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FAILED: patch "[PATCH] Btrfs: use nofs context when initializing security xattrs to" failed to apply to 4.14-stable tree

PATCH [email protected] 1 participant 1 message Jan 15, 2019

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The patch below does not apply to the 4.14-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 ------------------

From 827aa18e7b903c5ff3b3cd8fec328a99b1dbd411 Mon Sep 17 00:00:00 2001
From: Filipe Manana <[email protected]>
Date: Mon, 10 Dec 2018 17:53:35 +0000
Subject: [PATCH] Btrfs: use nofs context when initializing security xattrs to
avoid deadlock

When initializing the security xattrs, we are holding a transaction handle therefore we need to use a GFP_NOFS context in order to avoid a deadlock with reclaim in case it's triggered.

Fixes 39a27ec1004e8 ("btrfs: use GFP_KERNEL for xattr and acl allocations")
Reviewed-by Nikolay Borisov <[email protected]>
Signed-off-by Filipe Manana <[email protected]>
Reviewed-by David Sterba <[email protected]>
Signed-off-by David Sterba <[email protected]>
fs/btrfs/xattr.c +8 -0
index ea78c3d6dcfc..f141b45ce349 100644
@@ -11,6 +11,7 @@
 #include <linux/security.h>
 #include <linux/posix_acl_xattr.h>
 #include <linux/iversion.h>
+#include <linux/sched/mm.h>
 #include "ctree.h"
 #include "btrfs_inode.h"
 #include "transaction.h"

@@ -422,9 +423,15 @@ static int btrfs_initxattrs(struct inode *inode,
 {
 	const struct xattr *xattr;
 	struct btrfs_trans_handle *trans = fs_info;
+	unsigned int nofs_flag;
 	char *name;
 	int err = 0;
 
+	/*
+	 * We're holding a transaction handle, so use a NOFS memory allocation
+	 * context to avoid deadlock if reclaim happens.
+	 */
+	nofs_flag = memalloc_nofs_save();
 	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 		name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 			       strlen(xattr->name) + 1, GFP_KERNEL);

@@ -440,6 +447,7 @@ static int btrfs_initxattrs(struct inode *inode,
 		if (err < 0)
 			break;
 	}
+	memalloc_nofs_restore(nofs_flag);
 	return err;
 }