fuse: extract fuse_fill_super_common()

fuse_fill_super() includes code to process the fd= option and link the
struct fuse_dev to the fd's struct file.  In virtio-fs there is no file
descriptor because /dev/fuse is not used.

This patch extracts fuse_fill_super_common() so that both classic fuse and
virtio-fs can share the code to initialize a mount.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

2 files changed, 80 insertions, 59 deletions

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 5f910c99e8dd..1902148281cc 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -416,6 +416,26 @@ struct fuse_dev {
         struct list_head entry;
 };
 
+struct fuse_fs_context {
+        int fd;
+        unsigned int rootmode;
+        kuid_t user_id;
+        kgid_t group_id;
+        bool is_bdev:1;
+        bool fd_present:1;
+        bool rootmode_present:1;
+        bool user_id_present:1;
+        bool group_id_present:1;
+        bool default_permissions:1;
+        bool allow_other:1;
+        unsigned int max_read;
+        unsigned int blksize;
+        const char *subtype;
+
+        /* fuse_dev pointer to fill in, should contain NULL on entry */
+        void **fudptr;
+};
+
 /**
  * A Fuse connection.
  *
@@ -874,6 +894,13 @@ void fuse_dev_free(struct fuse_dev *fud);
 void fuse_send_init(struct fuse_conn *fc);
 
 /**
+ * Fill in superblock and initialize fuse connection
+ * @sb: partially-initialized superblock to fill in
+ * @ctx: mount context
+ */
+int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx);
+
+/**
  * Add connection to control filesystem
  */
 int fuse_ctl_add_conn(struct fuse_conn *fc);
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 5d455f4d6195..30d92e633ece 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -64,23 +64,6 @@ MODULE_PARM_DESC(max_user_congthresh,
 static struct file_system_type fuseblk_fs_type;
 #endif
 
-struct fuse_fs_context {
-        const char      *subtype;
-        bool            is_bdev;
-        int fd;
-        unsigned rootmode;
-        kuid_t user_id;
-        kgid_t group_id;
-        unsigned fd_present:1;
-        unsigned rootmode_present:1;
-        unsigned user_id_present:1;
-        unsigned group_id_present:1;
-        unsigned default_permissions:1;
-        unsigned allow_other:1;
-        unsigned max_read;
-        unsigned blksize;
-};
-
 struct fuse_forget_link *fuse_alloc_forget(void)
 {
         return kzalloc(sizeof(struct fuse_forget_link), GFP_KERNEL);
@@ -1100,16 +1083,13 @@ void fuse_dev_free(struct fuse_dev *fud)
 }
 EXPORT_SYMBOL_GPL(fuse_dev_free);
 
-static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
+int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
 {
-        struct fuse_fs_context *ctx = fsc->fs_private;
         struct fuse_dev *fud;
-        struct fuse_conn *fc;
+        struct fuse_conn *fc = get_fuse_conn_super(sb);
         struct inode *root;
-        struct file *file;
         struct dentry *root_dentry;
         int err;
-        int is_bdev = sb->s_bdev != NULL;
 
         err = -EINVAL;
         if (sb->s_flags & SB_MANDLOCK)
@@ -1117,7 +1097,7 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
 
         sb->s_flags &= ~(SB_NOSEC | SB_I_VERSION);
 
-        if (is_bdev) {
+        if (ctx->is_bdev) {
 #ifdef CONFIG_BLOCK
                 err = -EINVAL;
                 if (!sb_set_blocksize(sb, ctx->blksize))
@@ -1140,19 +1120,6 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
         if (sb->s_user_ns != &init_user_ns)
                 sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER;
 
-        file = fget(ctx->fd);
-        err = -EINVAL;
-        if (!file)
-                goto err;
-
-        /*
-         * Require mount to happen from the same user namespace which
-         * opened /dev/fuse to prevent potential attacks.
-         */
-        if (file->f_op != &fuse_dev_operations ||
-            file->f_cred->user_ns != sb->s_user_ns)
-                goto err_fput;
-
         /*
          * If we are not in the initial user namespace posix
          * acls must be translated.
@@ -1160,17 +1127,9 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
         if (sb->s_user_ns != &init_user_ns)
                 sb->s_xattr = fuse_no_acl_xattr_handlers;
 
-        fc = kmalloc(sizeof(*fc), GFP_KERNEL);
-        err = -ENOMEM;
-        if (!fc)
-                goto err_fput;
-
-        fuse_conn_init(fc, sb->s_user_ns);
-        fc->release = fuse_free_conn;
-
         fud = fuse_dev_alloc(fc);
         if (!fud)
-                goto err_put_conn;
+                goto err;
 
         fc->dev = sb->s_dev;
         fc->sb = sb;
@@ -1188,10 +1147,7 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
         fc->user_id = ctx->user_id;
         fc->group_id = ctx->group_id;
         fc->max_read = max_t(unsigned, 4096, ctx->max_read);
-        fc->destroy = is_bdev;
-
-        /* Used by get_root_inode() */
-        sb->s_fs_info = fc;
+        fc->destroy = ctx->is_bdev;
 
         err = -ENOMEM;
         root = fuse_get_root_inode(sb, ctx->rootmode);
@@ -1204,7 +1160,7 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
 
         mutex_lock(&fuse_mutex);
         err = -EINVAL;
-        if (file->private_data)
+        if (*ctx->fudptr)
                 goto err_unlock;
 
         err = fuse_ctl_add_conn(fc);
@@ -1213,24 +1169,62 @@ static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
 
         list_add_tail(&fc->entry, &fuse_conn_list);
         sb->s_root = root_dentry;
-        file->private_data = fud;
+        *ctx->fudptr = fud;
         mutex_unlock(&fuse_mutex);
+        return 0;
+
+ err_unlock:
+        mutex_unlock(&fuse_mutex);
+        dput(root_dentry);
+ err_dev_free:
+        fuse_dev_free(fud);
+ err:
+        return err;
+}
+EXPORT_SYMBOL_GPL(fuse_fill_super_common);
+
+static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
+{
+        struct fuse_fs_context *ctx = fsc->fs_private;
+        struct file *file;
+        int err;
+        struct fuse_conn *fc;
+
+        err = -EINVAL;
+        file = fget(ctx->fd);
+        if (!file)
+                goto err;
+
+        /*
+         * Require mount to happen from the same user namespace which
+         * opened /dev/fuse to prevent potential attacks.
+         */
+        if ((file->f_op != &fuse_dev_operations) ||
+            (file->f_cred->user_ns != sb->s_user_ns))
+                goto err_fput;
+        ctx->fudptr = &file->private_data;
+
+        fc = kmalloc(sizeof(*fc), GFP_KERNEL);
+        err = -ENOMEM;
+        if (!fc)
+                goto err_fput;
+
+        fuse_conn_init(fc, sb->s_user_ns);
+        fc->release = fuse_free_conn;
+        sb->s_fs_info = fc;
+
+        err = fuse_fill_super_common(sb, ctx);
+        if (err)
+                goto err_put_conn;
         /*
          * atomic_dec_and_test() in fput() provides the necessary
          * memory barrier for file->private_data to be visible on all
          * CPUs after this
          */
         fput(file);
-
-        fuse_send_init(fc);
-
+        fuse_send_init(get_fuse_conn_super(sb));
         return 0;
 
- err_unlock:
-        mutex_unlock(&fuse_mutex);
-        dput(root_dentry);
- err_dev_free:
-        fuse_dev_free(fud);
  err_put_conn:
         fuse_conn_put(fc);
         sb->s_fs_info = NULL;