• Dan Williams's avatar
    lib/genalloc: introduce chunk owners · 795ee306
    Dan Williams authored
    The p2pdma facility enables a provider to publish a pool of dma
    addresses for a consumer to allocate.  A genpool is used internally by
    p2pdma to collect dma resources, 'chunks', to be handed out to
    consumers.  Whenever a consumer allocates a resource it needs to pin the
    'struct dev_pagemap' instance that backs the chunk selected by
    pci_alloc_p2pmem().
    
    Currently that reference is taken globally on the entire provider
    device.  That sets up a lifetime mismatch whereby the p2pdma core needs
    to maintain hacks to make sure the percpu_ref is not released twice.
    
    This lifetime mismatch also stands in the way of a fix to
    devm_memremap_pages() whereby devm_memremap_pages_release() must wait for
    the percpu_ref ->release() callback to complete before it can proceed to
    teardown pages.
    
    So, towards fixing this situation, introduce the ability to store a 'chunk
    owner' at gen_pool_add() time, and a facility to retrieve the owner at
    gen_pool_{alloc,free}() time.  For p2pdma this will be used to store and
    recall individual dev_pagemap reference counter instances per-chunk.
    
    Link: http://lkml.kernel.org/r/155727338118.292046.13407378933221579644.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    Reviewed-by: default avatarIra Weiny <ira.weiny@intel.com>
    Reviewed-by: default avatarLogan Gunthorpe <logang@deltatee.com>
    Cc: Bjorn Helgaas <bhelgaas@google.com>
    Cc: "Jérôme Glisse" <jglisse@redhat.com>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: "Rafael J. Wysocki" <rafael@kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    795ee306
genalloc.c 21.7 KB