On Mon, Jun 15, 2015 at 2:41 PM, <[email protected]> wrote:
> From: Jeff Mahoney <[email protected]>
>
> It's possible, though unexpected, to pass unaligned offsets and lengths
> to btrfs_issue_discard. We then shift the offset/length values to sector
> units. If an unaligned offset has been passed, it will result in the
> entire sector being discarded, possibly losing data. An unaligned
> length is safe but we'll end up returning an inaccurate number of
> discarded bytes.
>
> This patch aligns the offset to the 512B boundary, adjusts the length,
> and warns, since we shouldn't be discarding on an offset that isn't
> aligned with our sector size.
>
> Signed-off-by: Jeff Mahoney <[email protected]>
Reviewed-by: Filipe Manana <[email protected]>
Tested-by: Filipe Manana <[email protected]>
> ---
> fs/btrfs/extent-tree.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index da1145d..cf9cefd 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -1888,12 +1888,21 @@ static int btrfs_issue_discard(struct block_device
> *bdev, u64 start, u64 len,
> u64 *discarded_bytes)
> {
> int ret = 0;
> + u64 aligned_start = ALIGN(start, 1 << 9);
>
> - *discarded_bytes = 0;
> - ret = blkdev_issue_discard(bdev, start >> 9, len >> 9, GFP_NOFS, 0);
> - if (!ret)
> - *discarded_bytes = len;
> + if (WARN_ON(start != aligned_start)) {
> + len -= aligned_start - start;
> + len = round_down(len, 1 << 9);
> + start = aligned_start;
> + }
>
> + *discarded_bytes = 0;
> + if (len) {
> + ret = blkdev_issue_discard(bdev, start >> 9, len >> 9,
> + GFP_NOFS, 0);
> + if (!ret)
> + *discarded_bytes = len;
> + }
> return ret;
> }
>
> --
> 2.4.3
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Filipe David Manana,
"Reasonable men adapt themselves to the world.
Unreasonable men adapt the world to themselves.
That's why all progress depends on unreasonable men."
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
