Re: [PATCH 9/9] man: create a separate xfs shutdown ioctl manpage

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Jul 05, 2019 at 11:08:54AM -0500, Eric Sandeen wrote:
> On 6/20/19 11:51 AM, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Create a separate manual page for the xfs shutdown ioctl so we can
> > document how it works.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  man/man2/ioctl_xfs_goingdown.2 |   63 ++++++++++++++++++++++++++++++++++++++++
> >  man/man3/xfsctl.3              |    7 ++++
> >  2 files changed, 70 insertions(+)
> >  create mode 100644 man/man2/ioctl_xfs_goingdown.2
> > 
> > 
> > diff --git a/man/man2/ioctl_xfs_goingdown.2 b/man/man2/ioctl_xfs_goingdown.2
> > new file mode 100644
> > index 00000000..bedc85c8
> > --- /dev/null
> > +++ b/man/man2/ioctl_xfs_goingdown.2
> > @@ -0,0 +1,63 @@
> > +.\" Copyright (c) 2019, Oracle.  All rights reserved.
> > +.\"
> > +.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
> > +.\" SPDX-License-Identifier: GPL-2.0+
> > +.\" %%%LICENSE_END
> > +.TH IOCTL-XFS-GOINGDOWN 2 2019-06-17 "XFS"
> > +.SH NAME
> > +ioctl_xfs_goingdown \- shut down an XFS filesystem
> > +.SH SYNOPSIS
> > +.br
> > +.B #include <xfs/xfs_fs.h>
> > +.PP
> > +.BI "int ioctl(int " fd ", XFS_IOC_GOINGDOWN, uint32_t " flags );
> > +.SH DESCRIPTION
> > +Shuts down a live XFS filesystem.
> > +This is a software initiated hard shutdown and should be avoided whenever
> > +possible.
> > +After this call completes, the filesystem will be totally unusable and must be
> > +unmounted.
> 
> That almost sounds permanently destructive.  Perhaps:
> 
> "... will be totally unusable until the filesystem has been unmounted and remounted."
> 
> ?

Sounds good to me.

> > +
> > +.PP
> > +.I flags
> > +can be one of the following:
> > +.RS 0.4i
> > +.TP
> > +.B XFS_FSOP_GOING_FLAGS_DEFAULT
> > +Flush all dirty data and in-core state to disk, flush pending transactions to
> > +the log, and shut down.
> 
> What exactly do we mean by "in-core state" here?  I'm not sure the average
> reader will know (I'm not sure I know)

Hm... really it's any dirty cached state, like ... unflushed inodes and
dquots, dirty file data, etc.  I didn't want to commit to that level of
specificity though.

> > +.TP
> > +.B XFS_FSOP_GOING_FLAGS_LOGFLUSH
> > +Flush all pending transactions to the log and shut down, leaving all dirty
> > +data unwritten.
> > +.TP
> > +.B XFS_FSOP_GOING_FLAGS_NOLOGFLUSH
> > +Shut down immediately, without writing pending transactions or dirty data
> > +to disk.
> > +
> > +.SH RETURN VALUE
> > +On error, \-1 is returned, and
> > +.I errno
> > +is set to indicate the error.
> > +.PP
> > +.SH ERRORS
> > +Error codes can be one of, but are not limited to, the following:
> 
> Hm crud, now I wonder about auditing all your stated error codes.
> EPERM, EFAULT, and EINVAL seem to be the only options for this
> particular call.  Maybe that can be a 2nd cleanup, documenting
> an error code that won't happen is harmless...

<urk> Ok, I'll go do that. :)

> > +.TP
> > +.B EFSBADCRC
> > +Metadata checksum validation failed while performing the query.
> > +.TP
> > +.B EFSCORRUPTED
> > +Metadata corruption was encountered while performing the query.
> > +.TP
> > +.B EINVAL
> > +The specified allocation group number is not valid for this filesystem.

This one definitely was copypasta error. :(

--D

> > +.TP
> > +.B EIO
> > +An I/O error was encountered while performing the query.
> > +.TP
> > +.B EPERM
> > +Caller did not have permission to shut down the filesystem.
> > +.SH CONFORMING TO
> > +This API is specific to XFS filesystem on the Linux kernel.
> > +.SH SEE ALSO
> > +.BR ioctl (2)
> > diff --git a/man/man3/xfsctl.3 b/man/man3/xfsctl.3
> > index 077dd411..7e6588b8 100644
> > --- a/man/man3/xfsctl.3
> > +++ b/man/man3/xfsctl.3
> > @@ -365,6 +365,12 @@ See
> >  for more information.
> >  Save yourself a lot of frustration and avoid these ioctls.
> >  
> > +.TP
> > +.B XFS_IOC_GOINGDOWN
> > +See
> > +.BR ioctl_xfs_goingdown (2)
> > +for more information.
> > +
> >  .PP
> >  .nf
> >  .B XFS_IOC_THAW
> > @@ -388,6 +394,7 @@ as they are not of general use to applications.
> >  .BR ioctl_xfs_fscounts (2),
> >  .BR ioctl_xfs_getresblks (2),
> >  .BR ioctl_xfs_getbmap (2),
> > +.BR ioctl_xfs_goingdown (2),
> >  .BR fstatfs (2),
> >  .BR statfs (2),
> >  .BR xfs (5),
> >