AcoSail/kernel_optimize_test
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Merge branch 'for-linus' of git://git.kernel.dk/data/git/linux-2.6-block

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* 'for-linus' of git://git.kernel.dk/data/git/linux-2.6-block:
  Fix compile/link of init/do_mounts.c with !CONFIG_BLOCK
  When stacked block devices are in-use (e.g. md or dm), the recursive calls
This commit is contained in:
Linus Torvalds 2007-05-11 09:58:49 -07:00
commit cabca0cb0d
3 changed files with 61 additions and 2 deletions
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53
block/ll_rw_blk.c
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@ -3116,7 +3116,7 @@ static inline int should_fail_request(struct bio *bio)
* bi_sector for remaps as it sees fit. So the values of these fields
* should NOT be depended on after the call to generic_make_request.
*/
void generic_make_request(struct bio *bio)
static inline void __generic_make_request(struct bio *bio)
{
request_queue_t *q;
sector_t maxsector;
@ -3215,6 +3215,57 @@ void generic_make_request(struct bio *bio)
} while (ret);
}
/*
* 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
* submited by a make_request_fn function.
* current->bio_tail 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
* at the tail
*/
void generic_make_request(struct bio *bio)
{
if (current->bio_tail) {
/* make_request is active */
*(current->bio_tail) = bio;
bio->bi_next = NULL;
current->bio_tail = &bio->bi_next;
return;
}
/* following loop may be a bit non-obvious, and so deserves some
* explanation.
* 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
* 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.
*
* 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);
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;
} while (bio);
current->bio_tail = NULL; /* deactivate */
}
EXPORT_SYMBOL(generic_make_request);
/**

6
include/linux/genhd.h
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@ -434,6 +434,10 @@ static inline struct block_device *bdget_disk(struct gendisk *disk, int index)
#endif
#endif
#else /* CONFIG_BLOCK */
static inline void printk_all_partitions(void) { }
#endif /* CONFIG_BLOCK */
#endif

4
include/linux/sched.h
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@ -88,6 +88,7 @@ struct sched_param {
struct exec_domain;
struct futex_pi_state;
struct bio;
/*
* List of flags we want to share for kernel threads,
@ -1016,6 +1017,9 @@ struct task_struct {
/* journalling filesystem info */
void *journal_info;
/* stacked block device info */
struct bio *bio_list, **bio_tail;
/* VM state */
struct reclaim_state *reclaim_state;