[PATCH 4.7 37/45] ext4: allow DAX writeback for hole punch

From: Greg Kroah-Hartman
Date: Fri Oct 21 2016 - 05:20:13 EST


4.7-stable review patch. If anyone has any objections, please let me know.

------------------

From: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>

commit cca32b7eeb4ea24fa6596650e06279ad9130af98 upstream.

Currently when doing a DAX hole punch with ext4 we fail to do a writeback.
This is because the logic around filemap_write_and_wait_range() in
ext4_punch_hole() only looks for dirty page cache pages in the radix tree,
not for dirty DAX exceptional entries.

Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
fs/ext4/inode.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3892,7 +3892,7 @@ int ext4_update_disksize_before_punch(st
}

/*
- * ext4_punch_hole: punches a hole in a file by releaseing the blocks
+ * ext4_punch_hole: punches a hole in a file by releasing the blocks
* associated with the given offset and length
*
* @inode: File inode
@@ -3921,7 +3921,7 @@ int ext4_punch_hole(struct inode *inode,
* Write out all dirty pages to avoid race conditions
* Then release them.
*/
- if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+ if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
ret = filemap_write_and_wait_range(mapping, offset,
offset + length - 1);
if (ret)