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
> +.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?
> +.PP
> +.I logstart
> +tells the start of the log, in units of filesystem blocks.
contains?
> +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?)
> +.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. ;)
> +.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?
> +.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/
> +.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?
> +.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?
> +.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.
> +.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),
>
