[3.16.y-ckt stable] Patch "ext4: avoid deadlocks in the writeback path by using sb_getblk_gfp" has been added to staging queue

[Luis Henriques]

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

    ext4: avoid deadlocks in the writeback path by using sb_getblk_gfp

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt17.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From a2fd4ed8c6f84d945181320925c0dd18c87b3f76 Mon Sep 17 00:00:00 2001
From: Nikolay Borisov <kernel at kyup.com>
Date: Thu, 2 Jul 2015 01:34:07 -0400
Subject: ext4: avoid deadlocks in the writeback path by using sb_getblk_gfp

commit c45653c341f5c8a0ce19c8f0ad4678640849cb86 upstream.

Switch ext4 to using sb_getblk_gfp with GFP_NOFS added to fix possible
deadlocks in the page writeback path.

Signed-off-by: Nikolay Borisov <kernel at kyup.com>
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ext4/extents.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index a2c5bb7e71bb..ba5d7dc47b3e 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -487,7 +487,7 @@ __read_extent_tree_block(const char *function, unsigned int line,
 	struct buffer_head		*bh;
 	int				err;

-	bh = sb_getblk(inode->i_sb, pblk);
+	bh = sb_getblk_gfp(inode->i_sb, pblk, __GFP_MOVABLE | GFP_NOFS);
 	if (unlikely(!bh))
 		return ERR_PTR(-ENOMEM);

@@ -1061,7 +1061,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
 		err = -EIO;
 		goto cleanup;
 	}
-	bh = sb_getblk(inode->i_sb, newblock);
+	bh = sb_getblk_gfp(inode->i_sb, newblock, __GFP_MOVABLE | GFP_NOFS);
 	if (unlikely(!bh)) {
 		err = -ENOMEM;
 		goto cleanup;
@@ -1247,7 +1247,7 @@ static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
 	if (newblock == 0)
 		return err;

-	bh = sb_getblk(inode->i_sb, newblock);
+	bh = sb_getblk_gfp(inode->i_sb, newblock, __GFP_MOVABLE | GFP_NOFS);
 	if (unlikely(!bh))
 		return -ENOMEM;
 	lock_buffer(bh);