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    SubjectRe: + c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-update-after-mm- num_exe_file_vmas-removal.patch added to -mm tree
    On 04/20, Cyrill Gorcunov wrote:
    > On Thu, Apr 19, 2012 at 09:20:05PM +0200, Oleg Nesterov wrote:
    > > On 04/19, Andrew Morton wrote:
    > > >
    > > > From: Konstantin Khlebnikov <>
    > > > Subject: c/r: prctl: update prctl_set_mm_exe_file() after mm->num_exe_file_vmas removal
    > > >
    > > > [ fix for "c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-v2" from mm tree ]
    > > >
    > > > After removing mm->num_exe_file_vmas kernel keeps mm->exe_file until final
    > > > mmput(), it never becomes NULL while task is alive.
    > > >
    > > > We can check for other mapped files in mm instead of checking
    > > > mm->num_exe_file_vmas, and mark mm with flag MMF_EXE_FILE_CHANGED in order
    > > > to forbid second changing of mm->exe_file.
    > >
    > > I lost the track a long ago.
    > >
    > > Just one question, what does this "forbid second changing" actually mean?
    > Heh :) Oleg, it was actually your idea to make this feature "one-shot".

    Heh, no ;)

    IIRC, I only asked you what do you actually want,

    Just one note for the record, prctl_set_mm_exe_file() does

    if (mm->num_exe_file_vmas)
    return -EBUSY;

    We could do

    if (mm->exe_file)
    return -EBUSY;

    This way "because this feature is a special to C/R" becomes
    really true. IOW, you can't do PR_SET_MM_EXE_FILE twice.

    I am fine either way, just I want to ensure you really want
    the current version.

    and only because it was documented as "feature is a special to C/R".

    > Once exe-file changed to a new value, it can't be changed again. The
    > reason was to bring at least minimum disturbance in sysadmins life.

    You misunderstood. I am not arguing with "one-shot", I do not really

    My question is: unless I missed something "it can't be changed again"
    is not actually true. A task does PR_SET_MM_EXE_FILE, then it forks
    the new child. The child can do PR_SET_MM_EXE_FILE again. Is this
    by design?


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