On Thu, Mar 2, 2023 at 3:28 PM Luis Chamberlain <mcgrof@xxxxxxxxxx> wrote:
>
> i915_gem requires huge folios to be split when swapping.
> However we have check for usage of writepages() to ensure
> it used only for swap purposes later. Avoid the splits if
> we're not being called for reclaim, even if they should in
> theory not happen.
>
> This makes the conditions easier to follow on shem_writepage().
>
> Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Nice cleanup.
Reviewed-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
> ---
> mm/shmem.c | 24 ++++++++++++------------
> 1 file changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 2b9ff585a553..a5a6da51087e 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1340,6 +1340,18 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
> swp_entry_t swap;
> pgoff_t index;
>
> + /*
> + * Our capabilities prevent regular writeback or sync from ever calling
> + * shmem_writepage; but a stacking filesystem might use ->writepage of
> + * its underlying filesystem, in which case tmpfs should write out to
> + * swap only in response to memory pressure, and not for the writeback
> + * threads or sync.
> + */
> + if (!wbc->for_reclaim) {
> + WARN_ON_ONCE(1); /* Still happens? Tell us about it! */
> + goto redirty;
> + }
> +
> /*
> * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "always" or
> * "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages,
> @@ -1360,18 +1372,6 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
> if (!total_swap_pages)
> goto redirty;
>
> - /*
> - * Our capabilities prevent regular writeback or sync from ever calling
> - * shmem_writepage; but a stacking filesystem might use ->writepage of
> - * its underlying filesystem, in which case tmpfs should write out to
> - * swap only in response to memory pressure, and not for the writeback
> - * threads or sync.
> - */
> - if (!wbc->for_reclaim) {
> - WARN_ON_ONCE(1); /* Still happens? Tell us about it! */
> - goto redirty;
> - }
> -
> /*
> * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
> * value into swapfile.c, the only way we can correctly account for a
> --
> 2.39.1
>
