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
  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,
  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
 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 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
 199 DEFINE_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  */
 233 int 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
 318 out_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
 355 DEFINE_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 */
 362 static 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
 378 void 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 */
 396 void 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  */
 422 static 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
 439 void 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
 455 static 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
 484 out:
 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  */
 507 void 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
 530 out_move:
 531         d_move(dentry, target);
 532 }
 533
 534 const struct dentry_operations ocfs2_dentry_ops = {
 535         .d_revalidate           = ocfs2_dentry_revalidate,
 536         .d_iput                 = ocfs2_dentry_iput,
 537 };