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Patch "pstore/core: drop cmpxchg based updates" has been added to the 4.8-stable tree

PATCH [email protected] 1 participant 1 message Oct 26, 2016

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This is a note to let you know that I've just added the patch titled

pstore/core: drop cmpxchg based updates

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
pstore-core-drop-cmpxchg-based-updates.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From d5a9bf0b38d2ac85c9a693c7fb851f74fd2a2494 Mon Sep 17 00:00:00 2001

From: Sebastian Andrzej Siewior <[email protected]>
Date: Thu, 8 Sep 2016 13:48:06 +0200
Subject: pstore/core: drop cmpxchg based updates
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Sebastian Andrzej Siewior <[email protected]>

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 <[email protected]>
Cc Colin Cross <[email protected]>
Cc Kees Cook <[email protected]>
Cc Tony Luck <[email protected]>
Cc Rabin Vincent <[email protected]>
Tested-by Rabin Vincent <[email protected]>
Signed-off-by Sebastian Andrzej Siewior <[email protected]>
Reviewed-by Guenter Roeck <[email protected]>
[kees: remove "_locked" suffix since it's the only option now]
Signed-off-by Kees Cook <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 fs/pstore/ram_core.c |   43 ++-----------------------------------------
 1 file changed, 2 insertions(+), 41 deletions(-)
fs/pstore/ram_core.c +2 -41
@@ -47,43 +47,10 @@ static inline size_t buffer_start(struct
 	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;

@@ -103,7 +70,7 @@ static size_t buffer_start_add_locked(st
 }
 
 /* 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;

@@ -124,9 +91,6 @@ 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_a
 		return NULL;
 	}
 
-	buffer_start_add = buffer_start_add_locked;
-	buffer_size_add = buffer_size_add_locked;
-
 	if (memtype)
 		va = ioremap(start, size);
 	else

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/pstore-core-drop-cmpxchg-based-updates.patch queue-4.8/pstore-ramoops-fixup-driver-removal.patch