Re: [PATCH 01/20] btrfs: change nr to u64 in btrfs_start_delalloc_roots

[Nikolay Borisov <nborisov@suse.com>]

On 30.01.20 г. 1:50 ч., Josef Bacik wrote:
> We have btrfs_wait_ordered_roots() which takes a u64 for nr, but
> btrfs_start_delalloc_roots() that takes an int for nr, which makes using
> them in conjunction, especially for something like (u64)-1, annoying and
> inconsistent.  Fix btrfs_start_delalloc_roots() to take a u64 for nr and
> adjust start_delalloc_inodes() and it's callers appropriately.

nit: You could include one more sentence to be explicit about the fact
that now 'nr' management is delegated to start_delalloc_inodes i.e you
pass it as a pointer to that function which in turn will control when
btrfs_Start_delalloc_roots breaks out of its own loop.

> 
> Part of adjusting the callers to this means changing
> btrfs_writeback_inodes_sb_nr() to take a u64 for items.  This may be
> confusing because it seems unrelated, but the caller of
> btrfs_writeback_inodes_sb_nr() already passes in a u64, it's just the
> function variable that needs to be changed.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
>  fs/btrfs/ctree.h       |  2 +-
>  fs/btrfs/dev-replace.c |  2 +-
>  fs/btrfs/inode.c       | 27 +++++++++++----------------
>  fs/btrfs/ioctl.c       |  2 +-
>  fs/btrfs/space-info.c  |  2 +-
>  5 files changed, 15 insertions(+), 20 deletions(-)
> 

<snip>

> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -9619,7 +9619,8 @@ static struct btrfs_delalloc_work *btrfs_alloc_delalloc_work(struct inode *inode
>   * some fairly slow code that needs optimization. This walks the list
>   * of all the inodes with pending delalloc and forces them to disk.
>   */
> -static int start_delalloc_inodes(struct btrfs_root *root, int nr, bool snapshot)
> +static int start_delalloc_inodes(struct btrfs_root *root, u64 *nr,
> +				 bool snapshot)
>  {
>  	struct btrfs_inode *binode;
>  	struct inode *inode;
> @@ -9659,9 +9660,11 @@ static int start_delalloc_inodes(struct btrfs_root *root, int nr, bool snapshot)
>  		list_add_tail(&work->list, &works);
>  		btrfs_queue_work(root->fs_info->flush_workers,
>  				 &work->work);
> -		ret++;
> -		if (nr != -1 && ret >= nr)
> -			goto out;
> +		if (*nr != U64_MAX) {
> +			(*nr)--;
> +			if (*nr == 0)
> +				goto out;
> +		}
>  		cond_resched();
>  		spin_lock(&root->delalloc_lock);
>  	}
> @@ -9686,18 +9689,15 @@ static int start_delalloc_inodes(struct btrfs_root *root, int nr, bool snapshot)
>  int btrfs_start_delalloc_snapshot(struct btrfs_root *root)
>  {
>  	struct btrfs_fs_info *fs_info = root->fs_info;
> -	int ret;
> +	u64 nr = U64_MAX;

This var is never used past start_delalloc_snapshot so you can remove it
and simply pass U64_MAX to start_delalloc_inodes.

>  
>  	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state))
>  		return -EROFS;
>  
> -	ret = start_delalloc_inodes(root, -1, true);
> -	if (ret > 0)
> -		ret = 0;
> -	return ret;
> +	return start_delalloc_inodes(root, &nr, true);
>  }
>  
> -int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, int nr)
> +int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, u64 nr)
>  {
>  	struct btrfs_root *root;
>  	struct list_head splice;
> @@ -9720,15 +9720,10 @@ int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, int nr)
>  			       &fs_info->delalloc_roots);
>  		spin_unlock(&fs_info->delalloc_root_lock);
>  
> -		ret = start_delalloc_inodes(root, nr, false);
> +		ret = start_delalloc_inodes(root, &nr, false);
>  		btrfs_put_root(root);
>  		if (ret < 0)
>  			goto out;
> -
> -		if (nr != -1) {
> -			nr -= ret;
> -			WARN_ON(nr < 0);
> -		}
>  		spin_lock(&fs_info->delalloc_root_lock);
>  	}
>  	spin_unlock(&fs_info->delalloc_root_lock);

<snip>