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23 * Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
24 * Use is subject to license terms.
26 * Copyright (c) 2012, 2017, Intel Corporation.
29 * This file is part of Lustre, http://www.lustre.org/
31 * lustre/ofd/ofd_dlm.c
33 * This file contains OBD Filter Device (OFD) LDLM-related code which is just
34 * intent handling for glimpse lock.
36 * Author: Andreas Dilger <andreas.dilger@intel.com>
37 * Author: Jinshan Xiong <jinshan.xiong@intel.com>
38 * Author: Alexey Zhuravlev <alexey.zhuravlev@intel.com>
39 * Author: Mikhail Pershin <mike.pershin@intel.com>
42 #define DEBUG_SUBSYSTEM S_FILTER
44 #include "ofd_internal.h"
46 struct ofd_intent_args {
47 struct list_head gl_list;
54 * OFD interval callback.
56 * The interval_callback_t is part of interval_iterate_reverse() and is called
57 * for each interval in tree. The OFD interval callback searches for locks
58 * covering extents beyond the given args->size. This is used to decide if the
59 * size is too small and needs to be updated. Note that we are only interested
60 * in growing the size, as truncate is the only operation which can shrink it,
61 * and it is handled differently. This is why we only look at locks beyond the
64 * It finds the highest lock (by starting point) in this interval, and adds it
65 * to the list of locks to glimpse. We must glimpse a list of locks - rather
66 * than only the highest lock on the file - because lockahead creates extent
67 * locks in advance of IO, and so breaks the assumption that the holder of the
68 * highest lock knows the current file size.
70 * This assumption is normally true because locks which are created as part of
71 * IO - rather than in advance of it - are guaranteed to be 'active', i.e.,
72 * involved in IO, and the holder of the highest 'active' lock always knows the
73 * current file size, because the size is either not changing or the holder of
74 * that lock is responsible for updating it.
76 * So we need only glimpse until we find the first client with an 'active'
79 * Unfortunately, there is no way to know if a manually requested/speculative
80 * lock is 'active' from the server side. So when we see a potentially
81 * speculative lock, we must send a glimpse for that lock unless we have
82 * already sent a glimpse to the holder of that lock.
84 * However, *all* non-speculative locks are active. So we can stop glimpsing
85 * as soon as we find a non-speculative lock. Currently, all speculative PW
86 * locks have LDLM_FL_NO_EXPANSION set, and we use this to identify them. This
87 * is enforced by an assertion in osc_lock_init, which references this comment.
89 * If that ever changes, we will either need to find a new way to identify
90 * active locks or we will need to consider all PW locks (we will still only
91 * glimpse one per client).
93 * Note that it is safe to glimpse only the 'top' lock from each interval
94 * because ofd_intent_cb is only called for PW extent locks, and for PW locks,
95 * there is only one lock per interval.
97 * \param[in] n interval node
98 * \param[in,out] args intent arguments, gl work list for identified locks
100 * \retval INTERVAL_ITER_STOP if the interval is lower than
101 * file size, caller stops execution
102 * \retval INTERVAL_ITER_CONT if callback finished successfully
103 * and caller may continue execution
105 static enum interval_iter ofd_intent_cb(struct interval_node *n, void *args)
107 struct ldlm_interval *node = (struct ldlm_interval *)n;
108 struct ofd_intent_args *arg = args;
109 __u64 size = arg->size;
110 struct ldlm_lock *victim_lock = NULL;
111 struct ldlm_lock *lck;
112 struct ldlm_glimpse_work *gl_work = NULL;
115 /* If the interval is lower than the current file size, just break. */
116 if (interval_high(n) <= size)
117 GOTO(out, rc = INTERVAL_ITER_STOP);
119 /* Find the 'victim' lock from this interval */
120 list_for_each_entry(lck, &node->li_group, l_sl_policy) {
121 victim_lock = LDLM_LOCK_GET(lck);
123 /* the same policy group - every lock has the
124 * same extent, so needn't do it any more */
128 /* l_export can be null in race with eviction - In that case, we will
129 * not find any locks in this interval */
131 GOTO(out, rc = INTERVAL_ITER_CONT);
134 * This check is for lock taken in ofd_destroy_by_fid() that does
135 * not have l_glimpse_ast set. So the logic is: if there is a lock
136 * with no l_glimpse_ast set, this object is being destroyed already.
137 * Hence, if you are grabbing DLM locks on the server, always set
138 * non-NULL glimpse_ast (e.g., ldlm_request.c::ldlm_glimpse_ast()).
140 if (victim_lock->l_glimpse_ast == NULL) {
141 LDLM_DEBUG(victim_lock, "no l_glimpse_ast");
142 arg->no_glimpse_ast = true;
143 GOTO(out_release, rc = INTERVAL_ITER_STOP);
146 /* If NO_EXPANSION is not set, this is an active lock, and we don't need
147 * to glimpse any further once we've glimpsed the client holding this
148 * lock. So set us up to stop. See comment above this function. */
149 if (!(victim_lock->l_flags & LDLM_FL_NO_EXPANSION))
150 rc = INTERVAL_ITER_STOP;
152 rc = INTERVAL_ITER_CONT;
154 /* Check to see if we're already set up to send a glimpse to this
155 * client; if so, don't add this lock to the glimpse list - We need
156 * only glimpse each client once. (And if we know that client holds
157 * an active lock, we can stop glimpsing. So keep the rc set in the
159 list_for_each_entry(gl_work, &arg->gl_list, gl_list) {
160 if (gl_work->gl_lock->l_export == victim_lock->l_export)
161 GOTO(out_release, rc);
164 if (!OBD_FAIL_CHECK(OBD_FAIL_OST_GL_WORK_ALLOC))
165 OBD_SLAB_ALLOC_PTR_GFP(gl_work, ldlm_glimpse_work_kmem,
169 arg->error = -ENOMEM;
170 GOTO(out_release, rc = INTERVAL_ITER_STOP);
173 /* Populate the gl_work structure. */
174 gl_work->gl_lock = victim_lock;
175 list_add_tail(&gl_work->gl_list, &arg->gl_list);
176 /* There is actually no need for a glimpse descriptor when glimpsing
178 gl_work->gl_desc = NULL;
179 /* This tells ldlm_work_gl_ast_lock this was allocated from a slab and
180 * must be freed in a slab-aware manner. */
181 gl_work->gl_flags = LDLM_GL_WORK_SLAB_ALLOCATED;
186 /* If the victim doesn't go on the glimpse list, we must release it */
187 LDLM_LOCK_RELEASE(victim_lock);
193 * OFD lock intent policy
195 * This defines ldlm_namespace::ns_policy interface for OFD.
196 * Intent policy is called when lock has an intent, for OFD that
197 * means glimpse lock and policy fills Lock Value Block (LVB).
199 * If already granted lock is found it will be placed in \a lockp and
200 * returned back to caller function.
202 * \param[in] ns namespace
203 * \param[in,out] lockp pointer to the lock
204 * \param[in] req_cookie incoming request
205 * \param[in] mode LDLM mode
206 * \param[in] flags LDLM flags
207 * \param[in] data opaque data, not used in OFD policy
209 * \retval ELDLM_LOCK_REPLACED if already granted lock was found
210 * and placed in \a lockp
211 * \retval ELDLM_LOCK_ABORTED in other cases except error
212 * \retval negative errno on error
214 int ofd_intent_policy(const struct lu_env *env, struct ldlm_namespace *ns,
215 struct ldlm_lock **lockp, void *req_cookie,
216 enum ldlm_mode mode, __u64 flags, void *data)
218 struct ptlrpc_request *req = req_cookie;
219 struct ldlm_lock *lock = *lockp;
220 struct ldlm_resource *res = lock->l_resource;
221 ldlm_processing_policy policy;
222 struct ost_lvb *res_lvb, *reply_lvb;
223 struct ldlm_reply *rep;
226 struct ldlm_interval_tree *tree;
227 struct ofd_intent_args arg;
229 [MSG_PTLRPC_BODY_OFF] = sizeof(struct ptlrpc_body),
230 [DLM_LOCKREPLY_OFF] = sizeof(*rep),
231 [DLM_REPLY_REC_OFF] = sizeof(*reply_lvb)
233 struct ldlm_glimpse_work *pos, *tmp;
236 /* update stats for intent in intent policy */
237 if (ptlrpc_req2svc(req)->srv_stats != NULL)
238 lprocfs_counter_incr(ptlrpc_req2svc(req)->srv_stats,
239 PTLRPC_LAST_CNTR + LDLM_GLIMPSE_ENQUEUE);
241 INIT_LIST_HEAD(&arg.gl_list);
242 arg.no_glimpse_ast = false;
244 lock->l_lvb_type = LVB_T_OST;
245 policy = ldlm_get_processing_policy(res);
246 LASSERT(policy != NULL);
247 LASSERT(req != NULL);
249 rc = lustre_pack_reply(req, 3, repsize, NULL);
251 RETURN(req->rq_status = rc);
253 rep = lustre_msg_buf(req->rq_repmsg, DLM_LOCKREPLY_OFF, sizeof(*rep));
254 LASSERT(rep != NULL);
256 reply_lvb = lustre_msg_buf(req->rq_repmsg, DLM_REPLY_REC_OFF,
258 LASSERT(reply_lvb != NULL);
260 /* Call the extent policy function to see if our request can be
261 * granted, or is blocked.
262 * If the OST lock has LDLM_FL_HAS_INTENT set, it means a glimpse
263 * lock, and should not be granted if the lock will be blocked.
266 if (flags & LDLM_FL_BLOCK_NOWAIT) {
267 OBD_FAIL_TIMEOUT(OBD_FAIL_LDLM_AGL_DELAY, 5);
269 if (OBD_FAIL_CHECK(OBD_FAIL_LDLM_AGL_NOLOCK))
270 RETURN(ELDLM_LOCK_ABORTED);
273 LASSERT(ns == ldlm_res_to_ns(res));
276 /* Check if this is a resend case (MSG_RESENT is set on RPC) and a
277 * lock was found by ldlm_handle_enqueue(); if so no need to grant
279 if (flags & LDLM_FL_RESENT) {
280 rc = LDLM_ITER_CONTINUE;
283 rc = policy(lock, &tmpflags, LDLM_PROCESS_RESCAN, &err, NULL);
284 check_res_locked(res);
287 /* The lock met with no resistance; we're finished. */
288 if (rc == LDLM_ITER_CONTINUE) {
289 if (OBD_FAIL_TIMEOUT(OBD_FAIL_LDLM_GLIMPSE, 2)) {
290 ldlm_resource_unlink_lock(lock);
291 err = ELDLM_LOCK_ABORTED;
293 err = ELDLM_LOCK_REPLACED;
297 } else if (flags & LDLM_FL_BLOCK_NOWAIT) {
298 /* LDLM_FL_BLOCK_NOWAIT means it is for AGL. Do not send glimpse
299 * callback for glimpse size. The real size user will trigger
300 * the glimpse callback when necessary. */
302 RETURN(ELDLM_LOCK_ABORTED);
305 /* Do not grant any lock, but instead send GL callbacks. The extent
306 * policy nicely created a list of all PW locks for us. We will choose
307 * the highest of those which are larger than the size in the LVB, if
308 * any, and perform a glimpse callback. */
309 res_lvb = res->lr_lvb_data;
310 LASSERT(res_lvb != NULL);
311 *reply_lvb = *res_lvb;
314 * ->ns_lock guarantees that no new locks are granted, and,
315 * therefore, that res->lr_lvb_data cannot increase beyond the
316 * end of already granted lock. As a result, it is safe to
317 * check against "stale" reply_lvb->lvb_size value without
320 arg.size = reply_lvb->lvb_size;
322 /* Check for PW locks beyond the size in the LVB, build the list
323 * of locks to glimpse (arg.gl_list) */
324 for (idx = 0; idx < LCK_MODE_NUM; idx++) {
325 tree = &res->lr_itree[idx];
326 if (tree->lit_mode == LCK_PR)
329 interval_iterate_reverse(tree->lit_root, ofd_intent_cb, &arg);
332 GOTO(out, rc = arg.error);
337 /* There were no PW locks beyond the size in the LVB; finished. */
338 if (list_empty(&arg.gl_list))
339 RETURN(ELDLM_LOCK_ABORTED);
341 if (arg.no_glimpse_ast) {
342 /* We are racing with unlink(); just return -ENOENT */
343 rep->lock_policy_res1 = ptlrpc_status_hton(-ENOENT);
344 GOTO(out, ELDLM_LOCK_ABORTED);
347 /* this will update the LVB */
348 ldlm_glimpse_locks(res, &arg.gl_list);
351 *reply_lvb = *res_lvb;
355 /* If the list is not empty, we failed to glimpse some locks and
356 * must clean up. Usually due to a race with unlink.*/
357 list_for_each_entry_safe(pos, tmp, &arg.gl_list, gl_list) {
358 list_del(&pos->gl_list);
359 LDLM_LOCK_RELEASE(pos->gl_lock);
360 OBD_SLAB_FREE_PTR(pos, ldlm_glimpse_work_kmem);
363 RETURN(rc < 0 ? rc : ELDLM_LOCK_ABORTED);