mm: create new mm/swap.h header file

Patch series "MM changes to improve swap-over-NFS support".

Assorted improvements for swap-via-filesystem.

This is a resend of these patches, rebased on current HEAD.  The only
substantial changes is that swap_dirty_folio has replaced
swap_set_page_dirty.

Currently swap-via-fs (SWP_FS_OPS) doesn't work for any filesystem.  It
has previously worked for NFS but that broke a few releases back.  This
series changes to use a new ->swap_rw rather than ->readpage and
->direct_IO.  It also makes other improvements.

There is a companion series already in linux-next which fixes various
issues with NFS.  Once both series land, a final patch is needed which
changes NFS over to use ->swap_rw.


This patch (of 10):

Many functions declared in include/linux/swap.h are only used within mm/

Create a new "mm/swap.h" and move some of these declarations there.
Remove the redundant 'extern' from the function declarations.

[akpm@linux-foundation.org: mm/memory-failure.c needs mm/swap.h]
Link: https://lkml.kernel.org/r/164859751830.29473.5309689752169286816.stgit@noble.brown
Link: https://lkml.kernel.org/r/164859778120.29473.11725907882296224053.stgit@noble.brown
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: David Howells <dhowells@redhat.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/mm/page_io.c b/mm/page_io.c
index 89fbf3cae30f..4b359e59bfdc 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -26,6 +26,7 @@
 #include <linux/uio.h>
 #include <linux/sched/task.h>
 #include <linux/delayacct.h>
+#include "swap.h"
 
 void end_swap_bio_write(struct bio *bio)
 {