diff options
| author | Miklos Szeredi <mszeredi@redhat.com> | 2016-12-09 16:45:04 +0100 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2016-12-09 16:45:04 +0100 |
| commit | 76fca90e9f3abc82114d9d02d8e14e0324a18ca2 (patch) | |
| tree | 9dc26cb4603b4c93cd6b5b1bb7b538c30d19e438 | |
| parent | fd4a0edf2a3d781c6ae07d2810776ce22302ee1c (diff) | |
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>
| -rw-r--r-- | Documentation/filesystems/porting | 4 | ||||
| -rw-r--r-- | Documentation/filesystems/vfs.txt | 9 | ||||
| -rw-r--r-- | fs/namei.c | 15 | ||||
| -rw-r--r-- | include/linux/fs.h | 1 |
4 files changed, 23 insertions, 6 deletions
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting index bdd025ceb763..95280079c0b3 100644 --- a/Documentation/filesystems/porting +++ b/Documentation/filesystems/porting @@ -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). diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index b5039a00caaf..038241123ca5 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -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. diff --git a/fs/namei.c b/fs/namei.c index 12a4159de72a..b87465d67c60 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -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); + + if (!d_is_symlink(dentry)) + return -EINVAL; + + spin_lock(&inode->i_lock); + inode->i_opflags |= IOP_DEFAULT_READLINK; + spin_unlock(&inode->i_lock); + } - return inode->i_op->readlink(dentry, buffer, buflen); + return generic_readlink(dentry, buffer, buflen); } EXPORT_SYMBOL(vfs_readlink); diff --git a/include/linux/fs.h b/include/linux/fs.h index eba20d1c068d..f6c206eae6ac 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -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 |