On 3/25/20 1:07 PM, Baoquan He wrote:
On 03/25/20 at 03:06pm, Baoquan He wrote:
On 03/25/20 at 08:49am, Aneesh Kumar K.V wrote:

  mm/sparse.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/mm/sparse.c b/mm/sparse.c
index aadb7298dcef..3012d1f3771a 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -781,6 +781,8 @@ static void section_deactivate(unsigned long pfn, unsigned 
long nr_pages,
                        ms->usage = NULL;
                memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
+               /* Mark the section invalid */
+               ms->section_mem_map &= ~SECTION_HAS_MEM_MAP;

Not sure if we should add checking in valid_section() or pfn_valid(),
e.g check ms->usage validation too. Otherwise, this fix looks good to

With SPASEMEM_VMEMAP enabled, we should do validation check on ms->usage
before checking any subsection is valid. Since now we do have case
in which ms->usage is released, people still try to check it.

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index f0a2c184eb9a..d79bd938852e 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1306,6 +1306,8 @@ static inline int pfn_section_valid(struct mem_section 
*ms, unsigned long pfn)
        int idx = subsection_map_index(pfn);
+ if (!ms->usage)
+               return 0;
        return test_bit(idx, ms->usage->subsection_map);

We always check for section valid, before we check if pfn_section_valid().

static inline int pfn_valid(unsigned long pfn)

        struct mem_section *ms;

        if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
                return 0;
        ms = __nr_to_section(pfn_to_section_nr(pfn));
        if (!valid_section(ms))
                return 0;
         * Traditionally early sections always returned pfn_valid() for
         * the entire section-sized span.
        return early_section(ms) || pfn_section_valid(ms, pfn);

IMHO adding that if (!ms->usage) is redundant.


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