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    SubjectRe: [PATCH] vmalloc: add warning in __vmalloc
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    On 3 May 2012 15:46, Sage Weil <sage@newdream.net> wrote:
    > On Thu, 3 May 2012, Minchan Kim wrote:
    >> On 05/03/2012 04:46 AM, Andrew Morton wrote:
    >> > Well.  What are we actually doing here?  Causing the kernel to spew a
    >> > warning due to known-buggy callsites, so that users will report the
    >> > warnings, eventually goading maintainers into fixing their stuff.
    >> >
    >> > This isn't very efficient :(
    >>
    >>
    >> Yes. I hope maintainers fix it before merging this.
    >>
    >> >
    >> > It would be better to fix that stuff first, then add the warning to
    >> > prevent reoccurrences.  Yes, maintainers are very naughty and probably
    >> > do need cattle prods^W^W warnings to motivate them to fix stuff, but we
    >> > should first make an effort to get these things fixed without
    >> > irritating and alarming our users.
    >> >
    >> > Where are these offending callsites?
    >
    > Okay, maybe this is a stupid question, but: if an fs can't call vmalloc
    > with GFP_NOFS without risking deadlock, calling with GFP_KERNEL instead
    > doesn't fix anything (besides being more honest).  This really means that
    > vmalloc is effectively off-limits for file systems in any
    > writeback-related path, right?

    Anywhere it cannot reenter the filesystem, yes. GFP_NOFS is effectively
    GFP_KERNEL when calling vmalloc.

    Note that in writeback paths, a "good citizen" filesystem should not require
    any allocations, or at least it should be able to tolerate allocation failures.
    So fixing that would be a good idea anyway.
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