• Peter Staubach's avatar
    optimize attribute timeouts for "noac" and "actimeo=0" · 64672d55
    Peter Staubach authored
    I've been looking at a bugzilla which describes a problem where
    a customer was advised to use either the "noac" or "actimeo=0"
    mount options to solve a consistency problem that they were
    seeing in the file attributes.  It turned out that this solution
    did not work reliably for them because sometimes, the local
    attribute cache was believed to be valid and not timed out.
    (With an attribute cache timeout of 0, the cache should always
    appear to be timed out.)
    In looking at this situation, it appears to me that the problem
    is that the attribute cache timeout code has an off-by-one
    error in it.  It is assuming that the cache is valid in the
    region, [read_cache_jiffies, read_cache_jiffies + attrtimeo].  The
    cache should be considered valid only in the region,
    [read_cache_jiffies, read_cache_jiffies + attrtimeo).  With this
    change, the options, "noac" and "actimeo=0", work as originally
    This problem was previously addressed by special casing the
    attrtimeo == 0 case.  However, since the problem is only an off-
    by-one error, the cleaner solution is address the off-by-one
    error and thus, not require the special case.
    Signed-off-by: default avatarPeter Staubach <staubach@redhat.com>
    Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
jiffies.h 11.5 KB