mm/fs: add hooks to support cleancache

This fourth patch of eight in this cleancache series provides the
core hooks in VFS for: initializing cleancache per filesystem;
capturing clean pages reclaimed by page cache; attempting to get
pages from cleancache before filesystem read; and ensuring coherency
between pagecache, disk, and cleancache.  Note that the placement
of these hooks was stable from 2.6.18 to 2.6.38; a minor semantic
change was required due to a patchset in 2.6.39.

All hooks become no-ops if CONFIG_CLEANCACHE is unset, or become
a check of a boolean global if CONFIG_CLEANCACHE is set but no
cleancache "backend" has claimed cleancache_ops.

Details and a FAQ can be found in Documentation/vm/cleancache.txt

[v8: minchan.kim@gmail.com: adapt to new remove_from_page_cache function]
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Reviewed-by: Jeremy Fitzhardinge <jeremy@goop.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik Van Riel <riel@redhat.com>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: Andreas Dilger <adilger@sun.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <joel.becker@oracle.com>
Cc: Nitin Gupta <ngupta@vflare.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/super.c b/fs/super.c
index 8a06881b1920..b383fa407740 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -31,6 +31,7 @@
 #include <linux/mutex.h>
 #include <linux/backing-dev.h>
 #include <linux/rculist_bl.h>
+#include <linux/cleancache.h>
 #include "internal.h"
 
 
@@ -112,6 +113,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
                 s->s_maxbytes = MAX_NON_LFS;
                 s->s_op = &default_op;
                 s->s_time_gran = 1000000000;
+                s->cleancache_poolid = -1;
         }
 out:
         return s;
@@ -177,6 +179,7 @@ void deactivate_locked_super(struct super_block *s)
 {
         struct file_system_type *fs = s->s_type;
         if (atomic_dec_and_test(&s->s_active)) {
+                cleancache_flush_fs(s);
                 fs->kill_sb(s);
                 /*
                  * We need to call rcu_barrier so all the delayed rcu free