Root/fs/ocfs2/dcache.c

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
43void 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
52static int ocfs2_dentry_revalidate(struct dentry *dentry,
53                   struct nameidata *nd)
54{
55    struct inode *inode;
56    int ret = 0; /* if all else fails, just return false */
57    struct ocfs2_super *osb;
58
59    if (nd && nd->flags & LOOKUP_RCU)
60        return -ECHILD;
61
62    inode = dentry->d_inode;
63    osb = OCFS2_SB(dentry->d_sb);
64
65    trace_ocfs2_dentry_revalidate(dentry, dentry->d_name.len,
66                      dentry->d_name.name);
67
68    /* For a negative dentry -
69     * check the generation number of the parent and compare with the
70     * one stored in the inode.
71     */
72    if (inode == NULL) {
73        unsigned long gen = (unsigned long) dentry->d_fsdata;
74        unsigned long pgen =
75            OCFS2_I(dentry->d_parent->d_inode)->ip_dir_lock_gen;
76
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
121valid:
122    ret = 1;
123
124bail:
125    trace_ocfs2_dentry_revalidate_ret(ret);
126    return ret;
127}
128
129static 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 */
169struct dentry *ocfs2_find_local_alias(struct inode *inode,
170                      u64 parent_blkno,
171                      int skip_unhashed)
172{
173    struct list_head *p;
174    struct dentry *dentry = NULL;
175
176    spin_lock(&inode->i_lock);
177    list_for_each(p, &inode->i_dentry) {
178        dentry = list_entry(p, struct dentry, d_alias);
179
180        spin_lock(&dentry->d_lock);
181        if (ocfs2_match_dentry(dentry, parent_blkno, skip_unhashed)) {
182            trace_ocfs2_find_local_alias(dentry->d_name.len,
183                             dentry->d_name.name);
184
185            dget_dlock(dentry);
186            spin_unlock(&dentry->d_lock);
187            break;
188        }
189        spin_unlock(&dentry->d_lock);
190
191        dentry = NULL;
192    }
193
194    spin_unlock(&inode->i_lock);
195
196    return dentry;
197}
198
199DEFINE_SPINLOCK(dentry_attach_lock);
200
201/*
202 * Attach this dentry to a cluster lock.
203 *
204 * Dentry locks cover all links in a given directory to a particular
205 * inode. We do this so that ocfs2 can build a lock name which all
206 * nodes in the cluster can agree on at all times. Shoving full names
207 * in the cluster lock won't work due to size restrictions. Covering
208 * links inside of a directory is a good compromise because it still
209 * allows us to use the parent directory lock to synchronize
210 * operations.
211 *
212 * Call this function with the parent dir semaphore and the parent dir
213 * cluster lock held.
214 *
215 * The dir semaphore will protect us from having to worry about
216 * concurrent processes on our node trying to attach a lock at the
217 * same time.
218 *
219 * The dir cluster lock (held at either PR or EX mode) protects us
220 * from unlink and rename on other nodes.
221 *
222 * A dput() can happen asynchronously due to pruning, so we cover
223 * attaching and detaching the dentry lock with a
224 * dentry_attach_lock.
225 *
226 * A node which has done lookup on a name retains a protected read
227 * lock until final dput. If the user requests and unlink or rename,
228 * the protected read is upgraded to an exclusive lock. Other nodes
229 * who have seen the dentry will then be informed that they need to
230 * downgrade their lock, which will involve d_delete on the
231 * dentry. This happens in ocfs2_dentry_convert_worker().
232 */
233int ocfs2_dentry_attach_lock(struct dentry *dentry,
234                 struct inode *inode,
235                 u64 parent_blkno)
236{
237    int ret;
238    struct dentry *alias;
239    struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
240
241    trace_ocfs2_dentry_attach_lock(dentry->d_name.len, dentry->d_name.name,
242                       (unsigned long long)parent_blkno, dl);
243
244    /*
245     * Negative dentry. We ignore these for now.
246     *
247     * XXX: Could we can improve ocfs2_dentry_revalidate() by
248     * tracking these?
249     */
250    if (!inode)
251        return 0;
252
253    if (!dentry->d_inode && dentry->d_fsdata) {
254        /* Converting a negative dentry to positive
255           Clear dentry->d_fsdata */
256        dentry->d_fsdata = dl = NULL;
257    }
258
259    if (dl) {
260        mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
261                " \"%.*s\": old parent: %llu, new: %llu\n",
262                dentry->d_name.len, dentry->d_name.name,
263                (unsigned long long)parent_blkno,
264                (unsigned long long)dl->dl_parent_blkno);
265        return 0;
266    }
267
268    alias = ocfs2_find_local_alias(inode, parent_blkno, 0);
269    if (alias) {
270        /*
271         * Great, an alias exists, which means we must have a
272         * dentry lock already. We can just grab the lock off
273         * the alias and add it to the list.
274         *
275         * We're depending here on the fact that this dentry
276         * was found and exists in the dcache and so must have
277         * a reference to the dentry_lock because we can't
278         * race creates. Final dput() cannot happen on it
279         * since we have it pinned, so our reference is safe.
280         */
281        dl = alias->d_fsdata;
282        mlog_bug_on_msg(!dl, "parent %llu, ino %llu\n",
283                (unsigned long long)parent_blkno,
284                (unsigned long long)OCFS2_I(inode)->ip_blkno);
285
286        mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
287                " \"%.*s\": old parent: %llu, new: %llu\n",
288                dentry->d_name.len, dentry->d_name.name,
289                (unsigned long long)parent_blkno,
290                (unsigned long long)dl->dl_parent_blkno);
291
292        trace_ocfs2_dentry_attach_lock_found(dl->dl_lockres.l_name,
293                (unsigned long long)parent_blkno,
294                (unsigned long long)OCFS2_I(inode)->ip_blkno);
295
296        goto out_attach;
297    }
298
299    /*
300     * There are no other aliases
301     */
302    dl = kmalloc(sizeof(*dl), GFP_NOFS);
303    if (!dl) {
304        ret = -ENOMEM;
305        mlog_errno(ret);
306        return ret;
307    }
308
309    dl->dl_count = 0;
310    /*
311     * Does this have to happen below, for all attaches, in case
312     * the struct inode gets blown away by the downconvert thread?
313     */
314    dl->dl_inode = igrab(inode);
315    dl->dl_parent_blkno = parent_blkno;
316    ocfs2_dentry_lock_res_init(dl, parent_blkno, inode);
317
318out_attach:
319    spin_lock(&dentry_attach_lock);
320    dentry->d_fsdata = dl;
321    dl->dl_count++;
322    spin_unlock(&dentry_attach_lock);
323
324    /*
325     * This actually gets us our PRMODE level lock. From now on,
326     * we'll have a notification if one of these names is
327     * destroyed on another node.
328     */
329    ret = ocfs2_dentry_lock(dentry, 0);
330    if (!ret)
331        ocfs2_dentry_unlock(dentry, 0);
332    else
333        mlog_errno(ret);
334
335    /*
336     * In case of error, manually free the allocation and do the iput().
337     * We need to do this because error here means no d_instantiate(),
338     * which means iput() will not be called during dput(dentry).
339     */
340    if (ret < 0 && !alias) {
341        ocfs2_lock_res_free(&dl->dl_lockres);
342        BUG_ON(dl->dl_count != 1);
343        spin_lock(&dentry_attach_lock);
344        dentry->d_fsdata = NULL;
345        spin_unlock(&dentry_attach_lock);
346        kfree(dl);
347        iput(inode);
348    }
349
350    dput(alias);
351
352    return ret;
353}
354
355DEFINE_SPINLOCK(dentry_list_lock);
356
357/* We limit the number of dentry locks to drop in one go. We have
358 * this limit so that we don't starve other users of ocfs2_wq. */
359#define DL_INODE_DROP_COUNT 64
360
361/* Drop inode references from dentry locks */
362static void __ocfs2_drop_dl_inodes(struct ocfs2_super *osb, int drop_count)
363{
364    struct ocfs2_dentry_lock *dl;
365
366    spin_lock(&dentry_list_lock);
367    while (osb->dentry_lock_list && (drop_count < 0 || drop_count--)) {
368        dl = osb->dentry_lock_list;
369        osb->dentry_lock_list = dl->dl_next;
370        spin_unlock(&dentry_list_lock);
371        iput(dl->dl_inode);
372        kfree(dl);
373        spin_lock(&dentry_list_lock);
374    }
375    spin_unlock(&dentry_list_lock);
376}
377
378void ocfs2_drop_dl_inodes(struct work_struct *work)
379{
380    struct ocfs2_super *osb = container_of(work, struct ocfs2_super,
381                           dentry_lock_work);
382
383    __ocfs2_drop_dl_inodes(osb, DL_INODE_DROP_COUNT);
384    /*
385     * Don't queue dropping if umount is in progress. We flush the
386     * list in ocfs2_dismount_volume
387     */
388    spin_lock(&dentry_list_lock);
389    if (osb->dentry_lock_list &&
390        !ocfs2_test_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED))
391        queue_work(ocfs2_wq, &osb->dentry_lock_work);
392    spin_unlock(&dentry_list_lock);
393}
394
395/* Flush the whole work queue */
396void ocfs2_drop_all_dl_inodes(struct ocfs2_super *osb)
397{
398    __ocfs2_drop_dl_inodes(osb, -1);
399}
400
401/*
402 * ocfs2_dentry_iput() and friends.
403 *
404 * At this point, our particular dentry is detached from the inodes
405 * alias list, so there's no way that the locking code can find it.
406 *
407 * The interesting stuff happens when we determine that our lock needs
408 * to go away because this is the last subdir alias in the
409 * system. This function needs to handle a couple things:
410 *
411 * 1) Synchronizing lock shutdown with the downconvert threads. This
412 * is already handled for us via the lockres release drop function
413 * called in ocfs2_release_dentry_lock()
414 *
415 * 2) A race may occur when we're doing our lock shutdown and
416 * another process wants to create a new dentry lock. Right now we
417 * let them race, which means that for a very short while, this
418 * node might have two locks on a lock resource. This should be a
419 * problem though because one of them is in the process of being
420 * thrown out.
421 */
422static void ocfs2_drop_dentry_lock(struct ocfs2_super *osb,
423                   struct ocfs2_dentry_lock *dl)
424{
425    ocfs2_simple_drop_lockres(osb, &dl->dl_lockres);
426    ocfs2_lock_res_free(&dl->dl_lockres);
427
428    /* We leave dropping of inode reference to ocfs2_wq as that can
429     * possibly lead to inode deletion which gets tricky */
430    spin_lock(&dentry_list_lock);
431    if (!osb->dentry_lock_list &&
432        !ocfs2_test_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED))
433        queue_work(ocfs2_wq, &osb->dentry_lock_work);
434    dl->dl_next = osb->dentry_lock_list;
435    osb->dentry_lock_list = dl;
436    spin_unlock(&dentry_list_lock);
437}
438
439void ocfs2_dentry_lock_put(struct ocfs2_super *osb,
440               struct ocfs2_dentry_lock *dl)
441{
442    int unlock;
443
444    BUG_ON(dl->dl_count == 0);
445
446    spin_lock(&dentry_attach_lock);
447    dl->dl_count--;
448    unlock = !dl->dl_count;
449    spin_unlock(&dentry_attach_lock);
450
451    if (unlock)
452        ocfs2_drop_dentry_lock(osb, dl);
453}
454
455static void ocfs2_dentry_iput(struct dentry *dentry, struct inode *inode)
456{
457    struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
458
459    if (!dl) {
460        /*
461         * No dentry lock is ok if we're disconnected or
462         * unhashed.
463         */
464        if (!(dentry->d_flags & DCACHE_DISCONNECTED) &&
465            !d_unhashed(dentry)) {
466            unsigned long long ino = 0ULL;
467            if (inode)
468                ino = (unsigned long long)OCFS2_I(inode)->ip_blkno;
469            mlog(ML_ERROR, "Dentry is missing cluster lock. "
470                 "inode: %llu, d_flags: 0x%x, d_name: %.*s\n",
471                 ino, dentry->d_flags, dentry->d_name.len,
472                 dentry->d_name.name);
473        }
474
475        goto out;
476    }
477
478    mlog_bug_on_msg(dl->dl_count == 0, "dentry: %.*s, count: %u\n",
479            dentry->d_name.len, dentry->d_name.name,
480            dl->dl_count);
481
482    ocfs2_dentry_lock_put(OCFS2_SB(dentry->d_sb), dl);
483
484out:
485    iput(inode);
486}
487
488/*
489 * d_move(), but keep the locks in sync.
490 *
491 * When we are done, "dentry" will have the parent dir and name of
492 * "target", which will be thrown away.
493 *
494 * We manually update the lock of "dentry" if need be.
495 *
496 * "target" doesn't have it's dentry lock touched - we allow the later
497 * dput() to handle this for us.
498 *
499 * This is called during ocfs2_rename(), while holding parent
500 * directory locks. The dentries have already been deleted on other
501 * nodes via ocfs2_remote_dentry_delete().
502 *
503 * Normally, the VFS handles the d_move() for the file system, after
504 * the ->rename() callback. OCFS2 wants to handle this internally, so
505 * the new lock can be created atomically with respect to the cluster.
506 */
507void ocfs2_dentry_move(struct dentry *dentry, struct dentry *target,
508               struct inode *old_dir, struct inode *new_dir)
509{
510    int ret;
511    struct ocfs2_super *osb = OCFS2_SB(old_dir->i_sb);
512    struct inode *inode = dentry->d_inode;
513
514    /*
515     * Move within the same directory, so the actual lock info won't
516     * change.
517     *
518     * XXX: Is there any advantage to dropping the lock here?
519     */
520    if (old_dir == new_dir)
521        goto out_move;
522
523    ocfs2_dentry_lock_put(osb, dentry->d_fsdata);
524
525    dentry->d_fsdata = NULL;
526    ret = ocfs2_dentry_attach_lock(dentry, inode, OCFS2_I(new_dir)->ip_blkno);
527    if (ret)
528        mlog_errno(ret);
529
530out_move:
531    d_move(dentry, target);
532}
533
534const struct dentry_operations ocfs2_dentry_ops = {
535    .d_revalidate = ocfs2_dentry_revalidate,
536    .d_iput = ocfs2_dentry_iput,
537};
538

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