linux-ext4 - Re: [PATCH 1/6] fs: add hole punching to fallocate

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Message-Id: <18ACAA85-8847-4B12-9839-F99FB6C7B3E4@dilger.ca>
Date:	Tue, 16 Nov 2010 18:22:47 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	Jan Kara <jack@...e.cz>
Cc:	Josef Bacik <josef@...hat.com>, david@...morbit.com,
	linux-kernel@...r.kernel.org, linux-btrfs@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	xfs@....sgi.com, cmm@...ibm.com, cluster-devel@...hat.com,
	ocfs2-devel@....oracle.com
Subject: Re: [PATCH 1/6] fs: add hole punching to fallocate

On 2010-11-16, at 07:14, Jan Kara wrote:
>> Yeah I went back and forth on this.  KEEP_SIZE won't change the behavior of PUNCH_HOLE since PUNCH_HOLE implicitly means keep the size.  I figured since its "mode" and not "flags" it would be ok to make either way accepted, but if you prefer PUNCH_HOLE means you have to have KEEP_SIZE set then I'm cool with that, just let me know one way or the other.
> 
> So we call it "mode" but speak about "flags"? Seems a bit inconsistent.  
> I'd maybe lean a bit at the "flags" side and just make sure that only one of FALLOC_FL_KEEP_SIZE, FALLOC_FL_PUNCH_HOLE is set (interpreting FALLOC_FL_KEEP_SIZE as allocate blocks beyond i_size). But I'm not sure what others think.

IMHO, it makes more sense for consistency and "get what users expect" that these be treated as flags.  Some users will want KEEP_SIZE, but in other cases it may make sense that a hole punch at the end of a file should shrink the file (i.e. the opposite of an append).

Cheers, Andreas





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