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Message-Id: <20250605142306.1930831-11-dongsheng.yang@linux.dev>
Date: Thu, 5 Jun 2025 14:23:05 +0000
From: Dongsheng Yang <dongsheng.yang@...ux.dev>
To: mpatocka@...hat.com,
agk@...hat.com,
snitzer@...nel.org,
axboe@...nel.dk,
hch@....de,
dan.j.williams@...el.com,
Jonathan.Cameron@...wei.com
Cc: linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-cxl@...r.kernel.org,
nvdimm@...ts.linux.dev,
dm-devel@...ts.linux.dev,
Dongsheng Yang <dongsheng.yang@...ux.dev>
Subject: [RFC PATCH 10/11] dm-pcache: add cache core
Add cache.c and cache.h that introduce the top-level
“struct pcache_cache”. This object glues together the backing block
device, the persistent-memory cache device, segment array, RB-tree
indexes, and the background workers for write-back and garbage
collection.
* Persistent metadata
- pcache_cache_info tracks options such as cache mode, data-crc flag
and GC threshold, written atomically with CRC+sequence.
- key_tail and dirty_tail positions are double-buffered and recovered
at mount time.
* Segment management
- kvcalloc()’d array of pcache_cache_segment objects, bitmap for fast
allocation, refcounts and generation numbers so GC can invalidate
old extents safely.
- First segment hosts a pcache_cache_ctrl block shared by all
threads.
* Request path hooks
- pcache_cache_handle_req() dispatches READ, WRITE and FLUSH bios to
the engines added in earlier patches.
- Per-CPU data_heads support lock-free allocation of space for new
writes.
* Background workers
- Delayed work items for write-back (5 s) and GC (5 s).
- clean_work removes stale keys after segments are reclaimed.
* Lifecycle helpers
- pcache_cache_start()/stop() bring the cache online, replay keys,
start workers, and flush everything on shutdown.
With this piece in place dm-pcache has a fully initialised cache object
capable of serving I/O and maintaining its on-disk structures.
Signed-off-by: Dongsheng Yang <dongsheng.yang@...ux.dev>
---
drivers/md/dm-pcache/cache.c | 443 ++++++++++++++++++++++++++
drivers/md/dm-pcache/cache.h | 601 +++++++++++++++++++++++++++++++++++
2 files changed, 1044 insertions(+)
create mode 100644 drivers/md/dm-pcache/cache.c
create mode 100644 drivers/md/dm-pcache/cache.h
diff --git a/drivers/md/dm-pcache/cache.c b/drivers/md/dm-pcache/cache.c
new file mode 100644
index 000000000000..af2e59f16be8
--- /dev/null
+++ b/drivers/md/dm-pcache/cache.c
@@ -0,0 +1,443 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/blk_types.h>
+
+#include "cache.h"
+#include "cache_dev.h"
+#include "backing_dev.h"
+#include "dm_pcache.h"
+
+static inline struct pcache_cache_info *get_cache_info_addr(struct pcache_cache *cache)
+{
+ return cache->cache_info_addr + cache->info_index;
+}
+
+static void cache_info_write(struct pcache_cache *cache)
+{
+ struct pcache_cache_info *cache_info = &cache->cache_info;
+
+ cache_info->header.seq++;
+ cache_info->header.crc = pcache_meta_crc(&cache_info->header,
+ sizeof(struct pcache_cache_info));
+
+ memcpy_flushcache(get_cache_info_addr(cache), cache_info,
+ sizeof(struct pcache_cache_info));
+
+ cache->info_index = (cache->info_index + 1) % PCACHE_META_INDEX_MAX;
+}
+
+static void cache_info_init_default(struct pcache_cache *cache);
+static int cache_info_init(struct pcache_cache *cache, struct pcache_cache_options *opts)
+{
+ struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
+ struct pcache_cache_info *cache_info_addr;
+
+ cache_info_addr = pcache_meta_find_latest(&cache->cache_info_addr->header,
+ sizeof(struct pcache_cache_info),
+ PCACHE_CACHE_INFO_SIZE,
+ &cache->cache_info);
+ if (IS_ERR(cache_info_addr))
+ return PTR_ERR(cache_info_addr);
+
+ if (cache_info_addr) {
+ if (opts->data_crc !=
+ (cache->cache_info.flags & PCACHE_CACHE_FLAGS_DATA_CRC)) {
+ pcache_dev_err(pcache, "invalid option for data_crc: %s, expected: %s",
+ opts->data_crc ? "true" : "false",
+ cache->cache_info.flags & PCACHE_CACHE_FLAGS_DATA_CRC ? "true" : "false");
+ return -EINVAL;
+ }
+
+ return 0;
+ }
+
+ /* init cache_info for new cache */
+ cache_info_init_default(cache);
+
+ cache->cache_info.flags &= ~PCACHE_CACHE_FLAGS_CACHE_MODE_MASK;
+ cache->cache_info.flags |= FIELD_PREP(PCACHE_CACHE_FLAGS_CACHE_MODE_MASK, opts->cache_mode);
+
+ if (opts->data_crc)
+ cache->cache_info.flags |= PCACHE_CACHE_FLAGS_DATA_CRC;
+
+ return 0;
+}
+
+static void cache_info_set_gc_percent(struct pcache_cache_info *cache_info, u8 percent)
+{
+ cache_info->flags &= ~PCACHE_CACHE_FLAGS_GC_PERCENT_MASK;
+ cache_info->flags |= FIELD_PREP(PCACHE_CACHE_FLAGS_GC_PERCENT_MASK, percent);
+}
+
+int pcache_cache_set_gc_percent(struct pcache_cache *cache, u8 percent)
+{
+ if (percent > PCACHE_CACHE_GC_PERCENT_MAX || percent < PCACHE_CACHE_GC_PERCENT_MIN)
+ return -EINVAL;
+
+ mutex_lock(&cache->cache_info_lock);
+ cache_info_set_gc_percent(&cache->cache_info, percent);
+
+ cache_info_write(cache);
+ mutex_unlock(&cache->cache_info_lock);
+
+ return 0;
+}
+
+void cache_pos_encode(struct pcache_cache *cache,
+ struct pcache_cache_pos_onmedia *pos_onmedia_base,
+ struct pcache_cache_pos *pos, u64 seq, u32 *index)
+{
+ struct pcache_cache_pos_onmedia pos_onmedia;
+ struct pcache_cache_pos_onmedia *pos_onmedia_addr = pos_onmedia_base + *index;
+
+ pos_onmedia.cache_seg_id = pos->cache_seg->cache_seg_id;
+ pos_onmedia.seg_off = pos->seg_off;
+ pos_onmedia.header.seq = seq;
+ pos_onmedia.header.crc = cache_pos_onmedia_crc(&pos_onmedia);
+
+ memcpy_flushcache(pos_onmedia_addr, &pos_onmedia, sizeof(struct pcache_cache_pos_onmedia));
+ pmem_wmb();
+
+ *index = (*index + 1) % PCACHE_META_INDEX_MAX;
+}
+
+int cache_pos_decode(struct pcache_cache *cache,
+ struct pcache_cache_pos_onmedia *pos_onmedia,
+ struct pcache_cache_pos *pos, u64 *seq, u32 *index)
+{
+ struct pcache_cache_pos_onmedia latest, *latest_addr;
+
+ latest_addr = pcache_meta_find_latest(&pos_onmedia->header,
+ sizeof(struct pcache_cache_pos_onmedia),
+ sizeof(struct pcache_cache_pos_onmedia),
+ &latest);
+ if (IS_ERR(latest_addr))
+ return PTR_ERR(latest_addr);
+
+ if (!latest_addr)
+ return -EIO;
+
+ pos->cache_seg = &cache->segments[latest.cache_seg_id];
+ pos->seg_off = latest.seg_off;
+ *seq = latest.header.seq;
+ *index = (latest_addr - pos_onmedia);
+
+ return 0;
+}
+
+static inline void cache_info_set_seg_id(struct pcache_cache *cache, u32 seg_id)
+{
+ cache->cache_info.seg_id = seg_id;
+}
+
+static int cache_init(struct dm_pcache *pcache)
+{
+ struct pcache_cache *cache = &pcache->cache;
+ struct pcache_backing_dev *backing_dev = &pcache->backing_dev;
+ struct pcache_cache_dev *cache_dev = &pcache->cache_dev;
+ int ret;
+
+ cache->segments = kvcalloc(cache_dev->seg_num, sizeof(struct pcache_cache_segment), GFP_KERNEL);
+ if (!cache->segments) {
+ ret = -ENOMEM;
+ goto err;
+ }
+
+ cache->seg_map = bitmap_zalloc(cache_dev->seg_num, GFP_KERNEL);
+ if (!cache->seg_map) {
+ ret = -ENOMEM;
+ goto free_segments;
+ }
+
+ cache->req_cache = KMEM_CACHE(pcache_backing_dev_req, 0);
+ if (!cache->req_cache) {
+ ret = -ENOMEM;
+ goto free_bitmap;
+ }
+
+ cache->backing_dev = backing_dev;
+ cache->cache_dev = &pcache->cache_dev;
+ cache->n_segs = cache_dev->seg_num;
+ atomic_set(&cache->gc_errors, 0);
+ spin_lock_init(&cache->seg_map_lock);
+ spin_lock_init(&cache->key_head_lock);
+
+ mutex_init(&cache->cache_info_lock);
+ mutex_init(&cache->key_tail_lock);
+ mutex_init(&cache->dirty_tail_lock);
+ mutex_init(&cache->writeback_lock);
+
+ INIT_DELAYED_WORK(&cache->writeback_work, cache_writeback_fn);
+ INIT_DELAYED_WORK(&cache->gc_work, pcache_cache_gc_fn);
+ INIT_WORK(&cache->clean_work, clean_fn);
+
+ return 0;
+
+free_bitmap:
+ bitmap_free(cache->seg_map);
+free_segments:
+ kvfree(cache->segments);
+err:
+ return ret;
+}
+
+static void cache_exit(struct pcache_cache *cache)
+{
+ kmem_cache_destroy(cache->req_cache);
+ bitmap_free(cache->seg_map);
+ kvfree(cache->segments);
+}
+
+static void cache_info_init_default(struct pcache_cache *cache)
+{
+ struct pcache_cache_info *cache_info = &cache->cache_info;
+
+ cache_info->header.seq = 0;
+ cache_info->n_segs = cache->cache_dev->seg_num;
+ cache_info_set_gc_percent(cache_info, PCACHE_CACHE_GC_PERCENT_DEFAULT);
+}
+
+static int cache_tail_init(struct pcache_cache *cache)
+{
+ struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
+ bool new_cache = !(cache->cache_info.flags & PCACHE_CACHE_FLAGS_INIT_DONE);
+ int ret;
+
+ if (new_cache) {
+ set_bit(0, cache->seg_map);
+
+ cache->key_head.cache_seg = &cache->segments[0];
+ cache->key_head.seg_off = 0;
+ cache_pos_copy(&cache->key_tail, &cache->key_head);
+ cache_pos_copy(&cache->dirty_tail, &cache->key_head);
+
+ cache_encode_dirty_tail(cache);
+ cache_encode_key_tail(cache);
+ } else {
+ if (cache_decode_key_tail(cache) || cache_decode_dirty_tail(cache)) {
+ pcache_dev_err(pcache, "Corrupted key tail or dirty tail.\n");
+ ret = -EIO;
+ goto err;
+ }
+ }
+ return 0;
+err:
+ return ret;
+}
+
+static int get_seg_id(struct pcache_cache *cache,
+ struct pcache_cache_segment *prev_cache_seg,
+ bool new_cache, u32 *seg_id)
+{
+ struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
+ struct pcache_cache_dev *cache_dev = cache->cache_dev;
+ int ret;
+
+ if (new_cache) {
+ ret = cache_dev_get_empty_segment_id(cache_dev, seg_id);
+ if (ret) {
+ pcache_dev_err(pcache, "no available segment\n");
+ goto err;
+ }
+
+ if (prev_cache_seg)
+ cache_seg_set_next_seg(prev_cache_seg, *seg_id);
+ else
+ cache_info_set_seg_id(cache, *seg_id);
+ } else {
+ if (prev_cache_seg) {
+ struct pcache_segment_info *prev_seg_info;
+
+ prev_seg_info = &prev_cache_seg->cache_seg_info;
+ if (!segment_info_has_next(prev_seg_info)) {
+ ret = -EFAULT;
+ goto err;
+ }
+ *seg_id = prev_cache_seg->cache_seg_info.next_seg;
+ } else {
+ *seg_id = cache->cache_info.seg_id;
+ }
+ }
+ return 0;
+err:
+ return ret;
+}
+
+static int cache_segs_init(struct pcache_cache *cache)
+{
+ struct pcache_cache_segment *prev_cache_seg = NULL;
+ struct pcache_cache_info *cache_info = &cache->cache_info;
+ bool new_cache = !(cache->cache_info.flags & PCACHE_CACHE_FLAGS_INIT_DONE);
+ u32 seg_id;
+ int ret;
+ u32 i;
+
+ for (i = 0; i < cache_info->n_segs; i++) {
+ ret = get_seg_id(cache, prev_cache_seg, new_cache, &seg_id);
+ if (ret)
+ goto err;
+
+ ret = cache_seg_init(cache, seg_id, i, new_cache);
+ if (ret)
+ goto err;
+
+ prev_cache_seg = &cache->segments[i];
+ }
+ return 0;
+err:
+ return ret;
+}
+
+static int cache_init_req_keys(struct pcache_cache *cache, u32 n_paral)
+{
+ struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
+ u32 n_subtrees;
+ int ret;
+ u32 i, cpu;
+
+ /* Calculate number of cache trees based on the device size */
+ n_subtrees = DIV_ROUND_UP(cache->dev_size << SECTOR_SHIFT, PCACHE_CACHE_SUBTREE_SIZE);
+ ret = cache_tree_init(cache, &cache->req_key_tree, n_subtrees);
+ if (ret)
+ goto err;
+
+ cache->n_ksets = n_paral;
+ cache->ksets = kcalloc(cache->n_ksets, PCACHE_KSET_SIZE, GFP_KERNEL);
+ if (!cache->ksets) {
+ ret = -ENOMEM;
+ goto req_tree_exit;
+ }
+
+ /*
+ * Initialize each kset with a spinlock and delayed work for flushing.
+ * Each kset is associated with one queue to ensure independent handling
+ * of cache keys across multiple queues, maximizing multiqueue concurrency.
+ */
+ for (i = 0; i < cache->n_ksets; i++) {
+ struct pcache_cache_kset *kset = get_kset(cache, i);
+
+ kset->cache = cache;
+ spin_lock_init(&kset->kset_lock);
+ INIT_DELAYED_WORK(&kset->flush_work, kset_flush_fn);
+ }
+
+ cache->data_heads = alloc_percpu(struct pcache_cache_data_head);
+ if (!cache->data_heads) {
+ ret = -ENOMEM;
+ goto free_kset;
+ }
+
+ for_each_possible_cpu(cpu) {
+ struct pcache_cache_data_head *h =
+ per_cpu_ptr(cache->data_heads, cpu);
+ h->head_pos.cache_seg = NULL;
+ }
+
+ /*
+ * Replay persisted cache keys using cache_replay.
+ * This function loads and replays cache keys from previously stored
+ * ksets, allowing the cache to restore its state after a restart.
+ */
+ ret = cache_replay(cache);
+ if (ret) {
+ pcache_dev_err(pcache, "failed to replay keys\n");
+ goto free_heads;
+ }
+
+ return 0;
+
+free_heads:
+ free_percpu(cache->data_heads);
+free_kset:
+ kfree(cache->ksets);
+req_tree_exit:
+ cache_tree_exit(&cache->req_key_tree);
+err:
+ return ret;
+}
+
+static void cache_destroy_req_keys(struct pcache_cache *cache)
+{
+ u32 i;
+
+ for (i = 0; i < cache->n_ksets; i++) {
+ struct pcache_cache_kset *kset = get_kset(cache, i);
+
+ cancel_delayed_work_sync(&kset->flush_work);
+ }
+
+ free_percpu(cache->data_heads);
+ kfree(cache->ksets);
+ cache_tree_exit(&cache->req_key_tree);
+}
+
+int pcache_cache_start(struct dm_pcache *pcache, struct pcache_cache_options *opts)
+{
+ struct pcache_backing_dev *backing_dev = &pcache->backing_dev;
+ struct pcache_cache *cache = &pcache->cache;
+ int ret;
+
+ ret = cache_init(pcache);
+ if (ret)
+ return ret;
+
+ cache->cache_info_addr = CACHE_DEV_CACHE_INFO(cache->cache_dev);
+ cache->cache_ctrl = CACHE_DEV_CACHE_CTRL(cache->cache_dev);
+ backing_dev->cache = cache;
+ cache->dev_size = backing_dev->dev_size;
+
+ ret = cache_info_init(cache, opts);
+ if (ret)
+ goto cache_exit;
+
+ ret = cache_segs_init(cache);
+ if (ret)
+ goto cache_exit;
+
+ ret = cache_tail_init(cache);
+ if (ret)
+ goto cache_exit;
+
+ ret = cache_init_req_keys(cache, num_online_cpus());
+ if (ret)
+ goto cache_exit;
+
+ ret = cache_writeback_init(cache);
+ if (ret)
+ goto destroy_keys;
+
+ cache->cache_info.flags |= PCACHE_CACHE_FLAGS_INIT_DONE;
+ cache_info_write(cache);
+ queue_delayed_work(cache_get_wq(cache), &cache->gc_work, 0);
+
+ return 0;
+
+destroy_keys:
+ cache_destroy_req_keys(cache);
+cache_exit:
+ cache_exit(cache);
+
+ return ret;
+}
+
+void pcache_cache_stop(struct dm_pcache *pcache)
+{
+ struct pcache_cache *cache = &pcache->cache;
+
+ cache_flush(cache);
+
+ cancel_delayed_work_sync(&cache->gc_work);
+ flush_work(&cache->clean_work);
+ cache_writeback_exit(cache);
+
+ if (cache->req_key_tree.n_subtrees)
+ cache_destroy_req_keys(cache);
+
+ cache_exit(cache);
+}
+
+struct workqueue_struct *cache_get_wq(struct pcache_cache *cache)
+{
+ struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
+
+ return pcache->task_wq;
+}
diff --git a/drivers/md/dm-pcache/cache.h b/drivers/md/dm-pcache/cache.h
new file mode 100644
index 000000000000..edb1f9d85c1c
--- /dev/null
+++ b/drivers/md/dm-pcache/cache.h
@@ -0,0 +1,601 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _PCACHE_CACHE_H
+#define _PCACHE_CACHE_H
+
+#include "segment.h"
+
+/* Garbage collection thresholds */
+#define PCACHE_CACHE_GC_PERCENT_MIN 0 /* Minimum GC percentage */
+#define PCACHE_CACHE_GC_PERCENT_MAX 90 /* Maximum GC percentage */
+#define PCACHE_CACHE_GC_PERCENT_DEFAULT 70 /* Default GC percentage */
+
+#define PCACHE_CACHE_SUBTREE_SIZE (4 * 1024 * 1024) /* 4MB total tree size */
+#define PCACHE_CACHE_SUBTREE_SIZE_MASK 0x3FFFFF /* Mask for tree size */
+#define PCACHE_CACHE_SUBTREE_SIZE_SHIFT 22 /* Bit shift for tree size */
+
+/* Maximum number of keys per key set */
+#define PCACHE_KSET_KEYS_MAX 128
+#define PCACHE_CACHE_SEGS_MAX (1024 * 1024) /* maximum cache size for each device is 16T */
+#define PCACHE_KSET_ONMEDIA_SIZE_MAX struct_size_t(struct pcache_cache_kset_onmedia, data, PCACHE_KSET_KEYS_MAX)
+#define PCACHE_KSET_SIZE (sizeof(struct pcache_cache_kset) + sizeof(struct pcache_cache_key_onmedia) * PCACHE_KSET_KEYS_MAX)
+
+/* Maximum number of keys to clean in one round of clean_work */
+#define PCACHE_CLEAN_KEYS_MAX 10
+
+/* Writeback and garbage collection intervals in jiffies */
+#define PCACHE_CACHE_WRITEBACK_INTERVAL (5 * HZ)
+#define PCACHE_CACHE_GC_INTERVAL (5 * HZ)
+
+/* Macro to get the cache key structure from an rb_node pointer */
+#define CACHE_KEY(node) (container_of(node, struct pcache_cache_key, rb_node))
+
+struct pcache_cache_pos_onmedia {
+ struct pcache_meta_header header;
+ __u32 cache_seg_id;
+ __u32 seg_off;
+} __packed;
+
+/* Offset and size definitions for cache segment control */
+#define PCACHE_CACHE_SEG_CTRL_OFF (PCACHE_SEG_INFO_SIZE * PCACHE_META_INDEX_MAX)
+#define PCACHE_CACHE_SEG_CTRL_SIZE (4 * PCACHE_KB)
+
+struct pcache_cache_seg_gen {
+ struct pcache_meta_header header;
+ __u64 gen;
+} __packed;
+
+/* Control structure for cache segments */
+struct pcache_cache_seg_ctrl {
+ struct pcache_cache_seg_gen gen[PCACHE_META_INDEX_MAX];
+ __u64 res[64];
+} __packed;
+
+#define PCACHE_CACHE_FLAGS_DATA_CRC BIT(0)
+#define PCACHE_CACHE_FLAGS_INIT_DONE BIT(1)
+
+#define PCACHE_CACHE_FLAGS_CACHE_MODE_MASK GENMASK(5, 2)
+#define PCACHE_CACHE_MODE_WRITEBACK 0
+#define PCACHE_CACHE_MODE_WRITETHROUGH 1
+#define PCACHE_CACHE_MODE_WRITEAROUND 2
+#define PCACHE_CACHE_MODE_WRITEONLY 3
+
+#define PCACHE_CACHE_FLAGS_GC_PERCENT_MASK GENMASK(12, 6)
+
+struct pcache_cache_info {
+ struct pcache_meta_header header;
+ __u32 seg_id;
+ __u32 n_segs;
+ __u32 flags;
+ __u32 reserved;
+} __packed;
+
+struct pcache_cache_pos {
+ struct pcache_cache_segment *cache_seg;
+ u32 seg_off;
+};
+
+struct pcache_cache_segment {
+ struct pcache_cache *cache;
+ u32 cache_seg_id; /* Index in cache->segments */
+ struct pcache_segment segment;
+ atomic_t refs;
+
+ struct pcache_segment_info cache_seg_info;
+ struct mutex info_lock;
+ u32 info_index;
+
+ spinlock_t gen_lock;
+ u64 gen;
+ u64 gen_seq;
+ u32 gen_index;
+
+ struct pcache_cache_seg_ctrl *cache_seg_ctrl;
+ struct mutex ctrl_lock;
+};
+
+/* rbtree for cache entries */
+struct pcache_cache_subtree {
+ struct rb_root root;
+ spinlock_t tree_lock;
+};
+
+struct pcache_cache_tree {
+ struct pcache_cache *cache;
+ u32 n_subtrees;
+ struct kmem_cache *key_cache;
+ struct pcache_cache_subtree *subtrees;
+};
+
+struct pcache_cache_key {
+ struct pcache_cache_tree *cache_tree;
+ struct pcache_cache_subtree *cache_subtree;
+ struct kref ref;
+ struct rb_node rb_node;
+ struct list_head list_node;
+ u64 off;
+ u32 len;
+ u32 flags;
+ struct pcache_cache_pos cache_pos;
+ u64 seg_gen;
+};
+
+#define PCACHE_CACHE_KEY_FLAGS_EMPTY BIT(0)
+#define PCACHE_CACHE_KEY_FLAGS_CLEAN BIT(1)
+
+struct pcache_cache_key_onmedia {
+ __u64 off;
+ __u32 len;
+ __u32 flags;
+ __u32 cache_seg_id;
+ __u32 cache_seg_off;
+ __u64 seg_gen;
+ __u32 data_crc;
+ __u32 reserved;
+} __packed;
+
+struct pcache_cache_kset_onmedia {
+ __u32 crc;
+ union {
+ __u32 key_num;
+ __u32 next_cache_seg_id;
+ };
+ __u64 magic;
+ __u64 flags;
+ struct pcache_cache_key_onmedia data[];
+} __packed;
+
+struct pcache_cache {
+ struct pcache_backing_dev *backing_dev;
+ struct pcache_cache_dev *cache_dev;
+ struct pcache_cache_ctrl *cache_ctrl;
+ u64 dev_size;
+
+ struct pcache_cache_data_head __percpu *data_heads;
+
+ spinlock_t key_head_lock;
+ struct pcache_cache_pos key_head;
+ u32 n_ksets;
+ struct pcache_cache_kset *ksets;
+
+ struct mutex key_tail_lock;
+ struct pcache_cache_pos key_tail;
+ u64 key_tail_seq;
+ u32 key_tail_index;
+
+ struct mutex dirty_tail_lock;
+ struct pcache_cache_pos dirty_tail;
+ u64 dirty_tail_seq;
+ u32 dirty_tail_index;
+
+ struct pcache_cache_tree req_key_tree;
+ struct work_struct clean_work;
+
+ struct mutex writeback_lock;
+ char wb_kset_onmedia_buf[PCACHE_KSET_ONMEDIA_SIZE_MAX];
+ struct pcache_cache_tree writeback_key_tree;
+ struct delayed_work writeback_work;
+
+ char gc_kset_onmedia_buf[PCACHE_KSET_ONMEDIA_SIZE_MAX];
+ struct delayed_work gc_work;
+ atomic_t gc_errors;
+
+ struct kmem_cache *req_cache;
+
+ struct mutex cache_info_lock;
+ struct pcache_cache_info cache_info;
+ struct pcache_cache_info *cache_info_addr;
+ u32 info_index;
+
+ u32 n_segs;
+ unsigned long *seg_map;
+ u32 last_cache_seg;
+ spinlock_t seg_map_lock;
+ struct pcache_cache_segment *segments;
+};
+
+struct workqueue_struct *cache_get_wq(struct pcache_cache *cache);
+
+struct dm_pcache;
+struct pcache_cache_options {
+ u32 cache_mode:4;
+ u32 data_crc:1;
+};
+int pcache_cache_start(struct dm_pcache *pcache, struct pcache_cache_options *opts);
+void pcache_cache_stop(struct dm_pcache *pcache);
+
+struct pcache_cache_ctrl {
+ /* Updated by gc_thread */
+ struct pcache_cache_pos_onmedia key_tail_pos[PCACHE_META_INDEX_MAX];
+
+ /* Updated by writeback_thread */
+ struct pcache_cache_pos_onmedia dirty_tail_pos[PCACHE_META_INDEX_MAX];
+};
+
+struct pcache_cache_data_head {
+ struct pcache_cache_pos head_pos;
+};
+
+static inline u16 pcache_cache_get_gc_percent(struct pcache_cache *cache)
+{
+ return FIELD_GET(PCACHE_CACHE_FLAGS_GC_PERCENT_MASK, cache->cache_info.flags);
+}
+
+int pcache_cache_set_gc_percent(struct pcache_cache *cache, u8 percent);
+
+/* cache key */
+struct pcache_cache_key *cache_key_alloc(struct pcache_cache_tree *cache_tree);
+void cache_key_init(struct pcache_cache_tree *cache_tree, struct pcache_cache_key *key);
+void cache_key_get(struct pcache_cache_key *key);
+void cache_key_put(struct pcache_cache_key *key);
+int cache_key_append(struct pcache_cache *cache, struct pcache_cache_key *key, bool force_close);
+int cache_key_insert(struct pcache_cache_tree *cache_tree, struct pcache_cache_key *key, bool fixup);
+int cache_key_decode(struct pcache_cache *cache,
+ struct pcache_cache_key_onmedia *key_onmedia,
+ struct pcache_cache_key *key);
+void cache_pos_advance(struct pcache_cache_pos *pos, u32 len);
+
+#define PCACHE_KSET_FLAGS_LAST BIT(0)
+#define PCACHE_KSET_MAGIC 0x676894a64e164f1aULL
+
+struct pcache_cache_kset {
+ struct pcache_cache *cache;
+ spinlock_t kset_lock;
+ struct delayed_work flush_work;
+ struct pcache_cache_kset_onmedia kset_onmedia;
+};
+
+extern struct pcache_cache_kset_onmedia pcache_empty_kset;
+
+struct pcache_cache_subtree_walk_ctx {
+ struct pcache_cache_tree *cache_tree;
+ struct rb_node *start_node;
+ struct pcache_request *pcache_req;
+ u32 req_done;
+ struct pcache_cache_key *key;
+
+ struct list_head *delete_key_list;
+ struct list_head *submit_req_list;
+
+ /*
+ * |--------| key_tmp
+ * |====| key
+ */
+ int (*before)(struct pcache_cache_key *key, struct pcache_cache_key *key_tmp,
+ struct pcache_cache_subtree_walk_ctx *ctx);
+
+ /*
+ * |----------| key_tmp
+ * |=====| key
+ */
+ int (*after)(struct pcache_cache_key *key, struct pcache_cache_key *key_tmp,
+ struct pcache_cache_subtree_walk_ctx *ctx);
+
+ /*
+ * |----------------| key_tmp
+ * |===========| key
+ */
+ int (*overlap_tail)(struct pcache_cache_key *key, struct pcache_cache_key *key_tmp,
+ struct pcache_cache_subtree_walk_ctx *ctx);
+
+ /*
+ * |--------| key_tmp
+ * |==========| key
+ */
+ int (*overlap_head)(struct pcache_cache_key *key, struct pcache_cache_key *key_tmp,
+ struct pcache_cache_subtree_walk_ctx *ctx);
+
+ /*
+ * |----| key_tmp
+ * |==========| key
+ */
+ int (*overlap_contain)(struct pcache_cache_key *key, struct pcache_cache_key *key_tmp,
+ struct pcache_cache_subtree_walk_ctx *ctx);
+
+ /*
+ * |-----------| key_tmp
+ * |====| key
+ */
+ int (*overlap_contained)(struct pcache_cache_key *key, struct pcache_cache_key *key_tmp,
+ struct pcache_cache_subtree_walk_ctx *ctx);
+
+ int (*walk_finally)(struct pcache_cache_subtree_walk_ctx *ctx);
+ bool (*walk_done)(struct pcache_cache_subtree_walk_ctx *ctx);
+};
+
+int cache_subtree_walk(struct pcache_cache_subtree_walk_ctx *ctx);
+struct rb_node *cache_subtree_search(struct pcache_cache_subtree *cache_subtree, struct pcache_cache_key *key,
+ struct rb_node **parentp, struct rb_node ***newp,
+ struct list_head *delete_key_list);
+int cache_kset_close(struct pcache_cache *cache, struct pcache_cache_kset *kset);
+void clean_fn(struct work_struct *work);
+void kset_flush_fn(struct work_struct *work);
+int cache_replay(struct pcache_cache *cache);
+int cache_tree_init(struct pcache_cache *cache, struct pcache_cache_tree *cache_tree, u32 n_subtrees);
+void cache_tree_exit(struct pcache_cache_tree *cache_tree);
+
+/* cache segments */
+struct pcache_cache_segment *get_cache_segment(struct pcache_cache *cache);
+int cache_seg_init(struct pcache_cache *cache, u32 seg_id, u32 cache_seg_id,
+ bool new_cache);
+void cache_seg_get(struct pcache_cache_segment *cache_seg);
+void cache_seg_put(struct pcache_cache_segment *cache_seg);
+void cache_seg_set_next_seg(struct pcache_cache_segment *cache_seg, u32 seg_id);
+
+/* cache request*/
+int cache_flush(struct pcache_cache *cache);
+void miss_read_end_work_fn(struct work_struct *work);
+int pcache_cache_handle_req(struct pcache_cache *cache, struct pcache_request *pcache_req);
+
+/* gc */
+void pcache_cache_gc_fn(struct work_struct *work);
+
+/* writeback */
+void cache_writeback_exit(struct pcache_cache *cache);
+int cache_writeback_init(struct pcache_cache *cache);
+void cache_writeback_fn(struct work_struct *work);
+
+/* inline functions */
+static inline struct pcache_cache_subtree *get_subtree(struct pcache_cache_tree *cache_tree, u64 off)
+{
+ if (cache_tree->n_subtrees == 1)
+ return &cache_tree->subtrees[0];
+
+ return &cache_tree->subtrees[off >> PCACHE_CACHE_SUBTREE_SIZE_SHIFT];
+}
+
+static inline void *cache_pos_addr(struct pcache_cache_pos *pos)
+{
+ return (pos->cache_seg->segment.data + pos->seg_off);
+}
+
+static inline void *get_key_head_addr(struct pcache_cache *cache)
+{
+ return cache_pos_addr(&cache->key_head);
+}
+
+static inline u32 get_kset_id(struct pcache_cache *cache, u64 off)
+{
+ return (off >> PCACHE_CACHE_SUBTREE_SIZE_SHIFT) % cache->n_ksets;
+}
+
+static inline struct pcache_cache_kset *get_kset(struct pcache_cache *cache, u32 kset_id)
+{
+ return (void *)cache->ksets + PCACHE_KSET_SIZE * kset_id;
+}
+
+static inline struct pcache_cache_data_head *get_data_head(struct pcache_cache *cache)
+{
+ return this_cpu_ptr(cache->data_heads);
+}
+
+static inline bool cache_key_empty(struct pcache_cache_key *key)
+{
+ return key->flags & PCACHE_CACHE_KEY_FLAGS_EMPTY;
+}
+
+static inline bool cache_key_clean(struct pcache_cache_key *key)
+{
+ return key->flags & PCACHE_CACHE_KEY_FLAGS_CLEAN;
+}
+
+static inline void cache_pos_copy(struct pcache_cache_pos *dst, struct pcache_cache_pos *src)
+{
+ memcpy(dst, src, sizeof(struct pcache_cache_pos));
+}
+
+/**
+ * cache_seg_is_ctrl_seg - Checks if a cache segment is a cache ctrl segment.
+ * @cache_seg_id: ID of the cache segment.
+ *
+ * Returns true if the cache segment ID corresponds to a cache ctrl segment.
+ *
+ * Note: We extend the segment control of the first cache segment
+ * (cache segment ID 0) to serve as the cache control (pcache_cache_ctrl)
+ * for the entire PCACHE cache. This function determines whether the given
+ * cache segment is the one storing the pcache_cache_ctrl information.
+ */
+static inline bool cache_seg_is_ctrl_seg(u32 cache_seg_id)
+{
+ return (cache_seg_id == 0);
+}
+
+/**
+ * cache_key_cutfront - Cuts a specified length from the front of a cache key.
+ * @key: Pointer to pcache_cache_key structure.
+ * @cut_len: Length to cut from the front.
+ *
+ * Advances the cache key position by cut_len and adjusts offset and length accordingly.
+ */
+static inline void cache_key_cutfront(struct pcache_cache_key *key, u32 cut_len)
+{
+ if (key->cache_pos.cache_seg)
+ cache_pos_advance(&key->cache_pos, cut_len);
+
+ key->off += cut_len;
+ key->len -= cut_len;
+}
+
+/**
+ * cache_key_cutback - Cuts a specified length from the back of a cache key.
+ * @key: Pointer to pcache_cache_key structure.
+ * @cut_len: Length to cut from the back.
+ *
+ * Reduces the length of the cache key by cut_len.
+ */
+static inline void cache_key_cutback(struct pcache_cache_key *key, u32 cut_len)
+{
+ key->len -= cut_len;
+}
+
+static inline void cache_key_delete(struct pcache_cache_key *key)
+{
+ struct pcache_cache_subtree *cache_subtree;
+
+ cache_subtree = key->cache_subtree;
+ if (!cache_subtree)
+ return;
+
+ rb_erase(&key->rb_node, &cache_subtree->root);
+ key->flags = 0;
+ cache_key_put(key);
+}
+
+static inline bool cache_data_crc_on(struct pcache_cache *cache)
+{
+ return (cache->cache_info.flags & PCACHE_CACHE_FLAGS_DATA_CRC);
+}
+
+/**
+ * cache_key_data_crc - Calculates CRC for data in a cache key.
+ * @key: Pointer to the pcache_cache_key structure.
+ *
+ * Returns the CRC-32 checksum of the data within the cache key's position.
+ */
+static inline u32 cache_key_data_crc(struct pcache_cache_key *key)
+{
+ void *data;
+
+ data = cache_pos_addr(&key->cache_pos);
+
+ return crc32(PCACHE_CRC_SEED, data, key->len);
+}
+
+static inline u32 cache_kset_crc(struct pcache_cache_kset_onmedia *kset_onmedia)
+{
+ u32 crc_size;
+
+ if (kset_onmedia->flags & PCACHE_KSET_FLAGS_LAST)
+ crc_size = sizeof(struct pcache_cache_kset_onmedia) - 4;
+ else
+ crc_size = struct_size(kset_onmedia, data, kset_onmedia->key_num) - 4;
+
+ return crc32(PCACHE_CRC_SEED, (void *)kset_onmedia + 4, crc_size);
+}
+
+static inline u32 get_kset_onmedia_size(struct pcache_cache_kset_onmedia *kset_onmedia)
+{
+ return struct_size_t(struct pcache_cache_kset_onmedia, data, kset_onmedia->key_num);
+}
+
+/**
+ * cache_seg_remain - Computes remaining space in a cache segment.
+ * @pos: Pointer to pcache_cache_pos structure.
+ *
+ * Returns the amount of remaining space in the segment data starting from
+ * the current position offset.
+ */
+static inline u32 cache_seg_remain(struct pcache_cache_pos *pos)
+{
+ struct pcache_cache_segment *cache_seg;
+ struct pcache_segment *segment;
+ u32 seg_remain;
+
+ cache_seg = pos->cache_seg;
+ segment = &cache_seg->segment;
+ seg_remain = segment->data_size - pos->seg_off;
+
+ return seg_remain;
+}
+
+/**
+ * cache_key_invalid - Checks if a cache key is invalid.
+ * @key: Pointer to pcache_cache_key structure.
+ *
+ * Returns true if the cache key is invalid due to its generation being
+ * less than the generation of its segment; otherwise returns false.
+ *
+ * When the GC (garbage collection) thread identifies a segment
+ * as reclaimable, it increments the segment's generation (gen). However,
+ * it does not immediately remove all related cache keys. When accessing
+ * such a cache key, this function can be used to determine if the cache
+ * key has already become invalid.
+ */
+static inline bool cache_key_invalid(struct pcache_cache_key *key)
+{
+ if (cache_key_empty(key))
+ return false;
+
+ return (key->seg_gen < key->cache_pos.cache_seg->gen);
+}
+
+/**
+ * cache_key_lstart - Retrieves the logical start offset of a cache key.
+ * @key: Pointer to pcache_cache_key structure.
+ *
+ * Returns the logical start offset for the cache key.
+ */
+static inline u64 cache_key_lstart(struct pcache_cache_key *key)
+{
+ return key->off;
+}
+
+/**
+ * cache_key_lend - Retrieves the logical end offset of a cache key.
+ * @key: Pointer to pcache_cache_key structure.
+ *
+ * Returns the logical end offset for the cache key.
+ */
+static inline u64 cache_key_lend(struct pcache_cache_key *key)
+{
+ return key->off + key->len;
+}
+
+static inline void cache_key_copy(struct pcache_cache_key *key_dst, struct pcache_cache_key *key_src)
+{
+ key_dst->off = key_src->off;
+ key_dst->len = key_src->len;
+ key_dst->seg_gen = key_src->seg_gen;
+ key_dst->cache_tree = key_src->cache_tree;
+ key_dst->cache_subtree = key_src->cache_subtree;
+ key_dst->flags = key_src->flags;
+
+ cache_pos_copy(&key_dst->cache_pos, &key_src->cache_pos);
+}
+
+/**
+ * cache_pos_onmedia_crc - Calculates the CRC for an on-media cache position.
+ * @pos_om: Pointer to pcache_cache_pos_onmedia structure.
+ *
+ * Calculates the CRC-32 checksum of the position, excluding the first 4 bytes.
+ * Returns the computed CRC value.
+ */
+static inline u32 cache_pos_onmedia_crc(struct pcache_cache_pos_onmedia *pos_om)
+{
+ return pcache_meta_crc(&pos_om->header, sizeof(struct pcache_cache_pos_onmedia));
+}
+
+void cache_pos_encode(struct pcache_cache *cache,
+ struct pcache_cache_pos_onmedia *pos_onmedia,
+ struct pcache_cache_pos *pos, u64 seq, u32 *index);
+int cache_pos_decode(struct pcache_cache *cache,
+ struct pcache_cache_pos_onmedia *pos_onmedia,
+ struct pcache_cache_pos *pos, u64 *seq, u32 *index);
+
+static inline void cache_encode_key_tail(struct pcache_cache *cache)
+{
+ cache_pos_encode(cache, cache->cache_ctrl->key_tail_pos,
+ &cache->key_tail, ++cache->key_tail_seq,
+ &cache->key_tail_index);
+}
+
+static inline int cache_decode_key_tail(struct pcache_cache *cache)
+{
+ return cache_pos_decode(cache, cache->cache_ctrl->key_tail_pos,
+ &cache->key_tail, &cache->key_tail_seq,
+ &cache->key_tail_index);
+}
+
+static inline void cache_encode_dirty_tail(struct pcache_cache *cache)
+{
+ cache_pos_encode(cache, cache->cache_ctrl->dirty_tail_pos,
+ &cache->dirty_tail, ++cache->dirty_tail_seq,
+ &cache->dirty_tail_index);
+}
+
+static inline int cache_decode_dirty_tail(struct pcache_cache *cache)
+{
+ return cache_pos_decode(cache, cache->cache_ctrl->dirty_tail_pos,
+ &cache->dirty_tail, &cache->dirty_tail_seq,
+ &cache->dirty_tail_index);
+}
+#endif /* _PCACHE_CACHE_H */
--
2.34.1
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