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authorMiklos Szeredi <mszeredi@suse.cz>2014-10-24 02:14:36 +0400
committerMiklos Szeredi <mszeredi@suse.cz>2014-10-24 02:14:36 +0400
commit787fb6bc9682ec7c05fb5d9561b57100fbc1cc41 (patch)
treefde11fbe9f87e95ef6078fcbfed5f55c9ba134f8 /fs
parentcbdf35bcb833bfd00f0925d7a9a33a21f41ea582 (diff)
downloadlinux-787fb6bc9682ec7c05fb5d9561b57100fbc1cc41.tar.xz
vfs: add whiteout support
Whiteout isn't actually a new file type, but is represented as a char device (Linus's idea) with 0/0 device number. This has several advantages compared to introducing a new whiteout file type: - no userspace API changes (e.g. trivial to make backups of upper layer filesystem, without losing whiteouts) - no fs image format changes (you can boot an old kernel/fsck without whiteout support and things won't break) - implementation is trivial Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Diffstat (limited to 'fs')
-rw-r--r--fs/namei.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 77fd536106cb..d20191c0ebf5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4346,6 +4346,20 @@ SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newna
return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
}
+int vfs_whiteout(struct inode *dir, struct dentry *dentry)
+{
+ int error = may_create(dir, dentry);
+ if (error)
+ return error;
+
+ if (!dir->i_op->mknod)
+ return -EPERM;
+
+ return dir->i_op->mknod(dir, dentry,
+ S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
+}
+EXPORT_SYMBOL(vfs_whiteout);
+
int readlink_copy(char __user *buffer, int buflen, const char *link)
{
int len = PTR_ERR(link);