Matthew Dillon 7e76bb562e Implement IO_NOWDRAIN and B_NOWDRAIN - prevents the buffer cache from blocking ... in wdrain during a write. This flag needs to be used in devices whos strategy routines turn-around and issue another high level I/O, such as when MD turns around and issues a VOP_WRITE to vnode backing store, in order to avoid deadlocking the dirty buffer draining code. Remove a vprintf() warning from MD when the backing vnode is found to be in-use. The syncer of buf_daemon could be flushing the backing vnode at the time of an MD operation so the warning is not correct. MFC after: 1 week		2001-11-05 18:48:54 +00:00
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md.c	Implement IO_NOWDRAIN and B_NOWDRAIN - prevents the buffer cache from blocking	2001-11-05 18:48:54 +00:00