| Message ID | 20170109134210.GI7495@dhcp22.suse.cz (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
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
On 01/09/2017 02:42 PM, Michal Hocko wrote: > On Mon 09-01-17 14:04:21, Vlastimil Babka wrote: > [...] >>> +static inline unsigned int memalloc_nofs_save(void) >>> +{ >>> + unsigned int flags = current->flags & PF_MEMALLOC_NOFS; >>> + current->flags |= PF_MEMALLOC_NOFS; >> >> So this is not new, as same goes for memalloc_noio_save, but I've >> noticed that e.g. exit_signal() does tsk->flags |= PF_EXITING; >> So is it possible that there's a r-m-w hazard here? > > exit_signals operates on current and all task_struct::flags should be > used only on the current. > [...] Ah, good to know. > >>> @@ -3029,7 +3029,7 @@ 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 = (gfp_mask & GFP_RECLAIM_MASK) | >>> + .gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) | >> >> So this function didn't do memalloc_noio_flags() before? Is it a bug >> that should be fixed separately or at least mentioned? Because that >> looks like a functional change... > > We didn't need it. Kmem charges are opt-in and current all of them > support GFP_IO. The LRU pages are not charged in NOIO context either. > We need it now because there will be callers to charge GFP_KERNEL while > being inside the NOFS scope. I see. > 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. 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 Agree with your "So let's just scratch this follow up fix in the next e-mail. So for the unchanged patch. Acked-by: Vlastimil Babka <vbabka@suse.cz> -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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),