linux-ext4 - Re: [PATCH, RFC] ext4: add EXT4_IOC_ALLOC_DA

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Date:	Thu, 12 Mar 2009 10:59:06 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	"Theodore Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH, RFC] ext4: add EXT4_IOC_ALLOC_DA_BLKS ioctl

On Wed, Mar 11, 2009 at 05:41:05PM -0500, Eric Sandeen wrote:
> Theodore Ts'o wrote:
> > Add an ioctl which forces all of the delay allocated blocks to be
> > allocated.  This also provides a function ext4_alloc_da_blocks() which
> > will be used by the following commits to force files to be fully
> > allocated to preserve application-expected ext3 behaviour.
> > 
> 
> Is it worth checking whether a) the file has delalloc blocks, and/or b)
> whether the mapping is dirty before we spin off a filemap_flush?
> 
+int ext4_alloc_da_blocks(struct inode *inode)
+{
+       if (!EXT4_I(inode)->i_reserved_data_blocks &&
+           !EXT4_I(inode)->i_reserved_meta_blocks)
+               return 0;

This check test does (a). Since the ioctl is to force allocation of
delayed allocated blocks i guess (a) is enough because we don't want to
cause a filemap_flush when we don't have any delayed allocated blocks
but have dirty pages around.

-aneesh
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