[PATCH v2 0/4] extend vmalloc support for constrained allocations

From: Michal Hocko
Date: Mon Nov 22 2021 - 10:32:58 EST

The previous version has been posted here [1]

I hope I have addressed all the feedback. There were some suggestions
for further improvements but I would rather make this smaller as I
cannot really invest more time and I believe further changes can be done
on top.

This version is a rebase on top of the current Linus tree. Except for
the review feedback and conflicting changes in the area there is only
one change to filter out __GFP_NOFAIL from the bulk allocator. This is
not necessary strictly speaking AFAICS but I found it less confusing
because vmalloc has its fallback strategy and the bulk allocator is
meant only for the fast path.

Original cover:
Based on a recent discussion with Dave and Neil [2] I have tried to
implement NOFS, NOIO, NOFAIL support for the vmalloc to make
life of kvmalloc users easier.

A requirement for NOFAIL support for kvmalloc was new to me but this
seems to be really needed by the xfs code.

NOFS/NOIO was a known and a long term problem which was hoped to be
handled by the scope API. Those scope should have been used at the
reclaim recursion boundaries both to document them and also to remove
the necessity of NOFS/NOIO constrains for all allocations within that
scope. Instead workarounds were developed to wrap a single allocation
instead (like ceph_kvmalloc).

First patch implements NOFS/NOIO support for vmalloc. The second one
adds NOFAIL support and the third one bundles all together into kvmalloc
and drops ceph_kvmalloc which can use kvmalloc directly now.

I hope I haven't missed anything in the vmalloc allocator.


[1] http://lkml.kernel.org/r/20211025150223.13621-1-mhocko@xxxxxxxxxx
[2] http://lkml.kernel.org/r/163184741778.29351.16920832234899124642.stgit@noble.brown