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Commit 76fca90e authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

vfs: default to generic_readlink() 



If i_op->readlink is NULL, but i_op->get_link is set then vfs_readlink()
defaults to calling generic_readlink().

The IOP_DEFAULT_READLINK flag indicates that the above conditions are met
and the default action can be taken.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent fd4a0edf

Documentation/filesystems/porting

+4 −0
Original line number Diff line number Diff line
@@ -596,3 +596,7 @@ in your dentry operations instead. 
[mandatory]

	->rename() has an added flags argument.  Any flags not handled by the

        filesystem should result in EINVAL being returned.

--

[recommended]

	->readlink is optional for symlinks.  Don't set, unless filesystem needs

	to fake something for readlink(2).

Documentation/filesystems/vfs.txt

+6 −3
Original line number Diff line number Diff line
@@ -451,9 +451,6 @@ otherwise noted. 
	exist; this is checked by the VFS.  Unlike plain rename,

	source and target may be of different type.



  readlink: called by the readlink(2) system call. Only required if

	you want to support reading symbolic links



  get_link: called by the VFS to follow a symbolic link to the

	inode it points to.  Only required if you want to support

	symbolic links.  This method returns the symlink body
@@ -468,6 +465,12 @@ otherwise noted. 
	argument.  If request can't be handled without leaving RCU mode,

	have it return ERR_PTR(-ECHILD).



  readlink: this is now just an override for use by readlink(2) for the

	cases when ->get_link uses nd_jump_link() or object is not in

	fact a symlink.  Normally filesystems should only implement

	->get_link for symlinks and readlink(2) will automatically use

	that.



  permission: called by the VFS to check for access rights on a POSIX-like

  	filesystem.

fs/namei.c

+12 −3
Original line number Diff line number Diff line
@@ -4682,10 +4682,19 @@ int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen) 
{

	struct inode *inode = d_inode(dentry);



	if (!inode->i_op->readlink)

	if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {

		if (unlikely(inode->i_op->readlink))

			return inode->i_op->readlink(dentry, buffer, buflen);



		if (!d_is_symlink(dentry))

			return -EINVAL;



	return inode->i_op->readlink(dentry, buffer, buflen);

		spin_lock(&inode->i_lock);

		inode->i_opflags |= IOP_DEFAULT_READLINK;

		spin_unlock(&inode->i_lock);

	}



	return generic_readlink(dentry, buffer, buflen);

}

EXPORT_SYMBOL(vfs_readlink);

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -595,6 +595,7 @@ is_uncached_acl(struct posix_acl *acl) 
#define IOP_LOOKUP	0x0002

#define IOP_NOFOLLOW	0x0004

#define IOP_XATTR	0x0008

#define IOP_DEFAULT_READLINK	0x0010



/*

 * Keep mostly read-only and often accessed (especially for