[PATCH 2/7] pstore: locking: dont lock unless caller asks to

From: Joel Fernandes
Date: Sat Oct 08 2016 - 01:29:29 EST


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@xxxxxxxxxx>
---
fs/pstore/ram.c | 10 +++++-----
fs/pstore/ram_core.c | 27 ++++++++++++++++-----------
include/linux/pstore_ram.h | 2 +-
3 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index f1219af..751197d 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, 1);
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, 1);
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, 1);
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, 1);
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, 1);

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..c4722f0 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)
+ 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)
+ 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)
+ 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)
+ 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, 1);

- start = buffer_start_add(prz, c);
+ start = buffer_start_add(prz, c, 1);

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..782af68 100644
--- a/include/linux/pstore_ram.h
+++ b/include/linux/pstore_ram.h
@@ -61,7 +61,7 @@ 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