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blk-core: use BIO list management functions

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Now that the bio list management stuff is generic, convert
generic_make_request to use bio lists instead of its own private bio
list implementation.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Akinobu Mita 2010-02-23 08:55:42 +01:00 committed by Jens Axboe
parent d02f0cff1d
commit bddd87c7e6
2 changed files with 16 additions and 19 deletions
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31
block/blk-core.c
View file

@ -1490,9 +1490,9 @@ static inline void __generic_make_request(struct bio *bio)
/*
* We only want one ->make_request_fn to be active at a time,
* else stack usage with stacked devices could be a problem.
* So use current->bio_{list,tail} to keep a list of requests
* So use current->bio_list to keep a list of requests
* submited by a make_request_fn function.
* current->bio_tail is also used as a flag to say if
* current->bio_list is also used as a flag to say if
* generic_make_request is currently active in this task or not.
* If it is NULL, then no make_request is active. If it is non-NULL,
* then a make_request is active, and new requests should be added
@ -1500,11 +1500,11 @@ static inline void __generic_make_request(struct bio *bio)
*/
void generic_make_request(struct bio *bio)
{
if (current->bio_tail) {
struct bio_list bio_list_on_stack;
if (current->bio_list) {
/* make_request is active */
*(current->bio_tail) = bio;
bio->bi_next = NULL;
current->bio_tail = &bio->bi_next;
bio_list_add(current->bio_list, bio);
return;
}
/* following loop may be a bit non-obvious, and so deserves some
@ -1512,30 +1512,27 @@ void generic_make_request(struct bio *bio)
* Before entering the loop, bio->bi_next is NULL (as all callers
* ensure that) so we have a list with a single bio.
* We pretend that we have just taken it off a longer list, so
* we assign bio_list to the next (which is NULL) and bio_tail
* to &bio_list, thus initialising the bio_list of new bios to be
* we assign bio_list to a pointer to the bio_list_on_stack,
* thus initialising the bio_list of new bios to be
* added. __generic_make_request may indeed add some more bios
* through a recursive call to generic_make_request. If it
* did, we find a non-NULL value in bio_list and re-enter the loop
* from the top. In this case we really did just take the bio
* of the top of the list (no pretending) and so fixup bio_list and
* bio_tail or bi_next, and call into __generic_make_request again.
* of the top of the list (no pretending) and so remove it from
* bio_list, and call into __generic_make_request again.
*
* The loop was structured like this to make only one call to
* __generic_make_request (which is important as it is large and
* inlined) and to keep the structure simple.
*/
BUG_ON(bio->bi_next);
bio_list_init(&bio_list_on_stack);
current->bio_list = &bio_list_on_stack;
do {
current->bio_list = bio->bi_next;
if (bio->bi_next == NULL)
current->bio_tail = &current->bio_list;
else
bio->bi_next = NULL;
__generic_make_request(bio);
bio = current->bio_list;
bio = bio_list_pop(current->bio_list);
} while (bio);
current->bio_tail = NULL; /* deactivate */
current->bio_list = NULL; /* deactivate */
}
EXPORT_SYMBOL(generic_make_request);

4
include/linux/sched.h
View file

@ -97,7 +97,7 @@ struct sched_param {
struct exec_domain;
struct futex_pi_state;
struct robust_list_head;
struct bio;
struct bio_list;
struct fs_struct;
struct bts_context;
struct perf_event_context;
@ -1466,7 +1466,7 @@ struct task_struct {
void *journal_info;
/* stacked block device info */
struct bio *bio_list, **bio_tail;
struct bio_list *bio_list;
/* VM state */
struct reclaim_state *reclaim_state;