Re: [PATCH 09/35] btrfs: protect space cache inode alloc with nofs

Omar Sandoval
2018-09-01T04:24:52Z

On Thu, Aug 30, 2018 at 01:41:59PM -0400, Josef Bacik wrote:
> 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.

Could use a comment where we call memalloc_nofs_save(). Otherwise,

Reviewed-by: Omar Sandoval <osandov@fb.com>

> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
> fs/btrfs/free-space-cache.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> index c3888c113d81..db93a5f035a0 100644
> --- a/fs/btrfs/free-space-cache.c
> +++ b/fs/btrfs/free-space-cache.c
> @@ -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 +70,9 @@ static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
> btrfs_disk_key_to_cpu(&location, &disk_key);
> btrfs_release_path(path);
>
> + 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;
>
> --
> 2.14.3
>