[PATCH 0/9] relay: cleanup and const callbacks, take 2

[PATCH 0/9] relay: cleanup and const callbacks, take 2

[Jani Nikula]

This is v2 of [1], with a number of cleanups added first based on
Christoph's feedback, making the actual constness patch much smaller and
cleaner.

I don't know who actually maintains relay, it's not in MAINTAINERS -
Cc'd Andrew just in case.

I'd think it would be simplest to queue patches 5-9 via whichever tree
the relay patches get merged. They're all one-liners so neglible
conflict potential.

BR,
Jani.


[1] http://lore.kernel.org/r/20201118165320.26829-1-jani.nikula@intel.com


Cc: linux-block@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>
Cc: ath11k@lists.infradead.org
Cc: ath10k@lists.infradead.org
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: linux-wireless@vger.kernel.org
Cc: QCA ath9k Development <ath9k-devel@qca.qualcomm.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>


Jani Nikula (9):
  relay: remove unused buf_mapped and buf_unmapped callbacks
  relay: require non-NULL callbacks in relay_open()
  relay: make create_buf_file and remove_buf_file callbacks mandatory
  relay: allow the use of const callback structs
  drm/i915: make relay callbacks const
  ath10k: make relay callbacks const
  ath11k: make relay callbacks const
  ath9k: make relay callbacks const
  blktrace: make relay callbacks const

 drivers/gpu/drm/i915/gt/uc/intel_guc_log.c    |   2 +-
 drivers/net/wireless/ath/ath10k/spectral.c    |   2 +-
 drivers/net/wireless/ath/ath11k/spectral.c    |   2 +-
 .../net/wireless/ath/ath9k/common-spectral.c  |   2 +-
 include/linux/relay.h                         |  29 ++---
 kernel/relay.c                                | 107 +++---------------
 kernel/trace/blktrace.c                       |   2 +-
 7 files changed, 26 insertions(+), 120 deletions(-)

-- 
2.20.1

[PATCH 1/9] relay: remove unused buf_mapped and buf_unmapped callbacks

[Jani Nikula]

No relay client uses the buf_mapped or buf_unmapped callbacks. Remove
them. This makes relay's vm_operations_struct close callback a dummy,
remove it as well.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 include/linux/relay.h | 19 -------------------
 kernel/relay.c        | 34 ----------------------------------
 2 files changed, 53 deletions(-)

diff --git a/include/linux/relay.h b/include/linux/relay.h
index e13a333e7c37..b3c4f49f6951 100644
--- a/include/linux/relay.h
+++ b/include/linux/relay.h
@@ -101,25 +101,6 @@ struct rchan_callbacks
 			     void *prev_subbuf,
 			     size_t prev_padding);
 
-	/*
-	 * buf_mapped - relay buffer mmap notification
-	 * @buf: the channel buffer
-	 * @filp: relay file pointer
-	 *
-	 * Called when a relay file is successfully mmapped
-	 */
-        void (*buf_mapped)(struct rchan_buf *buf,
-			   struct file *filp);
-
-	/*
-	 * buf_unmapped - relay buffer unmap notification
-	 * @buf: the channel buffer
-	 * @filp: relay file pointer
-	 *
-	 * Called when a relay file is successfully unmapped
-	 */
-        void (*buf_unmapped)(struct rchan_buf *buf,
-			     struct file *filp);
 	/*
 	 * create_buf_file - create file to represent a relay channel buffer
 	 * @filename: the name of the file to create
diff --git a/kernel/relay.c b/kernel/relay.c
index b08d936d5fa7..b51343642bf4 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -27,15 +27,6 @@
 static DEFINE_MUTEX(relay_channels_mutex);
 static LIST_HEAD(relay_channels);
 
-/*
- * close() vm_op implementation for relay file mapping.
- */
-static void relay_file_mmap_close(struct vm_area_struct *vma)
-{
-	struct rchan_buf *buf = vma->vm_private_data;
-	buf->chan->cb->buf_unmapped(buf, vma->vm_file);
-}
-
 /*
  * fault() vm_op implementation for relay file mapping.
  */
@@ -62,7 +53,6 @@ static vm_fault_t relay_buf_fault(struct vm_fault *vmf)
  */
 static const struct vm_operations_struct relay_file_mmap_ops = {
 	.fault = relay_buf_fault,
-	.close = relay_file_mmap_close,
 };
 
 /*
@@ -96,7 +86,6 @@ static void relay_free_page_array(struct page **array)
 static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
 {
 	unsigned long length = vma->vm_end - vma->vm_start;
-	struct file *filp = vma->vm_file;
 
 	if (!buf)
 		return -EBADF;
@@ -107,7 +96,6 @@ static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
 	vma->vm_ops = &relay_file_mmap_ops;
 	vma->vm_flags |= VM_DONTEXPAND;
 	vma->vm_private_data = buf;
-	buf->chan->cb->buf_mapped(buf, filp);
 
 	return 0;
 }
@@ -283,22 +271,6 @@ static int subbuf_start_default_callback (struct rchan_buf *buf,
 	return 1;
 }
 
-/*
- * buf_mapped() default callback.  Does nothing.
- */
-static void buf_mapped_default_callback(struct rchan_buf *buf,
-					struct file *filp)
-{
-}
-
-/*
- * buf_unmapped() default callback.  Does nothing.
- */
-static void buf_unmapped_default_callback(struct rchan_buf *buf,
-					  struct file *filp)
-{
-}
-
 /*
  * create_buf_file_create() default callback.  Does nothing.
  */
@@ -322,8 +294,6 @@ static int remove_buf_file_default_callback(struct dentry *dentry)
 /* relay channel default callbacks */
 static struct rchan_callbacks default_channel_callbacks = {
 	.subbuf_start = subbuf_start_default_callback,
-	.buf_mapped = buf_mapped_default_callback,
-	.buf_unmapped = buf_unmapped_default_callback,
 	.create_buf_file = create_buf_file_default_callback,
 	.remove_buf_file = remove_buf_file_default_callback,
 };
@@ -509,10 +479,6 @@ static void setup_callbacks(struct rchan *chan,
 
 	if (!cb->subbuf_start)
 		cb->subbuf_start = subbuf_start_default_callback;
-	if (!cb->buf_mapped)
-		cb->buf_mapped = buf_mapped_default_callback;
-	if (!cb->buf_unmapped)
-		cb->buf_unmapped = buf_unmapped_default_callback;
 	if (!cb->create_buf_file)
 		cb->create_buf_file = create_buf_file_default_callback;
 	if (!cb->remove_buf_file)
-- 
2.20.1

[PATCH 2/9] relay: require non-NULL callbacks in relay_open()

[Jani Nikula]

There are no clients passing NULL callbacks, which makes sense as it
wouldn't even create a file. Require non-NULL callbacks, and throw away
the handling for NULL callbacks.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 kernel/relay.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/kernel/relay.c b/kernel/relay.c
index b51343642bf4..d9b8185161a8 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -291,13 +291,6 @@ static int remove_buf_file_default_callback(struct dentry *dentry)
 	return -EINVAL;
 }
 
-/* relay channel default callbacks */
-static struct rchan_callbacks default_channel_callbacks = {
-	.subbuf_start = subbuf_start_default_callback,
-	.create_buf_file = create_buf_file_default_callback,
-	.remove_buf_file = remove_buf_file_default_callback,
-};
-
 /**
  *	wakeup_readers - wake up readers waiting on a channel
  *	@work: contains the channel buffer
@@ -472,11 +465,6 @@ static void relay_close_buf(struct rchan_buf *buf)
 static void setup_callbacks(struct rchan *chan,
 				   struct rchan_callbacks *cb)
 {
-	if (!cb) {
-		chan->cb = &default_channel_callbacks;
-		return;
-	}
-
 	if (!cb->subbuf_start)
 		cb->subbuf_start = subbuf_start_default_callback;
 	if (!cb->create_buf_file)
@@ -542,6 +530,8 @@ struct rchan *relay_open(const char *base_filename,
 		return NULL;
 	if (subbuf_size > UINT_MAX / n_subbufs)
 		return NULL;
+	if (!cb)
+		return NULL;
 
 	chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
 	if (!chan)
-- 
2.20.1

[PATCH 3/9] relay: make create_buf_file and remove_buf_file callbacks mandatory

[Jani Nikula]

All clients provide create_buf_file and remove_buf_file callbacks, and
they're required for relay to make sense. There is no point in them
being optional.

Also document whether each callback is mandatory/optional.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 include/linux/relay.h |  6 ++++++
 kernel/relay.c        | 26 +-------------------------
 2 files changed, 7 insertions(+), 25 deletions(-)

diff --git a/include/linux/relay.h b/include/linux/relay.h
index b3c4f49f6951..99d024475ba5 100644
--- a/include/linux/relay.h
+++ b/include/linux/relay.h
@@ -89,6 +89,8 @@ struct rchan_callbacks
 	 * The client should return 1 to continue logging, 0 to stop
 	 * logging.
 	 *
+	 * This callback is optional.
+	 *
 	 * NOTE: subbuf_start will also be invoked when the buffer is
 	 *       created, so that the first sub-buffer can be initialized
 	 *       if necessary.  In this case, prev_subbuf will be NULL.
@@ -122,6 +124,8 @@ struct rchan_callbacks
 	 * cause relay_open() to create a single global buffer rather
 	 * than the default set of per-cpu buffers.
 	 *
+	 * This callback is mandatory.
+	 *
 	 * See Documentation/filesystems/relay.rst for more info.
 	 */
 	struct dentry *(*create_buf_file)(const char *filename,
@@ -139,6 +143,8 @@ struct rchan_callbacks
 	 * channel buffer.
 	 *
 	 * The callback should return 0 if successful, negative if not.
+	 *
+	 * This callback is mandatory.
 	 */
 	int (*remove_buf_file)(struct dentry *dentry);
 };
diff --git a/kernel/relay.c b/kernel/relay.c
index d9b8185161a8..dd4ec4ec07f3 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -271,26 +271,6 @@ static int subbuf_start_default_callback (struct rchan_buf *buf,
 	return 1;
 }
 
-/*
- * create_buf_file_create() default callback.  Does nothing.
- */
-static struct dentry *create_buf_file_default_callback(const char *filename,
-						       struct dentry *parent,
-						       umode_t mode,
-						       struct rchan_buf *buf,
-						       int *is_global)
-{
-	return NULL;
-}
-
-/*
- * remove_buf_file() default callback.  Does nothing.
- */
-static int remove_buf_file_default_callback(struct dentry *dentry)
-{
-	return -EINVAL;
-}
-
 /**
  *	wakeup_readers - wake up readers waiting on a channel
  *	@work: contains the channel buffer
@@ -467,10 +447,6 @@ static void setup_callbacks(struct rchan *chan,
 {
 	if (!cb->subbuf_start)
 		cb->subbuf_start = subbuf_start_default_callback;
-	if (!cb->create_buf_file)
-		cb->create_buf_file = create_buf_file_default_callback;
-	if (!cb->remove_buf_file)
-		cb->remove_buf_file = remove_buf_file_default_callback;
 	chan->cb = cb;
 }
 
@@ -530,7 +506,7 @@ struct rchan *relay_open(const char *base_filename,
 		return NULL;
 	if (subbuf_size > UINT_MAX / n_subbufs)
 		return NULL;
-	if (!cb)
+	if (!cb || !cb->create_buf_file || !cb->remove_buf_file)
 		return NULL;
 
 	chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
-- 
2.20.1

[PATCH 4/9] relay: allow the use of const callback structs

[Jani Nikula]

None of the relay users require the use of mutable structs for
callbacks, however the relay code does. Instead of assigning the default
callback for subbuf_start, add a wrapper to conditionally call the
client callback if available, and fall back to default behaviour
otherwise.

This lets all relay users make their struct rchan_callbacks const data.

Cc: linux-block@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>
Cc: ath11k@lists.infradead.org
Cc: ath10k@lists.infradead.org
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: linux-wireless@vger.kernel.org
Cc: QCA ath9k Development <ath9k-devel@qca.qualcomm.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

---

v2: Simplify after nuking some callbacks and making some others
mandatory in previous patches, as per Christoph's review comments.

I thought about adding wrappers for the now-mandatory create_buf_file
and remove_buf_file as well, for consistency, but ended up leaving them
out.
---
 include/linux/relay.h |  4 ++--
 kernel/relay.c        | 35 +++++++++++------------------------
 2 files changed, 13 insertions(+), 26 deletions(-)

diff --git a/include/linux/relay.h b/include/linux/relay.h
index 99d024475ba5..72b876dd5cb8 100644
--- a/include/linux/relay.h
+++ b/include/linux/relay.h
@@ -62,7 +62,7 @@ struct rchan
 	size_t subbuf_size;		/* sub-buffer size */
 	size_t n_subbufs;		/* number of sub-buffers per buffer */
 	size_t alloc_size;		/* total buffer size allocated */
-	struct rchan_callbacks *cb;	/* client callbacks */
+	const struct rchan_callbacks *cb; /* client callbacks */
 	struct kref kref;		/* channel refcount */
 	void *private_data;		/* for user-defined data */
 	size_t last_toobig;		/* tried to log event > subbuf size */
@@ -157,7 +157,7 @@ struct rchan *relay_open(const char *base_filename,
 			 struct dentry *parent,
 			 size_t subbuf_size,
 			 size_t n_subbufs,
-			 struct rchan_callbacks *cb,
+			 const struct rchan_callbacks *cb,
 			 void *private_data);
 extern int relay_late_setup_files(struct rchan *chan,
 				  const char *base_filename,
diff --git a/kernel/relay.c b/kernel/relay.c
index dd4ec4ec07f3..02bdba5372cb 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -252,19 +252,14 @@ EXPORT_SYMBOL_GPL(relay_buf_full);
  * High-level relay kernel API and associated functions.
  */
 
-/*
- * rchan_callback implementations defining default channel behavior.  Used
- * in place of corresponding NULL values in client callback struct.
- */
-
-/*
- * subbuf_start() default callback.  Does nothing.
- */
-static int subbuf_start_default_callback (struct rchan_buf *buf,
-					  void *subbuf,
-					  void *prev_subbuf,
-					  size_t prev_padding)
+/* subbuf_start callback wrapper */
+static int cb_subbuf_start(struct rchan_buf *buf, void *subbuf,
+			   void *prev_subbuf, size_t prev_padding)
 {
+	if (buf->chan->cb->subbuf_start)
+		return buf->chan->cb->subbuf_start(buf, subbuf,
+						   prev_subbuf, prev_padding);
+
 	if (relay_buf_full(buf))
 		return 0;
 
@@ -314,7 +309,7 @@ static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 	for (i = 0; i < buf->chan->n_subbufs; i++)
 		buf->padding[i] = 0;
 
-	buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
+	cb_subbuf_start(buf, buf->data, NULL, 0);
 }
 
 /**
@@ -442,14 +437,6 @@ static void relay_close_buf(struct rchan_buf *buf)
 	kref_put(&buf->kref, relay_remove_buf);
 }
 
-static void setup_callbacks(struct rchan *chan,
-				   struct rchan_callbacks *cb)
-{
-	if (!cb->subbuf_start)
-		cb->subbuf_start = subbuf_start_default_callback;
-	chan->cb = cb;
-}
-
 int relay_prepare_cpu(unsigned int cpu)
 {
 	struct rchan *chan;
@@ -495,7 +482,7 @@ struct rchan *relay_open(const char *base_filename,
 			 struct dentry *parent,
 			 size_t subbuf_size,
 			 size_t n_subbufs,
-			 struct rchan_callbacks *cb,
+			 const struct rchan_callbacks *cb,
 			 void *private_data)
 {
 	unsigned int i;
@@ -529,7 +516,7 @@ struct rchan *relay_open(const char *base_filename,
 		chan->has_base_filename = 1;
 		strlcpy(chan->base_filename, base_filename, NAME_MAX);
 	}
-	setup_callbacks(chan, cb);
+	chan->cb = cb;
 	kref_init(&chan->kref);
 
 	mutex_lock(&relay_channels_mutex);
@@ -712,7 +699,7 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 	new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 	new = buf->start + new_subbuf * buf->chan->subbuf_size;
 	buf->offset = 0;
-	if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
+	if (!cb_subbuf_start(buf, new, old, buf->prev_padding)) {
 		buf->offset = buf->chan->subbuf_size + 1;
 		return 0;
 	}
-- 
2.20.1

[PATCH 5/9] drm/i915: make relay callbacks const

[Jani Nikula]

Now that relay_open() accepts const callbacks, make relay callbacks
const.

Cc: intel-gfx@lists.freedesktop.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/gt/uc/intel_guc_log.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_log.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_log.c
index 9bbe8a795cb8..c92f2c056db4 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_log.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_log.c
@@ -134,7 +134,7 @@ static int remove_buf_file_callback(struct dentry *dentry)
 }
 
 /* relay channel callbacks */
-static struct rchan_callbacks relay_callbacks = {
+static const struct rchan_callbacks relay_callbacks = {
 	.subbuf_start = subbuf_start_callback,
 	.create_buf_file = create_buf_file_callback,
 	.remove_buf_file = remove_buf_file_callback,
-- 
2.20.1

[PATCH 6/9] ath10k: make relay callbacks const

[Jani Nikula]

Now that relay_open() accepts const callbacks, make relay callbacks
const.

Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: ath10k@lists.infradead.org
Acked-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/net/wireless/ath/ath10k/spectral.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath10k/spectral.c b/drivers/net/wireless/ath/ath10k/spectral.c
index 5db6bff5193b..68254a967ccb 100644
--- a/drivers/net/wireless/ath/ath10k/spectral.c
+++ b/drivers/net/wireless/ath/ath10k/spectral.c
@@ -497,7 +497,7 @@ static int remove_buf_file_handler(struct dentry *dentry)
 	return 0;
 }
 
-static struct rchan_callbacks rfs_spec_scan_cb = {
+static const struct rchan_callbacks rfs_spec_scan_cb = {
 	.create_buf_file = create_buf_file_handler,
 	.remove_buf_file = remove_buf_file_handler,
 };
-- 
2.20.1

[PATCH 7/9] ath11k: make relay callbacks const

[Jani Nikula]

Now that relay_open() accepts const callbacks, make relay callbacks
const.

Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: ath11k@lists.infradead.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/net/wireless/ath/ath11k/spectral.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath11k/spectral.c b/drivers/net/wireless/ath/ath11k/spectral.c
index ac2a8cfdc1c0..1afe67759659 100644
--- a/drivers/net/wireless/ath/ath11k/spectral.c
+++ b/drivers/net/wireless/ath/ath11k/spectral.c
@@ -148,7 +148,7 @@ static int remove_buf_file_handler(struct dentry *dentry)
 	return 0;
 }
 
-static struct rchan_callbacks rfs_scan_cb = {
+static const struct rchan_callbacks rfs_scan_cb = {
 	.create_buf_file = create_buf_file_handler,
 	.remove_buf_file = remove_buf_file_handler,
 };
-- 
2.20.1

[PATCH 8/9] ath9k: make relay callbacks const

[Jani Nikula]

Now that relay_open() accepts const callbacks, make relay callbacks
const.

Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: QCA ath9k Development <ath9k-devel@qca.qualcomm.com>
Cc: linux-wireless@vger.kernel.org
Acked-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/net/wireless/ath/ath9k/common-spectral.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath9k/common-spectral.c b/drivers/net/wireless/ath/ath9k/common-spectral.c
index 21191955a7c1..e055adfb5361 100644
--- a/drivers/net/wireless/ath/ath9k/common-spectral.c
+++ b/drivers/net/wireless/ath/ath9k/common-spectral.c
@@ -1053,7 +1053,7 @@ static int remove_buf_file_handler(struct dentry *dentry)
 	return 0;
 }
 
-static struct rchan_callbacks rfs_spec_scan_cb = {
+static const struct rchan_callbacks rfs_spec_scan_cb = {
 	.create_buf_file = create_buf_file_handler,
 	.remove_buf_file = remove_buf_file_handler,
 };
-- 
2.20.1

[PATCH 9/9] blktrace: make relay callbacks const

[Jani Nikula]

Now that relay_open() accepts const callbacks, make relay callbacks
const.

Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 kernel/trace/blktrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index f1022945e346..b5c4b9ade960 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -449,7 +449,7 @@ static struct dentry *blk_create_buf_file_callback(const char *filename,
 					&relay_file_operations);
 }
 
-static struct rchan_callbacks blk_relay_callbacks = {
+static const struct rchan_callbacks blk_relay_callbacks = {
 	.subbuf_start		= blk_subbuf_start_callback,
 	.create_buf_file	= blk_create_buf_file_callback,
 	.remove_buf_file	= blk_remove_buf_file_callback,
-- 
2.20.1

Re: [PATCH 0/9] relay: cleanup and const callbacks, take 2

[Kalle Valo]

Jani Nikula <jani.nikula@intel.com> writes:

> This is v2 of [1], with a number of cleanups added first based on
> Christoph's feedback, making the actual constness patch much smaller and
> cleaner.
>
> I don't know who actually maintains relay, it's not in MAINTAINERS -
> Cc'd Andrew just in case.
>
> I'd think it would be simplest to queue patches 5-9 via whichever tree
> the relay patches get merged. They're all one-liners so neglible
> conflict potential.
>
> BR,
> Jani.
>
>
> [1] http://lore.kernel.org/r/20201118165320.26829-1-jani.nikula@intel.com
>
>
> Cc: linux-block@vger.kernel.org
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: ath11k@lists.infradead.org
> Cc: ath10k@lists.infradead.org
> Cc: Kalle Valo <kvalo@codeaurora.org>
> Cc: linux-wireless@vger.kernel.org
> Cc: QCA ath9k Development <ath9k-devel@qca.qualcomm.com>
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
>
>
> Jani Nikula (9):
>   relay: remove unused buf_mapped and buf_unmapped callbacks
>   relay: require non-NULL callbacks in relay_open()
>   relay: make create_buf_file and remove_buf_file callbacks mandatory
>   relay: allow the use of const callback structs
>   drm/i915: make relay callbacks const
>   ath10k: make relay callbacks const
>   ath11k: make relay callbacks const
>   ath9k: make relay callbacks const
>   blktrace: make relay callbacks const

For ath9k, ath10k & ath11k:

Acked-by: Kalle Valo <kvalo@codeaurora.org>

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches

Re: [PATCH 1/9] relay: remove unused buf_mapped and buf_unmapped callbacks

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 2/9] relay: require non-NULL callbacks in relay_open()

[Christoph Hellwig]

On Mon, Nov 23, 2020 at 07:59:22PM +0200, Jani Nikula wrote:
> There are no clients passing NULL callbacks, which makes sense as it
> wouldn't even create a file. Require non-NULL callbacks, and throw away
> the handling for NULL callbacks.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 3/9] relay: make create_buf_file and remove_buf_file callbacks mandatory

[Christoph Hellwig]

On Mon, Nov 23, 2020 at 07:59:23PM +0200, Jani Nikula wrote:
> All clients provide create_buf_file and remove_buf_file callbacks, and
> they're required for relay to make sense. There is no point in them
> being optional.
> 
> Also document whether each callback is mandatory/optional.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 4/9] relay: allow the use of const callback structs

[Christoph Hellwig]

> +/* subbuf_start callback wrapper */
> +static int cb_subbuf_start(struct rchan_buf *buf, void *subbuf,
> +			   void *prev_subbuf, size_t prev_padding)

I don't think the comment adds any information over just looking at the
function and the two callers.  I'd also name it relay_subbuf_start
instead of the cb_ prefix not used anywhere else in the file.


>  {
> +	if (buf->chan->cb->subbuf_start)
> +		return buf->chan->cb->subbuf_start(buf, subbuf,
> +						   prev_subbuf, prev_padding);
> +
>  	if (relay_buf_full(buf))
>  		return 0;

This could also be simplified a bit more to:

	if (!buf->chan->cb->subbuf_start)
		return !relay_buf_full(buf);
	return buf->chan->cb->subbuf_start(buf, subbuf, prev_subbuf,
					   prev_padding);

Otherwise this looks good to me:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 5/9] drm/i915: make relay callbacks const

[Christoph Hellwig]

On Mon, Nov 23, 2020 at 07:59:25PM +0200, Jani Nikula wrote:
> Now that relay_open() accepts const callbacks, make relay callbacks
> const.
> 
> Cc: intel-gfx@lists.freedesktop.org
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 6/9] ath10k: make relay callbacks const

[Christoph Hellwig]

On Mon, Nov 23, 2020 at 07:59:26PM +0200, Jani Nikula wrote:
> Now that relay_open() accepts const callbacks, make relay callbacks
> const.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 7/9] ath11k: make relay callbacks const

[Christoph Hellwig]

On Mon, Nov 23, 2020 at 07:59:27PM +0200, Jani Nikula wrote:
> Now that relay_open() accepts const callbacks, make relay callbacks
> const.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 8/9] ath9k: make relay callbacks const

[Christoph Hellwig]

On Mon, Nov 23, 2020 at 07:59:28PM +0200, Jani Nikula wrote:
> Now that relay_open() accepts const callbacks, make relay callbacks
> const.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 9/9] blktrace: make relay callbacks const

[Christoph Hellwig]

On Mon, Nov 23, 2020 at 07:59:29PM +0200, Jani Nikula wrote:
> Now that relay_open() accepts const callbacks, make relay callbacks
> const.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH v3] relay: allow the use of const callback structs

[Jani Nikula]

None of the relay users require the use of mutable structs for
callbacks, however the relay code does. Instead of assigning the default
callback for subbuf_start, add a wrapper to conditionally call the
client callback if available, and fall back to default behaviour
otherwise.

This lets all relay users make their struct rchan_callbacks const data.

Cc: linux-block@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>
Cc: ath11k@lists.infradead.org
Cc: ath10k@lists.infradead.org
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: linux-wireless@vger.kernel.org
Cc: QCA ath9k Development <ath9k-devel@qca.qualcomm.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

---

v2: Simplify after nuking some callbacks and making some others
mandatory in previous patches, as per Christoph's review comments.

I thought about adding wrappers for the now-mandatory create_buf_file
and remove_buf_file as well, for consistency, but ended up leaving them
out.

v3: Rename cb_subbuf_start to relay_subbuf_start, minor finishing
touches
---
 include/linux/relay.h |  4 ++--
 kernel/relay.c        | 37 ++++++++++---------------------------
 2 files changed, 12 insertions(+), 29 deletions(-)

diff --git a/include/linux/relay.h b/include/linux/relay.h
index 99d024475ba5..72b876dd5cb8 100644
--- a/include/linux/relay.h
+++ b/include/linux/relay.h
@@ -62,7 +62,7 @@ struct rchan
 	size_t subbuf_size;		/* sub-buffer size */
 	size_t n_subbufs;		/* number of sub-buffers per buffer */
 	size_t alloc_size;		/* total buffer size allocated */
-	struct rchan_callbacks *cb;	/* client callbacks */
+	const struct rchan_callbacks *cb; /* client callbacks */
 	struct kref kref;		/* channel refcount */
 	void *private_data;		/* for user-defined data */
 	size_t last_toobig;		/* tried to log event > subbuf size */
@@ -157,7 +157,7 @@ struct rchan *relay_open(const char *base_filename,
 			 struct dentry *parent,
 			 size_t subbuf_size,
 			 size_t n_subbufs,
-			 struct rchan_callbacks *cb,
+			 const struct rchan_callbacks *cb,
 			 void *private_data);
 extern int relay_late_setup_files(struct rchan *chan,
 				  const char *base_filename,
diff --git a/kernel/relay.c b/kernel/relay.c
index dd4ec4ec07f3..d1a67fbb819d 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -252,23 +252,14 @@ EXPORT_SYMBOL_GPL(relay_buf_full);
  * High-level relay kernel API and associated functions.
  */
 
-/*
- * rchan_callback implementations defining default channel behavior.  Used
- * in place of corresponding NULL values in client callback struct.
- */
-
-/*
- * subbuf_start() default callback.  Does nothing.
- */
-static int subbuf_start_default_callback (struct rchan_buf *buf,
-					  void *subbuf,
-					  void *prev_subbuf,
-					  size_t prev_padding)
+static int relay_subbuf_start(struct rchan_buf *buf, void *subbuf,
+			      void *prev_subbuf, size_t prev_padding)
 {
-	if (relay_buf_full(buf))
-		return 0;
+	if (!buf->chan->cb->subbuf_start)
+		return !relay_buf_full(buf);
 
-	return 1;
+	return buf->chan->cb->subbuf_start(buf, subbuf,
+					   prev_subbuf, prev_padding);
 }
 
 /**
@@ -314,7 +305,7 @@ static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 	for (i = 0; i < buf->chan->n_subbufs; i++)
 		buf->padding[i] = 0;
 
-	buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
+	relay_subbuf_start(buf, buf->data, NULL, 0);
 }
 
 /**
@@ -442,14 +433,6 @@ static void relay_close_buf(struct rchan_buf *buf)
 	kref_put(&buf->kref, relay_remove_buf);
 }
 
-static void setup_callbacks(struct rchan *chan,
-				   struct rchan_callbacks *cb)
-{
-	if (!cb->subbuf_start)
-		cb->subbuf_start = subbuf_start_default_callback;
-	chan->cb = cb;
-}
-
 int relay_prepare_cpu(unsigned int cpu)
 {
 	struct rchan *chan;
@@ -495,7 +478,7 @@ struct rchan *relay_open(const char *base_filename,
 			 struct dentry *parent,
 			 size_t subbuf_size,
 			 size_t n_subbufs,
-			 struct rchan_callbacks *cb,
+			 const struct rchan_callbacks *cb,
 			 void *private_data)
 {
 	unsigned int i;
@@ -529,7 +512,7 @@ struct rchan *relay_open(const char *base_filename,
 		chan->has_base_filename = 1;
 		strlcpy(chan->base_filename, base_filename, NAME_MAX);
 	}
-	setup_callbacks(chan, cb);
+	chan->cb = cb;
 	kref_init(&chan->kref);
 
 	mutex_lock(&relay_channels_mutex);
@@ -712,7 +695,7 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 	new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
 	new = buf->start + new_subbuf * buf->chan->subbuf_size;
 	buf->offset = 0;
-	if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
+	if (!relay_subbuf_start(buf, new, old, buf->prev_padding)) {
 		buf->offset = buf->chan->subbuf_size + 1;
 		return 0;
 	}
-- 
2.20.1

Re: [PATCH 4/9] relay: allow the use of const callback structs

[Jani Nikula]

On Tue, 24 Nov 2020, Christoph Hellwig <hch@infradead.org> wrote:
> Otherwise this looks good to me:

v3 sent.

> Reviewed-by: Christoph Hellwig <hch@lst.de>

Thanks for the reviews, appreciated.

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Graphics Center