• David Howells's avatar
    fscache: Attach the index key and aux data to the cookie · 402cb8dd
    David Howells authored
    Attach copies of the index key and auxiliary data to the fscache cookie so
     (1) The callbacks to the netfs for this stuff can be eliminated.  This
         can simplify things in the cache as the information is still
         available, even after the cache has relinquished the cookie.
     (2) Simplifies the locking requirements of accessing the information as we
         don't have to worry about the netfs object going away on us.
     (3) The cache can do lazy updating of the coherency information on disk.
         As long as the cache is flushed before reboot/poweroff, there's no
         need to update the coherency info on disk every time it changes.
     (4) Cookies can be hashed or put in a tree as the index key is easily
         available.  This allows:
         (a) Checks for duplicate cookies can be made at the top fscache layer
         	 rather than down in the bowels of the cache backend.
         (b) Caching can be added to a netfs object that has a cookie if the
         	 cache is brought online after the netfs object is allocated.
    A certain amount of space is made in the cookie for inline copies of the
    data, but if it won't fit there, extra memory will be allocated for it.
    The downside of this is that live cache operation requires more memory.
    Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
    Acked-by: default avatarAnna Schumaker <anna.schumaker@netapp.com>
    Tested-by: default avatarSteve Dickson <steved@redhat.com>
cache.c 10.8 KB