Re: [PATCH v4] sg: O_EXCL and other lock handling

[Douglas Gilbert <dgilbert@interlog.com>]

On 14-06-13 05:03 AM, Christoph Hellwig wrote:
> Hi Doug,
>
> this looks generally good to me, but I don't think open_cnt and exclude
> have to use atomic_t, as they are only ever modified under open_rel_lock.

They are read by 'cat /proc/scsi/sg/debug' [in
sg_proc_seq_show_debug()] but transient off-by-1 reports
are not so important. [Prior to locking that block with
read_lock(sfd_lock) that routine sometimes printed wild
results, so some care is required.]

> Can you take a look at the version below?  This changes open_cnt to an
> int, exclude to a bool, removes the open_cnt underflow check that
> the VFS takes care for, and streamlines the open path a little bit:

sg_open() and sg_release() clean-up looks good. The
back-up goto at the end of sg_open() reminds me of
Fortran style :-) More importantly my sg_tst_excl*
tests give this version the thumbs up.

Acked-by: Douglas Gilbert <dgilbert@interlog.com>