fuse: Allow fuse_fill_super_common() for submounts

Submounts have their own superblock, which needs to be initialized.
However, they do not have a fuse_fs_context associated with them, and
the root node's attributes should be taken from the mountpoint's node.

Extend fuse_fill_super_common() to work for submounts by making the @ctx
parameter optional, and by adding a @submount_finode parameter.

(There is a plain "unsigned" in an existing code block that is being
indented by this commit.  Extend it to "unsigned int" so checkpatch does
not complain.)

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 95b81a8..d469905 100644 (file)
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1044,6 +1044,14 @@ void fuse_send_init(struct fuse_mount *fm);
  */
 int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx);
 
+/*
+ * Fill in superblock for submounts
+ * @sb: partially-initialized superblock to fill in
+ * @parent_fi: The fuse_inode of the parent filesystem where this submount is
+ *            mounted
+ */
+int fuse_fill_super_submount(struct super_block *sb,
+                            struct fuse_inode *parent_fi);
 
 /*
  * Remove the mount from the connection

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 8b34997..da5f03f 100644 (file)
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -126,8 +126,11 @@ static void fuse_evict_inode(struct inode *inode)
 
                if (FUSE_IS_DAX(inode))
                        fuse_dax_inode_cleanup(inode);
-               fuse_queue_forget(fc, fi->forget, fi->nodeid, fi->nlookup);
-               fi->forget = NULL;
+               if (fi->nlookup) {
+                       fuse_queue_forget(fc, fi->forget, fi->nodeid,
+                                         fi->nlookup);
+                       fi->forget = NULL;
+               }
        }
        if (S_ISREG(inode->i_mode) && !is_bad_inode(inode)) {
                WARN_ON(!list_empty(&fi->write_files));
@@ -1207,6 +1210,87 @@ void fuse_dev_free(struct fuse_dev *fud)
 }
 EXPORT_SYMBOL_GPL(fuse_dev_free);
 
+static void fuse_fill_attr_from_inode(struct fuse_attr *attr,
+                                     const struct fuse_inode *fi)
+{
+       *attr = (struct fuse_attr){
+               .ino            = fi->inode.i_ino,
+               .size           = fi->inode.i_size,
+               .blocks         = fi->inode.i_blocks,
+               .atime          = fi->inode.i_atime.tv_sec,
+               .mtime          = fi->inode.i_mtime.tv_sec,
+               .ctime          = fi->inode.i_ctime.tv_sec,
+               .atimensec      = fi->inode.i_atime.tv_nsec,
+               .mtimensec      = fi->inode.i_mtime.tv_nsec,
+               .ctimensec      = fi->inode.i_ctime.tv_nsec,
+               .mode           = fi->inode.i_mode,
+               .nlink          = fi->inode.i_nlink,
+               .uid            = fi->inode.i_uid.val,
+               .gid            = fi->inode.i_gid.val,
+               .rdev           = fi->inode.i_rdev,
+               .blksize        = 1u << fi->inode.i_blkbits,
+       };
+}
+
+static void fuse_sb_defaults(struct super_block *sb)
+{
+       sb->s_magic = FUSE_SUPER_MAGIC;
+       sb->s_op = &fuse_super_operations;
+       sb->s_xattr = fuse_xattr_handlers;
+       sb->s_maxbytes = MAX_LFS_FILESIZE;
+       sb->s_time_gran = 1;
+       sb->s_export_op = &fuse_export_operations;
+       sb->s_iflags |= SB_I_IMA_UNVERIFIABLE_SIGNATURE;
+       if (sb->s_user_ns != &init_user_ns)
+               sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER;
+       sb->s_flags &= ~(SB_NOSEC | SB_I_VERSION);
+
+       /*
+        * If we are not in the initial user namespace posix
+        * acls must be translated.
+        */
+       if (sb->s_user_ns != &init_user_ns)
+               sb->s_xattr = fuse_no_acl_xattr_handlers;
+}
+
+int fuse_fill_super_submount(struct super_block *sb,
+                            struct fuse_inode *parent_fi)
+{
+       struct fuse_mount *fm = get_fuse_mount_super(sb);
+       struct super_block *parent_sb = parent_fi->inode.i_sb;
+       struct fuse_attr root_attr;
+       struct inode *root;
+
+       fuse_sb_defaults(sb);
+       fm->sb = sb;
+
+       WARN_ON(sb->s_bdi != &noop_backing_dev_info);
+       sb->s_bdi = bdi_get(parent_sb->s_bdi);
+
+       sb->s_xattr = parent_sb->s_xattr;
+       sb->s_time_gran = parent_sb->s_time_gran;
+       sb->s_blocksize = parent_sb->s_blocksize;
+       sb->s_blocksize_bits = parent_sb->s_blocksize_bits;
+       sb->s_subtype = kstrdup(parent_sb->s_subtype, GFP_KERNEL);
+       if (parent_sb->s_subtype && !sb->s_subtype)
+               return -ENOMEM;
+
+       fuse_fill_attr_from_inode(&root_attr, parent_fi);
+       root = fuse_iget(sb, parent_fi->nodeid, 0, &root_attr, 0, 0);
+       /*
+        * This inode is just a duplicate, so it is not looked up and
+        * its nlookup should not be incremented.  fuse_iget() does
+        * that, though, so undo it here.
+        */
+       get_fuse_inode(root)->nlookup--;
+       sb->s_d_op = &fuse_dentry_operations;
+       sb->s_root = d_make_root(root);
+       if (!sb->s_root)
+               return -ENOMEM;
+
+       return 0;
+}
+
 int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
 {
        struct fuse_dev *fud = NULL;
@@ -1220,7 +1304,7 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
        if (sb->s_flags & SB_MANDLOCK)
                goto err;
 
-       sb->s_flags &= ~(SB_NOSEC | SB_I_VERSION);
+       fuse_sb_defaults(sb);
 
        if (ctx->is_bdev) {
 #ifdef CONFIG_BLOCK
@@ -1235,23 +1319,6 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
 
        sb->s_subtype = ctx->subtype;
        ctx->subtype = NULL;
-       sb->s_magic = FUSE_SUPER_MAGIC;
-       sb->s_op = &fuse_super_operations;
-       sb->s_xattr = fuse_xattr_handlers;
-       sb->s_maxbytes = MAX_LFS_FILESIZE;
-       sb->s_time_gran = 1;
-       sb->s_export_op = &fuse_export_operations;
-       sb->s_iflags |= SB_I_IMA_UNVERIFIABLE_SIGNATURE;
-       if (sb->s_user_ns != &init_user_ns)
-               sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER;
-
-       /*
-        * If we are not in the initial user namespace posix
-        * acls must be translated.
-        */
-       if (sb->s_user_ns != &init_user_ns)
-               sb->s_xattr = fuse_no_acl_xattr_handlers;
-
        if (IS_ENABLED(CONFIG_FUSE_DAX)) {
                err = fuse_dax_conn_alloc(fc, ctx->dax_dev);
                if (err)
@@ -1281,7 +1348,7 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
        fc->user_id = ctx->user_id;
        fc->group_id = ctx->group_id;
        fc->legacy_opts_show = ctx->legacy_opts_show;
-       fc->max_read = max_t(unsigned, 4096, ctx->max_read);
+       fc->max_read = max_t(unsigned int, 4096, ctx->max_read);
        fc->destroy = ctx->destroy;
        fc->no_control = ctx->no_control;
        fc->no_force_umount = ctx->no_force_umount;