linux-hardened/include/linux/shrinker.h
Minchan Kim 8e125cd855 vmscan: remove obsolete shrink_control comment
09f363c7 ("vmscan: fix shrinker callback bug in fs/super.c") fixed a
shrinker callback which was returning -1 when nr_to_scan is zero, which
caused excessive slab scanning.  But 635697c6 ("vmscan: fix initial
shrinker size handling") fixed the problem, again so we can freely return
-1 although nr_to_scan is zero.  So let's revert 09f363c7 because the
comment added in 09f363c7 made an unnecessary rule.

Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-31 18:42:43 -07:00

42 lines
1.4 KiB
C

#ifndef _LINUX_SHRINKER_H
#define _LINUX_SHRINKER_H
/*
* This struct is used to pass information from page reclaim to the shrinkers.
* We consolidate the values for easier extention later.
*/
struct shrink_control {
gfp_t gfp_mask;
/* How many slab objects shrinker() should scan and try to reclaim */
unsigned long nr_to_scan;
};
/*
* A callback you can register to apply pressure to ageable caches.
*
* 'sc' is passed shrink_control which includes a count 'nr_to_scan'
* and a 'gfpmask'. It should look through the least-recently-used
* 'nr_to_scan' entries and attempt to free them up. It should return
* the number of objects which remain in the cache. If it returns -1, it means
* it cannot do any scanning at this time (eg. there is a risk of deadlock).
*
* The 'gfpmask' refers to the allocation we are currently trying to
* fulfil.
*
* Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
* querying the cache size, so a fastpath for that case is appropriate.
*/
struct shrinker {
int (*shrink)(struct shrinker *, struct shrink_control *sc);
int seeks; /* seeks to recreate an obj */
long batch; /* reclaim batch size, 0 = default */
/* These are for internal use */
struct list_head list;
atomic_long_t nr_in_batch; /* objs pending delete */
};
#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
extern void register_shrinker(struct shrinker *);
extern void unregister_shrinker(struct shrinker *);
#endif