From: Valdis.Kletnieks@vt.edu
To: Josef Bacik <josef@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org, hch@infradead.org
Subject: Re: [PATCH 1/2] fs: add SEEK_HOLE and SEEK_DATA flags
Date: Sun, 24 Apr 2011 23:11:20 -0400 [thread overview]
Message-ID: <125854.1303701080@localhost> (raw)
In-Reply-To: Your message of "Thu, 21 Apr 2011 15:42:33 EDT." <1303414954-3315-1-git-send-email-josef@redhat.com>
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On Thu, 21 Apr 2011 15:42:33 EDT, Josef Bacik said:
> -SEEK_HOLE: this moves the file pos to the nearest hole in the file from the
> given position.
Do we want the semantic to be "the nearest" hole? Or did we really want "the
next" hole? Loops like a bullet loaded in the chamber and pointed at the
programmer's foot if they aren't allowing for the fact that this can go
*backwards* in the file if the closest hole is towards the beginning. Good way
to end up in an infinite loop or other messy...
Consider the obvious implementation of "skip over a hole" - lseek(SEEK_HOLE),
lseek(SEEK_DATA). and start reading data because we've skipped over the hole.
Wrong - the second seek may have gone backwards if the data was only 4K away
but the hole was 64K in size...
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prev parent reply other threads:[~2011-04-25 3:11 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-21 19:42 [PATCH 1/2] fs: add SEEK_HOLE and SEEK_DATA flags Josef Bacik
2011-04-21 19:42 ` [PATCH 2/2] Btrfs: implement our own ->llseek Josef Bacik
2011-04-21 20:45 ` [PATCH 1/2] fs: add SEEK_HOLE and SEEK_DATA flags Theodore Tso
2011-04-21 21:29 ` Sunil Mushran
2011-04-22 3:23 ` Matthew Wilcox
2011-04-22 4:47 ` Christoph Hellwig
[not found] ` <loom.20110422T001650-760@post.gmane.org>
[not found] ` <BANLkTiknb+hzFAjpwESwMcqMVtkFc0HFQQ@mail.gmail.com>
2011-04-22 4:50 ` Christoph Hellwig
2011-04-22 11:28 ` Markus Trippelsdorf
2011-04-22 11:50 ` Eric Blake
2011-04-22 16:28 ` Sunil Mushran
2011-04-22 16:40 ` Eric Blake
2011-04-22 16:57 ` Sunil Mushran
2011-04-22 17:03 ` Eric Blake
2011-04-22 17:08 ` Sunil Mushran
2011-04-22 18:06 ` Andreas Dilger
2011-04-22 23:33 ` Sunil Mushran
2011-04-24 17:49 ` Jamie Lokier
2011-04-25 12:37 ` Eric Blake
2011-04-25 14:15 ` Jamie Lokier
[not found] ` <4DB17D5B.2090303@redhat.com>
2011-04-25 15:02 ` Nick Bowler
2011-04-22 20:10 ` Jonathan Nieder
2011-04-22 20:49 ` Sunil Mushran
2011-04-25 3:11 ` Valdis.Kletnieks [this message]
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