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    SubjectRe: [PATCH 4/7][TAKE5] support new modes in fallocate
    On Wed, Jul 11, 2007 at 10:03:12AM +0100, Christoph Hellwig wrote:
    > On Tue, Jul 03, 2007 at 05:16:50PM +0530, Amit K. Arora wrote:
    > > Well, if you see the modes proposed using above flags :
    > >
    > > #define FA_ALLOCATE 0
    > >
    > > FA_FL_DEL_DATA is _not_ being used for preallocation. We have two modes
    > > for preallocation FA_ALLOCATE and FA_RESV_SPACE, which do not use this
    > > flag. Hence prealloction will never delete data.
    > > This mode is required only for FA_UNRESV_SPACE, which is a deallocation
    > > mode, to support any existing XFS aware applications/usage-scenarios.
    > Sorry, but this doesn't make any sense. There is no need to put every
    > feature in the XFS ioctls in the syscalls. The XFS ioctls will need to
    > be supported forever anyway - as I suggested before they really should
    > be moved to generic code.
    > What needs to be supported is what makes sense as an interface.
    > A punch a hole interface does make sense, but trying to hack this into
    > a preallocation system call is just madness. We're not IRIX or windows
    > that fit things into random subcall just because there was some space
    > left to squeeze them in.
    > > > > > FA_FL_NO_MTIME 0x10 /* keep same mtime (default change on size, data change) */
    > > > > > FA_FL_NO_CTIME 0x20 /* keep same ctime (default change on size, data change) */
    > > >
    > > > NACK to these aswell. If i_size changes c/mtime need updates, if the size
    > > > doesn't chamge they don't. No need to add more flags for this.
    > >
    > > This requirement was from the point of view of HSM applications. Hope
    > > you saw Andreas previous post and are keeping that in mind.
    > HSMs needs this basically for every system call, which screams for an
    > open flag like O_INVISIBLE anyway. Adding this in a generic way is
    > a good idea, but hacking bits and pieces that won't fit into the global
    > design is completely wrong.

    Why don't we just merge the interface for preallocation (essentially
    enough to satisfy posix_fallocate() and the simple XFS requirement for
    space reservation without changing file size), which there is clear agreement
    on (I hope :)). After all, this was all that we set out to do when we

    And leave all the dealloc/punch/hsm type features for separate future patches/
    debates, those really shouldn't hold up the basic fallocate interface.
    I agree with Christoph that we are just diverging too much in trying to
    club those decisions here.

    Dave, Andreas, Ted ?


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    Suparna Bhattacharya (
    Linux Technology Center
    IBM Software Lab, India

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