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    SubjectRe: [PATCHSET 0/4] kmod: Optional timeout on the wait in call_usermodehelper_exec
    On 03/21/2012 08:35 AM, Greg KH wrote:
    > On Tue, Mar 20, 2012 at 04:18:49PM -0700, Boaz Harrosh wrote:
    >> Andrew Hi
    >>
    >> I'm picking on you because I don't have any one else to pick on.
    >> The 3 first patches here, are just good for today. Please see if
    >> you would like to take them? or tell me who should take them?
    >>
    >> The 4th patch is an RFC, which got me looking into this.
    >>
    >> My motivation is that I added yet another Kernel dependency on the
    >> call_usermodehelper() function and am not completely happy with the
    >> error case of having the user-mode program stuck forever. In such
    >> case I would like the Kernel part to timeout and properly error recover
    >> and clean up. So therefor the proposed 4th patch.
    >
    > What is this new use of call_usermodhelper that you are doing this work
    > for? Ideally, you never want to make this call, as it's slow and messy,
    > as you have found out. Is there an in-kernel user that you have
    > recently added?
    >
    > thanks,
    >
    > greg k-h

    I agree hence my comment in the 4th patch:
    "In the blasphemous occasions that a the Kernel must call a user-mode program"

    I have added a new caller, to the nfs/objectlayoutdriver.ko that uses this
    facility for auto-login into osd-targets (iscsi-targets) when new are requested
    by the filesystem. This auto-login facility is mandated by the pnfs-objects
    standard because in a large cluster filesystems for which pnfs was invented, storage
    devices break and changed everyday, and a manual login by every client is not
    feasible.

    You can see this patch as posted to the mailing list here:
    http://article.gmane.org/gmane.linux.nfs/48024/match=login
    [title: pnfs-obj: autologin: Add support for protocol autologin]

    It works very well and was heavily tested, with all error scenarios, but
    the theoretical possibility that the user-mode program can be stuck forever
    bothers me and I would like to do something about it. With this patch the
    Kernel can recover cleanly and continue. I have actually tested this part
    and it works as expected.

    Thanks
    Boaz


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