fs/ceph/mdsmap.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/ceph/ceph_debug.h>

 #include <linux/bug.h>
 #include <linux/err.h>
 #include <linux/random.h>
 #include <linux/slab.h>
 #include <linux/types.h>

 #include <linux/ceph/mdsmap.h>
 #include <linux/ceph/messenger.h>
 #include <linux/ceph/decode.h>

 #include "super.h"

 #define CEPH_MDS_IS_READY(i, ignore_laggy) \
 	(m->m_info[i].state > 0 && ignore_laggy ? true : !m->m_info[i].laggy)

 static int __mdsmap_get_random_mds(struct ceph_mdsmap *m, bool ignore_laggy)
 {
 	int n = 0;
 	int i, j;

 	/* count */
 	for (i = 0; i < m->possible_max_rank; i++)
 		if (CEPH_MDS_IS_READY(i, ignore_laggy))
 			n++;
 	if (n == 0)
 		return -1;

 	/* pick */
 	n = prandom_u32() % n;
 	for (j = 0, i = 0; i < m->possible_max_rank; i++) {
 		if (CEPH_MDS_IS_READY(i, ignore_laggy))
 			j++;
 		if (j > n)
 			break;
 	}

 	return i;
 }

 /*
  * choose a random mds that is "up" (i.e. has a state > 0), or -1.
  */
 int ceph_mdsmap_get_random_mds(struct ceph_mdsmap *m)
 {
 	int mds;

 	mds = __mdsmap_get_random_mds(m, false);
 	if (mds == m->possible_max_rank || mds == -1)
 		mds = __mdsmap_get_random_mds(m, true);

 	return mds == m->possible_max_rank ? -1 : mds;
 }

 #define __decode_and_drop_type(p, end, type, bad)		\
 	do {							\
 		if (*p + sizeof(type) > end)			\
 			goto bad;				\
 		*p += sizeof(type);				\
 	} while (0)

 #define __decode_and_drop_set(p, end, type, bad)		\
 	do {							\
 		u32 n;						\
 		size_t need;					\
 		ceph_decode_32_safe(p, end, n, bad);		\
 		need = sizeof(type) * n;			\
 		ceph_decode_need(p, end, need, bad);		\
 		*p += need;					\
 	} while (0)

 #define __decode_and_drop_map(p, end, ktype, vtype, bad)	\
 	do {							\
 		u32 n;						\
 		size_t need;					\
 		ceph_decode_32_safe(p, end, n, bad);		\
 		need = (sizeof(ktype) + sizeof(vtype)) * n;	\
 		ceph_decode_need(p, end, need, bad);		\
 		*p += need;					\
 	} while (0)


 static int __decode_and_drop_compat_set(void **p, void* end)
 {
 	int i;
 	/* compat, ro_compat, incompat*/
 	for (i = 0; i < 3; i++) {
 		u32 n;
 		ceph_decode_need(p, end, sizeof(u64) + sizeof(u32), bad);
 		/* mask */
 		*p += sizeof(u64);
 		/* names (map<u64, string>) */
 		n = ceph_decode_32(p);
 		while (n-- > 0) {
 			u32 len;
 			ceph_decode_need(p, end, sizeof(u64) + sizeof(u32),
 					 bad);
 			*p += sizeof(u64);
 			len = ceph_decode_32(p);
 			ceph_decode_need(p, end, len, bad);
 			*p += len;
 		}
 	}
 	return 0;
 bad:
 	return -1;
 }

 /*
  * Decode an MDS map
  *
  * Ignore any fields we don't care about (there are quite a few of
  * them).
  */
 struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
 {
 	struct ceph_mdsmap *m;
 	const void *start = *p;
 	int i, j, n;
 	int err;
 	u8 mdsmap_v;
 	u16 mdsmap_ev;
 	u32 target;

 	m = kzalloc(sizeof(*m), GFP_NOFS);
 	if (!m)
 		return ERR_PTR(-ENOMEM);

 	ceph_decode_need(p, end, 1 + 1, bad);
 	mdsmap_v = ceph_decode_8(p);
 	*p += sizeof(u8);			/* mdsmap_cv */
 	if (mdsmap_v >= 4) {
 	       u32 mdsmap_len;
 	       ceph_decode_32_safe(p, end, mdsmap_len, bad);
 	       if (end < *p + mdsmap_len)
 		       goto bad;
 	       end = *p + mdsmap_len;
 	}

 	ceph_decode_need(p, end, 8*sizeof(u32) + sizeof(u64), bad);
 	m->m_epoch = ceph_decode_32(p);
 	m->m_client_epoch = ceph_decode_32(p);
 	m->m_last_failure = ceph_decode_32(p);
 	m->m_root = ceph_decode_32(p);
 	m->m_session_timeout = ceph_decode_32(p);
 	m->m_session_autoclose = ceph_decode_32(p);
 	m->m_max_file_size = ceph_decode_64(p);
 	m->m_max_mds = ceph_decode_32(p);

 	/*
 	 * pick out the active nodes as the m_num_active_mds, the
 	 * m_num_active_mds maybe larger than m_max_mds when decreasing
 	 * the max_mds in cluster side, in other case it should less
 	 * than or equal to m_max_mds.
 	 */
 	m->m_num_active_mds = n = ceph_decode_32(p);

 	/*
 	 * the possible max rank, it maybe larger than the m_num_active_mds,
 	 * for example if the mds_max == 2 in the cluster, when the MDS(0)
 	 * was laggy and being replaced by a new MDS, we will temporarily
 	 * receive a new mds map with n_num_mds == 1 and the active MDS(1),
 	 * and the mds rank >= m_num_active_mds.
 	 */
 	m->possible_max_rank = max(m->m_num_active_mds, m->m_max_mds);

 	m->m_info = kcalloc(m->possible_max_rank, sizeof(*m->m_info), GFP_NOFS);
 	if (!m->m_info)
 		goto nomem;

 	/* pick out active nodes from mds_info (state > 0) */
 	for (i = 0; i < n; i++) {
 		u64 global_id;
 		u32 namelen;
 		s32 mds, inc, state;
 		u8 info_v;
 		void *info_end = NULL;
 		struct ceph_entity_addr addr;
 		u32 num_export_targets;
 		void *pexport_targets = NULL;
 		struct ceph_timespec laggy_since;
 		struct ceph_mds_info *info;
 		bool laggy;

 		ceph_decode_need(p, end, sizeof(u64) + 1, bad);
 		global_id = ceph_decode_64(p);
 		info_v= ceph_decode_8(p);
 		if (info_v >= 4) {
 			u32 info_len;
 			ceph_decode_need(p, end, 1 + sizeof(u32), bad);
 			*p += sizeof(u8);	/* info_cv */
 			info_len = ceph_decode_32(p);
 			info_end = *p + info_len;
 			if (info_end > end)
 				goto bad;
 		}

 		ceph_decode_need(p, end, sizeof(u64) + sizeof(u32), bad);
 		*p += sizeof(u64);
 		namelen = ceph_decode_32(p);  /* skip mds name */
 		*p += namelen;

 		ceph_decode_32_safe(p, end, mds, bad);
 		ceph_decode_32_safe(p, end, inc, bad);
 		ceph_decode_32_safe(p, end, state, bad);
 		*p += sizeof(u64);		/* state_seq */
 		if (info_v >= 8)
 			err = ceph_decode_entity_addrvec(p, end, msgr2, &addr);
 		else
 			err = ceph_decode_entity_addr(p, end, &addr);
 		if (err)
 			goto corrupt;

 		ceph_decode_copy_safe(p, end, &laggy_since, sizeof(laggy_since),
 				      bad);
 		laggy = laggy_since.tv_sec != 0 || laggy_since.tv_nsec != 0;
 		*p += sizeof(u32);
 		ceph_decode_32_safe(p, end, namelen, bad);
 		*p += namelen;
 		if (info_v >= 2) {
 			ceph_decode_32_safe(p, end, num_export_targets, bad);
 			pexport_targets = *p;
 			*p += num_export_targets * sizeof(u32);
 		} else {
 			num_export_targets = 0;
 		}

 		if (info_end && *p != info_end) {
 			if (*p > info_end)
 				goto bad;
 			*p = info_end;
 		}

 		dout("mdsmap_decode %d/%d %lld mds%d.%d %s %s%s\n",
 		     i+1, n, global_id, mds, inc,
 		     ceph_pr_addr(&addr),
 		     ceph_mds_state_name(state),
 		     laggy ? "(laggy)" : "");

 		if (mds < 0 || mds >= m->possible_max_rank) {
 			pr_warn("mdsmap_decode got incorrect mds(%d)\n", mds);
 			continue;
 		}

 		if (state <= 0) {
 			dout("mdsmap_decode got incorrect state(%s)\n",
 			     ceph_mds_state_name(state));
 			continue;
 		}

 		info = &m->m_info[mds];
 		info->global_id = global_id;
 		info->state = state;
 		info->addr = addr;
 		info->laggy = laggy;
 		info->num_export_targets = num_export_targets;
 		if (num_export_targets) {
 			info->export_targets = kcalloc(num_export_targets,
 						       sizeof(u32), GFP_NOFS);
 			if (!info->export_targets)
 				goto nomem;
 			for (j = 0; j < num_export_targets; j++) {
 				target = ceph_decode_32(&pexport_targets);
 				if (target >= m->possible_max_rank) {
 					err = -EIO;
 					goto corrupt;
 				}
 				info->export_targets[j] = target;
 			}
 		} else {
 			info->export_targets = NULL;
 		}
 	}

 	/* pg_pools */
 	ceph_decode_32_safe(p, end, n, bad);
 	m->m_num_data_pg_pools = n;
 	m->m_data_pg_pools = kcalloc(n, sizeof(u64), GFP_NOFS);
 	if (!m->m_data_pg_pools)
 		goto nomem;
 	ceph_decode_need(p, end, sizeof(u64)*(n+1), bad);
 	for (i = 0; i < n; i++)
 		m->m_data_pg_pools[i] = ceph_decode_64(p);
 	m->m_cas_pg_pool = ceph_decode_64(p);
 	m->m_enabled = m->m_epoch > 1;

 	mdsmap_ev = 1;
 	if (mdsmap_v >= 2) {
 		ceph_decode_16_safe(p, end, mdsmap_ev, bad_ext);
 	}
 	if (mdsmap_ev >= 3) {
 		if (__decode_and_drop_compat_set(p, end) < 0)
 			goto bad_ext;
 	}
 	/* metadata_pool */
 	if (mdsmap_ev < 5) {
 		__decode_and_drop_type(p, end, u32, bad_ext);
 	} else {
 		__decode_and_drop_type(p, end, u64, bad_ext);
 	}

 	/* created + modified + tableserver */
 	__decode_and_drop_type(p, end, struct ceph_timespec, bad_ext);
 	__decode_and_drop_type(p, end, struct ceph_timespec, bad_ext);
 	__decode_and_drop_type(p, end, u32, bad_ext);

 	/* in */
 	{
 		int num_laggy = 0;
 		ceph_decode_32_safe(p, end, n, bad_ext);
 		ceph_decode_need(p, end, sizeof(u32) * n, bad_ext);

 		for (i = 0; i < n; i++) {
 			s32 mds = ceph_decode_32(p);
 			if (mds >= 0 && mds < m->possible_max_rank) {
 				if (m->m_info[mds].laggy)
 					num_laggy++;
 			}
 		}
 		m->m_num_laggy = num_laggy;

 		if (n > m->possible_max_rank) {
 			void *new_m_info = krealloc(m->m_info,
 						    n * sizeof(*m->m_info),
 						    GFP_NOFS | __GFP_ZERO);
 			if (!new_m_info)
 				goto nomem;
 			m->m_info = new_m_info;
 		}
 		m->possible_max_rank = n;
 	}

 	/* inc */
 	__decode_and_drop_map(p, end, u32, u32, bad_ext);
 	/* up */
 	__decode_and_drop_map(p, end, u32, u64, bad_ext);
 	/* failed */
 	__decode_and_drop_set(p, end, u32, bad_ext);
 	/* stopped */
 	__decode_and_drop_set(p, end, u32, bad_ext);

 	if (mdsmap_ev >= 4) {
 		/* last_failure_osd_epoch */
 		__decode_and_drop_type(p, end, u32, bad_ext);
 	}
 	if (mdsmap_ev >= 6) {
 		/* ever_allowed_snaps */
 		__decode_and_drop_type(p, end, u8, bad_ext);
 		/* explicitly_allowed_snaps */
 		__decode_and_drop_type(p, end, u8, bad_ext);
 	}
 	if (mdsmap_ev >= 7) {
 		/* inline_data_enabled */
 		__decode_and_drop_type(p, end, u8, bad_ext);
 	}
 	if (mdsmap_ev >= 8) {
 		u32 name_len;
 		/* enabled */
 		ceph_decode_8_safe(p, end, m->m_enabled, bad_ext);
 		ceph_decode_32_safe(p, end, name_len, bad_ext);
 		ceph_decode_need(p, end, name_len, bad_ext);
 		*p += name_len;
 	}
 	/* damaged */
 	if (mdsmap_ev >= 9) {
 		size_t need;
 		ceph_decode_32_safe(p, end, n, bad_ext);
 		need = sizeof(u32) * n;
 		ceph_decode_need(p, end, need, bad_ext);
 		*p += need;
 		m->m_damaged = n > 0;
 	} else {
 		m->m_damaged = false;
 	}
 bad_ext:
 	dout("mdsmap_decode m_enabled: %d, m_damaged: %d, m_num_laggy: %d\n",
 	     !!m->m_enabled, !!m->m_damaged, m->m_num_laggy);
 	*p = end;
 	dout("mdsmap_decode success epoch %u\n", m->m_epoch);
 	return m;
 nomem:
 	err = -ENOMEM;
 	goto out_err;
 corrupt:
 	pr_err("corrupt mdsmap\n");
 	print_hex_dump(KERN_DEBUG, "mdsmap: ",
 		       DUMP_PREFIX_OFFSET, 16, 1,
 		       start, end - start, true);
 out_err:
 	ceph_mdsmap_destroy(m);
 	return ERR_PTR(err);
 bad:
 	err = -EINVAL;
 	goto corrupt;
 }

 void ceph_mdsmap_destroy(struct ceph_mdsmap *m)
 {
 	int i;

 	if (m->m_info) {
 		for (i = 0; i < m->possible_max_rank; i++)
 			kfree(m->m_info[i].export_targets);
 		kfree(m->m_info);
 	}
 	kfree(m->m_data_pg_pools);
 	kfree(m);
 }

 bool ceph_mdsmap_is_cluster_available(struct ceph_mdsmap *m)
 {
 	int i, nr_active = 0;
 	if (!m->m_enabled)
 		return false;
 	if (m->m_damaged)
 		return false;
 	if (m->m_num_laggy == m->m_num_active_mds)
 		return false;
 	for (i = 0; i < m->possible_max_rank; i++) {
 		if (m->m_info[i].state == CEPH_MDS_STATE_ACTIVE)
 			nr_active++;
 	}
 	return nr_active > 0;
 }
	// SPDX-License-Identifier: GPL-2.0
	#include <linux/ceph/ceph_debug.h>

	#include <linux/bug.h>
	#include <linux/err.h>
	#include <linux/random.h>
	#include <linux/slab.h>
	#include <linux/types.h>

	#include <linux/ceph/mdsmap.h>
	#include <linux/ceph/messenger.h>
	#include <linux/ceph/decode.h>

	#include "super.h"

	#define CEPH_MDS_IS_READY(i, ignore_laggy) \
	(m->m_info[i].state > 0 && ignore_laggy ? true : !m->m_info[i].laggy)

	static int __mdsmap_get_random_mds(struct ceph_mdsmap *m, bool ignore_laggy)
	{
	int n = 0;
	int i, j;

	/* count */
	for (i = 0; i < m->possible_max_rank; i++)
	if (CEPH_MDS_IS_READY(i, ignore_laggy))
	n++;
	if (n == 0)
	return -1;

	/* pick */
	n = prandom_u32() % n;
	for (j = 0, i = 0; i < m->possible_max_rank; i++) {
	if (CEPH_MDS_IS_READY(i, ignore_laggy))
	j++;
	if (j > n)
	break;
	}

	return i;
	}

	/*
	* choose a random mds that is "up" (i.e. has a state > 0), or -1.
	*/
	int ceph_mdsmap_get_random_mds(struct ceph_mdsmap *m)
	{
	int mds;

	mds = __mdsmap_get_random_mds(m, false);
	if (mds == m->possible_max_rank \|\| mds == -1)
	mds = __mdsmap_get_random_mds(m, true);

	return mds == m->possible_max_rank ? -1 : mds;
	}

	#define __decode_and_drop_type(p, end, type, bad) \
	do { \
	if (*p + sizeof(type) > end) \
	goto bad; \
	*p += sizeof(type); \
	} while (0)

	#define __decode_and_drop_set(p, end, type, bad) \
	do { \
	u32 n; \
	size_t need; \
	ceph_decode_32_safe(p, end, n, bad); \
	need = sizeof(type) * n; \
	ceph_decode_need(p, end, need, bad); \
	*p += need; \
	} while (0)

	#define __decode_and_drop_map(p, end, ktype, vtype, bad) \
	do { \
	u32 n; \
	size_t need; \
	ceph_decode_32_safe(p, end, n, bad); \
	need = (sizeof(ktype) + sizeof(vtype)) * n; \
	ceph_decode_need(p, end, need, bad); \
	*p += need; \
	} while (0)


	static int __decode_and_drop_compat_set(void *p, void end)
	{
	int i;
	/* compat, ro_compat, incompat*/
	for (i = 0; i < 3; i++) {
	u32 n;
	ceph_decode_need(p, end, sizeof(u64) + sizeof(u32), bad);
	/* mask */
	*p += sizeof(u64);
	/* names (map<u64, string>) */
	n = ceph_decode_32(p);
	while (n-- > 0) {
	u32 len;
	ceph_decode_need(p, end, sizeof(u64) + sizeof(u32),
	bad);
	*p += sizeof(u64);
	len = ceph_decode_32(p);
	ceph_decode_need(p, end, len, bad);
	*p += len;
	}
	}
	return 0;
	bad:
	return -1;
	}

	/*
	* Decode an MDS map
	*
	* Ignore any fields we don't care about (there are quite a few of
	* them).
	*/
	struct ceph_mdsmap ceph_mdsmap_decode(void p, void end, bool msgr2)
	{
	struct ceph_mdsmap *m;
	const void start = p;
	int i, j, n;
	int err;
	u8 mdsmap_v;
	u16 mdsmap_ev;
	u32 target;

	m = kzalloc(sizeof(*m), GFP_NOFS);
	if (!m)
	return ERR_PTR(-ENOMEM);

	ceph_decode_need(p, end, 1 + 1, bad);
	mdsmap_v = ceph_decode_8(p);
	p += sizeof(u8); / mdsmap_cv */
	if (mdsmap_v >= 4) {
	u32 mdsmap_len;
	ceph_decode_32_safe(p, end, mdsmap_len, bad);
	if (end < *p + mdsmap_len)
	goto bad;
	end = *p + mdsmap_len;
	}

	ceph_decode_need(p, end, 8*sizeof(u32) + sizeof(u64), bad);
	m->m_epoch = ceph_decode_32(p);
	m->m_client_epoch = ceph_decode_32(p);
	m->m_last_failure = ceph_decode_32(p);
	m->m_root = ceph_decode_32(p);
	m->m_session_timeout = ceph_decode_32(p);
	m->m_session_autoclose = ceph_decode_32(p);
	m->m_max_file_size = ceph_decode_64(p);
	m->m_max_mds = ceph_decode_32(p);

	/*
	* pick out the active nodes as the m_num_active_mds, the
	* m_num_active_mds maybe larger than m_max_mds when decreasing
	* the max_mds in cluster side, in other case it should less
	* than or equal to m_max_mds.
	*/
	m->m_num_active_mds = n = ceph_decode_32(p);

	/*
	* the possible max rank, it maybe larger than the m_num_active_mds,
	* for example if the mds_max == 2 in the cluster, when the MDS(0)
	* was laggy and being replaced by a new MDS, we will temporarily
	* receive a new mds map with n_num_mds == 1 and the active MDS(1),
	* and the mds rank >= m_num_active_mds.
	*/
	m->possible_max_rank = max(m->m_num_active_mds, m->m_max_mds);

	m->m_info = kcalloc(m->possible_max_rank, sizeof(*m->m_info), GFP_NOFS);
	if (!m->m_info)
	goto nomem;

	/* pick out active nodes from mds_info (state > 0) */
	for (i = 0; i < n; i++) {
	u64 global_id;
	u32 namelen;
	s32 mds, inc, state;
	u8 info_v;
	void *info_end = NULL;
	struct ceph_entity_addr addr;
	u32 num_export_targets;
	void *pexport_targets = NULL;
	struct ceph_timespec laggy_since;
	struct ceph_mds_info *info;
	bool laggy;

	ceph_decode_need(p, end, sizeof(u64) + 1, bad);
	global_id = ceph_decode_64(p);
	info_v= ceph_decode_8(p);
	if (info_v >= 4) {
	u32 info_len;
	ceph_decode_need(p, end, 1 + sizeof(u32), bad);
	p += sizeof(u8); / info_cv */
	info_len = ceph_decode_32(p);
	info_end = *p + info_len;
	if (info_end > end)
	goto bad;
	}

	ceph_decode_need(p, end, sizeof(u64) + sizeof(u32), bad);
	*p += sizeof(u64);
	namelen = ceph_decode_32(p); /* skip mds name */
	*p += namelen;

	ceph_decode_32_safe(p, end, mds, bad);
	ceph_decode_32_safe(p, end, inc, bad);
	ceph_decode_32_safe(p, end, state, bad);
	p += sizeof(u64); / state_seq */
	if (info_v >= 8)
	err = ceph_decode_entity_addrvec(p, end, msgr2, &addr);
	else
	err = ceph_decode_entity_addr(p, end, &addr);
	if (err)
	goto corrupt;

	ceph_decode_copy_safe(p, end, &laggy_since, sizeof(laggy_since),
	bad);
	laggy = laggy_since.tv_sec != 0 \|\| laggy_since.tv_nsec != 0;
	*p += sizeof(u32);
	ceph_decode_32_safe(p, end, namelen, bad);
	*p += namelen;
	if (info_v >= 2) {
	ceph_decode_32_safe(p, end, num_export_targets, bad);
	pexport_targets = *p;
	p += num_export_targets sizeof(u32);
	} else {
	num_export_targets = 0;
	}

	if (info_end && *p != info_end) {
	if (*p > info_end)
	goto bad;
	*p = info_end;
	}

	dout("mdsmap_decode %d/%d %lld mds%d.%d %s %s%s\n",
	i+1, n, global_id, mds, inc,
	ceph_pr_addr(&addr),
	ceph_mds_state_name(state),
	laggy ? "(laggy)" : "");

	if (mds < 0 \|\| mds >= m->possible_max_rank) {
	pr_warn("mdsmap_decode got incorrect mds(%d)\n", mds);
	continue;
	}

	if (state <= 0) {
	dout("mdsmap_decode got incorrect state(%s)\n",
	ceph_mds_state_name(state));
	continue;
	}

	info = &m->m_info[mds];
	info->global_id = global_id;
	info->state = state;
	info->addr = addr;
	info->laggy = laggy;
	info->num_export_targets = num_export_targets;
	if (num_export_targets) {
	info->export_targets = kcalloc(num_export_targets,
	sizeof(u32), GFP_NOFS);
	if (!info->export_targets)
	goto nomem;
	for (j = 0; j < num_export_targets; j++) {
	target = ceph_decode_32(&pexport_targets);
	if (target >= m->possible_max_rank) {
	err = -EIO;
	goto corrupt;
	}
	info->export_targets[j] = target;
	}
	} else {
	info->export_targets = NULL;
	}
	}

	/* pg_pools */
	ceph_decode_32_safe(p, end, n, bad);
	m->m_num_data_pg_pools = n;
	m->m_data_pg_pools = kcalloc(n, sizeof(u64), GFP_NOFS);
	if (!m->m_data_pg_pools)
	goto nomem;
	ceph_decode_need(p, end, sizeof(u64)*(n+1), bad);
	for (i = 0; i < n; i++)
	m->m_data_pg_pools[i] = ceph_decode_64(p);
	m->m_cas_pg_pool = ceph_decode_64(p);
	m->m_enabled = m->m_epoch > 1;

	mdsmap_ev = 1;
	if (mdsmap_v >= 2) {
	ceph_decode_16_safe(p, end, mdsmap_ev, bad_ext);
	}
	if (mdsmap_ev >= 3) {
	if (__decode_and_drop_compat_set(p, end) < 0)
	goto bad_ext;
	}
	/* metadata_pool */
	if (mdsmap_ev < 5) {
	__decode_and_drop_type(p, end, u32, bad_ext);
	} else {
	__decode_and_drop_type(p, end, u64, bad_ext);
	}

	/* created + modified + tableserver */
	__decode_and_drop_type(p, end, struct ceph_timespec, bad_ext);
	__decode_and_drop_type(p, end, struct ceph_timespec, bad_ext);
	__decode_and_drop_type(p, end, u32, bad_ext);

	/* in */
	{
	int num_laggy = 0;
	ceph_decode_32_safe(p, end, n, bad_ext);
	ceph_decode_need(p, end, sizeof(u32) * n, bad_ext);

	for (i = 0; i < n; i++) {
	s32 mds = ceph_decode_32(p);
	if (mds >= 0 && mds < m->possible_max_rank) {
	if (m->m_info[mds].laggy)
	num_laggy++;
	}
	}
	m->m_num_laggy = num_laggy;

	if (n > m->possible_max_rank) {
	void *new_m_info = krealloc(m->m_info,
	n * sizeof(*m->m_info),
	GFP_NOFS \| __GFP_ZERO);
	if (!new_m_info)
	goto nomem;
	m->m_info = new_m_info;
	}
	m->possible_max_rank = n;
	}

	/* inc */
	__decode_and_drop_map(p, end, u32, u32, bad_ext);
	/* up */
	__decode_and_drop_map(p, end, u32, u64, bad_ext);
	/* failed */
	__decode_and_drop_set(p, end, u32, bad_ext);
	/* stopped */
	__decode_and_drop_set(p, end, u32, bad_ext);

	if (mdsmap_ev >= 4) {
	/* last_failure_osd_epoch */
	__decode_and_drop_type(p, end, u32, bad_ext);
	}
	if (mdsmap_ev >= 6) {
	/* ever_allowed_snaps */
	__decode_and_drop_type(p, end, u8, bad_ext);
	/* explicitly_allowed_snaps */
	__decode_and_drop_type(p, end, u8, bad_ext);
	}
	if (mdsmap_ev >= 7) {
	/* inline_data_enabled */
	__decode_and_drop_type(p, end, u8, bad_ext);
	}
	if (mdsmap_ev >= 8) {
	u32 name_len;
	/* enabled */
	ceph_decode_8_safe(p, end, m->m_enabled, bad_ext);
	ceph_decode_32_safe(p, end, name_len, bad_ext);
	ceph_decode_need(p, end, name_len, bad_ext);
	*p += name_len;
	}
	/* damaged */
	if (mdsmap_ev >= 9) {
	size_t need;
	ceph_decode_32_safe(p, end, n, bad_ext);
	need = sizeof(u32) * n;
	ceph_decode_need(p, end, need, bad_ext);
	*p += need;
	m->m_damaged = n > 0;
	} else {
	m->m_damaged = false;
	}
	bad_ext:
	dout("mdsmap_decode m_enabled: %d, m_damaged: %d, m_num_laggy: %d\n",
	!!m->m_enabled, !!m->m_damaged, m->m_num_laggy);
	*p = end;
	dout("mdsmap_decode success epoch %u\n", m->m_epoch);
	return m;
	nomem:
	err = -ENOMEM;
	goto out_err;
	corrupt:
	pr_err("corrupt mdsmap\n");
	print_hex_dump(KERN_DEBUG, "mdsmap: ",
	DUMP_PREFIX_OFFSET, 16, 1,
	start, end - start, true);
	out_err:
	ceph_mdsmap_destroy(m);
	return ERR_PTR(err);
	bad:
	err = -EINVAL;
	goto corrupt;
	}

	void ceph_mdsmap_destroy(struct ceph_mdsmap *m)
	{
	int i;

	if (m->m_info) {
	for (i = 0; i < m->possible_max_rank; i++)
	kfree(m->m_info[i].export_targets);
	kfree(m->m_info);
	}
	kfree(m->m_data_pg_pools);
	kfree(m);
	}

	bool ceph_mdsmap_is_cluster_available(struct ceph_mdsmap *m)
	{
	int i, nr_active = 0;
	if (!m->m_enabled)
	return false;
	if (m->m_damaged)
	return false;
	if (m->m_num_laggy == m->m_num_active_mds)
	return false;
	for (i = 0; i < m->possible_max_rank; i++) {
	if (m->m_info[i].state == CEPH_MDS_STATE_ACTIVE)
	nr_active++;
	}
	return nr_active > 0;
	}