mm: move readahead nr_pages check into read_pages

Simplify the callers by moving the check for nr_pages and the BUG_ON
into read_pages().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Chao Yu <yuchao0@huawei.com>
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: Miklos Szeredi <mszeredi@redhat.com>
Link: http://lkml.kernel.org/r/20200414150233.24495-5-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/readahead.c b/mm/readahead.c
index 61b15b6..9fcd4e3 100644 (file)
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -119,6 +119,9 @@ static void read_pages(struct address_space *mapping, struct file *filp,
        struct blk_plug plug;
        unsigned page_idx;
 
+       if (!nr_pages)
+               return;
+
        blk_start_plug(&plug);
 
        if (mapping->a_ops->readpages) {
@@ -138,6 +141,8 @@ static void read_pages(struct address_space *mapping, struct file *filp,
 
 out:
        blk_finish_plug(&plug);
+
+       BUG_ON(!list_empty(pages));
 }
 
 /*
@@ -180,8 +185,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
                         * contiguous pages before continuing with the next
                         * batch.
                         */
-                       if (nr_pages)
-                               read_pages(mapping, filp, &page_pool, nr_pages,
+                       read_pages(mapping, filp, &page_pool, nr_pages,
                                                gfp_mask);
                        nr_pages = 0;
                        continue;
@@ -202,9 +206,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
         * uptodate then the caller will launch readpage again, and
         * will then handle the error.
         */
-       if (nr_pages)
-               read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask);
-       BUG_ON(!list_empty(&page_pool));
+       read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask);
 }
 
 /*