fuse.c

UNIX/LINUX下面的用户文件系统

/*
    FUSE: Filesystem in Userspace
    Copyright (C) 2001-2007  Miklos Szeredi <[e-mail]>

    This program can be distributed under the terms of the GNU LGPL.
    See the file COPYING.LIB
*/


/* For pthread_rwlock_t */
#define _GNU_SOURCE

#include "fuse_i.h"
#include "fuse_lowlevel.h"
#include "fuse_opt.h"
#include "fuse_misc.h"
#include "fuse_common_compat.h"
#include "fuse_compat.h"

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stddef.h>
#include <unistd.h>
#include <time.h>
#include <fcntl.h>
#include <limits.h>
#include <errno.h>
#include <signal.h>
#include <dlfcn.h>
#include <assert.h>
#include <sys/param.h>
#include <sys/uio.h>
#include <sys/time.h>

#define FUSE_MAX_PATH 4096
#define FUSE_DEFAULT_INTR_SIGNAL SIGUSR1

#define FUSE_UNKNOWN_INO 0xffffffff
#define OFFSET_MAX 0x7fffffffffffffffLL

struct fuse_config {
    unsigned int uid;
    unsigned int gid;
    unsigned int  umask;
    double entry_timeout;
    double negative_timeout;
    double attr_timeout;
    double ac_attr_timeout;
    int ac_attr_timeout_set;
    int debug;
    int hard_remove;
    int use_ino;
    int readdir_ino;
    int set_mode;
    int set_uid;
    int set_gid;
    int direct_io;
    int kernel_cache;
    int auto_cache;
    int intr;
    int intr_signal;
    int help;
    char *modules;
};

struct fuse_fs {
    struct fuse_operations op;
    struct fuse_module *m;
    void *user_data;
    int compat;
};

struct fusemod_so {
    void *handle;
    int ctr;
};

struct fuse {
    struct fuse_session *se;
    struct node **name_table;
    size_t name_table_size;
    struct node **id_table;
    size_t id_table_size;
    fuse_ino_t ctr;
    unsigned int generation;
    unsigned int hidectr;
    pthread_mutex_t lock;
    pthread_rwlock_t tree_lock;
    struct fuse_config conf;
    int intr_installed;
    struct fuse_fs *fs;
};

struct lock {
    int type;
    off_t start;
    off_t end;
    pid_t pid;
    uint64_t owner;
    struct lock *next;
};

struct node {
    struct node *name_next;
    struct node *id_next;
    fuse_ino_t nodeid;
    unsigned int generation;
    int refctr;
    struct node *parent;
    char *name;
    uint64_t nlookup;
    int open_count;
    int is_hidden;
    struct timespec stat_updated;
    struct timespec mtime;
    off_t size;
    int cache_valid;
    struct lock *locks;
};

struct fuse_dh {
    pthread_mutex_t lock;
    struct fuse *fuse;
    fuse_req_t req;
    char *contents;
    int allocated;
    unsigned len;
    unsigned size;
    unsigned needlen;
    int filled;
    uint64_t fh;
    int error;
    fuse_ino_t nodeid;
};

/* old dir handle */
struct fuse_dirhandle {
    fuse_fill_dir_t filler;
    void *buf;
};

struct fuse_context_i {
    struct fuse_context ctx;
    fuse_req_t req;
};

static pthread_key_t fuse_context_key;
static pthread_mutex_t fuse_context_lock = PTHREAD_MUTEX_INITIALIZER;
static int fuse_context_ref;
static struct fusemod_so *fuse_current_so;
static struct fuse_module *fuse_modules;

static int fuse_load_so_name(const char *soname)
{
    struct fusemod_so *so;

    so = calloc(1, sizeof(struct fusemod_so));
    if (!so) {
        fprintf(stderr, "fuse: memory allocation failed\n");
        return -1;
    }

    fuse_current_so = so;
    so->handle = dlopen(soname, RTLD_NOW);
    fuse_current_so = NULL;
    if (!so->handle) {
        fprintf(stderr, "fuse: %s\n", dlerror());
        goto err;
    }
    if (!so->ctr) {
        fprintf(stderr, "fuse: %s did not register any modules", soname);
        goto err;
    }
    return 0;

 err:
    if (so->handle)
        dlclose(so->handle);
    free(so);
    return -1;
}

static int fuse_load_so_module(const char *module)
{
    int res;
    char *soname = malloc(strlen(module) + 64);
    if (!soname) {
        fprintf(stderr, "fuse: memory allocation failed\n");
        return -1;
    }
    sprintf(soname, "libfusemod_%s.so", module);
    res = fuse_load_so_name(soname);
    free(soname);
    return res;
}

static struct fuse_module *fuse_find_module(const char *module)
{
    struct fuse_module *m;
    for (m = fuse_modules; m; m = m->next) {
        if (strcmp(module, m->name) == 0) {
            m->ctr++;
            break;
        }
    }
    return m;
}

static struct fuse_module *fuse_get_module(const char *module)
{
    struct fuse_module *m;

    pthread_mutex_lock(&fuse_context_lock);
    m = fuse_find_module(module);
    if (!m) {
        int err = fuse_load_so_module(module);
        if (!err)
            m = fuse_find_module(module);
    }
    pthread_mutex_unlock(&fuse_context_lock);
    return m;
}

static void fuse_put_module(struct fuse_module *m)
{
    pthread_mutex_lock(&fuse_context_lock);
    assert(m->ctr > 0);
    m->ctr--;
    if (!m->ctr && m->so) {
        struct fusemod_so *so = m->so;
        assert(so->ctr > 0);
        so->ctr--;
        if (!so->ctr) {
            struct fuse_module **mp;
            for (mp = &fuse_modules; *mp;) {
                if ((*mp)->so == so)
                    *mp = (*mp)->next;
                else
                    mp = &(*mp)->next;
            }
            dlclose(so->handle);
            free(so);
        }
    }
    pthread_mutex_unlock(&fuse_context_lock);
}

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;
}

static struct node *get_node(struct fuse *f, fuse_ino_t nodeid)
{
    struct node *node = get_node_nocheck(f, nodeid);
    if (!node) {
        fprintf(stderr, "fuse internal error: node %llu not found\n",
                (unsigned long long) nodeid);
        abort();
    }
    return node;
}

static void free_node(struct node *node)
{
    free(node->name);
    free(node);
}

static void unhash_id(struct fuse *f, struct node *node)
{
    size_t hash = node->nodeid % f->id_table_size;
    struct node **nodep = &f->id_table[hash];

    for (; *nodep != NULL; nodep = &(*nodep)->id_next)
        if (*nodep == node) {
            *nodep = node->id_next;
            return;
        }
}

static void hash_id(struct fuse *f, struct node *node)
{
    size_t hash = node->nodeid % f->id_table_size;
    node->id_next = f->id_table[hash];
    f->id_table[hash] = node;
}

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;
}

static void unref_node(struct fuse *f, struct node *node);

static void unhash_name(struct fuse *f, struct node *node)
{
    if (node->name) {
        size_t hash = name_hash(f, node->parent->nodeid, node->name);
        struct node **nodep = &f->name_table[hash];

        for (; *nodep != NULL; nodep = &(*nodep)->name_next)
            if (*nodep == node) {
                *nodep = node->name_next;
                node->name_next = NULL;
                unref_node(f, node->parent);
                free(node->name);
                node->name = NULL;
                node->parent = NULL;
                return;
            }
        fprintf(stderr, "fuse internal error: unable to unhash node: %llu\n",
                (unsigned long long) node->nodeid);
        abort();
    }
}

static int hash_name(struct fuse *f, struct node *node, fuse_ino_t parentid,
                     const char *name)
{
    size_t hash = name_hash(f, parentid, name);
    struct node *parent = get_node(f, parentid);
    node->name = strdup(name);
    if (node->name == NULL)
        return -1;

    parent->refctr ++;
    node->parent = parent;
    node->name_next = f->name_table[hash];
    f->name_table[hash] = node;
    return 0;
}

static void delete_node(struct fuse *f, struct node *node)
{
    if (f->conf.debug)
        fprintf(stderr, "delete: %llu\n", (unsigned long long) node->nodeid);

    assert(!node->name);
    unhash_id(f, node);
    free_node(node);
}

static void unref_node(struct fuse *f, struct node *node)
{
    assert(node->refctr > 0);
    node->refctr --;
    if (!node->refctr)
        delete_node(f, node);
}

static fuse_ino_t next_id(struct fuse *f)
{
    do {
        f->ctr = (f->ctr + 1) & 0xffffffff;
        if (!f->ctr)
            f->generation ++;
    } while (f->ctr == 0 || f->ctr == FUSE_UNKNOWN_INO ||
             get_node_nocheck(f, f->ctr) != NULL);
    return f->ctr;
}

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;
}

static struct node *find_node(struct fuse *f, fuse_ino_t parent,
                              const char *name)
{
    struct node *node;

    pthread_mutex_lock(&f->lock);
    node = lookup_node(f, parent, name);
    if (node == NULL) {
        node = (struct node *) calloc(1, sizeof(struct node));
        if (node == NULL)
            goto out_err;

        node->refctr = 1;
        node->nodeid = next_id(f);
        node->open_count = 0;
        node->is_hidden = 0;
        node->generation = f->generation;
        if (hash_name(f, node, parent, name) == -1) {
            free(node);
            node = NULL;
            goto out_err;
        }
        hash_id(f, node);
    }
    node->nlookup ++;
 out_err:
    pthread_mutex_unlock(&f->lock);
    return node;
}

static char *add_name(char *buf, char *s, const char *name)
{
    size_t len = strlen(name);
    s -= len;
    if (s <= buf) {
        fprintf(stderr, "fuse: path too long: ...%s\n", s + len);
        return NULL;
    }
    strncpy(s, name, len);
    s--;
    *s = '/';

    return s;
}

static char *get_path_name(struct fuse *f, fuse_ino_t nodeid, const char *name)
{
    char buf[FUSE_MAX_PATH];
    char *s = buf + FUSE_MAX_PATH - 1;
    struct node *node;

    *s = '\0';

    if (name != NULL) {
        s = add_name(buf, s, name);
        if (s == NULL)
            return NULL;
    }

    pthread_mutex_lock(&f->lock);
    for (node = get_node(f, nodeid); node && node->nodeid != FUSE_ROOT_ID;
         node = node->parent) {
        if (node->name == NULL) {
            s = NULL;
            break;
        }

        s = add_name(buf, s, node->name);
        if (s == NULL)
            break;
    }
    pthread_mutex_unlock(&f->lock);

    if (node == NULL || s == NULL)
        return NULL;
    else if (*s == '\0')
        return strdup("/");
    else
        return strdup(s);
}

static char *get_path(struct fuse *f, fuse_ino_t nodeid)
{
    return get_path_name(f, nodeid, NULL);
}