On Mon, Sep 24, 2012 at 12:38:07PM +0800, Wang Sheng-Hui wrote:
> Check range early to avoid further check/compute in case
> of range error.
>
> Signed-off-by: Wang Sheng-Hui <shh...@gmail.com>
> ---
> fs/btrfs/extent_io.c | 16 ++++++++--------
> 1 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 4c87847..9250cf5 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -4643,6 +4643,14 @@ int map_private_extent_buffer(struct extent_buffer
> *eb, unsigned long start,
> unsigned long end_i = (start_offset + start + min_len - 1) >>
> PAGE_CACHE_SHIFT;
>
> + if (start + min_len > eb->len) {
> + printk(KERN_ERR "btrfs bad mapping eb start %llu len %lu, "
> + "wanted %lu %lu\n", (unsigned long long)eb->start,
> + eb->len, start, min_len);
> + WARN_ON(1);
> + return -EINVAL;
> + }
> +
> if (i != end_i)
> return -EINVAL;
4665 unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
4666 unsigned long end_i = (start_offset + start + min_len - 1) >>
4667 PAGE_CACHE_SHIFT;
so the check above effectively verifies that
min_len - 1 < PAGE_CACHE_SIZE
AND
is within the same page
The other check
if (start + min_len > eb->len) {
looks if the requested data do not lie out of the bounds of the extent
buffer, where min_len is filled with sizeof(something).
So, both the checks look for corrupted metadata, I don't see the need to
swap them.
david
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