mm: move end_index check out of readahead loop (b0f31d78) · Commits · 戴 / test

By reducing nr_to_read, we can eliminate this check from inside the loop. Signed-off-by:

Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Reviewed-by:

John Hubbard <jhubbard@nvidia.com> Reviewed-by:

William Kucharski <william.kucharski@oracle.com> Cc: Chao Yu <yuchao0@huawei.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Dave Chinner <dchinner@redhat.com> Cc: Eric Biggers <ebiggers@google.com> Cc: Gao Xiang <gaoxiang25@huawei.com> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: Joseph Qi <joseph.qi@linux.alibaba.com> Cc: Junxiao Bi <junxiao.bi@oracle.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com> Cc: Miklos Szeredi <mszeredi@redhat.com> Link: http://lkml.kernel.org/r/20200414150233.24495-13-willy@infradead.org Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/readahead.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -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 +176,26 @@ 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;
		/* Don't read past the page containing the last byte of the file */
		if (nr_to_read > end_index - 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

Admin message