linux-ext4 - Re: [PATCH v2 5/9] ext4: make ext4_es_insert_delayed

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Date: Mon, 29 Apr 2024 11:16:38 +0200
From: Jan Kara <jack@...e.cz>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz,
	yi.zhang@...wei.com, chengzhihao1@...wei.com, yukuai3@...wei.com
Subject: Re: [PATCH v2 5/9] ext4: make ext4_es_insert_delayed_block() insert
 multi-blocks

On Wed 10-04-24 11:41:59, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
> 
> Rename ext4_es_insert_delayed_block() to ext4_es_insert_delayed_extent()
> and pass length parameter to make it insert multi delalloc blocks once a
> time. For the case of bigalloc, expand the allocated parameter to
> lclu_allocated and end_allocated. lclu_allocated indicates the allocate
> state of the cluster which containing the lblk, end_allocated represents
> the end, and the middle clusters must be unallocated.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

Looks mostly good, just one comment below:

> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index 4a00e2f019d9..2320b0d71001 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -2052,34 +2052,42 @@ bool ext4_is_pending(struct inode *inode, ext4_lblk_t lblk)
>  }
>  
>  /*
> - * ext4_es_insert_delayed_block - adds a delayed block to the extents status
> - *                                tree, adding a pending reservation where
> - *                                needed
> + * ext4_es_insert_delayed_extent - adds some delayed blocks to the extents
> + *                                 status tree, adding a pending reservation
> + *                                 where needed
>   *
>   * @inode - file containing the newly added block
> - * @lblk - logical block to be added
> - * @allocated - indicates whether a physical cluster has been allocated for
> - *              the logical cluster that contains the block
> + * @lblk - start logical block to be added
> + * @len - length of blocks to be added
> + * @lclu_allocated/end_allocated - indicates whether a physical cluster has
> + *                                 been allocated for the logical cluster
> + *                                 that contains the block
						        ^^^^ "start / end
block" to make it clearer...

> -void ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
> -				  bool allocated)
> +void ext4_es_insert_delayed_extent(struct inode *inode, ext4_lblk_t lblk,
> +				   ext4_lblk_t len, bool lclu_allocated,
> +				   bool end_allocated)
>  {
>  	struct extent_status newes;
> +	ext4_lblk_t end = lblk + len - 1;
>  	int err1 = 0, err2 = 0, err3 = 0;
>  	struct extent_status *es1 = NULL;
>  	struct extent_status *es2 = NULL;
> -	struct pending_reservation *pr = NULL;
> +	struct pending_reservation *pr1 = NULL;
> +	struct pending_reservation *pr2 = NULL;
>  
>  	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
>  		return;
>  
> -	es_debug("add [%u/1) delayed to extent status tree of inode %lu\n",
> -		 lblk, inode->i_ino);
> +	es_debug("add [%u/%u) delayed to extent status tree of inode %lu\n",
> +		 lblk, len, inode->i_ino);
> +	if (!len)
> +		return;
>  
>  	newes.es_lblk = lblk;
> -	newes.es_len = 1;
> +	newes.es_len = len;
>  	ext4_es_store_pblock_status(&newes, ~0, EXTENT_STATUS_DELAYED);
> -	trace_ext4_es_insert_delayed_block(inode, &newes, allocated);
> +	trace_ext4_es_insert_delayed_extent(inode, &newes, lclu_allocated,
> +					    end_allocated);
>  
>  	ext4_es_insert_extent_check(inode, &newes);
>  
> @@ -2088,11 +2096,15 @@ void ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
>  		es1 = __es_alloc_extent(true);
>  	if ((err1 || err2) && !es2)
>  		es2 = __es_alloc_extent(true);
> -	if ((err1 || err2 || err3) && allocated && !pr)
> -		pr = __alloc_pending(true);
> +	if (err1 || err2 || err3) {
> +		if (lclu_allocated && !pr1)
> +			pr1 = __alloc_pending(true);
> +		if (end_allocated && !pr2)
> +			pr2 = __alloc_pending(true);
> +	}
>  	write_lock(&EXT4_I(inode)->i_es_lock);
>  
> -	err1 = __es_remove_extent(inode, lblk, lblk, NULL, es1);
> +	err1 = __es_remove_extent(inode, lblk, end, NULL, es1);
>  	if (err1 != 0)
>  		goto error;
>  	/* Free preallocated extent if it didn't get used. */
> @@ -2112,13 +2124,22 @@ void ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
>  		es2 = NULL;
>  	}
>  
> -	if (allocated) {
> -		err3 = __insert_pending(inode, lblk, &pr);
> +	if (lclu_allocated) {
> +		err3 = __insert_pending(inode, lblk, &pr1);
>  		if (err3 != 0)
>  			goto error;
> -		if (pr) {
> -			__free_pending(pr);
> -			pr = NULL;
> +		if (pr1) {
> +			__free_pending(pr1);
> +			pr1 = NULL;
> +		}
> +	}
> +	if (end_allocated) {

So there's one unclear thing here: What if 'lblk' and 'end' are in the same
cluster? We don't want two pending reservation structures for the cluster.
__insert_pending() already handles this gracefully but perhaps we don't
need to allocate 'pr2' in that case and call __insert_pending() at all? I
think it could be easily handled by something like:

	if (EXT4_B2C(lblk) == EXT4_B2C(end))
		end_allocated = false;

at appropriate place in ext4_es_insert_delayed_extent().

Otherwise the patch looks good.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR