Re: [PATCH] xfs_io: support a basic extent swap command

[Brian Foster <bfoster@redhat.com>]

On Tue, Feb 06, 2018 at 09:32:13AM -0800, Darrick J. Wong wrote:
> On Tue, Feb 06, 2018 at 08:02:47AM -0500, Brian Foster wrote:
> > Extent swap is a low level mechanism exported by XFS to facilitate
> > filesystem defragmentation. It is typically invoked by xfs_fsr under
> > conditions that will atomically adjust inode extent state without
> > loss of file data.
> > 
> > xfs_fsr does not provide the necessary controls for low-level
> > testing of the extent swap command, however. For example, xfs_fsr
> > implements policies that dictate when to perform an extent swap and
> > offers no control over the donor file characteristics.
> > 
> > Add a basic swapext command to xfs_io that allows userspace
> > invocation of the command under more controlled conditions. This
> > command makes no effort to retain data across the operation. As
> > such, it is primarily for testing purposes (i.e., in support of
> > xfstests, etc.).
> > 
> > Signed-off-by: Brian Foster <bfoster@redhat.com>
> > ---
> > 
> > This command is in support of an xfstests test to be posted shortly...
> > 
> > Brian
> > 
> >  io/Makefile  |   3 +-
> >  io/init.c    |   1 +
> >  io/io.h      |   1 +
> >  io/swapext.c | 107 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 111 insertions(+), 1 deletion(-)
> >  create mode 100644 io/swapext.c
> > 
> > diff --git a/io/Makefile b/io/Makefile
> > index 6725936d..2f9249e8 100644
> > --- a/io/Makefile
> > +++ b/io/Makefile
> > @@ -11,7 +11,8 @@ HFILES = init.h io.h
> >  CFILES = init.c \
> >  	attr.c bmap.c cowextsize.c encrypt.c file.c freeze.c fsync.c \
> >  	getrusage.c imap.c link.c mmap.c open.c parent.c pread.c prealloc.c \
> > -	pwrite.c reflink.c seek.c shutdown.c stat.c sync.c truncate.c utimes.c
> > +	pwrite.c reflink.c seek.c shutdown.c stat.c swapext.c sync.c \
> > +	truncate.c utimes.c
> >  
> >  LLDLIBS = $(LIBXCMD) $(LIBHANDLE) $(LIBPTHREAD)
> >  LTDEPENDENCIES = $(LIBXCMD) $(LIBHANDLE)
> > diff --git a/io/init.c b/io/init.c
> > index 20d5f80d..2ade03f4 100644
> > --- a/io/init.c
> > +++ b/io/init.c
> > @@ -88,6 +88,7 @@ init_commands(void)
> >  	sendfile_init();
> >  	shutdown_init();
> >  	stat_init();
> > +	swapext_init();
> >  	sync_init();
> >  	sync_range_init();
> >  	truncate_init();
> > diff --git a/io/io.h b/io/io.h
> > index 3862985f..258311f1 100644
> > --- a/io/io.h
> > +++ b/io/io.h
> > @@ -118,6 +118,7 @@ extern void		quit_init(void);
> >  extern void		seek_init(void);
> >  extern void		shutdown_init(void);
> >  extern void		stat_init(void);
> > +extern void		swapext_init(void);
> >  extern void		sync_init(void);
> >  extern void		truncate_init(void);
> >  extern void		utimes_init(void);
> > diff --git a/io/swapext.c b/io/swapext.c
> > new file mode 100644
> > index 00000000..5e161d69
> > --- /dev/null
> > +++ b/io/swapext.c
> > @@ -0,0 +1,107 @@
> > +/*
> > + * Copyright (c) 2018 Red Hat, Inc.
> > + * All Rights Reserved.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License as
> > + * published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it would be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write the Free Software Foundation,
> > + * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
> > + */
> > +
> > +#include "command.h"
> > +#include "input.h"
> > +#include "init.h"
> > +#include "io.h"
> > +
> > +static cmdinfo_t swapext_cmd;
> > +
> > +static void
> > +swapext_help(void)
> > +{
> > +	printf(_(
> > +"\n"
> > +" Swaps extents between the open file descriptor and the supplied filename.\n"
> 
> An update to the xfs_io manpage is needed, but this otherwise looks ok to me.
> 

Ok, will fix..

Brian

> --D
> 
> > +"\n"));
> > +}
> > +
> > +static int
> > +xfs_bulkstat_single(
> > +	int			fd,
> > +	xfs_ino_t		*lastip,
> > +	struct xfs_bstat	*ubuffer)
> > +{
> > +	struct xfs_fsop_bulkreq	bulkreq;
> > +
> > +	bulkreq.lastip = (__u64 *)lastip;
> > +	bulkreq.icount = 1;
> > +	bulkreq.ubuffer = ubuffer;
> > +	bulkreq.ocount = NULL;
> > +	return ioctl(fd, XFS_IOC_FSBULKSTAT_SINGLE, &bulkreq);
> > +}
> > +
> > +static int
> > +swapext_f(
> > +	int			argc,
> > +	char			**argv)
> > +{
> > +	int			fd;
> > +	int			error;
> > +	struct xfs_swapext	sx;
> > +	struct stat		stat;
> > +
> > +	/* open the donor file */
> > +	fd = openfile(argv[1], NULL, 0, 0, NULL);
> > +	if (fd < 0)
> > +		return 0;
> > +
> > +	/*
> > +	 * stat the target file to get the inode number and use the latter to
> > +	 * get the bulkstat info for the swapext cmd.
> > +	 */
> > +	error = fstat(file->fd, &stat);
> > +	if (error) {
> > +		perror("fstat");
> > +		goto out;
> > +	}
> > +
> > +	error = xfs_bulkstat_single(file->fd, &stat.st_ino, &sx.sx_stat);
> > +	if (error) {
> > +		perror("bulkstat");
> > +		goto out;
> > +	}
> > +	sx.sx_version = XFS_SX_VERSION;
> > +	sx.sx_fdtarget = file->fd;
> > +	sx.sx_fdtmp = fd;
> > +	sx.sx_offset = 0;
> > +	sx.sx_length = stat.st_size;
> > +	error = ioctl(file->fd, XFS_IOC_SWAPEXT, &sx);
> > +	if (error)
> > +		perror("swapext");
> > +
> > +out:
> > +	close(fd);
> > +	return 0;
> > +}
> > +
> > +void
> > +swapext_init(void)
> > +{
> > +	swapext_cmd.name = "swapext";
> > +	swapext_cmd.cfunc = swapext_f;
> > +	swapext_cmd.argmin = 1;
> > +	swapext_cmd.argmax = 1;
> > +	swapext_cmd.flags = CMD_NOMAP_OK;
> > +	swapext_cmd.args = _("<donorfile>");
> > +	swapext_cmd.oneline = _("Swap extents between files.");
> > +	swapext_cmd.help = swapext_help;
> > +
> > +	add_command(&swapext_cmd);
> > +}
> > -- 
> > 2.13.6
> > 
> > --
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