[PATCH 0/3 v5] Add cond_guard() to conditional guards

[PATCH 0/3 v5] Add cond_guard() to conditional guards

[Fabio M. De Francesco]

Add cond_guard() macro to conditional guards. Show how to use it by 
converting two functions in drivers/cxl to replace open-coded up_read()
in show_targetN() and in cxl_inject_poison() and avoid to 'goto' to a
cleanup block marked by an 'out' label. The second conversion is added
with v5 to show that the most recent implementation of cond_guard() can
also be used more than once in the same scope.

Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
---

Changes from RFC v5:
        Changed the interface of cond_guard() to take a statement or 
        statement-expression as its second argument to conform to Dan's 
        suggestion (thanks).
Changes from v1:
        Fixed a grammar error in the commit message of 1/2; replaced the
        name of the second argument of cond_guard() with '_fail'
        according to Jonathan's comments (thanks). 
Changes from v2:
        Changed macro's implementation to add an 'else' to protect
        against it being used incorrectly within another if() block.
        Suggested by Dan (thanks). The Reviewed-by tags on 1/2 are not
        forwarded because the implementation of cond_guard() has changed.
        Removed a redundant 'else' from show_targetN() in 2/2.
Changes from v3:
	Added braces around empty body in an 'else' statement in
	cond_guard(). Added Reviewed-by tags (Dave, Ira - thanks).
Changes from v4:
	Made it possible to call cond_guard() more than once in the same
	scope. Jonathan suggested a more elegant implementation than the
	one I had thought. It uses an exhisting helper instead of creating
	an ad hoc one (thanks). Added a second conversion to show that
	cond_guard() can be used twice in the same scope. Deleted the
	Reviewed-by tags from 1/3 since the implementation of cond_guard()
	has significantly been reworked to allow multiple calls.

Fabio M. De Francesco (3):
  cleanup: Add cond_guard() to conditional guards
  cxl/region: Use cond_guard() in show_targetN()
  cxl/memdev: Use cond_guard() in cxl_inject_poison()

 drivers/cxl/core/memdev.c | 19 +++++--------------
 drivers/cxl/core/region.c | 16 ++++------------
 include/linux/cleanup.h   | 20 ++++++++++++++++++++
 3 files changed, 29 insertions(+), 26 deletions(-)

-- 
2.43.2

[PATCH 1/3 v5] cleanup: Add cond_guard() to conditional guards

[Fabio M. De Francesco]

Add cond_guard() macro to conditional guards.

cond_guard() is a guard to be used with the conditional variants of locks,
like down_read_trylock() or mutex_lock_interruptible().

It takes a statement (or statement-expression) that is passed as its
second argument. That statement (or statement-expression) is executed if
waiting for a lock is interrupted or if a _trylock() fails in case of
contention.

Usage example:

	cond_guard(mutex_intr, return -EINTR, &mutex);

Consistent with other usage of _guard(), locks are unlocked at the exit of
the scope where cond_guard() is called. This macro can be called multiple
times in the same scope.

Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
---
 include/linux/cleanup.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index c2d09bc4f976..602afb85da34 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -134,6 +134,19 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
  *	an anonymous instance of the (guard) class, not recommended for
  *	conditional locks.
  *
+ * cond_guard(name, fail, args...):
+ *	a guard to be used with the conditional variants of locks, like
+ *	down_read_trylock() or mutex_lock_interruptible(). 'fail' is a
+ *	statement or statement-expression that is executed if waiting for a
+ *	lock is interrupted or if a _trylock() fails in case of contention.
+ *
+ *	Example:
+ *
+ *		cond_guard(mutex_intr, return -EINTR, &mutex);
+ *
+ * 	This macro can be called multiple times in the same scope, for it
+ * 	declares unique instances of type 'name'.
+ *
  * 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
@@ -165,6 +178,13 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
 
 #define __guard_ptr(_name) class_##_name##_lock_ptr
 
+#define __cond_guard(__unique, _name, _fail, args...) \
+	CLASS(_name, __unique)(args); \
+	if (!__guard_ptr(_name)(&__unique)) _fail; \
+	else { }
+#define cond_guard(_name, _fail, args...) \
+	__cond_guard(__UNIQUE_ID(scope), _name, _fail, args)
+
 #define scoped_guard(_name, args...)					\
 	for (CLASS(_name, scope)(args),					\
 	     *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)
-- 
2.43.2

Re: [PATCH 1/3 v5] cleanup: Add cond_guard() to conditional guards

[Jonathan Cameron]

On Sat, 17 Feb 2024 11:59:02 +0100
"Fabio M. De Francesco" <fabio.maria.de.francesco@linux.intel.com> wrote:

> Add cond_guard() macro to conditional guards.
> 
> cond_guard() is a guard to be used with the conditional variants of locks,
> like down_read_trylock() or mutex_lock_interruptible().
> 
> It takes a statement (or statement-expression) that is passed as its
> second argument. That statement (or statement-expression) is executed if
> waiting for a lock is interrupted or if a _trylock() fails in case of
> contention.
> 
> Usage example:
> 
> 	cond_guard(mutex_intr, return -EINTR, &mutex);
> 
> Consistent with other usage of _guard(), locks are unlocked at the exit of
> the scope where cond_guard() is called. This macro can be called multiple
> times in the same scope.
> 
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
Looks good.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Re: [PATCH 1/3 v5] cleanup: Add cond_guard() to conditional guards

[Dave Jiang]

On 2/17/24 3:59 AM, Fabio M. De Francesco wrote:
> Add cond_guard() macro to conditional guards.
> 
> cond_guard() is a guard to be used with the conditional variants of locks,
> like down_read_trylock() or mutex_lock_interruptible().
> 
> It takes a statement (or statement-expression) that is passed as its
> second argument. That statement (or statement-expression) is executed if
> waiting for a lock is interrupted or if a _trylock() fails in case of
> contention.
> 
> Usage example:
> 
> 	cond_guard(mutex_intr, return -EINTR, &mutex);
> 
> Consistent with other usage of _guard(), locks are unlocked at the exit of
> the scope where cond_guard() is called. This macro can be called multiple
> times in the same scope.
> 
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  include/linux/cleanup.h | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
> index c2d09bc4f976..602afb85da34 100644
> --- a/include/linux/cleanup.h
> +++ b/include/linux/cleanup.h
> @@ -134,6 +134,19 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
>   *	an anonymous instance of the (guard) class, not recommended for
>   *	conditional locks.
>   *
> + * cond_guard(name, fail, args...):
> + *	a guard to be used with the conditional variants of locks, like
> + *	down_read_trylock() or mutex_lock_interruptible(). 'fail' is a
> + *	statement or statement-expression that is executed if waiting for a
> + *	lock is interrupted or if a _trylock() fails in case of contention.
> + *
> + *	Example:
> + *
> + *		cond_guard(mutex_intr, return -EINTR, &mutex);
> + *
> + * 	This macro can be called multiple times in the same scope, for it
> + * 	declares unique instances of type 'name'.
> + *
>   * 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
> @@ -165,6 +178,13 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
>  
>  #define __guard_ptr(_name) class_##_name##_lock_ptr
>  
> +#define __cond_guard(__unique, _name, _fail, args...) \
> +	CLASS(_name, __unique)(args); \
> +	if (!__guard_ptr(_name)(&__unique)) _fail; \
> +	else { }
> +#define cond_guard(_name, _fail, args...) \
> +	__cond_guard(__UNIQUE_ID(scope), _name, _fail, args)
> +
>  #define scoped_guard(_name, args...)					\
>  	for (CLASS(_name, scope)(args),					\
>  	     *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)

[PATCH 2/3 v5] cxl/region: Use cond_guard() in show_targetN()

[Fabio M. De Francesco]

Use cond_guard() in show_target() to not open code an up_read() in an 'out'
block. If the down_read_interruptible() fails, the statement passed to the
second argument of cond_guard() returns -EINTR.

Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
---
 drivers/cxl/core/region.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index ce0e2d82bb2b..704102f75c14 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -666,28 +666,20 @@ static size_t show_targetN(struct cxl_region *cxlr, char *buf, int pos)
 {
 	struct cxl_region_params *p = &cxlr->params;
 	struct cxl_endpoint_decoder *cxled;
-	int rc;
 
-	rc = down_read_interruptible(&cxl_region_rwsem);
-	if (rc)
-		return rc;
+	cond_guard(rwsem_read_intr, return -EINTR, &cxl_region_rwsem);
 
 	if (pos >= p->interleave_ways) {
 		dev_dbg(&cxlr->dev, "position %d out of range %d\n", pos,
 			p->interleave_ways);
-		rc = -ENXIO;
-		goto out;
+		return -ENXIO;
 	}
 
 	cxled = p->targets[pos];
 	if (!cxled)
-		rc = sysfs_emit(buf, "\n");
-	else
-		rc = sysfs_emit(buf, "%s\n", dev_name(&cxled->cxld.dev));
-out:
-	up_read(&cxl_region_rwsem);
+		return sysfs_emit(buf, "\n");
 
-	return rc;
+	return sysfs_emit(buf, "%s\n", dev_name(&cxled->cxld.dev));
 }
 
 static int match_free_decoder(struct device *dev, void *data)
-- 
2.43.2

[PATCH 3/3 v5] cxl/memdev: Use cond_guard() in cxl_inject_poison()

[Fabio M. De Francesco]

Use cond_guard() in cxl_inject_poison() to not open code two up_write()
in an 'out' block. If the down_read_interruptible() fail, the statements
passed as the second argument of cond_guard() return -EINTR.

Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
---
 drivers/cxl/core/memdev.c | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
index dae8802ecdb0..bd97eea65bb0 100644
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -331,19 +331,13 @@ int cxl_inject_poison(struct cxl_memdev *cxlmd, u64 dpa)
 	if (!IS_ENABLED(CONFIG_DEBUG_FS))
 		return 0;
 
-	rc = down_read_interruptible(&cxl_region_rwsem);
-	if (rc)
-		return rc;
+	cond_guard(rwsem_read_intr, return -EINTR, &cxl_region_rwsem);
 
-	rc = down_read_interruptible(&cxl_dpa_rwsem);
-	if (rc) {
-		up_read(&cxl_region_rwsem);
-		return rc;
-	}
+	cond_guard(rwsem_read_intr, return -EINTR, &cxl_dpa_rwsem);
 
 	rc = cxl_validate_poison_dpa(cxlmd, dpa);
 	if (rc)
-		goto out;
+		return rc;
 
 	inject.address = cpu_to_le64(dpa);
 	mbox_cmd = (struct cxl_mbox_cmd) {
@@ -353,7 +347,7 @@ int cxl_inject_poison(struct cxl_memdev *cxlmd, u64 dpa)
 	};
 	rc = cxl_internal_send_cmd(mds, &mbox_cmd);
 	if (rc)
-		goto out;
+		return rc;
 
 	cxlr = cxl_dpa_to_region(cxlmd, dpa);
 	if (cxlr)
@@ -366,11 +360,8 @@ int cxl_inject_poison(struct cxl_memdev *cxlmd, u64 dpa)
 		.length = cpu_to_le32(1),
 	};
 	trace_cxl_poison(cxlmd, cxlr, &record, 0, 0, CXL_POISON_TRACE_INJECT);
-out:
-	up_read(&cxl_dpa_rwsem);
-	up_read(&cxl_region_rwsem);
 
-	return rc;
+	return 0;
 }
 EXPORT_SYMBOL_NS_GPL(cxl_inject_poison, CXL);
 
-- 
2.43.2

Re: [PATCH 3/3 v5] cxl/memdev: Use cond_guard() in cxl_inject_poison()

[Jonathan Cameron]

On Sat, 17 Feb 2024 11:59:04 +0100
"Fabio M. De Francesco" <fabio.maria.de.francesco@linux.intel.com> wrote:

> Use cond_guard() in cxl_inject_poison() to not open code two up_write()
> in an 'out' block. If the down_read_interruptible() fail, the statements
> passed as the second argument of cond_guard() return -EINTR.
> 
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Re: [PATCH 3/3 v5] cxl/memdev: Use cond_guard() in cxl_inject_poison()

[Dave Jiang]

On 2/17/24 3:59 AM, Fabio M. De Francesco wrote:
> Use cond_guard() in cxl_inject_poison() to not open code two up_write()
> in an 'out' block. If the down_read_interruptible() fail, the statements
> passed as the second argument of cond_guard() return -EINTR.
> 
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  drivers/cxl/core/memdev.c | 19 +++++--------------
>  1 file changed, 5 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index dae8802ecdb0..bd97eea65bb0 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -331,19 +331,13 @@ int cxl_inject_poison(struct cxl_memdev *cxlmd, u64 dpa)
>  	if (!IS_ENABLED(CONFIG_DEBUG_FS))
>  		return 0;
>  
> -	rc = down_read_interruptible(&cxl_region_rwsem);
> -	if (rc)
> -		return rc;
> +	cond_guard(rwsem_read_intr, return -EINTR, &cxl_region_rwsem);
>  
> -	rc = down_read_interruptible(&cxl_dpa_rwsem);
> -	if (rc) {
> -		up_read(&cxl_region_rwsem);
> -		return rc;
> -	}
> +	cond_guard(rwsem_read_intr, return -EINTR, &cxl_dpa_rwsem);
>  
>  	rc = cxl_validate_poison_dpa(cxlmd, dpa);
>  	if (rc)
> -		goto out;
> +		return rc;
>  
>  	inject.address = cpu_to_le64(dpa);
>  	mbox_cmd = (struct cxl_mbox_cmd) {
> @@ -353,7 +347,7 @@ int cxl_inject_poison(struct cxl_memdev *cxlmd, u64 dpa)
>  	};
>  	rc = cxl_internal_send_cmd(mds, &mbox_cmd);
>  	if (rc)
> -		goto out;
> +		return rc;
>  
>  	cxlr = cxl_dpa_to_region(cxlmd, dpa);
>  	if (cxlr)
> @@ -366,11 +360,8 @@ int cxl_inject_poison(struct cxl_memdev *cxlmd, u64 dpa)
>  		.length = cpu_to_le32(1),
>  	};
>  	trace_cxl_poison(cxlmd, cxlr, &record, 0, 0, CXL_POISON_TRACE_INJECT);
> -out:
> -	up_read(&cxl_dpa_rwsem);
> -	up_read(&cxl_region_rwsem);
>  
> -	return rc;
> +	return 0;
>  }
>  EXPORT_SYMBOL_NS_GPL(cxl_inject_poison, CXL);
>