[PATCH v12 08/13] exfat: add exfat cache

Namjae Jeon
2020-01-20T12:45:15Z

This adds the implementation of exfat cache.

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Sungjong Seo <sj1557.seo@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
---
fs/exfat/cache.c | 325 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 325 insertions(+)
create mode 100644 fs/exfat/cache.c

diff --git a/fs/exfat/cache.c b/fs/exfat/cache.c
new file mode 100644
index 000000000000..03d0824fc368
--- /dev/null
+++ b/fs/exfat/cache.c
@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * linux/fs/fat/cache.c
+ *
+ * Written 1992,1993 by Werner Almesberger
+ *
+ * Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
+ * of inode number.
+ * May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
+ * Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
+ */
+
+#include <linux/slab.h>
+#include <asm/unaligned.h>
+#include <linux/buffer_head.h>
+
+#include "exfat_raw.h"
+#include "exfat_fs.h"
+
+#define EXFAT_CACHE_VALID 0
+#define EXFAT_MAX_CACHE 16
+
+struct exfat_cache {
+ struct list_head cache_list;
+ unsigned int nr_contig; /* number of contiguous clusters */
+ unsigned int fcluster; /* cluster number in the file. */
+ unsigned int dcluster; /* cluster number on disk. */
+};
+
+struct exfat_cache_id {
+ unsigned int id;
+ unsigned int nr_contig;
+ unsigned int fcluster;
+ unsigned int dcluster;
+};
+
+static struct kmem_cache *exfat_cachep;
+
+static void exfat_cache_init_once(void *c)
+{
+ struct exfat_cache *cache = (struct exfat_cache *)c;
+
+ INIT_LIST_HEAD(&cache->cache_list);
+}
+
+int exfat_cache_init(void)
+{
+ exfat_cachep = kmem_cache_create("exfat_cache",
+ sizeof(struct exfat_cache),
+ 0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
+ exfat_cache_init_once);
+ if (!exfat_cachep)
+ return -ENOMEM;
+ return 0;
+}
+
+void exfat_cache_shutdown(void)
+{
+ if (!exfat_cachep)
+ return;
+ kmem_cache_destroy(exfat_cachep);
+}
+
+void exfat_cache_init_inode(struct inode *inode)
+{
+ struct exfat_inode_info *ei = EXFAT_I(inode);
+
+ spin_lock_init(&ei->cache_lru_lock);
+ ei->nr_caches = 0;
+ ei->cache_valid_id = EXFAT_CACHE_VALID + 1;
+ INIT_LIST_HEAD(&ei->cache_lru);
+}
+
+static inline struct exfat_cache *exfat_cache_alloc(void)
+{
+ return kmem_cache_alloc(exfat_cachep, GFP_NOFS);
+}
+
+static inline void exfat_cache_free(struct exfat_cache *cache)
+{
+ WARN_ON(!list_empty(&cache->cache_list));
+ kmem_cache_free(exfat_cachep, cache);
+}
+
+static inline void exfat_cache_update_lru(struct inode *inode,
+ struct exfat_cache *cache)
+{
+ struct exfat_inode_info *ei = EXFAT_I(inode);
+
+ if (ei->cache_lru.next != &cache->cache_list)
+ list_move(&cache->cache_list, &ei->cache_lru);
+}
+
+static unsigned int exfat_cache_lookup(struct inode *inode,
+ unsigned int fclus, struct exfat_cache_id *cid,
+ unsigned int *cached_fclus, unsigned int *cached_dclus)
+{
+ struct exfat_inode_info *ei = EXFAT_I(inode);
+ static struct exfat_cache nohit = { .fcluster = 0, };
+ struct exfat_cache *hit = &nohit, *p;
+ unsigned int offset = EXFAT_EOF_CLUSTER;
+
+ spin_lock(&ei->cache_lru_lock);
+ list_for_each_entry(p, &ei->cache_lru, cache_list) {
+ /* Find the cache of "fclus" or nearest cache. */
+ if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
+ hit = p;
+ if (hit->fcluster + hit->nr_contig < fclus) {
+ offset = hit->nr_contig;
+ } else {
+ offset = fclus - hit->fcluster;
+ break;
+ }
+ }
+ }
+ if (hit != &nohit) {
+ exfat_cache_update_lru(inode, hit);
+
+ cid->id = ei->cache_valid_id;
+ cid->nr_contig = hit->nr_contig;
+ cid->fcluster = hit->fcluster;
+ cid->dcluster = hit->dcluster;
+ *cached_fclus = cid->fcluster + offset;
+ *cached_dclus = cid->dcluster + offset;
+ }
+ spin_unlock(&ei->cache_lru_lock);
+
+ return offset;
+}
+
+static struct exfat_cache *exfat_cache_merge(struct inode *inode,
+ struct exfat_cache_id *new)
+{
+ struct exfat_inode_info *ei = EXFAT_I(inode);
+ struct exfat_cache *p;
+
+ list_for_each_entry(p, &ei->cache_lru, cache_list) {
+ /* Find the same part as "new" in cluster-chain. */
+ if (p->fcluster == new->fcluster) {
+ if (new->nr_contig > p->nr_contig)
+ p->nr_contig = new->nr_contig;
+ return p;
+ }
+ }
+ return NULL;
+}
+
+static void exfat_cache_add(struct inode *inode,
+ struct exfat_cache_id *new)
+{
+ struct exfat_inode_info *ei = EXFAT_I(inode);
+ struct exfat_cache *cache, *tmp;
+
+ if (new->fcluster == EXFAT_EOF_CLUSTER) /* dummy cache */
+ return;
+
+ spin_lock(&ei->cache_lru_lock);
+ if (new->id != EXFAT_CACHE_VALID &&
+ new->id != ei->cache_valid_id)
+ goto unlock; /* this cache was invalidated */
+
+ cache = exfat_cache_merge(inode, new);
+ if (cache == NULL) {
+ if (ei->nr_caches < EXFAT_MAX_CACHE) {
+ ei->nr_caches++;
+ spin_unlock(&ei->cache_lru_lock);
+
+ tmp = exfat_cache_alloc();
+ if (!tmp) {
+ spin_lock(&ei->cache_lru_lock);
+ ei->nr_caches--;
+ spin_unlock(&ei->cache_lru_lock);
+ return;
+ }
+
+ spin_lock(&ei->cache_lru_lock);
+ cache = exfat_cache_merge(inode, new);
+ if (cache != NULL) {
+ ei->nr_caches--;
+ exfat_cache_free(tmp);
+ goto out_update_lru;
+ }
+ cache = tmp;
+ } else {
+ struct list_head *p = ei->cache_lru.prev;
+
+ cache = list_entry(p,
+ struct exfat_cache, cache_list);
+ }
+ cache->fcluster = new->fcluster;
+ cache->dcluster = new->dcluster;
+ cache->nr_contig = new->nr_contig;
+ }
+out_update_lru:
+ exfat_cache_update_lru(inode, cache);
+unlock:
+ spin_unlock(&ei->cache_lru_lock);
+}
+
+/*
+ * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
+ * fixes itself after a while.
+ */
+static void __exfat_cache_inval_inode(struct inode *inode)
+{
+ struct exfat_inode_info *ei = EXFAT_I(inode);
+ struct exfat_cache *cache;
+
+ while (!list_empty(&ei->cache_lru)) {
+ cache = list_entry(ei->cache_lru.next,
+ struct exfat_cache, cache_list);
+ list_del_init(&cache->cache_list);
+ ei->nr_caches--;
+ exfat_cache_free(cache);
+ }
+ /* Update. The copy of caches before this id is discarded. */
+ ei->cache_valid_id++;
+ if (ei->cache_valid_id == EXFAT_CACHE_VALID)
+ ei->cache_valid_id++;
+}
+
+void exfat_cache_inval_inode(struct inode *inode)
+{
+ struct exfat_inode_info *ei = EXFAT_I(inode);
+
+ spin_lock(&ei->cache_lru_lock);
+ __exfat_cache_inval_inode(inode);
+ spin_unlock(&ei->cache_lru_lock);
+}
+
+static inline int cache_contiguous(struct exfat_cache_id *cid,
+ unsigned int dclus)
+{
+ cid->nr_contig++;
+ return cid->dcluster + cid->nr_contig == dclus;
+}
+
+static inline void cache_init(struct exfat_cache_id *cid,
+ unsigned int fclus, unsigned int dclus)
+{
+ cid->id = EXFAT_CACHE_VALID;
+ cid->fcluster = fclus;
+ cid->dcluster = dclus;
+ cid->nr_contig = 0;
+}
+
+int exfat_get_cluster(struct inode *inode, unsigned int cluster,
+ unsigned int *fclus, unsigned int *dclus,
+ unsigned int *last_dclus, int allow_eof)
+{
+ struct super_block *sb = inode->i_sb;
+ struct exfat_sb_info *sbi = EXFAT_SB(sb);
+ unsigned int limit = sbi->num_clusters;
+ struct exfat_inode_info *ei = EXFAT_I(inode);
+ struct exfat_cache_id cid;
+ unsigned int content;
+
+ if (ei->start_clu == EXFAT_FREE_CLUSTER) {
+ exfat_fs_error(sb,
+ "invalid access to exfat cache (entry 0x%08x)",
+ ei->start_clu);
+ return -EIO;
+ }
+
+ *fclus = 0;
+ *dclus = ei->start_clu;
+ *last_dclus = *dclus;
+
+ /*
+ * Don`t use exfat_cache if zero offset or non-cluster allocation
+ */
+ if (cluster == 0 || *dclus == EXFAT_EOF_CLUSTER)
+ return 0;
+
+ cache_init(&cid, EXFAT_EOF_CLUSTER, EXFAT_EOF_CLUSTER);
+
+ if (exfat_cache_lookup(inode, cluster, &cid, fclus, dclus) ==
+ EXFAT_EOF_CLUSTER) {
+ /*
+ * dummy, always not contiguous
+ * This is reinitialized by cache_init(), later.
+ */
+ WARN_ON(cid.id != EXFAT_CACHE_VALID ||
+ cid.fcluster != EXFAT_EOF_CLUSTER ||
+ cid.dcluster != EXFAT_EOF_CLUSTER ||
+ cid.nr_contig != 0);
+ }
+
+ if (*fclus == cluster)
+ return 0;
+
+ while (*fclus < cluster) {
+ /* prevent the infinite loop of cluster chain */
+ if (*fclus > limit) {
+ exfat_fs_error(sb,
+ "detected the cluster chain loop (i_pos %u)",
+ (*fclus));
+ return -EIO;
+ }
+
+ if (exfat_ent_get(sb, *dclus, &content))
+ return -EIO;
+
+ *last_dclus = *dclus;
+ *dclus = content;
+ (*fclus)++;
+
+ if (content == EXFAT_EOF_CLUSTER) {
+ if (!allow_eof) {
+ exfat_fs_error(sb,
+ "invalid cluster chain (i_pos %u, last_clus 0x%08x is EOF)",
+ *fclus, (*last_dclus));
+ return -EIO;
+ }
+
+ break;
+ }
+
+ if (!cache_contiguous(&cid, *dclus))
+ cache_init(&cid, *fclus, *dclus);
+ }
+
+ exfat_cache_add(inode, &cid);
+ return 0;
+}
--
2.17.1