[PATCH 13/14] namei: prepare do_renameat2 for refactoring

[Dmitry Kadashev <dkadashev@gmail.com>]

This is just a preparation for the move of the main renameat logic to a
separate function to make the logic easier to follow.  This change
contains the flow changes so that the actual change to move the main
logic to a separate function does no change the flow at all.

Changes to the flow here:

1. Flags handling is moved into the retry loop. So it can be moved
into the function with the main logic. A few extra arithmetic checks
on a slow path should be OK.

2. Just like the similar patches for rmdir and others a few commits
before, previously on filename_create() and filename_lookup() error the
function used to exit immediately, and now it will check the return code
to see if ESTALE retry is appropriate. Both filename_create() and
filename_lookup() do their own retries on ESTALE (at least via
filename_parentat() used inside), but this extra check should be
completely fine. Invalid flags will now hit `if retry_estale()` as well.

3. unlikely() is added around the ESTALE check;

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/io-uring/CAHk-=wiG+sN+2zSoAOggKCGue2kOJvw3rQySvQXsZstRQFTN+g@mail.gmail.com/
Link: https://lore.kernel.org/io-uring/CAHk-=wjFd0qn6asio=zg7zUTRmSty_TpAEhnwym1Qb=wFgCKzA@mail.gmail.com/
Signed-off-by: Dmitry Kadashev <dkadashev@gmail.com>
---
 fs/namei.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index b93e9623eb5d..a75abff5a9a6 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4654,9 +4654,9 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
 	int old_type, new_type;
 	struct inode *delegated_inode = NULL;
 	unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
-	bool should_retry = false;
 	int error = -EINVAL;
 
+retry:
 	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
 		goto put_names;
 
@@ -4667,7 +4667,6 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
 	if (flags & RENAME_EXCHANGE)
 		target_flags = 0;
 
-retry:
 	error = __filename_parentat(olddfd, from, lookup_flags, &old_path,
 					&old_last, &old_type);
 	if (error)
@@ -4769,17 +4768,14 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
 	}
 	mnt_drop_write(old_path.mnt);
 exit2:
-	if (retry_estale(error, lookup_flags))
-		should_retry = true;
 	path_put(&new_path);
 exit1:
 	path_put(&old_path);
-	if (should_retry) {
-		should_retry = false;
+put_names:
+	if (retry_estale(error, lookup_flags)) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
 	}
-put_names:
 	putname(from);
 	putname(to);
 	return error;
-- 
2.30.2