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: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi 2016-12-09 16:45:04 +01:00
parent fd4a0edf2a
commit 76fca90e9f
4 changed files with 23 additions and 6 deletions

View File

@ -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).

View File

@ -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.

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@ -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)
return -EINVAL;
if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
if (unlikely(inode->i_op->readlink))
return inode->i_op->readlink(dentry, buffer, buflen);
return inode->i_op->readlink(dentry, buffer, buflen);
if (!d_is_symlink(dentry))
return -EINVAL;
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);

View File

@ -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