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    SubjectRe: [PATCH] mm/hugetlb: Use compound page head in migrate_huge_page
    On Tue 29-05-12 08:48:00, Aneesh Kumar K.V wrote:
    > Michal Hocko <mhocko@suse.cz> writes:
    >
    > > On Mon 28-05-12 20:51:30, Aneesh Kumar K.V wrote:
    > >> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
    > >>
    > >> The change was introduced by "hugetlb: simplify migrate_huge_page() "
    > >>
    > >> We should use compound page head instead of tail pages in
    > >> migrate_huge_page().
    > >>
    > >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    > >> ---
    > >> mm/memory-failure.c | 4 ++--
    > >> 1 file changed, 2 insertions(+), 2 deletions(-)
    > >>
    > >> This is an important bug fix. If we want we can fold it with the not
    > >> yet merged upstream patch mentioned above in linux-next. The stack
    > >> trace for the crash is
    > >>
    > >> [ 75.337421] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
    > >> [ 75.338386] IP: [<ffffffff816b3f0f>] __mutex_lock_common+0xa1/0x350
    > >> [ 75.338386] PGD 1d700067 PUD 1d7dd067 PMD 0
    > >> [ 75.338386] Oops: 0002 [#1] SMP
    > >> [ 75.338386] CPU 1
    > >> [ 75.338386] Modules linked in:
    > >> ...
    > >> ...
    > >>
    > >> [ 75.338386] Call Trace:
    > >> [ 75.338386] [<ffffffff810ffc04>] ? try_to_unmap_file+0x38/0x51c
    > >> [ 75.338386] [<ffffffff810ffc04>] ? try_to_unmap_file+0x38/0x51c
    > >> [ 75.338386] [<ffffffff813b5f8b>] ? vsnprintf+0x83/0x421
    > >> [ 75.338386] [<ffffffff816b427d>] mutex_lock_nested+0x2a/0x31
    > >> [ 75.338386] [<ffffffff8110999b>] ? alloc_huge_page_node+0x1d/0x55
    > >> [ 75.338386] [<ffffffff810ffc04>] try_to_unmap_file+0x38/0x51c
    > >> [ 75.338386] [<ffffffff8110999b>] ? alloc_huge_page_node+0x1d/0x55
    > >> [ 75.338386] [<ffffffff810a06b9>] ? arch_local_irq_save+0x9/0xc
    > >> [ 75.338386] [<ffffffff816b5e3b>] ? _raw_spin_unlock+0x23/0x27
    > >> [ 75.338386] [<ffffffff81100839>] try_to_unmap+0x25/0x3c
    > >> [ 75.338386] [<ffffffff810641c2>] ? console_unlock+0x210/0x238
    > >> [ 75.338386] [<ffffffff811141e3>] migrate_huge_page+0x8d/0x178
    > >
    > > This should be part of the changelog.
    >
    > I was expecting the patch to be folded back to the existing patch in
    > -mm. That is the reason I added stack trace in the notes section so that
    > if we decided to keep it as a separate patch we can pull the stack trace
    > and add it to commit message.

    OK.
    --
    Michal Hocko
    SUSE Labs
    SUSE LINUX s.r.o.
    Lihovarska 1060/12
    190 00 Praha 9
    Czech Republic


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