From: Miklos Szeredi This patch fixes a problem when a inode which is the root of a mount becomes bad (make_bad_inode()). In this case follow_link will return -EIO, so the name resolution fails, and umount won't work. The solution is just to remove the follow_link method from bad_inode_ops. Any filesystem operation (other than unmount) will still fail, since every other method returns -EIO. A test case for this is: 1) export an smbfs on host A and mount the share on host B 2) create directory X on A under the exported directory 3) bind mount X to Y on B (Y need not be under the share) 4) remove directory X, and create regular file X (same name) on A 5) stat X on B, this will make X a bad inode (file type changed) 6) umount Y Without the patch applied, umount won't succeed, and a reboot is necessary to get rid of the mount. With the patch applied, umount will succeed. The same is true for any filesystem which uses make_bad_inode() to mark an existing inode bad (NFS, SMBFS, FUSE, etc...). Signed-off-by: Miklos Szeredi Signed-off-by: Andrew Morton --- 25-akpm/fs/bad_inode.c | 14 ++------------ 1 files changed, 2 insertions(+), 12 deletions(-) diff -puN fs/bad_inode.c~cant-unmount-bad-inode fs/bad_inode.c --- 25/fs/bad_inode.c~cant-unmount-bad-inode Mon Jan 24 14:06:32 2005 +++ 25-akpm/fs/bad_inode.c Mon Jan 24 14:06:32 2005 @@ -15,17 +15,6 @@ #include #include -/* - * The follow_link operation is special: it must behave as a no-op - * so that a bad root inode can at least be unmounted. To do this - * we must dput() the base and return the dentry with a dget(). - */ -static int bad_follow_link(struct dentry *dent, struct nameidata *nd) -{ - nd_set_link(nd, ERR_PTR(-EIO)); - return 0; -} - static int return_EIO(void) { return -EIO; @@ -70,7 +59,8 @@ struct inode_operations bad_inode_ops = .mknod = EIO_ERROR, .rename = EIO_ERROR, .readlink = EIO_ERROR, - .follow_link = bad_follow_link, + /* follow_link must be no-op, otherwise unmounting this inode + won't work */ .truncate = EIO_ERROR, .permission = EIO_ERROR, .getattr = EIO_ERROR, _