[PATCH 09/14] namei: prepare do_symlinkat for refactoring

[Dmitry Kadashev <dkadashev@gmail.com>]

This is just a preparation for the move of the main symlinkat 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. IS_ERR(from) check is repeated on ESTALE retry now. It's OK to do
since the call is trivial (and ESTALE retry is a slow path);

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-=wiG+sN+2zSoAOggKCGue2kOJvw3rQySvQXsZstRQFTN+g@mail.gmail.com/
Link: https://lore.kernel.org/io-uring/CAHk-=whH4msnFkj=iYZ9NDmZEAiZKM+vii803M8gnEwEsF1-Yg@mail.gmail.com/
Signed-off-by: Dmitry Kadashev <dkadashev@gmail.com>
---
 fs/namei.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index f7cde1543b47..c4d75c94adce 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4241,15 +4241,15 @@ int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
 	struct path path;
 	unsigned int lookup_flags = 0;
 
+retry:
 	if (IS_ERR(from)) {
 		error = PTR_ERR(from);
-		goto out_putnames;
+		goto out;
 	}
-retry:
 	dentry = __filename_create(newdfd, to, &path, lookup_flags);
 	error = PTR_ERR(dentry);
 	if (IS_ERR(dentry))
-		goto out_putnames;
+		goto out;
 
 	error = security_path_symlink(&path, dentry, from->name);
 	if (!error) {
@@ -4260,11 +4260,11 @@ int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
 				    from->name);
 	}
 	done_path_create(&path, dentry);
-	if (retry_estale(error, lookup_flags)) {
+out:
+	if (unlikely(retry_estale(error, lookup_flags))) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
 	}
-out_putnames:
 	putname(to);
 	putname(from);
 	return error;
-- 
2.30.2