xref: /linux/fs/ocfs2/dcache.c (revision bd628c1bed7902ec1f24ba0fe70758949146abbe)
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 "ocfs2_trace.h"
41 
42 void ocfs2_dentry_attach_gen(struct dentry *dentry)
43 {
44 	unsigned long gen =
45 		OCFS2_I(d_inode(dentry->d_parent))->ip_dir_lock_gen;
46 	BUG_ON(d_inode(dentry));
47 	dentry->d_fsdata = (void *)gen;
48 }
49 
50 
51 static int ocfs2_dentry_revalidate(struct dentry *dentry, unsigned int flags)
52 {
53 	struct inode *inode;
54 	int ret = 0;    /* if all else fails, just return false */
55 	struct ocfs2_super *osb;
56 
57 	if (flags & LOOKUP_RCU)
58 		return -ECHILD;
59 
60 	inode = d_inode(dentry);
61 	osb = OCFS2_SB(dentry->d_sb);
62 
63 	trace_ocfs2_dentry_revalidate(dentry, dentry->d_name.len,
64 				      dentry->d_name.name);
65 
66 	/* For a negative dentry -
67 	 * check the generation number of the parent and compare with the
68 	 * one stored in the inode.
69 	 */
70 	if (inode == NULL) {
71 		unsigned long gen = (unsigned long) dentry->d_fsdata;
72 		unsigned long pgen;
73 		spin_lock(&dentry->d_lock);
74 		pgen = OCFS2_I(d_inode(dentry->d_parent))->ip_dir_lock_gen;
75 		spin_unlock(&dentry->d_lock);
76 		trace_ocfs2_dentry_revalidate_negative(dentry->d_name.len,
77 						       dentry->d_name.name,
78 						       pgen, gen);
79 		if (gen != pgen)
80 			goto bail;
81 		goto valid;
82 	}
83 
84 	BUG_ON(!osb);
85 
86 	if (inode == osb->root_inode || is_bad_inode(inode))
87 		goto bail;
88 
89 	spin_lock(&OCFS2_I(inode)->ip_lock);
90 	/* did we or someone else delete this inode? */
91 	if (OCFS2_I(inode)->ip_flags & OCFS2_INODE_DELETED) {
92 		spin_unlock(&OCFS2_I(inode)->ip_lock);
93 		trace_ocfs2_dentry_revalidate_delete(
94 				(unsigned long long)OCFS2_I(inode)->ip_blkno);
95 		goto bail;
96 	}
97 	spin_unlock(&OCFS2_I(inode)->ip_lock);
98 
99 	/*
100 	 * We don't need a cluster lock to test this because once an
101 	 * inode nlink hits zero, it never goes back.
102 	 */
103 	if (inode->i_nlink == 0) {
104 		trace_ocfs2_dentry_revalidate_orphaned(
105 			(unsigned long long)OCFS2_I(inode)->ip_blkno,
106 			S_ISDIR(inode->i_mode));
107 		goto bail;
108 	}
109 
110 	/*
111 	 * If the last lookup failed to create dentry lock, let us
112 	 * redo it.
113 	 */
114 	if (!dentry->d_fsdata) {
115 		trace_ocfs2_dentry_revalidate_nofsdata(
116 				(unsigned long long)OCFS2_I(inode)->ip_blkno);
117 		goto bail;
118 	}
119 
120 valid:
121 	ret = 1;
122 
123 bail:
124 	trace_ocfs2_dentry_revalidate_ret(ret);
125 	return ret;
126 }
127 
128 static int ocfs2_match_dentry(struct dentry *dentry,
129 			      u64 parent_blkno,
130 			      int skip_unhashed)
131 {
132 	struct inode *parent;
133 
134 	/*
135 	 * ocfs2_lookup() does a d_splice_alias() _before_ attaching
136 	 * to the lock data, so we skip those here, otherwise
137 	 * ocfs2_dentry_attach_lock() will get its original dentry
138 	 * back.
139 	 */
140 	if (!dentry->d_fsdata)
141 		return 0;
142 
143 	if (!dentry->d_parent)
144 		return 0;
145 
146 	if (skip_unhashed && d_unhashed(dentry))
147 		return 0;
148 
149 	parent = d_inode(dentry->d_parent);
150 	/* Negative parent dentry? */
151 	if (!parent)
152 		return 0;
153 
154 	/* Name is in a different directory. */
155 	if (OCFS2_I(parent)->ip_blkno != parent_blkno)
156 		return 0;
157 
158 	return 1;
159 }
160 
161 /*
162  * Walk the inode alias list, and find a dentry which has a given
163  * parent. ocfs2_dentry_attach_lock() wants to find _any_ alias as it
164  * is looking for a dentry_lock reference. The downconvert thread is
165  * looking to unhash aliases, so we allow it to skip any that already
166  * have that property.
167  */
168 struct dentry *ocfs2_find_local_alias(struct inode *inode,
169 				      u64 parent_blkno,
170 				      int skip_unhashed)
171 {
172 	struct dentry *dentry;
173 
174 	spin_lock(&inode->i_lock);
175 	hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
176 		spin_lock(&dentry->d_lock);
177 		if (ocfs2_match_dentry(dentry, parent_blkno, skip_unhashed)) {
178 			trace_ocfs2_find_local_alias(dentry->d_name.len,
179 						     dentry->d_name.name);
180 
181 			dget_dlock(dentry);
182 			spin_unlock(&dentry->d_lock);
183 			spin_unlock(&inode->i_lock);
184 			return dentry;
185 		}
186 		spin_unlock(&dentry->d_lock);
187 	}
188 	spin_unlock(&inode->i_lock);
189 	return NULL;
190 }
191 
192 DEFINE_SPINLOCK(dentry_attach_lock);
193 
194 /*
195  * Attach this dentry to a cluster lock.
196  *
197  * Dentry locks cover all links in a given directory to a particular
198  * inode. We do this so that ocfs2 can build a lock name which all
199  * nodes in the cluster can agree on at all times. Shoving full names
200  * in the cluster lock won't work due to size restrictions. Covering
201  * links inside of a directory is a good compromise because it still
202  * allows us to use the parent directory lock to synchronize
203  * operations.
204  *
205  * Call this function with the parent dir semaphore and the parent dir
206  * cluster lock held.
207  *
208  * The dir semaphore will protect us from having to worry about
209  * concurrent processes on our node trying to attach a lock at the
210  * same time.
211  *
212  * The dir cluster lock (held at either PR or EX mode) protects us
213  * from unlink and rename on other nodes.
214  *
215  * A dput() can happen asynchronously due to pruning, so we cover
216  * attaching and detaching the dentry lock with a
217  * dentry_attach_lock.
218  *
219  * A node which has done lookup on a name retains a protected read
220  * lock until final dput. If the user requests and unlink or rename,
221  * the protected read is upgraded to an exclusive lock. Other nodes
222  * who have seen the dentry will then be informed that they need to
223  * downgrade their lock, which will involve d_delete on the
224  * dentry. This happens in ocfs2_dentry_convert_worker().
225  */
226 int ocfs2_dentry_attach_lock(struct dentry *dentry,
227 			     struct inode *inode,
228 			     u64 parent_blkno)
229 {
230 	int ret;
231 	struct dentry *alias;
232 	struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
233 
234 	trace_ocfs2_dentry_attach_lock(dentry->d_name.len, dentry->d_name.name,
235 				       (unsigned long long)parent_blkno, dl);
236 
237 	/*
238 	 * Negative dentry. We ignore these for now.
239 	 *
240 	 * XXX: Could we can improve ocfs2_dentry_revalidate() by
241 	 * tracking these?
242 	 */
243 	if (!inode)
244 		return 0;
245 
246 	if (d_really_is_negative(dentry) && dentry->d_fsdata) {
247 		/* Converting a negative dentry to positive
248 		   Clear dentry->d_fsdata */
249 		dentry->d_fsdata = dl = NULL;
250 	}
251 
252 	if (dl) {
253 		mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
254 				" \"%pd\": old parent: %llu, new: %llu\n",
255 				dentry,
256 				(unsigned long long)parent_blkno,
257 				(unsigned long long)dl->dl_parent_blkno);
258 		return 0;
259 	}
260 
261 	alias = ocfs2_find_local_alias(inode, parent_blkno, 0);
262 	if (alias) {
263 		/*
264 		 * Great, an alias exists, which means we must have a
265 		 * dentry lock already. We can just grab the lock off
266 		 * the alias and add it to the list.
267 		 *
268 		 * We're depending here on the fact that this dentry
269 		 * was found and exists in the dcache and so must have
270 		 * a reference to the dentry_lock because we can't
271 		 * race creates. Final dput() cannot happen on it
272 		 * since we have it pinned, so our reference is safe.
273 		 */
274 		dl = alias->d_fsdata;
275 		mlog_bug_on_msg(!dl, "parent %llu, ino %llu\n",
276 				(unsigned long long)parent_blkno,
277 				(unsigned long long)OCFS2_I(inode)->ip_blkno);
278 
279 		mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
280 				" \"%pd\": old parent: %llu, new: %llu\n",
281 				dentry,
282 				(unsigned long long)parent_blkno,
283 				(unsigned long long)dl->dl_parent_blkno);
284 
285 		trace_ocfs2_dentry_attach_lock_found(dl->dl_lockres.l_name,
286 				(unsigned long long)parent_blkno,
287 				(unsigned long long)OCFS2_I(inode)->ip_blkno);
288 
289 		goto out_attach;
290 	}
291 
292 	/*
293 	 * There are no other aliases
294 	 */
295 	dl = kmalloc(sizeof(*dl), GFP_NOFS);
296 	if (!dl) {
297 		ret = -ENOMEM;
298 		mlog_errno(ret);
299 		return ret;
300 	}
301 
302 	dl->dl_count = 0;
303 	/*
304 	 * Does this have to happen below, for all attaches, in case
305 	 * the struct inode gets blown away by the downconvert thread?
306 	 */
307 	dl->dl_inode = igrab(inode);
308 	dl->dl_parent_blkno = parent_blkno;
309 	ocfs2_dentry_lock_res_init(dl, parent_blkno, inode);
310 
311 out_attach:
312 	spin_lock(&dentry_attach_lock);
313 	dentry->d_fsdata = dl;
314 	dl->dl_count++;
315 	spin_unlock(&dentry_attach_lock);
316 
317 	/*
318 	 * This actually gets us our PRMODE level lock. From now on,
319 	 * we'll have a notification if one of these names is
320 	 * destroyed on another node.
321 	 */
322 	ret = ocfs2_dentry_lock(dentry, 0);
323 	if (!ret)
324 		ocfs2_dentry_unlock(dentry, 0);
325 	else
326 		mlog_errno(ret);
327 
328 	/*
329 	 * In case of error, manually free the allocation and do the iput().
330 	 * We need to do this because error here means no d_instantiate(),
331 	 * which means iput() will not be called during dput(dentry).
332 	 */
333 	if (ret < 0 && !alias) {
334 		ocfs2_lock_res_free(&dl->dl_lockres);
335 		BUG_ON(dl->dl_count != 1);
336 		spin_lock(&dentry_attach_lock);
337 		dentry->d_fsdata = NULL;
338 		spin_unlock(&dentry_attach_lock);
339 		kfree(dl);
340 		iput(inode);
341 	}
342 
343 	dput(alias);
344 
345 	return ret;
346 }
347 
348 /*
349  * ocfs2_dentry_iput() and friends.
350  *
351  * At this point, our particular dentry is detached from the inodes
352  * alias list, so there's no way that the locking code can find it.
353  *
354  * The interesting stuff happens when we determine that our lock needs
355  * to go away because this is the last subdir alias in the
356  * system. This function needs to handle a couple things:
357  *
358  * 1) Synchronizing lock shutdown with the downconvert threads. This
359  *    is already handled for us via the lockres release drop function
360  *    called in ocfs2_release_dentry_lock()
361  *
362  * 2) A race may occur when we're doing our lock shutdown and
363  *    another process wants to create a new dentry lock. Right now we
364  *    let them race, which means that for a very short while, this
365  *    node might have two locks on a lock resource. This should be a
366  *    problem though because one of them is in the process of being
367  *    thrown out.
368  */
369 static void ocfs2_drop_dentry_lock(struct ocfs2_super *osb,
370 				   struct ocfs2_dentry_lock *dl)
371 {
372 	iput(dl->dl_inode);
373 	ocfs2_simple_drop_lockres(osb, &dl->dl_lockres);
374 	ocfs2_lock_res_free(&dl->dl_lockres);
375 	kfree(dl);
376 }
377 
378 void ocfs2_dentry_lock_put(struct ocfs2_super *osb,
379 			   struct ocfs2_dentry_lock *dl)
380 {
381 	int unlock = 0;
382 
383 	BUG_ON(dl->dl_count == 0);
384 
385 	spin_lock(&dentry_attach_lock);
386 	dl->dl_count--;
387 	unlock = !dl->dl_count;
388 	spin_unlock(&dentry_attach_lock);
389 
390 	if (unlock)
391 		ocfs2_drop_dentry_lock(osb, dl);
392 }
393 
394 static void ocfs2_dentry_iput(struct dentry *dentry, struct inode *inode)
395 {
396 	struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
397 
398 	if (!dl) {
399 		/*
400 		 * No dentry lock is ok if we're disconnected or
401 		 * unhashed.
402 		 */
403 		if (!(dentry->d_flags & DCACHE_DISCONNECTED) &&
404 		    !d_unhashed(dentry)) {
405 			unsigned long long ino = 0ULL;
406 			if (inode)
407 				ino = (unsigned long long)OCFS2_I(inode)->ip_blkno;
408 			mlog(ML_ERROR, "Dentry is missing cluster lock. "
409 			     "inode: %llu, d_flags: 0x%x, d_name: %pd\n",
410 			     ino, dentry->d_flags, dentry);
411 		}
412 
413 		goto out;
414 	}
415 
416 	mlog_bug_on_msg(dl->dl_count == 0, "dentry: %pd, count: %u\n",
417 			dentry, dl->dl_count);
418 
419 	ocfs2_dentry_lock_put(OCFS2_SB(dentry->d_sb), dl);
420 
421 out:
422 	iput(inode);
423 }
424 
425 /*
426  * d_move(), but keep the locks in sync.
427  *
428  * When we are done, "dentry" will have the parent dir and name of
429  * "target", which will be thrown away.
430  *
431  * We manually update the lock of "dentry" if need be.
432  *
433  * "target" doesn't have it's dentry lock touched - we allow the later
434  * dput() to handle this for us.
435  *
436  * This is called during ocfs2_rename(), while holding parent
437  * directory locks. The dentries have already been deleted on other
438  * nodes via ocfs2_remote_dentry_delete().
439  *
440  * Normally, the VFS handles the d_move() for the file system, after
441  * the ->rename() callback. OCFS2 wants to handle this internally, so
442  * the new lock can be created atomically with respect to the cluster.
443  */
444 void ocfs2_dentry_move(struct dentry *dentry, struct dentry *target,
445 		       struct inode *old_dir, struct inode *new_dir)
446 {
447 	int ret;
448 	struct ocfs2_super *osb = OCFS2_SB(old_dir->i_sb);
449 	struct inode *inode = d_inode(dentry);
450 
451 	/*
452 	 * Move within the same directory, so the actual lock info won't
453 	 * change.
454 	 *
455 	 * XXX: Is there any advantage to dropping the lock here?
456 	 */
457 	if (old_dir == new_dir)
458 		goto out_move;
459 
460 	ocfs2_dentry_lock_put(osb, dentry->d_fsdata);
461 
462 	dentry->d_fsdata = NULL;
463 	ret = ocfs2_dentry_attach_lock(dentry, inode, OCFS2_I(new_dir)->ip_blkno);
464 	if (ret)
465 		mlog_errno(ret);
466 
467 out_move:
468 	d_move(dentry, target);
469 }
470 
471 const struct dentry_operations ocfs2_dentry_ops = {
472 	.d_revalidate		= ocfs2_dentry_revalidate,
473 	.d_iput			= ocfs2_dentry_iput,
474 };
475