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

To: Jan Kara <jack@xxxxxxx>
Subject: Re: [PATCH 1/6] fs: add hole punching to fallocate
From: Andreas Dilger <adilger@xxxxxxxxx>
Date: Tue, 16 Nov 2010 18:22:47 -0600
Cc: Josef Bacik <josef@xxxxxxxxxx>, david@xxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-btrfs@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, cmm@xxxxxxxxxx, cluster-devel@xxxxxxxxxx, ocfs2-devel@xxxxxxxxxxxxxx
In-reply-to: <20101116131451.GH4757@xxxxxxxxxxxxx>
References: <1289840723-3056-1-git-send-email-josef@xxxxxxxxxx> <1289840723-3056-2-git-send-email-josef@xxxxxxxxxx> <20101116111611.GA4757@xxxxxxxxxxxxx> <20101116114346.GB4757@xxxxxxxxxxxxx> <20101116125249.GB31957@xxxxxxxxxxxxxxxxxxxxxxxxxx> <20101116131451.GH4757@xxxxxxxxxxxxx>
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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