/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_COMPACTION_H
#define _LINUX_COMPACTION_H

/*
 * Determines how hard direct compaction should try to succeed.
 * Lower value means higher priority, analogically to reclaim priority.
 */
enum compact_priority {
        COMPACT_PRIO_SYNC_FULL,
        MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL,
        COMPACT_PRIO_SYNC_LIGHT,
        MIN_COMPACT_COSTLY_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
        DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
        COMPACT_PRIO_ASYNC,
        INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC
};

/* Return values for compact_zone() and try_to_compact_pages() */
/* When adding new states, please adjust include/trace/events/compaction.h */
enum compact_result {
        /* For more detailed tracepoint output - internal to compaction */
        COMPACT_NOT_SUITABLE_ZONE,
        /*
         * compaction didn't start as it was not possible or direct reclaim
         * was more suitable
         */
        COMPACT_SKIPPED,
        /* compaction didn't start as it was deferred due to past failures */
        COMPACT_DEFERRED,

        /* compaction not active last round */
        COMPACT_INACTIVE = COMPACT_DEFERRED,

        /* For more detailed tracepoint output - internal to compaction */
        COMPACT_NO_SUITABLE_PAGE,
        /* compaction should continue to another pageblock */
        COMPACT_CONTINUE,

        /*
         * The full zone was compacted scanned but wasn't successfull to compact
         * suitable pages.
         */
        COMPACT_COMPLETE,
        /*
         * direct compaction has scanned part of the zone but wasn't successfull
         * to compact suitable pages.
         */
        COMPACT_PARTIAL_SKIPPED,

        /* compaction terminated prematurely due to lock contentions */
        COMPACT_CONTENDED,

        /*
         * direct compaction terminated after concluding that the allocation
         * should now succeed
         */
        COMPACT_SUCCESS,
};

struct alloc_context; /* in mm/internal.h */

/*
 * Number of free order-0 pages that should be available above given watermark
 * to make sure compaction has reasonable chance of not running out of free
 * pages that it needs to isolate as migration target during its work.
 */
static inline unsigned long compact_gap(unsigned int order)
{
        /*
         * Although all the isolations for migration are temporary, compaction
         * free scanner may have up to 1 << order pages on its list and then
         * try to split an (order - 1) free page. At that point, a gap of
         * 1 << order might not be enough, so it's safer to require twice that
         * amount. Note that the number of pages on the list is also
         * effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum
         * that the migrate scanner can have isolated on migrate list, and free
         * scanner is only invoked when the number of isolated free pages is
         * lower than that. But it's not worth to complicate the formula here
         * as a bigger gap for higher orders than strictly necessary can also
         * improve chances of compaction success.
         */
        return 2UL << order;
}

#ifdef CONFIG_COMPACTION
extern int sysctl_compact_memory;
extern int sysctl_compaction_handler(struct ctl_table *table, int write,
                        void __user *buffer, size_t *length, loff_t *ppos);
extern int sysctl_extfrag_threshold;
extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
                        void __user *buffer, size_t *length, loff_t *ppos);
extern int sysctl_compact_unevictable_allowed;

extern int fragmentation_index(struct zone *zone, unsigned int order);
extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
                unsigned int order, unsigned int alloc_flags,
                const struct alloc_context *ac, enum compact_priority prio);
extern void reset_isolation_suitable(pg_data_t *pgdat);
extern enum compact_result compaction_suitable(struct zone *zone, int order,
                unsigned int alloc_flags, int classzone_idx);

extern void defer_compaction(struct zone *zone, int order);
extern bool compaction_deferred(struct zone *zone, int order);
extern void compaction_defer_reset(struct zone *zone, int order,
                                bool alloc_success);
extern bool compaction_restarting(struct zone *zone, int order);

/* Compaction has made some progress and retrying makes sense */
static inline bool compaction_made_progress(enum compact_result result)
{
        /*
         * Even though this might sound confusing this in fact tells us
         * that the compaction successfully isolated and migrated some
         * pageblocks.
         */
        if (result == COMPACT_SUCCESS)
                return true;

        return false;
}

/* Compaction has failed and it doesn't make much sense to keep retrying. */
static inline bool compaction_failed(enum compact_result result)
{
        /* All zones were scanned completely and still not result. */
        if (result == COMPACT_COMPLETE)
                return true;

        return false;
}

/*
 * Compaction  has backed off for some reason. It might be throttling or
 * lock contention. Retrying is still worthwhile.
 */
static inline bool compaction_withdrawn(enum compact_result result)
{
        /*
         * Compaction backed off due to watermark checks for order-0
         * so the regular reclaim has to try harder and reclaim something.
         */
        if (result == COMPACT_SKIPPED)
                return true;

        /*
         * If compaction is deferred for high-order allocations, it is
         * because sync compaction recently failed. If this is the case
         * and the caller requested a THP allocation, we do not want
         * to heavily disrupt the system, so we fail the allocation
         * instead of entering direct reclaim.
         */
        if (result == COMPACT_DEFERRED)
                return true;

        /*
         * If compaction in async mode encounters contention or blocks higher
         * priority task we back off early rather than cause stalls.
         */
        if (result == COMPACT_CONTENDED)
                return true;

        /*
         * Page scanners have met but we haven't scanned full zones so this
         * is a back off in fact.
         */
        if (result == COMPACT_PARTIAL_SKIPPED)
                return true;

        return false;
}


bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
                                        int alloc_flags);

extern int kcompactd_run(int nid);
extern void kcompactd_stop(int nid);
extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);

#else
static inline void reset_isolation_suitable(pg_data_t *pgdat)
{
}

static inline enum compact_result compaction_suitable(struct zone *zone, int order,
                                        int alloc_flags, int classzone_idx)
{
        return COMPACT_SKIPPED;
}

static inline void defer_compaction(struct zone *zone, int order)
{
}

static inline bool compaction_deferred(struct zone *zone, int order)
{
        return true;
}

static inline bool compaction_made_progress(enum compact_result result)
{
        return false;
}

static inline bool compaction_failed(enum compact_result result)
{
        return false;
}

static inline bool compaction_withdrawn(enum compact_result result)
{
        return true;
}

static inline int kcompactd_run(int nid)
{
        return 0;
}
static inline void kcompactd_stop(int nid)
{
}

static inline void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
{
}

#endif /* CONFIG_COMPACTION */

#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
struct node;
extern int compaction_register_node(struct node *node);
extern void compaction_unregister_node(struct node *node);

#else

static inline int compaction_register_node(struct node *node)
{
        return 0;
}

static inline void compaction_unregister_node(struct node *node)
{
}
#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */

#endif /* _LINUX_COMPACTION_H */