1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * dcache.c
4 *
5 * dentry cache handling code
6 *
7 * Copyright (C) 2002, 2004 Oracle. All rights reserved.
8 */
9
10#include <linux/fs.h>
11#include <linux/types.h>
12#include <linux/slab.h>
13#include <linux/namei.h>
14
15#include <cluster/masklog.h>
16
17#include "ocfs2.h"
18
19#include "alloc.h"
20#include "dcache.h"
21#include "dlmglue.h"
22#include "file.h"
23#include "inode.h"
24#include "ocfs2_trace.h"
25
26void ocfs2_dentry_attach_gen(struct dentry *dentry)
27{
28 unsigned long gen =
29 OCFS2_I(inode: d_inode(dentry: dentry->d_parent))->ip_dir_lock_gen;
30 BUG_ON(d_inode(dentry));
31 dentry->d_fsdata = (void *)gen;
32}
33
34
35static int ocfs2_dentry_revalidate(struct dentry *dentry, unsigned int flags)
36{
37 struct inode *inode;
38 int ret = 0; /* if all else fails, just return false */
39 struct ocfs2_super *osb;
40
41 if (flags & LOOKUP_RCU)
42 return -ECHILD;
43
44 inode = d_inode(dentry);
45 osb = OCFS2_SB(dentry->d_sb);
46
47 trace_ocfs2_dentry_revalidate(dentry, len: dentry->d_name.len,
48 name: dentry->d_name.name);
49
50 /* For a negative dentry -
51 * check the generation number of the parent and compare with the
52 * one stored in the inode.
53 */
54 if (inode == NULL) {
55 unsigned long gen = (unsigned long) dentry->d_fsdata;
56 unsigned long pgen;
57 spin_lock(lock: &dentry->d_lock);
58 pgen = OCFS2_I(inode: d_inode(dentry: dentry->d_parent))->ip_dir_lock_gen;
59 spin_unlock(lock: &dentry->d_lock);
60 trace_ocfs2_dentry_revalidate_negative(len: dentry->d_name.len,
61 name: dentry->d_name.name,
62 pgen, gen);
63 if (gen != pgen)
64 goto bail;
65 goto valid;
66 }
67
68 BUG_ON(!osb);
69
70 if (inode == osb->root_inode || is_bad_inode(inode))
71 goto bail;
72
73 spin_lock(lock: &OCFS2_I(inode)->ip_lock);
74 /* did we or someone else delete this inode? */
75 if (OCFS2_I(inode)->ip_flags & OCFS2_INODE_DELETED) {
76 spin_unlock(lock: &OCFS2_I(inode)->ip_lock);
77 trace_ocfs2_dentry_revalidate_delete(
78 num: (unsigned long long)OCFS2_I(inode)->ip_blkno);
79 goto bail;
80 }
81 spin_unlock(lock: &OCFS2_I(inode)->ip_lock);
82
83 /*
84 * We don't need a cluster lock to test this because once an
85 * inode nlink hits zero, it never goes back.
86 */
87 if (inode->i_nlink == 0) {
88 trace_ocfs2_dentry_revalidate_orphaned(
89 val1: (unsigned long long)OCFS2_I(inode)->ip_blkno,
90 S_ISDIR(inode->i_mode));
91 goto bail;
92 }
93
94 /*
95 * If the last lookup failed to create dentry lock, let us
96 * redo it.
97 */
98 if (!dentry->d_fsdata) {
99 trace_ocfs2_dentry_revalidate_nofsdata(
100 num: (unsigned long long)OCFS2_I(inode)->ip_blkno);
101 goto bail;
102 }
103
104valid:
105 ret = 1;
106
107bail:
108 trace_ocfs2_dentry_revalidate_ret(num: ret);
109 return ret;
110}
111
112static int ocfs2_match_dentry(struct dentry *dentry,
113 u64 parent_blkno,
114 int skip_unhashed)
115{
116 struct inode *parent;
117
118 /*
119 * ocfs2_lookup() does a d_splice_alias() _before_ attaching
120 * to the lock data, so we skip those here, otherwise
121 * ocfs2_dentry_attach_lock() will get its original dentry
122 * back.
123 */
124 if (!dentry->d_fsdata)
125 return 0;
126
127 if (!dentry->d_parent)
128 return 0;
129
130 if (skip_unhashed && d_unhashed(dentry))
131 return 0;
132
133 parent = d_inode(dentry: dentry->d_parent);
134 /* Negative parent dentry? */
135 if (!parent)
136 return 0;
137
138 /* Name is in a different directory. */
139 if (OCFS2_I(inode: parent)->ip_blkno != parent_blkno)
140 return 0;
141
142 return 1;
143}
144
145/*
146 * Walk the inode alias list, and find a dentry which has a given
147 * parent. ocfs2_dentry_attach_lock() wants to find _any_ alias as it
148 * is looking for a dentry_lock reference. The downconvert thread is
149 * looking to unhash aliases, so we allow it to skip any that already
150 * have that property.
151 */
152struct dentry *ocfs2_find_local_alias(struct inode *inode,
153 u64 parent_blkno,
154 int skip_unhashed)
155{
156 struct dentry *dentry;
157
158 spin_lock(lock: &inode->i_lock);
159 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
160 spin_lock(lock: &dentry->d_lock);
161 if (ocfs2_match_dentry(dentry, parent_blkno, skip_unhashed)) {
162 trace_ocfs2_find_local_alias(len: dentry->d_name.len,
163 name: dentry->d_name.name);
164
165 dget_dlock(dentry);
166 spin_unlock(lock: &dentry->d_lock);
167 spin_unlock(lock: &inode->i_lock);
168 return dentry;
169 }
170 spin_unlock(lock: &dentry->d_lock);
171 }
172 spin_unlock(lock: &inode->i_lock);
173 return NULL;
174}
175
176DEFINE_SPINLOCK(dentry_attach_lock);
177
178/*
179 * Attach this dentry to a cluster lock.
180 *
181 * Dentry locks cover all links in a given directory to a particular
182 * inode. We do this so that ocfs2 can build a lock name which all
183 * nodes in the cluster can agree on at all times. Shoving full names
184 * in the cluster lock won't work due to size restrictions. Covering
185 * links inside of a directory is a good compromise because it still
186 * allows us to use the parent directory lock to synchronize
187 * operations.
188 *
189 * Call this function with the parent dir semaphore and the parent dir
190 * cluster lock held.
191 *
192 * The dir semaphore will protect us from having to worry about
193 * concurrent processes on our node trying to attach a lock at the
194 * same time.
195 *
196 * The dir cluster lock (held at either PR or EX mode) protects us
197 * from unlink and rename on other nodes.
198 *
199 * A dput() can happen asynchronously due to pruning, so we cover
200 * attaching and detaching the dentry lock with a
201 * dentry_attach_lock.
202 *
203 * A node which has done lookup on a name retains a protected read
204 * lock until final dput. If the user requests and unlink or rename,
205 * the protected read is upgraded to an exclusive lock. Other nodes
206 * who have seen the dentry will then be informed that they need to
207 * downgrade their lock, which will involve d_delete on the
208 * dentry. This happens in ocfs2_dentry_convert_worker().
209 */
210int ocfs2_dentry_attach_lock(struct dentry *dentry,
211 struct inode *inode,
212 u64 parent_blkno)
213{
214 int ret;
215 struct dentry *alias;
216 struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
217
218 trace_ocfs2_dentry_attach_lock(len: dentry->d_name.len, name: dentry->d_name.name,
219 parent: (unsigned long long)parent_blkno, fsdata: dl);
220
221 /*
222 * Negative dentry. We ignore these for now.
223 *
224 * XXX: Could we can improve ocfs2_dentry_revalidate() by
225 * tracking these?
226 */
227 if (!inode)
228 return 0;
229
230 if (d_really_is_negative(dentry) && dentry->d_fsdata) {
231 /* Converting a negative dentry to positive
232 Clear dentry->d_fsdata */
233 dentry->d_fsdata = dl = NULL;
234 }
235
236 if (dl) {
237 mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
238 " \"%pd\": old parent: %llu, new: %llu\n",
239 dentry,
240 (unsigned long long)parent_blkno,
241 (unsigned long long)dl->dl_parent_blkno);
242 return 0;
243 }
244
245 alias = ocfs2_find_local_alias(inode, parent_blkno, skip_unhashed: 0);
246 if (alias) {
247 /*
248 * Great, an alias exists, which means we must have a
249 * dentry lock already. We can just grab the lock off
250 * the alias and add it to the list.
251 *
252 * We're depending here on the fact that this dentry
253 * was found and exists in the dcache and so must have
254 * a reference to the dentry_lock because we can't
255 * race creates. Final dput() cannot happen on it
256 * since we have it pinned, so our reference is safe.
257 */
258 dl = alias->d_fsdata;
259 mlog_bug_on_msg(!dl, "parent %llu, ino %llu\n",
260 (unsigned long long)parent_blkno,
261 (unsigned long long)OCFS2_I(inode)->ip_blkno);
262
263 mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
264 " \"%pd\": old parent: %llu, new: %llu\n",
265 dentry,
266 (unsigned long long)parent_blkno,
267 (unsigned long long)dl->dl_parent_blkno);
268
269 trace_ocfs2_dentry_attach_lock_found(name: dl->dl_lockres.l_name,
270 parent: (unsigned long long)parent_blkno,
271 ino: (unsigned long long)OCFS2_I(inode)->ip_blkno);
272
273 goto out_attach;
274 }
275
276 /*
277 * There are no other aliases
278 */
279 dl = kmalloc(size: sizeof(*dl), GFP_NOFS);
280 if (!dl) {
281 ret = -ENOMEM;
282 mlog_errno(ret);
283 return ret;
284 }
285
286 dl->dl_count = 0;
287 /*
288 * Does this have to happen below, for all attaches, in case
289 * the struct inode gets blown away by the downconvert thread?
290 */
291 dl->dl_inode = igrab(inode);
292 dl->dl_parent_blkno = parent_blkno;
293 ocfs2_dentry_lock_res_init(dl, parent: parent_blkno, inode);
294
295out_attach:
296 spin_lock(lock: &dentry_attach_lock);
297 if (unlikely(dentry->d_fsdata && !alias)) {
298 /* d_fsdata is set by a racing thread which is doing
299 * the same thing as this thread is doing. Leave the racing
300 * thread going ahead and we return here.
301 */
302 spin_unlock(lock: &dentry_attach_lock);
303 iput(dl->dl_inode);
304 ocfs2_lock_res_free(res: &dl->dl_lockres);
305 kfree(objp: dl);
306 return 0;
307 }
308
309 dentry->d_fsdata = dl;
310 dl->dl_count++;
311 spin_unlock(lock: &dentry_attach_lock);
312
313 /*
314 * This actually gets us our PRMODE level lock. From now on,
315 * we'll have a notification if one of these names is
316 * destroyed on another node.
317 */
318 ret = ocfs2_dentry_lock(dentry, ex: 0);
319 if (!ret)
320 ocfs2_dentry_unlock(dentry, ex: 0);
321 else
322 mlog_errno(ret);
323
324 /*
325 * In case of error, manually free the allocation and do the iput().
326 * We need to do this because error here means no d_instantiate(),
327 * which means iput() will not be called during dput(dentry).
328 */
329 if (ret < 0 && !alias) {
330 ocfs2_lock_res_free(res: &dl->dl_lockres);
331 BUG_ON(dl->dl_count != 1);
332 spin_lock(lock: &dentry_attach_lock);
333 dentry->d_fsdata = NULL;
334 spin_unlock(lock: &dentry_attach_lock);
335 kfree(objp: dl);
336 iput(inode);
337 }
338
339 dput(alias);
340
341 return ret;
342}
343
344/*
345 * ocfs2_dentry_iput() and friends.
346 *
347 * At this point, our particular dentry is detached from the inodes
348 * alias list, so there's no way that the locking code can find it.
349 *
350 * The interesting stuff happens when we determine that our lock needs
351 * to go away because this is the last subdir alias in the
352 * system. This function needs to handle a couple things:
353 *
354 * 1) Synchronizing lock shutdown with the downconvert threads. This
355 * is already handled for us via the lockres release drop function
356 * called in ocfs2_release_dentry_lock()
357 *
358 * 2) A race may occur when we're doing our lock shutdown and
359 * another process wants to create a new dentry lock. Right now we
360 * let them race, which means that for a very short while, this
361 * node might have two locks on a lock resource. This should be a
362 * problem though because one of them is in the process of being
363 * thrown out.
364 */
365static void ocfs2_drop_dentry_lock(struct ocfs2_super *osb,
366 struct ocfs2_dentry_lock *dl)
367{
368 iput(dl->dl_inode);
369 ocfs2_simple_drop_lockres(osb, lockres: &dl->dl_lockres);
370 ocfs2_lock_res_free(res: &dl->dl_lockres);
371 kfree(objp: dl);
372}
373
374void ocfs2_dentry_lock_put(struct ocfs2_super *osb,
375 struct ocfs2_dentry_lock *dl)
376{
377 int unlock = 0;
378
379 BUG_ON(dl->dl_count == 0);
380
381 spin_lock(lock: &dentry_attach_lock);
382 dl->dl_count--;
383 unlock = !dl->dl_count;
384 spin_unlock(lock: &dentry_attach_lock);
385
386 if (unlock)
387 ocfs2_drop_dentry_lock(osb, dl);
388}
389
390static void ocfs2_dentry_iput(struct dentry *dentry, struct inode *inode)
391{
392 struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
393
394 if (!dl) {
395 /*
396 * No dentry lock is ok if we're disconnected or
397 * unhashed.
398 */
399 if (!(dentry->d_flags & DCACHE_DISCONNECTED) &&
400 !d_unhashed(dentry)) {
401 unsigned long long ino = 0ULL;
402 if (inode)
403 ino = (unsigned long long)OCFS2_I(inode)->ip_blkno;
404 mlog(ML_ERROR, "Dentry is missing cluster lock. "
405 "inode: %llu, d_flags: 0x%x, d_name: %pd\n",
406 ino, dentry->d_flags, dentry);
407 }
408
409 goto out;
410 }
411
412 mlog_bug_on_msg(dl->dl_count == 0, "dentry: %pd, count: %u\n",
413 dentry, dl->dl_count);
414
415 ocfs2_dentry_lock_put(OCFS2_SB(dentry->d_sb), dl);
416
417out:
418 iput(inode);
419}
420
421/*
422 * d_move(), but keep the locks in sync.
423 *
424 * When we are done, "dentry" will have the parent dir and name of
425 * "target", which will be thrown away.
426 *
427 * We manually update the lock of "dentry" if need be.
428 *
429 * "target" doesn't have it's dentry lock touched - we allow the later
430 * dput() to handle this for us.
431 *
432 * This is called during ocfs2_rename(), while holding parent
433 * directory locks. The dentries have already been deleted on other
434 * nodes via ocfs2_remote_dentry_delete().
435 *
436 * Normally, the VFS handles the d_move() for the file system, after
437 * the ->rename() callback. OCFS2 wants to handle this internally, so
438 * the new lock can be created atomically with respect to the cluster.
439 */
440void ocfs2_dentry_move(struct dentry *dentry, struct dentry *target,
441 struct inode *old_dir, struct inode *new_dir)
442{
443 int ret;
444 struct ocfs2_super *osb = OCFS2_SB(old_dir->i_sb);
445 struct inode *inode = d_inode(dentry);
446
447 /*
448 * Move within the same directory, so the actual lock info won't
449 * change.
450 *
451 * XXX: Is there any advantage to dropping the lock here?
452 */
453 if (old_dir == new_dir)
454 goto out_move;
455
456 ocfs2_dentry_lock_put(osb, dl: dentry->d_fsdata);
457
458 dentry->d_fsdata = NULL;
459 ret = ocfs2_dentry_attach_lock(dentry, inode, parent_blkno: OCFS2_I(inode: new_dir)->ip_blkno);
460 if (ret)
461 mlog_errno(ret);
462
463out_move:
464 d_move(dentry, target);
465}
466
467const struct dentry_operations ocfs2_dentry_ops = {
468 .d_revalidate = ocfs2_dentry_revalidate,
469 .d_iput = ocfs2_dentry_iput,
470};
471

source code of linux/fs/ocfs2/dcache.c