linux/fs/xfs/xfs_buf.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
   4 * All Rights Reserved.
   5 */
   6#include "xfs.h"
   7#include <linux/backing-dev.h>
   8
   9#include "xfs_shared.h"
  10#include "xfs_format.h"
  11#include "xfs_log_format.h"
  12#include "xfs_trans_resv.h"
  13#include "xfs_mount.h"
  14#include "xfs_trace.h"
  15#include "xfs_log.h"
  16#include "xfs_log_recover.h"
  17#include "xfs_trans.h"
  18#include "xfs_buf_item.h"
  19#include "xfs_errortag.h"
  20#include "xfs_error.h"
  21#include "xfs_ag.h"
  22
  23static struct kmem_cache *xfs_buf_cache;
  24
  25/*
  26 * Locking orders
  27 *
  28 * xfs_buf_ioacct_inc:
  29 * xfs_buf_ioacct_dec:
  30 *      b_sema (caller holds)
  31 *        b_lock
  32 *
  33 * xfs_buf_stale:
  34 *      b_sema (caller holds)
  35 *        b_lock
  36 *          lru_lock
  37 *
  38 * xfs_buf_rele:
  39 *      b_lock
  40 *        pag_buf_lock
  41 *          lru_lock
  42 *
  43 * xfs_buftarg_drain_rele
  44 *      lru_lock
  45 *        b_lock (trylock due to inversion)
  46 *
  47 * xfs_buftarg_isolate
  48 *      lru_lock
  49 *        b_lock (trylock due to inversion)
  50 */
  51
  52static int __xfs_buf_submit(struct xfs_buf *bp, bool wait);
  53
  54static inline int
  55xfs_buf_submit(
  56        struct xfs_buf          *bp)
  57{
  58        return __xfs_buf_submit(bp, !(bp->b_flags & XBF_ASYNC));
  59}
  60
  61static inline int
  62xfs_buf_is_vmapped(
  63        struct xfs_buf  *bp)
  64{
  65        /*
  66         * Return true if the buffer is vmapped.
  67         *
  68         * b_addr is null if the buffer is not mapped, but the code is clever
  69         * enough to know it doesn't have to map a single page, so the check has
  70         * to be both for b_addr and bp->b_page_count > 1.
  71         */
  72        return bp->b_addr && bp->b_page_count > 1;
  73}
  74
  75static inline int
  76xfs_buf_vmap_len(
  77        struct xfs_buf  *bp)
  78{
  79        return (bp->b_page_count * PAGE_SIZE);
  80}
  81
  82/*
  83 * Bump the I/O in flight count on the buftarg if we haven't yet done so for
  84 * this buffer. The count is incremented once per buffer (per hold cycle)
  85 * because the corresponding decrement is deferred to buffer release. Buffers
  86 * can undergo I/O multiple times in a hold-release cycle and per buffer I/O
  87 * tracking adds unnecessary overhead. This is used for sychronization purposes
  88 * with unmount (see xfs_buftarg_drain()), so all we really need is a count of
  89 * in-flight buffers.
  90 *
  91 * Buffers that are never released (e.g., superblock, iclog buffers) must set
  92 * the XBF_NO_IOACCT flag before I/O submission. Otherwise, the buftarg count
  93 * never reaches zero and unmount hangs indefinitely.
  94 */
  95static inline void
  96xfs_buf_ioacct_inc(
  97        struct xfs_buf  *bp)
  98{
  99        if (bp->b_flags & XBF_NO_IOACCT)
 100                return;
 101
 102        ASSERT(bp->b_flags & XBF_ASYNC);
 103        spin_lock(&bp->b_lock);
 104        if (!(bp->b_state & XFS_BSTATE_IN_FLIGHT)) {
 105                bp->b_state |= XFS_BSTATE_IN_FLIGHT;
 106                percpu_counter_inc(&bp->b_target->bt_io_count);
 107        }
 108        spin_unlock(&bp->b_lock);
 109}
 110
 111/*
 112 * Clear the in-flight state on a buffer about to be released to the LRU or
 113 * freed and unaccount from the buftarg.
 114 */
 115static inline void
 116__xfs_buf_ioacct_dec(
 117        struct xfs_buf  *bp)
 118{
 119        lockdep_assert_held(&bp->b_lock);
 120
 121        if (bp->b_state & XFS_BSTATE_IN_FLIGHT) {
 122                bp->b_state &= ~XFS_BSTATE_IN_FLIGHT;
 123                percpu_counter_dec(&bp->b_target->bt_io_count);
 124        }
 125}
 126
 127static inline void
 128xfs_buf_ioacct_dec(
 129        struct xfs_buf  *bp)
 130{
 131        spin_lock(&bp->b_lock);
 132        __xfs_buf_ioacct_dec(bp);
 133        spin_unlock(&bp->b_lock);
 134}
 135
 136/*
 137 * When we mark a buffer stale, we remove the buffer from the LRU and clear the
 138 * b_lru_ref count so that the buffer is freed immediately when the buffer
 139 * reference count falls to zero. If the buffer is already on the LRU, we need
 140 * to remove the reference that LRU holds on the buffer.
 141 *
 142 * This prevents build-up of stale buffers on the LRU.
 143 */
 144void
 145xfs_buf_stale(
 146        struct xfs_buf  *bp)
 147{
 148        ASSERT(xfs_buf_islocked(bp));
 149
 150        bp->b_flags |= XBF_STALE;
 151
 152        /*
 153         * Clear the delwri status so that a delwri queue walker will not
 154         * flush this buffer to disk now that it is stale. The delwri queue has
 155         * a reference to the buffer, so this is safe to do.
 156         */
 157        bp->b_flags &= ~_XBF_DELWRI_Q;
 158
 159        /*
 160         * Once the buffer is marked stale and unlocked, a subsequent lookup
 161         * could reset b_flags. There is no guarantee that the buffer is
 162         * unaccounted (released to LRU) before that occurs. Drop in-flight
 163         * status now to preserve accounting consistency.
 164         */
 165        spin_lock(&bp->b_lock);
 166        __xfs_buf_ioacct_dec(bp);
 167
 168        atomic_set(&bp->b_lru_ref, 0);
 169        if (!(bp->b_state & XFS_BSTATE_DISPOSE) &&
 170            (list_lru_del(&bp->b_target->bt_lru, &bp->b_lru)))
 171                atomic_dec(&bp->b_hold);
 172
 173        ASSERT(atomic_read(&bp->b_hold) >= 1);
 174        spin_unlock(&bp->b_lock);
 175}
 176
 177static int
 178xfs_buf_get_maps(
 179        struct xfs_buf          *bp,
 180        int                     map_count)
 181{
 182        ASSERT(bp->b_maps == NULL);
 183        bp->b_map_count = map_count;
 184
 185        if (map_count == 1) {
 186                bp->b_maps = &bp->__b_map;
 187                return 0;
 188        }
 189
 190        bp->b_maps = kmem_zalloc(map_count * sizeof(struct xfs_buf_map),
 191                                KM_NOFS);
 192        if (!bp->b_maps)
 193                return -ENOMEM;
 194        return 0;
 195}
 196
 197/*
 198 *      Frees b_pages if it was allocated.
 199 */
 200static void
 201xfs_buf_free_maps(
 202        struct xfs_buf  *bp)
 203{
 204        if (bp->b_maps != &bp->__b_map) {
 205                kmem_free(bp->b_maps);
 206                bp->b_maps = NULL;
 207        }
 208}
 209
 210static int
 211_xfs_buf_alloc(
 212        struct xfs_buftarg      *target,
 213        struct xfs_buf_map      *map,
 214        int                     nmaps,
 215        xfs_buf_flags_t         flags,
 216        struct xfs_buf          **bpp)
 217{
 218        struct xfs_buf          *bp;
 219        int                     error;
 220        int                     i;
 221
 222        *bpp = NULL;
 223        bp = kmem_cache_zalloc(xfs_buf_cache, GFP_NOFS | __GFP_NOFAIL);
 224
 225        /*
 226         * We don't want certain flags to appear in b_flags unless they are
 227         * specifically set by later operations on the buffer.
 228         */
 229        flags &= ~(XBF_UNMAPPED | XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD);
 230
 231        atomic_set(&bp->b_hold, 1);
 232        atomic_set(&bp->b_lru_ref, 1);
 233        init_completion(&bp->b_iowait);
 234        INIT_LIST_HEAD(&bp->b_lru);
 235        INIT_LIST_HEAD(&bp->b_list);
 236        INIT_LIST_HEAD(&bp->b_li_list);
 237        sema_init(&bp->b_sema, 0); /* held, no waiters */
 238        spin_lock_init(&bp->b_lock);
 239        bp->b_target = target;
 240        bp->b_mount = target->bt_mount;
 241        bp->b_flags = flags;
 242
 243        /*
 244         * Set length and io_length to the same value initially.
 245         * I/O routines should use io_length, which will be the same in
 246         * most cases but may be reset (e.g. XFS recovery).
 247         */
 248        error = xfs_buf_get_maps(bp, nmaps);
 249        if (error)  {
 250                kmem_cache_free(xfs_buf_cache, bp);
 251                return error;
 252        }
 253
 254        bp->b_rhash_key = map[0].bm_bn;
 255        bp->b_length = 0;
 256        for (i = 0; i < nmaps; i++) {
 257                bp->b_maps[i].bm_bn = map[i].bm_bn;
 258                bp->b_maps[i].bm_len = map[i].bm_len;
 259                bp->b_length += map[i].bm_len;
 260        }
 261
 262        atomic_set(&bp->b_pin_count, 0);
 263        init_waitqueue_head(&bp->b_waiters);
 264
 265        XFS_STATS_INC(bp->b_mount, xb_create);
 266        trace_xfs_buf_init(bp, _RET_IP_);
 267
 268        *bpp = bp;
 269        return 0;
 270}
 271
 272static void
 273xfs_buf_free_pages(
 274        struct xfs_buf  *bp)
 275{
 276        uint            i;
 277
 278        ASSERT(bp->b_flags & _XBF_PAGES);
 279
 280        if (xfs_buf_is_vmapped(bp))
 281                vm_unmap_ram(bp->b_addr, bp->b_page_count);
 282
 283        for (i = 0; i < bp->b_page_count; i++) {
 284                if (bp->b_pages[i])
 285                        __free_page(bp->b_pages[i]);
 286        }
 287        if (current->reclaim_state)
 288                current->reclaim_state->reclaimed_slab += bp->b_page_count;
 289
 290        if (bp->b_pages != bp->b_page_array)
 291                kmem_free(bp->b_pages);
 292        bp->b_pages = NULL;
 293        bp->b_flags &= ~_XBF_PAGES;
 294}
 295
 296static void
 297xfs_buf_free(
 298        struct xfs_buf          *bp)
 299{
 300        trace_xfs_buf_free(bp, _RET_IP_);
 301
 302        ASSERT(list_empty(&bp->b_lru));
 303
 304        if (bp->b_flags & _XBF_PAGES)
 305                xfs_buf_free_pages(bp);
 306        else if (bp->b_flags & _XBF_KMEM)
 307                kmem_free(bp->b_addr);
 308
 309        xfs_buf_free_maps(bp);
 310        kmem_cache_free(xfs_buf_cache, bp);
 311}
 312
 313static int
 314xfs_buf_alloc_kmem(
 315        struct xfs_buf  *bp,
 316        xfs_buf_flags_t flags)
 317{
 318        xfs_km_flags_t  kmflag_mask = KM_NOFS;
 319        size_t          size = BBTOB(bp->b_length);
 320
 321        /* Assure zeroed buffer for non-read cases. */
 322        if (!(flags & XBF_READ))
 323                kmflag_mask |= KM_ZERO;
 324
 325        bp->b_addr = kmem_alloc(size, kmflag_mask);
 326        if (!bp->b_addr)
 327                return -ENOMEM;
 328
 329        if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
 330            ((unsigned long)bp->b_addr & PAGE_MASK)) {
 331                /* b_addr spans two pages - use alloc_page instead */
 332                kmem_free(bp->b_addr);
 333                bp->b_addr = NULL;
 334                return -ENOMEM;
 335        }
 336        bp->b_offset = offset_in_page(bp->b_addr);
 337        bp->b_pages = bp->b_page_array;
 338        bp->b_pages[0] = kmem_to_page(bp->b_addr);
 339        bp->b_page_count = 1;
 340        bp->b_flags |= _XBF_KMEM;
 341        return 0;
 342}
 343
 344static int
 345xfs_buf_alloc_pages(
 346        struct xfs_buf  *bp,
 347        xfs_buf_flags_t flags)
 348{
 349        gfp_t           gfp_mask = __GFP_NOWARN;
 350        long            filled = 0;
 351
 352        if (flags & XBF_READ_AHEAD)
 353                gfp_mask |= __GFP_NORETRY;
 354        else
 355                gfp_mask |= GFP_NOFS;
 356
 357        /* Make sure that we have a page list */
 358        bp->b_page_count = DIV_ROUND_UP(BBTOB(bp->b_length), PAGE_SIZE);
 359        if (bp->b_page_count <= XB_PAGES) {
 360                bp->b_pages = bp->b_page_array;
 361        } else {
 362                bp->b_pages = kzalloc(sizeof(struct page *) * bp->b_page_count,
 363                                        gfp_mask);
 364                if (!bp->b_pages)
 365                        return -ENOMEM;
 366        }
 367        bp->b_flags |= _XBF_PAGES;
 368
 369        /* Assure zeroed buffer for non-read cases. */
 370        if (!(flags & XBF_READ))
 371                gfp_mask |= __GFP_ZERO;
 372
 373        /*
 374         * Bulk filling of pages can take multiple calls. Not filling the entire
 375         * array is not an allocation failure, so don't back off if we get at
 376         * least one extra page.
 377         */
 378        for (;;) {
 379                long    last = filled;
 380
 381                filled = alloc_pages_bulk_array(gfp_mask, bp->b_page_count,
 382                                                bp->b_pages);
 383                if (filled == bp->b_page_count) {
 384                        XFS_STATS_INC(bp->b_mount, xb_page_found);
 385                        break;
 386                }
 387
 388                if (filled != last)
 389                        continue;
 390
 391                if (flags & XBF_READ_AHEAD) {
 392                        xfs_buf_free_pages(bp);
 393                        return -ENOMEM;
 394                }
 395
 396                XFS_STATS_INC(bp->b_mount, xb_page_retries);
 397                congestion_wait(BLK_RW_ASYNC, HZ / 50);
 398        }
 399        return 0;
 400}
 401
 402/*
 403 *      Map buffer into kernel address-space if necessary.
 404 */
 405STATIC int
 406_xfs_buf_map_pages(
 407        struct xfs_buf          *bp,
 408        uint                    flags)
 409{
 410        ASSERT(bp->b_flags & _XBF_PAGES);
 411        if (bp->b_page_count == 1) {
 412                /* A single page buffer is always mappable */
 413                bp->b_addr = page_address(bp->b_pages[0]);
 414        } else if (flags & XBF_UNMAPPED) {
 415                bp->b_addr = NULL;
 416        } else {
 417                int retried = 0;
 418                unsigned nofs_flag;
 419
 420                /*
 421                 * vm_map_ram() will allocate auxiliary structures (e.g.
 422                 * pagetables) with GFP_KERNEL, yet we are likely to be under
 423                 * GFP_NOFS context here. Hence we need to tell memory reclaim
 424                 * that we are in such a context via PF_MEMALLOC_NOFS to prevent
 425                 * memory reclaim re-entering the filesystem here and
 426                 * potentially deadlocking.
 427                 */
 428                nofs_flag = memalloc_nofs_save();
 429                do {
 430                        bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
 431                                                -1);
 432                        if (bp->b_addr)
 433                                break;
 434                        vm_unmap_aliases();
 435                } while (retried++ <= 1);
 436                memalloc_nofs_restore(nofs_flag);
 437
 438                if (!bp->b_addr)
 439                        return -ENOMEM;
 440        }
 441
 442        return 0;
 443}
 444
 445/*
 446 *      Finding and Reading Buffers
 447 */
 448static int
 449_xfs_buf_obj_cmp(
 450        struct rhashtable_compare_arg   *arg,
 451        const void                      *obj)
 452{
 453        const struct xfs_buf_map        *map = arg->key;
 454        const struct xfs_buf            *bp = obj;
 455
 456        /*
 457         * The key hashing in the lookup path depends on the key being the
 458         * first element of the compare_arg, make sure to assert this.
 459         */
 460        BUILD_BUG_ON(offsetof(struct xfs_buf_map, bm_bn) != 0);
 461
 462        if (bp->b_rhash_key != map->bm_bn)
 463                return 1;
 464
 465        if (unlikely(bp->b_length != map->bm_len)) {
 466                /*
 467                 * found a block number match. If the range doesn't
 468                 * match, the only way this is allowed is if the buffer
 469                 * in the cache is stale and the transaction that made
 470                 * it stale has not yet committed. i.e. we are
 471                 * reallocating a busy extent. Skip this buffer and
 472                 * continue searching for an exact match.
 473                 */
 474                ASSERT(bp->b_flags & XBF_STALE);
 475                return 1;
 476        }
 477        return 0;
 478}
 479
 480static const struct rhashtable_params xfs_buf_hash_params = {
 481        .min_size               = 32,   /* empty AGs have minimal footprint */
 482        .nelem_hint             = 16,
 483        .key_len                = sizeof(xfs_daddr_t),
 484        .key_offset             = offsetof(struct xfs_buf, b_rhash_key),
 485        .head_offset            = offsetof(struct xfs_buf, b_rhash_head),
 486        .automatic_shrinking    = true,
 487        .obj_cmpfn              = _xfs_buf_obj_cmp,
 488};
 489
 490int
 491xfs_buf_hash_init(
 492        struct xfs_perag        *pag)
 493{
 494        spin_lock_init(&pag->pag_buf_lock);
 495        return rhashtable_init(&pag->pag_buf_hash, &xfs_buf_hash_params);
 496}
 497
 498void
 499xfs_buf_hash_destroy(
 500        struct xfs_perag        *pag)
 501{
 502        rhashtable_destroy(&pag->pag_buf_hash);
 503}
 504
 505/*
 506 * Look up a buffer in the buffer cache and return it referenced and locked
 507 * in @found_bp.
 508 *
 509 * If @new_bp is supplied and we have a lookup miss, insert @new_bp into the
 510 * cache.
 511 *
 512 * If XBF_TRYLOCK is set in @flags, only try to lock the buffer and return
 513 * -EAGAIN if we fail to lock it.
 514 *
 515 * Return values are:
 516 *      -EFSCORRUPTED if have been supplied with an invalid address
 517 *      -EAGAIN on trylock failure
 518 *      -ENOENT if we fail to find a match and @new_bp was NULL
 519 *      0, with @found_bp:
 520 *              - @new_bp if we inserted it into the cache
 521 *              - the buffer we found and locked.
 522 */
 523static int
 524xfs_buf_find(
 525        struct xfs_buftarg      *btp,
 526        struct xfs_buf_map      *map,
 527        int                     nmaps,
 528        xfs_buf_flags_t         flags,
 529        struct xfs_buf          *new_bp,
 530        struct xfs_buf          **found_bp)
 531{
 532        struct xfs_perag        *pag;
 533        struct xfs_buf          *bp;
 534        struct xfs_buf_map      cmap = { .bm_bn = map[0].bm_bn };
 535        xfs_daddr_t             eofs;
 536        int                     i;
 537
 538        *found_bp = NULL;
 539
 540        for (i = 0; i < nmaps; i++)
 541                cmap.bm_len += map[i].bm_len;
 542
 543        /* Check for IOs smaller than the sector size / not sector aligned */
 544        ASSERT(!(BBTOB(cmap.bm_len) < btp->bt_meta_sectorsize));
 545        ASSERT(!(BBTOB(cmap.bm_bn) & (xfs_off_t)btp->bt_meta_sectormask));
 546
 547        /*
 548         * Corrupted block numbers can get through to here, unfortunately, so we
 549         * have to check that the buffer falls within the filesystem bounds.
 550         */
 551        eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
 552        if (cmap.bm_bn < 0 || cmap.bm_bn >= eofs) {
 553                xfs_alert(btp->bt_mount,
 554                          "%s: daddr 0x%llx out of range, EOFS 0x%llx",
 555                          __func__, cmap.bm_bn, eofs);
 556                WARN_ON(1);
 557                return -EFSCORRUPTED;
 558        }
 559
 560        pag = xfs_perag_get(btp->bt_mount,
 561                            xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
 562
 563        spin_lock(&pag->pag_buf_lock);
 564        bp = rhashtable_lookup_fast(&pag->pag_buf_hash, &cmap,
 565                                    xfs_buf_hash_params);
 566        if (bp) {
 567                atomic_inc(&bp->b_hold);
 568                goto found;
 569        }
 570
 571        /* No match found */
 572        if (!new_bp) {
 573                XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
 574                spin_unlock(&pag->pag_buf_lock);
 575                xfs_perag_put(pag);
 576                return -ENOENT;
 577        }
 578
 579        /* the buffer keeps the perag reference until it is freed */
 580        new_bp->b_pag = pag;
 581        rhashtable_insert_fast(&pag->pag_buf_hash, &new_bp->b_rhash_head,
 582                               xfs_buf_hash_params);
 583        spin_unlock(&pag->pag_buf_lock);
 584        *found_bp = new_bp;
 585        return 0;
 586
 587found:
 588        spin_unlock(&pag->pag_buf_lock);
 589        xfs_perag_put(pag);
 590
 591        if (!xfs_buf_trylock(bp)) {
 592                if (flags & XBF_TRYLOCK) {
 593                        xfs_buf_rele(bp);
 594                        XFS_STATS_INC(btp->bt_mount, xb_busy_locked);
 595                        return -EAGAIN;
 596                }
 597                xfs_buf_lock(bp);
 598                XFS_STATS_INC(btp->bt_mount, xb_get_locked_waited);
 599        }
 600
 601        /*
 602         * if the buffer is stale, clear all the external state associated with
 603         * it. We need to keep flags such as how we allocated the buffer memory
 604         * intact here.
 605         */
 606        if (bp->b_flags & XBF_STALE) {
 607                ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
 608                bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
 609                bp->b_ops = NULL;
 610        }
 611
 612        trace_xfs_buf_find(bp, flags, _RET_IP_);
 613        XFS_STATS_INC(btp->bt_mount, xb_get_locked);
 614        *found_bp = bp;
 615        return 0;
 616}
 617
 618struct xfs_buf *
 619xfs_buf_incore(
 620        struct xfs_buftarg      *target,
 621        xfs_daddr_t             blkno,
 622        size_t                  numblks,
 623        xfs_buf_flags_t         flags)
 624{
 625        struct xfs_buf          *bp;
 626        int                     error;
 627        DEFINE_SINGLE_BUF_MAP(map, blkno, numblks);
 628
 629        error = xfs_buf_find(target, &map, 1, flags, NULL, &bp);
 630        if (error)
 631                return NULL;
 632        return bp;
 633}
 634
 635/*
 636 * Assembles a buffer covering the specified range. The code is optimised for
 637 * cache hits, as metadata intensive workloads will see 3 orders of magnitude
 638 * more hits than misses.
 639 */
 640int
 641xfs_buf_get_map(
 642        struct xfs_buftarg      *target,
 643        struct xfs_buf_map      *map,
 644        int                     nmaps,
 645        xfs_buf_flags_t         flags,
 646        struct xfs_buf          **bpp)
 647{
 648        struct xfs_buf          *bp;
 649        struct xfs_buf          *new_bp;
 650        int                     error;
 651
 652        *bpp = NULL;
 653        error = xfs_buf_find(target, map, nmaps, flags, NULL, &bp);
 654        if (!error)
 655                goto found;
 656        if (error != -ENOENT)
 657                return error;
 658
 659        error = _xfs_buf_alloc(target, map, nmaps, flags, &new_bp);
 660        if (error)
 661                return error;
 662
 663        /*
 664         * For buffers that fit entirely within a single page, first attempt to
 665         * allocate the memory from the heap to minimise memory usage. If we
 666         * can't get heap memory for these small buffers, we fall back to using
 667         * the page allocator.
 668         */
 669        if (BBTOB(new_bp->b_length) >= PAGE_SIZE ||
 670            xfs_buf_alloc_kmem(new_bp, flags) < 0) {
 671                error = xfs_buf_alloc_pages(new_bp, flags);
 672                if (error)
 673                        goto out_free_buf;
 674        }
 675
 676        error = xfs_buf_find(target, map, nmaps, flags, new_bp, &bp);
 677        if (error)
 678                goto out_free_buf;
 679
 680        if (bp != new_bp)
 681                xfs_buf_free(new_bp);
 682
 683found:
 684        if (!bp->b_addr) {
 685                error = _xfs_buf_map_pages(bp, flags);
 686                if (unlikely(error)) {
 687                        xfs_warn_ratelimited(target->bt_mount,
 688                                "%s: failed to map %u pages", __func__,
 689                                bp->b_page_count);
 690                        xfs_buf_relse(bp);
 691                        return error;
 692                }
 693        }
 694
 695        /*
 696         * Clear b_error if this is a lookup from a caller that doesn't expect
 697         * valid data to be found in the buffer.
 698         */
 699        if (!(flags & XBF_READ))
 700                xfs_buf_ioerror(bp, 0);
 701
 702        XFS_STATS_INC(target->bt_mount, xb_get);
 703        trace_xfs_buf_get(bp, flags, _RET_IP_);
 704        *bpp = bp;
 705        return 0;
 706out_free_buf:
 707        xfs_buf_free(new_bp);
 708        return error;
 709}
 710
 711int
 712_xfs_buf_read(
 713        struct xfs_buf          *bp,
 714        xfs_buf_flags_t         flags)
 715{
 716        ASSERT(!(flags & XBF_WRITE));
 717        ASSERT(bp->b_maps[0].bm_bn != XFS_BUF_DADDR_NULL);
 718
 719        bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD | XBF_DONE);
 720        bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
 721
 722        return xfs_buf_submit(bp);
 723}
 724
 725/*
 726 * Reverify a buffer found in cache without an attached ->b_ops.
 727 *
 728 * If the caller passed an ops structure and the buffer doesn't have ops
 729 * assigned, set the ops and use it to verify the contents. If verification
 730 * fails, clear XBF_DONE. We assume the buffer has no recorded errors and is
 731 * already in XBF_DONE state on entry.
 732 *
 733 * Under normal operations, every in-core buffer is verified on read I/O
 734 * completion. There are two scenarios that can lead to in-core buffers without
 735 * an assigned ->b_ops. The first is during log recovery of buffers on a V4
 736 * filesystem, though these buffers are purged at the end of recovery. The
 737 * other is online repair, which intentionally reads with a NULL buffer ops to
 738 * run several verifiers across an in-core buffer in order to establish buffer
 739 * type.  If repair can't establish that, the buffer will be left in memory
 740 * with NULL buffer ops.
 741 */
 742int
 743xfs_buf_reverify(
 744        struct xfs_buf          *bp,
 745        const struct xfs_buf_ops *ops)
 746{
 747        ASSERT(bp->b_flags & XBF_DONE);
 748        ASSERT(bp->b_error == 0);
 749
 750        if (!ops || bp->b_ops)
 751                return 0;
 752
 753        bp->b_ops = ops;
 754        bp->b_ops->verify_read(bp);
 755        if (bp->b_error)
 756                bp->b_flags &= ~XBF_DONE;
 757        return bp->b_error;
 758}
 759
 760int
 761xfs_buf_read_map(
 762        struct xfs_buftarg      *target,
 763        struct xfs_buf_map      *map,
 764        int                     nmaps,
 765        xfs_buf_flags_t         flags,
 766        struct xfs_buf          **bpp,
 767        const struct xfs_buf_ops *ops,
 768        xfs_failaddr_t          fa)
 769{
 770        struct xfs_buf          *bp;
 771        int                     error;
 772
 773        flags |= XBF_READ;
 774        *bpp = NULL;
 775
 776        error = xfs_buf_get_map(target, map, nmaps, flags, &bp);
 777        if (error)
 778                return error;
 779
 780        trace_xfs_buf_read(bp, flags, _RET_IP_);
 781
 782        if (!(bp->b_flags & XBF_DONE)) {
 783                /* Initiate the buffer read and wait. */
 784                XFS_STATS_INC(target->bt_mount, xb_get_read);
 785                bp->b_ops = ops;
 786                error = _xfs_buf_read(bp, flags);
 787
 788                /* Readahead iodone already dropped the buffer, so exit. */
 789                if (flags & XBF_ASYNC)
 790                        return 0;
 791        } else {
 792                /* Buffer already read; all we need to do is check it. */
 793                error = xfs_buf_reverify(bp, ops);
 794
 795                /* Readahead already finished; drop the buffer and exit. */
 796                if (flags & XBF_ASYNC) {
 797                        xfs_buf_relse(bp);
 798                        return 0;
 799                }
 800
 801                /* We do not want read in the flags */
 802                bp->b_flags &= ~XBF_READ;
 803                ASSERT(bp->b_ops != NULL || ops == NULL);
 804        }
 805
 806        /*
 807         * If we've had a read error, then the contents of the buffer are
 808         * invalid and should not be used. To ensure that a followup read tries
 809         * to pull the buffer from disk again, we clear the XBF_DONE flag and
 810         * mark the buffer stale. This ensures that anyone who has a current
 811         * reference to the buffer will interpret it's contents correctly and
 812         * future cache lookups will also treat it as an empty, uninitialised
 813         * buffer.
 814         */
 815        if (error) {
 816                if (!xfs_is_shutdown(target->bt_mount))
 817                        xfs_buf_ioerror_alert(bp, fa);
 818
 819                bp->b_flags &= ~XBF_DONE;
 820                xfs_buf_stale(bp);
 821                xfs_buf_relse(bp);
 822
 823                /* bad CRC means corrupted metadata */
 824                if (error == -EFSBADCRC)
 825                        error = -EFSCORRUPTED;
 826                return error;
 827        }
 828
 829        *bpp = bp;
 830        return 0;
 831}
 832
 833/*
 834 *      If we are not low on memory then do the readahead in a deadlock
 835 *      safe manner.
 836 */
 837void
 838xfs_buf_readahead_map(
 839        struct xfs_buftarg      *target,
 840        struct xfs_buf_map      *map,
 841        int                     nmaps,
 842        const struct xfs_buf_ops *ops)
 843{
 844        struct xfs_buf          *bp;
 845
 846        if (bdi_read_congested(target->bt_bdev->bd_disk->bdi))
 847                return;
 848
 849        xfs_buf_read_map(target, map, nmaps,
 850                     XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD, &bp, ops,
 851                     __this_address);
 852}
 853
 854/*
 855 * Read an uncached buffer from disk. Allocates and returns a locked
 856 * buffer containing the disk contents or nothing. Uncached buffers always have
 857 * a cache index of XFS_BUF_DADDR_NULL so we can easily determine if the buffer
 858 * is cached or uncached during fault diagnosis.
 859 */
 860int
 861xfs_buf_read_uncached(
 862        struct xfs_buftarg      *target,
 863        xfs_daddr_t             daddr,
 864        size_t                  numblks,
 865        int                     flags,
 866        struct xfs_buf          **bpp,
 867        const struct xfs_buf_ops *ops)
 868{
 869        struct xfs_buf          *bp;
 870        int                     error;
 871
 872        *bpp = NULL;
 873
 874        error = xfs_buf_get_uncached(target, numblks, flags, &bp);
 875        if (error)
 876                return error;
 877
 878        /* set up the buffer for a read IO */
 879        ASSERT(bp->b_map_count == 1);
 880        bp->b_rhash_key = XFS_BUF_DADDR_NULL;
 881        bp->b_maps[0].bm_bn = daddr;
 882        bp->b_flags |= XBF_READ;
 883        bp->b_ops = ops;
 884
 885        xfs_buf_submit(bp);
 886        if (bp->b_error) {
 887                error = bp->b_error;
 888                xfs_buf_relse(bp);
 889                return error;
 890        }
 891
 892        *bpp = bp;
 893        return 0;
 894}
 895
 896int
 897xfs_buf_get_uncached(
 898        struct xfs_buftarg      *target,
 899        size_t                  numblks,
 900        int                     flags,
 901        struct xfs_buf          **bpp)
 902{
 903        int                     error;
 904        struct xfs_buf          *bp;
 905        DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
 906
 907        *bpp = NULL;
 908
 909        /* flags might contain irrelevant bits, pass only what we care about */
 910        error = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT, &bp);
 911        if (error)
 912                return error;
 913
 914        error = xfs_buf_alloc_pages(bp, flags);
 915        if (error)
 916                goto fail_free_buf;
 917
 918        error = _xfs_buf_map_pages(bp, 0);
 919        if (unlikely(error)) {
 920                xfs_warn(target->bt_mount,
 921                        "%s: failed to map pages", __func__);
 922                goto fail_free_buf;
 923        }
 924
 925        trace_xfs_buf_get_uncached(bp, _RET_IP_);
 926        *bpp = bp;
 927        return 0;
 928
 929fail_free_buf:
 930        xfs_buf_free(bp);
 931        return error;
 932}
 933
 934/*
 935 *      Increment reference count on buffer, to hold the buffer concurrently
 936 *      with another thread which may release (free) the buffer asynchronously.
 937 *      Must hold the buffer already to call this function.
 938 */
 939void
 940xfs_buf_hold(
 941        struct xfs_buf          *bp)
 942{
 943        trace_xfs_buf_hold(bp, _RET_IP_);
 944        atomic_inc(&bp->b_hold);
 945}
 946
 947/*
 948 * Release a hold on the specified buffer. If the hold count is 1, the buffer is
 949 * placed on LRU or freed (depending on b_lru_ref).
 950 */
 951void
 952xfs_buf_rele(
 953        struct xfs_buf          *bp)
 954{
 955        struct xfs_perag        *pag = bp->b_pag;
 956        bool                    release;
 957        bool                    freebuf = false;
 958
 959        trace_xfs_buf_rele(bp, _RET_IP_);
 960
 961        if (!pag) {
 962                ASSERT(list_empty(&bp->b_lru));
 963                if (atomic_dec_and_test(&bp->b_hold)) {
 964                        xfs_buf_ioacct_dec(bp);
 965                        xfs_buf_free(bp);
 966                }
 967                return;
 968        }
 969
 970        ASSERT(atomic_read(&bp->b_hold) > 0);
 971
 972        /*
 973         * We grab the b_lock here first to serialise racing xfs_buf_rele()
 974         * calls. The pag_buf_lock being taken on the last reference only
 975         * serialises against racing lookups in xfs_buf_find(). IOWs, the second
 976         * to last reference we drop here is not serialised against the last
 977         * reference until we take bp->b_lock. Hence if we don't grab b_lock
 978         * first, the last "release" reference can win the race to the lock and
 979         * free the buffer before the second-to-last reference is processed,
 980         * leading to a use-after-free scenario.
 981         */
 982        spin_lock(&bp->b_lock);
 983        release = atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock);
 984        if (!release) {
 985                /*
 986                 * Drop the in-flight state if the buffer is already on the LRU
 987                 * and it holds the only reference. This is racy because we
 988                 * haven't acquired the pag lock, but the use of _XBF_IN_FLIGHT
 989                 * ensures the decrement occurs only once per-buf.
 990                 */
 991                if ((atomic_read(&bp->b_hold) == 1) && !list_empty(&bp->b_lru))
 992                        __xfs_buf_ioacct_dec(bp);
 993                goto out_unlock;
 994        }
 995
 996        /* the last reference has been dropped ... */
 997        __xfs_buf_ioacct_dec(bp);
 998        if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
 999                /*
1000                 * If the buffer is added to the LRU take a new reference to the
1001                 * buffer for the LRU and clear the (now stale) dispose list
1002                 * state flag
1003                 */
1004                if (list_lru_add(&bp->b_target->bt_lru, &bp->b_lru)) {
1005                        bp->b_state &= ~XFS_BSTATE_DISPOSE;
1006                        atomic_inc(&bp->b_hold);
1007                }
1008                spin_unlock(&pag->pag_buf_lock);
1009        } else {
1010                /*
1011                 * most of the time buffers will already be removed from the
1012                 * LRU, so optimise that case by checking for the
1013                 * XFS_BSTATE_DISPOSE flag indicating the last list the buffer
1014                 * was on was the disposal list
1015                 */
1016                if (!(bp->b_state & XFS_BSTATE_DISPOSE)) {
1017                        list_lru_del(&bp->b_target->bt_lru, &bp->b_lru);
1018                } else {
1019                        ASSERT(list_empty(&bp->b_lru));
1020                }
1021
1022                ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1023                rhashtable_remove_fast(&pag->pag_buf_hash, &bp->b_rhash_head,
1024                                       xfs_buf_hash_params);
1025                spin_unlock(&pag->pag_buf_lock);
1026                xfs_perag_put(pag);
1027                freebuf = true;
1028        }
1029
1030out_unlock:
1031        spin_unlock(&bp->b_lock);
1032
1033        if (freebuf)
1034                xfs_buf_free(bp);
1035}
1036
1037
1038/*
1039 *      Lock a buffer object, if it is not already locked.
1040 *
1041 *      If we come across a stale, pinned, locked buffer, we know that we are
1042 *      being asked to lock a buffer that has been reallocated. Because it is
1043 *      pinned, we know that the log has not been pushed to disk and hence it
1044 *      will still be locked.  Rather than continuing to have trylock attempts
1045 *      fail until someone else pushes the log, push it ourselves before
1046 *      returning.  This means that the xfsaild will not get stuck trying
1047 *      to push on stale inode buffers.
1048 */
1049int
1050xfs_buf_trylock(
1051        struct xfs_buf          *bp)
1052{
1053        int                     locked;
1054
1055        locked = down_trylock(&bp->b_sema) == 0;
1056        if (locked)
1057                trace_xfs_buf_trylock(bp, _RET_IP_);
1058        else
1059                trace_xfs_buf_trylock_fail(bp, _RET_IP_);
1060        return locked;
1061}
1062
1063/*
1064 *      Lock a buffer object.
1065 *
1066 *      If we come across a stale, pinned, locked buffer, we know that we
1067 *      are being asked to lock a buffer that has been reallocated. Because
1068 *      it is pinned, we know that the log has not been pushed to disk and
1069 *      hence it will still be locked. Rather than sleeping until someone
1070 *      else pushes the log, push it ourselves before trying to get the lock.
1071 */
1072void
1073xfs_buf_lock(
1074        struct xfs_buf          *bp)
1075{
1076        trace_xfs_buf_lock(bp, _RET_IP_);
1077
1078        if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
1079                xfs_log_force(bp->b_mount, 0);
1080        down(&bp->b_sema);
1081
1082        trace_xfs_buf_lock_done(bp, _RET_IP_);
1083}
1084
1085void
1086xfs_buf_unlock(
1087        struct xfs_buf          *bp)
1088{
1089        ASSERT(xfs_buf_islocked(bp));
1090
1091        up(&bp->b_sema);
1092        trace_xfs_buf_unlock(bp, _RET_IP_);
1093}
1094
1095STATIC void
1096xfs_buf_wait_unpin(
1097        struct xfs_buf          *bp)
1098{
1099        DECLARE_WAITQUEUE       (wait, current);
1100
1101        if (atomic_read(&bp->b_pin_count) == 0)
1102                return;
1103
1104        add_wait_queue(&bp->b_waiters, &wait);
1105        for (;;) {
1106                set_current_state(TASK_UNINTERRUPTIBLE);
1107                if (atomic_read(&bp->b_pin_count) == 0)
1108                        break;
1109                io_schedule();
1110        }
1111        remove_wait_queue(&bp->b_waiters, &wait);
1112        set_current_state(TASK_RUNNING);
1113}
1114
1115static void
1116xfs_buf_ioerror_alert_ratelimited(
1117        struct xfs_buf          *bp)
1118{
1119        static unsigned long    lasttime;
1120        static struct xfs_buftarg *lasttarg;
1121
1122        if (bp->b_target != lasttarg ||
1123            time_after(jiffies, (lasttime + 5*HZ))) {
1124                lasttime = jiffies;
1125                xfs_buf_ioerror_alert(bp, __this_address);
1126        }
1127        lasttarg = bp->b_target;
1128}
1129
1130/*
1131 * Account for this latest trip around the retry handler, and decide if
1132 * we've failed enough times to constitute a permanent failure.
1133 */
1134static bool
1135xfs_buf_ioerror_permanent(
1136        struct xfs_buf          *bp,
1137        struct xfs_error_cfg    *cfg)
1138{
1139        struct xfs_mount        *mp = bp->b_mount;
1140
1141        if (cfg->max_retries != XFS_ERR_RETRY_FOREVER &&
1142            ++bp->b_retries > cfg->max_retries)
1143                return true;
1144        if (cfg->retry_timeout != XFS_ERR_RETRY_FOREVER &&
1145            time_after(jiffies, cfg->retry_timeout + bp->b_first_retry_time))
1146                return true;
1147
1148        /* At unmount we may treat errors differently */
1149        if (xfs_is_unmounting(mp) && mp->m_fail_unmount)
1150                return true;
1151
1152        return false;
1153}
1154
1155/*
1156 * On a sync write or shutdown we just want to stale the buffer and let the
1157 * caller handle the error in bp->b_error appropriately.
1158 *
1159 * If the write was asynchronous then no one will be looking for the error.  If
1160 * this is the first failure of this type, clear the error state and write the
1161 * buffer out again. This means we always retry an async write failure at least
1162 * once, but we also need to set the buffer up to behave correctly now for
1163 * repeated failures.
1164 *
1165 * If we get repeated async write failures, then we take action according to the
1166 * error configuration we have been set up to use.
1167 *
1168 * Returns true if this function took care of error handling and the caller must
1169 * not touch the buffer again.  Return false if the caller should proceed with
1170 * normal I/O completion handling.
1171 */
1172static bool
1173xfs_buf_ioend_handle_error(
1174        struct xfs_buf          *bp)
1175{
1176        struct xfs_mount        *mp = bp->b_mount;
1177        struct xfs_error_cfg    *cfg;
1178
1179        /*
1180         * If we've already decided to shutdown the filesystem because of I/O
1181         * errors, there's no point in giving this a retry.
1182         */
1183        if (xfs_is_shutdown(mp))
1184                goto out_stale;
1185
1186        xfs_buf_ioerror_alert_ratelimited(bp);
1187
1188        /*
1189         * We're not going to bother about retrying this during recovery.
1190         * One strike!
1191         */
1192        if (bp->b_flags & _XBF_LOGRECOVERY) {
1193                xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR);
1194                return false;
1195        }
1196
1197        /*
1198         * Synchronous writes will have callers process the error.
1199         */
1200        if (!(bp->b_flags & XBF_ASYNC))
1201                goto out_stale;
1202
1203        trace_xfs_buf_iodone_async(bp, _RET_IP_);
1204
1205        cfg = xfs_error_get_cfg(mp, XFS_ERR_METADATA, bp->b_error);
1206        if (bp->b_last_error != bp->b_error ||
1207            !(bp->b_flags & (XBF_STALE | XBF_WRITE_FAIL))) {
1208                bp->b_last_error = bp->b_error;
1209                if (cfg->retry_timeout != XFS_ERR_RETRY_FOREVER &&
1210                    !bp->b_first_retry_time)
1211                        bp->b_first_retry_time = jiffies;
1212                goto resubmit;
1213        }
1214
1215        /*
1216         * Permanent error - we need to trigger a shutdown if we haven't already
1217         * to indicate that inconsistency will result from this action.
1218         */
1219        if (xfs_buf_ioerror_permanent(bp, cfg)) {
1220                xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR);
1221                goto out_stale;
1222        }
1223
1224        /* Still considered a transient error. Caller will schedule retries. */
1225        if (bp->b_flags & _XBF_INODES)
1226                xfs_buf_inode_io_fail(bp);
1227        else if (bp->b_flags & _XBF_DQUOTS)
1228                xfs_buf_dquot_io_fail(bp);
1229        else
1230                ASSERT(list_empty(&bp->b_li_list));
1231        xfs_buf_ioerror(bp, 0);
1232        xfs_buf_relse(bp);
1233        return true;
1234
1235resubmit:
1236        xfs_buf_ioerror(bp, 0);
1237        bp->b_flags |= (XBF_DONE | XBF_WRITE_FAIL);
1238        xfs_buf_submit(bp);
1239        return true;
1240out_stale:
1241        xfs_buf_stale(bp);
1242        bp->b_flags |= XBF_DONE;
1243        bp->b_flags &= ~XBF_WRITE;
1244        trace_xfs_buf_error_relse(bp, _RET_IP_);
1245        return false;
1246}
1247
1248static void
1249xfs_buf_ioend(
1250        struct xfs_buf  *bp)
1251{
1252        trace_xfs_buf_iodone(bp, _RET_IP_);
1253
1254        /*
1255         * Pull in IO completion errors now. We are guaranteed to be running
1256         * single threaded, so we don't need the lock to read b_io_error.
1257         */
1258        if (!bp->b_error && bp->b_io_error)
1259                xfs_buf_ioerror(bp, bp->b_io_error);
1260
1261        if (bp->b_flags & XBF_READ) {
1262                if (!bp->b_error && bp->b_ops)
1263                        bp->b_ops->verify_read(bp);
1264                if (!bp->b_error)
1265                        bp->b_flags |= XBF_DONE;
1266        } else {
1267                if (!bp->b_error) {
1268                        bp->b_flags &= ~XBF_WRITE_FAIL;
1269                        bp->b_flags |= XBF_DONE;
1270                }
1271
1272                if (unlikely(bp->b_error) && xfs_buf_ioend_handle_error(bp))
1273                        return;
1274
1275                /* clear the retry state */
1276                bp->b_last_error = 0;
1277                bp->b_retries = 0;
1278                bp->b_first_retry_time = 0;
1279
1280                /*
1281                 * Note that for things like remote attribute buffers, there may
1282                 * not be a buffer log item here, so processing the buffer log
1283                 * item must remain optional.
1284                 */
1285                if (bp->b_log_item)
1286                        xfs_buf_item_done(bp);
1287
1288                if (bp->b_flags & _XBF_INODES)
1289                        xfs_buf_inode_iodone(bp);
1290                else if (bp->b_flags & _XBF_DQUOTS)
1291                        xfs_buf_dquot_iodone(bp);
1292
1293        }
1294
1295        bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD |
1296                         _XBF_LOGRECOVERY);
1297
1298        if (bp->b_flags & XBF_ASYNC)
1299                xfs_buf_relse(bp);
1300        else
1301                complete(&bp->b_iowait);
1302}
1303
1304static void
1305xfs_buf_ioend_work(
1306        struct work_struct      *work)
1307{
1308        struct xfs_buf          *bp =
1309                container_of(work, struct xfs_buf, b_ioend_work);
1310
1311        xfs_buf_ioend(bp);
1312}
1313
1314static void
1315xfs_buf_ioend_async(
1316        struct xfs_buf  *bp)
1317{
1318        INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work);
1319        queue_work(bp->b_mount->m_buf_workqueue, &bp->b_ioend_work);
1320}
1321
1322void
1323__xfs_buf_ioerror(
1324        struct xfs_buf          *bp,
1325        int                     error,
1326        xfs_failaddr_t          failaddr)
1327{
1328        ASSERT(error <= 0 && error >= -1000);
1329        bp->b_error = error;
1330        trace_xfs_buf_ioerror(bp, error, failaddr);
1331}
1332
1333void
1334xfs_buf_ioerror_alert(
1335        struct xfs_buf          *bp,
1336        xfs_failaddr_t          func)
1337{
1338        xfs_buf_alert_ratelimited(bp, "XFS: metadata IO error",
1339                "metadata I/O error in \"%pS\" at daddr 0x%llx len %d error %d",
1340                                  func, (uint64_t)xfs_buf_daddr(bp),
1341                                  bp->b_length, -bp->b_error);
1342}
1343
1344/*
1345 * To simulate an I/O failure, the buffer must be locked and held with at least
1346 * three references. The LRU reference is dropped by the stale call. The buf
1347 * item reference is dropped via ioend processing. The third reference is owned
1348 * by the caller and is dropped on I/O completion if the buffer is XBF_ASYNC.
1349 */
1350void
1351xfs_buf_ioend_fail(
1352        struct xfs_buf  *bp)
1353{
1354        bp->b_flags &= ~XBF_DONE;
1355        xfs_buf_stale(bp);
1356        xfs_buf_ioerror(bp, -EIO);
1357        xfs_buf_ioend(bp);
1358}
1359
1360int
1361xfs_bwrite(
1362        struct xfs_buf          *bp)
1363{
1364        int                     error;
1365
1366        ASSERT(xfs_buf_islocked(bp));
1367
1368        bp->b_flags |= XBF_WRITE;
1369        bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q |
1370                         XBF_DONE);
1371
1372        error = xfs_buf_submit(bp);
1373        if (error)
1374                xfs_force_shutdown(bp->b_mount, SHUTDOWN_META_IO_ERROR);
1375        return error;
1376}
1377
1378static void
1379xfs_buf_bio_end_io(
1380        struct bio              *bio)
1381{
1382        struct xfs_buf          *bp = (struct xfs_buf *)bio->bi_private;
1383
1384        if (!bio->bi_status &&
1385            (bp->b_flags & XBF_WRITE) && (bp->b_flags & XBF_ASYNC) &&
1386            XFS_TEST_ERROR(false, bp->b_mount, XFS_ERRTAG_BUF_IOERROR))
1387                bio->bi_status = BLK_STS_IOERR;
1388
1389        /*
1390         * don't overwrite existing errors - otherwise we can lose errors on
1391         * buffers that require multiple bios to complete.
1392         */
1393        if (bio->bi_status) {
1394                int error = blk_status_to_errno(bio->bi_status);
1395
1396                cmpxchg(&bp->b_io_error, 0, error);
1397        }
1398
1399        if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
1400                invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
1401
1402        if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
1403                xfs_buf_ioend_async(bp);
1404        bio_put(bio);
1405}
1406
1407static void
1408xfs_buf_ioapply_map(
1409        struct xfs_buf  *bp,
1410        int             map,
1411        int             *buf_offset,
1412        int             *count,
1413        int             op)
1414{
1415        int             page_index;
1416        unsigned int    total_nr_pages = bp->b_page_count;
1417        int             nr_pages;
1418        struct bio      *bio;
1419        sector_t        sector =  bp->b_maps[map].bm_bn;
1420        int             size;
1421        int             offset;
1422
1423        /* skip the pages in the buffer before the start offset */
1424        page_index = 0;
1425        offset = *buf_offset;
1426        while (offset >= PAGE_SIZE) {
1427                page_index++;
1428                offset -= PAGE_SIZE;
1429        }
1430
1431        /*
1432         * Limit the IO size to the length of the current vector, and update the
1433         * remaining IO count for the next time around.
1434         */
1435        size = min_t(int, BBTOB(bp->b_maps[map].bm_len), *count);
1436        *count -= size;
1437        *buf_offset += size;
1438
1439next_chunk:
1440        atomic_inc(&bp->b_io_remaining);
1441        nr_pages = bio_max_segs(total_nr_pages);
1442
1443        bio = bio_alloc(GFP_NOIO, nr_pages);
1444        bio_set_dev(bio, bp->b_target->bt_bdev);
1445        bio->bi_iter.bi_sector = sector;
1446        bio->bi_end_io = xfs_buf_bio_end_io;
1447        bio->bi_private = bp;
1448        bio->bi_opf = op;
1449
1450        for (; size && nr_pages; nr_pages--, page_index++) {
1451                int     rbytes, nbytes = PAGE_SIZE - offset;
1452
1453                if (nbytes > size)
1454                        nbytes = size;
1455
1456                rbytes = bio_add_page(bio, bp->b_pages[page_index], nbytes,
1457                                      offset);
1458                if (rbytes < nbytes)
1459                        break;
1460
1461                offset = 0;
1462                sector += BTOBB(nbytes);
1463                size -= nbytes;
1464                total_nr_pages--;
1465        }
1466
1467        if (likely(bio->bi_iter.bi_size)) {
1468                if (xfs_buf_is_vmapped(bp)) {
1469                        flush_kernel_vmap_range(bp->b_addr,
1470                                                xfs_buf_vmap_len(bp));
1471                }
1472                submit_bio(bio);
1473                if (size)
1474                        goto next_chunk;
1475        } else {
1476                /*
1477                 * This is guaranteed not to be the last io reference count
1478                 * because the caller (xfs_buf_submit) holds a count itself.
1479                 */
1480                atomic_dec(&bp->b_io_remaining);
1481                xfs_buf_ioerror(bp, -EIO);
1482                bio_put(bio);
1483        }
1484
1485}
1486
1487STATIC void
1488_xfs_buf_ioapply(
1489        struct xfs_buf  *bp)
1490{
1491        struct blk_plug plug;
1492        int             op;
1493        int             offset;
1494        int             size;
1495        int             i;
1496
1497        /*
1498         * Make sure we capture only current IO errors rather than stale errors
1499         * left over from previous use of the buffer (e.g. failed readahead).
1500         */
1501        bp->b_error = 0;
1502
1503        if (bp->b_flags & XBF_WRITE) {
1504                op = REQ_OP_WRITE;
1505
1506                /*
1507                 * Run the write verifier callback function if it exists. If
1508                 * this function fails it will mark the buffer with an error and
1509                 * the IO should not be dispatched.
1510                 */
1511                if (bp->b_ops) {
1512                        bp->b_ops->verify_write(bp);
1513                        if (bp->b_error) {
1514                                xfs_force_shutdown(bp->b_mount,
1515                                                   SHUTDOWN_CORRUPT_INCORE);
1516                                return;
1517                        }
1518                } else if (bp->b_rhash_key != XFS_BUF_DADDR_NULL) {
1519                        struct xfs_mount *mp = bp->b_mount;
1520
1521                        /*
1522                         * non-crc filesystems don't attach verifiers during
1523                         * log recovery, so don't warn for such filesystems.
1524                         */
1525                        if (xfs_has_crc(mp)) {
1526                                xfs_warn(mp,
1527                                        "%s: no buf ops on daddr 0x%llx len %d",
1528                                        __func__, xfs_buf_daddr(bp),
1529                                        bp->b_length);
1530                                xfs_hex_dump(bp->b_addr,
1531                                                XFS_CORRUPTION_DUMP_LEN);
1532                                dump_stack();
1533                        }
1534                }
1535        } else {
1536                op = REQ_OP_READ;
1537                if (bp->b_flags & XBF_READ_AHEAD)
1538                        op |= REQ_RAHEAD;
1539        }
1540
1541        /* we only use the buffer cache for meta-data */
1542        op |= REQ_META;
1543
1544        /*
1545         * Walk all the vectors issuing IO on them. Set up the initial offset
1546         * into the buffer and the desired IO size before we start -
1547         * _xfs_buf_ioapply_vec() will modify them appropriately for each
1548         * subsequent call.
1549         */
1550        offset = bp->b_offset;
1551        size = BBTOB(bp->b_length);
1552        blk_start_plug(&plug);
1553        for (i = 0; i < bp->b_map_count; i++) {
1554                xfs_buf_ioapply_map(bp, i, &offset, &size, op);
1555                if (bp->b_error)
1556                        break;
1557                if (size <= 0)
1558                        break;  /* all done */
1559        }
1560        blk_finish_plug(&plug);
1561}
1562
1563/*
1564 * Wait for I/O completion of a sync buffer and return the I/O error code.
1565 */
1566static int
1567xfs_buf_iowait(
1568        struct xfs_buf  *bp)
1569{
1570        ASSERT(!(bp->b_flags & XBF_ASYNC));
1571
1572        trace_xfs_buf_iowait(bp, _RET_IP_);
1573        wait_for_completion(&bp->b_iowait);
1574        trace_xfs_buf_iowait_done(bp, _RET_IP_);
1575
1576        return bp->b_error;
1577}
1578
1579/*
1580 * Buffer I/O submission path, read or write. Asynchronous submission transfers
1581 * the buffer lock ownership and the current reference to the IO. It is not
1582 * safe to reference the buffer after a call to this function unless the caller
1583 * holds an additional reference itself.
1584 */
1585static int
1586__xfs_buf_submit(
1587        struct xfs_buf  *bp,
1588        bool            wait)
1589{
1590        int             error = 0;
1591
1592        trace_xfs_buf_submit(bp, _RET_IP_);
1593
1594        ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1595
1596        /* on shutdown we stale and complete the buffer immediately */
1597        if (xfs_is_shutdown(bp->b_mount)) {
1598                xfs_buf_ioend_fail(bp);
1599                return -EIO;
1600        }
1601
1602        /*
1603         * Grab a reference so the buffer does not go away underneath us. For
1604         * async buffers, I/O completion drops the callers reference, which
1605         * could occur before submission returns.
1606         */
1607        xfs_buf_hold(bp);
1608
1609        if (bp->b_flags & XBF_WRITE)
1610                xfs_buf_wait_unpin(bp);
1611
1612        /* clear the internal error state to avoid spurious errors */
1613        bp->b_io_error = 0;
1614
1615        /*
1616         * Set the count to 1 initially, this will stop an I/O completion
1617         * callout which happens before we have started all the I/O from calling
1618         * xfs_buf_ioend too early.
1619         */
1620        atomic_set(&bp->b_io_remaining, 1);
1621        if (bp->b_flags & XBF_ASYNC)
1622                xfs_buf_ioacct_inc(bp);
1623        _xfs_buf_ioapply(bp);
1624
1625        /*
1626         * If _xfs_buf_ioapply failed, we can get back here with only the IO
1627         * reference we took above. If we drop it to zero, run completion so
1628         * that we don't return to the caller with completion still pending.
1629         */
1630        if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
1631                if (bp->b_error || !(bp->b_flags & XBF_ASYNC))
1632                        xfs_buf_ioend(bp);
1633                else
1634                        xfs_buf_ioend_async(bp);
1635        }
1636
1637        if (wait)
1638                error = xfs_buf_iowait(bp);
1639
1640        /*
1641         * Release the hold that keeps the buffer referenced for the entire
1642         * I/O. Note that if the buffer is async, it is not safe to reference
1643         * after this release.
1644         */
1645        xfs_buf_rele(bp);
1646        return error;
1647}
1648
1649void *
1650xfs_buf_offset(
1651        struct xfs_buf          *bp,
1652        size_t                  offset)
1653{
1654        struct page             *page;
1655
1656        if (bp->b_addr)
1657                return bp->b_addr + offset;
1658
1659        page = bp->b_pages[offset >> PAGE_SHIFT];
1660        return page_address(page) + (offset & (PAGE_SIZE-1));
1661}
1662
1663void
1664xfs_buf_zero(
1665        struct xfs_buf          *bp,
1666        size_t                  boff,
1667        size_t                  bsize)
1668{
1669        size_t                  bend;
1670
1671        bend = boff + bsize;
1672        while (boff < bend) {
1673                struct page     *page;
1674                int             page_index, page_offset, csize;
1675
1676                page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
1677                page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
1678                page = bp->b_pages[page_index];
1679                csize = min_t(size_t, PAGE_SIZE - page_offset,
1680                                      BBTOB(bp->b_length) - boff);
1681
1682                ASSERT((csize + page_offset) <= PAGE_SIZE);
1683
1684                memset(page_address(page) + page_offset, 0, csize);
1685
1686                boff += csize;
1687        }
1688}
1689
1690/*
1691 * Log a message about and stale a buffer that a caller has decided is corrupt.
1692 *
1693 * This function should be called for the kinds of metadata corruption that
1694 * cannot be detect from a verifier, such as incorrect inter-block relationship
1695 * data.  Do /not/ call this function from a verifier function.
1696 *
1697 * The buffer must be XBF_DONE prior to the call.  Afterwards, the buffer will
1698 * be marked stale, but b_error will not be set.  The caller is responsible for
1699 * releasing the buffer or fixing it.
1700 */
1701void
1702__xfs_buf_mark_corrupt(
1703        struct xfs_buf          *bp,
1704        xfs_failaddr_t          fa)
1705{
1706        ASSERT(bp->b_flags & XBF_DONE);
1707
1708        xfs_buf_corruption_error(bp, fa);
1709        xfs_buf_stale(bp);
1710}
1711
1712/*
1713 *      Handling of buffer targets (buftargs).
1714 */
1715
1716/*
1717 * Wait for any bufs with callbacks that have been submitted but have not yet
1718 * returned. These buffers will have an elevated hold count, so wait on those
1719 * while freeing all the buffers only held by the LRU.
1720 */
1721static enum lru_status
1722xfs_buftarg_drain_rele(
1723        struct list_head        *item,
1724        struct list_lru_one     *lru,
1725        spinlock_t              *lru_lock,
1726        void                    *arg)
1727
1728{
1729        struct xfs_buf          *bp = container_of(item, struct xfs_buf, b_lru);
1730        struct list_head        *dispose = arg;
1731
1732        if (atomic_read(&bp->b_hold) > 1) {
1733                /* need to wait, so skip it this pass */
1734                trace_xfs_buf_drain_buftarg(bp, _RET_IP_);
1735                return LRU_SKIP;
1736        }
1737        if (!spin_trylock(&bp->b_lock))
1738                return LRU_SKIP;
1739
1740        /*
1741         * clear the LRU reference count so the buffer doesn't get
1742         * ignored in xfs_buf_rele().
1743         */
1744        atomic_set(&bp->b_lru_ref, 0);
1745        bp->b_state |= XFS_BSTATE_DISPOSE;
1746        list_lru_isolate_move(lru, item, dispose);
1747        spin_unlock(&bp->b_lock);
1748        return LRU_REMOVED;
1749}
1750
1751/*
1752 * Wait for outstanding I/O on the buftarg to complete.
1753 */
1754void
1755xfs_buftarg_wait(
1756        struct xfs_buftarg      *btp)
1757{
1758        /*
1759         * First wait on the buftarg I/O count for all in-flight buffers to be
1760         * released. This is critical as new buffers do not make the LRU until
1761         * they are released.
1762         *
1763         * Next, flush the buffer workqueue to ensure all completion processing
1764         * has finished. Just waiting on buffer locks is not sufficient for
1765         * async IO as the reference count held over IO is not released until
1766         * after the buffer lock is dropped. Hence we need to ensure here that
1767         * all reference counts have been dropped before we start walking the
1768         * LRU list.
1769         */
1770        while (percpu_counter_sum(&btp->bt_io_count))
1771                delay(100);
1772        flush_workqueue(btp->bt_mount->m_buf_workqueue);
1773}
1774
1775void
1776xfs_buftarg_drain(
1777        struct xfs_buftarg      *btp)
1778{
1779        LIST_HEAD(dispose);
1780        int                     loop = 0;
1781        bool                    write_fail = false;
1782
1783        xfs_buftarg_wait(btp);
1784
1785        /* loop until there is nothing left on the lru list. */
1786        while (list_lru_count(&btp->bt_lru)) {
1787                list_lru_walk(&btp->bt_lru, xfs_buftarg_drain_rele,
1788                              &dispose, LONG_MAX);
1789
1790                while (!list_empty(&dispose)) {
1791                        struct xfs_buf *bp;
1792                        bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1793                        list_del_init(&bp->b_lru);
1794                        if (bp->b_flags & XBF_WRITE_FAIL) {
1795                                write_fail = true;
1796                                xfs_buf_alert_ratelimited(bp,
1797                                        "XFS: Corruption Alert",
1798"Corruption Alert: Buffer at daddr 0x%llx had permanent write failures!",
1799                                        (long long)xfs_buf_daddr(bp));
1800                        }
1801                        xfs_buf_rele(bp);
1802                }
1803                if (loop++ != 0)
1804                        delay(100);
1805        }
1806
1807        /*
1808         * If one or more failed buffers were freed, that means dirty metadata
1809         * was thrown away. This should only ever happen after I/O completion
1810         * handling has elevated I/O error(s) to permanent failures and shuts
1811         * down the fs.
1812         */
1813        if (write_fail) {
1814                ASSERT(xfs_is_shutdown(btp->bt_mount));
1815                xfs_alert(btp->bt_mount,
1816              "Please run xfs_repair to determine the extent of the problem.");
1817        }
1818}
1819
1820static enum lru_status
1821xfs_buftarg_isolate(
1822        struct list_head        *item,
1823        struct list_lru_one     *lru,
1824        spinlock_t              *lru_lock,
1825        void                    *arg)
1826{
1827        struct xfs_buf          *bp = container_of(item, struct xfs_buf, b_lru);
1828        struct list_head        *dispose = arg;
1829
1830        /*
1831         * we are inverting the lru lock/bp->b_lock here, so use a trylock.
1832         * If we fail to get the lock, just skip it.
1833         */
1834        if (!spin_trylock(&bp->b_lock))
1835                return LRU_SKIP;
1836        /*
1837         * Decrement the b_lru_ref count unless the value is already
1838         * zero. If the value is already zero, we need to reclaim the
1839         * buffer, otherwise it gets another trip through the LRU.
1840         */
1841        if (atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
1842                spin_unlock(&bp->b_lock);
1843                return LRU_ROTATE;
1844        }
1845
1846        bp->b_state |= XFS_BSTATE_DISPOSE;
1847        list_lru_isolate_move(lru, item, dispose);
1848        spin_unlock(&bp->b_lock);
1849        return LRU_REMOVED;
1850}
1851
1852static unsigned long
1853xfs_buftarg_shrink_scan(
1854        struct shrinker         *shrink,
1855        struct shrink_control   *sc)
1856{
1857        struct xfs_buftarg      *btp = container_of(shrink,
1858                                        struct xfs_buftarg, bt_shrinker);
1859        LIST_HEAD(dispose);
1860        unsigned long           freed;
1861
1862        freed = list_lru_shrink_walk(&btp->bt_lru, sc,
1863                                     xfs_buftarg_isolate, &dispose);
1864
1865        while (!list_empty(&dispose)) {
1866                struct xfs_buf *bp;
1867                bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1868                list_del_init(&bp->b_lru);
1869                xfs_buf_rele(bp);
1870        }
1871
1872        return freed;
1873}
1874
1875static unsigned long
1876xfs_buftarg_shrink_count(
1877        struct shrinker         *shrink,
1878        struct shrink_control   *sc)
1879{
1880        struct xfs_buftarg      *btp = container_of(shrink,
1881                                        struct xfs_buftarg, bt_shrinker);
1882        return list_lru_shrink_count(&btp->bt_lru, sc);
1883}
1884
1885void
1886xfs_free_buftarg(
1887        struct xfs_buftarg      *btp)
1888{
1889        unregister_shrinker(&btp->bt_shrinker);
1890        ASSERT(percpu_counter_sum(&btp->bt_io_count) == 0);
1891        percpu_counter_destroy(&btp->bt_io_count);
1892        list_lru_destroy(&btp->bt_lru);
1893
1894        blkdev_issue_flush(btp->bt_bdev);
1895
1896        kmem_free(btp);
1897}
1898
1899int
1900xfs_setsize_buftarg(
1901        xfs_buftarg_t           *btp,
1902        unsigned int            sectorsize)
1903{
1904        /* Set up metadata sector size info */
1905        btp->bt_meta_sectorsize = sectorsize;
1906        btp->bt_meta_sectormask = sectorsize - 1;
1907
1908        if (set_blocksize(btp->bt_bdev, sectorsize)) {
1909                xfs_warn(btp->bt_mount,
1910                        "Cannot set_blocksize to %u on device %pg",
1911                        sectorsize, btp->bt_bdev);
1912                return -EINVAL;
1913        }
1914
1915        /* Set up device logical sector size mask */
1916        btp->bt_logical_sectorsize = bdev_logical_block_size(btp->bt_bdev);
1917        btp->bt_logical_sectormask = bdev_logical_block_size(btp->bt_bdev) - 1;
1918
1919        return 0;
1920}
1921
1922/*
1923 * When allocating the initial buffer target we have not yet
1924 * read in the superblock, so don't know what sized sectors
1925 * are being used at this early stage.  Play safe.
1926 */
1927STATIC int
1928xfs_setsize_buftarg_early(
1929        xfs_buftarg_t           *btp,
1930        struct block_device     *bdev)
1931{
1932        return xfs_setsize_buftarg(btp, bdev_logical_block_size(bdev));
1933}
1934
1935xfs_buftarg_t *
1936xfs_alloc_buftarg(
1937        struct xfs_mount        *mp,
1938        struct block_device     *bdev,
1939        struct dax_device       *dax_dev)
1940{
1941        xfs_buftarg_t           *btp;
1942
1943        btp = kmem_zalloc(sizeof(*btp), KM_NOFS);
1944
1945        btp->bt_mount = mp;
1946        btp->bt_dev =  bdev->bd_dev;
1947        btp->bt_bdev = bdev;
1948        btp->bt_daxdev = dax_dev;
1949
1950        /*
1951         * Buffer IO error rate limiting. Limit it to no more than 10 messages
1952         * per 30 seconds so as to not spam logs too much on repeated errors.
1953         */
1954        ratelimit_state_init(&btp->bt_ioerror_rl, 30 * HZ,
1955                             DEFAULT_RATELIMIT_BURST);
1956
1957        if (xfs_setsize_buftarg_early(btp, bdev))
1958                goto error_free;
1959
1960        if (list_lru_init(&btp->bt_lru))
1961                goto error_free;
1962
1963        if (percpu_counter_init(&btp->bt_io_count, 0, GFP_KERNEL))
1964                goto error_lru;
1965
1966        btp->bt_shrinker.count_objects = xfs_buftarg_shrink_count;
1967        btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
1968        btp->bt_shrinker.seeks = DEFAULT_SEEKS;
1969        btp->bt_shrinker.flags = SHRINKER_NUMA_AWARE;
1970        if (register_shrinker(&btp->bt_shrinker))
1971                goto error_pcpu;
1972        return btp;
1973
1974error_pcpu:
1975        percpu_counter_destroy(&btp->bt_io_count);
1976error_lru:
1977        list_lru_destroy(&btp->bt_lru);
1978error_free:
1979        kmem_free(btp);
1980        return NULL;
1981}
1982
1983/*
1984 * Cancel a delayed write list.
1985 *
1986 * Remove each buffer from the list, clear the delwri queue flag and drop the
1987 * associated buffer reference.
1988 */
1989void
1990xfs_buf_delwri_cancel(
1991        struct list_head        *list)
1992{
1993        struct xfs_buf          *bp;
1994
1995        while (!list_empty(list)) {
1996                bp = list_first_entry(list, struct xfs_buf, b_list);
1997
1998                xfs_buf_lock(bp);
1999                bp->b_flags &= ~_XBF_DELWRI_Q;
2000                list_del_init(&bp->b_list);
2001                xfs_buf_relse(bp);
2002        }
2003}
2004
2005/*
2006 * Add a buffer to the delayed write list.
2007 *
2008 * This queues a buffer for writeout if it hasn't already been.  Note that
2009 * neither this routine nor the buffer list submission functions perform
2010 * any internal synchronization.  It is expected that the lists are thread-local
2011 * to the callers.
2012 *
2013 * Returns true if we queued up the buffer, or false if it already had
2014 * been on the buffer list.
2015 */
2016bool
2017xfs_buf_delwri_queue(
2018        struct xfs_buf          *bp,
2019        struct list_head        *list)
2020{
2021        ASSERT(xfs_buf_islocked(bp));
2022        ASSERT(!(bp->b_flags & XBF_READ));
2023
2024        /*
2025         * If the buffer is already marked delwri it already is queued up
2026         * by someone else for imediate writeout.  Just ignore it in that
2027         * case.
2028         */
2029        if (bp->b_flags & _XBF_DELWRI_Q) {
2030                trace_xfs_buf_delwri_queued(bp, _RET_IP_);
2031                return false;
2032        }
2033
2034        trace_xfs_buf_delwri_queue(bp, _RET_IP_);
2035
2036        /*
2037         * If a buffer gets written out synchronously or marked stale while it
2038         * is on a delwri list we lazily remove it. To do this, the other party
2039         * clears the  _XBF_DELWRI_Q flag but otherwise leaves the buffer alone.
2040         * It remains referenced and on the list.  In a rare corner case it
2041         * might get readded to a delwri list after the synchronous writeout, in
2042         * which case we need just need to re-add the flag here.
2043         */
2044        bp->b_flags |= _XBF_DELWRI_Q;
2045        if (list_empty(&bp->b_list)) {
2046                atomic_inc(&bp->b_hold);
2047                list_add_tail(&bp->b_list, list);
2048        }
2049
2050        return true;
2051}
2052
2053/*
2054 * Compare function is more complex than it needs to be because
2055 * the return value is only 32 bits and we are doing comparisons
2056 * on 64 bit values
2057 */
2058static int
2059xfs_buf_cmp(
2060        void                    *priv,
2061        const struct list_head  *a,
2062        const struct list_head  *b)
2063{
2064        struct xfs_buf  *ap = container_of(a, struct xfs_buf, b_list);
2065        struct xfs_buf  *bp = container_of(b, struct xfs_buf, b_list);
2066        xfs_daddr_t             diff;
2067
2068        diff = ap->b_maps[0].bm_bn - bp->b_maps[0].bm_bn;
2069        if (diff < 0)
2070                return -1;
2071        if (diff > 0)
2072                return 1;
2073        return 0;
2074}
2075
2076/*
2077 * Submit buffers for write. If wait_list is specified, the buffers are
2078 * submitted using sync I/O and placed on the wait list such that the caller can
2079 * iowait each buffer. Otherwise async I/O is used and the buffers are released
2080 * at I/O completion time. In either case, buffers remain locked until I/O
2081 * completes and the buffer is released from the queue.
2082 */
2083static int
2084xfs_buf_delwri_submit_buffers(
2085        struct list_head        *buffer_list,
2086        struct list_head        *wait_list)
2087{
2088        struct xfs_buf          *bp, *n;
2089        int                     pinned = 0;
2090        struct blk_plug         plug;
2091
2092        list_sort(NULL, buffer_list, xfs_buf_cmp);
2093
2094        blk_start_plug(&plug);
2095        list_for_each_entry_safe(bp, n, buffer_list, b_list) {
2096                if (!wait_list) {
2097                        if (xfs_buf_ispinned(bp)) {
2098                                pinned++;
2099                                continue;
2100                        }
2101                        if (!xfs_buf_trylock(bp))
2102                                continue;
2103                } else {
2104                        xfs_buf_lock(bp);
2105                }
2106
2107                /*
2108                 * Someone else might have written the buffer synchronously or
2109                 * marked it stale in the meantime.  In that case only the
2110                 * _XBF_DELWRI_Q flag got cleared, and we have to drop the
2111                 * reference and remove it from the list here.
2112                 */
2113                if (!(bp->b_flags & _XBF_DELWRI_Q)) {
2114                        list_del_init(&bp->b_list);
2115                        xfs_buf_relse(bp);
2116                        continue;
2117                }
2118
2119                trace_xfs_buf_delwri_split(bp, _RET_IP_);
2120
2121                /*
2122                 * If we have a wait list, each buffer (and associated delwri
2123                 * queue reference) transfers to it and is submitted
2124                 * synchronously. Otherwise, drop the buffer from the delwri
2125                 * queue and submit async.
2126                 */
2127                bp->b_flags &= ~_XBF_DELWRI_Q;
2128                bp->b_flags |= XBF_WRITE;
2129                if (wait_list) {
2130                        bp->b_flags &= ~XBF_ASYNC;
2131                        list_move_tail(&bp->b_list, wait_list);
2132                } else {
2133                        bp->b_flags |= XBF_ASYNC;
2134                        list_del_init(&bp->b_list);
2135                }
2136                __xfs_buf_submit(bp, false);
2137        }
2138        blk_finish_plug(&plug);
2139
2140        return pinned;
2141}
2142
2143/*
2144 * Write out a buffer list asynchronously.
2145 *
2146 * This will take the @buffer_list, write all non-locked and non-pinned buffers
2147 * out and not wait for I/O completion on any of the buffers.  This interface
2148 * is only safely useable for callers that can track I/O completion by higher
2149 * level means, e.g. AIL pushing as the @buffer_list is consumed in this
2150 * function.
2151 *
2152 * Note: this function will skip buffers it would block on, and in doing so
2153 * leaves them on @buffer_list so they can be retried on a later pass. As such,
2154 * it is up to the caller to ensure that the buffer list is fully submitted or
2155 * cancelled appropriately when they are finished with the list. Failure to
2156 * cancel or resubmit the list until it is empty will result in leaked buffers
2157 * at unmount time.
2158 */
2159int
2160xfs_buf_delwri_submit_nowait(
2161        struct list_head        *buffer_list)
2162{
2163        return xfs_buf_delwri_submit_buffers(buffer_list, NULL);
2164}
2165
2166/*
2167 * Write out a buffer list synchronously.
2168 *
2169 * This will take the @buffer_list, write all buffers out and wait for I/O
2170 * completion on all of the buffers. @buffer_list is consumed by the function,
2171 * so callers must have some other way of tracking buffers if they require such
2172 * functionality.
2173 */
2174int
2175xfs_buf_delwri_submit(
2176        struct list_head        *buffer_list)
2177{
2178        LIST_HEAD               (wait_list);
2179        int                     error = 0, error2;
2180        struct xfs_buf          *bp;
2181
2182        xfs_buf_delwri_submit_buffers(buffer_list, &wait_list);
2183
2184        /* Wait for IO to complete. */
2185        while (!list_empty(&wait_list)) {
2186                bp = list_first_entry(&wait_list, struct xfs_buf, b_list);
2187
2188                list_del_init(&bp->b_list);
2189
2190                /*
2191                 * Wait on the locked buffer, check for errors and unlock and
2192                 * release the delwri queue reference.
2193                 */
2194                error2 = xfs_buf_iowait(bp);
2195                xfs_buf_relse(bp);
2196                if (!error)
2197                        error = error2;
2198        }
2199
2200        return error;
2201}
2202
2203/*
2204 * Push a single buffer on a delwri queue.
2205 *
2206 * The purpose of this function is to submit a single buffer of a delwri queue
2207 * and return with the buffer still on the original queue. The waiting delwri
2208 * buffer submission infrastructure guarantees transfer of the delwri queue
2209 * buffer reference to a temporary wait list. We reuse this infrastructure to
2210 * transfer the buffer back to the original queue.
2211 *
2212 * Note the buffer transitions from the queued state, to the submitted and wait
2213 * listed state and back to the queued state during this call. The buffer
2214 * locking and queue management logic between _delwri_pushbuf() and
2215 * _delwri_queue() guarantee that the buffer cannot be queued to another list
2216 * before returning.
2217 */
2218int
2219xfs_buf_delwri_pushbuf(
2220        struct xfs_buf          *bp,
2221        struct list_head        *buffer_list)
2222{
2223        LIST_HEAD               (submit_list);
2224        int                     error;
2225
2226        ASSERT(bp->b_flags & _XBF_DELWRI_Q);
2227
2228        trace_xfs_buf_delwri_pushbuf(bp, _RET_IP_);
2229
2230        /*
2231         * Isolate the buffer to a new local list so we can submit it for I/O
2232         * independently from the rest of the original list.
2233         */
2234        xfs_buf_lock(bp);
2235        list_move(&bp->b_list, &submit_list);
2236        xfs_buf_unlock(bp);
2237
2238        /*
2239         * Delwri submission clears the DELWRI_Q buffer flag and returns with
2240         * the buffer on the wait list with the original reference. Rather than
2241         * bounce the buffer from a local wait list back to the original list
2242         * after I/O completion, reuse the original list as the wait list.
2243         */
2244        xfs_buf_delwri_submit_buffers(&submit_list, buffer_list);
2245
2246        /*
2247         * The buffer is now locked, under I/O and wait listed on the original
2248         * delwri queue. Wait for I/O completion, restore the DELWRI_Q flag and
2249         * return with the buffer unlocked and on the original queue.
2250         */
2251        error = xfs_buf_iowait(bp);
2252        bp->b_flags |= _XBF_DELWRI_Q;
2253        xfs_buf_unlock(bp);
2254
2255        return error;
2256}
2257
2258int __init
2259xfs_buf_init(void)
2260{
2261        xfs_buf_cache = kmem_cache_create("xfs_buf", sizeof(struct xfs_buf), 0,
2262                                         SLAB_HWCACHE_ALIGN |
2263                                         SLAB_RECLAIM_ACCOUNT |
2264                                         SLAB_MEM_SPREAD,
2265                                         NULL);
2266        if (!xfs_buf_cache)
2267                goto out;
2268
2269        return 0;
2270
2271 out:
2272        return -ENOMEM;
2273}
2274
2275void
2276xfs_buf_terminate(void)
2277{
2278        kmem_cache_destroy(xfs_buf_cache);
2279}
2280
2281void xfs_buf_set_ref(struct xfs_buf *bp, int lru_ref)
2282{
2283        /*
2284         * Set the lru reference count to 0 based on the error injection tag.
2285         * This allows userspace to disrupt buffer caching for debug/testing
2286         * purposes.
2287         */
2288        if (XFS_TEST_ERROR(false, bp->b_mount, XFS_ERRTAG_BUF_LRU_REF))
2289                lru_ref = 0;
2290
2291        atomic_set(&bp->b_lru_ref, lru_ref);
2292}
2293
2294/*
2295 * Verify an on-disk magic value against the magic value specified in the
2296 * verifier structure. The verifier magic is in disk byte order so the caller is
2297 * expected to pass the value directly from disk.
2298 */
2299bool
2300xfs_verify_magic(
2301        struct xfs_buf          *bp,
2302        __be32                  dmagic)
2303{
2304        struct xfs_mount        *mp = bp->b_mount;
2305        int                     idx;
2306
2307        idx = xfs_has_crc(mp);
2308        if (WARN_ON(!bp->b_ops || !bp->b_ops->magic[idx]))
2309                return false;
2310        return dmagic == bp->b_ops->magic[idx];
2311}
2312/*
2313 * Verify an on-disk magic value against the magic value specified in the
2314 * verifier structure. The verifier magic is in disk byte order so the caller is
2315 * expected to pass the value directly from disk.
2316 */
2317bool
2318xfs_verify_magic16(
2319        struct xfs_buf          *bp,
2320        __be16                  dmagic)
2321{
2322        struct xfs_mount        *mp = bp->b_mount;
2323        int                     idx;
2324
2325        idx = xfs_has_crc(mp);
2326        if (WARN_ON(!bp->b_ops || !bp->b_ops->magic16[idx]))
2327                return false;
2328        return dmagic == bp->b_ops->magic16[idx];
2329}
2330