vfs: add RENAME_WHITEOUT

This adds a new RENAME_WHITEOUT flag.  This flag makes rename() create a
whiteout of source.  The whiteout creation is atomic relative to the
rename.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

2 files changed, 7 insertions, 2 deletions

diff --git a/fs/namei.c b/fs/namei.c
index d20191c0ebf5..42df664e95e5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4209,12 +4209,16 @@ SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
         bool should_retry = false;
         int error;
 
-        if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
+        if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
                 return -EINVAL;
 
-        if ((flags & RENAME_NOREPLACE) && (flags & RENAME_EXCHANGE))
+        if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
+            (flags & RENAME_EXCHANGE))
                 return -EINVAL;
 
+        if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
+                return -EPERM;
+
 retry:
         from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
         if (IS_ERR(from)) {
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index ca1a11bb4443..3735fa0a6784 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -37,6 +37,7 @@
 
 #define RENAME_NOREPLACE        (1 << 0)        /* Don't overwrite target */
 #define RENAME_EXCHANGE         (1 << 1)        /* Exchange source and dest */
+#define RENAME_WHITEOUT         (1 << 2)        /* Whiteout source */
 
 struct fstrim_range {
         __u64 start;