linux-ext4 - Re: [PATCH 1/2] Make orphan functions no-op in no-journal mode

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Date:	Mon, 17 Sep 2012 23:32:04 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Anatol Pomozov <anatol.pomozov@...il.com>
Cc:	linux-ext4@...r.kernel.org, dmonakhov@...nvz.org
Subject: Re: [PATCH 1/2] Make orphan functions no-op in no-journal mode

On Mon, Sep 17, 2012 at 10:47:16AM -0700, Anatol Pomozov wrote:
> This avoids using shared mutext and thus improves scalability of
> no-journal mode. The goal of this change is similar to 3d287de3b828
> but it avoids mutex usage for all ext4_orphan_del(NULL,..) calls.

It doesn't really improve scalability in no-journal except in the
error case.  This is because....

> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 2a42cc0..6863cdf 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -2362,6 +2362,8 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
>  	struct ext4_iloc iloc;
>  	int err = 0, rc;
>  
> +	if (!EXT4_SB(sb)->s_journal)
> +		return 0;
>  	if (!ext4_handle_valid(handle))
>  		return 0;


The two checks above are equivalent.  If (!EXT4_SB(sb)->s_journal),
then ext4_journal_start() will return return an "invalid" handle.  So
this change is purely cosmetic.  I don't object to making the change
for consistency with the change to be made in ext4_orphan_del() below,
but we should remove the !ext4_handle_valid(handle) call in that case.


> @@ -2436,6 +2438,8 @@ int ext4_orphan_del(handle_t *handle, struct inode *inode)
>  	struct ext4_iloc iloc;
>  	int err = 0;
>  
> +	if (!EXT4_SB(inode->i_sb)->s_journal)
> +		return 0;
>  	/* ext4_handle_valid() assumes a valid handle_t pointer */
>  	if (handle && !ext4_handle_valid(handle))
>  		return 0;

We can remove the (handle && !ext4_handle_valid(handle)) conditional
here too.

						- Ted
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