On Mon, Jun 17, 2019 at 12:25:05PM -0500, Eric Sandeen wrote:
> On 6/7/19 2:29 PM, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > Create a separate manual page for the BMAP ioctls so we can document how
> > they work.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > ---
> > man/man2/ioctl_xfs_getbmap.2 | 165 ++++++++++++++++++++++++++++++++++++++++++
> > man/man3/xfsctl.3 | 61 +++-------------
> > 2 files changed, 175 insertions(+), 51 deletions(-)
> > create mode 100644 man/man2/ioctl_xfs_getbmap.2
> >
> >
> > diff --git a/man/man2/ioctl_xfs_getbmap.2 b/man/man2/ioctl_xfs_getbmap.2
> > new file mode 100644
> > index 00000000..5097173b
> > --- /dev/null
> > +++ b/man/man2/ioctl_xfs_getbmap.2
> > @@ -0,0 +1,165 @@
> > +.\" Copyright (c) 2019, Oracle. All rights reserved.
> > +.\"
> > +.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
> > +.\" SPDX-License-Identifier: GPL-2.0+
> > +.\" %%%LICENSE_END
> > +.TH IOCTL-XFS-GETBMAP 2 2019-04-11 "XFS"
> > +.SH NAME
> > +ioctl_xfs_getbmap \- query extent information for an open file
> > +.SH SYNOPSIS
> > +.br
> > +.B #include <xfs/xfs_fs.h>
> > +.PP
> > +.BI "int ioctl(int " fd ", XFS_IOC_GETBMAP, struct getbmap *" arg );
> > +.PP
> > +.BI "int ioctl(int " fd ", XFS_IOC_GETBMAPA, struct getbmap *" arg );
> > +.PP
> > +.BI "int ioctl(int " fd ", XFS_IOC_GETBMAPX, struct getbmapx *" arg );
> > +.SH DESCRIPTION
> > +Get the block map for a segment of a file in an XFS file system.
> > +The mapping information is conveyed in a structure of the following form:
> > +.PP
> > +.in +4n
> > +.nf
> > +struct getbmap {
> > + __s64 bmv_offset;
> > + __s64 bmv_block;
> > + __s64 bmv_length;
> > + __s32 bmv_count;
> > + __s32 bmv_entries;
> > +};
> > +.fi
> > +.in
> > +.PP
> > +The
> > +.B XFS_IOC_GETBMAPX
> > +ioctl uses a larger version of that structure:
> > +.PP
> > +.in +4n
> > +.nf
> > +struct getbmapx {
> > + __s64 bmv_offset;
> > + __s64 bmv_block;
> > + __s64 bmv_length;
> > + __s32 bmv_count;
> > + __s32 bmv_entries;
> > + __s32 bmv_iflags;
> > + __s32 bmv_oflags;
> > + __s32 bmv_unused1;
> > + __s32 bmv_unused2;
> > +};
> > +.fi
> > +.in
> > +.PP
> > +All sizes and offsets in the structure are in units of 512 bytes.
> > +.PP
> > +The first structure in the array is a header and the remaining structures in
> > +the array contain block map information on return.
> > +The header controls iterative calls to the command and should be filled out as
> > +follows:
> > +.TP
> > +.B bmv_offset
> > +The file offset of the area of interest in the file.
> > +.TP
> > +.B bmv_length
> > +The length of the area of interest in the file.
> > +If this value is set to -1, the length of the interesting area is the rest of
> > +the file.
> > +.TP
> > +.B bmv_count
> > +The length of the array, including this header.
> > +.TP
> > +.B bmv_entries
> > +The number of entries actually filled in by the call.
> > +This does not need to be filled out before the call.
> > +.TP
> > +.B bmv_iflags
> > +For the
> > +.B XFS_IOC_GETBMAPX
> > +function, this is a combination of the following flags:
>
> specifically mention that they are ORed or is that obvious?
"...this is a bitmask containing a combination of the following
flags..."
> > +.RS 0.4i
> > +.TP
> > +.B BMV_IF_ATTRFORK
> > +Return information about the extended attribute fork.
> > +.TP
> > +.B BMV_IF_PREALLOC
> > +Return information about unwritten pre-allocated segments.
> > +.TP
> > +.B BMV_IF_DELALLOC
> > +Return information about delayed allocation reservation segments.
> > +.TP
> > +.B BMV_IF_NO_HOLES
> > +Do not return information about holes.
> > +.RE
> > +.PD 1
>
> perhaps mention that others (bmv_block ...) are ignored in the header?
Ok.
> > +
> > +.PP
> > +On return from a call, the header is updated so that the command can be
> > +reused to obtain more information without re-initializing the structures.
> > +The remainder of the array will be filled out by the call as follows:
> > +
> > +.TP
> > +.B bmv_offset
> > +File offset of segment.
> > +.TP
> > +.B bmv_block
> > +Physical starting block of segment.
> > +If this is -1, then the segment is a hole.
> > +.TP
> > +.B bmv_length
> > +Length of segment.
> > +.TP
> > +.B bmv_oflags
> > +The
> > +.B XFS_IOC_GETBMAPX
> > +function will fill this field with a combination of the following flags:
> > +.RS 0.4i
> > +.TP
> > +.B BMV_OF_PREALLOC
> > +The segment is an unwritten pre-allocation.
> > +.TP
> > +.B BMV_OF_DELALLOC
> > +The segment is a delayed allocation reservation.
> > +.TP
> > +.B BMV_OF_LAST
> > +This segment is the last in the file.
> > +.TP
> > +.B BMV_OF_SHARED
> > +This segment shares blocks with other files.
> > +.RE
> > +.PD 1
> > +.PP
>
> .. and maybe mention that i.e. bmv_count is unused in the
> array of records? *shrug*
Ok.
--D
> > +The
> > +.B XFS_IOC_GETBMAPA
> > +command is identical to
> > +.B XFS_IOC_GETBMAP
> > +except that information about the attribute fork of the file is returned.
> > +.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 EINVAL
> > +One of the arguments was not valid.
> > +.TP
> > +.B EIO
> > +An I/O error was encountered while performing the query.
> > +.TP
> > +.B ENOMEM
> > +There was insufficient memory to perform 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 25e51417..e0986afb 100644
> > --- a/man/man3/xfsctl.3
> > +++ b/man/man3/xfsctl.3
> > @@ -144,59 +144,17 @@ See
> > .BR ioctl_xfs_fsgetxattr (2)
> > for more information.
> >
> > -.TP
> > -.B XFS_IOC_GETBMAP
> > -Get the block map for a segment of a file in an XFS file system.
> > -The final argument points to an arry of variables of type
> > -.BR "struct getbmap" .
> > -All sizes and offsets in the structure are in units of 512 bytes.
> > -The structure fields include:
> > -.B bmv_offset
> > -(file offset of segment),
> > -.B bmv_block
> > -(starting block of segment),
> > -.B bmv_length
> > -(length of segment),
> > -.B bmv_count
> > -(number of array entries, including the first), and
> > -.B bmv_entries
> > -(number of entries filled in).
> > -The first structure in the array is a header, and the remaining
> > -structures in the array contain block map information on return.
> > -The header controls iterative calls to the
> > +.PP
> > +.nf
> > .B XFS_IOC_GETBMAP
> > -command.
> > -The caller fills in the
> > -.B bmv_offset
> > -and
> > -.B bmv_length
> > -fields of the header to indicate the area of interest in the file,
> > -and fills in the
> > -.B bmv_count
> > -field to indicate the length of the array.
> > -If the
> > -.B bmv_length
> > -value is set to \-1 then the length of the interesting area is the rest
> > -of the file.
> > -On return from a call, the header is updated so that the command can be
> > -reused to obtain more information, without re-initializing the structures.
> > -Also on return, the
> > -.B bmv_entries
> > -field of the header is set to the number of array entries actually filled in.
> > -The non-header structures will be filled in with
> > -.BR bmv_offset ,
> > -.BR bmv_block ,
> > -and
> > -.BR bmv_length .
> > -If a region of the file has no blocks (is a hole in the file) then the
> > -.B bmv_block
> > -field is set to \-1.
> > -
> > -.TP
> > .B XFS_IOC_GETBMAPA
> > -Identical to
> > -.B XFS_IOC_GETBMAP
> > -except that information about the attribute fork of the file is returned.
> > +.fi
> > +.PD 0
> > +.TP
> > +.B XFS_IOC_GETBMAPX
> > +See
> > +.BR ioctl_getbmap (2)
> > +for more information.
> >
> > .PP
> > .B XFS_IOC_RESVSP
> > @@ -428,6 +386,7 @@ as they are not of general use to applications.
> > .BR ioctl_xfs_fsinumbers (2),
> > .BR ioctl_xfs_fscounts (2),
> > .BR ioctl_xfs_getresblks (2),
> > +.BR ioctl_xfs_getbmap (2),
> > .BR fstatfs (2),
> > .BR statfs (2),
> > .BR xfs (5),
> >
