[PATCH v9 2/3] fs: move drop_pagecache_sb() for others to use

[Shiyang Ruan <ruansy.fnst@fujitsu.com>]

xfs_notify_failure.c requires a method to invalidate all dax mappings.
drop_pagecache_sb() can do this but it is a static function and only
build with CONFIG_SYSCTL.  Now, move it to super.c and make it available
for others.  And use its second argument to choose which invalidate
method to use.

Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
---
 fs/drop_caches.c        | 35 ++-------------------------------
 fs/super.c              | 43 +++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h      |  1 +
 include/linux/pagemap.h |  1 +
 mm/truncate.c           | 20 +++++++++++++++++--
 5 files changed, 65 insertions(+), 35 deletions(-)

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index e619c31b6bd9..4c9281885077 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -15,38 +15,6 @@
 /* A global variable is a bit ugly, but it keeps the code simple */
 int sysctl_drop_caches;
 
-static void drop_pagecache_sb(struct super_block *sb, void *unused)
-{
-	struct inode *inode, *toput_inode = NULL;
-
-	spin_lock(&sb->s_inode_list_lock);
-	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
-		spin_lock(&inode->i_lock);
-		/*
-		 * We must skip inodes in unusual state. We may also skip
-		 * inodes without pages but we deliberately won't in case
-		 * we need to reschedule to avoid softlockups.
-		 */
-		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
-		    (mapping_empty(inode->i_mapping) && !need_resched())) {
-			spin_unlock(&inode->i_lock);
-			continue;
-		}
-		__iget(inode);
-		spin_unlock(&inode->i_lock);
-		spin_unlock(&sb->s_inode_list_lock);
-
-		invalidate_mapping_pages(inode->i_mapping, 0, -1);
-		iput(toput_inode);
-		toput_inode = inode;
-
-		cond_resched();
-		spin_lock(&sb->s_inode_list_lock);
-	}
-	spin_unlock(&sb->s_inode_list_lock);
-	iput(toput_inode);
-}
-
 int drop_caches_sysctl_handler(struct ctl_table *table, int write,
 		void *buffer, size_t *length, loff_t *ppos)
 {
@@ -59,7 +27,8 @@ int drop_caches_sysctl_handler(struct ctl_table *table, int write,
 		static int stfu;
 
 		if (sysctl_drop_caches & 1) {
-			iterate_supers(drop_pagecache_sb, NULL);
+			iterate_supers(super_drop_pagecache,
+				       invalidate_inode_pages);
 			count_vm_event(DROP_PAGECACHE);
 		}
 		if (sysctl_drop_caches & 2) {
diff --git a/fs/super.c b/fs/super.c
index 12c08cb20405..d788b73f93f0 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -36,6 +36,7 @@
 #include <linux/lockdep.h>
 #include <linux/user_namespace.h>
 #include <linux/fs_context.h>
+#include <linux/pagemap.h>
 #include <uapi/linux/mount.h>
 #include "internal.h"
 
@@ -678,6 +679,48 @@ void drop_super_exclusive(struct super_block *sb)
 }
 EXPORT_SYMBOL(drop_super_exclusive);
 
+/*
+ *	super_drop_pagecache - drop all page caches of a filesystem
+ *	@sb: superblock to invalidate
+ *	@arg: invalidate method, such as invalidate_inode_pages(),
+ *	        invalidate_inode_pages2()
+ *
+ *	Scans the inodes of a filesystem, drop all page caches.
+ */
+void super_drop_pagecache(struct super_block *sb, void *arg)
+{
+	struct inode *inode, *toput_inode = NULL;
+	int (*invalidator)(struct address_space *) = arg;
+
+	spin_lock(&sb->s_inode_list_lock);
+	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+		spin_lock(&inode->i_lock);
+		/*
+		 * We must skip inodes in unusual state. We may also skip
+		 * inodes without pages but we deliberately won't in case
+		 * we need to reschedule to avoid softlockups.
+		 */
+		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
+		    (mapping_empty(inode->i_mapping) && !need_resched())) {
+			spin_unlock(&inode->i_lock);
+			continue;
+		}
+		__iget(inode);
+		spin_unlock(&inode->i_lock);
+		spin_unlock(&sb->s_inode_list_lock);
+
+		invalidator(inode->i_mapping);
+		iput(toput_inode);
+		toput_inode = inode;
+
+		cond_resched();
+		spin_lock(&sb->s_inode_list_lock);
+	}
+	spin_unlock(&sb->s_inode_list_lock);
+	iput(toput_inode);
+}
+EXPORT_SYMBOL(super_drop_pagecache);
+
 static void __iterate_supers(void (*f)(struct super_block *))
 {
 	struct super_block *sb, *p = NULL;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c1769a2c5d70..b853632e76cd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3308,6 +3308,7 @@ extern struct super_block *get_super(struct block_device *);
 extern struct super_block *get_active_super(struct block_device *bdev);
 extern void drop_super(struct super_block *sb);
 extern void drop_super_exclusive(struct super_block *sb);
+void super_drop_pagecache(struct super_block *sb, void *unused);
 extern void iterate_supers(void (*)(struct super_block *, void *), void *);
 extern void iterate_supers_type(struct file_system_type *,
 			        void (*)(struct super_block *, void *), void *);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 29e1f9e76eb6..d0a180268baa 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -27,6 +27,7 @@ static inline void invalidate_remote_inode(struct inode *inode)
 	    S_ISLNK(inode->i_mode))
 		invalidate_mapping_pages(inode->i_mapping, 0, -1);
 }
+int invalidate_inode_pages(struct address_space *mapping);
 int invalidate_inode_pages2(struct address_space *mapping);
 int invalidate_inode_pages2_range(struct address_space *mapping,
 		pgoff_t start, pgoff_t end);
diff --git a/mm/truncate.c b/mm/truncate.c
index 7b4ea4c4a46b..131f2ab2d566 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -540,12 +540,13 @@ unsigned long invalidate_mapping_pagevec(struct address_space *mapping,
 }
 
 /**
- * invalidate_mapping_pages - Invalidate all clean, unlocked cache of one inode
+ * invalidate_mapping_pages - Invalidate range of clean, unlocked cache of one
+ *			      inode
  * @mapping: the address_space which holds the cache to invalidate
  * @start: the offset 'from' which to invalidate
  * @end: the offset 'to' which to invalidate (inclusive)
  *
- * This function removes pages that are clean, unmapped and unlocked,
+ * This function removes range of pages that are clean, unmapped and unlocked,
  * as well as shadow entries. It will not block on IO activity.
  *
  * If you want to remove all the pages of one inode, regardless of
@@ -560,6 +561,21 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
 }
 EXPORT_SYMBOL(invalidate_mapping_pages);
 
+/**
+ * invalidate_inode_pages - Invalidate all clean, unlocked cache of one inode
+ * @mapping: the address_space which holds the cache to invalidate
+ *
+ * This function removes all pages that are clean, unmapped and unlocked,
+ * as well as shadow entries. It will not block on IO activity.
+ */
+int invalidate_inode_pages(struct address_space *mapping)
+{
+	invalidate_mapping_pages(mapping, 0, -1);
+
+	return 0;
+}
+EXPORT_SYMBOL(invalidate_inode_pages);
+
 /*
  * This is like invalidate_inode_page(), except it ignores the page's
  * refcount.  We do this because invalidate_inode_pages2() needs stronger
-- 
2.39.1