linux/fs/ceph/snap.c
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   1#include <linux/ceph/ceph_debug.h>
   2
   3#include <linux/sort.h>
   4#include <linux/slab.h>
   5
   6#include "super.h"
   7#include "mds_client.h"
   8
   9#include <linux/ceph/decode.h>
  10
  11/*
  12 * Snapshots in ceph are driven in large part by cooperation from the
  13 * client.  In contrast to local file systems or file servers that
  14 * implement snapshots at a single point in the system, ceph's
  15 * distributed access to storage requires clients to help decide
  16 * whether a write logically occurs before or after a recently created
  17 * snapshot.
  18 *
  19 * This provides a perfect instantanous client-wide snapshot.  Between
  20 * clients, however, snapshots may appear to be applied at slightly
  21 * different points in time, depending on delays in delivering the
  22 * snapshot notification.
  23 *
  24 * Snapshots are _not_ file system-wide.  Instead, each snapshot
  25 * applies to the subdirectory nested beneath some directory.  This
  26 * effectively divides the hierarchy into multiple "realms," where all
  27 * of the files contained by each realm share the same set of
  28 * snapshots.  An individual realm's snap set contains snapshots
  29 * explicitly created on that realm, as well as any snaps in its
  30 * parent's snap set _after_ the point at which the parent became it's
  31 * parent (due to, say, a rename).  Similarly, snaps from prior parents
  32 * during the time intervals during which they were the parent are included.
  33 *
  34 * The client is spared most of this detail, fortunately... it must only
  35 * maintains a hierarchy of realms reflecting the current parent/child
  36 * realm relationship, and for each realm has an explicit list of snaps
  37 * inherited from prior parents.
  38 *
  39 * A snap_realm struct is maintained for realms containing every inode
  40 * with an open cap in the system.  (The needed snap realm information is
  41 * provided by the MDS whenever a cap is issued, i.e., on open.)  A 'seq'
  42 * version number is used to ensure that as realm parameters change (new
  43 * snapshot, new parent, etc.) the client's realm hierarchy is updated.
  44 *
  45 * The realm hierarchy drives the generation of a 'snap context' for each
  46 * realm, which simply lists the resulting set of snaps for the realm.  This
  47 * is attached to any writes sent to OSDs.
  48 */
  49/*
  50 * Unfortunately error handling is a bit mixed here.  If we get a snap
  51 * update, but don't have enough memory to update our realm hierarchy,
  52 * it's not clear what we can do about it (besides complaining to the
  53 * console).
  54 */
  55
  56
  57/*
  58 * increase ref count for the realm
  59 *
  60 * caller must hold snap_rwsem for write.
  61 */
  62void ceph_get_snap_realm(struct ceph_mds_client *mdsc,
  63                         struct ceph_snap_realm *realm)
  64{
  65        dout("get_realm %p %d -> %d\n", realm,
  66             atomic_read(&realm->nref), atomic_read(&realm->nref)+1);
  67        /*
  68         * since we _only_ increment realm refs or empty the empty
  69         * list with snap_rwsem held, adjusting the empty list here is
  70         * safe.  we do need to protect against concurrent empty list
  71         * additions, however.
  72         */
  73        if (atomic_read(&realm->nref) == 0) {
  74                spin_lock(&mdsc->snap_empty_lock);
  75                list_del_init(&realm->empty_item);
  76                spin_unlock(&mdsc->snap_empty_lock);
  77        }
  78
  79        atomic_inc(&realm->nref);
  80}
  81
  82static void __insert_snap_realm(struct rb_root *root,
  83                                struct ceph_snap_realm *new)
  84{
  85        struct rb_node **p = &root->rb_node;
  86        struct rb_node *parent = NULL;
  87        struct ceph_snap_realm *r = NULL;
  88
  89        while (*p) {
  90                parent = *p;
  91                r = rb_entry(parent, struct ceph_snap_realm, node);
  92                if (new->ino < r->ino)
  93                        p = &(*p)->rb_left;
  94                else if (new->ino > r->ino)
  95                        p = &(*p)->rb_right;
  96                else
  97                        BUG();
  98        }
  99
 100        rb_link_node(&new->node, parent, p);
 101        rb_insert_color(&new->node, root);
 102}
 103
 104/*
 105 * create and get the realm rooted at @ino and bump its ref count.
 106 *
 107 * caller must hold snap_rwsem for write.
 108 */
 109static struct ceph_snap_realm *ceph_create_snap_realm(
 110        struct ceph_mds_client *mdsc,
 111        u64 ino)
 112{
 113        struct ceph_snap_realm *realm;
 114
 115        realm = kzalloc(sizeof(*realm), GFP_NOFS);
 116        if (!realm)
 117                return ERR_PTR(-ENOMEM);
 118
 119        atomic_set(&realm->nref, 0);    /* tree does not take a ref */
 120        realm->ino = ino;
 121        INIT_LIST_HEAD(&realm->children);
 122        INIT_LIST_HEAD(&realm->child_item);
 123        INIT_LIST_HEAD(&realm->empty_item);
 124        INIT_LIST_HEAD(&realm->dirty_item);
 125        INIT_LIST_HEAD(&realm->inodes_with_caps);
 126        spin_lock_init(&realm->inodes_with_caps_lock);
 127        __insert_snap_realm(&mdsc->snap_realms, realm);
 128        dout("create_snap_realm %llx %p\n", realm->ino, realm);
 129        return realm;
 130}
 131
 132/*
 133 * lookup the realm rooted at @ino.
 134 *
 135 * caller must hold snap_rwsem for write.
 136 */
 137struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc,
 138                                               u64 ino)
 139{
 140        struct rb_node *n = mdsc->snap_realms.rb_node;
 141        struct ceph_snap_realm *r;
 142
 143        while (n) {
 144                r = rb_entry(n, struct ceph_snap_realm, node);
 145                if (ino < r->ino)
 146                        n = n->rb_left;
 147                else if (ino > r->ino)
 148                        n = n->rb_right;
 149                else {
 150                        dout("lookup_snap_realm %llx %p\n", r->ino, r);
 151                        return r;
 152                }
 153        }
 154        return NULL;
 155}
 156
 157static void __put_snap_realm(struct ceph_mds_client *mdsc,
 158                             struct ceph_snap_realm *realm);
 159
 160/*
 161 * called with snap_rwsem (write)
 162 */
 163static void __destroy_snap_realm(struct ceph_mds_client *mdsc,
 164                                 struct ceph_snap_realm *realm)
 165{
 166        dout("__destroy_snap_realm %p %llx\n", realm, realm->ino);
 167
 168        rb_erase(&realm->node, &mdsc->snap_realms);
 169
 170        if (realm->parent) {
 171                list_del_init(&realm->child_item);
 172                __put_snap_realm(mdsc, realm->parent);
 173        }
 174
 175        kfree(realm->prior_parent_snaps);
 176        kfree(realm->snaps);
 177        ceph_put_snap_context(realm->cached_context);
 178        kfree(realm);
 179}
 180
 181/*
 182 * caller holds snap_rwsem (write)
 183 */
 184static void __put_snap_realm(struct ceph_mds_client *mdsc,
 185                             struct ceph_snap_realm *realm)
 186{
 187        dout("__put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
 188             atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
 189        if (atomic_dec_and_test(&realm->nref))
 190                __destroy_snap_realm(mdsc, realm);
 191}
 192
 193/*
 194 * caller needn't hold any locks
 195 */
 196void ceph_put_snap_realm(struct ceph_mds_client *mdsc,
 197                         struct ceph_snap_realm *realm)
 198{
 199        dout("put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
 200             atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
 201        if (!atomic_dec_and_test(&realm->nref))
 202                return;
 203
 204        if (down_write_trylock(&mdsc->snap_rwsem)) {
 205                __destroy_snap_realm(mdsc, realm);
 206                up_write(&mdsc->snap_rwsem);
 207        } else {
 208                spin_lock(&mdsc->snap_empty_lock);
 209                list_add(&realm->empty_item, &mdsc->snap_empty);
 210                spin_unlock(&mdsc->snap_empty_lock);
 211        }
 212}
 213
 214/*
 215 * Clean up any realms whose ref counts have dropped to zero.  Note
 216 * that this does not include realms who were created but not yet
 217 * used.
 218 *
 219 * Called under snap_rwsem (write)
 220 */
 221static void __cleanup_empty_realms(struct ceph_mds_client *mdsc)
 222{
 223        struct ceph_snap_realm *realm;
 224
 225        spin_lock(&mdsc->snap_empty_lock);
 226        while (!list_empty(&mdsc->snap_empty)) {
 227                realm = list_first_entry(&mdsc->snap_empty,
 228                                   struct ceph_snap_realm, empty_item);
 229                list_del(&realm->empty_item);
 230                spin_unlock(&mdsc->snap_empty_lock);
 231                __destroy_snap_realm(mdsc, realm);
 232                spin_lock(&mdsc->snap_empty_lock);
 233        }
 234        spin_unlock(&mdsc->snap_empty_lock);
 235}
 236
 237void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc)
 238{
 239        down_write(&mdsc->snap_rwsem);
 240        __cleanup_empty_realms(mdsc);
 241        up_write(&mdsc->snap_rwsem);
 242}
 243
 244/*
 245 * adjust the parent realm of a given @realm.  adjust child list, and parent
 246 * pointers, and ref counts appropriately.
 247 *
 248 * return true if parent was changed, 0 if unchanged, <0 on error.
 249 *
 250 * caller must hold snap_rwsem for write.
 251 */
 252static int adjust_snap_realm_parent(struct ceph_mds_client *mdsc,
 253                                    struct ceph_snap_realm *realm,
 254                                    u64 parentino)
 255{
 256        struct ceph_snap_realm *parent;
 257
 258        if (realm->parent_ino == parentino)
 259                return 0;
 260
 261        parent = ceph_lookup_snap_realm(mdsc, parentino);
 262        if (!parent) {
 263                parent = ceph_create_snap_realm(mdsc, parentino);
 264                if (IS_ERR(parent))
 265                        return PTR_ERR(parent);
 266        }
 267        dout("adjust_snap_realm_parent %llx %p: %llx %p -> %llx %p\n",
 268             realm->ino, realm, realm->parent_ino, realm->parent,
 269             parentino, parent);
 270        if (realm->parent) {
 271                list_del_init(&realm->child_item);
 272                ceph_put_snap_realm(mdsc, realm->parent);
 273        }
 274        realm->parent_ino = parentino;
 275        realm->parent = parent;
 276        ceph_get_snap_realm(mdsc, parent);
 277        list_add(&realm->child_item, &parent->children);
 278        return 1;
 279}
 280
 281
 282static int cmpu64_rev(const void *a, const void *b)
 283{
 284        if (*(u64 *)a < *(u64 *)b)
 285                return 1;
 286        if (*(u64 *)a > *(u64 *)b)
 287                return -1;
 288        return 0;
 289}
 290
 291/*
 292 * build the snap context for a given realm.
 293 */
 294static int build_snap_context(struct ceph_snap_realm *realm)
 295{
 296        struct ceph_snap_realm *parent = realm->parent;
 297        struct ceph_snap_context *snapc;
 298        int err = 0;
 299        u32 num = realm->num_prior_parent_snaps + realm->num_snaps;
 300
 301        /*
 302         * build parent context, if it hasn't been built.
 303         * conservatively estimate that all parent snaps might be
 304         * included by us.
 305         */
 306        if (parent) {
 307                if (!parent->cached_context) {
 308                        err = build_snap_context(parent);
 309                        if (err)
 310                                goto fail;
 311                }
 312                num += parent->cached_context->num_snaps;
 313        }
 314
 315        /* do i actually need to update?  not if my context seq
 316           matches realm seq, and my parents' does to.  (this works
 317           because we rebuild_snap_realms() works _downward_ in
 318           hierarchy after each update.) */
 319        if (realm->cached_context &&
 320            realm->cached_context->seq == realm->seq &&
 321            (!parent ||
 322             realm->cached_context->seq >= parent->cached_context->seq)) {
 323                dout("build_snap_context %llx %p: %p seq %lld (%u snaps)"
 324                     " (unchanged)\n",
 325                     realm->ino, realm, realm->cached_context,
 326                     realm->cached_context->seq,
 327                     (unsigned int) realm->cached_context->num_snaps);
 328                return 0;
 329        }
 330
 331        /* alloc new snap context */
 332        err = -ENOMEM;
 333        if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
 334                goto fail;
 335        snapc = kzalloc(sizeof(*snapc) + num*sizeof(u64), GFP_NOFS);
 336        if (!snapc)
 337                goto fail;
 338        atomic_set(&snapc->nref, 1);
 339
 340        /* build (reverse sorted) snap vector */
 341        num = 0;
 342        snapc->seq = realm->seq;
 343        if (parent) {
 344                u32 i;
 345
 346                /* include any of parent's snaps occurring _after_ my
 347                   parent became my parent */
 348                for (i = 0; i < parent->cached_context->num_snaps; i++)
 349                        if (parent->cached_context->snaps[i] >=
 350                            realm->parent_since)
 351                                snapc->snaps[num++] =
 352                                        parent->cached_context->snaps[i];
 353                if (parent->cached_context->seq > snapc->seq)
 354                        snapc->seq = parent->cached_context->seq;
 355        }
 356        memcpy(snapc->snaps + num, realm->snaps,
 357               sizeof(u64)*realm->num_snaps);
 358        num += realm->num_snaps;
 359        memcpy(snapc->snaps + num, realm->prior_parent_snaps,
 360               sizeof(u64)*realm->num_prior_parent_snaps);
 361        num += realm->num_prior_parent_snaps;
 362
 363        sort(snapc->snaps, num, sizeof(u64), cmpu64_rev, NULL);
 364        snapc->num_snaps = num;
 365        dout("build_snap_context %llx %p: %p seq %lld (%u snaps)\n",
 366             realm->ino, realm, snapc, snapc->seq,
 367             (unsigned int) snapc->num_snaps);
 368
 369        if (realm->cached_context)
 370                ceph_put_snap_context(realm->cached_context);
 371        realm->cached_context = snapc;
 372        return 0;
 373
 374fail:
 375        /*
 376         * if we fail, clear old (incorrect) cached_context... hopefully
 377         * we'll have better luck building it later
 378         */
 379        if (realm->cached_context) {
 380                ceph_put_snap_context(realm->cached_context);
 381                realm->cached_context = NULL;
 382        }
 383        pr_err("build_snap_context %llx %p fail %d\n", realm->ino,
 384               realm, err);
 385        return err;
 386}
 387
 388/*
 389 * rebuild snap context for the given realm and all of its children.
 390 */
 391static void rebuild_snap_realms(struct ceph_snap_realm *realm)
 392{
 393        struct ceph_snap_realm *child;
 394
 395        dout("rebuild_snap_realms %llx %p\n", realm->ino, realm);
 396        build_snap_context(realm);
 397
 398        list_for_each_entry(child, &realm->children, child_item)
 399                rebuild_snap_realms(child);
 400}
 401
 402
 403/*
 404 * helper to allocate and decode an array of snapids.  free prior
 405 * instance, if any.
 406 */
 407static int dup_array(u64 **dst, __le64 *src, u32 num)
 408{
 409        u32 i;
 410
 411        kfree(*dst);
 412        if (num) {
 413                *dst = kcalloc(num, sizeof(u64), GFP_NOFS);
 414                if (!*dst)
 415                        return -ENOMEM;
 416                for (i = 0; i < num; i++)
 417                        (*dst)[i] = get_unaligned_le64(src + i);
 418        } else {
 419                *dst = NULL;
 420        }
 421        return 0;
 422}
 423
 424
 425/*
 426 * When a snapshot is applied, the size/mtime inode metadata is queued
 427 * in a ceph_cap_snap (one for each snapshot) until writeback
 428 * completes and the metadata can be flushed back to the MDS.
 429 *
 430 * However, if a (sync) write is currently in-progress when we apply
 431 * the snapshot, we have to wait until the write succeeds or fails
 432 * (and a final size/mtime is known).  In this case the
 433 * cap_snap->writing = 1, and is said to be "pending."  When the write
 434 * finishes, we __ceph_finish_cap_snap().
 435 *
 436 * Caller must hold snap_rwsem for read (i.e., the realm topology won't
 437 * change).
 438 */
 439void ceph_queue_cap_snap(struct ceph_inode_info *ci)
 440{
 441        struct inode *inode = &ci->vfs_inode;
 442        struct ceph_cap_snap *capsnap;
 443        int used, dirty;
 444
 445        capsnap = kzalloc(sizeof(*capsnap), GFP_NOFS);
 446        if (!capsnap) {
 447                pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
 448                return;
 449        }
 450
 451        spin_lock(&ci->i_ceph_lock);
 452        used = __ceph_caps_used(ci);
 453        dirty = __ceph_caps_dirty(ci);
 454
 455        /*
 456         * If there is a write in progress, treat that as a dirty Fw,
 457         * even though it hasn't completed yet; by the time we finish
 458         * up this capsnap it will be.
 459         */
 460        if (used & CEPH_CAP_FILE_WR)
 461                dirty |= CEPH_CAP_FILE_WR;
 462
 463        if (__ceph_have_pending_cap_snap(ci)) {
 464                /* there is no point in queuing multiple "pending" cap_snaps,
 465                   as no new writes are allowed to start when pending, so any
 466                   writes in progress now were started before the previous
 467                   cap_snap.  lucky us. */
 468                dout("queue_cap_snap %p already pending\n", inode);
 469                kfree(capsnap);
 470        } else if (dirty & (CEPH_CAP_AUTH_EXCL|CEPH_CAP_XATTR_EXCL|
 471                            CEPH_CAP_FILE_EXCL|CEPH_CAP_FILE_WR)) {
 472                struct ceph_snap_context *snapc = ci->i_head_snapc;
 473
 474                /*
 475                 * if we are a sync write, we may need to go to the snaprealm
 476                 * to get the current snapc.
 477                 */
 478                if (!snapc)
 479                        snapc = ci->i_snap_realm->cached_context;
 480
 481                dout("queue_cap_snap %p cap_snap %p queuing under %p %s\n",
 482                     inode, capsnap, snapc, ceph_cap_string(dirty));
 483                ihold(inode);
 484
 485                atomic_set(&capsnap->nref, 1);
 486                capsnap->ci = ci;
 487                INIT_LIST_HEAD(&capsnap->ci_item);
 488                INIT_LIST_HEAD(&capsnap->flushing_item);
 489
 490                capsnap->follows = snapc->seq;
 491                capsnap->issued = __ceph_caps_issued(ci, NULL);
 492                capsnap->dirty = dirty;
 493
 494                capsnap->mode = inode->i_mode;
 495                capsnap->uid = inode->i_uid;
 496                capsnap->gid = inode->i_gid;
 497
 498                if (dirty & CEPH_CAP_XATTR_EXCL) {
 499                        __ceph_build_xattrs_blob(ci);
 500                        capsnap->xattr_blob =
 501                                ceph_buffer_get(ci->i_xattrs.blob);
 502                        capsnap->xattr_version = ci->i_xattrs.version;
 503                } else {
 504                        capsnap->xattr_blob = NULL;
 505                        capsnap->xattr_version = 0;
 506                }
 507
 508                /* dirty page count moved from _head to this cap_snap;
 509                   all subsequent writes page dirties occur _after_ this
 510                   snapshot. */
 511                capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
 512                ci->i_wrbuffer_ref_head = 0;
 513                capsnap->context = snapc;
 514                ci->i_head_snapc =
 515                        ceph_get_snap_context(ci->i_snap_realm->cached_context);
 516                dout(" new snapc is %p\n", ci->i_head_snapc);
 517                list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);
 518
 519                if (used & CEPH_CAP_FILE_WR) {
 520                        dout("queue_cap_snap %p cap_snap %p snapc %p"
 521                             " seq %llu used WR, now pending\n", inode,
 522                             capsnap, snapc, snapc->seq);
 523                        capsnap->writing = 1;
 524                } else {
 525                        /* note mtime, size NOW. */
 526                        __ceph_finish_cap_snap(ci, capsnap);
 527                }
 528        } else {
 529                dout("queue_cap_snap %p nothing dirty|writing\n", inode);
 530                kfree(capsnap);
 531        }
 532
 533        spin_unlock(&ci->i_ceph_lock);
 534}
 535
 536/*
 537 * Finalize the size, mtime for a cap_snap.. that is, settle on final values
 538 * to be used for the snapshot, to be flushed back to the mds.
 539 *
 540 * If capsnap can now be flushed, add to snap_flush list, and return 1.
 541 *
 542 * Caller must hold i_ceph_lock.
 543 */
 544int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
 545                            struct ceph_cap_snap *capsnap)
 546{
 547        struct inode *inode = &ci->vfs_inode;
 548        struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
 549
 550        BUG_ON(capsnap->writing);
 551        capsnap->size = inode->i_size;
 552        capsnap->mtime = inode->i_mtime;
 553        capsnap->atime = inode->i_atime;
 554        capsnap->ctime = inode->i_ctime;
 555        capsnap->time_warp_seq = ci->i_time_warp_seq;
 556        if (capsnap->dirty_pages) {
 557                dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu "
 558                     "still has %d dirty pages\n", inode, capsnap,
 559                     capsnap->context, capsnap->context->seq,
 560                     ceph_cap_string(capsnap->dirty), capsnap->size,
 561                     capsnap->dirty_pages);
 562                return 0;
 563        }
 564        dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu\n",
 565             inode, capsnap, capsnap->context,
 566             capsnap->context->seq, ceph_cap_string(capsnap->dirty),
 567             capsnap->size);
 568
 569        spin_lock(&mdsc->snap_flush_lock);
 570        list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
 571        spin_unlock(&mdsc->snap_flush_lock);
 572        return 1;  /* caller may want to ceph_flush_snaps */
 573}
 574
 575/*
 576 * Queue cap_snaps for snap writeback for this realm and its children.
 577 * Called under snap_rwsem, so realm topology won't change.
 578 */
 579static void queue_realm_cap_snaps(struct ceph_snap_realm *realm)
 580{
 581        struct ceph_inode_info *ci;
 582        struct inode *lastinode = NULL;
 583        struct ceph_snap_realm *child;
 584
 585        dout("queue_realm_cap_snaps %p %llx inodes\n", realm, realm->ino);
 586
 587        spin_lock(&realm->inodes_with_caps_lock);
 588        list_for_each_entry(ci, &realm->inodes_with_caps,
 589                            i_snap_realm_item) {
 590                struct inode *inode = igrab(&ci->vfs_inode);
 591                if (!inode)
 592                        continue;
 593                spin_unlock(&realm->inodes_with_caps_lock);
 594                if (lastinode)
 595                        iput(lastinode);
 596                lastinode = inode;
 597                ceph_queue_cap_snap(ci);
 598                spin_lock(&realm->inodes_with_caps_lock);
 599        }
 600        spin_unlock(&realm->inodes_with_caps_lock);
 601        if (lastinode)
 602                iput(lastinode);
 603
 604        list_for_each_entry(child, &realm->children, child_item) {
 605                dout("queue_realm_cap_snaps %p %llx queue child %p %llx\n",
 606                     realm, realm->ino, child, child->ino);
 607                list_del_init(&child->dirty_item);
 608                list_add(&child->dirty_item, &realm->dirty_item);
 609        }
 610
 611        list_del_init(&realm->dirty_item);
 612        dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino);
 613}
 614
 615/*
 616 * Parse and apply a snapblob "snap trace" from the MDS.  This specifies
 617 * the snap realm parameters from a given realm and all of its ancestors,
 618 * up to the root.
 619 *
 620 * Caller must hold snap_rwsem for write.
 621 */
 622int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
 623                           void *p, void *e, bool deletion)
 624{
 625        struct ceph_mds_snap_realm *ri;    /* encoded */
 626        __le64 *snaps;                     /* encoded */
 627        __le64 *prior_parent_snaps;        /* encoded */
 628        struct ceph_snap_realm *realm;
 629        int invalidate = 0;
 630        int err = -ENOMEM;
 631        LIST_HEAD(dirty_realms);
 632
 633        dout("update_snap_trace deletion=%d\n", deletion);
 634more:
 635        ceph_decode_need(&p, e, sizeof(*ri), bad);
 636        ri = p;
 637        p += sizeof(*ri);
 638        ceph_decode_need(&p, e, sizeof(u64)*(le32_to_cpu(ri->num_snaps) +
 639                            le32_to_cpu(ri->num_prior_parent_snaps)), bad);
 640        snaps = p;
 641        p += sizeof(u64) * le32_to_cpu(ri->num_snaps);
 642        prior_parent_snaps = p;
 643        p += sizeof(u64) * le32_to_cpu(ri->num_prior_parent_snaps);
 644
 645        realm = ceph_lookup_snap_realm(mdsc, le64_to_cpu(ri->ino));
 646        if (!realm) {
 647                realm = ceph_create_snap_realm(mdsc, le64_to_cpu(ri->ino));
 648                if (IS_ERR(realm)) {
 649                        err = PTR_ERR(realm);
 650                        goto fail;
 651                }
 652        }
 653
 654        /* ensure the parent is correct */
 655        err = adjust_snap_realm_parent(mdsc, realm, le64_to_cpu(ri->parent));
 656        if (err < 0)
 657                goto fail;
 658        invalidate += err;
 659
 660        if (le64_to_cpu(ri->seq) > realm->seq) {
 661                dout("update_snap_trace updating %llx %p %lld -> %lld\n",
 662                     realm->ino, realm, realm->seq, le64_to_cpu(ri->seq));
 663                /* update realm parameters, snap lists */
 664                realm->seq = le64_to_cpu(ri->seq);
 665                realm->created = le64_to_cpu(ri->created);
 666                realm->parent_since = le64_to_cpu(ri->parent_since);
 667
 668                realm->num_snaps = le32_to_cpu(ri->num_snaps);
 669                err = dup_array(&realm->snaps, snaps, realm->num_snaps);
 670                if (err < 0)
 671                        goto fail;
 672
 673                realm->num_prior_parent_snaps =
 674                        le32_to_cpu(ri->num_prior_parent_snaps);
 675                err = dup_array(&realm->prior_parent_snaps, prior_parent_snaps,
 676                                realm->num_prior_parent_snaps);
 677                if (err < 0)
 678                        goto fail;
 679
 680                /* queue realm for cap_snap creation */
 681                list_add(&realm->dirty_item, &dirty_realms);
 682
 683                invalidate = 1;
 684        } else if (!realm->cached_context) {
 685                dout("update_snap_trace %llx %p seq %lld new\n",
 686                     realm->ino, realm, realm->seq);
 687                invalidate = 1;
 688        } else {
 689                dout("update_snap_trace %llx %p seq %lld unchanged\n",
 690                     realm->ino, realm, realm->seq);
 691        }
 692
 693        dout("done with %llx %p, invalidated=%d, %p %p\n", realm->ino,
 694             realm, invalidate, p, e);
 695
 696        if (p < e)
 697                goto more;
 698
 699        /* invalidate when we reach the _end_ (root) of the trace */
 700        if (invalidate)
 701                rebuild_snap_realms(realm);
 702
 703        /*
 704         * queue cap snaps _after_ we've built the new snap contexts,
 705         * so that i_head_snapc can be set appropriately.
 706         */
 707        while (!list_empty(&dirty_realms)) {
 708                realm = list_first_entry(&dirty_realms, struct ceph_snap_realm,
 709                                         dirty_item);
 710                queue_realm_cap_snaps(realm);
 711        }
 712
 713        __cleanup_empty_realms(mdsc);
 714        return 0;
 715
 716bad:
 717        err = -EINVAL;
 718fail:
 719        pr_err("update_snap_trace error %d\n", err);
 720        return err;
 721}
 722
 723
 724/*
 725 * Send any cap_snaps that are queued for flush.  Try to carry
 726 * s_mutex across multiple snap flushes to avoid locking overhead.
 727 *
 728 * Caller holds no locks.
 729 */
 730static void flush_snaps(struct ceph_mds_client *mdsc)
 731{
 732        struct ceph_inode_info *ci;
 733        struct inode *inode;
 734        struct ceph_mds_session *session = NULL;
 735
 736        dout("flush_snaps\n");
 737        spin_lock(&mdsc->snap_flush_lock);
 738        while (!list_empty(&mdsc->snap_flush_list)) {
 739                ci = list_first_entry(&mdsc->snap_flush_list,
 740                                struct ceph_inode_info, i_snap_flush_item);
 741                inode = &ci->vfs_inode;
 742                ihold(inode);
 743                spin_unlock(&mdsc->snap_flush_lock);
 744                spin_lock(&ci->i_ceph_lock);
 745                __ceph_flush_snaps(ci, &session, 0);
 746                spin_unlock(&ci->i_ceph_lock);
 747                iput(inode);
 748                spin_lock(&mdsc->snap_flush_lock);
 749        }
 750        spin_unlock(&mdsc->snap_flush_lock);
 751
 752        if (session) {
 753                mutex_unlock(&session->s_mutex);
 754                ceph_put_mds_session(session);
 755        }
 756        dout("flush_snaps done\n");
 757}
 758
 759
 760/*
 761 * Handle a snap notification from the MDS.
 762 *
 763 * This can take two basic forms: the simplest is just a snap creation
 764 * or deletion notification on an existing realm.  This should update the
 765 * realm and its children.
 766 *
 767 * The more difficult case is realm creation, due to snap creation at a
 768 * new point in the file hierarchy, or due to a rename that moves a file or
 769 * directory into another realm.
 770 */
 771void ceph_handle_snap(struct ceph_mds_client *mdsc,
 772                      struct ceph_mds_session *session,
 773                      struct ceph_msg *msg)
 774{
 775        struct super_block *sb = mdsc->fsc->sb;
 776        int mds = session->s_mds;
 777        u64 split;
 778        int op;
 779        int trace_len;
 780        struct ceph_snap_realm *realm = NULL;
 781        void *p = msg->front.iov_base;
 782        void *e = p + msg->front.iov_len;
 783        struct ceph_mds_snap_head *h;
 784        int num_split_inos, num_split_realms;
 785        __le64 *split_inos = NULL, *split_realms = NULL;
 786        int i;
 787        int locked_rwsem = 0;
 788
 789        /* decode */
 790        if (msg->front.iov_len < sizeof(*h))
 791                goto bad;
 792        h = p;
 793        op = le32_to_cpu(h->op);
 794        split = le64_to_cpu(h->split);   /* non-zero if we are splitting an
 795                                          * existing realm */
 796        num_split_inos = le32_to_cpu(h->num_split_inos);
 797        num_split_realms = le32_to_cpu(h->num_split_realms);
 798        trace_len = le32_to_cpu(h->trace_len);
 799        p += sizeof(*h);
 800
 801        dout("handle_snap from mds%d op %s split %llx tracelen %d\n", mds,
 802             ceph_snap_op_name(op), split, trace_len);
 803
 804        mutex_lock(&session->s_mutex);
 805        session->s_seq++;
 806        mutex_unlock(&session->s_mutex);
 807
 808        down_write(&mdsc->snap_rwsem);
 809        locked_rwsem = 1;
 810
 811        if (op == CEPH_SNAP_OP_SPLIT) {
 812                struct ceph_mds_snap_realm *ri;
 813
 814                /*
 815                 * A "split" breaks part of an existing realm off into
 816                 * a new realm.  The MDS provides a list of inodes
 817                 * (with caps) and child realms that belong to the new
 818                 * child.
 819                 */
 820                split_inos = p;
 821                p += sizeof(u64) * num_split_inos;
 822                split_realms = p;
 823                p += sizeof(u64) * num_split_realms;
 824                ceph_decode_need(&p, e, sizeof(*ri), bad);
 825                /* we will peek at realm info here, but will _not_
 826                 * advance p, as the realm update will occur below in
 827                 * ceph_update_snap_trace. */
 828                ri = p;
 829
 830                realm = ceph_lookup_snap_realm(mdsc, split);
 831                if (!realm) {
 832                        realm = ceph_create_snap_realm(mdsc, split);
 833                        if (IS_ERR(realm))
 834                                goto out;
 835                }
 836                ceph_get_snap_realm(mdsc, realm);
 837
 838                dout("splitting snap_realm %llx %p\n", realm->ino, realm);
 839                for (i = 0; i < num_split_inos; i++) {
 840                        struct ceph_vino vino = {
 841                                .ino = le64_to_cpu(split_inos[i]),
 842                                .snap = CEPH_NOSNAP,
 843                        };
 844                        struct inode *inode = ceph_find_inode(sb, vino);
 845                        struct ceph_inode_info *ci;
 846                        struct ceph_snap_realm *oldrealm;
 847
 848                        if (!inode)
 849                                continue;
 850                        ci = ceph_inode(inode);
 851
 852                        spin_lock(&ci->i_ceph_lock);
 853                        if (!ci->i_snap_realm)
 854                                goto skip_inode;
 855                        /*
 856                         * If this inode belongs to a realm that was
 857                         * created after our new realm, we experienced
 858                         * a race (due to another split notifications
 859                         * arriving from a different MDS).  So skip
 860                         * this inode.
 861                         */
 862                        if (ci->i_snap_realm->created >
 863                            le64_to_cpu(ri->created)) {
 864                                dout(" leaving %p in newer realm %llx %p\n",
 865                                     inode, ci->i_snap_realm->ino,
 866                                     ci->i_snap_realm);
 867                                goto skip_inode;
 868                        }
 869                        dout(" will move %p to split realm %llx %p\n",
 870                             inode, realm->ino, realm);
 871                        /*
 872                         * Move the inode to the new realm
 873                         */
 874                        spin_lock(&realm->inodes_with_caps_lock);
 875                        list_del_init(&ci->i_snap_realm_item);
 876                        list_add(&ci->i_snap_realm_item,
 877                                 &realm->inodes_with_caps);
 878                        oldrealm = ci->i_snap_realm;
 879                        ci->i_snap_realm = realm;
 880                        spin_unlock(&realm->inodes_with_caps_lock);
 881                        spin_unlock(&ci->i_ceph_lock);
 882
 883                        ceph_get_snap_realm(mdsc, realm);
 884                        ceph_put_snap_realm(mdsc, oldrealm);
 885
 886                        iput(inode);
 887                        continue;
 888
 889skip_inode:
 890                        spin_unlock(&ci->i_ceph_lock);
 891                        iput(inode);
 892                }
 893
 894                /* we may have taken some of the old realm's children. */
 895                for (i = 0; i < num_split_realms; i++) {
 896                        struct ceph_snap_realm *child =
 897                                ceph_lookup_snap_realm(mdsc,
 898                                           le64_to_cpu(split_realms[i]));
 899                        if (!child)
 900                                continue;
 901                        adjust_snap_realm_parent(mdsc, child, realm->ino);
 902                }
 903        }
 904
 905        /*
 906         * update using the provided snap trace. if we are deleting a
 907         * snap, we can avoid queueing cap_snaps.
 908         */
 909        ceph_update_snap_trace(mdsc, p, e,
 910                               op == CEPH_SNAP_OP_DESTROY);
 911
 912        if (op == CEPH_SNAP_OP_SPLIT)
 913                /* we took a reference when we created the realm, above */
 914                ceph_put_snap_realm(mdsc, realm);
 915
 916        __cleanup_empty_realms(mdsc);
 917
 918        up_write(&mdsc->snap_rwsem);
 919
 920        flush_snaps(mdsc);
 921        return;
 922
 923bad:
 924        pr_err("corrupt snap message from mds%d\n", mds);
 925        ceph_msg_dump(msg);
 926out:
 927        if (locked_rwsem)
 928                up_write(&mdsc->snap_rwsem);
 929        return;
 930}
 931
 932
 933
 934
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