diff options
| author | Mike Kravetz <mike.kravetz@oracle.com> | 2019-01-09 02:23:36 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-01-09 04:15:11 +0300 |
| commit | ddeaab32a89f04b7e2a2df8771583a719c4ac6b7 (patch) | |
| tree | faa31cf72190bc24e3041c924da8e7d58d8c99f0 /mm/userfaultfd.c | |
| parent | e7c58097793ef15d58fadf190ee58738fbf447cd (diff) | |
| download | linux-ddeaab32a89f04b7e2a2df8771583a719c4ac6b7.tar.xz | |
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/userfaultfd.c')
| -rw-r--r-- | mm/userfaultfd.c | 11 |
1 files changed, 2 insertions, 9 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 065c1ce191c4..d59b5a73dfb3 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -267,14 +267,10 @@ retry: VM_BUG_ON(dst_addr & ~huge_page_mask(h)); /* - * Serialize via i_mmap_rwsem and hugetlb_fault_mutex. - * i_mmap_rwsem ensures the dst_pte remains valid even - * in the case of shared pmds. fault mutex prevents - * races with other faulting threads. + * Serialize via hugetlb_fault_mutex */ - mapping = dst_vma->vm_file->f_mapping; - i_mmap_lock_read(mapping); idx = linear_page_index(dst_vma, dst_addr); + mapping = dst_vma->vm_file->f_mapping; hash = hugetlb_fault_mutex_hash(h, dst_mm, dst_vma, mapping, idx, dst_addr); mutex_lock(&hugetlb_fault_mutex_table[hash]); @@ -283,7 +279,6 @@ retry: dst_pte = huge_pte_alloc(dst_mm, dst_addr, huge_page_size(h)); if (!dst_pte) { mutex_unlock(&hugetlb_fault_mutex_table[hash]); - i_mmap_unlock_read(mapping); goto out_unlock; } @@ -291,7 +286,6 @@ retry: dst_pteval = huge_ptep_get(dst_pte); if (!huge_pte_none(dst_pteval)) { mutex_unlock(&hugetlb_fault_mutex_table[hash]); - i_mmap_unlock_read(mapping); goto out_unlock; } @@ -299,7 +293,6 @@ retry: dst_addr, src_addr, &page); mutex_unlock(&hugetlb_fault_mutex_table[hash]); - i_mmap_unlock_read(mapping); vm_alloc_shared = vm_shared; cond_resched(); |