linux-ext4 - Re: [PATCH 06/10] ext2: Factor our freeing of xattr block reference

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Date:   Thu, 14 Jul 2022 18:07:14 +0530
From:   Ritesh Harjani <ritesh.list@...il.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 06/10] ext2: Factor our freeing of xattr block reference

On 22/07/12 12:54PM, Jan Kara wrote:
> Free of xattr block reference is opencode in two places. Factor it out
> into a separate function and use it.

Looked into the refactoring logic. The patch looks good to me.
Small queries below -

>
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  fs/ext2/xattr.c | 90 +++++++++++++++++++++----------------------------
>  1 file changed, 38 insertions(+), 52 deletions(-)
>
> diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
> index 841fa6d9d744..9885294993ef 100644
> --- a/fs/ext2/xattr.c
> +++ b/fs/ext2/xattr.c
> @@ -651,6 +651,42 @@ ext2_xattr_set(struct inode *inode, int name_index, const char *name,
>  	return error;
>  }
>
> +static void ext2_xattr_release_block(struct inode *inode,
> +				     struct buffer_head *bh)
> +{
> +	struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
> +
> +	lock_buffer(bh);
> +	if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
> +		__u32 hash = le32_to_cpu(HDR(bh)->h_hash);
> +
> +		/*
> +		 * This must happen under buffer lock for
> +		 * ext2_xattr_set2() to reliably detect freed block
> +		 */
> +		mb_cache_entry_delete(ea_block_cache, hash,
> +				      bh->b_blocknr);
> +		/* Free the old block. */
> +		ea_bdebug(bh, "freeing");
> +		ext2_free_blocks(inode, bh->b_blocknr, 1);
> +		/* We let our caller release bh, so we
> +		 * need to duplicate the buffer before. */
> +		get_bh(bh);
> +		bforget(bh);
> +		unlock_buffer(bh);
> +	} else {
> +		/* Decrement the refcount only. */
> +		le32_add_cpu(&HDR(bh)->h_refcount, -1);
> +		dquot_free_block(inode, 1);
> +		mark_buffer_dirty(bh);
> +		unlock_buffer(bh);
> +		ea_bdebug(bh, "refcount now=%d",
> +			le32_to_cpu(HDR(bh)->h_refcount));
> +		if (IS_SYNC(inode))
> +			sync_dirty_buffer(bh);
> +	}
> +}
> +
>  /*
>   * Second half of ext2_xattr_set(): Update the file system.
>   */
> @@ -747,34 +783,7 @@ ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
>  		 * If there was an old block and we are no longer using it,
>  		 * release the old block.
>  		 */
> -		lock_buffer(old_bh);
> -		if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
> -			__u32 hash = le32_to_cpu(HDR(old_bh)->h_hash);
> -
> -			/*
> -			 * This must happen under buffer lock for
> -			 * ext2_xattr_set2() to reliably detect freed block
> -			 */
> -			mb_cache_entry_delete(ea_block_cache, hash,
> -					      old_bh->b_blocknr);
> -			/* Free the old block. */
> -			ea_bdebug(old_bh, "freeing");
> -			ext2_free_blocks(inode, old_bh->b_blocknr, 1);
> -			mark_inode_dirty(inode);

^^^ this is not needed because ext2_free_blocks() will take care of it.
Hence you have dropped this in ext2_xattr_release_block()

> -			/* We let our caller release old_bh, so we
> -			 * need to duplicate the buffer before. */
> -			get_bh(old_bh);
> -			bforget(old_bh);
> -		} else {
> -			/* Decrement the refcount only. */
> -			le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
> -			dquot_free_block_nodirty(inode, 1);
> -			mark_inode_dirty(inode);

Quick qn -> Don't we need mark_inode_dirty() here?

> -			mark_buffer_dirty(old_bh);
> -			ea_bdebug(old_bh, "refcount now=%d",
> -				le32_to_cpu(HDR(old_bh)->h_refcount));
> -		}
> -		unlock_buffer(old_bh);
> +		ext2_xattr_release_block(inode, old_bh);
>  	}
>
>  cleanup:
> @@ -828,30 +837,7 @@ ext2_xattr_delete_inode(struct inode *inode)
>  			EXT2_I(inode)->i_file_acl);
>  		goto cleanup;
>  	}
> -	lock_buffer(bh);
> -	if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
> -		__u32 hash = le32_to_cpu(HDR(bh)->h_hash);
> -
> -		/*
> -		 * This must happen under buffer lock for ext2_xattr_set2() to
> -		 * reliably detect freed block
> -		 */
> -		mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
> -				      bh->b_blocknr);
> -		ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
> -		get_bh(bh);
> -		bforget(bh);
> -		unlock_buffer(bh);
> -	} else {
> -		le32_add_cpu(&HDR(bh)->h_refcount, -1);
> -		ea_bdebug(bh, "refcount now=%d",
> -			le32_to_cpu(HDR(bh)->h_refcount));
> -		unlock_buffer(bh);
> -		mark_buffer_dirty(bh);
> -		if (IS_SYNC(inode))
> -			sync_dirty_buffer(bh);
> -		dquot_free_block_nodirty(inode, 1);
> -	}
> +	ext2_xattr_release_block(inode, bh);
>  	EXT2_I(inode)->i_file_acl = 0;
>
>  cleanup:
> --
> 2.35.3
>