• Michal Hocko's avatar
    mm: introduce kv[mz]alloc helpers · a7c3e901
    Michal Hocko authored
    Patch series "kvmalloc", v5.
    
    There are many open coded kmalloc with vmalloc fallback instances in the
    tree.  Most of them are not careful enough or simply do not care about
    the underlying semantic of the kmalloc/page allocator which means that
    a) some vmalloc fallbacks are basically unreachable because the kmalloc
    part will keep retrying until it succeeds b) the page allocator can
    invoke a really disruptive steps like the OOM killer to move forward
    which doesn't sound appropriate when we consider that the vmalloc
    fallback is available.
    
    As it can be seen implementing kvmalloc requires quite an intimate
    knowledge if the page allocator and the memory reclaim internals which
    strongly suggests that a helper should be implemented in the memory
    subsystem proper.
    
    Most callers, I could find, have been converted to use the helper
    instead.  This is patch 6.  There are some more relying on __GFP_REPEAT
    in the networking stack which I have converted as well and Eric Dumazet
    was not opposed [2] to convert them as well.
    
    [1] http://lkml.kernel.org/r/20170130094940.13546-1-mhocko@kernel.org
    [2] http://lkml.kernel.org/r/1485273626.16328.301.camel@edumazet-glaptop3.roam.corp.google.com
    
    This patch (of 9):
    
    Using kmalloc with the vmalloc fallback for larger allocations is a
    common pattern in the kernel code.  Yet we do not have any common helper
    for that and so users have invented their own helpers.  Some of them are
    really creative when doing so.  Let's just add kv[mz]alloc and make sure
    it is implemented properly.  This implementation makes sure to not make
    a large memory pressure for > PAGE_SZE requests (__GFP_NORETRY) and also
    to not warn about allocation failures.  This also rules out the OOM
    killer as the vmalloc is a more approapriate fallback than a disruptive
    user visible action.
    
    This patch also changes some existing users and removes helpers which
    are specific for them.  In some cases this is not possible (e.g.
    ext4_kvmalloc, libcfs_kvzalloc) because those seems to be broken and
    require GFP_NO{FS,IO} context which is not vmalloc compatible in general
    (note that the page table allocation is GFP_KERNEL).  Those need to be
    fixed separately.
    
    While we are at it, document that __vmalloc{_node} about unsupported gfp
    mask because there seems to be a lot of confusion out there.
    kvmalloc_node will warn about GFP_KERNEL incompatible (which are not
    superset) flags to catch new abusers.  Existing ones would have to die
    slowly.
    
    [sfr@canb.auug.org.au: f2fs fixup]
      Link: http://lkml.kernel.org/r/20170320163735.332e64b7@canb.auug.org.au
    Link: http://lkml.kernel.org/r/20170306103032.2540-2-mhocko@kernel.orgSigned-off-by: default avatarMichal Hocko <mhocko@suse.com>
    Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
    Reviewed-by: Andreas Dilger <adilger@dilger.ca>	[ext4 part]
    Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
    Cc: John Hubbard <jhubbard@nvidia.com>
    Cc: David Miller <davem@davemloft.net>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    a7c3e901
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