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Message-Id: <1476947872-14485-3-git-send-email-joelaf@google.com>
Date: Thu, 20 Oct 2016 00:17:47 -0700
From: Joel Fernandes <joelaf@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
Joel Fernandes <joelaf@...gle.com>,
Anton Vorontsov <anton@...msg.org>,
Colin Cross <ccross@...roid.com>,
Tony Luck <tony.luck@...el.com>
Subject: [PATCH 2/7] pstore: locking: dont lock unless caller asks to
In preparation of not locking at all for certain buffers depending on if
there's contention, make locking optional depending if caller requested it.
Signed-off-by: Joel Fernandes <joelaf@...gle.com>
---
fs/pstore/ram.c | 10 +++++-----
fs/pstore/ram_core.c | 27 ++++++++++++++++-----------
include/linux/pstore_ram.h | 10 +++++++++-
3 files changed, 30 insertions(+), 17 deletions(-)
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index f1219af..cb07ef6 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -260,7 +260,7 @@ static size_t ramoops_write_kmsg_hdr(struct persistent_ram_zone *prz,
compressed ? 'C' : 'D');
WARN_ON_ONCE(!hdr);
len = hdr ? strlen(hdr) : 0;
- persistent_ram_write(prz, hdr, len);
+ persistent_ram_write(prz, hdr, len, RAM_LOCK);
kfree(hdr);
return len;
@@ -280,17 +280,17 @@ static int notrace ramoops_pstore_write_buf(enum pstore_type_id type,
if (type == PSTORE_TYPE_CONSOLE) {
if (!cxt->cprz)
return -ENOMEM;
- persistent_ram_write(cxt->cprz, buf, size);
+ persistent_ram_write(cxt->cprz, buf, size, RAM_LOCK);
return 0;
} else if (type == PSTORE_TYPE_FTRACE) {
if (!cxt->fprz)
return -ENOMEM;
- persistent_ram_write(cxt->fprz, buf, size);
+ persistent_ram_write(cxt->fprz, buf, size, RAM_LOCK);
return 0;
} else if (type == PSTORE_TYPE_PMSG) {
if (!cxt->mprz)
return -ENOMEM;
- persistent_ram_write(cxt->mprz, buf, size);
+ persistent_ram_write(cxt->mprz, buf, size, RAM_LOCK);
return 0;
}
@@ -324,7 +324,7 @@ static int notrace ramoops_pstore_write_buf(enum pstore_type_id type,
hlen = ramoops_write_kmsg_hdr(prz, compressed);
if (size + hlen > prz->buffer_size)
size = prz->buffer_size - hlen;
- persistent_ram_write(prz, buf, size);
+ persistent_ram_write(prz, buf, size, RAM_LOCK);
cxt->dump_write_cnt = (cxt->dump_write_cnt + 1) % cxt->max_dump_cnt;
diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index cb92055..69c7b96 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -49,13 +49,15 @@ static inline size_t buffer_start(struct persistent_ram_zone *prz)
}
/* increase and wrap the start pointer, returning the old value */
-static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)
+static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a,
+ int lock)
{
int old;
int new;
unsigned long flags;
- raw_spin_lock_irqsave(&prz->buffer_lock, flags);
+ if (lock == RAM_LOCK)
+ raw_spin_lock_irqsave(&prz->buffer_lock, flags);
old = atomic_read(&prz->buffer->start);
new = old + a;
@@ -63,19 +65,21 @@ static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)
new -= prz->buffer_size;
atomic_set(&prz->buffer->start, new);
- raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
+ if (lock == RAM_LOCK)
+ raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
return old;
}
/* increase the size counter until it hits the max size */
-static void buffer_size_add(struct persistent_ram_zone *prz, size_t a)
+static void buffer_size_add(struct persistent_ram_zone *prz, size_t a, int lock)
{
size_t old;
size_t new;
unsigned long flags;
- raw_spin_lock_irqsave(&prz->buffer_lock, flags);
+ if (lock == RAM_LOCK)
+ raw_spin_lock_irqsave(&prz->buffer_lock, flags);
old = atomic_read(&prz->buffer->size);
if (old == prz->buffer_size)
@@ -87,7 +91,8 @@ static void buffer_size_add(struct persistent_ram_zone *prz, size_t a)
atomic_set(&prz->buffer->size, new);
exit:
- raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
+ if (lock == RAM_LOCK)
+ raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
}
static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
@@ -300,7 +305,7 @@ void persistent_ram_save_old(struct persistent_ram_zone *prz)
}
int notrace persistent_ram_write(struct persistent_ram_zone *prz,
- const void *s, unsigned int count)
+ const void *s, unsigned int count, int lock)
{
int rem;
int c = count;
@@ -311,9 +316,9 @@ int notrace persistent_ram_write(struct persistent_ram_zone *prz,
c = prz->buffer_size;
}
- buffer_size_add(prz, c);
+ buffer_size_add(prz, c, lock);
- start = buffer_start_add(prz, c);
+ start = buffer_start_add(prz, c, lock);
rem = prz->buffer_size - start;
if (unlikely(rem < c)) {
@@ -342,9 +347,9 @@ int notrace persistent_ram_write_user(struct persistent_ram_zone *prz,
c = prz->buffer_size;
}
- buffer_size_add(prz, c);
+ buffer_size_add(prz, c, RAM_LOCK);
- start = buffer_start_add(prz, c);
+ start = buffer_start_add(prz, c, RAM_LOCK);
rem = prz->buffer_size - start;
if (unlikely(rem < c)) {
diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
index 244d242..69f3487 100644
--- a/include/linux/pstore_ram.h
+++ b/include/linux/pstore_ram.h
@@ -24,6 +24,14 @@
#include <linux/list.h>
#include <linux/types.h>
+/*
+ * Choose whether access to the RAM zone requires locking or not. If a zone
+ * can be written to from different CPUs like with ftrace for example, then
+ * RAM_LOCK is used. For all other cases, RAM_NOLOCK should be used.
+ */
+#define RAM_NOLOCK 0
+#define RAM_LOCK 1
+
struct persistent_ram_buffer;
struct rs_control;
@@ -61,7 +69,7 @@ void persistent_ram_free(struct persistent_ram_zone *prz);
void persistent_ram_zap(struct persistent_ram_zone *prz);
int persistent_ram_write(struct persistent_ram_zone *prz, const void *s,
- unsigned int count);
+ unsigned int count, int lock);
int persistent_ram_write_user(struct persistent_ram_zone *prz,
const void __user *s, unsigned int count);
--
2.7.4
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