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ext4: fix prefetchw of NULL page

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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>
This commit is contained in:
Liu Xiang 2019-04-07 11:54:27 -04:00 committed by Theodore Ts'o
parent 742b06b562
commit d454a27384
1 changed files with 2 additions and 1 deletions
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3
fs/ext4/readpage.c
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@ -127,9 +127,10 @@ int ext4_mpage_readpages(struct address_space *mapping,
int fully_mapped = 1; int fully_mapped = 1;
unsigned first_hole = blocks_per_page; unsigned first_hole = blocks_per_page;
prefetchw(&page->flags);
if (pages) { if (pages) {
page = lru_to_page(pages); page = lru_to_page(pages);
prefetchw(&page->flags);
list_del(&page->lru); list_del(&page->lru);
if (add_to_page_cache_lru(page, mapping, page->index, if (add_to_page_cache_lru(page, mapping, page->index,
readahead_gfp_mask(mapping))) readahead_gfp_mask(mapping)))