Line data    Source code

       1             : /* SPDX-License-Identifier: GPL-2.0 */
       2             : #ifndef _LINUX_SHRINKER_H
       3             : #define _LINUX_SHRINKER_H
       4             : 
       5             : #include <linux/atomic.h>
       6             : #include <linux/types.h>
       7             : 
       8             : /*
       9             :  * This struct is used to pass information from page reclaim to the shrinkers.
      10             :  * We consolidate the values for easier extension later.
      11             :  *
      12             :  * The 'gfpmask' refers to the allocation we are currently trying to
      13             :  * fulfil.
      14             :  */
      15             : struct shrink_control {
      16             :         gfp_t gfp_mask;
      17             : 
      18             :         /* current node being shrunk (for NUMA aware shrinkers) */
      19             :         int nid;
      20             : 
      21             :         /*
      22             :          * How many objects scan_objects should scan and try to reclaim.
      23             :          * This is reset before every call, so it is safe for callees
      24             :          * to modify.
      25             :          */
      26             :         unsigned long nr_to_scan;
      27             : 
      28             :         /*
      29             :          * How many objects did scan_objects process?
      30             :          * This defaults to nr_to_scan before every call, but the callee
      31             :          * should track its actual progress.
      32             :          */
      33             :         unsigned long nr_scanned;
      34             : 
      35             :         /* current memcg being shrunk (for memcg aware shrinkers) */
      36             :         struct mem_cgroup *memcg;
      37             : };
      38             : 
      39             : #define SHRINK_STOP (~0UL)
      40             : #define SHRINK_EMPTY (~0UL - 1)
      41             : /*
      42             :  * A callback you can register to apply pressure to ageable caches.
      43             :  *
      44             :  * @count_objects should return the number of freeable items in the cache. If
      45             :  * there are no objects to free, it should return SHRINK_EMPTY, while 0 is
      46             :  * returned in cases of the number of freeable items cannot be determined
      47             :  * or shrinker should skip this cache for this time (e.g., their number
      48             :  * is below shrinkable limit). No deadlock checks should be done during the
      49             :  * count callback - the shrinker relies on aggregating scan counts that couldn't
      50             :  * be executed due to potential deadlocks to be run at a later call when the
      51             :  * deadlock condition is no longer pending.
      52             :  *
      53             :  * @scan_objects will only be called if @count_objects returned a non-zero
      54             :  * value for the number of freeable objects. The callout should scan the cache
      55             :  * and attempt to free items from the cache. It should then return the number
      56             :  * of objects freed during the scan, or SHRINK_STOP if progress cannot be made
      57             :  * due to potential deadlocks. If SHRINK_STOP is returned, then no further
      58             :  * attempts to call the @scan_objects will be made from the current reclaim
      59             :  * context.
      60             :  *
      61             :  * @flags determine the shrinker abilities, like numa awareness
      62             :  */
      63             : struct shrinker {
      64             :         unsigned long (*count_objects)(struct shrinker *,
      65             :                                        struct shrink_control *sc);
      66             :         unsigned long (*scan_objects)(struct shrinker *,
      67             :                                       struct shrink_control *sc);
      68             : 
      69             :         long batch;     /* reclaim batch size, 0 = default */
      70             :         int seeks;      /* seeks to recreate an obj */
      71             :         unsigned flags;
      72             : 
      73             :         /* These are for internal use */
      74             :         struct list_head list;
      75             : #ifdef CONFIG_MEMCG
      76             :         /* ID in shrinker_idr */
      77             :         int id;
      78             : #endif
      79             : #ifdef CONFIG_SHRINKER_DEBUG
      80             :         int debugfs_id;
      81             :         const char *name;
      82             :         struct dentry *debugfs_entry;
      83             : #endif
      84             :         /* objs pending delete, per node */
      85             :         atomic_long_t *nr_deferred;
      86             : };
      87             : #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
      88             : 
      89             : /* Flags */
      90             : #define SHRINKER_REGISTERED     (1 << 0)
      91             : #define SHRINKER_NUMA_AWARE     (1 << 1)
      92             : #define SHRINKER_MEMCG_AWARE    (1 << 2)
      93             : /*
      94             :  * It just makes sense when the shrinker is also MEMCG_AWARE for now,
      95             :  * non-MEMCG_AWARE shrinker should not have this flag set.
      96             :  */
      97             : #define SHRINKER_NONSLAB        (1 << 3)
      98             : 
      99             : extern int __printf(2, 3) prealloc_shrinker(struct shrinker *shrinker,
     100             :                                             const char *fmt, ...);
     101             : extern void register_shrinker_prepared(struct shrinker *shrinker);
     102             : extern int __printf(2, 3) register_shrinker(struct shrinker *shrinker,
     103             :                                             const char *fmt, ...);
     104             : extern void unregister_shrinker(struct shrinker *shrinker);
     105             : extern void free_prealloced_shrinker(struct shrinker *shrinker);
     106             : extern void synchronize_shrinkers(void);
     107             : 
     108             : #ifdef CONFIG_SHRINKER_DEBUG
     109             : extern int shrinker_debugfs_add(struct shrinker *shrinker);
     110             : extern struct dentry *shrinker_debugfs_detach(struct shrinker *shrinker,
     111             :                                               int *debugfs_id);
     112             : extern void shrinker_debugfs_remove(struct dentry *debugfs_entry,
     113             :                                     int debugfs_id);
     114             : extern int __printf(2, 3) shrinker_debugfs_rename(struct shrinker *shrinker,
     115             :                                                   const char *fmt, ...);
     116             : #else /* CONFIG_SHRINKER_DEBUG */
     117             : static inline int shrinker_debugfs_add(struct shrinker *shrinker)
     118             : {
     119             :         return 0;
     120             : }
     121             : static inline struct dentry *shrinker_debugfs_detach(struct shrinker *shrinker,
     122             :                                                      int *debugfs_id)
     123             : {
     124           5 :         *debugfs_id = -1;
     125             :         return NULL;
     126             : }
     127             : static inline void shrinker_debugfs_remove(struct dentry *debugfs_entry,
     128             :                                            int debugfs_id)
     129             : {
     130             : }
     131             : static inline __printf(2, 3)
     132             : int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
     133             : {
     134             :         return 0;
     135             : }
     136             : #endif /* CONFIG_SHRINKER_DEBUG */
     137             : #endif /* _LINUX_SHRINKER_H */