On Mon 09-01-17 14:42:10, Michal Hocko wrote:
> On Mon 09-01-17 14:04:21, Vlastimil Babka wrote:
[...]
> Now that you have opened this I have noticed that the code is wrong
> here because GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK would overwrite
> the removed GFP_FS.
Blee, it wouldn't because ~GFP_RECLAIM_MASK will not contain neither
GFP_FS nor GFP_IO. So all is good here.
> I guess it would be better and less error prone
> to move the current_gfp_context part into the direct reclaim entry -
> do_try_to_free_pages - and put the comment like this
well, after more thinking about we, should probably keep it where it is.
If for nothing else try_to_free_mem_cgroup_pages has a tracepoint which
prints the gfp mask so we should use the filtered one. So let's just
scratch this follow up fix.
> ---
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 4ea6b610f20e..df7975185f11 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2756,6 +2756,13 @@ static unsigned long do_try_to_free_pages(struct
> zonelist *zonelist,
> int initial_priority = sc->priority;
> unsigned long total_scanned = 0;
> unsigned long writeback_threshold;
> +
> + /*
> + * Make sure that the gfp context properly handles scope gfp mask.
> + * This might weaken the reclaim context (e.g. make it GFP_NOFS or
> + * GFP_NOIO).
> + */
> + sc->gfp_mask = current_gfp_context(sc->gfp_mask);
> retry:
> delayacct_freepages_start();
>
> @@ -2949,7 +2956,7 @@ unsigned long try_to_free_pages(struct zonelist
> *zonelist, int order,
> unsigned long nr_reclaimed;
> struct scan_control sc = {
> .nr_to_reclaim = SWAP_CLUSTER_MAX,
> - .gfp_mask = (gfp_mask = current_gfp_context(gfp_mask)),
> + .gfp_mask = gfp_mask,
> .reclaim_idx = gfp_zone(gfp_mask),
> .order = order,
> .nodemask = nodemask,
> @@ -3029,8 +3036,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct
> mem_cgroup *memcg,
> int nid;
> struct scan_control sc = {
> .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
> - .gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) |
> - (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
> + .gfp_mask = GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK,
> .reclaim_idx = MAX_NR_ZONES - 1,
> .target_mem_cgroup = memcg,
> .priority = DEF_PRIORITY,
> @@ -3723,7 +3729,7 @@ static int __node_reclaim(struct pglist_data *pgdat,
> gfp_t gfp_mask, unsigned in
> int classzone_idx = gfp_zone(gfp_mask);
> struct scan_control sc = {
> .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
> - .gfp_mask = (gfp_mask = current_gfp_context(gfp_mask)),
> + .gfp_mask = gfp_mask,
> .order = order,
> .priority = NODE_RECLAIM_PRIORITY,
> .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
> --
> Michal Hocko
> SUSE Labs
--
Michal Hocko
SUSE Labs
