linux-ext4 - Re: [PATCH 2/3] ext4: ensure enough credits in ext4_ext_shift_path

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Date:   Thu, 30 Sep 2021 18:21:35 +0200
From:   Jan Kara <jack@...e.cz>
To:     yangerkun <yangerkun@...wei.com>
Cc:     tytso@....edu, jack@...e.cz, linux-ext4@...r.kernel.org,
        yukuai3@...wei.com
Subject: Re: [PATCH 2/3] ext4: ensure enough credits in
 ext4_ext_shift_path_extents

On Fri 03-09-21 14:27:47, yangerkun wrote:
> Like ext4_ext_rm_leaf, we can ensure enough credits before every call
> that will consume credits. This can remove ext4_access_path which only
> used in ext4_ext_shift_path_extents. It's a prepare patch for the next
> bugfix patch.
> 
> Signed-off-by: yangerkun <yangerkun@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/extents.c | 49 +++++++++++++++--------------------------------
>  1 file changed, 15 insertions(+), 34 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 7ae32078b48f..a6fb0350f062 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -4974,36 +4974,6 @@ int ext4_get_es_cache(struct inode *inode, struct fiemap_extent_info *fieinfo,
>  	return ext4_fill_es_cache_info(inode, start_blk, len_blks, fieinfo);
>  }
>  
> -/*
> - * ext4_access_path:
> - * Function to access the path buffer for marking it dirty.
> - * It also checks if there are sufficient credits left in the journal handle
> - * to update path.
> - */
> -static int
> -ext4_access_path(handle_t *handle, struct inode *inode,
> -		struct ext4_ext_path *path)
> -{
> -	int credits, err;
> -
> -	if (!ext4_handle_valid(handle))
> -		return 0;
> -
> -	/*
> -	 * Check if need to extend journal credits
> -	 * 3 for leaf, sb, and inode plus 2 (bmap and group
> -	 * descriptor) for each block group; assume two block
> -	 * groups
> -	 */
> -	credits = ext4_writepage_trans_blocks(inode);
> -	err = ext4_datasem_ensure_credits(handle, inode, 7, credits, 0);
> -	if (err < 0)
> -		return err;
> -
> -	err = ext4_ext_get_access(handle, inode, path);
> -	return err;
> -}
> -
>  /*
>   * ext4_ext_shift_path_extents:
>   * Shift the extents of a path structure lying between path[depth].p_ext
> @@ -5018,6 +4988,7 @@ ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,
>  	int depth, err = 0;
>  	struct ext4_extent *ex_start, *ex_last;
>  	bool update = false;
> +	int credits, restart_credits;
>  	depth = path->p_depth;
>  
>  	while (depth >= 0) {
> @@ -5027,13 +4998,23 @@ ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,
>  				return -EFSCORRUPTED;
>  
>  			ex_last = EXT_LAST_EXTENT(path[depth].p_hdr);
> +			/* leaf + sb + inode */
> +			credits = 3;
> +			if (ex_start == EXT_FIRST_EXTENT(path[depth].p_hdr)) {
> +				update = true;
> +				/* extent tree + sb + inode */
> +				credits = depth + 2;
> +			}
>  
> -			err = ext4_access_path(handle, inode, path + depth);
> +			restart_credits = ext4_writepage_trans_blocks(inode);
> +			err = ext4_datasem_ensure_credits(handle, inode, credits,
> +					restart_credits, 0);
>  			if (err)
>  				goto out;
>  
> -			if (ex_start == EXT_FIRST_EXTENT(path[depth].p_hdr))
> -				update = true;
> +			err = ext4_ext_get_access(handle, inode, path + depth);
> +			if (err)
> +				goto out;
>  
>  			while (ex_start <= ex_last) {
>  				if (SHIFT == SHIFT_LEFT) {
> @@ -5064,7 +5045,7 @@ ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,
>  		}
>  
>  		/* Update index too */
> -		err = ext4_access_path(handle, inode, path + depth);
> +		err = ext4_ext_get_access(handle, inode, path + depth);
>  		if (err)
>  			goto out;
>  
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR