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FAILED: patch "[PATCH] btrfs: protect space cache inode alloc with GFP_NOFS" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Nov 12, 2018

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The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From 84de76a2fb217dc1b6bc2965cc397d1648aa1404 Mon Sep 17 00:00:00 2001

From: Josef Bacik <[email protected]>
Date: Fri, 28 Sep 2018 07:17:49 -0400
Subject: [PATCH] btrfs: protect space cache inode alloc with GFP_NOFS

If we're allocating a new space cache inode it's likely going to be under a transaction handle, so we need to use memalloc_nofs_save() in order to avoid deadlocks, and more importantly lockdep messages that make xfstests fail.

CC [email protected] # 4.4+
Reviewed-by Omar Sandoval <[email protected]>
Signed-off-by Josef Bacik <[email protected]>
Reviewed-by David Sterba <[email protected]>
Signed-off-by David Sterba <[email protected]>
fs/btrfs/free-space-cache.c +8 -0
index ed097ff023e8..a1f379e8ad13 100644
@@ -10,6 +10,7 @@
 #include <linux/math64.h>
 #include <linux/ratelimit.h>
 #include <linux/error-injection.h>
+#include <linux/sched/mm.h>
 #include "ctree.h"
 #include "free-space-cache.h"
 #include "transaction.h"

@@ -47,6 +48,7 @@ static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
 	struct btrfs_free_space_header *header;
 	struct extent_buffer *leaf;
 	struct inode *inode = NULL;
+	unsigned nofs_flag;
 	int ret;
 
 	key.objectid = BTRFS_FREE_SPACE_OBJECTID;

@@ -68,7 +70,13 @@ static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
 	btrfs_disk_key_to_cpu(&location, &disk_key);
 	btrfs_release_path(path);
 
+	/*
+	 * We are often under a trans handle at this point, so we need to make
+	 * sure NOFS is set to keep us from deadlocking.
+	 */
+	nofs_flag = memalloc_nofs_save();
 	inode = btrfs_iget(fs_info->sb, &location, root, NULL);
+	memalloc_nofs_restore(nofs_flag);
 	if (IS_ERR(inode))
 		return inode;