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 stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 827aa18e7b903c5ff3b3cd8fec328a99b1dbd411 Mon Sep 17 00:00:00 2001
From: Filipe Manana fdmanana@suse.com 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 nborisov@suse.com Signed-off-by: Filipe Manana fdmanana@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c index ea78c3d6dcfc..f141b45ce349 100644 --- a/fs/btrfs/xattr.c +++ b/fs/btrfs/xattr.c @@ -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; }