* Wei Yang <richard.weiyang@xxxxxxxxx> [241010 21:27]:
>
> Related fix has been posted, but not merged yet.
>
> lkml.kernel.org/r/20240626160631.3636515-1-Liam.Howlett@xxxxxxxxxx
>
> May drop this one.
Yes, thanks. This can be dropped in favour of the other commit.
>
> On Tue, Sep 24, 2024 at 12:39:54PM +0000, Wei Yang wrote:
> >We got an rare case when mas_node_count() would fail even there is
> >enough memory.
> >
> >The reason is the maple_alloc grows downward. And when hit a full
> >maple_alloc, the max_req would be 0. This leads to mt_alloc_bulk()
> >return 0, which means failure here.
> >
> >For example, here is the test code:
> >
> > expect = MAPLE_ALLOC_SLOTS + 1;
> > mas_node_count(&ms, expect);
> > pr_info("expect %d allocated %lu\n", expect, mas_allocated(&ms));
> > expect = MAPLE_ALLOC_SLOTS * 2 + 2;
> > mas_node_count(&ms, expect);
> > pr_info("expect %d allocated %lu\n", expect, mas_allocated(&ms));
> >
> >We will get the following output, which shows we fail to allocate the
> >required number of nodes.
> >
> > expect 31 allocated 31
> > expect 62 allocated 61
> >
> >The straight forward way to fix it is go down one level more.
> >
> >Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
> >CC: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> >CC: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
> >---
> > lib/maple_tree.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> >diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> >index 1cbc5f7ca40d..dd33d0793dd1 100644
> >--- a/lib/maple_tree.c
> >+++ b/lib/maple_tree.c
> >@@ -1253,8 +1253,10 @@ static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
> > }
> >
> > node = mas->alloc;
> >- while (requested) {
> >+ for (; requested; node = node->slot[0]) {
> > max_req = MAPLE_ALLOC_SLOTS - node->node_count;
> >+ if (unlikely(!max_req))
> >+ continue;
> > slots = (void **)&node->slot[node->node_count];
> > max_req = min(requested, max_req);
> > count = mt_alloc_bulk(gfp, max_req, slots);
> >@@ -1268,7 +1270,6 @@ static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
> >
> > node->node_count += count;
> > allocated += count;
> >- node = node->slot[0];
> > requested -= count;
> > }
> > mas->alloc->total = allocated;
> >--
> >2.34.1
>
> --
> Wei Yang
> Help you, Help me
>
