[PATCH v8 12/25] mm: Move end_index check out of readahead loop
From: Matthew Wilcox <willy@infradead.org>
Date: 2020-02-25 21:51:37
Also in:
linux-btrfs, linux-f2fs-devel, linux-fsdevel, linux-mm, linux-xfs, lkml, ocfs2-devel
Subsystem:
memory management, page cache, the rest · Maintainers:
Andrew Morton, Matthew Wilcox, Jan Kara, Linus Torvalds
From: "Matthew Wilcox (Oracle)" <willy@infradead.org> By reducing nr_to_read, we can eliminate this check from inside the loop. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: John Hubbard <jhubbard@nvidia.com> --- mm/readahead.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/mm/readahead.c b/mm/readahead.c
index d01531ef9f3c..a37b68f66233 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c@@ -167,8 +167,6 @@ void __do_page_cache_readahead(struct address_space *mapping, unsigned long lookahead_size) { struct inode *inode = mapping->host; - struct page *page; - unsigned long end_index; /* The last page we want to read */ LIST_HEAD(page_pool); loff_t isize = i_size_read(inode); gfp_t gfp_mask = readahead_gfp_mask(mapping);
@@ -178,22 +176,29 @@ void __do_page_cache_readahead(struct address_space *mapping, ._index = index, }; unsigned long i; + pgoff_t end_index; /* The last page we want to read */ if (isize == 0) return; - end_index = ((isize - 1) >> PAGE_SHIFT); + end_index = (isize - 1) >> PAGE_SHIFT; + if (index > end_index) + return; + /* Avoid wrapping to the beginning of the file */ + if (index + nr_to_read < index) + nr_to_read = ULONG_MAX - index + 1; + /* Don't read past the page containing the last byte of the file */ + if (index + nr_to_read >= end_index) + nr_to_read = end_index - index + 1; /* * Preallocate as many pages as we will need. */ for (i = 0; i < nr_to_read; i++) { - if (index + i > end_index) - break; + struct page *page = xa_load(&mapping->i_pages, index + i); BUG_ON(index + i != rac._index + rac._nr_pages); - page = xa_load(&mapping->i_pages, index + i); if (page && !xa_is_value(page)) { /* * Page already present? Kick off the current batch of
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2.25.0