linux-kernel - [v5 PATCH 2/2] mm: swap: add comment for swap_vma

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Date:   Fri,  4 Jan 2019 03:27:53 +0800
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     ying.huang@...el.com, tim.c.chen@...el.com, minchan@...nel.org,
        daniel.m.jordan@...cle.com, akpm@...ux-foundation.org
Cc:     yang.shi@...ux.alibaba.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [v5 PATCH 2/2] mm: swap: add comment for swap_vma_readahead

swap_vma_readahead()'s comment is missed, just add it.

Cc: Huang Ying <ying.huang@...el.com>
Cc: Tim Chen <tim.c.chen@...el.com>
Cc: Minchan Kim <minchan@...nel.org>
Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>
---
v5: Fixed the comments per Ying Huang

 mm/swap_state.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 78d500e..c8730d7 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -523,7 +523,7 @@ static unsigned long swapin_nr_pages(unsigned long offset)
  * This has been extended to use the NUMA policies from the mm triggering
  * the readahead.
  *
- * Caller must hold down_read on the vma->vm_mm if vmf->vma is not NULL.
+ * Caller must hold read mmap_sem if vmf->vma is not NULL.
  */
 struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
 				struct vm_fault *vmf)
@@ -698,6 +698,20 @@ static void swap_ra_info(struct vm_fault *vmf,
 	pte_unmap(orig_pte);
 }
 
+/**
+ * swap_vma_readahead - swap in pages in hope we need them soon
+ * @entry: swap entry of this memory
+ * @gfp_mask: memory allocation flags
+ * @vmf: fault information
+ *
+ * Returns the struct page for entry and addr, after queueing swapin.
+ *
+ * Primitive swap readahead code. We simply read in a few pages whoes
+ * virtual addresses are around the fault address in the same vma.
+ *
+ * Caller must hold read mmap_sem if vmf->vma is not NULL.
+ *
+ */
 static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
 				       struct vm_fault *vmf)
 {
-- 
1.8.3.1