On Thu, 10 Jul 2014, Xiaoguang Wang wrote:
> Date: Thu, 10 Jul 2014 13:40:36 +0800
> From: Xiaoguang Wang <wangxg.fnst@xxxxxxxxxxxxxx>
> To: linux-ext4@xxxxxxxxxxxxxxx
> Cc: tytso@xxxxxxx, mlombard@xxxxxxxxxx,
> Xiaoguang Wang <wangxg.fnst@xxxxxxxxxxxxxx>
> Subject: [PATCH] ext4: fix wrong size computation in
> ext4_mb_normalize_request()
>
> As the member fe_len defined in struct ext4_free_extent is expressed as
> number of clusters, the variable "size" computation is wrong, we need to
> first translate it to block number, then to bytes.
>
> Signed-off-by: Xiaoguang Wang <wangxg.fnst@xxxxxxxxxxxxxx>
> ---
> fs/ext4/mballoc.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 7f72f50..9a543b5 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -3076,7 +3076,8 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
> size = 8 * 1024 * 1024;
> } else {
> start_off = (loff_t)ac->ac_o_ex.fe_logical << bsbits;
> - size = ac->ac_o_ex.fe_len << bsbits;
> + size = EXT4_C2B(EXT4_SB(ac->ac_sb),
> + ac->ac_o_ex.fe_len) << bsbits;
There is a patch out there up for more discussion which rewrites a
whole bunch of code in ext4_mb_normalize_request(). But more
importantly this fix, while correct is not going to change anything
since this condition will never be run.
Btw, I take back the correct part since it seems that there is a
a possibility of overflow. This should be better.
size = (loff_t)EXT4_C2B(EXT4_SB(ac->ac_sb),
ac->ac_o_ex.fe_len) << bsbits;
Thanks!
-Lukas
> }
> size = size >> bsbits;
> start = start_off >> bsbits;
>
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
