On Fri, Jun 14, 2019 at 05:00:30PM -0500, Eric Sandeen wrote:
> On 6/7/19 2:29 PM, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > Break out the fs geometry ioctl into a separate manpage so that we can
> > document how it works.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > ---
> > man/man2/ioctl_xfs_fsop_geometry.2 | 214 ++++++++++++++++++++++++++++++++++++
> > man/man3/xfsctl.3 | 11 +-
> > 2 files changed, 221 insertions(+), 4 deletions(-)
> > create mode 100644 man/man2/ioctl_xfs_fsop_geometry.2
> >
> >
> > diff --git a/man/man2/ioctl_xfs_fsop_geometry.2 b/man/man2/ioctl_xfs_fsop_geometry.2
> > new file mode 100644
> > index 00000000..4045e03b
> > --- /dev/null
> > +++ b/man/man2/ioctl_xfs_fsop_geometry.2
> > @@ -0,0 +1,214 @@
> > +.\" Copyright (c) 2019, Oracle. All rights reserved.
> > +.\"
> > +.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
> > +.\" SPDX-License-Identifier: GPL-2.0+
> > +.\" %%%LICENSE_END
> > +.TH IOCTL-XFS-FSOP-GEOMETRY 2 2019-04-11 "XFS"
> > +.SH NAME
> > +ioctl_xfs_fsop_geometry \- report XFS filesystem shape
> > +.SH SYNOPSIS
> > +.br
> > +.B #include <xfs/xfs_fs.h>
> > +.PP
> > +.BI "int ioctl(int " fd ", XFS_IOC_FSOP_GEOMETRY, struct xfs_fsop_geometry *" arg );
> > +.PP
>
> ditto on the .br?
>
> also xfs_fsop_geometry isn't a thing, is it? xfs_fsop_geom?
>
> > +.BI "int ioctl(int " fd ", XFS_IOC_FSOP_GEOMETRY_V1, struct xfs_fsop_geometry_v1 *" arg );
>
> and xfs_fsop_geom_v1
Fixed.
> > +.SH DESCRIPTION
> > +Report the storage space parameters that influence allocation decisions in
> > +this XFS filesystem.
> > +This information is conveyed in a structure of the following form:
> > +.PP
> > +.in +4n
> > +.nf
> > +struct xfs_fsop_geom {
> > + __u32 blocksize;
> > + __u32 rtextsize;
> > + __u32 agblocks;
> > + __u32 agcount;
> > + __u32 logblocks;
> > + __u32 sectsize;
> > + __u32 inodesize;
> > + __u32 imaxpct;
> > + __u64 datablocks;
> > + __u64 rtblocks;
> > + __u64 rtextents;
> > + __u64 logstart;
> > + unsigned char uuid[16];
> > + __u32 sunit;
> > + __u32 swidth;
> > + __s32 version;
> > + __u32 flags;
> > + __u32 logsectsize;
> > + __u32 rtsectsize;
> > + __u32 dirblocksize;
> > + /* struct xfs_fsop_geom_v1 stops here. */
> > +
> > + __u32 logsunit;
> > +};
> > +.fi
> > +.in
> > +.PP
> > +.I blocksize
> > +is the size of a fundamental filesystem block, in bytes.
> > +.PP
> > +.I rtextsize
> > +is the size of an extent on the realtime volume, in bytes.
> > +.PP
> > +.I agblocks
> > +is the size of an allocation group, in units of filesystem blocks.
> > +.PP
> > +.I agcount
> > +is the number of allocation groups in the filesystem.
> > +.PP
> > +.I logblocks
> > +is the size of the log, in units of filesystem blocks.
> > +.PP
> > +.I sectsize
> > +is the smallest amount of data that can be written to the data device
> > +atomically, in bytes.
> > +.PP
> > +.I inodesize
> > +is the size of an inode record, in bytes.
> > +.PP
> > +.I imaxpct
> > +is the maximum percentage of the filesystem that can be allocated to inode
> > +record blocks.
> > +.PP
> > +.I datablocks
> > +is the size of the data device, in units of filesystem blocks.
> > +.PP
> > +.I rtblocks
> > +is the size of the realtime device, in units of filesystem blocks.
> > +.PP
> > +.I rtextents
> > +is the number of extents that can be allocated on the realtime device.
> > +This ought to be
> > +.RB "( " rtblocks " * " blocksize " ) / " rtextsize .
>
> ought to be? I'm not sure what that means?
Dropped.
> > +.PP
> > +.I logstart
> > +tells the start of the log, in units of filesystem blocks.
>
> contains?
I'll change it to 'is' here.
> > +If the filesystem has an external log, this will be zero.
> > +.PP
> > +.I uuid
> > +is the universal unique identifier of the filesystem.
> > +.PP
> > +.I sunit
> > +is what the filesystem has been told is the size of a RAID stripe unit on the
> > +underlying data device, in filesystem blocks.
> > +.PP
> > +.I swidth
> > +is what the filesystem has been told is the width of a RAID stripe on the
> > +underlying data device, in units of RAID stripe units.
> > +.PP
> > +.I version
> > +is the version of this structure.
> > +This value will be XFS_FSOP_GEOM_VERSION.
> > +.PP
> > +.I flags
> > +tell us what features are enabled on the filesystem.
> > +This field can be any combination of the following:
> > +.RS 0.4i
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_ATTR
> > +Extended attributes are present.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_NLINK
> > +This filesystem supports up to 2^32 links.
>
> and if not it supports what?
>
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_QUOTA
> > +Quotas are enabled.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_IALIGN
> > +Inodes are aligned for better performance.
>
> aligned to ____ ? (worth trying to explain?)
Aligned to ... inode cluster buffer size, which we've never really
documented outside of "RTFS"? :)
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_DALIGN
> > +Data blocks are aligned for better performance.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_SHARED
> > +Unused.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_EXTFLG
> > +Filesystem supports unwritten extents.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_DIRV2
> > +Directories maintain free space data for better performance.
>
> I don't remember all the v1->v2 differences but in other places
> you simply say "contains version 2 format" or whatnot, so that might
> suffice here. Also can't do v1 since forever, anyway. ;)
Fixed.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_LOGV2
> > +Log uses the V2 format.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_SECTOR
> > +The log device has a sector size larger than 512 bytes.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_ATTR2
> > +Filesystem contains V2 extended attributes.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_PROJID32
> > +Project IDs can be as large as 2^32.
>
> otherwise 2^16?
yes.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_DIRV2CI
> > +Case-insensitive lookups are supported on directories.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_LAZYSB
> > +On-disk superblock counters are updated only at unmount time.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_V5SB
> > +Metadata blocks are self describing and contain checksums.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_FTYPE
> > +Directories cache inode types in directory entries.
>
> s/cache/contain/
Ok.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_FINOBT
> > +Filesystem maintains an index of free inodes.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_SPINODES
> > +Filesystem tries harder to allocate inodes when free space is fragmented.
>
> Filesystem may allocate discontinuous inode chunks when free space is fragmented?
Ok.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_RMAPBT
> > +Filesystem stores reverse mappings of blocks to owners.
> > +.TP
> > +.B XFS_FSOP_GEOM_FLAGS_REFLINK
> > +Filesystem supports sharing blocks.
>
> between inodes?
Between files; will fix.
> > +.RE
> > +
> > +.PD 1
> > +.PP
> > +.I logsectsize
> > +is the smallest amount of data that can be written to the log device atomically,
> > +in bytes.
>
> oh hello, we're back to the structure members again!
>
> I wonder if it'd be better to move the flag details down below all the structure descriptions.
Yeah, probably. I'll do that for all the new manpages since otherwise
this becomes a mess.
--D
> > +.PP
> > +.I rtsectsize
> > +is the smallest amount of data that can be written to the realtime device
> > +atomically, in bytes.
> > +.PP
> > +.I dirblocksize
> > +is the size of directory blocks, in bytes.
> > +.PP
> > +.I logsunit
> > +is what the filesystem has been told is the size of a RAID stripe unit on the
> > +underlying log device, in filesystem blocks.
> > +This field is meaningful only if the flag
> > +.B XFS_FSOP_GEOM_FLAGS_LOGV2
> > +is set.
> > +.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:
> > +.TP
> > +.B EFAULT
> > +The kernel was not able to copy into the userspace buffer.
> > +.TP
> > +.B EFSBADCRC
> > +Metadata checksum validation failed while performing the query.
> > +.TP
> > +.B EFSCORRUPTED
> > +Metadata corruption was encountered while performing the query.
> > +.TP
> > +.B EIO
> > +An I/O error was encountered while performing the query.
> > +.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 2992b5be..1237eac6 100644
> > --- a/man/man3/xfsctl.3
> > +++ b/man/man3/xfsctl.3
> > @@ -479,6 +479,12 @@ the kernel, except no output count parameter is used (should
> > be initialized to zero).
> > An error is returned if the inode number is invalid.
> >
> > +.TP
> > +.B XFS_IOC_FSGEOMETRY
> > +See
> > +.BR ioctl_xfs_fsop_geometry (2)
> > +for more information.
> > +
> > .PP
> > .nf
> > .B XFS_IOC_THAW
> > @@ -494,10 +500,6 @@ An error is returned if the inode number is invalid.
> > These interfaces are used to implement various filesystem internal
> > operations on XFS filesystems.
> > For
> > -.B XFS_IOC_FSGEOMETRY
> > -(get filesystem mkfs time information), the output structure is of type
> > -.BR struct xfs_fsop_geom .
> > -For
> > .B XFS_FS_COUNTS
> > (get filesystem dynamic global information), the output structure is of type
> > .BR xfs_fsop_counts_t .
> > @@ -506,6 +508,7 @@ as they are not of general use to applications.
> >
> > .SH SEE ALSO
> > .BR ioctl_xfs_fsgetxattr (2),
> > +.BR ioctl_xfs_fsop_geometry (2),
> > .BR fstatfs (2),
> > .BR statfs (2),
> > .BR xfs (5),
> >
