From 90efe9d4773eedf96d9e4ebb0193da7c6f09ca52 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Thu, 8 Sep 2016 13:48:06 +0200 Subject: [PATCH] pstore/core: drop cmpxchg based updates MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit d5a9bf0b38d2ac85c9a693c7fb851f74fd2a2494 upstream. I have here a FPGA behind PCIe which exports SRAM which I use for pstore. Now it seems that the FPGA no longer supports cmpxchg based updates and writes back 0xff…ff and returns the same. This leads to crash during crash rendering pstore useless. Since I doubt that there is much benefit from using cmpxchg() here, I am dropping this atomic access and use the spinlock based version. Cc: Anton Vorontsov Cc: Colin Cross Cc: Kees Cook Cc: Tony Luck Cc: Rabin Vincent Tested-by: Rabin Vincent Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Guenter Roeck [kees: remove "_locked" suffix since it's the only option now] Signed-off-by: Kees Cook Signed-off-by: Willy Tarreau --- fs/pstore/ram_core.c | 43 ++----------------------------------------- 1 file changed, 2 insertions(+), 41 deletions(-) diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c index 0b367ef7a7d6..ee3c6ec5348f 100644 --- a/fs/pstore/ram_core.c +++ b/fs/pstore/ram_core.c @@ -45,43 +45,10 @@ static inline size_t buffer_start(struct persistent_ram_zone *prz) return atomic_read(&prz->buffer->start); } -/* increase and wrap the start pointer, returning the old value */ -static size_t buffer_start_add_atomic(struct persistent_ram_zone *prz, size_t a) -{ - int old; - int new; - - do { - old = atomic_read(&prz->buffer->start); - new = old + a; - while (unlikely(new >= prz->buffer_size)) - new -= prz->buffer_size; - } while (atomic_cmpxchg(&prz->buffer->start, old, new) != old); - - return old; -} - -/* increase the size counter until it hits the max size */ -static void buffer_size_add_atomic(struct persistent_ram_zone *prz, size_t a) -{ - size_t old; - size_t new; - - if (atomic_read(&prz->buffer->size) == prz->buffer_size) - return; - - do { - old = atomic_read(&prz->buffer->size); - new = old + a; - if (new > prz->buffer_size) - new = prz->buffer_size; - } 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) +static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a) { int old; int new; @@ -101,7 +68,7 @@ static size_t buffer_start_add_locked(struct persistent_ram_zone *prz, size_t a) } /* increase the size counter until it hits the max size */ -static void buffer_size_add_locked(struct persistent_ram_zone *prz, size_t a) +static void buffer_size_add(struct persistent_ram_zone *prz, size_t a) { size_t old; size_t new; @@ -122,9 +89,6 @@ exit: raw_spin_unlock_irqrestore(&buffer_lock, flags); } -static size_t (*buffer_start_add)(struct persistent_ram_zone *, size_t) = buffer_start_add_atomic; -static void (*buffer_size_add)(struct persistent_ram_zone *, size_t) = buffer_size_add_atomic; - static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz, uint8_t *data, size_t len, uint8_t *ecc) { @@ -426,9 +390,6 @@ static void *persistent_ram_iomap(phys_addr_t start, size_t size, return NULL; } - buffer_start_add = buffer_start_add_locked; - buffer_size_add = buffer_size_add_locked; - if (memtype) va = ioremap(start, size); else -- 2.20.1