From: Josef Bacik <josef@redhat.com>
Date: Fri, 4 Mar 2011 20:46:53 +0000 (-0500)
Subject: Btrfs: add a comment explaining what btrfs_cont_expand does
X-Git-Tag: v3.0~816^2~72
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=695a0d0da09e75c4475bbb303def159023ef72ca;p=platform%2Fkernel%2Flinux-amlogic.git

Btrfs: add a comment explaining what btrfs_cont_expand does

Everytime I have to deal with btrfs_cont_expand I stare at it for 20 minutes
trying to remember what exactly it does and why the hell we need it.  So add a
comment to save future-Josef some time.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
---

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 64d57e0..888dbdb 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3557,6 +3557,12 @@ out:
 	return ret;
 }
 
+/*
+ * This function puts in dummy file extents for the area we're creating a hole
+ * for.  So if we are truncating this file to a larger size we need to insert
+ * these file extents so that btrfs_get_extent will return a EXTENT_MAP_HOLE for
+ * the range between oldsize and size
+ */
 int btrfs_cont_expand(struct inode *inode, loff_t oldsize, loff_t size)
 {
 	struct btrfs_trans_handle *trans;