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 "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 };