[PATCH v2 12/14] namei: clean up do_linkat retry logic

[Dmitry Kadashev <dkadashev@xxxxxxxxx>]

No functional changes, just move the main logic to a helper function to
make the whole thing easier to follow.

Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christian Brauner <christian.brauner@xxxxxxxxxx>
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/io-uring/CAHk-=wiG+sN+2zSoAOggKCGue2kOJvw3rQySvQXsZstRQFTN+g@xxxxxxxxxxxxxx/
Link: https://lore.kernel.org/io-uring/CAHk-=wiE_JVny73KRZ6wuhL_5U0RRSmAw678_Cnkh3OHM8C7Jg@xxxxxxxxxxxxxx/
Signed-off-by: Dmitry Kadashev <dkadashev@xxxxxxxxx>
---
 fs/namei.c | 37 +++++++++++++++++++------------------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 82cb6421b6df..b93e9623eb5d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4381,37 +4381,32 @@ EXPORT_SYMBOL(vfs_link);
  * with linux 2.0, and to avoid hard-linking to directories
  * and other special files.  --ADM
  */
-int do_linkat(int olddfd, struct filename *old, int newdfd,
-	      struct filename *new, int flags)
+static int try_linkat(int olddfd, struct filename *old, int newdfd,
+		      struct filename *new, int flags, unsigned int how)
 {
 	struct user_namespace *mnt_userns;
 	struct dentry *new_dentry;
 	struct path old_path, new_path;
 	struct inode *delegated_inode = NULL;
-	int how = 0;
 	int error;
 
 retry:
-	if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) {
-		error = -EINVAL;
-		goto out_putnames;
-	}
+	if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
+		return -EINVAL;
 	/*
 	 * To use null names we require CAP_DAC_READ_SEARCH
 	 * This ensures that not everyone will be able to create
 	 * handlink using the passed filedescriptor.
 	 */
-	if (flags & AT_EMPTY_PATH && !capable(CAP_DAC_READ_SEARCH)) {
-		error = -ENOENT;
-		goto out_putnames;
-	}
+	if (flags & AT_EMPTY_PATH && !capable(CAP_DAC_READ_SEARCH))
+		return -ENOENT;
 
 	if (flags & AT_SYMLINK_FOLLOW)
 		how |= LOOKUP_FOLLOW;
 
 	error = __filename_lookup(olddfd, old, how, &old_path, NULL);
 	if (error)
-		goto out_putnames;
+		return error;
 
 	new_dentry = __filename_create(newdfd, new, &new_path,
 					(how & LOOKUP_REVAL));
@@ -4442,14 +4437,20 @@ int do_linkat(int olddfd, struct filename *old, int newdfd,
 	}
 out_putpath:
 	path_put(&old_path);
-out_putnames:
-	if (unlikely(retry_estale(error, how))) {
-		how |= LOOKUP_REVAL;
-		goto retry;
-	}
+	return error;
+}
+
+int do_linkat(int olddfd, struct filename *old, int newdfd,
+	      struct filename *new, int flags)
+{
+	int error;
+
+	error = try_linkat(olddfd, old, newdfd, new, flags, 0);
+	if (unlikely(retry_estale(error, 0)))
+		error = try_linkat(olddfd, old, newdfd, new, flags, LOOKUP_REVAL);
+
 	putname(old);
 	putname(new);
-
 	return error;
 }
 
-- 
2.30.2