Date:   Mon, 15 May 2017 21:12:51 +0200
From:   Andreas Dilger <adilger@...ger.ca>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Theodore Ts'o <tytso@....edu>,
        linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH v2] e2freefrag: use GETFSMAP on mounted filesystems


> On May 15, 2017, at 8:37 PM, Darrick J. Wong <darrick.wong@...cle.com> wrote:
> 
> Use GETFSMAP to query mounted filesystems for free space information.
> This prevents us from reporting stale free space stats if there happen
> to be uncheckpointed block bitmap updates sitting in the journal.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>

Reviewed-by: Andreas Dilger <adilger@...ger.ca>

> ---
> v2: various cleanups to isolate the ioctl code more effectively
> ---
> configure         |    2 -
> configure.ac      |    1
> lib/config.h.in   |    3 +
> misc/e2freefrag.c |  121 +++++++++++++++++++++++++++++++++++++++++++++++++----
> misc/fsmap.h      |   89 +++++++++++++++++++++++++++++++++++++++
> 5 files changed, 206 insertions(+), 10 deletions(-)
> create mode 100644 misc/fsmap.h
> 
> diff --git a/configure b/configure
> index 5f7b429..2d75150 100755
> --- a/configure
> +++ b/configure
> @@ -12368,7 +12368,7 @@ fi
> done
> 
> fi
> -for ac_header in  	dirent.h 	errno.h 	execinfo.h 	getopt.h 	malloc.h 	mntent.h 	paths.h 	semaphore.h 	setjmp.h 	signal.h 	stdarg.h 	stdint.h 	stdlib.h 	termios.h 	termio.h 	unistd.h 	utime.h 	attr/xattr.h 	linux/falloc.h 	linux/fd.h 	linux/major.h 	linux/loop.h 	net/if_dl.h 	netinet/in.h 	sys/acl.h 	sys/disklabel.h 	sys/disk.h 	sys/file.h 	sys/ioctl.h 	sys/key.h 	sys/mkdev.h 	sys/mman.h 	sys/mount.h 	sys/prctl.h 	sys/resource.h 	sys/select.h 	sys/socket.h 	sys/sockio.h 	sys/stat.h 	sys/syscall.h 	sys/sysctl.h 	sys/sysmacros.h 	sys/time.h 	sys/types.h 	sys/un.h 	sys/wait.h
> +for ac_header in  	dirent.h 	errno.h 	execinfo.h 	getopt.h 	malloc.h 	mntent.h 	paths.h 	semaphore.h 	setjmp.h 	signal.h 	stdarg.h 	stdint.h 	stdlib.h 	termios.h 	termio.h 	unistd.h 	utime.h 	attr/xattr.h 	linux/falloc.h 	linux/fd.h 	linux/fsmap.h 	linux/major.h 	linux/loop.h 	net/if_dl.h 	netinet/in.h 	sys/acl.h 	sys/disklabel.h 	sys/disk.h 	sys/file.h 	sys/ioctl.h 	sys/key.h 	sys/mkdev.h 	sys/mman.h 	sys/mount.h 	sys/prctl.h 	sys/resource.h 	sys/select.h 	sys/socket.h 	sys/sockio.h 	sys/stat.h 	sys/syscall.h 	sys/sysctl.h 	sys/sysmacros.h 	sys/time.h 	sys/types.h 	sys/un.h 	sys/wait.h
> do :
>   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
> ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"
> diff --git a/configure.ac b/configure.ac
> index 9da7b86..a8bc15d 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -918,6 +918,7 @@ AC_CHECK_HEADERS(m4_flatten([
> 	attr/xattr.h
> 	linux/falloc.h
> 	linux/fd.h
> +	linux/fsmap.h
> 	linux/major.h
> 	linux/loop.h
> 	net/if_dl.h
> diff --git a/lib/config.h.in b/lib/config.h.in
> index bc006de..37d0c46 100644
> --- a/lib/config.h.in
> +++ b/lib/config.h.in
> @@ -244,6 +244,9 @@
> /* Define to 1 if you have the <linux/fd.h> header file. */
> #undef HAVE_LINUX_FD_H
> 
> +/* Define to 1 if you have the <linux/fsmap.h> header file. */
> +#undef HAVE_LINUX_FSMAP_H
> +
> /* Define to 1 if you have the <linux/loop.h> header file. */
> #undef HAVE_LINUX_LOOP_H
> 
> diff --git a/misc/e2freefrag.c b/misc/e2freefrag.c
> index 90acb7e..b315263 100644
> --- a/misc/e2freefrag.c
> +++ b/misc/e2freefrag.c
> @@ -25,11 +25,25 @@
> extern char *optarg;
> extern int optind;
> #endif
> +#if defined(HAVE_EXT2_IOCTLS) && !defined(DEBUGFS)
> +# include <sys/ioctl.h>
> +# include <sys/types.h>
> +# include <sys/stat.h>
> +# include <fcntl.h>
> +# include <limits.h>
> +#endif
> 
> #include "ext2fs/ext2_fs.h"
> #include "ext2fs/ext2fs.h"
> #include "e2freefrag.h"
> 
> +#if defined(HAVE_EXT2_IOCTLS) && !defined(DEBUGFS)
> +# ifdef HAVE_LINUX_FSMAP_H
> +#  include <linux/fsmap.h>
> +# endif
> +# include "fsmap.h"
> +#endif
> +
> static void usage(const char *prog)
> {
> 	fprintf(stderr, "usage: %s [-c chunksize in kb] [-h] "
> @@ -143,8 +157,97 @@ static void scan_block_bitmap(ext2_filsys fs, struct chunk_info *info)
> 		update_chunk_stats(info, last_chunk_size);
> }
> 
> -static errcode_t get_chunk_info(ext2_filsys fs, struct chunk_info *info,
> -				FILE *f)
> +#if defined(HAVE_EXT2_IOCTLS) && !defined(DEBUGFS)
> +# define FSMAP_EXTENTS	1024
> +static int scan_online(ext2_filsys fs, struct chunk_info *info)
> +{
> +	struct fsmap_head *fsmap;
> +	struct fsmap *extent;
> +	struct fsmap *p;
> +	char mntpoint[PATH_MAX + 1];
> +	errcode_t retval;
> +	int mount_flags;
> +	int fd;
> +	int ret;
> +	int i;
> +
> +	/* Try to open the mountpoint for a live query. */
> +	retval = ext2fs_check_mount_point(fs->device_name, &mount_flags,
> +					  mntpoint, PATH_MAX);
> +	if (retval) {
> +		com_err(fs->device_name, retval, "while checking mount status");
> +		return 0;
> +	}
> +	if (!mount_flags & EXT2_MF_MOUNTED)
> +		return 0;
> +	fd = open(mntpoint, O_RDONLY);
> +	if (fd < 0) {
> +		com_err(mntpoint, errno, "while opening mount point");
> +		return 0;
> +	}
> +
> +	fsmap = malloc(fsmap_sizeof(FSMAP_EXTENTS));
> +	if (!fsmap) {
> +		com_err(fs->device_name, errno, "while allocating memory");
> +		return 0;
> +	}
> +
> +	memset(fsmap, 0, sizeof(*fsmap));
> +	fsmap->fmh_count = FSMAP_EXTENTS;
> +	fsmap->fmh_keys[1].fmr_device = UINT_MAX;
> +	fsmap->fmh_keys[1].fmr_physical = ULLONG_MAX;
> +	fsmap->fmh_keys[1].fmr_owner = ULLONG_MAX;
> +	fsmap->fmh_keys[1].fmr_offset = ULLONG_MAX;
> +	fsmap->fmh_keys[1].fmr_flags = UINT_MAX;
> +
> +	/* Fill the extent histogram with live data */
> +	while (1) {
> +		ret = ioctl(fd, FS_IOC_GETFSMAP, fsmap);
> +		if (ret < 0) {
> +			com_err(fs->device_name, errno, "while calling fsmap");
> +			free(fsmap);
> +			return 0;
> +		}
> +
> +		/* No more extents to map, exit */
> +		if (!fsmap->fmh_entries)
> +			break;
> +
> +		for (i = 0, extent = fsmap->fmh_recs;
> +		     i < fsmap->fmh_entries;
> +		     i++, extent++) {
> +			if (!(extent->fmr_flags & FMR_OF_SPECIAL_OWNER) ||
> +			    extent->fmr_owner != FMR_OWN_FREE)
> +				continue;
> +			update_chunk_stats(info,
> +					   extent->fmr_length / fs->blocksize);
> +		}
> +
> +		p = &fsmap->fmh_recs[fsmap->fmh_entries - 1];
> +		if (p->fmr_flags & FMR_OF_LAST)
> +			break;
> +		fsmap_advance(fsmap);
> +	}
> +
> +	return 1;
> +}
> +#else
> +# define scan_online(fs, info)	(0)
> +#endif /* HAVE_EXT2_IOCTLS */
> +
> +static errcode_t scan_offline(ext2_filsys fs, struct chunk_info *info)
> +{
> +	errcode_t retval;
> +
> +	retval = ext2fs_read_block_bitmap(fs);
> +	if (retval)
> +		return retval;
> +	scan_block_bitmap(fs, info);
> +	return 0;
> +}
> +
> +static errcode_t dump_chunk_info(ext2_filsys fs, struct chunk_info *info,
> +				 FILE *f)
> {
> 	unsigned long total_chunks;
> 	const char *unitp = "KMGTPEZY";
> @@ -152,8 +255,6 @@ static errcode_t get_chunk_info(ext2_filsys fs, struct chunk_info *info,
> 	unsigned long start = 0, end;
> 	int i, retval = 0;
> 
> -	scan_block_bitmap(fs, info);
> -
> 	fprintf(f, "Total blocks: %llu\nFree blocks: %u (%0.1f%%)\n",
> 		ext2fs_blocks_count(fs->super), fs->super->s_free_blocks_count,
> 		(double)fs->super->s_free_blocks_count * 100 /
> @@ -228,18 +329,20 @@ static void collect_info(ext2_filsys fs, struct chunk_info *chunk_info, FILE *f)
> 	fprintf(f, "Device: %s\n", fs->device_name);
> 	fprintf(f, "Blocksize: %u bytes\n", fs->blocksize);
> 
> -	retval = ext2fs_read_block_bitmap(fs);
> +	init_chunk_info(fs, chunk_info);
> +	if (!scan_online(fs, chunk_info)) {
> +		init_chunk_info(fs, chunk_info);
> +		retval = scan_offline(fs, chunk_info);
> +	}
> 	if (retval) {
> 		com_err(fs->device_name, retval, "while reading block bitmap");
> 		close_device(fs->device_name, fs);
> 		exit(1);
> 	}
> 
> -	init_chunk_info(fs, chunk_info);
> -
> -	retval = get_chunk_info(fs, chunk_info, f);
> +	retval = dump_chunk_info(fs, chunk_info, f);
> 	if (retval) {
> -		com_err(fs->device_name, retval, "while collecting chunk info");
> +		com_err(fs->device_name, retval, "while dumping chunk info");
>                 close_device(fs->device_name, fs);
> 		exit(1);
> 	}
> diff --git a/misc/fsmap.h b/misc/fsmap.h
> new file mode 100644
> index 0000000..e9590aa
> --- /dev/null
> +++ b/misc/fsmap.h
> @@ -0,0 +1,89 @@
> +/*
> + * Copyright (c) 2017 Oracle.
> + * All Rights Reserved.
> + *
> + * Author: Darrick J. Wong <darrick.wong@...cle.com>
> + *
> + * 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
> + */
> +#ifndef FSMAP_H_
> +#define FSMAP_H_
> +
> +/* FS_IOC_GETFSMAP ioctl definitions */
> +#ifndef FS_IOC_GETFSMAP
> +struct fsmap {
> +	__u32		fmr_device;	/* device id */
> +	__u32		fmr_flags;	/* mapping flags */
> +	__u64		fmr_physical;	/* device offset of segment */
> +	__u64		fmr_owner;	/* owner id */
> +	__u64		fmr_offset;	/* file offset of segment */
> +	__u64		fmr_length;	/* length of segment */
> +	__u64		fmr_reserved[3];	/* must be zero */
> +};
> +
> +struct fsmap_head {
> +	__u32		fmh_iflags;	/* control flags */
> +	__u32		fmh_oflags;	/* output flags */
> +	__u32		fmh_count;	/* # of entries in array incl. input */
> +	__u32		fmh_entries;	/* # of entries filled in (output). */
> +	__u64		fmh_reserved[6];	/* must be zero */
> +
> +	struct fsmap	fmh_keys[2];	/* low and high keys for the mapping search */
> +	struct fsmap	fmh_recs[];	/* returned records */
> +};
> +
> +/* Size of an fsmap_head with room for nr records. */
> +static inline size_t
> +fsmap_sizeof(
> +	unsigned int	nr)
> +{
> +	return sizeof(struct fsmap_head) + nr * sizeof(struct fsmap);
> +}
> +
> +/* Start the next fsmap query at the end of the current query results. */
> +static inline void
> +fsmap_advance(
> +	struct fsmap_head	*head)
> +{
> +	head->fmh_keys[0] = head->fmh_recs[head->fmh_entries - 1];
> +}
> +
> +/*	fmh_iflags values - set by FS_IOC_GETFSMAP caller in the header. */
> +/* no flags defined yet */
> +#define FMH_IF_VALID		0
> +
> +/*	fmh_oflags values - returned in the header segment only. */
> +#define FMH_OF_DEV_T		0x1	/* fmr_device values will be dev_t */
> +
> +/*	fmr_flags values - returned for each non-header segment */
> +#define FMR_OF_PREALLOC		0x1	/* segment = unwritten pre-allocation */
> +#define FMR_OF_ATTR_FORK	0x2	/* segment = attribute fork */
> +#define FMR_OF_EXTENT_MAP	0x4	/* segment = extent map */
> +#define FMR_OF_SHARED		0x8	/* segment = shared with another file */
> +#define FMR_OF_SPECIAL_OWNER	0x10	/* owner is a special value */
> +#define FMR_OF_LAST		0x20	/* segment is the last in the FS */
> +
> +/* Each FS gets to define its own special owner codes. */
> +#define FMR_OWNER(type, code)	(((__u64)type << 32) | \
> +				 ((__u64)code & 0xFFFFFFFFULL))
> +#define FMR_OWNER_TYPE(owner)	((__u32)((__u64)owner >> 32))
> +#define FMR_OWNER_CODE(owner)	((__u32)(((__u64)owner & 0xFFFFFFFFULL)))
> +#define FMR_OWN_FREE		FMR_OWNER(0, 1) /* free space */
> +#define FMR_OWN_UNKNOWN		FMR_OWNER(0, 2) /* unknown owner */
> +#define FMR_OWN_METADATA	FMR_OWNER(0, 3) /* metadata */
> +
> +#define FS_IOC_GETFSMAP		_IOWR('X', 59, struct fsmap_head)
> +#endif /* FS_IOC_GETFSMAP */
> +
> +#endif


Cheers, Andreas






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