mm/memory.c: refactor insert_page to prepare for batched-lock insert

Add helper methods for vm_insert_page()/insert_page() to prepare for
vm_insert_pages(), which batch-inserts pages to reduce spinlock
operations when inserting multiple consecutive pages into the user page
table.

The intention of this patch-set is to reduce atomic ops for tcp zerocopy
receives, which normally hits the same spinlock multiple times
consecutively.

Signed-off-by: Arjun Roy <arjunroy@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: David Miller <davem@davemloft.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Link: http://lkml.kernel.org/r/20200128025958.43490-1-arjunroy.kdev@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index 19874d133a66fc01d7b7d5b0e6c1c923a70d9c0d..52a3303458cb6c1984cd05673f1ac165be2bf989 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1442,6 +1442,27 @@ pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
        return pte_alloc_map_lock(mm, pmd, addr, ptl);
 }
 
+static int validate_page_before_insert(struct page *page)
+{
+       if (PageAnon(page) || PageSlab(page) || page_has_type(page))
+               return -EINVAL;
+       flush_dcache_page(page);
+       return 0;
+}
+
+static int insert_page_into_pte_locked(struct mm_struct *mm, pte_t *pte,
+                       unsigned long addr, struct page *page, pgprot_t prot)
+{
+       if (!pte_none(*pte))
+               return -EBUSY;
+       /* Ok, finally just insert the thing.. */
+       get_page(page);
+       inc_mm_counter_fast(mm, mm_counter_file(page));
+       page_add_file_rmap(page, false);
+       set_pte_at(mm, addr, pte, mk_pte(page, prot));
+       return 0;
+}
+
 /*
  * This is the old fallback for page remapping.
  *
@@ -1457,26 +1478,14 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
        pte_t *pte;
        spinlock_t *ptl;
 
-       retval = -EINVAL;
-       if (PageAnon(page) || PageSlab(page) || page_has_type(page))
+       retval = validate_page_before_insert(page);
+       if (retval)
                goto out;
        retval = -ENOMEM;
-       flush_dcache_page(page);
        pte = get_locked_pte(mm, addr, &ptl);
        if (!pte)
                goto out;
-       retval = -EBUSY;
-       if (!pte_none(*pte))
-               goto out_unlock;
-
-       /* Ok, finally just insert the thing.. */
-       get_page(page);
-       inc_mm_counter_fast(mm, mm_counter_file(page));
-       page_add_file_rmap(page, false);
-       set_pte_at(mm, addr, pte, mk_pte(page, prot));
-
-       retval = 0;
-out_unlock:
+       retval = insert_page_into_pte_locked(mm, pte, addr, page, prot);
        pte_unmap_unlock(pte, ptl);
 out:
        return retval;