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authorLi Xinhai <lixinhai.lxh@gmail.com>2021-02-24 12:04:49 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-02-24 13:38:30 -0800
commitee8ab1903e3d912d8f10bedbf96c3b6a1c8cbede (patch)
tree336052046bb2efbce056b12f6a9f2be525af6f16 /mm/rmap.c
parentdbf53f7597be11ffc18b16444a1ffc7d7b76746e (diff)
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mm: rmap: explicitly reset vma->anon_vma in unlink_anon_vmas()
In case the vma will continue to be used after unlink its relevant anon_vma, we need to reset the vma->anon_vma pointer to NULL. So, later when fault happen within this vma again, a new anon_vma will be prepared. By this way, the vma will only be checked for reverse mapping of pages which been fault in after the unlink_anon_vmas call. Currently, the mremap with MREMAP_DONTUNMAP scenario will continue use the vma after moved its page table entries to a new vma. For other scenarios, the vma itself will be freed after call unlink_anon_vmas. Link: https://lkml.kernel.org/r/20210119075126.3513154-1-lixinhai.lxh@gmail.com Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Brian Geffon <bgeffon@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Lokesh Gidra <lokeshgidra@google.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/rmap.c')
-rw-r--r--mm/rmap.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 5ebf16fae4b9..e26ae119a131 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -413,8 +413,15 @@ void unlink_anon_vmas(struct vm_area_struct *vma)
list_del(&avc->same_vma);
anon_vma_chain_free(avc);
}
- if (vma->anon_vma)
+ if (vma->anon_vma) {
vma->anon_vma->degree--;
+
+ /*
+ * vma would still be needed after unlink, and anon_vma will be prepared
+ * when handle fault.
+ */
+ vma->anon_vma = NULL;
+ }
unlock_anon_vma_root(root);
/*