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 <apop...@nvidia.com>
Reviewed-by: Jan Kara <j...@suse.cz>
---
 fs/ext4/inode.c     | 5 +----
 fs/fuse/dax.c       | 4 +---
 fs/xfs/xfs_inode.c  | 4 +---
 include/linux/dax.h | 8 ++++++++
 4 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 4bae9cc..4737450 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3844,10 +3844,7 @@ 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 12ef91d..da50595 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_inode.c b/fs/xfs/xfs_inode.c
index f36091e..b5742aa 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -4243,9 +4243,7 @@ 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 9d3e332..773dfc4 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -213,6 +213,14 @@ 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)
+{
+       return ___wait_var_event(page, page_ref_count(page) == 1,
+                               TASK_INTERRUPTIBLE, 0, 0, cb(inode));
+}
+
 #if IS_ENABLED(CONFIG_DAX)
 int dax_read_lock(void);
 void dax_read_unlock(int id);
-- 
git-series 0.9.1

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