On Wed, 18 Apr 2018, Christopher Lameter wrote:
> Mikulas Patoka wants to ensure that no fallback to lower order happens. I > think __GFP_NORETRY should work correctly in that case too and not fall > back. > > > > Allocating at a smaller order is a retry operation and should not > be attempted. > > If the caller does not want retries then respect that. > > GFP_NORETRY allows callers to ensure that only maximum order > allocations are attempted. > > Signed-off-by: Christoph Lameter <[email protected]> > > Index: linux/mm/slub.c > =================================================================== > --- linux.orig/mm/slub.c > +++ linux/mm/slub.c > @@ -1598,7 +1598,7 @@ static struct page *allocate_slab(struct > alloc_gfp = (alloc_gfp | __GFP_NOMEMALLOC) & > ~(__GFP_RECLAIM|__GFP_NOFAIL); > > page = alloc_slab_page(s, alloc_gfp, node, oo); > - if (unlikely(!page)) { > + if (unlikely(!page) && !(flags & __GFP_NORETRY)) { > oo = s->min; > alloc_gfp = flags; > /* No, this would hit NULL pointer dereference if page is NULL and __GFP_NORETRY is set. You want this: --- mm/slub.c | 2 ++ 1 file changed, 2 insertions(+) Index: linux-2.6/mm/slub.c =================================================================== --- linux-2.6.orig/mm/slub.c 2018-04-17 20:58:23.000000000 +0200 +++ linux-2.6/mm/slub.c 2018-04-18 17:04:01.000000000 +0200 @@ -1599,6 +1599,8 @@ static struct page *allocate_slab(struct page = alloc_slab_page(s, alloc_gfp, node, oo); if (unlikely(!page)) { + if (flags & __GFP_NORETRY) + goto out; oo = s->min; alloc_gfp = flags; /* -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
