[RFC PATCH 1/8] non-consuming variant of do_renameat2()

[Al Viro <viro@zeniv.linux.org.uk>]

filename_renameat2() replaces do_renameat2(); unlike the latter,
it does not drop filename references - these days it can be just
as easily arranged in the caller.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 Documentation/filesystems/porting.rst |  8 ++++++++
 fs/internal.h                         |  2 +-
 fs/namei.c                            | 21 +++++++++++----------
 io_uring/fs.c                         |  7 ++++---
 4 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 3397937ed838..577f7f952a51 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1334,3 +1334,11 @@ end_creating() and the parent will be unlocked precisely when necessary.
 
 kill_litter_super() is gone; convert to DCACHE_PERSISTENT use (as all
 in-tree filesystems have done).
+
+---
+
+**mandatory**
+
+do_renameat2() is gone; filename_renameat2() replaces it.  The difference
+is that the former used to consume filename references; the latter does
+not.
diff --git a/fs/internal.h b/fs/internal.h
index 4c4d2733c47a..5047cfbb8c93 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -57,7 +57,7 @@ extern int filename_lookup(int dfd, struct filename *name, unsigned flags,
 int do_rmdir(int dfd, struct filename *name);
 int do_unlinkat(int dfd, struct filename *name);
 int may_linkat(struct mnt_idmap *idmap, const struct path *link);
-int do_renameat2(int olddfd, struct filename *oldname, int newdfd,
+int filename_renameat2(int olddfd, struct filename *oldname, int newdfd,
 		 struct filename *newname, unsigned int flags);
 int do_mkdirat(int dfd, struct filename *name, umode_t mode);
 int do_mknodat(int dfd, struct filename *name, umode_t mode, unsigned int dev);
diff --git a/fs/namei.c b/fs/namei.c
index 7418a4e725da..c54beaf193e0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -5980,11 +5980,9 @@ int vfs_rename(struct renamedata *rd)
 }
 EXPORT_SYMBOL(vfs_rename);
 
-int do_renameat2(int olddfd, struct filename *__from, int newdfd,
-		 struct filename *__to, unsigned int flags)
+int filename_renameat2(int olddfd, struct filename *from,
+		       int newdfd, struct filename *to, unsigned int flags)
 {
-	CLASS(filename_consume, from)(__from);
-	CLASS(filename_consume, to)(__to);
 	struct renamedata rd;
 	struct path old_path, new_path;
 	struct qstr old_last, new_last;
@@ -6088,21 +6086,24 @@ int do_renameat2(int olddfd, struct filename *__from, int newdfd,
 SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
 		int, newdfd, const char __user *, newname, unsigned int, flags)
 {
-	return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
-				flags);
+	CLASS(filename, old)(oldname);
+	CLASS(filename, new)(newname);
+	return filename_renameat2(olddfd, old, newdfd, new, flags);
 }
 
 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
 		int, newdfd, const char __user *, newname)
 {
-	return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
-				0);
+	CLASS(filename, old)(oldname);
+	CLASS(filename, new)(newname);
+	return filename_renameat2(olddfd, old, newdfd, new, 0);
 }
 
 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
 {
-	return do_renameat2(AT_FDCWD, getname(oldname), AT_FDCWD,
-				getname(newname), 0);
+	CLASS(filename, old)(oldname);
+	CLASS(filename, new)(newname);
+	return filename_renameat2(AT_FDCWD, old, AT_FDCWD, new, 0);
 }
 
 int readlink_copy(char __user *buffer, int buflen, const char *link, int linklen)
diff --git a/io_uring/fs.c b/io_uring/fs.c
index c04c6282210a..e5829d112c9e 100644
--- a/io_uring/fs.c
+++ b/io_uring/fs.c
@@ -82,13 +82,14 @@ int io_renameat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 int io_renameat(struct io_kiocb *req, unsigned int issue_flags)
 {
 	struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename);
+	CLASS(filename_complete_delayed, old)(&ren->oldpath);
+	CLASS(filename_complete_delayed, new)(&ren->newpath);
 	int ret;
 
 	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
 
-	ret = do_renameat2(ren->old_dfd, complete_getname(&ren->oldpath),
-			   ren->new_dfd, complete_getname(&ren->newpath),
-			   ren->flags);
+	ret = filename_renameat2(ren->old_dfd, old,
+				 ren->new_dfd, new, ren->flags);
 
 	req->flags &= ~REQ_F_NEED_CLEANUP;
 	io_req_set_res(req, ret, 0);
-- 
2.47.3