linux-kernel - [PATCH 3.18 02/50] pstore: Make spinlock per zone instead of global

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Message-Id: <20170804231550.972526635@linuxfoundation.org>
Date:   Fri,  4 Aug 2017 16:15:48 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Joel Fernandes <joelaf@...gle.com>,
        Kees Cook <keescook@...omium.org>, Leo Yan <leo.yan@...aro.org>
Subject: [PATCH 3.18 02/50] pstore: Make spinlock per zone instead of global

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joel Fernandes <joelaf@...gle.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@...gle.com>
[kees: updated commit message]
Signed-off-by: Kees Cook <keescook@...omium.org>
Cc: Leo Yan <leo.yan@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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
@@ -80,8 +80,6 @@ static void buffer_size_add_atomic(struc
 	} while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);
 }
 
-static DEFINE_RAW_SPINLOCK(buffer_lock);
-
 /* increase and wrap the start pointer, returning the old value */
 static size_t buffer_start_add_locked(struct persistent_ram_zone *prz, size_t a)
 {
@@ -89,7 +87,7 @@ static size_t buffer_start_add_locked(st
 	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;
@@ -97,7 +95,7 @@ static size_t buffer_start_add_locked(st
 		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;
 }
@@ -109,7 +107,7 @@ static void buffer_size_add_locked(struc
 	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)
@@ -121,7 +119,7 @@ static void buffer_size_add_locked(struc
 	atomic_set(&prz->buffer->size, new);
 
 exit:
-	raw_spin_unlock_irqrestore(&buffer_lock, flags);
+	raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
 }
 
 static size_t (*buffer_start_add)(struct persistent_ram_zone *, size_t) = buffer_start_add_atomic;
@@ -489,6 +487,7 @@ 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;