fuse.c

linux下的用户文件系统fuse-2.5.2

/*
    FUSE: Filesystem in Userspace
    Copyright (C) 2001-2006  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 <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stddef.h>
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>
#include <errno.h>
#include <assert.h>
#include <pthread.h>
#include <sys/param.h>
#include <sys/uio.h>

#define FUSE_MAX_PATH 4096

#define FUSE_UNKNOWN_INO 0xffffffff

struct fuse_config {
    unsigned int uid;
    unsigned int gid;
    unsigned int  umask;
    double entry_timeout;
    double negative_timeout;
    double attr_timeout;
    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;
};

struct fuse {
    struct fuse_session *se;
    struct fuse_operations op;
    int compat;
    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;
    void *user_data;
    struct fuse_config conf;
};

struct node {
    struct node *name_next;
    struct node *id_next;
    fuse_ino_t nodeid;
    unsigned int generation;
    int refctr;
    fuse_ino_t parent;
    char *name;
    uint64_t nlookup;
    int open_count;
    int is_hidden;
};

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

static struct fuse_context *(*fuse_getcontext)(void) = NULL;

static int fuse_do_open(struct fuse *, char *, struct fuse_file_info *);
static void fuse_do_release(struct fuse *, char *, struct fuse_file_info *);
static int fuse_do_opendir(struct fuse *, char *, struct fuse_file_info *);
static int fuse_do_statfs(struct fuse *, char *, struct statvfs *);

#ifndef USE_UCLIBC
#define mutex_init(mut) pthread_mutex_init(mut, NULL)
#else
static void mutex_init(pthread_mutex_t *mut)
{
    pthread_mutexattr_t attr;
    pthread_mutexattr_init(&attr);
    pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ADAPTIVE_NP);
    pthread_mutex_init(mut, &attr);
    pthread_mutexattr_destroy(&attr);
}
#endif

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, 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, get_node(f, node->parent));
                free(node->name);
                node->name = NULL;
                node->parent = 0;
                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 parent,
                     const char *name)
{
    size_t hash = name_hash(f, parent, name);
    node->name = strdup(name);
    if (node->name == NULL)
        return -1;

    get_node(f, 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) {
        printf("delete: %llu\n", (unsigned long long) node->nodeid);
        fflush(stdout);
    }
    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++;
        if (!f->ctr)
            f->generation ++;
    } while (f->ctr == 0 || 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 == 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 = get_node(f, 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);
}

static void forget_node(struct fuse *f, fuse_ino_t nodeid, uint64_t nlookup)
{
    struct node *node;
    if (nodeid == FUSE_ROOT_ID)
        return;
    pthread_mutex_lock(&f->lock);
    node = get_node(f, nodeid);
    assert(node->nlookup >= nlookup);
    node->nlookup -= nlookup;
    if (!node->nlookup) {
        unhash_name(f, node);
        unref_node(f, node);
    }
    pthread_mutex_unlock(&f->lock);
}

static void remove_node(struct fuse *f, fuse_ino_t dir, const char *name)
{
    struct node *node;

    pthread_mutex_lock(&f->lock);
    node = lookup_node(f, dir, name);
    if (node != NULL)
        unhash_name(f, node);
    pthread_mutex_unlock(&f->lock);
}

static int rename_node(struct fuse *f, fuse_ino_t olddir, const char *oldname,
                        fuse_ino_t newdir, const char *newname, int hide)
{
    struct node *node;
    struct node *newnode;
    int err = 0;

    pthread_mutex_lock(&f->lock);
    node  = lookup_node(f, olddir, oldname);
    newnode  = lookup_node(f, newdir, newname);
    if (node == NULL)
        goto out;

    if (newnode != NULL) {
        if (hide) {
            fprintf(stderr, "fuse: hidden file got created during hiding\n");
            err = -EBUSY;
            goto out;
        }
        unhash_name(f, newnode);
    }

    unhash_name(f, node);
    if (hash_name(f, node, newdir, newname) == -1) {
        err = -ENOMEM;
        goto out;
    }

    if (hide)
        node->is_hidden = 1;

 out:
    pthread_mutex_unlock(&f->lock);
    return err;
}

static void set_stat(struct fuse *f, fuse_ino_t nodeid, struct stat *stbuf)
{
    if (!f->conf.use_ino)
        stbuf->st_ino = nodeid;
    if (f->conf.set_mode)
        stbuf->st_mode = (stbuf->st_mode & S_IFMT) | (0777 & ~f->conf.umask);
    if (f->conf.set_uid)
        stbuf->st_uid = f->conf.uid;
    if (f->conf.set_gid)
        stbuf->st_gid = f->conf.gid;
}

static int is_open(struct fuse *f, fuse_ino_t dir, const char *name)
{
    struct node *node;
    int isopen = 0;
    pthread_mutex_lock(&f->lock);
    node = lookup_node(f, dir, name);
    if (node && node->open_count > 0)
        isopen = 1;
    pthread_mutex_unlock(&f->lock);
    return isopen;
}

static char *hidden_name(struct fuse *f, fuse_ino_t dir, const char *oldname,
                        char *newname, size_t bufsize)
{
    struct stat buf;
    struct node *node;
    struct node *newnode;
    char *newpath;
    int res;
    int failctr = 10;

    if (!f->op.getattr)
        return NULL;

    do {
        pthread_mutex_lock(&f->lock);
        node = lookup_node(f, dir, oldname);
        if (node == NULL) {
            pthread_mutex_unlock(&f->lock);
            return NULL;
        }
        do {
            f->hidectr ++;
            snprintf(newname, bufsize, ".fuse_hidden%08x%08x",
                     (unsigned int) node->nodeid, f->hidectr);
            newnode = lookup_node(f, dir, newname);
        } while(newnode);
        pthread_mutex_unlock(&f->lock);

        newpath = get_path_name(f, dir, newname);
        if (!newpath)
            break;

        res = f->op.getattr(newpath, &buf);
        if (res != 0)
            break;
        free(newpath);
        newpath = NULL;
    } while(--failctr);

    return newpath;
}

static int hide_node(struct fuse *f, const char *oldpath, fuse_ino_t dir,
                     const char *oldname)
{
    char newname[64];
    char *newpath;
    int err = -EBUSY;

    if (f->op.rename && f->op.unlink) {
        newpath = hidden_name(f, dir, oldname, newname, sizeof(newname));
        if (newpath) {
            int res = f->op.rename(oldpath, newpath);
            if (res == 0)
                err = rename_node(f, dir, oldname, dir, newname, 1);
            free(newpath);
        }
    }
    return err;
}

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));
    if (fi && f->op.fgetattr)
        res = f->op.fgetattr(path, &e->attr, fi);
    else
        res = f->op.getattr(path, &e->attr);
    if (res == 0) {
        struct node *node;

        node = find_node(f, nodeid, name);
        if (node == NULL)
            res = -ENOMEM;
        else {
            e->ino = node->nodeid;
            e->generation = node->generation;
            e->entry_timeout = f->conf.entry_timeout;
            e->attr_timeout = f->conf.attr_timeout;
            set_stat(f, e->ino, &e->attr);
            if (f->conf.debug) {
                printf("   NODEID: %lu\n", (unsigned long) e->ino);
                fflush(stdout);
            }
        }
    }
    return res;
}

static struct fuse *req_fuse(fuse_req_t req)
{
    return (struct fuse *) fuse_req_userdata(req);
}

static struct fuse *req_fuse_prepare(fuse_req_t req)
{
    struct fuse_context *c = fuse_get_context();
    const struct fuse_ctx *ctx = fuse_req_ctx(req);
    c->fuse = req_fuse(req);
    c->uid = ctx->uid;
    c->gid = ctx->gid;
    c->pid = ctx->pid;
    c->private_data = c->fuse->user_data;

    return c->fuse;
}

static inline void reply_err(fuse_req_t req, int err)
{
    /* fuse_reply_err() uses non-negated errno values */
    fuse_reply_err(req, -err);
}

static void reply_entry(fuse_req_t req, const struct fuse_entry_param *e,