On Sun, Sep 21, 2014 at 02:01:21AM +0100, Dimitri John Ledkov wrote:
> From: Shawn Landen <shawnland...@gmail.com>
>
> Bug-Debian: http://bugs.debian.org/656955
The bug seems old (2012) and agains 0.19. We've fixed a few unaligned
access bugs in the meantime. Can you please retest with 3.16?
> --- a/ctree.h
> +++ b/ctree.h
> @@ -19,6 +19,8 @@
> #ifndef __BTRFS__
> #define __BTRFS__
>
> +#include <stdint.h>
> +
> #if BTRFS_FLAT_INCLUDES
> #include "list.h"
> #include "kerncompat.h"
> @@ -1191,13 +1193,17 @@ struct btrfs_root {
> static inline u##bits btrfs_##name(const struct extent_buffer *eb) \
> { \
> const struct btrfs_header *h = (struct btrfs_header *)eb->data; \
> - return le##bits##_to_cpu(h->member); \
> + uint##bits##_t t; \
> + memcpy(&t, &h->member, sizeof(h->member)); \
> + return le##bits##_to_cpu(t); \
The change to memcpy is safe, the compiler is smart enough to not emit
any memcpy call for x86_64 and there's no change to the leXX_to_cpu
macros.
However, I'd like to check first if this is really necessary due to the
old version in the bugreport. I'd prefer using the u8/.../u64 types
instead of the stdint.h ones, for sake of consistency with the rest of
the codebase.
> --- a/volumes.c
> +++ b/volumes.c
> @@ -472,10 +472,11 @@ static int find_next_chunk(struct btrfs_root *root, u64
> objectid, u64 *offset)
> if (found_key.objectid != objectid)
> *offset = 0;
> else {
> + u64 t;
> chunk = btrfs_item_ptr(path->nodes[0], path->slots[0],
> struct btrfs_chunk);
> - *offset = found_key.offset +
> - btrfs_chunk_length(path->nodes[0], chunk);
> + t = found_key.offset +
> btrfs_chunk_length(path->nodes[0], chunk);
> + memcpy(offset, &t, sizeof(found_key.offset));
That's not enough, there are more direct assignments to *offset in that
function. The preferred way is to add 'put_unaligned' helper into
kerncompat.h and use it.
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