mm/huge_memory.c: rework the function do_huge_pmd_numa_page() slightly

The current code that checks if migrating misplaced transhuge page is
needed is pretty hard to follow.  Rework it and add a comment to make
its logic more clear and improve readability.

Link: https://lkml.kernel.org/r/20210318122722.13135-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Thomas Hellstrm (Intel) <thomas_os@shipmail.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: yuleixzhang <yulei.kernel@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 01b96c6..23964ad 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1462,12 +1462,6 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
         */
        page_locked = trylock_page(page);
        target_nid = mpol_misplaced(page, vma, haddr);
-       if (target_nid == NUMA_NO_NODE) {
-               /* If the page was locked, there are no parallel migrations */
-               if (page_locked)
-                       goto clear_pmdnuma;
-       }
-
        /* Migration could have started since the pmd_trans_migrating check */
        if (!page_locked) {
                page_nid = NUMA_NO_NODE;
@@ -1476,6 +1470,11 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
                spin_unlock(vmf->ptl);
                put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE);
                goto out;
+       } else if (target_nid == NUMA_NO_NODE) {
+               /* There are no parallel migrations and page is in the right
+                * node. Clear the numa hinting info in this pmd.
+                */
+               goto clear_pmdnuma;
        }
 
        /*