[3.13.y.z extended stable] Patch "fs: make cont_expand_zero interruptible" has been added to staging queue

[Kamal Mostafa]

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

    fs: make cont_expand_zero interruptible

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 3.13.11.10.

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 343952a707425092ffbd60dfaef3f5faf4be4222 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka at redhat.com>
Date: Sun, 27 Jul 2014 13:00:41 -0400
Subject: fs: make cont_expand_zero interruptible

commit c2ca0fcd202863b14bd041a7fece2e789926c225 upstream.

This patch makes it possible to kill a process looping in
cont_expand_zero. A process may spend a lot of time in this function, so
it is desirable to be able to kill it.

It happened to me that I wanted to copy a piece data from the disk to a
file. By mistake, I used the "seek" parameter to dd instead of "skip". Due
to the "seek" parameter, dd attempted to extend the file and became stuck
doing so - the only possibility was to reset the machine or wait many
hours until the filesystem runs out of space and cont_expand_zero fails.
We need this patch to be able to terminate the process.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/buffer.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/buffer.c b/fs/buffer.c
index be90719..4252d82 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2313,6 +2313,11 @@ static int cont_expand_zero(struct file *file, struct address_space *mapping,
 		err = 0;

 		balance_dirty_pages_ratelimited(mapping);
+
+		if (unlikely(fatal_signal_pending(current))) {
+			err = -EINTR;
+			goto out;
+		}
 	}

 	/* page covers the boundary, find the boundary offset */
--
1.9.1