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Message-ID: <ZqySSHBweO18qJ4R@li-bb2b2a4c-3307-11b2-a85c-8fa5c3a69313.ibm.com>
Date: Fri, 2 Aug 2024 13:31:12 +0530
From: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To: libaokun@...weicloud.com
Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca,
        jack@...e.cz, ritesh.list@...il.com, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com, yangerkun@...wei.com,
        Baokun Li <libaokun1@...wei.com>
Subject: Re: [PATCH 11/20] ext4: get rid of ppath in ext4_ext_insert_extent()

On Wed, Jul 10, 2024 at 12:06:45PM +0800, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> The use of path and ppath is now very confusing, so to make the code more
> readable, pass path between functions uniformly, and get rid of ppath.
> 
> To get rid of the ppath in ext4_ext_insert_extent(), the following is done
> here:
> 
>  * Free the extents path when an error is encountered.
>  * Its caller needs to update ppath if it uses ppath.
>  * Free path when npath is used, free npath when it is not used.
>  * The got_allocated_blocks label in ext4_ext_map_blocks() does not
>    update err now, so err is updated to 0 if the err returned by
>    ext4_ext_search_right() is greater than 0 and is about to enter
>    got_allocated_blocks.
> 
> No functional changes.
> 
> Signed-off-by: Baokun Li <libaokun1@...wei.com>

Looks good, feel free to add:

Reviewed-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>

Regards,
ojaswin
> ---
>  fs/ext4/ext4.h        |  7 ++--
>  fs/ext4/extents.c     | 88 ++++++++++++++++++++++++-------------------
>  fs/ext4/fast_commit.c |  8 ++--
>  fs/ext4/migrate.c     |  5 ++-
>  4 files changed, 61 insertions(+), 47 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index cbe8d6062c52..53b4c1f454e6 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -3710,9 +3710,10 @@ extern int ext4_map_blocks(handle_t *handle, struct inode *inode,
>  extern int ext4_ext_calc_credits_for_single_extent(struct inode *inode,
>  						   int num,
>  						   struct ext4_ext_path *path);
> -extern int ext4_ext_insert_extent(handle_t *, struct inode *,
> -				  struct ext4_ext_path **,
> -				  struct ext4_extent *, int);
> +extern struct ext4_ext_path *ext4_ext_insert_extent(
> +				handle_t *handle, struct inode *inode,
> +				struct ext4_ext_path *path,
> +				struct ext4_extent *newext, int gb_flags);
>  extern struct ext4_ext_path *ext4_find_extent(struct inode *, ext4_lblk_t,
>  					      struct ext4_ext_path *,
>  					      int flags);
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 0d6ce9e74b01..fc75390d591a 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -1974,16 +1974,15 @@ static unsigned int ext4_ext_check_overlap(struct ext4_sb_info *sbi,
>   * inserts requested extent as new one into the tree,
>   * creating new leaf in the no-space case.
>   */
> -int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
> -				struct ext4_ext_path **ppath,
> -				struct ext4_extent *newext, int gb_flags)
> +struct ext4_ext_path *
> +ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
> +		       struct ext4_ext_path *path,
> +		       struct ext4_extent *newext, int gb_flags)
>  {
> -	struct ext4_ext_path *path = *ppath;
>  	struct ext4_extent_header *eh;
>  	struct ext4_extent *ex, *fex;
>  	struct ext4_extent *nearex; /* nearest extent */
> -	struct ext4_ext_path *npath = NULL;
> -	int depth, len, err;
> +	int depth, len, err = 0;
>  	ext4_lblk_t next;
>  	int mb_flags = 0, unwritten;
>  
> @@ -1991,14 +1990,16 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
>  		mb_flags |= EXT4_MB_DELALLOC_RESERVED;
>  	if (unlikely(ext4_ext_get_actual_len(newext) == 0)) {
>  		EXT4_ERROR_INODE(inode, "ext4_ext_get_actual_len(newext) == 0");
> -		return -EFSCORRUPTED;
> +		err = -EFSCORRUPTED;
> +		goto errout;
>  	}
>  	depth = ext_depth(inode);
>  	ex = path[depth].p_ext;
>  	eh = path[depth].p_hdr;
>  	if (unlikely(path[depth].p_hdr == NULL)) {
>  		EXT4_ERROR_INODE(inode, "path[%d].p_hdr == NULL", depth);
> -		return -EFSCORRUPTED;
> +		err = -EFSCORRUPTED;
> +		goto errout;
>  	}
>  
>  	/* try to insert block into found extent and return */
> @@ -2036,7 +2037,7 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
>  			err = ext4_ext_get_access(handle, inode,
>  						  path + depth);
>  			if (err)
> -				return err;
> +				goto errout;
>  			unwritten = ext4_ext_is_unwritten(ex);
>  			ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
>  					+ ext4_ext_get_actual_len(newext));
> @@ -2061,7 +2062,7 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
>  			err = ext4_ext_get_access(handle, inode,
>  						  path + depth);
>  			if (err)
> -				return err;
> +				goto errout;
>  
>  			unwritten = ext4_ext_is_unwritten(ex);
>  			ex->ee_block = newext->ee_block;
> @@ -2086,21 +2087,26 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
>  	if (le32_to_cpu(newext->ee_block) > le32_to_cpu(fex->ee_block))
>  		next = ext4_ext_next_leaf_block(path);
>  	if (next != EXT_MAX_BLOCKS) {
> +		struct ext4_ext_path *npath;
> +
>  		ext_debug(inode, "next leaf block - %u\n", next);
> -		BUG_ON(npath != NULL);
>  		npath = ext4_find_extent(inode, next, NULL, gb_flags);
> -		if (IS_ERR(npath))
> -			return PTR_ERR(npath);
> +		if (IS_ERR(npath)) {
> +			err = PTR_ERR(npath);
> +			goto errout;
> +		}
>  		BUG_ON(npath->p_depth != path->p_depth);
>  		eh = npath[depth].p_hdr;
>  		if (le16_to_cpu(eh->eh_entries) < le16_to_cpu(eh->eh_max)) {
>  			ext_debug(inode, "next leaf isn't full(%d)\n",
>  				  le16_to_cpu(eh->eh_entries));
> +			ext4_free_ext_path(path);
>  			path = npath;
>  			goto has_space;
>  		}
>  		ext_debug(inode, "next leaf has no free space(%d,%d)\n",
>  			  le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));
> +		ext4_free_ext_path(npath);
>  	}
>  
>  	/*
> @@ -2111,12 +2117,8 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
>  		mb_flags |= EXT4_MB_USE_RESERVED;
>  	path = ext4_ext_create_new_leaf(handle, inode, mb_flags, gb_flags,
>  					path, newext);
> -	if (IS_ERR(path)) {
> -		*ppath = NULL;
> -		err = PTR_ERR(path);
> -		goto cleanup;
> -	}
> -	*ppath = path;
> +	if (IS_ERR(path))
> +		return path;
>  	depth = ext_depth(inode);
>  	eh = path[depth].p_hdr;
>  
> @@ -2125,7 +2127,7 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
>  
>  	err = ext4_ext_get_access(handle, inode, path + depth);
>  	if (err)
> -		goto cleanup;
> +		goto errout;
>  
>  	if (!nearex) {
>  		/* there is no extent in this leaf, create first one */
> @@ -2183,17 +2185,20 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
>  	if (!(gb_flags & EXT4_GET_BLOCKS_PRE_IO))
>  		ext4_ext_try_to_merge(handle, inode, path, nearex);
>  
> -
>  	/* time to correct all indexes above */
>  	err = ext4_ext_correct_indexes(handle, inode, path);
>  	if (err)
> -		goto cleanup;
> +		goto errout;
>  
>  	err = ext4_ext_dirty(handle, inode, path + path->p_depth);
> +	if (err)
> +		goto errout;
>  
> -cleanup:
> -	ext4_free_ext_path(npath);
> -	return err;
> +	return path;
> +
> +errout:
> +	ext4_free_ext_path(path);
> +	return ERR_PTR(err);
>  }
>  
>  static int ext4_fill_es_cache_info(struct inode *inode,
> @@ -3248,24 +3253,29 @@ static int ext4_split_extent_at(handle_t *handle,
>  	if (split_flag & EXT4_EXT_MARK_UNWRIT2)
>  		ext4_ext_mark_unwritten(ex2);
>  
> -	err = ext4_ext_insert_extent(handle, inode, ppath, &newex, flags);
> -	if (err != -ENOSPC && err != -EDQUOT && err != -ENOMEM)
> +	path = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
> +	if (!IS_ERR(path)) {
> +		*ppath = path;
>  		goto out;
> +	}
> +	*ppath = NULL;
> +	err = PTR_ERR(path);
> +	if (err != -ENOSPC && err != -EDQUOT && err != -ENOMEM)
> +		return err;
>  
>  	/*
> -	 * Update path is required because previous ext4_ext_insert_extent()
> -	 * may have freed or reallocated the path. Using EXT4_EX_NOFAIL
> -	 * guarantees that ext4_find_extent() will not return -ENOMEM,
> -	 * otherwise -ENOMEM will cause a retry in do_writepages(), and a
> -	 * WARN_ON may be triggered in ext4_da_update_reserve_space() due to
> -	 * an incorrect ee_len causing the i_reserved_data_blocks exception.
> +	 * Get a new path to try to zeroout or fix the extent length.
> +	 * Using EXT4_EX_NOFAIL guarantees that ext4_find_extent()
> +	 * will not return -ENOMEM, otherwise -ENOMEM will cause a
> +	 * retry in do_writepages(), and a WARN_ON may be triggered
> +	 * in ext4_da_update_reserve_space() due to an incorrect
> +	 * ee_len causing the i_reserved_data_blocks exception.
>  	 */
> -	path = ext4_find_extent(inode, ee_block, *ppath,
> +	path = ext4_find_extent(inode, ee_block, NULL,
>  				flags | EXT4_EX_NOFAIL);
>  	if (IS_ERR(path)) {
>  		EXT4_ERROR_INODE(inode, "Failed split extent on %u, err %ld",
>  				 split, PTR_ERR(path));
> -		*ppath = NULL;
>  		return PTR_ERR(path);
>  	}
>  	depth = ext_depth(inode);
> @@ -3324,7 +3334,7 @@ static int ext4_split_extent_at(handle_t *handle,
>  	ext4_ext_dirty(handle, inode, path + path->p_depth);
>  	return err;
>  out:
> -	ext4_ext_show_leaf(inode, *ppath);
> +	ext4_ext_show_leaf(inode, path);
>  	return err;
>  }
>  
> @@ -4313,6 +4323,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>  	    get_implied_cluster_alloc(inode->i_sb, map, &ex2, path)) {
>  		ar.len = allocated = map->m_len;
>  		newblock = map->m_pblk;
> +		err = 0;
>  		goto got_allocated_blocks;
>  	}
>  
> @@ -4385,8 +4396,9 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>  		map->m_flags |= EXT4_MAP_UNWRITTEN;
>  	}
>  
> -	err = ext4_ext_insert_extent(handle, inode, &path, &newex, flags);
> -	if (err) {
> +	path = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
> +	if (IS_ERR(path)) {
> +		err = PTR_ERR(path);
>  		if (allocated_clusters) {
>  			int fb_flags = 0;
>  
> diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
> index 87c009e0c59a..1dee40477727 100644
> --- a/fs/ext4/fast_commit.c
> +++ b/fs/ext4/fast_commit.c
> @@ -1777,12 +1777,12 @@ static int ext4_fc_replay_add_range(struct super_block *sb,
>  			if (ext4_ext_is_unwritten(ex))
>  				ext4_ext_mark_unwritten(&newex);
>  			down_write(&EXT4_I(inode)->i_data_sem);
> -			ret = ext4_ext_insert_extent(
> -				NULL, inode, &path, &newex, 0);
> +			path = ext4_ext_insert_extent(NULL, inode,
> +						      path, &newex, 0);
>  			up_write((&EXT4_I(inode)->i_data_sem));
> -			ext4_free_ext_path(path);
> -			if (ret)
> +			if (IS_ERR(path))
>  				goto out;
> +			ext4_free_ext_path(path);
>  			goto next;
>  		}
>  
> diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
> index d98ac2af8199..0f68b8a14560 100644
> --- a/fs/ext4/migrate.c
> +++ b/fs/ext4/migrate.c
> @@ -37,7 +37,6 @@ static int finish_range(handle_t *handle, struct inode *inode,
>  	path = ext4_find_extent(inode, lb->first_block, NULL, 0);
>  	if (IS_ERR(path)) {
>  		retval = PTR_ERR(path);
> -		path = NULL;
>  		goto err_out;
>  	}
>  
> @@ -53,7 +52,9 @@ static int finish_range(handle_t *handle, struct inode *inode,
>  	retval = ext4_datasem_ensure_credits(handle, inode, needed, needed, 0);
>  	if (retval < 0)
>  		goto err_out;
> -	retval = ext4_ext_insert_extent(handle, inode, &path, &newext, 0);
> +	path = ext4_ext_insert_extent(handle, inode, path, &newext, 0);
> +	if (IS_ERR(path))
> +		retval = PTR_ERR(path);
>  err_out:
>  	up_write((&EXT4_I(inode)->i_data_sem));
>  	ext4_free_ext_path(path);
> -- 
> 2.39.2
> 

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