Re: [PATCH v3 2/3] mm/vmalloc: respect passed gfp_mask when do preloading

[Andrew Morton]

On Fri, 18 Oct 2019 11:40:49 +0200 Uladzislau Rezki <urezki@xxxxxxxxx> wrote:

> > > alloc_vmap_area() is given a gfp_mask for the page allocator.
> > > Let's respect that mask and consider it even in the case when
> > > doing regular CPU preloading, i.e. where a context can sleep.
> > 
> > This is explaining what but it doesn't say why. I would go with
> > "
> > Allocation functions should comply with the given gfp_mask as much as
> > possible. The preallocation code in alloc_vmap_area doesn't follow that
> > pattern and it is using a hardcoded GFP_KERNEL. Although this doesn't
> > really make much difference because vmalloc is not GFP_NOWAIT compliant
> > in general (e.g. page table allocations are GFP_KERNEL) there is no
> > reason to spread that bad habit and it is good to fix the antipattern.
> > "
> I can go with that, agree. I am not sure if i need to update the patch
> and send v4. Or maybe Andrew can directly update it in his tree.
> 
> Andrew, should i send or can update?

I updated the changelog with Michal's words prior to committing.  You
were cc'ed :)


From: "Uladzislau Rezki (Sony)" <urezki@xxxxxxxxx>
Subject: mm/vmalloc: respect passed gfp_mask when doing preloading

Allocation functions should comply with the given gfp_mask as much as
possible.  The preallocation code in alloc_vmap_area doesn't follow that
pattern and it is using a hardcoded GFP_KERNEL.  Although this doesn't
really make much difference because vmalloc is not GFP_NOWAIT compliant in
general (e.g.  page table allocations are GFP_KERNEL) there is no reason
to spread that bad habit and it is good to fix the antipattern.

[mhocko@xxxxxxxx: rewrite changelog]
Link: http://lkml.kernel.org/r/20191016095438.12391-2-urezki@xxxxxxxxx
Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Daniel Wagner <dwagner@xxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@xxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/vmalloc.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/mm/vmalloc.c~mm-vmalloc-respect-passed-gfp_mask-when-do-preloading
+++ a/mm/vmalloc.c
@@ -1063,9 +1063,9 @@ static struct vmap_area *alloc_vmap_area
 		return ERR_PTR(-EBUSY);
 
 	might_sleep();
+	gfp_mask = gfp_mask & GFP_RECLAIM_MASK;
 
-	va = kmem_cache_alloc_node(vmap_area_cachep,
-			gfp_mask & GFP_RECLAIM_MASK, node);
+	va = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node);
 	if (unlikely(!va))
 		return ERR_PTR(-ENOMEM);
 
@@ -1073,7 +1073,7 @@ static struct vmap_area *alloc_vmap_area
 	 * Only scan the relevant parts containing pointers to other objects
 	 * to avoid false negatives.
 	 */
-	kmemleak_scan_area(&va->rb_node, SIZE_MAX, gfp_mask & GFP_RECLAIM_MASK);
+	kmemleak_scan_area(&va->rb_node, SIZE_MAX, gfp_mask);
 
 retry:
 	/*
@@ -1099,7 +1099,7 @@ retry:
 		 * Just proceed as it is. If needed "overflow" path
 		 * will refill the cache we allocate from.
 		 */
-		pva = kmem_cache_alloc_node(vmap_area_cachep, GFP_KERNEL, node);
+		pva = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node);
 
 	spin_lock(&vmap_area_lock);
 
_