From 119e9db233ad0f4cbd4cfb9f9385a7bca378b37d Mon Sep 17 00:00:00 2001 From: Zeng Chi Date: Mon, 21 Sep 2026 18:24:42 +0800 Subject: KVM: Don't pre-reserve xarray entries when storing empty/NULL attributes Skip the xarray reservation loop when clearing all memory attributes, as storing NULL only erases the entry and never needs to allocate, so no reservation (and no cleanup of a failed one) is required in that case. Suggested-by: Sean Christopherson Cc: David Ballesteros Signed-off-by: Zeng Chi Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com [sean: split to separate patch] Signed-off-by: Sean Christopherson --- drivers/md/dm-cache-background-tracker.c | 239 +++++++++++++++++++++++++++++++ 1 file changed, 239 insertions(+) create mode 100644 drivers/md/dm-cache-background-tracker.c (limited to 'drivers/md/dm-cache-background-tracker.c') diff --git a/drivers/md/dm-cache-background-tracker.c b/drivers/md/dm-cache-background-tracker.c new file mode 100644 index 000000000..2ca3a3e2e --- /dev/null +++ b/drivers/md/dm-cache-background-tracker.c @@ -0,0 +1,239 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2017 Red Hat. All rights reserved. + * + * This file is released under the GPL. + */ + +#include "dm-cache-background-tracker.h" + +/*----------------------------------------------------------------*/ + +#define DM_MSG_PREFIX "dm-background-tracker" + +struct background_tracker { + unsigned int max_work; + atomic_t pending_promotes; + atomic_t pending_writebacks; + atomic_t pending_demotes; + + struct list_head issued; + struct list_head queued; + struct rb_root pending; +}; + +struct kmem_cache *btracker_work_cache = NULL; + +struct background_tracker *btracker_create(unsigned int max_work) +{ + struct background_tracker *b = kmalloc_obj(*b); + + if (!b) { + DMERR("couldn't create background_tracker"); + return NULL; + } + + b->max_work = max_work; + atomic_set(&b->pending_promotes, 0); + atomic_set(&b->pending_writebacks, 0); + atomic_set(&b->pending_demotes, 0); + + INIT_LIST_HEAD(&b->issued); + INIT_LIST_HEAD(&b->queued); + + b->pending = RB_ROOT; + + return b; +} +EXPORT_SYMBOL_GPL(btracker_create); + +void btracker_destroy(struct background_tracker *b) +{ + struct bt_work *w, *tmp; + + BUG_ON(!list_empty(&b->issued)); + list_for_each_entry_safe (w, tmp, &b->queued, list) { + list_del(&w->list); + kmem_cache_free(btracker_work_cache, w); + } + + kfree(b); +} +EXPORT_SYMBOL_GPL(btracker_destroy); + +static int cmp_oblock(dm_oblock_t lhs, dm_oblock_t rhs) +{ + if (from_oblock(lhs) < from_oblock(rhs)) + return -1; + + if (from_oblock(rhs) < from_oblock(lhs)) + return 1; + + return 0; +} + +static bool __insert_pending(struct background_tracker *b, + struct bt_work *nw) +{ + int cmp; + struct bt_work *w; + struct rb_node **new = &b->pending.rb_node, *parent = NULL; + + while (*new) { + w = container_of(*new, struct bt_work, node); + + parent = *new; + cmp = cmp_oblock(w->work.oblock, nw->work.oblock); + if (cmp < 0) + new = &((*new)->rb_left); + + else if (cmp > 0) + new = &((*new)->rb_right); + + else + /* already present */ + return false; + } + + rb_link_node(&nw->node, parent, new); + rb_insert_color(&nw->node, &b->pending); + + return true; +} + +static struct bt_work *__find_pending(struct background_tracker *b, + dm_oblock_t oblock) +{ + int cmp; + struct bt_work *w; + struct rb_node **new = &b->pending.rb_node; + + while (*new) { + w = container_of(*new, struct bt_work, node); + + cmp = cmp_oblock(w->work.oblock, oblock); + if (cmp < 0) + new = &((*new)->rb_left); + + else if (cmp > 0) + new = &((*new)->rb_right); + + else + break; + } + + return *new ? w : NULL; +} + + +static void update_stats(struct background_tracker *b, struct policy_work *w, int delta) +{ + switch (w->op) { + case POLICY_PROMOTE: + atomic_add(delta, &b->pending_promotes); + break; + + case POLICY_DEMOTE: + atomic_add(delta, &b->pending_demotes); + break; + + case POLICY_WRITEBACK: + atomic_add(delta, &b->pending_writebacks); + break; + } +} + +unsigned int btracker_nr_demotions_queued(struct background_tracker *b) +{ + return atomic_read(&b->pending_demotes); +} +EXPORT_SYMBOL_GPL(btracker_nr_demotions_queued); + +static bool max_work_reached(struct background_tracker *b) +{ + return atomic_read(&b->pending_promotes) + + atomic_read(&b->pending_writebacks) + + atomic_read(&b->pending_demotes) >= b->max_work; +} + +static struct bt_work *alloc_work(struct background_tracker *b) +{ + if (max_work_reached(b)) + return NULL; + + return kmem_cache_alloc(btracker_work_cache, GFP_NOWAIT); +} + +int btracker_queue(struct background_tracker *b, + struct policy_work *work, + struct policy_work **pwork) +{ + struct bt_work *w; + + if (pwork) + *pwork = NULL; + + w = alloc_work(b); + if (!w) + return -ENOMEM; + + memcpy(&w->work, work, sizeof(*work)); + + if (!__insert_pending(b, w)) { + /* + * There was a race, we'll just ignore this second + * bit of work for the same oblock. + */ + kmem_cache_free(btracker_work_cache, w); + return -EINVAL; + } + + if (pwork) { + *pwork = &w->work; + list_add(&w->list, &b->issued); + } else + list_add(&w->list, &b->queued); + update_stats(b, &w->work, 1); + + return 0; +} +EXPORT_SYMBOL_GPL(btracker_queue); + +/* + * Returns -ENODATA if there's no work. + */ +int btracker_issue(struct background_tracker *b, struct policy_work **work) +{ + struct bt_work *w; + + if (list_empty(&b->queued)) + return -ENODATA; + + w = list_first_entry(&b->queued, struct bt_work, list); + list_move(&w->list, &b->issued); + *work = &w->work; + + return 0; +} +EXPORT_SYMBOL_GPL(btracker_issue); + +void btracker_complete(struct background_tracker *b, + struct policy_work *op) +{ + struct bt_work *w = container_of(op, struct bt_work, work); + + update_stats(b, &w->work, -1); + rb_erase(&w->node, &b->pending); + list_del(&w->list); + kmem_cache_free(btracker_work_cache, w); +} +EXPORT_SYMBOL_GPL(btracker_complete); + +bool btracker_promotion_already_present(struct background_tracker *b, + dm_oblock_t oblock) +{ + return __find_pending(b, oblock) != NULL; +} +EXPORT_SYMBOL_GPL(btracker_promotion_already_present); + +/*----------------------------------------------------------------*/ -- cgit v1.3.1