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Date: Sun, 29 Dec 2019 15:23:40 +0100
From: Pali Rohár <pali.rohar@...il.com>
To: Namjae Jeon <namjae.jeon@...sung.com>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
gregkh@...uxfoundation.org, valdis.kletnieks@...edu, hch@....de,
sj1557.seo@...sung.com, linkinjeon@...il.com
Subject: Re: [PATCH v8 08/13] exfat: add exfat cache
Hello! This patch looks like a copy-pase of fat cache implementation.
It is possible to avoid duplicating code?
On Friday 20 December 2019 01:24:14 Namjae Jeon wrote:
> This adds the implementation of exfat cache.
>
> Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
> Signed-off-by: Sungjong Seo <sj1557.seo@...sung.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;
> +}
--
Pali Rohár
pali.rohar@...il.com
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