add filesystem subtype support

There's a slight problem with filesystem type representation in fuse
based filesystems.

From the kernel's view, there are just two filesystem types: fuse and
fuseblk.  From the user's view there are lots of different filesystem
types.  The user is not even much concerned if the filesystem is fuse based
or not.  So there's a conflict of interest in how this should be
represented in fstab, mtab and /proc/mounts.

The current scheme is to encode the real filesystem type in the mount
source.  So an sshfs mount looks like this:

  sshfs#user@server:/   /mnt/server    fuse   rw,nosuid,nodev,...

This url-ish syntax works OK for sshfs and similar filesystems.  However
for block device based filesystems (ntfs-3g, zfs) it doesn't work, since
the kernel expects the mount source to be a real device name.

A possibly better scheme would be to encode the real type in the type
field as "type.subtype".  So fuse mounts would look like this:

  /dev/hda1       /mnt/windows   fuseblk.ntfs-3g   rw,...
  user@server:/   /mnt/server    fuse.sshfs        rw,nosuid,nodev,...

This patch adds the necessary code to the kernel so that this can be
correctly displayed in /proc/mounts.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/filesystems.c b/fs/filesystems.c
index 7a4f61aa05f8a63697be13231d69316ef5c365a9..f37f87262837aaf6e47526d4895a000f1f9024c2 100644 (file)
--- a/fs/filesystems.c
+++ b/fs/filesystems.c
@@ -41,11 +41,12 @@ void put_filesystem(struct file_system_type *fs)
        module_put(fs->owner);
 }
 
-static struct file_system_type **find_filesystem(const char *name)
+static struct file_system_type **find_filesystem(const char *name, unsigned len)
 {
        struct file_system_type **p;
        for (p=&file_systems; *p; p=&(*p)->next)
-               if (strcmp((*p)->name,name) == 0)
+               if (strlen((*p)->name) == len &&
+                   strncmp((*p)->name, name, len) == 0)
                        break;
        return p;
 }
@@ -68,11 +69,12 @@ int register_filesystem(struct file_system_type * fs)
        int res = 0;
        struct file_system_type ** p;
 
+       BUG_ON(strchr(fs->name, '.'));
        if (fs->next)
                return -EBUSY;
        INIT_LIST_HEAD(&fs->fs_supers);
        write_lock(&file_systems_lock);
-       p = find_filesystem(fs->name);
+       p = find_filesystem(fs->name, strlen(fs->name));
        if (*p)
                res = -EBUSY;
        else
@@ -215,19 +217,26 @@ int get_filesystem_list(char * buf)
 struct file_system_type *get_fs_type(const char *name)
 {
        struct file_system_type *fs;
+       const char *dot = strchr(name, '.');
+       unsigned len = dot ? dot - name : strlen(name);
 
        read_lock(&file_systems_lock);
-       fs = *(find_filesystem(name));
+       fs = *(find_filesystem(name, len));
        if (fs && !try_module_get(fs->owner))
                fs = NULL;
        read_unlock(&file_systems_lock);
-       if (!fs && (request_module("%s", name) == 0)) {
+       if (!fs && (request_module("%.*s", len, name) == 0)) {
                read_lock(&file_systems_lock);
-               fs = *(find_filesystem(name));
+               fs = *(find_filesystem(name, len));
                if (fs && !try_module_get(fs->owner))
                        fs = NULL;
                read_unlock(&file_systems_lock);
        }
+
+       if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
+               put_filesystem(fs);
+               fs = NULL;
+       }
        return fs;
 }
 

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index d8003be56e0593e392d51c55539c86939ab5f4c9..1397018ff47665e28bead1fb5a75592703c762c9 100644 (file)
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -636,6 +636,7 @@ static int fuse_get_sb(struct file_system_type *fs_type,
 static struct file_system_type fuse_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "fuse",
+       .fs_flags       = FS_HAS_SUBTYPE,
        .get_sb         = fuse_get_sb,
        .kill_sb        = kill_anon_super,
 };
@@ -652,6 +653,7 @@ static int fuse_get_sb_blk(struct file_system_type *fs_type,
 static struct file_system_type fuseblk_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "fuseblk",
+       .fs_flags       = FS_HAS_SUBTYPE,
        .get_sb         = fuse_get_sb_blk,
        .kill_sb        = kill_block_super,
        .fs_flags       = FS_REQUIRES_DEV,

diff --git a/fs/namespace.c b/fs/namespace.c
index be5e56bfb73e18b1d65612ebce3ca46a10adb7c9..c5b88100d914d8ae618261cb38cf2af652849340 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -377,6 +377,10 @@ static int show_vfsmnt(struct seq_file *m, void *v)
        seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
        seq_putc(m, ' ');
        mangle(m, mnt->mnt_sb->s_type->name);
+       if (mnt->mnt_sb->s_subtype && mnt->mnt_sb->s_subtype[0]) {
+               seq_putc(m, '.');
+               mangle(m, mnt->mnt_sb->s_subtype);
+       }
        seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw");
        for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
                if (mnt->mnt_sb->s_flags & fs_infop->flag)

diff --git a/fs/super.c b/fs/super.c
index 8341e4e1d7380f49ce590a428456b12c88e11fed..5260d620c555fbd987eed1642649c0372670ace9 100644 (file)
--- a/fs/super.c
+++ b/fs/super.c
@@ -107,6 +107,7 @@ out:
 static inline void destroy_super(struct super_block *s)
 {
        security_sb_free(s);
+       kfree(s->s_subtype);
        kfree(s);
 }
 
@@ -907,6 +908,29 @@ out:
 
 EXPORT_SYMBOL_GPL(vfs_kern_mount);
 
+static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
+{
+       int err;
+       const char *subtype = strchr(fstype, '.');
+       if (subtype) {
+               subtype++;
+               err = -EINVAL;
+               if (!subtype[0])
+                       goto err;
+       } else
+               subtype = "";
+
+       mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
+       err = -ENOMEM;
+       if (!mnt->mnt_sb->s_subtype)
+               goto err;
+       return mnt;
+
+ err:
+       mntput(mnt);
+       return ERR_PTR(err);
+}
+
 struct vfsmount *
 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 {
@@ -915,6 +939,9 @@ do_kern_mount(const char *fstype, int flags, const char *name, void *data)
        if (!type)
                return ERR_PTR(-ENODEV);
        mnt = vfs_kern_mount(type, flags, name, data);
+       if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
+           !mnt->mnt_sb->s_subtype)
+               mnt = fs_set_subtype(mnt, fstype);
        put_filesystem(type);
        return mnt;
 }

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 986b5d5d369fe59da11f005578f698767110013f..527a09a82297887db5512f10b016e2f2f32c7906 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -92,6 +92,7 @@ extern int dir_notify_enable;
 /* public flags for file_system_type */
 #define FS_REQUIRES_DEV 1 
 #define FS_BINARY_MOUNTDATA 2
+#define FS_HAS_SUBTYPE 4
 #define FS_REVAL_DOT   16384   /* Check the paths ".", ".." for staleness */
 #define FS_RENAME_DOES_D_MOVE  32768   /* FS will handle d_move()
                                         * during rename() internally.
@@ -961,6 +962,12 @@ struct super_block {
        /* Granularity of c/m/atime in ns.
           Cannot be worse than a second */
        u32                s_time_gran;
+
+       /*
+        * Filesystem subtype.  If non-empty the filesystem type field
+        * in /proc/mounts will be "type.subtype"
+        */
+       char *s_subtype;
 };
 
 extern struct timespec current_fs_time(struct super_block *sb);