lvm2/device_mapper/raid/raid_parser.c

/*
 * Copyright (C) 2024 Red Hat, Inc. All rights reserved.
 *
 * This file is part of the device-mapper userspace tools.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU Lesser General Public License v.2.1.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/*
 * Support counting number of failed device bits in dm-raid superblock bit arrays or clear them out.
 */

#include "device_mapper/misc/dmlib.h"
#include "device_mapper/all.h"
#include "device_mapper/raid/target.h"
#include "lib/mm/xlate.h"
#include <fcntl.h>
#include <unistd.h>

/* Copied/derived from kernel's drivers/md/dm-raid.c so this is prone to out-of-sync (factor out to header file?). */
#define	MAX_RAID_DEVICES		253 /* md-raid kernel limit? */
#define UINT64_BITS			(sizeof(uint64_t) * 8)
#define DISKS_ARRAY_ELEMS		((MAX_RAID_DEVICES + (UINT64_BITS - 1)) / UINT64_BITS)
#define DM_RAID_SB_MAGIC		0x446D5264 /* "DmRd" */
#define	FEATURE_FLAG_SUPPORTS_V190	0x1 /* Supports extended superblock */

/* RAID superblock at beginning of rmeta SubLVs trimmed down to mandatory members. */
struct dm_raid_superblock {
	__le32 magic;		/* "DmRd" */
	__le32 compat_features;	/* Used to indicate compatible features (like 1.9.0 ondisk metadata extension) */
	__le32 dummy[4];
	__le64 failed_devices;	/* Pre 1.9.0 part of bit field of devices to */
				/* indicate device failures (see extension below) */
	__le32 dummy1[7];

	/********************************************************************
	 * BELOW FOLLOW V1.9.0 EXTENSIONS TO THE PRISTINE SUPERBLOCK FORMAT!!!
	 *
	 * FEATURE_FLAG_SUPPORTS_V190 in the compat_features member indicates that those exist
	 */
	__le32 flags; /* Flags defining array states for reshaping */
	__le32 dummy2[14];
	__le64 extended_failed_devices[DISKS_ARRAY_ELEMS - 1];

	__le32 dummy3;
	/* Always set rest up to logical block size to 0 when writing ... */
} __packed;
/* END: Copied from ... */

/* Superblock I/O buffer size to be able to Cope with 4K native devices... */
#define	SB_BUFSZ	4096

static size_t _get_sb_size(const struct dm_raid_superblock *sb)
{
	return (FEATURE_FLAG_SUPPORTS_V190 & le32_to_cpu(sb->compat_features)) ?
	       sizeof(*sb) : ((char *) &sb->flags - (char *) sb);
}

static uint32_t _hweight64(__le64 v)
{
	uint32_t r = 0;

	while (v) {
		r += v & 1;
		v >>= 1;
	}

	return r;
}

static uint32_t _hweight_failed(struct dm_raid_superblock *sb)
{
	uint32_t r = _hweight64(sb->failed_devices);

	if (_get_sb_size(sb) == sizeof(*sb)) {
		int i = (int)DM_ARRAY_SIZE(sb->extended_failed_devices);

		while (i--)
			r = max(r, _hweight64(sb->extended_failed_devices[i]));
	}

	return r;
}

static void _clear_failed_devices(struct dm_raid_superblock *sb)
{

	sb->failed_devices = 0;

	if (_get_sb_size(sb) == sizeof(*sb))
		memset(sb->extended_failed_devices, 0, sizeof(sb->extended_failed_devices));
}

static int _count_or_clear_failed_devices(const char *dev_path, bool clear, uint32_t *nr_failed)
{
	struct dm_raid_superblock *sb = NULL;
	size_t sz;
	int fd, r = 0;

	if (posix_memalign((void *) &sb, SB_BUFSZ, SB_BUFSZ)) {
		log_sys_error("Failed to allocate RAID superblock buffer", dev_path);
		return 0;
	}

	fd = open(dev_path, O_EXCL | ((clear) ?  O_RDWR : O_RDONLY) | O_DIRECT);
	if (fd < 0) {
		log_sys_error("Failed to open RAID metadata volume", dev_path);
		goto out;
	}

	if (read(fd, sb, SB_BUFSZ) != SB_BUFSZ) {
		log_sys_error("Failed to read RAID metadata volume", dev_path);
		goto out;
	}

	/* FIXME: big endian??? */
	if (sb->magic != cpu_to_be32(DM_RAID_SB_MAGIC)) {
		log_error("No RAID signature on %s.", dev_path);
		goto out;
	}

	if (nr_failed)
		*nr_failed = _hweight_failed(sb);

	if (clear) {
		if (lseek(fd, 0, SEEK_SET) < 0) {
			log_sys_error("Failed to seek RAID metadata volume", dev_path);
			goto out;
		}

		sz = _get_sb_size(sb);
		memset((void *)((char *) sb + sz), 0, SB_BUFSZ - sz);
		_clear_failed_devices(sb);
		if (write(fd, sb, SB_BUFSZ) != SB_BUFSZ) {
			log_sys_error("Failed to clear RAID metadata volume", dev_path);
			goto out;
		}
	}

	r = 1;

out:
	if ((fd >= 0) && close(fd))
		log_sys_debug("close", dev_path);

	free(sb);

	return r;
}

int dm_raid_count_failed_devices(const char *dev_path, uint32_t *nr_failed)
{
	return _count_or_clear_failed_devices(dev_path, false, nr_failed);
}

int dm_raid_clear_failed_devices(const char *dev_path, uint32_t *nr_failed)
{
	return _count_or_clear_failed_devices(dev_path, true, nr_failed);
}