Btrfs: setup a nofs context for memory allocation at btrfs_create_tree() (b89f6d1f) · Commits · 戴 / test

We are holding a transaction handle when creating a tree, therefore we can not allocate the root using GFP_KERNEL, as we could deadlock if reclaim is triggered by the allocation, therefore setup a nofs context. Fixes: ("btrfs: let callers of btrfs_alloc_root pass gfp flags") CC: stable@vger.kernel.org # 4.9+ 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>

fs/btrfs/disk-io.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -17,6 +17,7 @@
		#include <linux/semaphore.h>
		#include <linux/error-injection.h>
		#include <linux/crc32c.h>
		#include <linux/sched/mm.h>
		#include <asm/unaligned.h>
		#include "ctree.h"
		#include "disk-io.h"
		@@ -1258,10 +1259,17 @@ struct btrfs_root btrfs_create_tree(struct btrfs_trans_handle trans,
		struct btrfs_root *tree_root = fs_info->tree_root;
		struct btrfs_root *root;
		struct btrfs_key key;
		unsigned int nofs_flag;
		int ret = 0;
		uuid_le uuid = NULL_UUID_LE;

		/*
		* We're holding a transaction handle, so use a NOFS memory allocation
		* context to avoid deadlock if reclaim happens.
		*/
		nofs_flag = memalloc_nofs_save();
		root = btrfs_alloc_root(fs_info, GFP_KERNEL);
		memalloc_nofs_restore(nofs_flag);
		if (!root)
		return ERR_PTR(-ENOMEM);

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