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    SubjectRe: [PATCH] shrink_dcache_parent() races against shrink_dcache_memory()
    >><<<< and here, when you drop sb_lock, and dentry->d_lock/dcache_lock in 
    >>prune_dentry() it looks to me that we have exactly the same situation as
    >>it was without your patch:
    >><<<< another CPU can start umount in parallel.
    >><<<< maybe sb_lock barrier helps this somehow, but I can't see how yet...
    >
    >>From the unmount path, __mntput() is called. It sets s_active to 0 in
    > deactivate_super(), hence our check would prevent us from pruning a dentry
    > that is a part of a super block that is going to go away soon. The idea
    > is to let the unmount do all the work here, the allocator can concentrate
    > on other dentries.
    you check can happen 1 nanosecond before it sets s_active, after that
    the code goes into prune_dentry(), while deactivate_super() successfully
    sets s_active and starts umount main job. Nothing prevents the race... :(

    Kirill

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