bug#6131: [PATCH]: fiemap support for efficient sparse file copy (original) (raw)

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From: Joel Becker
Subject: bug#6131: [PATCH]: fiemap support for efficient sparse file copy
Date: Wed, 16 Jun 2010 02:03:42 -0700
User-agent: Mutt/1.5.20 (2009-06-14)

On Wed, Jun 16, 2010 at 02:57:01PM +0800, jeff.liu wrote:

Paul Eggert wrote: > For example, if a fiemapextent has the FIEMAPEXTENTUNWRITTEN flag > set, cp should treat that as a hole, because the extent is all zeros. > (This will greatly help performance in some cases.) Also, if an input > extent is read and a block of it is found to be zeros, cp should skip > over that block when writing. If FIEMAPEXTENTUNWRITTEN flag is set, we can call fallocate(2) against the dest file directly for the performance boost.

    Nope.  An UNWRITTEN extent is a hole, and the user asked for

holes. If cp sees an UNWRITTEN extent it is skipped.

Joel

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"Friends may come and go, but enemies accumulate." - Thomas Jones

Joel Becker Principal Software Developer Oracle E-mail: address@hidden Phone: (650) 506-8127