[PATCH 02/11] persistent_ram: Fix buffer size clamping during writes

Anton Vorontsov
2012-05-12T00:18:47Z

This is a longstanding bug, almost unnoticeable when calling
persistent_ram_write() for small buffers.

But when called for large data buffers, the write routine behaves
incorrectly, as the size may never update: instead of clamping
the size to the maximum buffer size, buffer_size_add_clamp() returns
an error (which is never checked by the write routine, btw).

To fix this, we now use buffer_size_add() that actually clamps the
size to the max value.

Also remove buffer_size_add_clamp(), it is no longer needed.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
drivers/staging/android/persistent_ram.c | 19 +------------------
1 file changed, 1 insertion(+), 18 deletions(-)

diff --git a/drivers/staging/android/persistent_ram.c b/drivers/staging/android/persistent_ram.c
index 12444fd..13a12bc 100644
--- a/drivers/staging/android/persistent_ram.c
+++ b/drivers/staging/android/persistent_ram.c
@@ -79,23 +79,6 @@ static inline void buffer_size_add(struct persistent_ram_zone *prz, size_t a)
} while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);
}

-/* increase the size counter, retuning an error if it hits the max size */
-static inline ssize_t buffer_size_add_clamp(struct persistent_ram_zone *prz,
- size_t a)
-{
- size_t old;
- size_t new;
-
- do {
- old = atomic_read(&prz->buffer->size);
- new = old + a;
- if (new > prz->buffer_size)
- return -ENOMEM;
- } while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);
-
- return 0;
-}
-
static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
uint8_t *data, size_t len, uint8_t *ecc)
{
@@ -300,7 +283,7 @@ int notrace persistent_ram_write(struct persistent_ram_zone *prz,
c = prz->buffer_size;
}

- buffer_size_add_clamp(prz, c);
+ buffer_size_add(prz, c);

start = buffer_start_add(prz, c);

--
1.7.9.2