From patchwork Mon Apr 14 01:45:01 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Dongsheng Yang X-Patchwork-Id: 14049561 Received: from out-173.mta1.migadu.com (out-173.mta1.migadu.com [95.215.58.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DB8AF1A3BA1 for ; Mon, 14 Apr 2025 01:45:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744595153; cv=none; b=DFIjI5rNAbGMWEuQRIFJN2kBBpnlRvGb7hjtGQEdrQc+W4CpRmTrYP4HE9laWkHFYEELsk6mLh7oxx4RMY2OZqFt3nOJ899OeM5uGKxImGpO8dis/W8jCSQ1wxgV98xLJTDSaQ9mPbdxgF+KIBFRd56lr8Hd5Ryxyvx13st+Pug= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744595153; c=relaxed/simple; bh=VZckwGgBqeyJPiuj1COjAFk16qUJWiOt/jKHpfPHaeY=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=ZmydMGjkzc2sFRvaH6kUJVHB55OdBQtnFZvt/sporWzjT8qYlBvV31Feq0fcA5j0Va/sg9okPLY2BJRO+90++dyS1500HGEtxhfl7Sakr4Y+d3/gDyd+cNC6UevwBeCSveHWnLNQ9REZL7VThGFmhor2q3cS55o5cR/To3Ig/I4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=C/i6Wx+E; arc=none smtp.client-ip=95.215.58.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="C/i6Wx+E" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1744595149; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PERYZnF60Rueh79zQCyZ/qsBqw4mzIQTx9IQaNEQUms=; b=C/i6Wx+ErnwGPEqGJu/SrAxhuhTnZfDXOMlPYevcCKw7vkKWFW49gFdj+7ffV0NLC5ZkBq OlbFnEgiNdDwPQ8cGkfnXDQthmnXSZSvoY5e0PaAJbXEGMVsMTxFjcHZeyJ1D+SkUqIqZV XWFClSRYVDfxftkxAd950hyOMHimr1Q= From: Dongsheng Yang To: axboe@kernel.dk, hch@lst.de, dan.j.williams@intel.com, gregory.price@memverge.com, John@groves.net, Jonathan.Cameron@Huawei.com, bbhushan2@marvell.com, chaitanyak@nvidia.com, rdunlap@infradead.org Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, linux-bcache@vger.kernel.org, nvdimm@lists.linux.dev, Dongsheng Yang Subject: [RFC PATCH 07/11] pcache: introduce cache_key infrastructure for persistent metadata management Date: Mon, 14 Apr 2025 01:45:01 +0000 Message-Id: <20250414014505.20477-8-dongsheng.yang@linux.dev> In-Reply-To: <20250414014505.20477-1-dongsheng.yang@linux.dev> References: <20250414014505.20477-1-dongsheng.yang@linux.dev> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT This patch adds a comprehensive cache key management module to pcache. Cache keys represent a mapping between logical offsets and cached data in persistent memory. The new implementation provides functions for: - Allocation and initialization of cache keys with reference counting, using kmem_cache for efficient memory management. - Encoding cache keys into an on-media format (struct pcache_cache_key_onmedia) that stores offset, length, segment information (segment ID and offset), generation number, and flags, with optional data CRC for integrity. - Decoding on-media cache keys and validating their integrity, reporting errors if mismatches occur. - Appending keys to ksets and handling kset flush when a kset becomes full, including support for appending a “last kset” marker for segment chaining. - Insertion of cache keys into the cache tree (implemented as an RB-tree), including custom overlap fixup functions (fixup_overlap_tail, fixup_overlap_head, fixup_overlap_contain, fixup_overlap_contained) to handle various overlapping scenarios during key insertion. - Cache tree traversal and search functions (cache_subtree_walk, cache_subtree_search) for efficient key management and garbage collection, along with a background cleanup routine (clean_fn) to remove invalid keys. This cache_key infrastructure is a key part of the pcache metadata system, enabling persistent, crash-consistent tracking of cached data locations and facilitating recovery and garbage collection. Signed-off-by: Dongsheng Yang --- drivers/block/pcache/cache_key.c | 885 +++++++++++++++++++++++++++++++ 1 file changed, 885 insertions(+) create mode 100644 drivers/block/pcache/cache_key.c diff --git a/drivers/block/pcache/cache_key.c b/drivers/block/pcache/cache_key.c new file mode 100644 index 000000000000..d68055ae8c2f --- /dev/null +++ b/drivers/block/pcache/cache_key.c @@ -0,0 +1,885 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +#include "cache.h" +#include "backing_dev.h" + +struct pcache_cache_kset_onmedia pcache_empty_kset = { 0 }; + +void cache_key_init(struct pcache_cache_tree *cache_tree, struct pcache_cache_key *key) +{ + kref_init(&key->ref); + key->cache_tree = cache_tree; + INIT_LIST_HEAD(&key->list_node); + RB_CLEAR_NODE(&key->rb_node); +} + +struct pcache_cache_key *cache_key_alloc(struct pcache_cache_tree *cache_tree) +{ + struct pcache_cache_key *key; + + key = kmem_cache_zalloc(cache_tree->key_cache, GFP_NOWAIT); + if (!key) + return NULL; + + cache_key_init(cache_tree, key); + + return key; +} + +/** + * cache_key_get - Increment the reference count of a cache key. + * @key: Pointer to the pcache_cache_key structure. + * + * This function increments the reference count of the specified cache key, + * ensuring that it is not freed while still in use. + */ +void cache_key_get(struct pcache_cache_key *key) +{ + kref_get(&key->ref); +} + +/** + * cache_key_destroy - Free a cache key structure when its reference count drops to zero. + * @ref: Pointer to the kref structure. + * + * This function is called when the reference count of the cache key reaches zero. + * It frees the allocated cache key back to the slab cache. + */ +static void cache_key_destroy(struct kref *ref) +{ + struct pcache_cache_key *key = container_of(ref, struct pcache_cache_key, ref); + struct pcache_cache_tree *cache_tree = key->cache_tree; + + kmem_cache_free(cache_tree->key_cache, key); +} + +void cache_key_put(struct pcache_cache_key *key) +{ + kref_put(&key->ref, cache_key_destroy); +} + +void cache_pos_advance(struct pcache_cache_pos *pos, u32 len) +{ + /* Ensure enough space remains in the current segment */ + BUG_ON(cache_seg_remain(pos) < len); + + pos->seg_off += len; +} + +static void cache_key_encode(struct pcache_cache *cache, + struct pcache_cache_key_onmedia *key_onmedia, + struct pcache_cache_key *key) +{ + key_onmedia->off = key->off; + key_onmedia->len = key->len; + + key_onmedia->cache_seg_id = key->cache_pos.cache_seg->cache_seg_id; + key_onmedia->cache_seg_off = key->cache_pos.seg_off; + + key_onmedia->seg_gen = key->seg_gen; + key_onmedia->flags = key->flags; + + if (cache_data_crc_on(cache)) + key_onmedia->data_crc = cache_key_data_crc(key); +} + +int cache_key_decode(struct pcache_cache *cache, + struct pcache_cache_key_onmedia *key_onmedia, + struct pcache_cache_key *key) +{ + key->off = key_onmedia->off; + key->len = key_onmedia->len; + + key->cache_pos.cache_seg = &cache->segments[key_onmedia->cache_seg_id]; + key->cache_pos.seg_off = key_onmedia->cache_seg_off; + + key->seg_gen = key_onmedia->seg_gen; + key->flags = key_onmedia->flags; + + if (cache_data_crc_on(cache) && + key_onmedia->data_crc != cache_key_data_crc(key)) { + backing_dev_err(cache->backing_dev, "key: %llu:%u seg %u:%u data_crc error: %x, expected: %x\n", + key->off, key->len, key->cache_pos.cache_seg->cache_seg_id, + key->cache_pos.seg_off, cache_key_data_crc(key), key_onmedia->data_crc); + return -EIO; + } + + return 0; +} + +static void append_last_kset(struct pcache_cache *cache, u32 next_seg) +{ + struct pcache_cache_kset_onmedia *kset_onmedia; + + kset_onmedia = get_key_head_addr(cache); + kset_onmedia->flags |= PCACHE_KSET_FLAGS_LAST; + kset_onmedia->next_cache_seg_id = next_seg; + kset_onmedia->magic = PCACHE_KSET_MAGIC; + kset_onmedia->crc = cache_kset_crc(kset_onmedia); + cache_pos_advance(&cache->key_head, sizeof(struct pcache_cache_kset_onmedia)); +} + +int cache_kset_close(struct pcache_cache *cache, struct pcache_cache_kset *kset) +{ + struct pcache_cache_kset_onmedia *kset_onmedia; + u32 kset_onmedia_size; + int ret; + + kset_onmedia = &kset->kset_onmedia; + + if (!kset_onmedia->key_num) + return 0; + + kset_onmedia_size = struct_size(kset_onmedia, data, kset_onmedia->key_num); + + spin_lock(&cache->key_head_lock); +again: + /* Reserve space for the last kset */ + if (cache_seg_remain(&cache->key_head) < kset_onmedia_size + sizeof(struct pcache_cache_kset_onmedia)) { + struct pcache_cache_segment *next_seg; + + next_seg = get_cache_segment(cache); + if (!next_seg) { + ret = -EBUSY; + goto out; + } + + /* clear outdated kset in next seg */ + memcpy_flushcache(next_seg->segment.data, &pcache_empty_kset, + sizeof(struct pcache_cache_kset_onmedia)); + append_last_kset(cache, next_seg->cache_seg_id); + cache->key_head.cache_seg = next_seg; + cache->key_head.seg_off = 0; + goto again; + } + + kset_onmedia->magic = PCACHE_KSET_MAGIC; + kset_onmedia->crc = cache_kset_crc(kset_onmedia); + + /* clear outdated kset after current kset */ + memcpy_flushcache(get_key_head_addr(cache) + kset_onmedia_size, &pcache_empty_kset, + sizeof(struct pcache_cache_kset_onmedia)); + + /* write current kset into segment */ + memcpy_flushcache(get_key_head_addr(cache), kset_onmedia, kset_onmedia_size); + memset(kset_onmedia, 0, sizeof(struct pcache_cache_kset_onmedia)); + cache_pos_advance(&cache->key_head, kset_onmedia_size); + + ret = 0; +out: + spin_unlock(&cache->key_head_lock); + + return ret; +} + +/** + * cache_key_append - Append a cache key to the related kset. + * @cache: Pointer to the pcache_cache structure. + * @key: Pointer to the cache key structure to append. + * + * This function appends a cache key to the appropriate kset. If the kset + * is full, it closes the kset. If not, it queues a flush work to write + * the kset to media. + * + * Returns 0 on success, or a negative error code on failure. + */ +int cache_key_append(struct pcache_cache *cache, struct pcache_cache_key *key) +{ + struct pcache_cache_kset *kset; + struct pcache_cache_kset_onmedia *kset_onmedia; + struct pcache_cache_key_onmedia *key_onmedia; + u32 kset_id = get_kset_id(cache, key->off); + int ret = 0; + + kset = get_kset(cache, kset_id); + kset_onmedia = &kset->kset_onmedia; + + spin_lock(&kset->kset_lock); + key_onmedia = &kset_onmedia->data[kset_onmedia->key_num]; + cache_key_encode(cache, key_onmedia, key); + + /* Check if the current kset has reached the maximum number of keys */ + if (++kset_onmedia->key_num == PCACHE_KSET_KEYS_MAX) { + /* If full, close the kset */ + ret = cache_kset_close(cache, kset); + if (ret) { + kset_onmedia->key_num--; + goto out; + } + } else { + /* If not full, queue a delayed work to flush the kset */ + queue_delayed_work(cache->backing_dev->task_wq, &kset->flush_work, 1 * HZ); + } +out: + spin_unlock(&kset->kset_lock); + + return ret; +} + +/** + * cache_subtree_walk - Traverse the cache tree. + * @cache: Pointer to the pcache_cache structure. + * @ctx: Pointer to the context structure for traversal. + * + * This function traverses the cache tree starting from the specified node. + * It calls the appropriate callback functions based on the relationships + * between the keys in the cache tree. + * + * Returns 0 on success, or a negative error code on failure. + */ +int cache_subtree_walk(struct pcache_cache_subtree_walk_ctx *ctx) +{ + struct pcache_cache_key *key_tmp, *key; + struct rb_node *node_tmp; + int ret; + + key = ctx->key; + node_tmp = ctx->start_node; + + while (node_tmp) { + if (ctx->walk_done && ctx->walk_done(ctx)) + break; + + key_tmp = CACHE_KEY(node_tmp); + /* + * If key_tmp ends before the start of key, continue to the next node. + * |----------| + * |=====| + */ + if (cache_key_lend(key_tmp) <= cache_key_lstart(key)) { + if (ctx->after) { + ret = ctx->after(key, key_tmp, ctx); + if (ret) + goto out; + } + goto next; + } + + /* + * If key_tmp starts after the end of key, stop traversing. + * |--------| + * |====| + */ + if (cache_key_lstart(key_tmp) >= cache_key_lend(key)) { + if (ctx->before) { + ret = ctx->before(key, key_tmp, ctx); + if (ret) + goto out; + } + break; + } + + /* Handle overlapping keys */ + if (cache_key_lstart(key_tmp) >= cache_key_lstart(key)) { + /* + * If key_tmp encompasses key. + * |----------------| key_tmp + * |===========| key + */ + if (cache_key_lend(key_tmp) >= cache_key_lend(key)) { + if (ctx->overlap_tail) { + ret = ctx->overlap_tail(key, key_tmp, ctx); + if (ret) + goto out; + } + break; + } + + /* + * If key_tmp is contained within key. + * |----| key_tmp + * |==========| key + */ + if (ctx->overlap_contain) { + ret = ctx->overlap_contain(key, key_tmp, ctx); + if (ret) + goto out; + } + + goto next; + } + + /* + * If key_tmp starts before key ends but ends after key. + * |-----------| key_tmp + * |====| key + */ + if (cache_key_lend(key_tmp) > cache_key_lend(key)) { + if (ctx->overlap_contained) { + ret = ctx->overlap_contained(key, key_tmp, ctx); + if (ret) + goto out; + } + break; + } + + /* + * If key_tmp starts before key and ends within key. + * |--------| key_tmp + * |==========| key + */ + if (ctx->overlap_head) { + ret = ctx->overlap_head(key, key_tmp, ctx); + if (ret) + goto out; + } +next: + node_tmp = rb_next(node_tmp); + } + + if (ctx->walk_finally) { + ret = ctx->walk_finally(ctx); + if (ret) + goto out; + } + + return 0; +out: + return ret; +} + +/** + * cache_subtree_search - Search for a key in the cache tree. + * @cache_subtree: Pointer to the cache tree structure. + * @key: Pointer to the cache key to search for. + * @parentp: Pointer to store the parent node of the found node. + * @newp: Pointer to store the location where the new node should be inserted. + * @delete_key_list: List to collect invalid keys for deletion. + * + * This function searches the cache tree for a specific key and returns + * the node that is the predecessor of the key, or first node if the key is + * less than all keys in the tree. If any invalid keys are found during + * the search, they are added to the delete_key_list for later cleanup. + * + * Returns a pointer to the previous node. + */ +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) +{ + struct rb_node **new, *parent = NULL; + struct pcache_cache_key *key_tmp; + struct rb_node *prev_node = NULL; + + new = &(cache_subtree->root.rb_node); + while (*new) { + key_tmp = container_of(*new, struct pcache_cache_key, rb_node); + if (cache_key_invalid(key_tmp)) + list_add(&key_tmp->list_node, delete_key_list); + + parent = *new; + if (key_tmp->off >= key->off) { + new = &((*new)->rb_left); + } else { + prev_node = *new; + new = &((*new)->rb_right); + } + } + + if (!prev_node) + prev_node = rb_first(&cache_subtree->root); + + if (parentp) + *parentp = parent; + + if (newp) + *newp = new; + + return prev_node; +} + +/** + * fixup_overlap_tail - Adjust the key when it overlaps at the tail. + * @key: Pointer to the new cache key being inserted. + * @key_tmp: Pointer to the existing key that overlaps. + * @ctx: Pointer to the context for walking the cache tree. + * + * This function modifies the existing key (key_tmp) when there is an + * overlap at the tail with the new key. If the modified key becomes + * empty, it is deleted. Returns 0 on success, or -EAGAIN if the key + * needs to be reinserted. + */ +static int fixup_overlap_tail(struct pcache_cache_key *key, + struct pcache_cache_key *key_tmp, + struct pcache_cache_subtree_walk_ctx *ctx) +{ + int ret; + + /* + * |----------------| key_tmp + * |===========| key + */ + cache_key_cutfront(key_tmp, cache_key_lend(key) - cache_key_lstart(key_tmp)); + if (key_tmp->len == 0) { + cache_key_delete(key_tmp); + ret = -EAGAIN; + + /* + * Deleting key_tmp may change the structure of the + * entire cache tree, so we need to re-search the tree + * to determine the new insertion point for the key. + */ + goto out; + } + + return 0; +out: + return ret; +} + +/** + * fixup_overlap_contain - Handle case where new key completely contains an existing key. + * @key: Pointer to the new cache key being inserted. + * @key_tmp: Pointer to the existing key that is being contained. + * @ctx: Pointer to the context for walking the cache tree. + * + * This function deletes the existing key (key_tmp) when the new key + * completely contains it. It returns -EAGAIN to indicate that the + * tree structure may have changed, necessitating a re-insertion of + * the new key. + */ +static int fixup_overlap_contain(struct pcache_cache_key *key, + struct pcache_cache_key *key_tmp, + struct pcache_cache_subtree_walk_ctx *ctx) +{ + /* + * |----| key_tmp + * |==========| key + */ + cache_key_delete(key_tmp); + + return -EAGAIN; +} + +/** + * fixup_overlap_contained - Handle overlap when a new key is contained in an existing key. + * @key: The new cache key being inserted. + * @key_tmp: The existing cache key that overlaps with the new key. + * @ctx: Context for the cache tree walk. + * + * This function adjusts the existing key if the new key is contained + * within it. If the existing key is empty, it indicates a placeholder key + * that was inserted during a miss read. This placeholder will later be + * updated with real data from the backing_dev, making it no longer an empty key. + * + * If we delete key or insert a key, the structure of the entire cache tree may change, + * requiring a full research of the tree to find a new insertion point. + */ +static int fixup_overlap_contained(struct pcache_cache_key *key, + struct pcache_cache_key *key_tmp, struct pcache_cache_subtree_walk_ctx *ctx) +{ + struct pcache_cache_tree *cache_tree = ctx->cache_tree; + int ret; + + /* + * |-----------| key_tmp + * |====| key + */ + if (cache_key_empty(key_tmp)) { + /* If key_tmp is empty, don't split it; + * it's a placeholder key for miss reads that will be updated later. + */ + cache_key_cutback(key_tmp, cache_key_lend(key_tmp) - cache_key_lstart(key)); + if (key_tmp->len == 0) { + cache_key_delete(key_tmp); + ret = -EAGAIN; + goto out; + } + } else { + struct pcache_cache_key *key_fixup; + bool need_research = false; + + /* Allocate a new cache key for splitting key_tmp */ + key_fixup = cache_key_alloc(cache_tree); + if (!key_fixup) { + ret = -ENOMEM; + goto out; + } + + cache_key_copy(key_fixup, key_tmp); + + /* Split key_tmp based on the new key's range */ + cache_key_cutback(key_tmp, cache_key_lend(key_tmp) - cache_key_lstart(key)); + if (key_tmp->len == 0) { + cache_key_delete(key_tmp); + need_research = true; + } + + /* Create a new portion for key_fixup */ + cache_key_cutfront(key_fixup, cache_key_lend(key) - cache_key_lstart(key_tmp)); + if (key_fixup->len == 0) { + cache_key_put(key_fixup); + } else { + /* Insert the new key into the cache */ + ret = cache_key_insert(cache_tree, key_fixup, false); + if (ret) + goto out; + need_research = true; + } + + if (need_research) { + ret = -EAGAIN; + goto out; + } + } + + return 0; +out: + return ret; +} + +/** + * fixup_overlap_head - Handle overlap when a new key overlaps with the head of an existing key. + * @key: The new cache key being inserted. + * @key_tmp: The existing cache key that overlaps with the new key. + * @ctx: Context for the cache tree walk. + * + * This function adjusts the existing key if the new key overlaps + * with the beginning of it. If the resulting key length is zero + * after the adjustment, the key is deleted. This indicates that + * the key no longer holds valid data and requires the tree to be + * re-researched for a new insertion point. + */ +static int fixup_overlap_head(struct pcache_cache_key *key, + struct pcache_cache_key *key_tmp, struct pcache_cache_subtree_walk_ctx *ctx) +{ + /* + * |--------| key_tmp + * |==========| key + */ + /* Adjust key_tmp by cutting back based on the new key's start */ + cache_key_cutback(key_tmp, cache_key_lend(key_tmp) - cache_key_lstart(key)); + if (key_tmp->len == 0) { + /* If the adjusted key_tmp length is zero, delete it */ + cache_key_delete(key_tmp); + return -EAGAIN; + } + + return 0; +} + +/** + * cache_insert_fixup - Fix up overlaps when inserting a new key. + * @cache_tree: Pointer to the cache_tree structure. + * @key: The new cache key to insert. + * @prev_node: The last visited node during the search. + * + * This function initializes a walking context and calls the + * cache_subtree_walk function to handle potential overlaps between + * the new key and existing keys in the cache tree. Various + * fixup functions are provided to manage different overlap scenarios. + */ +static int cache_insert_fixup(struct pcache_cache_tree *cache_tree, + struct pcache_cache_key *key, struct rb_node *prev_node) +{ + struct pcache_cache_subtree_walk_ctx walk_ctx = { 0 }; + + /* Set up the context with the cache, start node, and new key */ + walk_ctx.cache_tree = cache_tree; + walk_ctx.start_node = prev_node; + walk_ctx.key = key; + + /* Assign overlap handling functions for different scenarios */ + walk_ctx.overlap_tail = fixup_overlap_tail; + walk_ctx.overlap_head = fixup_overlap_head; + walk_ctx.overlap_contain = fixup_overlap_contain; + walk_ctx.overlap_contained = fixup_overlap_contained; + + /* Begin walking the cache tree to fix overlaps */ + return cache_subtree_walk(&walk_ctx); +} + +/** + * cache_key_insert - Insert a new cache key into the cache tree. + * @cache_tree: Pointer to the cache_tree structure. + * @key: The cache key to insert. + * @fixup: Indicates if this is a new key being inserted. + * + * This function searches for the appropriate location to insert + * a new cache key into the cache tree. It handles key overlaps + * and ensures any invalid keys are removed before insertion. + * + * Returns 0 on success or a negative error code on failure. + */ +int cache_key_insert(struct pcache_cache_tree *cache_tree, struct pcache_cache_key *key, bool fixup) +{ + struct rb_node **new, *parent = NULL; + struct pcache_cache_subtree *cache_subtree; + struct pcache_cache_key *key_tmp = NULL, *key_next; + struct rb_node *prev_node = NULL; + LIST_HEAD(delete_key_list); + int ret; + + cache_subtree = get_subtree(cache_tree, key->off); + key->cache_subtree = cache_subtree; +search: + prev_node = cache_subtree_search(cache_subtree, key, &parent, &new, &delete_key_list); + if (!list_empty(&delete_key_list)) { + /* Remove invalid keys from the delete list */ + list_for_each_entry_safe(key_tmp, key_next, &delete_key_list, list_node) { + list_del_init(&key_tmp->list_node); + cache_key_delete(key_tmp); + } + goto search; + } + + if (fixup) { + ret = cache_insert_fixup(cache_tree, key, prev_node); + if (ret == -EAGAIN) + goto search; + if (ret) + goto out; + } + + /* Link and insert the new key into the red-black tree */ + rb_link_node(&key->rb_node, parent, new); + rb_insert_color(&key->rb_node, &cache_subtree->root); + + return 0; +out: + return ret; +} + +/** + * clean_fn - Cleanup function to remove invalid keys from the cache tree. + * @work: Pointer to the work_struct associated with the cleanup. + * + * This function cleans up invalid keys from the cache tree in the background + * after a cache segment has been invalidated during cache garbage collection. + * It processes a maximum of PCACHE_CLEAN_KEYS_MAX keys per iteration and holds + * the tree lock to ensure thread safety. + */ +void clean_fn(struct work_struct *work) +{ + struct pcache_cache *cache = container_of(work, struct pcache_cache, clean_work); + struct pcache_cache_subtree *cache_subtree; + struct rb_node *node; + struct pcache_cache_key *key; + int i, count; + + for (i = 0; i < cache->req_key_tree.n_subtrees; i++) { + cache_subtree = &cache->req_key_tree.subtrees[i]; + +again: + if (cache->state == PCACHE_CACHE_STATE_STOPPING) + return; + + /* Delete up to PCACHE_CLEAN_KEYS_MAX keys in one iteration */ + count = 0; + spin_lock(&cache_subtree->tree_lock); + node = rb_first(&cache_subtree->root); + while (node) { + key = CACHE_KEY(node); + node = rb_next(node); + if (cache_key_invalid(key)) { + count++; + cache_key_delete(key); + } + + if (count >= PCACHE_CLEAN_KEYS_MAX) { + /* Unlock and pause before continuing cleanup */ + spin_unlock(&cache_subtree->tree_lock); + usleep_range(1000, 2000); + goto again; + } + } + spin_unlock(&cache_subtree->tree_lock); + } +} + +/* + * kset_flush_fn - Flush work for a cache kset. + * + * This function is called when a kset flush work is queued from + * cache_key_append(). If the kset is full, it will be closed + * immediately. If not, the flush work will be queued for later closure. + * + * If cache_kset_close detects that a new segment is required to store + * the kset and there are no available segments, it will return an error. + * In this scenario, a retry will be attempted. + */ +void kset_flush_fn(struct work_struct *work) +{ + struct pcache_cache_kset *kset = container_of(work, struct pcache_cache_kset, flush_work.work); + struct pcache_cache *cache = kset->cache; + int ret; + + spin_lock(&kset->kset_lock); + ret = cache_kset_close(cache, kset); + spin_unlock(&kset->kset_lock); + + if (ret) { + /* Failed to flush kset, schedule a retry. */ + queue_delayed_work(cache->backing_dev->task_wq, &kset->flush_work, 0); + } +} + +static int kset_replay(struct pcache_cache *cache, struct pcache_cache_kset_onmedia *kset_onmedia) +{ + struct pcache_cache_key_onmedia *key_onmedia; + struct pcache_cache_key *key; + int ret; + int i; + + for (i = 0; i < kset_onmedia->key_num; i++) { + key_onmedia = &kset_onmedia->data[i]; + + key = cache_key_alloc(&cache->req_key_tree); + if (!key) { + ret = -ENOMEM; + goto err; + } + + ret = cache_key_decode(cache, key_onmedia, key); + if (ret) { + cache_key_put(key); + goto err; + } + + /* Mark the segment as used in the segment map. */ + set_bit(key->cache_pos.cache_seg->cache_seg_id, cache->seg_map); + + /* Check if the segment generation is valid for insertion. */ + if (key->seg_gen < key->cache_pos.cache_seg->gen) { + cache_key_put(key); + } else { + ret = cache_key_insert(&cache->req_key_tree, key, true); + if (ret) { + cache_key_put(key); + goto err; + } + } + + cache_seg_get(key->cache_pos.cache_seg); + } + + return 0; +err: + return ret; +} + +int cache_replay(struct pcache_cache *cache) +{ + struct pcache_cache_pos pos_tail; + struct pcache_cache_pos *pos; + struct pcache_cache_kset_onmedia *kset_onmedia; + u32 count = 0; + int ret = 0; + void *addr; + + cache_pos_copy(&pos_tail, &cache->key_tail); + pos = &pos_tail; + + /* Mark the segment as used in the segment map. */ + set_bit(pos->cache_seg->cache_seg_id, cache->seg_map); + + while (true) { + addr = cache_pos_addr(pos); + + kset_onmedia = (struct pcache_cache_kset_onmedia *)addr; + if (kset_onmedia->magic != PCACHE_KSET_MAGIC || + kset_onmedia->crc != cache_kset_crc(kset_onmedia)) { + break; + } + + if (kset_onmedia->crc != cache_kset_crc(kset_onmedia)) + break; + + /* Process the last kset and prepare for the next segment. */ + if (kset_onmedia->flags & PCACHE_KSET_FLAGS_LAST) { + struct pcache_cache_segment *next_seg; + + backing_dev_debug(cache->backing_dev, "last kset replay, next: %u\n", kset_onmedia->next_cache_seg_id); + + next_seg = &cache->segments[kset_onmedia->next_cache_seg_id]; + + pos->cache_seg = next_seg; + pos->seg_off = 0; + + set_bit(pos->cache_seg->cache_seg_id, cache->seg_map); + continue; + } + + /* Replay the kset and check for errors. */ + ret = kset_replay(cache, kset_onmedia); + if (ret) + goto out; + + /* Advance the position after processing the kset. */ + cache_pos_advance(pos, get_kset_onmedia_size(kset_onmedia)); + if (++count > 512) { + cond_resched(); + count = 0; + } + } + + /* Update the key_head position after replaying. */ + spin_lock(&cache->key_head_lock); + cache_pos_copy(&cache->key_head, pos); + spin_unlock(&cache->key_head_lock); + +out: + return ret; +} + +int cache_tree_init(struct pcache_cache *cache, struct pcache_cache_tree *cache_tree, u32 n_subtrees) +{ + int ret; + u32 i; + + cache_tree->cache = cache; + cache_tree->n_subtrees = n_subtrees; + + cache_tree->key_cache = KMEM_CACHE(pcache_cache_key, 0); + if (!cache_tree->key_cache) { + ret = -ENOMEM; + goto err; + } + /* + * Allocate and initialize the subtrees array. + * Each element is a cache tree structure that contains + * an RB tree root and a spinlock for protecting its contents. + */ + cache_tree->subtrees = kvcalloc(cache_tree->n_subtrees, sizeof(struct pcache_cache_subtree), GFP_KERNEL); + if (!cache_tree->n_subtrees) { + ret = -ENOMEM; + goto destroy_key_cache; + } + + for (i = 0; i < cache_tree->n_subtrees; i++) { + struct pcache_cache_subtree *cache_subtree = &cache_tree->subtrees[i]; + + cache_subtree->root = RB_ROOT; + spin_lock_init(&cache_subtree->tree_lock); + } + + return 0; + +destroy_key_cache: + kmem_cache_destroy(cache_tree->key_cache); +err: + return ret; +} + +void cache_tree_exit(struct pcache_cache_tree *cache_tree) +{ + struct pcache_cache_subtree *cache_subtree; + struct rb_node *node; + struct pcache_cache_key *key; + u32 i; + + for (i = 0; i < cache_tree->n_subtrees; i++) { + cache_subtree = &cache_tree->subtrees[i]; + + spin_lock(&cache_subtree->tree_lock); + node = rb_first(&cache_subtree->root); + while (node) { + key = CACHE_KEY(node); + node = rb_next(node); + + cache_key_delete(key); + } + spin_unlock(&cache_subtree->tree_lock); + } + kvfree(cache_tree->subtrees); + kmem_cache_destroy(cache_tree->key_cache); +}