linux-kernel - [PATCH 1/3] cleanup: add conditional guard helper

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Message-Id: <20241001-cleanup-if_not_cond_guard-v1-1-7753810b0f7a@baylibre.com>
Date: Tue, 01 Oct 2024 17:30:18 -0500
From: David Lechner <dlechner@...libre.com>
To: Peter Zijlstra <peterz@...radead.org>, 
 Dan Williams <dan.j.williams@...el.com>, 
 Linus Torvalds <torvalds@...ux-foundation.org>, 
 Jonathan Cameron <jic23@...nel.org>
Cc: Nuno Sá <nuno.sa@...log.com>, 
 Michael Hennerich <michael.hennerich@...log.com>, 
 linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org, 
 linux-cxl@...r.kernel.org, David Lechner <dlechner@...libre.com>
Subject: [PATCH 1/3] cleanup: add conditional guard helper

Add a new if_not_cond_guard() macro to cleanup.h for handling
conditional guards such as mutext_trylock().

This is more ergonomic than scoped_cond_guard() for most use cases.
Instead of hiding the error handling statement in the macro args, it
works like a normal if statement and allow the error path to be indented
while the normal code flow path is not indented. And it avoid unwanted
side-effect from hidden for loop in scoped_cond_guard().

Signed-off-by: David Lechner <dlechner@...libre.com>
---
 include/linux/cleanup.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index 038b2d523bf8..682bb3fadfc9 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -273,6 +273,10 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
  *	an anonymous instance of the (guard) class, not recommended for
  *	conditional locks.
  *
+ * if_not_cond_guard(name, args...) { <error handling> }:
+ *	convenience macro for conditional guards that calls the statement that
+ *	follows only if the lock was not acquired (typically an error return).
+ *
  * scoped_guard (name, args...) { }:
  *	similar to CLASS(name, scope)(args), except the variable (with the
  *	explicit name 'scope') is declard in a for-loop such that its scope is
@@ -304,6 +308,13 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
 
 #define __guard_ptr(_name) class_##_name##_lock_ptr
 
+#define __if_not_cond_guard(_name, _id, args...)	\
+	CLASS(_name, _id)(args);			\
+	if (!__guard_ptr(_name)(&_id))
+
+#define if_not_cond_guard(_name, args...) \
+	__if_not_cond_guard(_name, __UNIQUE_ID(guard), args)
+
 #define scoped_guard(_name, args...)					\
 	for (CLASS(_name, scope)(args),					\
 	     *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)

-- 
2.43.0