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