readahead: record mmap read-around states in file_ra_state

Mmap read-around now shares the same code style and data structure with
readahead code.

This also removes do_page_cache_readahead().  Its last user, mmap
read-around, has been changed to call ra_submit().

The no-readahead-if-congested logic is dumped by the way.  Users will be
pretty sensitive about the slow loading of executables.  So it's
unfavorable to disabled mmap read-around on a congested queue.

[akpm@linux-foundation.org: coding-style fixes]
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 5c0c6518f341..734891d0663d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1488,13 +1488,15 @@ static void do_sync_mmap_readahead(struct vm_area_struct *vma,
         if (ra->mmap_miss > MMAP_LOTSAMISS)
                 return;
 
+        /*
+         * mmap read-around
+         */
         ra_pages = max_sane_readahead(ra->ra_pages);
         if (ra_pages) {
-                pgoff_t start = 0;
-
-                if (offset > ra_pages / 2)
-                        start = offset - ra_pages / 2;
-                do_page_cache_readahead(mapping, file, start, ra_pages);
+                ra->start = max_t(long, 0, offset - ra_pages/2);
+                ra->size = ra_pages;
+                ra->async_size = 0;
+                ra_submit(ra, mapping, file);
         }
 }