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    SubjectRe: Is there a "make hole" (truncate in middle) syscall?
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    On Thursday 04 December 2003 15:48, Mike Fedyk wrote:
    > On Thu, Dec 04, 2003 at 02:32:23PM -0600, Rob Landley wrote:
    > > You can make a file with a hole by seeking past it and never writing to
    > > that bit, but is there any way to punch a hole in a file after the fact?
    > > (I mean other with lseek and write. Having a sparse file as the
    > > result....)
    >
    > No, Linux doesn't have this feature.
    >
    > > What are the downsides of holes? (How big do they have to be to actually
    > > save space, is there a performance penalty to having a file with 1000 4k
    > > holes in it, etc...)
    >
    > When you copy them, you need to use tools that know about sparse files and
    > how to deal with them. Also, you will only save space on block aligned
    > contiguous zeros at least the length of one block.

    I knew that bit.

    I was thinking of making a toy that would run periodically against a
    seldom-changed filesystem, find runs of zeroes of a certain minimum size, and
    turn 'em into holes. The fragmentation might not be worth it, though...

    Rob
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