• Dipankar Sarma's avatar
    [PATCH] files: files struct with RCU · ab2af1f5
    Dipankar Sarma authored
    Patch to eliminate struct files_struct.file_lock spinlock on the reader side
    and use rcu refcounting rcuref_xxx api for the f_count refcounter.  The
    updates to the fdtable are done by allocating a new fdtable structure and
    setting files->fdt to point to the new structure.  The fdtable structure is
    protected by RCU thereby allowing lock-free lookup.  For fd arrays/sets that
    are vmalloced, we use keventd to free them since RCU callbacks can't sleep.  A
    global list of fdtable to be freed is not scalable, so we use a per-cpu list.
    If keventd is already handling the current cpu's work, we use a timer to defer
    queueing of that work.
    Since the last publication, this patch has been re-written to avoid using
    explicit memory barriers and use rcu_assign_pointer(), rcu_dereference()
    premitives instead.  This required that the fd information is kept in a
    separate structure (fdtable) and updated atomically.
    Signed-off-by: default avatarDipankar Sarma <dipankar@in.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
open.c 23.3 KB