linux-ext4 - Re: [PATCH] ext4: fix callers of ext4_handle_release

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Message-ID: <20110321024324.GF4135@thunk.org>
Date:	Sun, 20 Mar 2011 22:43:24 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Amir Goldstein <amir73il@...il.com>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: fix callers of ext4_handle_release_buffer() API

On Tue, Mar 01, 2011 at 03:30:24PM +0200, Amir Goldstein wrote:
> ext4_handle_release_buffer() is an API, which is not being used properly.
> This is not so bad considering that it calls jbd2_journal_release_buffer(),
> which does nothing, but the snapshots implementation of this API does
> something.
> 
> ext4_jbd2.h defines 2 identical wrapper functions:
> ext4_journal_release_buffer() and ext4_handle_release_buffer().
> The former has no callers, so it was removed.

Note that there are some commented-out calls to
ext4_journal_release_buffer() in resize.c; they're probably commented
out because at least today, jbd2_journal_release_buffer() is indeed a
no-op.

I'll update resize.c to use the preferred call.  Speaking of which,
how does on-line resize work in the face of the snapshot feature?  Is
that something that is or isn't supported?

Note also that there may be places where a buffer has
get_write_access() called on it, only for it to be never modified.
resize.c is an example of that.

> There are 2 users of the API:
> ext4_new_inode() calls ext4_handle_release_buffer() and
> ext4_xattr_block_set() calls jbd2_journal_release_buffer() directly.
> The latter was chagned to call the wrapper API.
> 
> Signed-off-by: Amir Goldstein <amir73il@...rs.sf.net>

I'll apply this patch the changes.

						- Ted

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