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From: David Howells <dhowells@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org,
	viro@zeniv.linux.org.uk, tytso@mit.edu, adilger.kernel@dilger.ca,
	darrick.wong@oracle.com, clm@fb.com, josef@toxicpanda.com,
	dsterba@suse.com, linux-ext4@vger.kernel.org,
	linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: Problems with determining data presence by examining extents?
Date: Wed, 15 Jan 2020 14:15:34 +0000
Message-ID: <24480.1579097734@warthog.procyon.org.uk> (raw)
In-Reply-To: <20200115083854.GB23039@lst.de>

Christoph Hellwig <hch@lst.de> wrote:

> The whole idea of an out of band interface is going to be racy and suffer
> from implementation loss.  I think what you want is something similar to
> the NFSv4.2 READ_PLUS operation - give me that if there is any and
> otherwise tell me that there is a hole.  I think this could be a new
> RWF_NOHOLE or similar flag, just how to return the hole size would be
> a little awkward.  Maybe return a specific negative error code (ENODATA?)
> and advance the iov anyway.

Just having call_iter_read() return a short read could be made to suffice...
provided the filesystem doesn't return data I haven't written in (which could
cause apparent corruption) and does return data I have written in (otherwise I
have to go back to the server).

David


      parent reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 16:48 David Howells
2020-01-14 22:49 ` Theodore Y. Ts'o
2020-01-15  3:54 ` Qu Wenruo
2020-01-15 12:46   ` Andreas Dilger
2020-01-15 13:10     ` Qu Wenruo
2020-01-15 13:31       ` Christoph Hellwig
2020-01-15 19:48         ` Andreas Dilger
2020-01-16 10:16           ` Christoph Hellwig
2020-01-15 20:55         ` David Howells
2020-01-15 22:11           ` Andreas Dilger
2020-01-15 23:09           ` David Howells
2020-01-26 18:19             ` Zygo Blaxell
2020-01-15 14:35       ` David Howells
2020-01-15 14:48         ` Christoph Hellwig
2020-01-15 14:59         ` David Howells
2020-01-16 10:13           ` Christoph Hellwig
2020-01-17 16:43           ` David Howells
2020-01-15 14:20   ` David Howells
2020-01-15  8:38 ` Christoph Hellwig
2020-01-15 13:50 ` David Howells
2020-01-15 14:05 ` David Howells
2020-01-15 14:24   ` Qu Wenruo
2020-01-15 14:50   ` David Howells
2020-01-15 14:15 ` David Howells [this message]

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