Messages in this thread | | | Date | Mon, 16 Mar 2015 15:38:43 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 0/2] Move away from non-failing small allocations |
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On Wed, 11 Mar 2015 16:54:52 -0400 Michal Hocko <mhocko@suse.cz> wrote:
> as per discussion at LSF/MM summit few days back it seems there is a > general agreement on moving away from "small allocations do not fail" > concept.
Such a change affects basically every part of the kernel and every kernel developer. I expect most developers will say "it works well enough and I'm not getting any bug reports so why should I spend time on this?". It would help if we were to explain the justification very clearly. https://lwn.net/Articles/636017/ is Jon's writeup of the conference discussion.
Realistically, I don't think this overall effort will be successful - we'll add the knob, it won't get enough testing and any attempt to alter the default will be us deliberately destabilizing the kernel without knowing how badly :(
I wonder if we can alter the behaviour only for filesystem code, so we constrain the new behaviour just to that code where we're having problems. Most/all fs code goes via vfs methods so there's a reasonably small set of places where we can call
static inline void enter_fs_code(struct super_block *sb) { if (sb->my_small_allocations_can_fail) current->small_allocations_can_fail++; }
that way (or something similar) we can select the behaviour on a per-fs basis and the rest of the kernel remains unaffected. Other subsystems can opt in as well.
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