[3.13.y.z extended stable] Patch "ext4: Fix hole punching for files with indirect blocks" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ext4: Fix hole punching for files with indirect blocks

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 61908b1c891135091b70a454fb047aaa0d5f1c31 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack at suse.cz>
Date: Thu, 26 Jun 2014 12:30:54 -0400
Subject: ext4: Fix hole punching for files with indirect blocks

commit a93cd4cf86466caa49cfe64607bea7f0bde3f916 upstream.

Hole punching code for files with indirect blocks wrongly computed
number of blocks which need to be cleared when traversing the indirect
block tree. That could result in punching more blocks than actually
requested and thus effectively cause a data loss. For example:

fallocate -n -p 10240000 4096

will punch the range 10240000 - 12632064 instead of the range 1024000 -
10244096. Fix the calculation.

Fixes: 8bad6fc813a3a5300f51369c39d315679fd88c72
Signed-off-by: Jan Kara <jack at suse.cz>
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/ext4/indirect.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 3b91d24..e6574d7 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -1318,16 +1318,24 @@ static int free_hole_blocks(handle_t *handle, struct inode *inode,
 		blk = *i_data;
 		if (level > 0) {
 			ext4_lblk_t first2;
+			ext4_lblk_t count2;
+
 			bh = sb_bread(inode->i_sb, le32_to_cpu(blk));
 			if (!bh) {
 				EXT4_ERROR_INODE_BLOCK(inode, le32_to_cpu(blk),
 						       "Read failure");
 				return -EIO;
 			}
-			first2 = (first > offset) ? first - offset : 0;
+			if (first > offset) {
+				first2 = first - offset;
+				count2 = count;
+			} else {
+				first2 = 0;
+				count2 = count - (offset - first);
+			}
 			ret = free_hole_blocks(handle, inode, bh,
 					       (__le32 *)bh->b_data, level - 1,
-					       first2, count - offset,
+					       first2, count2,
 					       inode->i_sb->s_blocksize >> 2);
 			if (ret) {
 				brelse(bh);
--
1.9.1