pstore: Allow prz to control need for locking
commit 663deb47880f2283809669563c5a52ac7c6aef1a upstream.
In preparation of not locking at all for certain buffers depending on if
there's contention, make locking optional depending on the initialization
of the prz.
Signed-off-by: Joel Fernandes <joelaf@google.com>
[kees: moved locking flag into prz instead of via caller arguments]
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 6ad831b..8b09271 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -434,7 +434,7 @@
for (i = 0; i < cxt->max_dump_cnt; i++) {
cxt->przs[i] = persistent_ram_new(*paddr, cxt->record_size, 0,
&cxt->ecc_info,
- cxt->memtype);
+ cxt->memtype, 0);
if (IS_ERR(cxt->przs[i])) {
err = PTR_ERR(cxt->przs[i]);
dev_err(dev, "failed to request mem region (0x%zx@0x%llx): %d\n",
@@ -471,7 +471,8 @@
return -ENOMEM;
}
- *prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info, cxt->memtype);
+ *prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info,
+ cxt->memtype, 0);
if (IS_ERR(*prz)) {
int err = PTR_ERR(*prz);
diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index cb92055..a857338 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -53,9 +53,10 @@
{
int old;
int new;
- unsigned long flags;
+ unsigned long flags = 0;
- raw_spin_lock_irqsave(&prz->buffer_lock, flags);
+ if (!(prz->flags & PRZ_FLAG_NO_LOCK))
+ raw_spin_lock_irqsave(&prz->buffer_lock, flags);
old = atomic_read(&prz->buffer->start);
new = old + a;
@@ -63,7 +64,8 @@
new -= prz->buffer_size;
atomic_set(&prz->buffer->start, new);
- raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
+ if (!(prz->flags & PRZ_FLAG_NO_LOCK))
+ raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
return old;
}
@@ -73,9 +75,10 @@
{
size_t old;
size_t new;
- unsigned long flags;
+ unsigned long flags = 0;
- raw_spin_lock_irqsave(&prz->buffer_lock, flags);
+ if (!(prz->flags & PRZ_FLAG_NO_LOCK))
+ raw_spin_lock_irqsave(&prz->buffer_lock, flags);
old = atomic_read(&prz->buffer->size);
if (old == prz->buffer_size)
@@ -87,7 +90,8 @@
atomic_set(&prz->buffer->size, new);
exit:
- raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
+ if (!(prz->flags & PRZ_FLAG_NO_LOCK))
+ raw_spin_unlock_irqrestore(&prz->buffer_lock, flags);
}
static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
@@ -463,7 +467,8 @@
}
static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
- struct persistent_ram_ecc_info *ecc_info)
+ struct persistent_ram_ecc_info *ecc_info,
+ unsigned long flags)
{
int ret;
@@ -492,6 +497,7 @@
prz->buffer->sig = sig;
persistent_ram_zap(prz);
prz->buffer_lock = __RAW_SPIN_LOCK_UNLOCKED(buffer_lock);
+ prz->flags = flags;
return 0;
}
@@ -516,7 +522,7 @@
struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
u32 sig, struct persistent_ram_ecc_info *ecc_info,
- unsigned int memtype)
+ unsigned int memtype, u32 flags)
{
struct persistent_ram_zone *prz;
int ret = -ENOMEM;
@@ -531,7 +537,7 @@
if (ret)
goto err;
- ret = persistent_ram_post_init(prz, sig, ecc_info);
+ ret = persistent_ram_post_init(prz, sig, ecc_info, flags);
if (ret)
goto err;
diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
index 244d242..4058bf9 100644
--- a/include/linux/pstore_ram.h
+++ b/include/linux/pstore_ram.h
@@ -24,6 +24,13 @@
#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
+ * PRZ_FLAG_NO_LOCK is used. For all other cases, locking is required.
+ */
+#define PRZ_FLAG_NO_LOCK BIT(0)
+
struct persistent_ram_buffer;
struct rs_control;
@@ -40,6 +47,7 @@
void *vaddr;
struct persistent_ram_buffer *buffer;
size_t buffer_size;
+ u32 flags;
raw_spinlock_t buffer_lock;
/* ECC correction */
@@ -56,7 +64,7 @@
struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
u32 sig, struct persistent_ram_ecc_info *ecc_info,
- unsigned int memtype);
+ unsigned int memtype, u32 flags);
void persistent_ram_free(struct persistent_ram_zone *prz);
void persistent_ram_zap(struct persistent_ram_zone *prz);