[PATCH 10/12] swap: add a swap_activate_fs_ops helper

[Christoph Hellwig <hch@lst.de>]

Add a helper abstracting away the low-level details of enabling
fs_ops-based swapping.  This prepares for taking swap_info_struct
private.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/nfs/file.c        | 4 +---
 fs/smb/client/file.c | 3 +--
 include/linux/swap.h | 5 +++++
 mm/swapfile.c        | 7 +++++++
 4 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 10ab2a923835..ce4d860c4e7a 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -588,7 +588,7 @@ int nfs_swap_activate(struct file *file, struct swap_info_struct *sis)
 	ret = rpc_clnt_swap_activate(clnt);
 	if (ret)
 		return ret;
-	ret = add_swap_extent(sis, sis->max, NULL, 0);
+	ret = swap_activate_fs_ops(sis);
 	if (ret < 0) {
 		rpc_clnt_swap_deactivate(clnt);
 		return ret;
@@ -596,8 +596,6 @@ int nfs_swap_activate(struct file *file, struct swap_info_struct *sis)
 
 	if (cl->rpc_ops->enable_swap)
 		cl->rpc_ops->enable_swap(inode);
-
-	sis->flags |= SWP_FS_OPS;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(nfs_swap_activate);
diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index e1bbc65ce7f3..e11065be1e64 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -3326,8 +3326,7 @@ int cifs_swap_activate(struct file *swap_file, struct swap_info_struct *sis)
 	 * from reading or writing the file
 	 */
 
-	sis->flags |= SWP_FS_OPS;
-	return add_swap_extent(sis, sis->max, NULL, 0);
+	return swap_activate_fs_ops(sis);
 }
 
 void cifs_swap_deactivate(struct file *file)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index b1cbb67ddd8e..916889738f08 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -406,6 +406,7 @@ extern void __meminit kswapd_stop(int nid);
 int add_swap_extent(struct swap_info_struct *sis, unsigned long nr_pages,
 		struct block_device *bdev, sector_t start_block);
 int generic_swap_activate(struct file *swap_file, struct swap_info_struct *sis);
+int swap_activate_fs_ops(struct swap_info_struct *sis);
 
 static inline unsigned long total_swapcache_pages(void)
 {
@@ -532,6 +533,10 @@ static inline int add_swap_extent(struct swap_info_struct *sis,
 {
 	return -EINVAL;
 }
+static inline int swap_activate_fs_ops(struct swap_info_struct *sis)
+{
+	return -EINVAL;
+}
 #endif /* CONFIG_SWAP */
 #ifdef CONFIG_MEMCG
 static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 2c9d2af736c4..26852c2ad36e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2757,6 +2757,13 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long nr_pages,
 }
 EXPORT_SYMBOL_GPL(add_swap_extent);
 
+int swap_activate_fs_ops(struct swap_info_struct *sis)
+{
+	sis->flags |= SWP_FS_OPS;
+	return add_swap_extent(sis, sis->max, NULL, 0);
+}
+EXPORT_SYMBOL_GPL(swap_activate_fs_ops);
+
 /*
  * A `swap extent' is a simple thing which maps a contiguous range of pages
  * onto a contiguous range of disk blocks.  A rbtree of swap extents is
-- 
2.53.0