CVS commit: src

[Matthew Jacob <mjacob%netbsd.org@localhost>]

Module Name:    src
Committed By:   mjacob
Date:           Mon Aug 10 16:56:25 UTC 1998

Modified Files:
        src/sys/dev/scsipi: st.c
Log Message:
Responding to an issue brought to my attention- when the device is
opened norewind and 2 filemarks are written at the end a phantom file
is left (just what I was afraid of, but I didn't think about it in
the last delta because somehow I had managed to convince myself that
this was a nonissue. It's not.).

So- in stdone clear ST_WRITTEN for regular reads. In st_close, preserve
the state of ST_WRITTEN, and if no error and 2FM@EOD for this device and
this is a no-rewind open, backspace one filemark. This should preserve
(for this mount session) FILE - FMK - FILE - FMK - FILE ... FILE FMK FMK EOD
sequencing.

This doesn't clean up the case of EOM appends- in this case you *will* still
get (after an MTEOM operation and a write of a file) a phantom empty file,
e.g. FILE - FMK FMK - FILE - FMK FMK EOD *unless* you follow the EOM operation
with an explicit backspace. The trouble is that this makes it difficult for
seamless interchange with other systems which don't necessarily follow.

The preferrable alternative would be to eliminate the 2FM@EOD except for
1/2" Reel tapes, but that has been pretty much nixed within developers.