linux-ext4 - Re: [PATCH, RFC -V2 4/4] ext4: Avoid group preallocation for closed files

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Message-ID: <20090821024545.GA9529@mit.edu>
Date:	Thu, 20 Aug 2009 22:45:45 -0400
From:	Theodore Tso <tytso@....edu>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	linux-ext4@...r.kernel.org, Andreas Dilger <adilger@....com>,
	Alex Tomas <bzzz@....com>
Subject: Re: [PATCH, RFC -V2 4/4] ext4: Avoid group preallocation for
	closed files

On Thu, Aug 20, 2009 at 12:10:35PM +0530, Aneesh Kumar K.V wrote:
> > +	if ((size == isize) &&
> 
> What is this check supposed to help us ?. This would also imply we
> disable prealloc only if we are allocating the last chunk in the
> file.

That was the idea, yes; the idea was to disable preallocation if the
file is small enough that it could be written in a single call to
ext4_da_writepages, or if we are allocating/writing the last chunk in
a file.  Otherwise, preallocation would be a good thing.

> shouldn't it be !ext4_fs_is_busy(sbi) ?. Can you also write function
> documentation for ext4_fs_is_busy. I found in confusing that you are
> decrementing s_lock_busy if we are going to spin on spin_lock.

Um, oops.  Yeah, good point.  It should be !ext4_fs_is_busy().  I also
have the logic backwards in ext4_lock_group as well, so the two errors
mostly cancel each other out.  I'll fix that in the patch.

       	      	   	       	    	- Ted
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