/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will 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 version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2014, Intel Corporation.
 *
 * Copyright 2017 Cray Inc, all rights reserved.
 * Author: Ben Evans.
 *
 * Store PID->JobID mappings
 */

#define DEBUG_SUBSYSTEM S_RPC
#include <linux/user_namespace.h>
#ifdef HAVE_UIDGID_HEADER
#include <linux/uidgid.h>
#endif
#include <linux/utsname.h>

#include <libcfs/linux/linux-misc.h>
#include <obd_support.h>
#include <obd_class.h>
#include <lustre_net.h>

static struct cfs_hash *jobid_hash;
static struct cfs_hash_ops jobid_hash_ops;
spinlock_t jobid_hash_lock;

#define RESCAN_INTERVAL 30
#define DELETE_INTERVAL 300

char obd_jobid_var[JOBSTATS_JOBID_VAR_MAX_LEN + 1] = JOBSTATS_DISABLE;
char obd_jobid_name[LUSTRE_JOBID_SIZE] = "%e.%u";

/**
 * Structure to store a single PID->JobID mapping
 */
struct jobid_pid_map {
	struct hlist_node	jp_hash;
	time64_t		jp_time;
	spinlock_t		jp_lock; /* protects jp_jobid */
	char			jp_jobid[LUSTRE_JOBID_SIZE];
	unsigned int		jp_joblen;
	atomic_t		jp_refcount;
	pid_t			jp_pid;
};

/*
 * Get jobid of current process by reading the environment variable
 * stored in between the "env_start" & "env_end" of task struct.
 *
 * If some job scheduler doesn't store jobid in the "env_start/end",
 * then an upcall could be issued here to get the jobid by utilizing
 * the userspace tools/API. Then, the jobid must be cached.
 */
int jobid_get_from_environ(char *jobid_var, char *jobid, int *jobid_len)
{
	static bool printed;
	int rc;

	rc = cfs_get_environ(jobid_var, jobid, jobid_len);
	if (!rc)
		goto out;

	if (unlikely(rc == -EOVERFLOW && !printed)) {
		/* For the PBS_JOBID and LOADL_STEP_ID keys (which are
		 * variable length strings instead of just numbers), it
		 * might make sense to keep the unique parts for JobID,
		 * instead of just returning an error.  That means a
		 * larger temp buffer for cfs_get_environ(), then
		 * truncating the string at some separator to fit into
		 * the specified jobid_len.  Fix later if needed. */
		LCONSOLE_ERROR_MSG(0x16b,
				   "jobid: '%s' value too large (%d)\n",
				   obd_jobid_var, *jobid_len);
		printed = true;
		rc = 0;
	}
	if (rc) {
		CDEBUG((rc == -ENOENT || rc == -EINVAL ||
			rc == -EDEADLK) ? D_INFO : D_ERROR,
		       "jobid: get '%s' failed: rc = %d\n",
		       obd_jobid_var, rc);
	}

out:
	return rc;
}

/*
 * jobid_should_free_item
 *
 * Each item is checked to see if it should be released
 * Removed from hash table by caller
 * Actually freed in jobid_put_locked
 *
 * Returns 1 if item is to be freed, 0 if it is to be kept
 */

static int jobid_should_free_item(void *obj, void *data)
{
	char *jobid = data;
	struct jobid_pid_map *pidmap = obj;
	int rc = 0;

	if (obj == NULL)
		return 0;

	spin_lock(&pidmap->jp_lock);
	if (jobid == NULL)
		rc = 1;
	else if (jobid[0] == '\0')
		rc = 1;
	else if (ktime_get_real_seconds() - pidmap->jp_time > DELETE_INTERVAL)
		rc = 1;
	else if (strcmp(pidmap->jp_jobid, jobid) == 0)
		rc = 1;
	spin_unlock(&pidmap->jp_lock);

	return rc;
}

/*
 * jobid_name_is_valid
 *
 * Checks if the jobid is a Lustre process
 *
 * Returns true if jobid is valid
 * Returns false if jobid looks like it's a Lustre process
 */
static bool jobid_name_is_valid(char *jobid)
{
	const char *const lustre_reserved[] = { "ll_ping", "ptlrpc",
						"ldlm", "ll_sa", NULL };
	int i;

	if (jobid[0] == '\0')
		return false;

	for (i = 0; lustre_reserved[i] != NULL; i++) {
		if (strncmp(jobid, lustre_reserved[i],
			    strlen(lustre_reserved[i])) == 0)
			return false;
	}
	return true;
}

/*
 * jobid_get_from_cache()
 *
 * Returns contents of jobid_var from process environment for current PID.
 * This will be cached for some time to avoid overhead scanning environment.
 *
 * Return: -ENOMEM if allocating a new pidmap fails
 *         -ENOENT if no entry could be found
 *         +ve string length for success (something was returned in jobid)
 */
static int jobid_get_from_cache(char *jobid, size_t joblen)
{
	static time64_t last_expire;
	bool expire_cache = false;
	pid_t pid = current_pid();
	struct jobid_pid_map *pidmap = NULL;
	time64_t now = ktime_get_real_seconds();
	int rc = 0;
	ENTRY;

	LASSERT(jobid_hash != NULL);

	/* scan hash periodically to remove old PID entries from cache */
	spin_lock(&jobid_hash_lock);
	if (unlikely(last_expire + DELETE_INTERVAL <= now)) {
		expire_cache = true;
		last_expire = now;
	}
	spin_unlock(&jobid_hash_lock);

	if (expire_cache)
		cfs_hash_cond_del(jobid_hash, jobid_should_free_item,
				  "intentionally_bad_jobid");

	/* first try to find PID in the hash and use that value */
	pidmap = cfs_hash_lookup(jobid_hash, &pid);
	if (pidmap == NULL) {
		struct jobid_pid_map *pidmap2;

		OBD_ALLOC_PTR(pidmap);
		if (pidmap == NULL)
			GOTO(out, rc = -ENOMEM);

		pidmap->jp_pid = pid;
		pidmap->jp_time = 0;
		pidmap->jp_jobid[0] = '\0';
		spin_lock_init(&pidmap->jp_lock);
		INIT_HLIST_NODE(&pidmap->jp_hash);

		/*
		 * Add the newly created map to the hash, on key collision we
		 * lost a racing addition and must destroy our newly allocated
		 * map.  The object which exists in the hash will be returned.
		 */
		pidmap2 = cfs_hash_findadd_unique(jobid_hash, &pid,
						  &pidmap->jp_hash);
		if (unlikely(pidmap != pidmap2)) {
			CDEBUG(D_INFO, "jobid: duplicate found for PID=%u\n",
			       pid);
			OBD_FREE_PTR(pidmap);
			pidmap = pidmap2;
		} else {
			cfs_hash_get(jobid_hash, &pidmap->jp_hash);
		}
	}

	/*
	 * If pidmap is old (this is always true for new entries) refresh it.
	 * If obd_jobid_var is not found, cache empty entry and try again
	 * later, to avoid repeat lookups for PID if obd_jobid_var missing.
	 */
	spin_lock(&pidmap->jp_lock);
	if (pidmap->jp_time + RESCAN_INTERVAL <= now) {
		char env_jobid[LUSTRE_JOBID_SIZE] = "";
		int env_len = sizeof(env_jobid);

		pidmap->jp_time = now;

		spin_unlock(&pidmap->jp_lock);
		rc = jobid_get_from_environ(obd_jobid_var, env_jobid, &env_len);

		CDEBUG(D_INFO, "jobid: PID mapping established: %d->%s\n",
		       pidmap->jp_pid, env_jobid);
		spin_lock(&pidmap->jp_lock);
		if (!rc) {
			pidmap->jp_joblen = env_len;
			strlcpy(pidmap->jp_jobid, env_jobid,
				sizeof(pidmap->jp_jobid));
			rc = 0;
		} else if (rc == -ENOENT) {
			/* It might have been deleted, clear out old entry */
			pidmap->jp_joblen = 0;
			pidmap->jp_jobid[0] = '\0';
		}
	}

	/*
	 * Regardless of how pidmap was found, if it contains a valid entry
	 * use that for now.  If there was a technical error (e.g. -ENOMEM)
	 * use the old cached value until it can be looked up again properly.
	 * If a cached missing entry was found, return -ENOENT.
	 */
	if (pidmap->jp_joblen) {
		strlcpy(jobid, pidmap->jp_jobid, joblen);
		joblen = pidmap->jp_joblen;
		rc = 0;
	} else if (!rc) {
		rc = -ENOENT;
	}
	spin_unlock(&pidmap->jp_lock);

	cfs_hash_put(jobid_hash, &pidmap->jp_hash);

	EXIT;
out:
	return rc < 0 ? rc : joblen;
}

/*
 * jobid_interpret_string()
 *
 * Interpret the jobfmt string to expand specified fields, like coredumps do:
 *   %e = executable
 *   %g = gid
 *   %h = hostname
 *   %j = jobid from environment
 *   %p = pid
 *   %u = uid
 *
 * Unknown escape strings are dropped.  Other characters are copied through,
 * excluding whitespace (to avoid making jobid parsing difficult).
 *
 * Return: -EOVERFLOW if the expanded string does not fit within @joblen
 *         0 for success
 */
static int jobid_interpret_string(const char *jobfmt, char *jobid,
				  ssize_t joblen)
{
	char c;

	while ((c = *jobfmt++) && joblen > 1) {
		char f;
		int l;

		if (isspace(c)) /* Don't allow embedded spaces */
			continue;

		if (c != '%') {
			*jobid = c;
			joblen--;
			jobid++;
			continue;
		}

		switch ((f = *jobfmt++)) {
		case 'e': /* executable name */
			l = snprintf(jobid, joblen, "%s", current_comm());
			break;
		case 'g': /* group ID */
			l = snprintf(jobid, joblen, "%u",
				     from_kgid(&init_user_ns, current_fsgid()));
			break;
		case 'h': /* hostname */
			l = snprintf(jobid, joblen, "%s",
				     init_utsname()->nodename);
			break;
		case 'j': /* jobid stored in process environment */
			l = jobid_get_from_cache(jobid, joblen);
			if (l < 0)
				l = 0;
			break;
		case 'p': /* process ID */
			l = snprintf(jobid, joblen, "%u", current_pid());
			break;
		case 'u': /* user ID */
			l = snprintf(jobid, joblen, "%u",
				     from_kuid(&init_user_ns, current_fsuid()));
			break;
		case '\0': /* '%' at end of format string */
			l = 0;
			goto out;
		default: /* drop unknown %x format strings */
			l = 0;
			break;
		}
		jobid += l;
		joblen -= l;
	}
	/*
	 * This points at the end of the buffer, so long as jobid is always
	 * incremented the same amount as joblen is decremented.
	 */
out:
	jobid[joblen - 1] = '\0';

	return joblen < 0 ? -EOVERFLOW : 0;
}

/*
 * Hash initialization, copied from server-side job stats bucket sizes
 */
#define HASH_JOBID_BKT_BITS 5
#define HASH_JOBID_CUR_BITS 7
#define HASH_JOBID_MAX_BITS 12

int jobid_cache_init(void)
{
	int rc = 0;
	ENTRY;

	if (jobid_hash)
		return 0;

	spin_lock_init(&jobid_hash_lock);
	jobid_hash = cfs_hash_create("JOBID_HASH", HASH_JOBID_CUR_BITS,
				     HASH_JOBID_MAX_BITS, HASH_JOBID_BKT_BITS,
				     0, CFS_HASH_MIN_THETA, CFS_HASH_MAX_THETA,
				     &jobid_hash_ops, CFS_HASH_DEFAULT);
	if (!jobid_hash)
		rc = -ENOMEM;

	RETURN(rc);
}
EXPORT_SYMBOL(jobid_cache_init);

void jobid_cache_fini(void)
{
	struct cfs_hash *tmp_hash;
	ENTRY;

	spin_lock(&jobid_hash_lock);
	tmp_hash = jobid_hash;
	jobid_hash = NULL;
	spin_unlock(&jobid_hash_lock);

	if (tmp_hash != NULL) {
		cfs_hash_cond_del(tmp_hash, jobid_should_free_item, NULL);
		cfs_hash_putref(tmp_hash);
	}

	EXIT;
}
EXPORT_SYMBOL(jobid_cache_fini);

/*
 * Hash operations for pid<->jobid
 */
static unsigned jobid_hashfn(struct cfs_hash *hs, const void *key,
			     unsigned mask)
{
	return cfs_hash_djb2_hash(key, sizeof(pid_t), mask);
}

static void *jobid_key(struct hlist_node *hnode)
{
	struct jobid_pid_map *pidmap;

	pidmap = hlist_entry(hnode, struct jobid_pid_map, jp_hash);
	return &pidmap->jp_pid;
}

static int jobid_keycmp(const void *key, struct hlist_node *hnode)
{
	const pid_t *pid_key1;
	const pid_t *pid_key2;

	LASSERT(key != NULL);
	pid_key1 = (pid_t *)key;
	pid_key2 = (pid_t *)jobid_key(hnode);

	return *pid_key1 == *pid_key2;
}

static void *jobid_object(struct hlist_node *hnode)
{
	return hlist_entry(hnode, struct jobid_pid_map, jp_hash);
}

static void jobid_get(struct cfs_hash *hs, struct hlist_node *hnode)
{
	struct jobid_pid_map *pidmap;

	pidmap = hlist_entry(hnode, struct jobid_pid_map, jp_hash);

	atomic_inc(&pidmap->jp_refcount);
}

static void jobid_put_locked(struct cfs_hash *hs, struct hlist_node *hnode)
{
	struct jobid_pid_map *pidmap;

	if (hnode == NULL)
		return;

	pidmap = hlist_entry(hnode, struct jobid_pid_map, jp_hash);
	LASSERT(atomic_read(&pidmap->jp_refcount) > 0);
	if (atomic_dec_and_test(&pidmap->jp_refcount)) {
		CDEBUG(D_INFO, "Freeing: %d->%s\n",
		       pidmap->jp_pid, pidmap->jp_jobid);

		OBD_FREE_PTR(pidmap);
	}
}

static struct cfs_hash_ops jobid_hash_ops = {
	.hs_hash	= jobid_hashfn,
	.hs_keycmp	= jobid_keycmp,
	.hs_key		= jobid_key,
	.hs_object	= jobid_object,
	.hs_get		= jobid_get,
	.hs_put		= jobid_put_locked,
	.hs_put_locked	= jobid_put_locked,
};

/**
 * Generate the job identifier string for this process for tracking purposes.
 *
 * Fill in @jobid string based on the value of obd_jobid_var:
 * JOBSTATS_DISABLE:      none
 * JOBSTATS_NODELOCAL:    content of obd_jobid_node (jobid_interpret_string())
 * JOBSTATS_PROCNAME_UID: process name/UID
 * anything else:         look up obd_jobid_var in the processes environment
 *
 * Return -ve error number, 0 on success.
 */
int lustre_get_jobid(char *jobid, size_t joblen)
{
	int rc = 0;
	ENTRY;

	if (unlikely(joblen < 2)) {
		if (joblen == 1)
			jobid[0] = '\0';
		RETURN(-EINVAL);
	}

	if (strcmp(obd_jobid_var, JOBSTATS_DISABLE) == 0) {
		/* Jobstats isn't enabled */
		memset(jobid, 0, joblen);
	} else if (strcmp(obd_jobid_var, JOBSTATS_NODELOCAL) == 0) {
		/* Whole node dedicated to single job */
		rc = jobid_interpret_string(obd_jobid_name, jobid, joblen);
	} else if (strcmp(obd_jobid_var, JOBSTATS_PROCNAME_UID) == 0) {
		rc = jobid_interpret_string("%e.%u", jobid, joblen);
	} else if (jobid_name_is_valid(current_comm())) {
		/*
		 * obd_jobid_var holds the jobid environment variable name.
		 * Skip initial check if obd_jobid_name already uses "%j",
		 * otherwise try just "%j" first, then fall back to whatever
		 * is in obd_jobid_name if obd_jobid_var is not found.
		 */
		rc = -EAGAIN;
		if (!strnstr(obd_jobid_name, "%j", joblen))
			rc = jobid_get_from_cache(jobid, joblen);

		/* fall back to jobid_node if jobid_var not in environment */
		if (rc < 0) {
			int rc2 = jobid_interpret_string(obd_jobid_name,
							 jobid, joblen);
			if (!rc2)
				rc = 0;
		}
	}

	RETURN(rc);
}
EXPORT_SYMBOL(lustre_get_jobid);

/*
 * lustre_jobid_clear
 *
 * Search cache for JobID given by @find_jobid.
 * If any entries in the hash table match the value, they are removed
 */
void lustre_jobid_clear(const char *find_jobid)
{
	char jobid[LUSTRE_JOBID_SIZE];
	char *end;

	if (jobid_hash == NULL)
		return;

	strlcpy(jobid, find_jobid, sizeof(jobid));
	/* trim \n off the end of the incoming jobid */
	end = strchr(jobid, '\n');
	if (end && *end == '\n')
		*end = '\0';

	CDEBUG(D_INFO, "Clearing Jobid: %s\n", jobid);
	cfs_hash_cond_del(jobid_hash, jobid_should_free_item, jobid);

	CDEBUG(D_INFO, "%d items remain in jobID table\n",
	       atomic_read(&jobid_hash->hs_count));
}