On 13.12.18 г. 23:16 ч., fdmanana@xxxxxxxxxx wrote:
> From: Filipe Manana <fdmanana@xxxxxxxx>
>
> 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: 74e4d82757f74 ("btrfs: let callers of btrfs_alloc_root pass gfp flags")
> Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
> ---
> fs/btrfs/disk-io.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 67afeaf28a41..3e1b846156dd 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -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"
> @@ -1235,10 +1236,17 @@ 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);
>
>
