg) if (!sg)
sg = sglist; 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 = sg_next(sg);
}
sg_set_page(sg, bvec->bv_page); sg_set_page(sg, bvec->bv_page);
sg->length = nbytes; sg->length = nbytes;