Add filesystem stacking support to high level API

2 files changed, 1356 insertions, 0 deletions

diff --git a/lib/modules/iconv.c b/lib/modules/iconv.c
new file mode 100644
index 0000000..eec0205
--- /dev/null
+++ b/lib/modules/iconv.c
@@ -0,0 +1,701 @@
+#define FUSE_USE_VERSION 26
+#define _FILE_OFFSET_BITS 64
+
+#include <fuse.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <errno.h>
+#include <iconv.h>
+#include <pthread.h>
+#include <locale.h>
+#include <langinfo.h>
+
+struct iconv {
+    struct fuse_fs *next;
+    pthread_mutex_t lock;
+    char *from_code;
+    char *to_code;
+    iconv_t tofs;
+    iconv_t fromfs;
+};
+
+struct iconv_dh {
+    struct iconv *ic;
+    void *prev_buf;
+    fuse_fill_dir_t prev_filler;
+};
+
+static struct iconv *iconv_get(void)
+{
+    return fuse_get_context()->private_data;
+}
+
+static int iconv_convpath(struct iconv *ic, const char *path, char **newpathp,
+                          int fromfs)
+{
+    size_t pathlen = strlen(path);
+    size_t newpathlen = pathlen; /* FIXME after testing */
+    char *newpath = malloc(newpathlen + 1);
+    size_t plen = newpathlen;
+    char *p = newpath;
+    size_t res;
+    int err;
+
+    if (!newpath)
+        return -ENOMEM;
+
+    pthread_mutex_lock(&ic->lock);
+    do {
+        res = iconv(fromfs ? ic->fromfs : ic->tofs, (char **) &path, &pathlen,
+                    &p, &plen);
+        if (res == (size_t) -1) {
+            char *tmp;
+            size_t inc;
+
+            err = -EILSEQ;
+            if (errno != E2BIG)
+                goto err;
+
+            inc = (pathlen + 1) * 4;
+            newpathlen += inc;
+            tmp = realloc(newpath, newpathlen + 1);
+            err = -ENOMEM;
+            if (!tmp)
+                goto err;
+
+            p = tmp + (p - newpath);
+            plen += inc;
+            newpath = tmp;
+        }
+    } while (res == (size_t) -1);
+    pthread_mutex_unlock(&ic->lock);
+    *p = '\0';
+    *newpathp = newpath;
+    return 0;
+
+ err:
+    iconv(fromfs ? ic->fromfs : ic->tofs, NULL, NULL, NULL, NULL);
+    pthread_mutex_unlock(&ic->lock);
+    free(newpath);
+    return err;
+}
+
+static int iconv_getattr(const char *path, struct stat *stbuf)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_getattr(ic->next, newpath, stbuf);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_fgetattr(const char *path, struct stat *stbuf,
+                          struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_fgetattr(ic->next, newpath, stbuf, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_access(const char *path, int mask)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_access(ic->next, newpath, mask);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_readlink(const char *path, char *buf, size_t size)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_readlink(ic->next, newpath, buf, size);
+        if (!err) {
+            char *newlink;
+            err = iconv_convpath(ic, buf, &newlink, 1);
+            if (!err) {
+                strncpy(buf, newlink, size - 1);
+                buf[size - 1] = '\0';
+                free(newlink);
+            }
+        }
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_opendir(const char *path, struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_opendir(ic->next, newpath, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_dir_fill(void *buf, const char *name,
+                          const struct stat *stbuf, off_t off)
+{
+    struct iconv_dh *dh = buf;
+    char *newname;
+    int res = 0;
+    if (iconv_convpath(dh->ic, name, &newname, 1) == 0) {
+        res = dh->prev_filler(dh->prev_buf, newname, stbuf, off);
+        free(newname);
+    }
+    return res;
+}
+
+static int iconv_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
+                         off_t offset, struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        struct iconv_dh dh;
+        dh.ic = ic;
+        dh.prev_buf = buf;
+        dh.prev_filler = filler;
+        err = fuse_fs_readdir(ic->next, newpath, &dh, iconv_dir_fill, offset,
+                              fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_releasedir(const char *path, struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_releasedir(ic->next, newpath, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_mknod(const char *path, mode_t mode, dev_t rdev)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_mknod(ic->next, newpath, mode, rdev);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_mkdir(const char *path, mode_t mode)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_mkdir(ic->next, newpath, mode);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_unlink(const char *path)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_unlink(ic->next, newpath);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_rmdir(const char *path)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_rmdir(ic->next, newpath);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_symlink(const char *from, const char *to)
+{
+    struct iconv *ic = iconv_get();
+    char *newfrom;
+    char *newto;
+    int err = iconv_convpath(ic, from, &newfrom, 0);
+    if (!err) {
+        err = iconv_convpath(ic, to, &newto, 0);
+        if (!err) {
+            err = fuse_fs_symlink(ic->next, newfrom, newto);
+            free(newto);
+        }
+        free(newfrom);
+    }
+    return err;
+}
+
+static int iconv_rename(const char *from, const char *to)
+{
+    struct iconv *ic = iconv_get();
+    char *newfrom;
+    char *newto;
+    int err = iconv_convpath(ic, from, &newfrom, 0);
+    if (!err) {
+        err = iconv_convpath(ic, to, &newto, 0);
+        if (!err) {
+            err = fuse_fs_rename(ic->next, newfrom, newto);
+            free(newto);
+        }
+        free(newfrom);
+    }
+    return err;
+}
+
+static int iconv_link(const char *from, const char *to)
+{
+    struct iconv *ic = iconv_get();
+    char *newfrom;
+    char *newto;
+    int err = iconv_convpath(ic, from, &newfrom, 0);
+    if (!err) {
+        err = iconv_convpath(ic, to, &newto, 0);
+        if (!err) {
+            err = fuse_fs_link(ic->next, newfrom, newto);
+            free(newto);
+        }
+        free(newfrom);
+    }
+    return err;
+}
+
+static int iconv_chmod(const char *path, mode_t mode)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_chmod(ic->next, newpath, mode);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_chown(const char *path, uid_t uid, gid_t gid)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_chown(ic->next, newpath, uid, gid);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_truncate(const char *path, off_t size)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_truncate(ic->next, newpath, size);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_ftruncate(const char *path, off_t size,
+                           struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_ftruncate(ic->next, newpath, size, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_utimens(const char *path, const struct timespec ts[2])
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_utimens(ic->next, newpath, ts);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_create(const char *path, mode_t mode,
+                        struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_create(ic->next, newpath, mode, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_open_file(const char *path, struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_open(ic->next, newpath, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_read(const char *path, char *buf, size_t size, off_t offset,
+                    struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_read(ic->next, newpath, buf, size, offset, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_write(const char *path, const char *buf, size_t size,
+                       off_t offset, struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_write(ic->next, newpath, buf, size, offset, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_statfs(const char *path, struct statvfs *stbuf)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_statfs(ic->next, newpath, stbuf);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_flush(const char *path, struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_flush(ic->next, newpath, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_release(const char *path, struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_release(ic->next, newpath, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_fsync(const char *path, int isdatasync,
+                       struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_fsync(ic->next, newpath, isdatasync, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_fsyncdir(const char *path, int isdatasync,
+                          struct fuse_file_info *fi)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_fsyncdir(ic->next, newpath, isdatasync, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_setxattr(const char *path, const char *name,
+                          const char *value, size_t size, int flags)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_setxattr(ic->next, newpath, name, value, size, flags);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_getxattr(const char *path, const char *name, char *value,
+                          size_t size)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_getxattr(ic->next, newpath, name, value, size);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_listxattr(const char *path, char *list, size_t size)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_listxattr(ic->next, newpath, list, size);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_removexattr(const char *path, const char *name)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_removexattr(ic->next, newpath, name);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_lock(const char *path, struct fuse_file_info *fi, int cmd,
+                      struct flock *lock)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_lock(ic->next, newpath, fi, cmd, lock);
+        free(newpath);
+    }
+    return err;
+}
+
+static int iconv_bmap(const char *path, size_t blocksize, uint64_t *idx)
+{
+    struct iconv *ic = iconv_get();
+    char *newpath;
+    int err = iconv_convpath(ic, path, &newpath, 0);
+    if (!err) {
+        err = fuse_fs_bmap(ic->next, newpath, blocksize, idx);
+        free(newpath);
+    }
+    return err;
+}
+
+static void *iconv_init(struct fuse_conn_info *conn)
+{
+    struct iconv *ic = iconv_get();
+    fuse_fs_init(ic->next, conn);
+    return ic;
+}
+
+static void iconv_destroy(void *data)
+{
+    struct iconv *ic = data;
+    fuse_fs_destroy(ic->next);
+    iconv_close(ic->tofs);
+    iconv_close(ic->fromfs);
+    pthread_mutex_destroy(&ic->lock);
+    free(ic->from_code);
+    free(ic->to_code);
+    free(ic);
+}
+
+static struct fuse_operations iconv_oper = {
+    .destroy	= iconv_destroy,
+    .init	= iconv_init,
+    .getattr	= iconv_getattr,
+    .fgetattr	= iconv_fgetattr,
+    .access	= iconv_access,
+    .readlink	= iconv_readlink,
+    .opendir	= iconv_opendir,
+    .readdir	= iconv_readdir,
+    .releasedir	= iconv_releasedir,
+    .mknod	= iconv_mknod,
+    .mkdir	= iconv_mkdir,
+    .symlink	= iconv_symlink,
+    .unlink	= iconv_unlink,
+    .rmdir	= iconv_rmdir,
+    .rename	= iconv_rename,
+    .link	= iconv_link,
+    .chmod	= iconv_chmod,
+    .chown	= iconv_chown,
+    .truncate	= iconv_truncate,
+    .ftruncate	= iconv_ftruncate,
+    .utimens	= iconv_utimens,
+    .create	= iconv_create,
+    .open	= iconv_open_file,
+    .read	= iconv_read,
+    .write	= iconv_write,
+    .statfs	= iconv_statfs,
+    .flush	= iconv_flush,
+    .release	= iconv_release,
+    .fsync	= iconv_fsync,
+    .fsyncdir	= iconv_fsyncdir,
+    .setxattr	= iconv_setxattr,
+    .getxattr	= iconv_getxattr,
+    .listxattr	= iconv_listxattr,
+    .removexattr= iconv_removexattr,
+    .lock	= iconv_lock,
+    .bmap	= iconv_bmap,
+};
+
+static struct fuse_opt iconv_opts[] = {
+    FUSE_OPT_KEY("-h", 0),
+    FUSE_OPT_KEY("--help", 0),
+    { "from_code=%s", offsetof(struct iconv, from_code), 0 },
+    { "to_code=%s", offsetof(struct iconv, to_code), 1 },
+    FUSE_OPT_END
+};
+
+static void iconv_help(void)
+{
+    char *old = strdup(setlocale(LC_CTYPE, ""));
+    char *charmap = strdup(nl_langinfo(CODESET));
+    setlocale(LC_CTYPE, old);
+    free(old);
+    fprintf(stderr,
+"    -o from_code=CHARSET   original encoding of file names (default: UTF-8)\n"
+"    -o to_code=CHARSET     new encoding of the file names (default: %s)\n",
+            charmap);
+    free(charmap);
+}
+
+static int iconv_opt_proc(void *data, const char *arg, int key,
+                           struct fuse_args *outargs)
+{
+    (void) data; (void) arg; (void) outargs;
+
+    if (!key) {
+        iconv_help();
+        return -1;
+    }
+
+    return 1;
+}
+
+static struct fuse_fs *iconv_new(struct fuse_args *args,
+                                  struct fuse_fs *next[])
+{
+    struct fuse_fs *fs;
+    struct iconv *ic;
+    char *old = NULL;
+    const char *from;
+    const char *to;
+
+    ic = calloc(1, sizeof(struct iconv));
+    if (ic == NULL) {
+        fprintf(stderr, "fuse-iconv: memory allocation failed\n");
+        return NULL;
+    }
+
+    if (fuse_opt_parse(args, ic, iconv_opts, iconv_opt_proc) == -1)
+        goto out_free;
+
+    if (!next[0] || next[1]) {
+        fprintf(stderr, "fuse-iconv: exactly one next filesystem required\n");
+        goto out_free;
+    }
+
+    from = ic->from_code ? ic->from_code : "UTF-8";
+    to = ic->to_code ? ic->to_code : "";
+    /* FIXME: detect charset equivalence? */
+    if (!to[0])
+        old = strdup(setlocale(LC_CTYPE, ""));
+    ic->tofs = iconv_open(from, to);
+    if (ic->tofs == (iconv_t) -1) {
+        fprintf(stderr, "fuse-iconv: cannot convert from %s to %s\n",
+                to, from);
+        goto out_free;
+    }
+    ic->fromfs = iconv_open(to, from);
+    if (ic->tofs == (iconv_t) -1) {
+        fprintf(stderr, "fuse-iconv: cannot convert from %s to %s\n",
+                from, to);
+        goto out_iconv_close_to;
+    }
+    if (old) {
+        setlocale(LC_CTYPE, old);
+        free(old);
+    }
+
+    ic->next = next[0];
+    fs = fuse_fs_new(&iconv_oper, sizeof(iconv_oper), ic);
+    if (!fs)
+        goto out_iconv_close_from;
+
+    return fs;
+
+ out_iconv_close_from:
+    iconv_close(ic->fromfs);
+ out_iconv_close_to:
+    iconv_close(ic->tofs);
+ out_free:
+    free(ic->from_code);
+    free(ic->to_code);
+    free(ic);
+    return NULL;
+}
+
+FUSE_REGISTER_MODULE(iconv, iconv_new);
diff --git a/lib/modules/subdir.c b/lib/modules/subdir.c
new file mode 100644
index 0000000..eaba99d
--- /dev/null
+++ b/lib/modules/subdir.c
@@ -0,0 +1,655 @@
+#define FUSE_USE_VERSION 26
+#define _FILE_OFFSET_BITS 64
+
+#include <fuse.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <errno.h>
+
+struct subdir {
+    char *base;
+    size_t baselen;
+    int rellinks;
+    struct fuse_fs *next;
+};
+
+static struct subdir *subdir_get(void)
+{
+    return fuse_get_context()->private_data;
+}
+
+static char *subdir_addpath(struct subdir *d, const char *path)
+{
+    unsigned newlen = d->baselen + strlen(path);
+    char *newpath = malloc(newlen + 2);
+    if (newpath) {
+        if (path[0] == '/')
+            path++;
+        strcpy(newpath, d->base);
+        strcpy(newpath + d->baselen, path);
+        if (!newpath[0])
+            strcpy(newpath, ".");
+    }
+    return newpath;
+}
+
+static int subdir_getattr(const char *path, struct stat *stbuf)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_getattr(d->next, newpath, stbuf);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_fgetattr(const char *path, struct stat *stbuf,
+                           struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_fgetattr(d->next, newpath, stbuf, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_access(const char *path, int mask)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_access(d->next, newpath, mask);
+        free(newpath);
+    }
+    return err;
+}
+
+
+static int count_components(const char *p)
+{
+    int ctr;
+
+    for (; *p == '/'; p++);
+    for (ctr = 0; *p; ctr++) {
+        for (; *p && *p != '/'; p++);
+        for (; *p == '/'; p++);
+    }
+    return ctr;
+}
+
+static void strip_common(const char **sp, const char **tp)
+{
+    const char *s = *sp;
+    const char *t = *tp;
+    do {
+        for (; *s == '/'; s++);
+        for (; *t == '/'; t++);
+        *tp = t;
+        *sp = s;
+        for (; *s == *t && *s && *s != '/'; s++, t++);
+    } while ((*s == *t && *s) || (!*s && *t == '/') || (*s == '/' && !*t));
+}
+
+static void transform_symlink(struct subdir *d, const char *path,
+                              char *buf, size_t size)
+{
+    const char *l = buf;
+    size_t llen;
+    char *s;
+    int dotdots;
+    int i;
+
+    if (l[0] != '/' || d->base[0] != '/')
+        return;
+
+    strip_common(&l, &path);
+    if (l - buf < d->baselen)
+        return;
+
+    dotdots = count_components(path);
+    if (!dotdots)
+        return;
+    dotdots--;
+
+    llen = strlen(l);
+    if (dotdots * 3 + llen + 2 > size)
+        return;
+
+    s = buf + dotdots * 3;
+    if (llen)
+        memmove(s, l, llen + 1);
+    else if (!dotdots)
+        strcpy(s, ".");
+    else
+        *s = '\0';
+
+    for (s = buf, i = 0; i < dotdots; i++, s += 3)
+        memcpy(s, "../", 3);
+}
+
+
+static int subdir_readlink(const char *path, char *buf, size_t size)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_readlink(d->next, newpath, buf, size);
+        if (!err && d->rellinks)
+            transform_symlink(d, newpath, buf, size);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_opendir(const char *path, struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_opendir(d->next, newpath, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_readdir(const char *path, void *buf,
+                          fuse_fill_dir_t filler, off_t offset,
+                          struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_readdir(d->next, newpath, buf, filler, offset, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_releasedir(const char *path, struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_releasedir(d->next, newpath, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_mknod(const char *path, mode_t mode, dev_t rdev)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_mknod(d->next, newpath, mode, rdev);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_mkdir(const char *path, mode_t mode)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_mkdir(d->next, newpath, mode);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_unlink(const char *path)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_unlink(d->next, newpath);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_rmdir(const char *path)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_rmdir(d->next, newpath);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_symlink(const char *from, const char *path)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_symlink(d->next, from, newpath);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_rename(const char *from, const char *to)
+{
+    struct subdir *d = subdir_get();
+    char *newfrom = subdir_addpath(d, from);
+    char *newto = subdir_addpath(d, to);
+    int err = -ENOMEM;
+    if (newfrom && newto)
+        err = fuse_fs_rename(d->next, newfrom, newto);
+    free(newfrom);
+    free(newto);
+    return err;
+}
+
+static int subdir_link(const char *from, const char *to)
+{
+    struct subdir *d = subdir_get();
+    char *newfrom = subdir_addpath(d, from);
+    char *newto = subdir_addpath(d, to);
+    int err = -ENOMEM;
+    if (newfrom && newto)
+        err = fuse_fs_link(d->next, newfrom, newto);
+    free(newfrom);
+    free(newto);
+    return err;
+}
+
+static int subdir_chmod(const char *path, mode_t mode)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_chmod(d->next, newpath, mode);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_chown(const char *path, uid_t uid, gid_t gid)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_chown(d->next, newpath, uid, gid);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_truncate(const char *path, off_t size)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_truncate(d->next, newpath, size);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_ftruncate(const char *path, off_t size,
+                         struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_ftruncate(d->next, newpath, size, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_utimens(const char *path, const struct timespec ts[2])
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_utimens(d->next, newpath, ts);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_create(const char *path, mode_t mode, struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_create(d->next, newpath, mode, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_open(const char *path, struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_open(d->next, newpath, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_read(const char *path, char *buf, size_t size, off_t offset,
+                    struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_read(d->next, newpath, buf, size, offset, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_write(const char *path, const char *buf, size_t size,
+                     off_t offset, struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_write(d->next, newpath, buf, size, offset, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_statfs(const char *path, struct statvfs *stbuf)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_statfs(d->next, newpath, stbuf);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_flush(const char *path, struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_flush(d->next, newpath, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_release(const char *path, struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_release(d->next, newpath, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_fsync(const char *path, int isdatasync,
+                        struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_fsync(d->next, newpath, isdatasync, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_fsyncdir(const char *path, int isdatasync,
+                           struct fuse_file_info *fi)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_fsyncdir(d->next, newpath, isdatasync, fi);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_setxattr(const char *path, const char *name, const char *value,
+                        size_t size, int flags)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_setxattr(d->next, newpath, name, value, size, flags);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_getxattr(const char *path, const char *name, char *value,
+                    size_t size)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_getxattr(d->next, newpath, name, value, size);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_listxattr(const char *path, char *list, size_t size)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_listxattr(d->next, newpath, list, size);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_removexattr(const char *path, const char *name)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_removexattr(d->next, newpath, name);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_lock(const char *path, struct fuse_file_info *fi, int cmd,
+                    struct flock *lock)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_lock(d->next, newpath, fi, cmd, lock);
+        free(newpath);
+    }
+    return err;
+}
+
+static int subdir_bmap(const char *path, size_t blocksize, uint64_t *idx)
+{
+    struct subdir *d = subdir_get();
+    char *newpath = subdir_addpath(d, path);
+    int err = -ENOMEM;
+    if (newpath) {
+        err = fuse_fs_bmap(d->next, newpath, blocksize, idx);
+        free(newpath);
+    }
+    return err;
+}
+
+static void *subdir_init(struct fuse_conn_info *conn)
+{
+    struct subdir *d = subdir_get();
+    fuse_fs_init(d->next, conn);
+    return d;
+}
+
+static void subdir_destroy(void *data)
+{
+    struct subdir *d = data;
+    fuse_fs_destroy(d->next);
+    free(d->base);
+    free(d);
+}
+
+static struct fuse_operations subdir_oper = {
+    .destroy	= subdir_destroy,
+    .init	= subdir_init,
+    .getattr	= subdir_getattr,
+    .fgetattr	= subdir_fgetattr,
+    .access	= subdir_access,
+    .readlink	= subdir_readlink,
+    .opendir	= subdir_opendir,
+    .readdir	= subdir_readdir,
+    .releasedir	= subdir_releasedir,
+    .mknod	= subdir_mknod,
+    .mkdir	= subdir_mkdir,
+    .symlink	= subdir_symlink,
+    .unlink	= subdir_unlink,
+    .rmdir	= subdir_rmdir,
+    .rename	= subdir_rename,
+    .link	= subdir_link,
+    .chmod	= subdir_chmod,
+    .chown	= subdir_chown,
+    .truncate	= subdir_truncate,
+    .ftruncate	= subdir_ftruncate,
+    .utimens	= subdir_utimens,
+    .create	= subdir_create,
+    .open	= subdir_open,
+    .read	= subdir_read,
+    .write	= subdir_write,
+    .statfs	= subdir_statfs,
+    .flush	= subdir_flush,
+    .release	= subdir_release,
+    .fsync	= subdir_fsync,
+    .fsyncdir	= subdir_fsyncdir,
+    .setxattr	= subdir_setxattr,
+    .getxattr	= subdir_getxattr,
+    .listxattr	= subdir_listxattr,
+    .removexattr= subdir_removexattr,
+    .lock	= subdir_lock,
+    .bmap	= subdir_bmap,
+};
+
+static struct fuse_opt subdir_opts[] = {
+    FUSE_OPT_KEY("-h", 0),
+    FUSE_OPT_KEY("--help", 0),
+    { "subdir=%s", offsetof(struct subdir, base), 0 },
+    { "rellinks", offsetof(struct subdir, rellinks), 1 },
+    { "norellinks", offsetof(struct subdir, rellinks), 0 },
+    FUSE_OPT_END
+};
+
+static void subdir_help(void)
+{
+    fprintf(stderr,
+"    -o subdir=DIR          prepend this directory to all paths (mandatory)\n"
+"    -o [no]rellinks        transform absolute symlinks to relative\n");
+}
+
+static int subdir_opt_proc(void *data, const char *arg, int key,
+                           struct fuse_args *outargs)
+{
+    (void) data; (void) arg; (void) outargs;
+
+    if (!key) {
+        subdir_help();
+        return -1;
+    }
+
+    return 1;
+}
+
+static struct fuse_fs *subdir_new(struct fuse_args *args,
+                                  struct fuse_fs *next[])
+{
+    struct fuse_fs *fs;
+    struct subdir *d;
+
+    d = calloc(1, sizeof(struct subdir));
+    if (d == NULL) {
+        fprintf(stderr, "fuse-subdir: memory allocation failed\n");
+        return NULL;
+    }
+
+    if (fuse_opt_parse(args, d, subdir_opts, subdir_opt_proc) == -1)
+        goto out_free;
+
+    if (!next[0] || next[1]) {
+        fprintf(stderr, "fuse-subdir: exactly one next filesystem required\n");
+        goto out_free;
+    }
+
+    if (!d->base) {
+        fprintf(stderr, "fuse-subdir: missing 'subdir' option\n");
+        goto out_free;
+    }
+
+    if (d->base[0] && d->base[strlen(d->base)-1] != '/') {
+        char *tmp = realloc(d->base, strlen(d->base) + 2);
+        if (!tmp) {
+            fprintf(stderr, "fuse-subdir: memory allocation failed\n");
+            goto out_free;
+        }
+        d->base = tmp;
+        strcat(d->base, "/");
+    }
+    d->baselen = strlen(d->base);
+    d->next = next[0];
+    fs = fuse_fs_new(&subdir_oper, sizeof(subdir_oper), d);
+    if (!fs)
+        goto out_free;
+    return fs;
+
+ out_free:
+    free(d->base);
+    free(d);
+    return NULL;
+}
+
+FUSE_REGISTER_MODULE(subdir, subdir_new);