[3.13.y.z extended stable] Patch "ext4: grab missed write_count for EXT4_IOC_SWAP_BOOT" 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: grab missed write_count for EXT4_IOC_SWAP_BOOT

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 3.13.11.11.

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 375cf789a4aab6bd30ae3bfc160ff81afee21116 Mon Sep 17 00:00:00 2001
From: Dmitry Monakhov <dmonakhov at openvz.org>
Date: Fri, 3 Oct 2014 12:47:23 -0400
Subject: ext4: grab missed write_count for EXT4_IOC_SWAP_BOOT

commit 3e67cfad22230ebed85c56cbe413876f33fea82b upstream.

Otherwise this provokes complain like follows:
WARNING: CPU: 12 PID: 5795 at fs/ext4/ext4_jbd2.c:48 ext4_journal_check_start+0x4e/0xa0()
Modules linked in: brd iTCO_wdt lpc_ich mfd_core igb ptp dm_mirror dm_region_hash dm_log dm_mod
CPU: 12 PID: 5795 Comm: python Not tainted 3.17.0-rc2-00175-gae5344f #158
Hardware name: Intel Corporation W2600CR/W2600CR, BIOS SE5C600.86B.99.99.x028.061320111235 06/13/2011
 0000000000000030 ffff8808116cfd28 ffffffff815c7dfc 0000000000000030
 0000000000000000 ffff8808116cfd68 ffffffff8106ce8c ffff8808116cfdc8
 ffff880813b16000 ffff880806ad6ae8 ffffffff81202008 0000000000000000
Call Trace:
 [<ffffffff815c7dfc>] dump_stack+0x51/0x6d
 [<ffffffff8106ce8c>] warn_slowpath_common+0x8c/0xc0
 [<ffffffff81202008>] ? ext4_ioctl+0x9e8/0xeb0
 [<ffffffff8106ceda>] warn_slowpath_null+0x1a/0x20
 [<ffffffff8122867e>] ext4_journal_check_start+0x4e/0xa0
 [<ffffffff81228c10>] __ext4_journal_start_sb+0x90/0x110
 [<ffffffff81202008>] ext4_ioctl+0x9e8/0xeb0
 [<ffffffff8107b0bd>] ? ptrace_stop+0x24d/0x2f0
 [<ffffffff81088530>] ? alloc_pid+0x480/0x480
 [<ffffffff8107b1f2>] ? ptrace_do_notify+0x92/0xb0
 [<ffffffff81186545>] do_vfs_ioctl+0x4e5/0x550
 [<ffffffff815cdbcb>] ? _raw_spin_unlock_irq+0x2b/0x40
 [<ffffffff81186603>] SyS_ioctl+0x53/0x80
 [<ffffffff815ce2ce>] tracesys+0xd0/0xd5

Reviewed-by: Jan Kara <jack at suse.cz>
Signed-off-by: Dmitry Monakhov <dmonakhov at openvz.org>
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/ext4/ioctl.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 4a5fe55..2c3541b 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -548,9 +548,17 @@ group_add_out:
 	}

 	case EXT4_IOC_SWAP_BOOT:
+	{
+		int err;
 		if (!(filp->f_mode & FMODE_WRITE))
 			return -EBADF;
-		return swap_inode_boot_loader(sb, inode);
+		err = mnt_want_write_file(filp);
+		if (err)
+			return err;
+		err = swap_inode_boot_loader(sb, inode);
+		mnt_drop_write_file(filp);
+		return err;
+	}

 	case EXT4_IOC_RESIZE_FS: {
 		ext4_fsblk_t n_blocks_count;
--
1.9.1