Patch "pstore: Make spinlock per zone instead of global" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    pstore: Make spinlock per zone instead of global

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     pstore-make-spinlock-per-zone-instead-of-global.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 109704492ef637956265ec2eb72ae7b3b39eb6f4 Mon Sep 17 00:00:00 2001
From: Joel Fernandes <joelaf@google.com>
Date: Thu, 20 Oct 2016 00:34:00 -0700
Subject: pstore: Make spinlock per zone instead of global

From: Joel Fernandes <joelaf@google.com>

commit 109704492ef637956265ec2eb72ae7b3b39eb6f4 upstream.

Currently pstore has a global spinlock for all zones. Since the zones
are independent and modify different areas of memory, there's no need
to have a global lock, so we should use a per-zone lock as introduced
here. Also, when ramoops's ftrace use-case has a FTRACE_PER_CPU flag
introduced later, which splits the ftrace memory area into a single zone
per CPU, it will eliminate the need for locking. In preparation for this,
make the locking optional.

Signed-off-by: Joel Fernandes <joelaf@google.com>
[kees: updated commit message]
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/pstore/ram_core.c       |   11 +++++------
 include/linux/pstore_ram.h |    1 +
 2 files changed, 6 insertions(+), 6 deletions(-)

--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -47,8 +47,6 @@ static inline size_t buffer_start(struct
 	return atomic_read(&prz->buffer->start);
 }
 
-static DEFINE_RAW_SPINLOCK(buffer_lock);
-
 /* increase and wrap the start pointer, returning the old value */
 static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)
 {
@@ -56,7 +54,7 @@ static size_t buffer_start_add(struct pe
 	int new;
 	unsigned long flags;
 
-	raw_spin_lock_irqsave(&buffer_lock, flags);
+	raw_spin_lock_irqsave(&prz->buffer_lock, flags);
 
 	old = atomic_read(&prz->buffer->start);
 	new = old + a;
@@ -64,7 +62,7 @@ static size_t buffer_start_add(struct pe
 		new -= prz->buffer_size;
 	atomic_set(&prz->buffer->start, new);
 
-	raw_spin_unlock_irqrestore(&buffer_lock, flags);
+	raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
 
 	return old;
 }
@@ -76,7 +74,7 @@ static void buffer_size_add(struct persi
 	size_t new;
 	unsigned long flags;
 
-	raw_spin_lock_irqsave(&buffer_lock, flags);
+	raw_spin_lock_irqsave(&prz->buffer_lock, flags);
 
 	old = atomic_read(&prz->buffer->size);
 	if (old == prz->buffer_size)
@@ -88,7 +86,7 @@ static void buffer_size_add(struct persi
 	atomic_set(&prz->buffer->size, new);
 
 exit:
-	raw_spin_unlock_irqrestore(&buffer_lock, flags);
+	raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
 }
 
 static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
@@ -450,6 +448,7 @@ static int persistent_ram_post_init(stru
 
 	prz->buffer->sig = sig;
 	persistent_ram_zap(prz);
+	prz->buffer_lock = __RAW_SPIN_LOCK_UNLOCKED(buffer_lock);
 
 	return 0;
 }
--- a/include/linux/pstore_ram.h
+++ b/include/linux/pstore_ram.h
@@ -39,6 +39,7 @@ struct persistent_ram_zone {
 	void *vaddr;
 	struct persistent_ram_buffer *buffer;
 	size_t buffer_size;
+	raw_spinlock_t buffer_lock;
 
 	/* ECC correction */
 	char *par_buffer;


Patches currently in stable-queue which might be from joelaf@google.com are

queue-4.4/pstore-make-spinlock-per-zone-instead-of-global.patch