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    SubjectRe: vmalloc with GFP_NOFS


    On Tue, 24 Apr 2018, Michal Hocko wrote:

    > On Wed 25-04-18 00:18:40, Richard Weinberger wrote:
    > > Am Dienstag, 24. April 2018, 21:28:03 CEST schrieb Michal Hocko:
    > > > > Also only for debugging.
    > > > > Getting rid of vmalloc with GFP_NOFS in UBIFS is no big problem.
    > > > > I can prepare a patch.
    > > >
    > > > Cool!
    > > >
    > > > Anyway, if UBIFS has some reclaim recursion critical sections in general
    > > > it would be really great to have them documented and that is where the
    > > > scope api is really handy. Just add the scope and document what is the
    > > > recursion issue. This will help people reading the code as well. Ideally
    > > > there shouldn't be any explicit GFP_NOFS in the code.
    > >
    > > So in a perfect world a filesystem calls memalloc_nofs_save/restore and
    > > always uses GFP_KERNEL for kmalloc/vmalloc?
    >
    > Exactly! And in a dream world those memalloc_nofs_save act as a
    > documentation of the reclaim recursion documentation ;)
    > --
    > Michal Hocko
    > SUSE Labs

    BTW. should memalloc_nofs_save and memalloc_noio_save be merged into just
    one that prevents both I/O and FS recursion?

    memalloc_nofs_save allows submitting bios to I/O stack and the bios
    created under memalloc_nofs_save could be sent to the loop device and the
    loop device calls the filesystem...

    Mikulas

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