[RFC 05/10] fs/dax: Refactor wait for dax idle page

[Alistair Popple <apopple@nvidia.com>]

A FS DAX page is considered idle when its refcount drops to one. This
is currently open-coded in all file systems supporting FS DAX. Move
the idle detection to a common function to make future changes easier.

Signed-off-by: Alistair Popple <apopple@nvidia.com>
---
 fs/ext4/inode.c     |  5 +----
 fs/fuse/dax.c       |  4 +---
 fs/xfs/xfs_file.c   |  4 +---
 include/linux/dax.h | 11 +++++++++++
 4 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 4ce35f1..e9cef7d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3868,10 +3868,7 @@ int ext4_break_layouts(struct inode *inode)
 		if (!page)
 			return 0;
 
-		error = ___wait_var_event(&page->_refcount,
-				atomic_read(&page->_refcount) == 1,
-				TASK_INTERRUPTIBLE, 0, 0,
-				ext4_wait_dax_page(inode));
+		error = dax_wait_page_idle(page, ext4_wait_dax_page, inode);
 	} while (error == 0);
 
 	return error;
diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index 23904a6..8a62483 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -676,9 +676,7 @@ static int __fuse_dax_break_layouts(struct inode *inode, bool *retry,
 		return 0;
 
 	*retry = true;
-	return ___wait_var_event(&page->_refcount,
-			atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
-			0, 0, fuse_wait_dax_page(inode));
+	return dax_wait_page_idle(page, fuse_wait_dax_page, inode);
 }
 
 /* dmap_end == 0 leads to unmapping of whole file */
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 2037002..099cd70 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -849,9 +849,7 @@ xfs_break_dax_layouts(
 		return 0;
 
 	*retry = true;
-	return ___wait_var_event(&page->_refcount,
-			atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
-			0, 0, xfs_wait_dax_page(inode));
+	return dax_wait_page_idle(page, xfs_wait_dax_page, inode);
 }
 
 int
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 22cd990..bced4d4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -212,6 +212,17 @@ int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
 int dax_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
 		const struct iomap_ops *ops);
 
+static inline int dax_wait_page_idle(struct page *page,
+				void (cb)(struct inode *),
+				struct inode *inode)
+{
+	int ret;
+
+	ret = ___wait_var_event(page, page_ref_count(page) == 1,
+				TASK_INTERRUPTIBLE, 0, 0, cb(inode));
+	return ret;
+}
+
 #if IS_ENABLED(CONFIG_DAX)
 int dax_read_lock(void);
 void dax_read_unlock(int id);
-- 
git-series 0.9.1