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authorMike Kravetz <mike.kravetz@oracle.com>2019-01-08 15:23:36 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-08 17:15:11 -0800
commitddeaab32a89f04b7e2a2df8771583a719c4ac6b7 (patch)
treefaa31cf72190bc24e3041c924da8e7d58d8c99f0 /mm/migrate.c
parente7c58097793ef15d58fadf190ee58738fbf447cd (diff)
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hugetlbfs: revert "use i_mmap_rwsem for more pmd sharing synchronization"
This reverts b43a9990055958e70347c56f90ea2ae32c67334c The reverted commit caused issues with migration and poisoning of anon huge pages. The LTP move_pages12 test will cause an "unable to handle kernel NULL pointer" BUG would occur with stack similar to: RIP: 0010:down_write+0x1b/0x40 Call Trace: migrate_pages+0x81f/0xb90 __ia32_compat_sys_migrate_pages+0x190/0x190 do_move_pages_to_node.isra.53.part.54+0x2a/0x50 kernel_move_pages+0x566/0x7b0 __x64_sys_move_pages+0x24/0x30 do_syscall_64+0x5b/0x180 entry_SYSCALL_64_after_hwframe+0x44/0xa9 The purpose of the reverted patch was to fix some long existing races with huge pmd sharing. It used i_mmap_rwsem for this purpose with the idea that this could also be used to address truncate/page fault races with another patch. Further analysis has determined that i_mmap_rwsem can not be used to address all these hugetlbfs synchronization issues. Therefore, revert this patch while working an another approach to the underlying issues. Link: http://lkml.kernel.org/r/20190103235452.29335-2-mike.kravetz@oracle.com Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Reported-by: Jan Stancek <jstancek@redhat.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Prakash Sangappa <prakash.sangappa@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/migrate.c')
-rw-r--r--mm/migrate.c13
1 files changed, 1 insertions, 12 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index ccf8966caf6f..a16b15090df3 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1324,19 +1324,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
goto put_anon;
if (page_mapped(hpage)) {
- struct address_space *mapping = page_mapping(hpage);
-
- /*
- * try_to_unmap could potentially call huge_pmd_unshare.
- * Because of this, take semaphore in write mode here and
- * set TTU_RMAP_LOCKED to let lower levels know we have
- * taken the lock.
- */
- i_mmap_lock_write(mapping);
try_to_unmap(hpage,
- TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS|
- TTU_RMAP_LOCKED);
- i_mmap_unlock_write(mapping);
+ TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
page_was_mapped = 1;
}