[PATCH] ext4: Drop mapped buffer_head check during page_mkwrite

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Inorder to check whether the buffer_heads are mapped we need
to hold page lock. Otherwise a reclaim can cleanup the attached
buffer_heads. Instead of taking page lock and check whether
buffer_heads are mapped we let the write_begin/write_end callback
does the equivalent. It does have a performance impact in that we
are doing more work if we the buffer_heads are already mapped.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/ext4/inode.c |    6 ------
 1 files changed, 0 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f9c642b..d40b97d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5281,12 +5281,6 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	else
 		len = PAGE_CACHE_SIZE;
 
-	if (page_has_buffers(page)) {
-		/* return if we have all the buffers mapped */
-		if (!walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
-				       ext4_bh_unmapped))
-			goto out_unlock;
-	}
 	/*
 	 * OK, we need to fill the hole... Do write_begin write_end
 	 * to do block allocation/reservation.We are not holding
-- 
1.6.4.1.174.g32f4c