linux-kernel - Re: [PATCH 1/2 v2] fs: add SEEK_HOLE and SEEK

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Message-ID: <4DC1AA08.7000502@redhat.com>
Date:	Wed, 04 May 2011 15:33:28 -0400
From:	Josef Bacik <josef@...hat.com>
To:	Valdis.Kletnieks@...edu
CC:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-btrfs@...r.kernel.org
Subject: Re: [PATCH 1/2 v2] fs: add SEEK_HOLE and SEEK_DATA flags

On 05/04/2011 03:31 PM, Valdis.Kletnieks@...edu wrote:
> On Wed, 04 May 2011 13:58:39 EDT, Josef Bacik said:
>
>> +#define SEEK_HOLE	3	/* seek to the closest hole */
>> +#define SEEK_DATA	4	/* seek to the closest data */
>
> Comments here need nearest/next fixing as well - otherwise the ext[34] crew may
> actually implement the commented semantics. ;)
>

Balls, thanks I'll fix that.

> Other than that, patch 1/2 looks OK to me (not that there's much code to
> review), and 2/2 *seems* sane and implement the "next" semantics, though I only
> examined the while/if structure and am assuming the btrfs innards are done
> correctly.  In particular, that 'while (1)' looks like it can be painful for a
> sufficiently large and fragmented file (think a gigabyte file in 4K chunks,
> producing a million extents), but I'll let a btrfs expert analyse that
> performance issue ;)
>

Heh well we do while (1) in btrfs _everywhere_, so this isn't anything 
new, tho I should probably throw a cond_resched() in there.  Thanks,

Josef
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