[PATCH v2 07/14] namei: prepare do_mknodat for refactoring

[Dmitry Kadashev <dkadashev@gmail.com>]

This is just a preparation for the move of the main mknodat 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.

There are 3 changes to the flow here:

1. may_mknod() call is repeated on ESTALE retry now. It's OK to do since
the call is very cheap (and ESTALE retry is a slow path) and the result
doesn't change;

2. Just like the similar patches for rmdir and others a few commits
before, previously on filename_create() error the function used to exit
immediately, and now it will check the return code to see if ESTALE
retry is appropriate. The filename_create() does its own retries on
ESTALE (at least via filename_parentat() used inside), but this extra
check should be completely fine.

3. The retry_estale() check is wrapped in unlikely(). Some other places
already have that and overall it seems to make sense

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-=wijsw1QSsQHFu_6dEoZEr_zvT7++WJWohcuEkLqqXBGrQ@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 | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 50ab1cd00983..4008867e516d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3754,10 +3754,10 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
 	int error;
 	unsigned int lookup_flags = 0;
 
+retry:
 	error = may_mknod(mode);
 	if (error)
 		goto out1;
-retry:
 	dentry = __filename_create(dfd, name, &path, lookup_flags);
 	error = PTR_ERR(dentry);
 	if (IS_ERR(dentry))
@@ -3788,11 +3788,11 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
 	}
 out2:
 	done_path_create(&path, dentry);
-	if (retry_estale(error, lookup_flags)) {
+out1:
+	if (unlikely(retry_estale(error, lookup_flags))) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
 	}
-out1:
 	putname(name);
 	return error;
 }
-- 
2.30.2