linux-kernel - Re: [PATCH 2/4] mm/vmalloc: add support for __GFP

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Date:   Tue, 26 Oct 2021 13:29:00 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     NeilBrown <neilb@...e.de>
Cc:     linux-mm@...ck.org, Dave Chinner <david@...morbit.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@...radead.org>,
        Uladzislau Rezki <urezki@...il.com>,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Ilya Dryomov <idryomov@...il.com>,
        Jeff Layton <jlayton@...nel.org>
Subject: Re: [PATCH 2/4] mm/vmalloc: add support for __GFP_NOFAIL

On Tue 26-10-21 21:30:52, Neil Brown wrote:
> On Tue, 26 Oct 2021, Michal Hocko wrote:
> > On Tue 26-10-21 09:59:36, Neil Brown wrote:
> > > On Tue, 26 Oct 2021, Michal Hocko wrote:
> > [...]
> > > > @@ -3032,6 +3036,10 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
> > > >  		warn_alloc(gfp_mask, NULL,
> > > >  			"vmalloc error: size %lu, vm_struct allocation failed",
> > > >  			real_size);
> > > > +		if (gfp_mask & __GFP_NOFAIL) {
> > > > +			schedule_timeout_uninterruptible(1);
> > > > +			goto again;
> > > > +		}
> > > 
> > > Shouldn't the retry happen *before* the warning?
> > 
> > I've done it after to catch the "depleted or fragmented" vmalloc space.
> > This is not related to the memory available and therefore it won't be
> > handled by the oom killer. The error message shouldn't imply the vmalloc
> > allocation failure IMHO but I am open to suggestions.
> 
> The word "failed" does seem to imply what you don't want it to imply...
> 
> I guess it is reasonable to have this warning, but maybe add " -- retrying"
> if __GFP_NOFAIL.

I do not have a strong opinion on that. I can surely do
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 602649919a9d..3489928fafa2 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3033,10 +3033,11 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 				  VM_UNINITIALIZED | vm_flags, start, end, node,
 				  gfp_mask, caller);
 	if (!area) {
+		bool nofail = gfp_mask & __GFP_NOFAIL;
 		warn_alloc(gfp_mask, NULL,
-			"vmalloc error: size %lu, vm_struct allocation failed",
-			real_size);
-		if (gfp_mask & __GFP_NOFAIL) {
+			"vmalloc error: size %lu, vm_struct allocation failed%s",
+			real_size, (nofail) ? ". Retrying." : "");
+		if (nofail) {
 			schedule_timeout_uninterruptible(1);
 			goto again;
 		}
-- 
Michal Hocko
SUSE Labs