/* fuse fs的hash函数 */
static unsigned int name_hash(struct fuse *f, fuse_ino_t parent,
const char *name)
{
unsigned int hash = *name;
if (hash)
for (name += 1; *name != '\0'; name++)
hash = (hash << 5) - hash + *name;
return (hash + parent) % f->name_table_size;
}
/* 通过名字hash查找node信息*/
static struct node *lookup_node(struct fuse *f, fuse_ino_t parent,
const char *name)
{
size_t hash = name_hash(f, parent, name);
struct node *node;
for (node = f->name_table[hash]; node != NULL; node = node->name_next)
if (node->parent->nodeid == parent &&
strcmp(node->name, name) == 0)
return node;
return NULL;
}
/* 通过nodeid查找node信息*/
static struct node *get_node_nocheck(struct fuse *f, fuse_ino_t nodeid)
{
size_t hash = nodeid % f->id_table_size;
struct node *node;
for (node = f->id_table[hash]; node != NULL; node = node->id_next)
if (node->nodeid == nodeid)
return node;
return NULL;
}
/* 通过某一个目录项，你想递归获取全局路径 */
static int try_get_path(struct fuse *f, fuse_ino_t nodeid, const char *name,
char **path, struct node **wnodep, int ticket)
{
unsigned bufsize = 256;
char *buf;
char *s;
struct node *node;
struct node *wnode = NULL;
int err;
*path = NULL;
buf = malloc(bufsize);
if (buf == NULL)
return -ENOMEM;
s = buf + bufsize - 1;
*s = '\0';
if (name != NULL) {
s = add_name(&buf, &bufsize, s, name);
err = -ENOMEM;
if (s == NULL)
goto out_free;
}
if (wnodep) {
assert(ticket);
wnode = lookup_node(f, nodeid, name);
if (wnode) {
if (wnode->treelock != 0 ||
(wnode->ticket && wnode->ticket != ticket)) {
if (!wnode->ticket)
wnode->ticket = ticket;
err = -EAGAIN;
goto out_free;
}
wnode->treelock = -1;
wnode->ticket = 0;
}
}
/* 逆向遍历目录树，获取目录项的全局路径 */
err = 0;
for (node = get_node(f, nodeid); node->nodeid != FUSE_ROOT_ID;
node = node->parent) {
err = -ENOENT;
if (node->name == NULL || node->parent == NULL)
goto out_unlock;
err = -ENOMEM;
/* 长度不够将自动扩张，默认申请长度为256 */
s = add_name(&buf, &bufsize, s, node->name);
if (s == NULL)
goto out_unlock;
if (ticket) {
err = -EAGAIN;
if (node->treelock == -1 ||
(node->ticket && node->ticket != ticket))
goto out_unlock;
node->treelock++;
node->ticket = 0;
}
}
if (s[0])
memmove(buf, s, bufsize - (s - buf));
else
strcpy(buf, "/");
*path = buf;
if (wnodep)
*wnodep = wnode;
return 0;
out_unlock:
if (ticket)
unlock_path(f, nodeid, wnode, node, ticket);
out_free:
free(buf);
return err;
}
/* 获取下一个nodeid */
static fuse_ino_t next_id(struct fuse *f)
{
do {
f->ctr = (f->ctr + 1) & 0xffffffff;
if (!f->ctr)
f->generation ++; /* 如果32bit数以用完，将generation加1 */
} while (f->ctr == 0 || f->ctr == FUSE_UNKNOWN_INO ||
get_node_nocheck(f, f->ctr) != NULL);
return f->ctr;
}
/* 获取目录项的fuse_entry_param信息，如果目录项不存在则新建，并加入hash表
lookup、mknod、create等都调用了该方法 */
static int lookup_path(struct fuse *f, fuse_ino_t nodeid,
const char *name, const char *path,
struct fuse_entry_param *e, struct fuse_file_info *fi)
{
int res;
memset(e, 0, sizeof(struct fuse_entry_param));
/* 从这里可以看出 如果getattr接口返回错误，则整个过程将会出现问题，故在实现getattr时，即使获取不到文件的信息，也要填充entry的信息 */
if (fi)
res = fuse_fs_fgetattr(f->fs, path, &e->attr, fi);
else
res = fuse_fs_getattr(f->fs, path, &e->attr);
if (res == 0) {
struct node *node;
node = find_node(f, nodeid, name);
if (node == NULL)
res = -ENOMEM;
else {
/* 如果分配子目录项不成功，则返回父目录的信息 */
e->ino = node->nodeid;
e->generation = node->generation;
e->entry_timeout = f->conf.entry_timeout;
e->attr_timeout = f->conf.attr_timeout;
if (f->conf.auto_cache) {
pthread_mutex_lock(&f->lock);
update_stat(node, &e->attr);
pthread_mutex_unlock(&f->lock);
}
set_stat(f, e->ino, &e->attr);
if (f->conf.debug)
fprintf(stderr, " NODEID: %lu\n",
(unsigned long) e->ino);
}
}
return res;
}
static struct node *find_node(struct fuse *f, fuse_ino_t parent,
const char *name)
{
struct node *node;
pthread_mutex_lock(&f->lock);
if (!name)
node = get_node(f, parent);
else
node = lookup_node(f, parent, name);
if (node == NULL) {
node = (struct node *) calloc(1, sizeof(struct node));
if (node == NULL)
goto out_err;
if (f->conf.noforget)
node->nlookup = 1;
node->refctr = 1;
node->nodeid = next_id(f); /* 选择下一个使用的nodeid */
node->generation = f->generation;
node->open_count = 0;
node->is_hidden = 0;
node->treelock = 0;
node->ticket = 0;
if (hash_name(f, node, parent, name) == -1) { /* 加入路径名hash表 */
free(node);
node = NULL;
goto out_err;
}
hash_id(f, node); /* 加入nodeid hash表 */
}
node->nlookup ++;
out_err:
pthread_mutex_unlock(&f->lock);
return node;
}
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