Hey Jeff,
On Fri, Oct 25, 2013 at 02:52:44PM +0800, Jeff Liu wrote:
> From: Jie Liu <jeff.liu@xxxxxxxxxx>
>
> At xfs_iext_add(), if extent(s) are being appended to the last page in
> the indirection array and the new extent(s) don't fit in the page, the
> number of extents(erp->er_extcount) in a new allocated entry should be
> the minimum value between count and XFS_LINEAR_EXTS, instead of count.
>
> For now, there is no existing test case can demonstrates a problem with
> the er_extcount being set incorrectly here, but it obviously like a bug.
>
> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
> ---
> v2: * Declare count to uint as it will be decreased to 0 and XFS_LINEAR_EXTS
> can be uint because of a case in the macro.
> * Convert MIN() to min().
> * Revise the commits log to indicate there is no existing test case can
> reflect this issue for future tracking up.
>
> fs/xfs/xfs_inode_fork.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
> index 22c9837..cfee14a 100644
> --- a/fs/xfs/xfs_inode_fork.c
> +++ b/fs/xfs/xfs_inode_fork.c
> @@ -1021,15 +1021,14 @@ xfs_iext_add(
> * the next index needed in the indirection array.
> */
> else {
> - int count = ext_diff;
> + uint count = ext_diff;
>
> while (count) {
> erp = xfs_iext_irec_new(ifp, erp_idx);
> - erp->er_extcount = count;
> - count -= MIN(count, (int)XFS_LINEAR_EXTS);
> - if (count) {
> + erp->er_extcount = min(count, XFS_LINEAR_EXTS);
> + count -= erp->er_extcount;
> + if (count)
> erp_idx++;
> - }
> }
> }
> }
Really nice find. So there is potential for incorrect er_extcount and
er_extoff when adding > 256 extents to the end of the indirection array. You'd
think we'd be seeing some side effects since xfs_iext_idx_to_irec uses them in
it's binary search.
Reviewed-by: Ben Myers <bpm@xxxxxxx>
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