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page cache: Convert hole search to XArray

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The page cache offers the ability to search for a miss in the previous or
next N locations.  Rather than teach the XArray about the page cache's
definition of a miss, use xas_prev() and xas_next() to search the page
array.  This should be more efficient as it does not have to start the
lookup from the top for each index.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox
2017-11-21 14:07:06 -05:00
parent eb797a8ee0
commit 0d3f929666
4 changed files with 49 additions and 59 deletions
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4
mm/readahead.c
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@@ -336,7 +336,7 @@ static pgoff_t count_history_pages(struct address_space *mapping,
pgoff_t head;
rcu_read_lock();
head = page_cache_prev_hole(mapping, offset - 1, max);
head = page_cache_prev_miss(mapping, offset - 1, max);
rcu_read_unlock();
return offset - 1 - head;
@@ -425,7 +425,7 @@ ondemand_readahead(struct address_space *mapping,
pgoff_t start;
rcu_read_lock();
start = page_cache_next_hole(mapping, offset + 1, max_pages);
start = page_cache_next_miss(mapping, offset + 1, max_pages);
rcu_read_unlock();
if (!start || start - offset > max_pages)