mm/sparse: fix preinited section_mem_map clobbering on failure path

sparse_init_nid() is careful to leave alone every section whose vmemmap
has already been set up by sparse_vmemmap_init_nid_early(); it only clears
section_mem_map for the rest:

        if (!preinited_vmemmap_section(ms))
                ms->section_mem_map = 0;

A leftover line after that conditional block

        ms->section_mem_map = 0;

was supposed to be deleted but was missed in the failure path, causing the
field to be overwritten for all sections when memory allocation fails,
effectively destroying the pre-initialization check.

Drop the stray assignment so that preinited sections retain their
already valid state.

Those pre-inited sections (HugeTLB pages) are not activated.  However,
such failures are extremely rare, so I don't see any major userspace
issues.

Link: https://lore.kernel.org/20260331113724.2080833-1-songmuchun@bytedance.com
Fixes: d65917c42373 ("mm/sparse: allow for alternate vmemmap section init at boot")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed by: Donet Tom <donettom@linux.ibm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Frank van der Linden <fvdl@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/sparse.c b/mm/sparse.c
index 007fd52c621e80c2174fe754a05abdd543103449..effdac6b0ab13c8f905bed6ff257267f51bfbe0f 100644 (file)
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -403,7 +403,6 @@ failed:
                ms = __nr_to_section(pnum);
                if (!preinited_vmemmap_section(ms))
                        ms->section_mem_map = 0;
-               ms->section_mem_map = 0;
        }
 }