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    SubjectRe: [PATCH 4.14 023/159] mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y
    On 01/10/18 at 02:16pm, Kirill A. Shutemov wrote:
    > On Wed, Jan 10, 2018 at 03:08:04AM +0000, Dave Young wrote:
    > > On Tue, Jan 09, 2018 at 12:05:52PM +0300, Kirill A. Shutemov wrote:
    > > > On Tue, Jan 09, 2018 at 03:24:40PM +0800, Dave Young wrote:
    > > > > On 01/09/18 at 01:41pm, Baoquan He wrote:
    > > > > > On 01/09/18 at 09:09am, Dave Young wrote:
    > > > > >
    > > > > > > As for the macro name, VMCOREINFO_SYMBOL_ARRAY sounds better.
    > > >
    > > > Yep, that's better.
    > > >
    > > > > > I still think using vmcoreinfo_append_str is better. Unless we replace
    > > > > > all array variables with the newly added macro.
    > > > > >
    > > > > > vmcoreinfo_append_str("SYMBOL(mem_section)=%lx\n",
    > > > > > (unsigned long)mem_section);
    > > > >
    > > > > I have no strong opinion, either change all array uses or just introduce
    > > > > the macro and start to use it from now on if we have similar array
    > > > > symbols.
    > > >
    > > > Do you need some action on my side or will you folks take care about this?
    > >
    > > I think Baoquan was suggesting to update all array users in current
    > > code, if you can check every VMCOREINFO_SYMBOL and update all the arrays
    > > he will be happy. But if can not do it easily I'm fine with a
    > > VMCOREINFO_SYMBOL_ARRAY changes only now, we kdump people can do it
    > > later as well.
    >
    > It seems it's the only array we have there. swapper_pg_dir is a potential
    > candidate, but it's 'unsigned long' on arm.
    >
    > Below it patch with corrected macro name.
    >
    > Please, consider applying.
    >
    > From 70f3a84b97f2de98d1364f7b10b7a42a1d8e9968 Mon Sep 17 00:00:00 2001
    > From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
    > Date: Tue, 9 Jan 2018 02:55:47 +0300
    > Subject: [PATCH] kdump: Write a correct address of mem_section into vmcoreinfo
    >
    > Depending on configuration mem_section can now be an array or a pointer
    > to an array allocated dynamically. In most cases, we can continue to refer
    > to it as 'mem_section' regardless of what it is.
    >
    > But there's one exception: '&mem_section' means "address of the array" if
    > mem_section is an array, but if mem_section is a pointer, it would mean
    > "address of the pointer".
    >
    > We've stepped onto this in kdump code. VMCOREINFO_SYMBOL(mem_section)
    > writes down address of pointer into vmcoreinfo, not array as we wanted.
    >
    > Let's introduce VMCOREINFO_SYMBOL_ARRAY() that would handle the
    > situation correctly for both cases.
    >
    > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    > Fixes: 83e3c48729d9 ("mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y")

    Ack it, thanks.

    Acked-by: Baoquan He <bhe@redhat.com>

    > ---
    > include/linux/crash_core.h | 2 ++
    > kernel/crash_core.c | 2 +-
    > 2 files changed, 3 insertions(+), 1 deletion(-)
    >
    > diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
    > index 06097ef30449..b511f6d24b42 100644
    > --- a/include/linux/crash_core.h
    > +++ b/include/linux/crash_core.h
    > @@ -42,6 +42,8 @@ phys_addr_t paddr_vmcoreinfo_note(void);
    > vmcoreinfo_append_str("PAGESIZE=%ld\n", value)
    > #define VMCOREINFO_SYMBOL(name) \
    > vmcoreinfo_append_str("SYMBOL(%s)=%lx\n", #name, (unsigned long)&name)
    > +#define VMCOREINFO_SYMBOL_ARRAY(name) \
    > + vmcoreinfo_append_str("SYMBOL(%s)=%lx\n", #name, (unsigned long)name)
    > #define VMCOREINFO_SIZE(name) \
    > vmcoreinfo_append_str("SIZE(%s)=%lu\n", #name, \
    > (unsigned long)sizeof(name))
    > diff --git a/kernel/crash_core.c b/kernel/crash_core.c
    > index b3663896278e..4f63597c824d 100644
    > --- a/kernel/crash_core.c
    > +++ b/kernel/crash_core.c
    > @@ -410,7 +410,7 @@ static int __init crash_save_vmcoreinfo_init(void)
    > VMCOREINFO_SYMBOL(contig_page_data);
    > #endif
    > #ifdef CONFIG_SPARSEMEM
    > - VMCOREINFO_SYMBOL(mem_section);
    > + VMCOREINFO_SYMBOL_ARRAY(mem_section);
    > VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS);
    > VMCOREINFO_STRUCT_SIZE(mem_section);
    > VMCOREINFO_OFFSET(mem_section, section_mem_map);
    > --
    > Kirill A. Shutemov

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