From d454a27384f6eb05904a59d1607461b7ad312aa9 Mon Sep 17 00:00:00 2001
From: Liu Xiang <liu.xiang6@zte.com.cn>
Date: Sun, 7 Apr 2019 11:54:27 -0400
Subject: [PATCH] ext4: fix prefetchw of NULL page
In ext4_mpage_readpages(), if the parameter pages is not NULL, another
parameter page is NULL. At the first time prefetchw(&page->flags)
works on NULL. From second time, prefetchw(&page->flags) always works on
the last consumed page. This might do little improvment for handling
current page. So prefetchw() should be called while the page pointer
has just been updated.
Signed-off-by: Liu Xiang <liu.xiang6@zte.com.cn>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
fs/ext4/readpage.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index 3adadf4618253..9386b0446afb3 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -127,9 +127,10 @@ int ext4_mpage_readpages(struct address_space *mapping,
int fully_mapped = 1;
unsigned first_hole = blocks_per_page;
- prefetchw(&page->flags);
if (pages) {
page = lru_to_page(pages);
+
+ prefetchw(&page->flags);
list_del(&page->lru);
if (add_to_page_cache_lru(page, mapping, page->index,
readahead_gfp_mask(mapping)))
--
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