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From e88345bbb9a4027033254933ee2e1cad9feab6d6 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Thu, 24 Jun 2021 16:00:04 +0800
Subject: [PATCH] crupesteam fat patch.
---
fs/fat/cache.c | 64 ++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 57 insertions(+), 7 deletions(-)
diff --git a/fs/fat/cache.c b/fs/fat/cache.c
index 738e427e2d21..4f32bfee6d27 100644
--- a/fs/fat/cache.c
+++ b/fs/fat/cache.c
@@ -15,11 +15,15 @@
/* this must be > 0. */
#define FAT_MAX_CACHE 8
+#define FAT_CACHE_PREV_CLUSTER_COUNT 8
+
struct fat_cache {
struct list_head cache_list;
int nr_contig; /* number of contiguous clusters */
int fcluster; /* cluster number in the file. */
int dcluster; /* cluster number on disk. */
+ int prev_clusters_count;
+ int prev_clusters[FAT_CACHE_PREV_CLUSTER_COUNT];
};
struct fat_cache_id {
@@ -27,6 +31,8 @@ struct fat_cache_id {
int nr_contig;
int fcluster;
int dcluster;
+ int prev_clusters_count;
+ int prev_clusters[FAT_CACHE_PREV_CLUSTER_COUNT];
};
static inline int fat_max_cache(struct inode *inode)
@@ -84,10 +90,17 @@ static int fat_cache_lookup(struct inode *inode, int fclus,
static struct fat_cache nohit = { .fcluster = 0, };
struct fat_cache *hit = &nohit, *p;
- int offset = -1;
+ int offset = INT_MIN;
spin_lock(&MSDOS_I(inode)->cache_lru_lock);
list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
+ if (p->fcluster > fclus &&
+ p->fcluster - p->prev_clusters_count <= fclus) {
+ hit = p;
+ offset = fclus - hit->fcluster;
+ break;
+ }
+
/* Find the cache of "fclus" or nearest cache. */
if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
hit = p;
@@ -107,7 +120,11 @@ static int fat_cache_lookup(struct inode *inode, int fclus,
cid->fcluster = hit->fcluster;
cid->dcluster = hit->dcluster;
*cached_fclus = cid->fcluster + offset;
- *cached_dclus = cid->dcluster + offset;
+
+ if (offset < 0)
+ *cached_dclus = hit->prev_clusters[hit->prev_clusters_count + offset];
+ else
+ *cached_dclus = cid->dcluster + offset;
}
spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
@@ -145,6 +162,8 @@ static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
cache = fat_cache_merge(inode, new);
if (cache == NULL) {
+ int i;
+
if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) {
MSDOS_I(inode)->nr_caches++;
spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
@@ -172,6 +191,10 @@ static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
cache->fcluster = new->fcluster;
cache->dcluster = new->dcluster;
cache->nr_contig = new->nr_contig;
+ cache->prev_clusters_count = new->prev_clusters_count;
+ for (i = 0; i < new->prev_clusters_count; i++) {
+ cache->prev_clusters[i] = new->prev_clusters[i];
+ }
}
out_update_lru:
fat_cache_update_lru(inode, cache);
@@ -220,6 +243,7 @@ static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
cid->fcluster = fclus;
cid->dcluster = dclus;
cid->nr_contig = 0;
+ cid->prev_clusters_count = 0;
}
int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
@@ -230,6 +254,10 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
struct fat_entry fatent;
struct fat_cache_id cid;
int nr;
+ int offset;
+ int prev_cluster[FAT_CACHE_PREV_CLUSTER_COUNT];
+ int prev_cluster_current = 0;
+ int prev_cluster_count = 0;
BUG_ON(MSDOS_I(inode)->i_start == 0);
@@ -244,12 +272,13 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
if (cluster == 0)
return 0;
- if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
- /*
- * dummy, always not contiguous
- * This is reinitialized by cache_init(), later.
- */
+ offset = fat_cache_lookup(inode, cluster, &cid, fclus, dclus);
+
+ if (offset == INT_MIN) {
cache_init(&cid, -1, -1);
+ } else if (offset < 0) {
+ nr = 0;
+ goto out;
}
fatent_init(&fatent);
@@ -278,10 +307,31 @@ int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
}
(*fclus)++;
*dclus = nr;
+
+ prev_cluster[prev_cluster_current++] = *dclus;
+ if (prev_cluster_count < FAT_CACHE_PREV_CLUSTER_COUNT) {
+ prev_cluster_count++;
+ }
+ prev_cluster_current %= FAT_CACHE_PREV_CLUSTER_COUNT;
+
if (!cache_contiguous(&cid, *dclus))
cache_init(&cid, *fclus, *dclus);
}
nr = 0;
+
+ if (cid.nr_contig + 1 < FAT_CACHE_PREV_CLUSTER_COUNT) {
+ int i;
+ int count = prev_cluster_count - cid.nr_contig - 1;
+ int start = ((prev_cluster_current - prev_cluster_count)
+ + FAT_CACHE_PREV_CLUSTER_COUNT) % FAT_CACHE_PREV_CLUSTER_COUNT;
+
+ cid.prev_clusters_count = count;
+
+ for (i = 0; i < count; i++) {
+ cid.prev_clusters[i] = prev_cluster[(start + i) % FAT_CACHE_PREV_CLUSTER_COUNT];
+ }
+ }
+
fat_cache_add(inode, &cid);
out:
fatent_brelse(&fatent);
--
2.32.0
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