[RFC PATCH 2/4] lmb: Tighten up the code in lmb_add_region_flags()

[Sughosh Ganu]

On Tue, 30 Jul 2024 at 20:10, Simon Glass <sjg at chromium.org> wrote:
>
> This function has more special cases than it needs. Simplify it to
> reduce code size and complexity.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
>  lib/lmb.c | 57 +++++++++++++++++++------------------------------------
>  1 file changed, 19 insertions(+), 38 deletions(-)
>
> diff --git a/lib/lmb.c b/lib/lmb.c
> index c11ce308c5b..83b060a2f4d 100644
> --- a/lib/lmb.c
> +++ b/lib/lmb.c
> @@ -396,14 +396,6 @@ static long lmb_add_region_flags(struct alist *lmb_rgn_lst, phys_addr_t base,
>         if (alist_err(lmb_rgn_lst))
>                 return -1;
>
> -       if (alist_empty(lmb_rgn_lst)) {
> -               rgn[0].base = base;
> -               rgn[0].size = size;
> -               rgn[0].flags = flags;
> -               lmb_rgn_lst->count = 1;
> -               return 0;
> -       }
> -
>         /* First try and coalesce this LMB with another. */
>         for (i = 0; i < lmb_rgn_lst->count; i++) {
>                 phys_addr_t rgnbase = rgn[i].base;
> @@ -448,50 +440,39 @@ static long lmb_add_region_flags(struct alist *lmb_rgn_lst, phys_addr_t base,
>                 }
>         }
>
> -       if (i < lmb_rgn_lst->count - 1 &&
> -           rgn[i].flags == rgn[i + 1].flags) {
> -               if (lmb_regions_adjacent(lmb_rgn_lst, i, i + 1)) {
> -                       lmb_coalesce_regions(lmb_rgn_lst, i, i + 1);
> -                       coalesced++;
> -               } else if (lmb_regions_overlap(lmb_rgn_lst, i, i + 1)) {
> -                       /* fix overlapping area */
> -                       lmb_fix_over_lap_regions(lmb_rgn_lst, i, i + 1);
> -                       coalesced++;
> +       if (lmb_rgn_lst->count && i < lmb_rgn_lst->count - 1) {
> +               rgn = lmb_rgn_lst->data;
> +               if (rgn[i].flags == rgn[i + 1].flags) {
> +                       if (lmb_regions_adjacent(lmb_rgn_lst, i, i + 1)) {
> +                               lmb_coalesce_regions(lmb_rgn_lst, i, i + 1);
> +                               coalesced++;
> +                       } else if (lmb_regions_overlap(lmb_rgn_lst, i, i + 1)) {
> +                               /* fix overlapping area */
> +                               lmb_fix_over_lap_regions(lmb_rgn_lst, i, i + 1);
> +                               coalesced++;
> +                       }
>                 }
>         }
>
>         if (coalesced)
>                 return coalesced;
>
> -       if (alist_full(lmb_rgn_lst)) {
> -               if (!alist_expand_by(lmb_rgn_lst, lmb_rgn_lst->alloc * 2))
> -                       return -1;
> -               else
> -                       rgn = lmb_rgn_lst->data;
> -       }
> +       if (!alist_add_placeholder(lmb_rgn_lst))
> +               return -1;
> +       rgn = lmb_rgn_lst->data;

I think the above should have a check for alist_full(), and then add
to the list if full. Else we simply go on adding to the list on every
new node that gets added.

>
>         /* Couldn't coalesce the LMB, so add it to the sorted table. */
>         for (i = lmb_rgn_lst->count - 1; i >= 0; i--) {
> -               if (base < rgn[i].base) {
> -                       rgn[i + 1].base = rgn[i].base;
> -                       rgn[i + 1].size = rgn[i].size;
> -                       rgn[i + 1].flags = rgn[i].flags;
> +               if (i && base < rgn[i - 1].base) {
> +                       rgn[i] = rgn[i - 1];
>                 } else {
> -                       rgn[i + 1].base = base;
> -                       rgn[i + 1].size = size;
> -                       rgn[i + 1].flags = flags;
> +                       rgn[i].base = base;
> +                       rgn[i].size = size;
> +                       rgn[i].flags = flags;
>                         break;
>                 }
>         }

With the logic that you put above, should the loop not have 'i'
initialised to lmb_rgn_lst-count? I mean

for (i = lmb_rgn_lst->count; i >= 0; i--)

Else we are overwriting one region?

-sughosh

>
> -       if (base < rgn[0].base) {
> -               rgn[0].base = base;
> -               rgn[0].size = size;
> -               rgn[0].flags = flags;
> -       }
> -
> -       lmb_rgn_lst->count++;
> -
>         return 0;
>  }
>
> --
> 2.34.1
>