On Tue, Jun 06, 2023 at 09:13:24AM +0200, Vlastimil Babka wrote: > > On 6/5/23 22:11, Lorenzo Stoakes wrote: > > In __vmalloc_area_node() we always warn_alloc() when an allocation > > performed by vm_area_alloc_pages() fails unless it was due to a pending > > fatal signal. > > > > However, huge page allocations instigated either by vmalloc_huge() or > > __vmalloc_node_range() (or a caller that invokes this like kvmalloc() or > > kvmalloc_node()) always falls back to order-0 allocations if the huge page > > allocation fails. > > > > This renders the warning useless and noisy, especially as all callers > > appear to be aware that this may fallback. This has already resulted in at > > least one bug report from a user who was confused by this (see link). > > > > Therefore, simply update the code to only output this warning for order-0 > > pages when no fatal signal is pending. > > > > Link: https://bugzilla.suse.com/show_bug.cgi?id=1211410 > > Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx> > > I think there are more reports of same thing from the btrfs context, that > appear to be a 6.3 regression > > https://bugzilla.kernel.org/show_bug.cgi?id=217466 > Link: https://lore.kernel.org/all/efa04d56-cd7f-6620-bca7-1df89f49bf4b@xxxxxxxxx/ > I had a look at that report. The btrfs complains due to the fact that a high-order page(1 << 9) can not be obtained. In the vmalloc code we do not fall to 0-order allocator if there is a request of getting a high-order. I provided a patch to fallback if a high-order. A reproducer, after applying the patch, started to get oppses in another places. IMO, we should fallback even for high-order requests. Because it is highly likely it can not be accomplished. Any thoughts? <snip> diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 31ff782d368b..7a06452f7807 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2957,14 +2957,18 @@ vm_area_alloc_pages(gfp_t gfp, int nid, page = alloc_pages(alloc_gfp, order); else page = alloc_pages_node(nid, alloc_gfp, order); + if (unlikely(!page)) { - if (!nofail) - break; + if (nofail) + alloc_gfp |= __GFP_NOFAIL; - /* fall back to the zero order allocations */ - alloc_gfp |= __GFP_NOFAIL; - order = 0; - continue; + /* Fall back to the zero order allocations. */ + if (order || nofail) { + order = 0; + continue; + } + + break; } /* <snip> -- Uladzislau Rezki
