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09f363c736
The callback must not return -1 when nr_to_scan is zero. Fix the bug in fs/super.c and add this requirement to the callback specification. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: Dave Chinner <david@fromorbit.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
44 lines
1.5 KiB
C
44 lines
1.5 KiB
C
#ifndef _LINUX_SHRINKER_H
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#define _LINUX_SHRINKER_H
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/*
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* This struct is used to pass information from page reclaim to the shrinkers.
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* We consolidate the values for easier extention later.
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*/
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struct shrink_control {
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gfp_t gfp_mask;
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/* How many slab objects shrinker() should scan and try to reclaim */
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unsigned long nr_to_scan;
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};
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/*
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* A callback you can register to apply pressure to ageable caches.
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*
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* 'sc' is passed shrink_control which includes a count 'nr_to_scan'
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* and a 'gfpmask'. It should look through the least-recently-used
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* 'nr_to_scan' entries and attempt to free them up. It should return
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* the number of objects which remain in the cache. If it returns -1, it means
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* it cannot do any scanning at this time (eg. there is a risk of deadlock).
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* The callback must not return -1 if nr_to_scan is zero.
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*
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* The 'gfpmask' refers to the allocation we are currently trying to
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* fulfil.
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*
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* Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
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* querying the cache size, so a fastpath for that case is appropriate.
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*/
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struct shrinker {
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int (*shrink)(struct shrinker *, struct shrink_control *sc);
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int seeks; /* seeks to recreate an obj */
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long batch; /* reclaim batch size, 0 = default */
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/* These are for internal use */
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struct list_head list;
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long nr; /* objs pending delete */
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};
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#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
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extern void register_shrinker(struct shrinker *);
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extern void unregister_shrinker(struct shrinker *);
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#endif
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