----- Original Message -----
> From: Lachlan McIlroy <lmcilroy@xxxxxxxxxx>
>
> In the case where we are allocating for a non-extent file,
> we must limit the groups we allocate from to those below
> 2^32 blocks, and ext4_mb_regular_allocator() attempts to
> do this initially by putting a cap on ngroups for the
> subsequent search loop.
>
> However, the initial target group comes in from the
> allocation context (ac), and it may already be beyond
> the artificially limited ngroups. In this case,
> the limit
>
> if (group == ngroups)
> group = 0;
>
> at the top of the loop is never true, and the loop will
> run away.
>
> Catch this case inside the loop and reset the search to
> start at group 0.
>
> [sandeen@xxxxxxxxxx: add commit msg & comments]
>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
>
> p.s. I suppose this limit could go after the assignment
> from ac->ac_g_ex.fe_group, depending on your sense
> of style...
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index ee6614b..f54baee 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -1994,7 +1994,11 @@ repeat:
> group = ac->ac_g_ex.fe_group;
>
> for (i = 0; i < ngroups; group++, i++) {
> - if (group == ngroups)
> + /*
> + * Artificially restricted ngroups for non-extent
> + * files makes group > ngroups possible on first loop.
> + */
> + if (group >= ngroups)
> group = 0;
>
> /* This now checks without needing the buddy page */
>
> --
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>
Thanks for following through with this Eric. Looks good to me.
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