xref: /openbmc/linux/fs/ocfs2/dcache.c (revision e23feb16)
1 /* -*- mode: c; c-basic-offset: 8; -*-
2  * vim: noexpandtab sw=8 ts=8 sts=0:
3  *
4  * dcache.c
5  *
6  * dentry cache handling code
7  *
8  * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
9  *
10  * This program is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU General Public
12  * License as published by the Free Software Foundation; either
13  * version 2 of the License, or (at your option) any later version.
14  *
15  * This program is distributed in the hope that it will be useful,
16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
18  * General Public License for more details.
19  *
20  * You should have received a copy of the GNU General Public
21  * License along with this program; if not, write to the
22  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
23  * Boston, MA 021110-1307, USA.
24  */
25 
26 #include <linux/fs.h>
27 #include <linux/types.h>
28 #include <linux/slab.h>
29 #include <linux/namei.h>
30 
31 #include <cluster/masklog.h>
32 
33 #include "ocfs2.h"
34 
35 #include "alloc.h"
36 #include "dcache.h"
37 #include "dlmglue.h"
38 #include "file.h"
39 #include "inode.h"
40 #include "super.h"
41 #include "ocfs2_trace.h"
42 
43 void ocfs2_dentry_attach_gen(struct dentry *dentry)
44 {
45 	unsigned long gen =
46 		OCFS2_I(dentry->d_parent->d_inode)->ip_dir_lock_gen;
47 	BUG_ON(dentry->d_inode);
48 	dentry->d_fsdata = (void *)gen;
49 }
50 
51 
52 static int ocfs2_dentry_revalidate(struct dentry *dentry, unsigned int flags)
53 {
54 	struct inode *inode;
55 	int ret = 0;    /* if all else fails, just return false */
56 	struct ocfs2_super *osb;
57 
58 	if (flags & LOOKUP_RCU)
59 		return -ECHILD;
60 
61 	inode = dentry->d_inode;
62 	osb = OCFS2_SB(dentry->d_sb);
63 
64 	trace_ocfs2_dentry_revalidate(dentry, dentry->d_name.len,
65 				      dentry->d_name.name);
66 
67 	/* For a negative dentry -
68 	 * check the generation number of the parent and compare with the
69 	 * one stored in the inode.
70 	 */
71 	if (inode == NULL) {
72 		unsigned long gen = (unsigned long) dentry->d_fsdata;
73 		unsigned long pgen;
74 		spin_lock(&dentry->d_lock);
75 		pgen = OCFS2_I(dentry->d_parent->d_inode)->ip_dir_lock_gen;
76 		spin_unlock(&dentry->d_lock);
77 		trace_ocfs2_dentry_revalidate_negative(dentry->d_name.len,
78 						       dentry->d_name.name,
79 						       pgen, gen);
80 		if (gen != pgen)
81 			goto bail;
82 		goto valid;
83 	}
84 
85 	BUG_ON(!osb);
86 
87 	if (inode == osb->root_inode || is_bad_inode(inode))
88 		goto bail;
89 
90 	spin_lock(&OCFS2_I(inode)->ip_lock);
91 	/* did we or someone else delete this inode? */
92 	if (OCFS2_I(inode)->ip_flags & OCFS2_INODE_DELETED) {
93 		spin_unlock(&OCFS2_I(inode)->ip_lock);
94 		trace_ocfs2_dentry_revalidate_delete(
95 				(unsigned long long)OCFS2_I(inode)->ip_blkno);
96 		goto bail;
97 	}
98 	spin_unlock(&OCFS2_I(inode)->ip_lock);
99 
100 	/*
101 	 * We don't need a cluster lock to test this because once an
102 	 * inode nlink hits zero, it never goes back.
103 	 */
104 	if (inode->i_nlink == 0) {
105 		trace_ocfs2_dentry_revalidate_orphaned(
106 			(unsigned long long)OCFS2_I(inode)->ip_blkno,
107 			S_ISDIR(inode->i_mode));
108 		goto bail;
109 	}
110 
111 	/*
112 	 * If the last lookup failed to create dentry lock, let us
113 	 * redo it.
114 	 */
115 	if (!dentry->d_fsdata) {
116 		trace_ocfs2_dentry_revalidate_nofsdata(
117 				(unsigned long long)OCFS2_I(inode)->ip_blkno);
118 		goto bail;
119 	}
120 
121 valid:
122 	ret = 1;
123 
124 bail:
125 	trace_ocfs2_dentry_revalidate_ret(ret);
126 	return ret;
127 }
128 
129 static int ocfs2_match_dentry(struct dentry *dentry,
130 			      u64 parent_blkno,
131 			      int skip_unhashed)
132 {
133 	struct inode *parent;
134 
135 	/*
136 	 * ocfs2_lookup() does a d_splice_alias() _before_ attaching
137 	 * to the lock data, so we skip those here, otherwise
138 	 * ocfs2_dentry_attach_lock() will get its original dentry
139 	 * back.
140 	 */
141 	if (!dentry->d_fsdata)
142 		return 0;
143 
144 	if (!dentry->d_parent)
145 		return 0;
146 
147 	if (skip_unhashed && d_unhashed(dentry))
148 		return 0;
149 
150 	parent = dentry->d_parent->d_inode;
151 	/* Negative parent dentry? */
152 	if (!parent)
153 		return 0;
154 
155 	/* Name is in a different directory. */
156 	if (OCFS2_I(parent)->ip_blkno != parent_blkno)
157 		return 0;
158 
159 	return 1;
160 }
161 
162 /*
163  * Walk the inode alias list, and find a dentry which has a given
164  * parent. ocfs2_dentry_attach_lock() wants to find _any_ alias as it
165  * is looking for a dentry_lock reference. The downconvert thread is
166  * looking to unhash aliases, so we allow it to skip any that already
167  * have that property.
168  */
169 struct dentry *ocfs2_find_local_alias(struct inode *inode,
170 				      u64 parent_blkno,
171 				      int skip_unhashed)
172 {
173 	struct dentry *dentry;
174 
175 	spin_lock(&inode->i_lock);
176 	hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
177 		spin_lock(&dentry->d_lock);
178 		if (ocfs2_match_dentry(dentry, parent_blkno, skip_unhashed)) {
179 			trace_ocfs2_find_local_alias(dentry->d_name.len,
180 						     dentry->d_name.name);
181 
182 			dget_dlock(dentry);
183 			spin_unlock(&dentry->d_lock);
184 			spin_unlock(&inode->i_lock);
185 			return dentry;
186 		}
187 		spin_unlock(&dentry->d_lock);
188 	}
189 	spin_unlock(&inode->i_lock);
190 	return NULL;
191 }
192 
193 DEFINE_SPINLOCK(dentry_attach_lock);
194 
195 /*
196  * Attach this dentry to a cluster lock.
197  *
198  * Dentry locks cover all links in a given directory to a particular
199  * inode. We do this so that ocfs2 can build a lock name which all
200  * nodes in the cluster can agree on at all times. Shoving full names
201  * in the cluster lock won't work due to size restrictions. Covering
202  * links inside of a directory is a good compromise because it still
203  * allows us to use the parent directory lock to synchronize
204  * operations.
205  *
206  * Call this function with the parent dir semaphore and the parent dir
207  * cluster lock held.
208  *
209  * The dir semaphore will protect us from having to worry about
210  * concurrent processes on our node trying to attach a lock at the
211  * same time.
212  *
213  * The dir cluster lock (held at either PR or EX mode) protects us
214  * from unlink and rename on other nodes.
215  *
216  * A dput() can happen asynchronously due to pruning, so we cover
217  * attaching and detaching the dentry lock with a
218  * dentry_attach_lock.
219  *
220  * A node which has done lookup on a name retains a protected read
221  * lock until final dput. If the user requests and unlink or rename,
222  * the protected read is upgraded to an exclusive lock. Other nodes
223  * who have seen the dentry will then be informed that they need to
224  * downgrade their lock, which will involve d_delete on the
225  * dentry. This happens in ocfs2_dentry_convert_worker().
226  */
227 int ocfs2_dentry_attach_lock(struct dentry *dentry,
228 			     struct inode *inode,
229 			     u64 parent_blkno)
230 {
231 	int ret;
232 	struct dentry *alias;
233 	struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
234 
235 	trace_ocfs2_dentry_attach_lock(dentry->d_name.len, dentry->d_name.name,
236 				       (unsigned long long)parent_blkno, dl);
237 
238 	/*
239 	 * Negative dentry. We ignore these for now.
240 	 *
241 	 * XXX: Could we can improve ocfs2_dentry_revalidate() by
242 	 * tracking these?
243 	 */
244 	if (!inode)
245 		return 0;
246 
247 	if (!dentry->d_inode && dentry->d_fsdata) {
248 		/* Converting a negative dentry to positive
249 		   Clear dentry->d_fsdata */
250 		dentry->d_fsdata = dl = NULL;
251 	}
252 
253 	if (dl) {
254 		mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
255 				" \"%.*s\": old parent: %llu, new: %llu\n",
256 				dentry->d_name.len, dentry->d_name.name,
257 				(unsigned long long)parent_blkno,
258 				(unsigned long long)dl->dl_parent_blkno);
259 		return 0;
260 	}
261 
262 	alias = ocfs2_find_local_alias(inode, parent_blkno, 0);
263 	if (alias) {
264 		/*
265 		 * Great, an alias exists, which means we must have a
266 		 * dentry lock already. We can just grab the lock off
267 		 * the alias and add it to the list.
268 		 *
269 		 * We're depending here on the fact that this dentry
270 		 * was found and exists in the dcache and so must have
271 		 * a reference to the dentry_lock because we can't
272 		 * race creates. Final dput() cannot happen on it
273 		 * since we have it pinned, so our reference is safe.
274 		 */
275 		dl = alias->d_fsdata;
276 		mlog_bug_on_msg(!dl, "parent %llu, ino %llu\n",
277 				(unsigned long long)parent_blkno,
278 				(unsigned long long)OCFS2_I(inode)->ip_blkno);
279 
280 		mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
281 				" \"%.*s\": old parent: %llu, new: %llu\n",
282 				dentry->d_name.len, dentry->d_name.name,
283 				(unsigned long long)parent_blkno,
284 				(unsigned long long)dl->dl_parent_blkno);
285 
286 		trace_ocfs2_dentry_attach_lock_found(dl->dl_lockres.l_name,
287 				(unsigned long long)parent_blkno,
288 				(unsigned long long)OCFS2_I(inode)->ip_blkno);
289 
290 		goto out_attach;
291 	}
292 
293 	/*
294 	 * There are no other aliases
295 	 */
296 	dl = kmalloc(sizeof(*dl), GFP_NOFS);
297 	if (!dl) {
298 		ret = -ENOMEM;
299 		mlog_errno(ret);
300 		return ret;
301 	}
302 
303 	dl->dl_count = 0;
304 	/*
305 	 * Does this have to happen below, for all attaches, in case
306 	 * the struct inode gets blown away by the downconvert thread?
307 	 */
308 	dl->dl_inode = igrab(inode);
309 	dl->dl_parent_blkno = parent_blkno;
310 	ocfs2_dentry_lock_res_init(dl, parent_blkno, inode);
311 
312 out_attach:
313 	spin_lock(&dentry_attach_lock);
314 	dentry->d_fsdata = dl;
315 	dl->dl_count++;
316 	spin_unlock(&dentry_attach_lock);
317 
318 	/*
319 	 * This actually gets us our PRMODE level lock. From now on,
320 	 * we'll have a notification if one of these names is
321 	 * destroyed on another node.
322 	 */
323 	ret = ocfs2_dentry_lock(dentry, 0);
324 	if (!ret)
325 		ocfs2_dentry_unlock(dentry, 0);
326 	else
327 		mlog_errno(ret);
328 
329 	/*
330 	 * In case of error, manually free the allocation and do the iput().
331 	 * We need to do this because error here means no d_instantiate(),
332 	 * which means iput() will not be called during dput(dentry).
333 	 */
334 	if (ret < 0 && !alias) {
335 		ocfs2_lock_res_free(&dl->dl_lockres);
336 		BUG_ON(dl->dl_count != 1);
337 		spin_lock(&dentry_attach_lock);
338 		dentry->d_fsdata = NULL;
339 		spin_unlock(&dentry_attach_lock);
340 		kfree(dl);
341 		iput(inode);
342 	}
343 
344 	dput(alias);
345 
346 	return ret;
347 }
348 
349 DEFINE_SPINLOCK(dentry_list_lock);
350 
351 /* We limit the number of dentry locks to drop in one go. We have
352  * this limit so that we don't starve other users of ocfs2_wq. */
353 #define DL_INODE_DROP_COUNT 64
354 
355 /* Drop inode references from dentry locks */
356 static void __ocfs2_drop_dl_inodes(struct ocfs2_super *osb, int drop_count)
357 {
358 	struct ocfs2_dentry_lock *dl;
359 
360 	spin_lock(&dentry_list_lock);
361 	while (osb->dentry_lock_list && (drop_count < 0 || drop_count--)) {
362 		dl = osb->dentry_lock_list;
363 		osb->dentry_lock_list = dl->dl_next;
364 		spin_unlock(&dentry_list_lock);
365 		iput(dl->dl_inode);
366 		kfree(dl);
367 		spin_lock(&dentry_list_lock);
368 	}
369 	spin_unlock(&dentry_list_lock);
370 }
371 
372 void ocfs2_drop_dl_inodes(struct work_struct *work)
373 {
374 	struct ocfs2_super *osb = container_of(work, struct ocfs2_super,
375 					       dentry_lock_work);
376 
377 	__ocfs2_drop_dl_inodes(osb, DL_INODE_DROP_COUNT);
378 	/*
379 	 * Don't queue dropping if umount is in progress. We flush the
380 	 * list in ocfs2_dismount_volume
381 	 */
382 	spin_lock(&dentry_list_lock);
383 	if (osb->dentry_lock_list &&
384 	    !ocfs2_test_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED))
385 		queue_work(ocfs2_wq, &osb->dentry_lock_work);
386 	spin_unlock(&dentry_list_lock);
387 }
388 
389 /* Flush the whole work queue */
390 void ocfs2_drop_all_dl_inodes(struct ocfs2_super *osb)
391 {
392 	__ocfs2_drop_dl_inodes(osb, -1);
393 }
394 
395 /*
396  * ocfs2_dentry_iput() and friends.
397  *
398  * At this point, our particular dentry is detached from the inodes
399  * alias list, so there's no way that the locking code can find it.
400  *
401  * The interesting stuff happens when we determine that our lock needs
402  * to go away because this is the last subdir alias in the
403  * system. This function needs to handle a couple things:
404  *
405  * 1) Synchronizing lock shutdown with the downconvert threads. This
406  *    is already handled for us via the lockres release drop function
407  *    called in ocfs2_release_dentry_lock()
408  *
409  * 2) A race may occur when we're doing our lock shutdown and
410  *    another process wants to create a new dentry lock. Right now we
411  *    let them race, which means that for a very short while, this
412  *    node might have two locks on a lock resource. This should be a
413  *    problem though because one of them is in the process of being
414  *    thrown out.
415  */
416 static void ocfs2_drop_dentry_lock(struct ocfs2_super *osb,
417 				   struct ocfs2_dentry_lock *dl)
418 {
419 	ocfs2_simple_drop_lockres(osb, &dl->dl_lockres);
420 	ocfs2_lock_res_free(&dl->dl_lockres);
421 
422 	/* We leave dropping of inode reference to ocfs2_wq as that can
423 	 * possibly lead to inode deletion which gets tricky */
424 	spin_lock(&dentry_list_lock);
425 	if (!osb->dentry_lock_list &&
426 	    !ocfs2_test_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED))
427 		queue_work(ocfs2_wq, &osb->dentry_lock_work);
428 	dl->dl_next = osb->dentry_lock_list;
429 	osb->dentry_lock_list = dl;
430 	spin_unlock(&dentry_list_lock);
431 }
432 
433 void ocfs2_dentry_lock_put(struct ocfs2_super *osb,
434 			   struct ocfs2_dentry_lock *dl)
435 {
436 	int unlock;
437 
438 	BUG_ON(dl->dl_count == 0);
439 
440 	spin_lock(&dentry_attach_lock);
441 	dl->dl_count--;
442 	unlock = !dl->dl_count;
443 	spin_unlock(&dentry_attach_lock);
444 
445 	if (unlock)
446 		ocfs2_drop_dentry_lock(osb, dl);
447 }
448 
449 static void ocfs2_dentry_iput(struct dentry *dentry, struct inode *inode)
450 {
451 	struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
452 
453 	if (!dl) {
454 		/*
455 		 * No dentry lock is ok if we're disconnected or
456 		 * unhashed.
457 		 */
458 		if (!(dentry->d_flags & DCACHE_DISCONNECTED) &&
459 		    !d_unhashed(dentry)) {
460 			unsigned long long ino = 0ULL;
461 			if (inode)
462 				ino = (unsigned long long)OCFS2_I(inode)->ip_blkno;
463 			mlog(ML_ERROR, "Dentry is missing cluster lock. "
464 			     "inode: %llu, d_flags: 0x%x, d_name: %.*s\n",
465 			     ino, dentry->d_flags, dentry->d_name.len,
466 			     dentry->d_name.name);
467 		}
468 
469 		goto out;
470 	}
471 
472 	mlog_bug_on_msg(dl->dl_count == 0, "dentry: %.*s, count: %u\n",
473 			dentry->d_name.len, dentry->d_name.name,
474 			dl->dl_count);
475 
476 	ocfs2_dentry_lock_put(OCFS2_SB(dentry->d_sb), dl);
477 
478 out:
479 	iput(inode);
480 }
481 
482 /*
483  * d_move(), but keep the locks in sync.
484  *
485  * When we are done, "dentry" will have the parent dir and name of
486  * "target", which will be thrown away.
487  *
488  * We manually update the lock of "dentry" if need be.
489  *
490  * "target" doesn't have it's dentry lock touched - we allow the later
491  * dput() to handle this for us.
492  *
493  * This is called during ocfs2_rename(), while holding parent
494  * directory locks. The dentries have already been deleted on other
495  * nodes via ocfs2_remote_dentry_delete().
496  *
497  * Normally, the VFS handles the d_move() for the file system, after
498  * the ->rename() callback. OCFS2 wants to handle this internally, so
499  * the new lock can be created atomically with respect to the cluster.
500  */
501 void ocfs2_dentry_move(struct dentry *dentry, struct dentry *target,
502 		       struct inode *old_dir, struct inode *new_dir)
503 {
504 	int ret;
505 	struct ocfs2_super *osb = OCFS2_SB(old_dir->i_sb);
506 	struct inode *inode = dentry->d_inode;
507 
508 	/*
509 	 * Move within the same directory, so the actual lock info won't
510 	 * change.
511 	 *
512 	 * XXX: Is there any advantage to dropping the lock here?
513 	 */
514 	if (old_dir == new_dir)
515 		goto out_move;
516 
517 	ocfs2_dentry_lock_put(osb, dentry->d_fsdata);
518 
519 	dentry->d_fsdata = NULL;
520 	ret = ocfs2_dentry_attach_lock(dentry, inode, OCFS2_I(new_dir)->ip_blkno);
521 	if (ret)
522 		mlog_errno(ret);
523 
524 out_move:
525 	d_move(dentry, target);
526 }
527 
528 const struct dentry_operations ocfs2_dentry_ops = {
529 	.d_revalidate		= ocfs2_dentry_revalidate,
530 	.d_iput			= ocfs2_dentry_iput,
531 };
532