| Message ID | 20171023145126.2471-5-hch@lst.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 10/23/2017 04:51 PM, Christoph Hellwig wrote: > This helpers allows to bounce steal the uncompleted bios from a request so > that they can be reissued on another path. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > Reviewed-by: Sagi Grimberg <sagi@grimberg.me> > --- > block/blk-core.c | 20 ++++++++++++++++++++ > include/linux/blkdev.h | 2 ++ > 2 files changed, 22 insertions(+) > Reviewed-by: Hannes Reinecke <hare@suse.com> Cheers, Hannes
On 10/23/2017 5:51 PM, Christoph Hellwig wrote: > This helpers allows to bounce steal the uncompleted bios from a request so > that they can be reissued on another path. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > Reviewed-by: Sagi Grimberg <sagi@grimberg.me> > --- > block/blk-core.c | 20 ++++++++++++++++++++ > include/linux/blkdev.h | 2 ++ > 2 files changed, 22 insertions(+) > > diff --git a/block/blk-core.c b/block/blk-core.c > index b8c80f39f5fe..e804529e65a5 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -2767,6 +2767,26 @@ struct request *blk_fetch_request(struct request_queue *q) > } > EXPORT_SYMBOL(blk_fetch_request); > > +/* > + * Steal bios from a request. The request must not have been partially > + * completed before. > + */ Maybe we can add to the comment that "list" is the destination for the stolen bio. > +void blk_steal_bios(struct bio_list *list, struct request *rq) > +{ > + if (rq->bio) { > + if (list->tail) > + list->tail->bi_next = rq->bio; > + else > + list->head = rq->bio; > + list->tail = rq->biotail; if list->tail != NULL don't we lose the "list->tail->bi_next = rq->bio;" assignment after assigning "list->tail = rq->biotail;" ? > + } > + > + rq->bio = NULL; we can add this NULL assignment inside the big "if", but I'm not sure regarding the next 2 assignments. Anyway not a big deal. > + rq->biotail = NULL; > + rq->__data_len = 0; > +} > +EXPORT_SYMBOL_GPL(blk_steal_bios); > +
On Tue, Oct 24, 2017 at 11:44:26AM +0300, Max Gurtovoy wrote: >> + * Steal bios from a request. The request must not have been partially >> + * completed before. >> + */ > > Maybe we can add to the comment that "list" is the destination for the > stolen bio. Sure. >> +void blk_steal_bios(struct bio_list *list, struct request *rq) >> +{ >> + if (rq->bio) { >> + if (list->tail) >> + list->tail->bi_next = rq->bio; >> + else >> + list->head = rq->bio; >> + list->tail = rq->biotail; > > if list->tail != NULL don't we lose the "list->tail->bi_next = rq->bio;" > assignment after assigning "list->tail = rq->biotail;" ? the biolists are a little weird, they are a single linked list of bi_next plus a tail pointer. So if the list is emptry (->tail == NULL) we assign the biolist to ->head and point ->tail to end of the list in the request. But if the list is not empty we let ->bi_next of the last entry (as found in ->tail) point to the list we splice on, and still update ->tail to end of the list we spliced on. So I think this looks all ok. >> + } >> + >> + rq->bio = NULL; > > we can add this NULL assignment inside the big "if", but I'm not sure > regarding the next 2 assignments. > Anyway not a big deal. We can move both the ->bio and ->biotail assignments, and I've done it.
diff --git a/block/blk-core.c b/block/blk-core.c index b8c80f39f5fe..e804529e65a5 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -2767,6 +2767,26 @@ struct request *blk_fetch_request(struct request_queue *q) } EXPORT_SYMBOL(blk_fetch_request); +/* + * Steal bios from a request. The request must not have been partially + * completed before. + */ +void blk_steal_bios(struct bio_list *list, struct request *rq) +{ + if (rq->bio) { + if (list->tail) + list->tail->bi_next = rq->bio; + else + list->head = rq->bio; + list->tail = rq->biotail; + } + + rq->bio = NULL; + rq->biotail = NULL; + rq->__data_len = 0; +} +EXPORT_SYMBOL_GPL(blk_steal_bios); + /** * blk_update_request - Special helper function for request stacking drivers * @req: the request being processed diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 780f01db5899..45c63764a14e 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1110,6 +1110,8 @@ extern struct request *blk_peek_request(struct request_queue *q); extern void blk_start_request(struct request *rq); extern struct request *blk_fetch_request(struct request_queue *q); +void blk_steal_bios(struct bio_list *list, struct request *rq); + /* * Request completion related functions. *