linux-kernel - [PATCH 4.8 47/57] ext4: allow DAX writeback for hole punch

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Message-Id: <20161021091437.589319772@linuxfoundation.org>
Date:   Fri, 21 Oct 2016 11:18:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Jan Kara <jack@...e.cz>, Theodore Tso <tytso@....edu>
Subject: [PATCH 4.8 47/57] ext4: allow DAX writeback for hole punch

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

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

From: Ross Zwisler <ross.zwisler@...ux.intel.com>

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@...ux.intel.com>
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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)