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#include <linux/dax.h>
   9
  10#include "xfs_shared.h"
  11#include "xfs_format.h"
  12#include "xfs_log_format.h"
  13#include "xfs_trans_resv.h"
  14#include "xfs_mount.h"
  15#include "xfs_trace.h"
  16#include "xfs_log.h"
  17#include "xfs_log_recover.h"
  18#include "xfs_log_priv.h"
  19#include "xfs_trans.h"
  20#include "xfs_buf_item.h"
  21#include "xfs_errortag.h"
  22#include "xfs_error.h"
  23#include "xfs_ag.h"
  24
  25struct kmem_cache *xfs_buf_cache;
  26
  27/*
  28 * Locking orders
  29 *
  30 * xfs_buf_ioacct_inc:
  31 * xfs_buf_ioacct_dec:
  32 *	b_sema (caller holds)
  33 *	  b_lock
  34 *
  35 * xfs_buf_stale:
  36 *	b_sema (caller holds)
  37 *	  b_lock
  38 *	    lru_lock
  39 *
  40 * xfs_buf_rele:
  41 *	b_lock
  42 *	  pag_buf_lock
  43 *	    lru_lock
  44 *
  45 * xfs_buftarg_drain_rele
  46 *	lru_lock
  47 *	  b_lock (trylock due to inversion)
  48 *
  49 * xfs_buftarg_isolate
  50 *	lru_lock
  51 *	  b_lock (trylock due to inversion)
  52 */
  53
  54static int __xfs_buf_submit(struct xfs_buf *bp, bool wait);
  55
  56static inline int
  57xfs_buf_submit(
  58	struct xfs_buf		*bp)
  59{
  60	return __xfs_buf_submit(bp, !(bp->b_flags & XBF_ASYNC));
  61}
  62
  63static inline int
  64xfs_buf_is_vmapped(
  65	struct xfs_buf	*bp)
  66{
  67	/*
  68	 * Return true if the buffer is vmapped.
  69	 *
  70	 * b_addr is null if the buffer is not mapped, but the code is clever
  71	 * enough to know it doesn't have to map a single page, so the check has
  72	 * to be both for b_addr and bp->b_page_count > 1.
  73	 */
  74	return bp->b_addr && bp->b_page_count > 1;
  75}
  76
  77static inline int
  78xfs_buf_vmap_len(
  79	struct xfs_buf	*bp)
  80{
  81	return (bp->b_page_count * PAGE_SIZE);
  82}
  83
  84/*
  85 * Bump the I/O in flight count on the buftarg if we haven't yet done so for
  86 * this buffer. The count is incremented once per buffer (per hold cycle)
  87 * because the corresponding decrement is deferred to buffer release. Buffers
  88 * can undergo I/O multiple times in a hold-release cycle and per buffer I/O
  89 * tracking adds unnecessary overhead. This is used for sychronization purposes
  90 * with unmount (see xfs_buftarg_drain()), so all we really need is a count of
  91 * in-flight buffers.
  92 *
  93 * Buffers that are never released (e.g., superblock, iclog buffers) must set
  94 * the XBF_NO_IOACCT flag before I/O submission. Otherwise, the buftarg count
  95 * never reaches zero and unmount hangs indefinitely.
  96 */
  97static inline void
  98xfs_buf_ioacct_inc(
  99	struct xfs_buf	*bp)
 100{
 101	if (bp->b_flags & XBF_NO_IOACCT)
 102		return;
 103
 104	ASSERT(bp->b_flags & XBF_ASYNC);
 105	spin_lock(&bp->b_lock);
 106	if (!(bp->b_state & XFS_BSTATE_IN_FLIGHT)) {
 107		bp->b_state |= XFS_BSTATE_IN_FLIGHT;
 108		percpu_counter_inc(&bp->b_target->bt_io_count);
 109	}
 110	spin_unlock(&bp->b_lock);
 111}
 112
 113/*
 114 * Clear the in-flight state on a buffer about to be released to the LRU or
 115 * freed and unaccount from the buftarg.
 116 */
 117static inline void
 118__xfs_buf_ioacct_dec(
 119	struct xfs_buf	*bp)
 120{
 121	lockdep_assert_held(&bp->b_lock);
 122
 123	if (bp->b_state & XFS_BSTATE_IN_FLIGHT) {
 124		bp->b_state &= ~XFS_BSTATE_IN_FLIGHT;
 125		percpu_counter_dec(&bp->b_target->bt_io_count);
 126	}
 127}
 128
 129static inline void
 130xfs_buf_ioacct_dec(
 131	struct xfs_buf	*bp)
 132{
 133	spin_lock(&bp->b_lock);
 134	__xfs_buf_ioacct_dec(bp);
 135	spin_unlock(&bp->b_lock);
 136}
 137
 138/*
 139 * When we mark a buffer stale, we remove the buffer from the LRU and clear the
 140 * b_lru_ref count so that the buffer is freed immediately when the buffer
 141 * reference count falls to zero. If the buffer is already on the LRU, we need
 142 * to remove the reference that LRU holds on the buffer.
 143 *
 144 * This prevents build-up of stale buffers on the LRU.
 145 */
 146void
 147xfs_buf_stale(
 148	struct xfs_buf	*bp)
 149{
 150	ASSERT(xfs_buf_islocked(bp));
 151
 152	bp->b_flags |= XBF_STALE;
 153
 154	/*
 155	 * Clear the delwri status so that a delwri queue walker will not
 156	 * flush this buffer to disk now that it is stale. The delwri queue has
 157	 * a reference to the buffer, so this is safe to do.
 158	 */
 159	bp->b_flags &= ~_XBF_DELWRI_Q;
 160
 161	/*
 162	 * Once the buffer is marked stale and unlocked, a subsequent lookup
 163	 * could reset b_flags. There is no guarantee that the buffer is
 164	 * unaccounted (released to LRU) before that occurs. Drop in-flight
 165	 * status now to preserve accounting consistency.
 166	 */
 167	spin_lock(&bp->b_lock);
 168	__xfs_buf_ioacct_dec(bp);
 169
 170	atomic_set(&bp->b_lru_ref, 0);
 171	if (!(bp->b_state & XFS_BSTATE_DISPOSE) &&
 172	    (list_lru_del_obj(&bp->b_target->bt_lru, &bp->b_lru)))
 173		atomic_dec(&bp->b_hold);
 174
 175	ASSERT(atomic_read(&bp->b_hold) >= 1);
 176	spin_unlock(&bp->b_lock);
 177}
 178
 179static int
 180xfs_buf_get_maps(
 181	struct xfs_buf		*bp,
 182	int			map_count)
 183{
 184	ASSERT(bp->b_maps == NULL);
 185	bp->b_map_count = map_count;
 186
 187	if (map_count == 1) {
 188		bp->b_maps = &bp->__b_map;
 189		return 0;
 190	}
 191
 192	bp->b_maps = kmem_zalloc(map_count * sizeof(struct xfs_buf_map),
 193				KM_NOFS);
 194	if (!bp->b_maps)
 195		return -ENOMEM;
 196	return 0;
 197}
 198
 199/*
 200 *	Frees b_pages if it was allocated.
 201 */
 202static void
 203xfs_buf_free_maps(
 204	struct xfs_buf	*bp)
 205{
 206	if (bp->b_maps != &bp->__b_map) {
 207		kmem_free(bp->b_maps);
 208		bp->b_maps = NULL;
 209	}
 210}
 211
 212static int
 213_xfs_buf_alloc(
 214	struct xfs_buftarg	*target,
 215	struct xfs_buf_map	*map,
 216	int			nmaps,
 217	xfs_buf_flags_t		flags,
 218	struct xfs_buf		**bpp)
 219{
 220	struct xfs_buf		*bp;
 221	int			error;
 222	int			i;
 223
 224	*bpp = NULL;
 225	bp = kmem_cache_zalloc(xfs_buf_cache, GFP_NOFS | __GFP_NOFAIL);
 226
 227	/*
 228	 * We don't want certain flags to appear in b_flags unless they are
 229	 * specifically set by later operations on the buffer.
 230	 */
 231	flags &= ~(XBF_UNMAPPED | XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD);
 232
 233	atomic_set(&bp->b_hold, 1);
 234	atomic_set(&bp->b_lru_ref, 1);
 235	init_completion(&bp->b_iowait);
 236	INIT_LIST_HEAD(&bp->b_lru);
 237	INIT_LIST_HEAD(&bp->b_list);
 238	INIT_LIST_HEAD(&bp->b_li_list);
 239	sema_init(&bp->b_sema, 0); /* held, no waiters */
 240	spin_lock_init(&bp->b_lock);
 241	bp->b_target = target;
 242	bp->b_mount = target->bt_mount;
 243	bp->b_flags = flags;
 244
 245	/*
 246	 * Set length and io_length to the same value initially.
 247	 * I/O routines should use io_length, which will be the same in
 248	 * most cases but may be reset (e.g. XFS recovery).
 249	 */
 250	error = xfs_buf_get_maps(bp, nmaps);
 251	if (error)  {
 252		kmem_cache_free(xfs_buf_cache, bp);
 253		return error;
 254	}
 255
 256	bp->b_rhash_key = map[0].bm_bn;
 257	bp->b_length = 0;
 258	for (i = 0; i < nmaps; i++) {
 259		bp->b_maps[i].bm_bn = map[i].bm_bn;
 260		bp->b_maps[i].bm_len = map[i].bm_len;
 261		bp->b_length += map[i].bm_len;
 262	}
 263
 264	atomic_set(&bp->b_pin_count, 0);
 265	init_waitqueue_head(&bp->b_waiters);
 266
 267	XFS_STATS_INC(bp->b_mount, xb_create);
 268	trace_xfs_buf_init(bp, _RET_IP_);
 269
 270	*bpp = bp;
 271	return 0;
 272}
 273
 274static void
 275xfs_buf_free_pages(
 276	struct xfs_buf	*bp)
 277{
 278	uint		i;
 279
 280	ASSERT(bp->b_flags & _XBF_PAGES);
 281
 282	if (xfs_buf_is_vmapped(bp))
 283		vm_unmap_ram(bp->b_addr, bp->b_page_count);
 284
 285	for (i = 0; i < bp->b_page_count; i++) {
 286		if (bp->b_pages[i])
 287			__free_page(bp->b_pages[i]);
 288	}
 289	mm_account_reclaimed_pages(bp->b_page_count);
 
 290
 291	if (bp->b_pages != bp->b_page_array)
 292		kmem_free(bp->b_pages);
 293	bp->b_pages = NULL;
 294	bp->b_flags &= ~_XBF_PAGES;
 295}
 296
 297static void
 298xfs_buf_free_callback(
 299	struct callback_head	*cb)
 300{
 301	struct xfs_buf		*bp = container_of(cb, struct xfs_buf, b_rcu);
 302
 303	xfs_buf_free_maps(bp);
 304	kmem_cache_free(xfs_buf_cache, bp);
 305}
 306
 307static void
 308xfs_buf_free(
 309	struct xfs_buf		*bp)
 310{
 311	trace_xfs_buf_free(bp, _RET_IP_);
 312
 313	ASSERT(list_empty(&bp->b_lru));
 314
 315	if (bp->b_flags & _XBF_PAGES)
 316		xfs_buf_free_pages(bp);
 317	else if (bp->b_flags & _XBF_KMEM)
 318		kmem_free(bp->b_addr);
 319
 320	call_rcu(&bp->b_rcu, xfs_buf_free_callback);
 321}
 322
 323static int
 324xfs_buf_alloc_kmem(
 325	struct xfs_buf	*bp,
 326	xfs_buf_flags_t	flags)
 327{
 328	xfs_km_flags_t	kmflag_mask = KM_NOFS;
 329	size_t		size = BBTOB(bp->b_length);
 330
 331	/* Assure zeroed buffer for non-read cases. */
 332	if (!(flags & XBF_READ))
 333		kmflag_mask |= KM_ZERO;
 334
 335	bp->b_addr = kmem_alloc(size, kmflag_mask);
 336	if (!bp->b_addr)
 337		return -ENOMEM;
 338
 339	if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
 340	    ((unsigned long)bp->b_addr & PAGE_MASK)) {
 341		/* b_addr spans two pages - use alloc_page instead */
 342		kmem_free(bp->b_addr);
 343		bp->b_addr = NULL;
 344		return -ENOMEM;
 345	}
 346	bp->b_offset = offset_in_page(bp->b_addr);
 347	bp->b_pages = bp->b_page_array;
 348	bp->b_pages[0] = kmem_to_page(bp->b_addr);
 349	bp->b_page_count = 1;
 350	bp->b_flags |= _XBF_KMEM;
 351	return 0;
 352}
 353
 354static int
 355xfs_buf_alloc_pages(
 356	struct xfs_buf	*bp,
 357	xfs_buf_flags_t	flags)
 358{
 359	gfp_t		gfp_mask = __GFP_NOWARN;
 360	long		filled = 0;
 361
 362	if (flags & XBF_READ_AHEAD)
 363		gfp_mask |= __GFP_NORETRY;
 364	else
 365		gfp_mask |= GFP_NOFS;
 366
 367	/* Make sure that we have a page list */
 368	bp->b_page_count = DIV_ROUND_UP(BBTOB(bp->b_length), PAGE_SIZE);
 369	if (bp->b_page_count <= XB_PAGES) {
 370		bp->b_pages = bp->b_page_array;
 371	} else {
 372		bp->b_pages = kzalloc(sizeof(struct page *) * bp->b_page_count,
 373					gfp_mask);
 374		if (!bp->b_pages)
 375			return -ENOMEM;
 376	}
 377	bp->b_flags |= _XBF_PAGES;
 378
 379	/* Assure zeroed buffer for non-read cases. */
 380	if (!(flags & XBF_READ))
 381		gfp_mask |= __GFP_ZERO;
 382
 383	/*
 384	 * Bulk filling of pages can take multiple calls. Not filling the entire
 385	 * array is not an allocation failure, so don't back off if we get at
 386	 * least one extra page.
 387	 */
 388	for (;;) {
 389		long	last = filled;
 390
 391		filled = alloc_pages_bulk_array(gfp_mask, bp->b_page_count,
 392						bp->b_pages);
 393		if (filled == bp->b_page_count) {
 394			XFS_STATS_INC(bp->b_mount, xb_page_found);
 395			break;
 396		}
 397
 398		if (filled != last)
 399			continue;
 400
 401		if (flags & XBF_READ_AHEAD) {
 402			xfs_buf_free_pages(bp);
 403			return -ENOMEM;
 404		}
 405
 406		XFS_STATS_INC(bp->b_mount, xb_page_retries);
 407		memalloc_retry_wait(gfp_mask);
 408	}
 409	return 0;
 410}
 411
 412/*
 413 *	Map buffer into kernel address-space if necessary.
 414 */
 415STATIC int
 416_xfs_buf_map_pages(
 417	struct xfs_buf		*bp,
 418	xfs_buf_flags_t		flags)
 419{
 420	ASSERT(bp->b_flags & _XBF_PAGES);
 421	if (bp->b_page_count == 1) {
 422		/* A single page buffer is always mappable */
 423		bp->b_addr = page_address(bp->b_pages[0]);
 424	} else if (flags & XBF_UNMAPPED) {
 425		bp->b_addr = NULL;
 426	} else {
 427		int retried = 0;
 428		unsigned nofs_flag;
 429
 430		/*
 431		 * vm_map_ram() will allocate auxiliary structures (e.g.
 432		 * pagetables) with GFP_KERNEL, yet we are likely to be under
 433		 * GFP_NOFS context here. Hence we need to tell memory reclaim
 434		 * that we are in such a context via PF_MEMALLOC_NOFS to prevent
 435		 * memory reclaim re-entering the filesystem here and
 436		 * potentially deadlocking.
 437		 */
 438		nofs_flag = memalloc_nofs_save();
 439		do {
 440			bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
 441						-1);
 442			if (bp->b_addr)
 443				break;
 444			vm_unmap_aliases();
 445		} while (retried++ <= 1);
 446		memalloc_nofs_restore(nofs_flag);
 447
 448		if (!bp->b_addr)
 449			return -ENOMEM;
 450	}
 451
 452	return 0;
 453}
 454
 455/*
 456 *	Finding and Reading Buffers
 457 */
 458static int
 459_xfs_buf_obj_cmp(
 460	struct rhashtable_compare_arg	*arg,
 461	const void			*obj)
 462{
 463	const struct xfs_buf_map	*map = arg->key;
 464	const struct xfs_buf		*bp = obj;
 465
 466	/*
 467	 * The key hashing in the lookup path depends on the key being the
 468	 * first element of the compare_arg, make sure to assert this.
 469	 */
 470	BUILD_BUG_ON(offsetof(struct xfs_buf_map, bm_bn) != 0);
 471
 472	if (bp->b_rhash_key != map->bm_bn)
 473		return 1;
 474
 475	if (unlikely(bp->b_length != map->bm_len)) {
 476		/*
 477		 * found a block number match. If the range doesn't
 478		 * match, the only way this is allowed is if the buffer
 479		 * in the cache is stale and the transaction that made
 480		 * it stale has not yet committed. i.e. we are
 481		 * reallocating a busy extent. Skip this buffer and
 482		 * continue searching for an exact match.
 483		 */
 484		if (!(map->bm_flags & XBM_LIVESCAN))
 485			ASSERT(bp->b_flags & XBF_STALE);
 486		return 1;
 487	}
 488	return 0;
 489}
 490
 491static const struct rhashtable_params xfs_buf_hash_params = {
 492	.min_size		= 32,	/* empty AGs have minimal footprint */
 493	.nelem_hint		= 16,
 494	.key_len		= sizeof(xfs_daddr_t),
 495	.key_offset		= offsetof(struct xfs_buf, b_rhash_key),
 496	.head_offset		= offsetof(struct xfs_buf, b_rhash_head),
 497	.automatic_shrinking	= true,
 498	.obj_cmpfn		= _xfs_buf_obj_cmp,
 499};
 500
 501int
 502xfs_buf_hash_init(
 503	struct xfs_perag	*pag)
 504{
 505	spin_lock_init(&pag->pag_buf_lock);
 506	return rhashtable_init(&pag->pag_buf_hash, &xfs_buf_hash_params);
 507}
 508
 509void
 510xfs_buf_hash_destroy(
 511	struct xfs_perag	*pag)
 512{
 513	rhashtable_destroy(&pag->pag_buf_hash);
 514}
 515
 516static int
 517xfs_buf_map_verify(
 518	struct xfs_buftarg	*btp,
 519	struct xfs_buf_map	*map)
 520{
 521	xfs_daddr_t		eofs;
 522
 523	/* Check for IOs smaller than the sector size / not sector aligned */
 524	ASSERT(!(BBTOB(map->bm_len) < btp->bt_meta_sectorsize));
 525	ASSERT(!(BBTOB(map->bm_bn) & (xfs_off_t)btp->bt_meta_sectormask));
 526
 527	/*
 528	 * Corrupted block numbers can get through to here, unfortunately, so we
 529	 * have to check that the buffer falls within the filesystem bounds.
 530	 */
 531	eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
 532	if (map->bm_bn < 0 || map->bm_bn >= eofs) {
 533		xfs_alert(btp->bt_mount,
 534			  "%s: daddr 0x%llx out of range, EOFS 0x%llx",
 535			  __func__, map->bm_bn, eofs);
 536		WARN_ON(1);
 537		return -EFSCORRUPTED;
 538	}
 539	return 0;
 540}
 541
 542static int
 543xfs_buf_find_lock(
 544	struct xfs_buf          *bp,
 545	xfs_buf_flags_t		flags)
 546{
 547	if (flags & XBF_TRYLOCK) {
 548		if (!xfs_buf_trylock(bp)) {
 549			XFS_STATS_INC(bp->b_mount, xb_busy_locked);
 550			return -EAGAIN;
 551		}
 552	} else {
 553		xfs_buf_lock(bp);
 554		XFS_STATS_INC(bp->b_mount, xb_get_locked_waited);
 555	}
 556
 557	/*
 558	 * if the buffer is stale, clear all the external state associated with
 559	 * it. We need to keep flags such as how we allocated the buffer memory
 560	 * intact here.
 561	 */
 562	if (bp->b_flags & XBF_STALE) {
 563		if (flags & XBF_LIVESCAN) {
 564			xfs_buf_unlock(bp);
 565			return -ENOENT;
 566		}
 567		ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
 568		bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
 569		bp->b_ops = NULL;
 570	}
 571	return 0;
 572}
 573
 574static inline int
 575xfs_buf_lookup(
 576	struct xfs_perag	*pag,
 577	struct xfs_buf_map	*map,
 578	xfs_buf_flags_t		flags,
 579	struct xfs_buf		**bpp)
 580{
 581	struct xfs_buf          *bp;
 582	int			error;
 583
 584	rcu_read_lock();
 585	bp = rhashtable_lookup(&pag->pag_buf_hash, map, xfs_buf_hash_params);
 586	if (!bp || !atomic_inc_not_zero(&bp->b_hold)) {
 587		rcu_read_unlock();
 588		return -ENOENT;
 589	}
 590	rcu_read_unlock();
 591
 592	error = xfs_buf_find_lock(bp, flags);
 593	if (error) {
 594		xfs_buf_rele(bp);
 595		return error;
 596	}
 597
 598	trace_xfs_buf_find(bp, flags, _RET_IP_);
 599	*bpp = bp;
 600	return 0;
 601}
 602
 603/*
 604 * Insert the new_bp into the hash table. This consumes the perag reference
 605 * taken for the lookup regardless of the result of the insert.
 606 */
 607static int
 608xfs_buf_find_insert(
 609	struct xfs_buftarg	*btp,
 610	struct xfs_perag	*pag,
 611	struct xfs_buf_map	*cmap,
 612	struct xfs_buf_map	*map,
 613	int			nmaps,
 614	xfs_buf_flags_t		flags,
 615	struct xfs_buf		**bpp)
 616{
 617	struct xfs_buf		*new_bp;
 618	struct xfs_buf		*bp;
 619	int			error;
 620
 621	error = _xfs_buf_alloc(btp, map, nmaps, flags, &new_bp);
 622	if (error)
 623		goto out_drop_pag;
 624
 625	/*
 626	 * For buffers that fit entirely within a single page, first attempt to
 627	 * allocate the memory from the heap to minimise memory usage. If we
 628	 * can't get heap memory for these small buffers, we fall back to using
 629	 * the page allocator.
 630	 */
 631	if (BBTOB(new_bp->b_length) >= PAGE_SIZE ||
 632	    xfs_buf_alloc_kmem(new_bp, flags) < 0) {
 633		error = xfs_buf_alloc_pages(new_bp, flags);
 634		if (error)
 635			goto out_free_buf;
 636	}
 637
 638	spin_lock(&pag->pag_buf_lock);
 639	bp = rhashtable_lookup_get_insert_fast(&pag->pag_buf_hash,
 640			&new_bp->b_rhash_head, xfs_buf_hash_params);
 641	if (IS_ERR(bp)) {
 642		error = PTR_ERR(bp);
 643		spin_unlock(&pag->pag_buf_lock);
 644		goto out_free_buf;
 645	}
 646	if (bp) {
 647		/* found an existing buffer */
 648		atomic_inc(&bp->b_hold);
 649		spin_unlock(&pag->pag_buf_lock);
 650		error = xfs_buf_find_lock(bp, flags);
 651		if (error)
 652			xfs_buf_rele(bp);
 653		else
 654			*bpp = bp;
 655		goto out_free_buf;
 656	}
 657
 658	/* The new buffer keeps the perag reference until it is freed. */
 659	new_bp->b_pag = pag;
 660	spin_unlock(&pag->pag_buf_lock);
 661	*bpp = new_bp;
 662	return 0;
 663
 664out_free_buf:
 665	xfs_buf_free(new_bp);
 666out_drop_pag:
 667	xfs_perag_put(pag);
 668	return error;
 669}
 670
 671/*
 672 * Assembles a buffer covering the specified range. The code is optimised for
 673 * cache hits, as metadata intensive workloads will see 3 orders of magnitude
 674 * more hits than misses.
 675 */
 676int
 677xfs_buf_get_map(
 678	struct xfs_buftarg	*btp,
 679	struct xfs_buf_map	*map,
 680	int			nmaps,
 681	xfs_buf_flags_t		flags,
 682	struct xfs_buf		**bpp)
 683{
 684	struct xfs_perag	*pag;
 685	struct xfs_buf		*bp = NULL;
 686	struct xfs_buf_map	cmap = { .bm_bn = map[0].bm_bn };
 687	int			error;
 688	int			i;
 689
 690	if (flags & XBF_LIVESCAN)
 691		cmap.bm_flags |= XBM_LIVESCAN;
 692	for (i = 0; i < nmaps; i++)
 693		cmap.bm_len += map[i].bm_len;
 694
 695	error = xfs_buf_map_verify(btp, &cmap);
 696	if (error)
 697		return error;
 698
 699	pag = xfs_perag_get(btp->bt_mount,
 700			    xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
 701
 702	error = xfs_buf_lookup(pag, &cmap, flags, &bp);
 703	if (error && error != -ENOENT)
 704		goto out_put_perag;
 705
 706	/* cache hits always outnumber misses by at least 10:1 */
 707	if (unlikely(!bp)) {
 708		XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
 709
 710		if (flags & XBF_INCORE)
 711			goto out_put_perag;
 712
 713		/* xfs_buf_find_insert() consumes the perag reference. */
 714		error = xfs_buf_find_insert(btp, pag, &cmap, map, nmaps,
 715				flags, &bp);
 716		if (error)
 717			return error;
 718	} else {
 719		XFS_STATS_INC(btp->bt_mount, xb_get_locked);
 720		xfs_perag_put(pag);
 721	}
 722
 723	/* We do not hold a perag reference anymore. */
 724	if (!bp->b_addr) {
 725		error = _xfs_buf_map_pages(bp, flags);
 726		if (unlikely(error)) {
 727			xfs_warn_ratelimited(btp->bt_mount,
 728				"%s: failed to map %u pages", __func__,
 729				bp->b_page_count);
 730			xfs_buf_relse(bp);
 731			return error;
 732		}
 733	}
 734
 735	/*
 736	 * Clear b_error if this is a lookup from a caller that doesn't expect
 737	 * valid data to be found in the buffer.
 738	 */
 739	if (!(flags & XBF_READ))
 740		xfs_buf_ioerror(bp, 0);
 741
 742	XFS_STATS_INC(btp->bt_mount, xb_get);
 743	trace_xfs_buf_get(bp, flags, _RET_IP_);
 744	*bpp = bp;
 745	return 0;
 746
 747out_put_perag:
 748	xfs_perag_put(pag);
 749	return error;
 750}
 751
 752int
 753_xfs_buf_read(
 754	struct xfs_buf		*bp,
 755	xfs_buf_flags_t		flags)
 756{
 757	ASSERT(!(flags & XBF_WRITE));
 758	ASSERT(bp->b_maps[0].bm_bn != XFS_BUF_DADDR_NULL);
 759
 760	bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD | XBF_DONE);
 761	bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
 762
 763	return xfs_buf_submit(bp);
 764}
 765
 766/*
 767 * Reverify a buffer found in cache without an attached ->b_ops.
 768 *
 769 * If the caller passed an ops structure and the buffer doesn't have ops
 770 * assigned, set the ops and use it to verify the contents. If verification
 771 * fails, clear XBF_DONE. We assume the buffer has no recorded errors and is
 772 * already in XBF_DONE state on entry.
 773 *
 774 * Under normal operations, every in-core buffer is verified on read I/O
 775 * completion. There are two scenarios that can lead to in-core buffers without
 776 * an assigned ->b_ops. The first is during log recovery of buffers on a V4
 777 * filesystem, though these buffers are purged at the end of recovery. The
 778 * other is online repair, which intentionally reads with a NULL buffer ops to
 779 * run several verifiers across an in-core buffer in order to establish buffer
 780 * type.  If repair can't establish that, the buffer will be left in memory
 781 * with NULL buffer ops.
 782 */
 783int
 784xfs_buf_reverify(
 785	struct xfs_buf		*bp,
 786	const struct xfs_buf_ops *ops)
 787{
 788	ASSERT(bp->b_flags & XBF_DONE);
 789	ASSERT(bp->b_error == 0);
 790
 791	if (!ops || bp->b_ops)
 792		return 0;
 793
 794	bp->b_ops = ops;
 795	bp->b_ops->verify_read(bp);
 796	if (bp->b_error)
 797		bp->b_flags &= ~XBF_DONE;
 798	return bp->b_error;
 799}
 800
 801int
 802xfs_buf_read_map(
 803	struct xfs_buftarg	*target,
 804	struct xfs_buf_map	*map,
 805	int			nmaps,
 806	xfs_buf_flags_t		flags,
 807	struct xfs_buf		**bpp,
 808	const struct xfs_buf_ops *ops,
 809	xfs_failaddr_t		fa)
 810{
 811	struct xfs_buf		*bp;
 812	int			error;
 813
 814	flags |= XBF_READ;
 815	*bpp = NULL;
 816
 817	error = xfs_buf_get_map(target, map, nmaps, flags, &bp);
 818	if (error)
 819		return error;
 820
 821	trace_xfs_buf_read(bp, flags, _RET_IP_);
 822
 823	if (!(bp->b_flags & XBF_DONE)) {
 824		/* Initiate the buffer read and wait. */
 825		XFS_STATS_INC(target->bt_mount, xb_get_read);
 826		bp->b_ops = ops;
 827		error = _xfs_buf_read(bp, flags);
 828
 829		/* Readahead iodone already dropped the buffer, so exit. */
 830		if (flags & XBF_ASYNC)
 831			return 0;
 832	} else {
 833		/* Buffer already read; all we need to do is check it. */
 834		error = xfs_buf_reverify(bp, ops);
 835
 836		/* Readahead already finished; drop the buffer and exit. */
 837		if (flags & XBF_ASYNC) {
 838			xfs_buf_relse(bp);
 839			return 0;
 840		}
 841
 842		/* We do not want read in the flags */
 843		bp->b_flags &= ~XBF_READ;
 844		ASSERT(bp->b_ops != NULL || ops == NULL);
 845	}
 846
 847	/*
 848	 * If we've had a read error, then the contents of the buffer are
 849	 * invalid and should not be used. To ensure that a followup read tries
 850	 * to pull the buffer from disk again, we clear the XBF_DONE flag and
 851	 * mark the buffer stale. This ensures that anyone who has a current
 852	 * reference to the buffer will interpret it's contents correctly and
 853	 * future cache lookups will also treat it as an empty, uninitialised
 854	 * buffer.
 855	 */
 856	if (error) {
 857		/*
 858		 * Check against log shutdown for error reporting because
 859		 * metadata writeback may require a read first and we need to
 860		 * report errors in metadata writeback until the log is shut
 861		 * down. High level transaction read functions already check
 862		 * against mount shutdown, anyway, so we only need to be
 863		 * concerned about low level IO interactions here.
 864		 */
 865		if (!xlog_is_shutdown(target->bt_mount->m_log))
 866			xfs_buf_ioerror_alert(bp, fa);
 867
 868		bp->b_flags &= ~XBF_DONE;
 869		xfs_buf_stale(bp);
 870		xfs_buf_relse(bp);
 871
 872		/* bad CRC means corrupted metadata */
 873		if (error == -EFSBADCRC)
 874			error = -EFSCORRUPTED;
 875		return error;
 876	}
 877
 878	*bpp = bp;
 879	return 0;
 880}
 881
 882/*
 883 *	If we are not low on memory then do the readahead in a deadlock
 884 *	safe manner.
 885 */
 886void
 887xfs_buf_readahead_map(
 888	struct xfs_buftarg	*target,
 889	struct xfs_buf_map	*map,
 890	int			nmaps,
 891	const struct xfs_buf_ops *ops)
 892{
 893	struct xfs_buf		*bp;
 894
 895	xfs_buf_read_map(target, map, nmaps,
 896		     XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD, &bp, ops,
 897		     __this_address);
 898}
 899
 900/*
 901 * Read an uncached buffer from disk. Allocates and returns a locked
 902 * buffer containing the disk contents or nothing. Uncached buffers always have
 903 * a cache index of XFS_BUF_DADDR_NULL so we can easily determine if the buffer
 904 * is cached or uncached during fault diagnosis.
 905 */
 906int
 907xfs_buf_read_uncached(
 908	struct xfs_buftarg	*target,
 909	xfs_daddr_t		daddr,
 910	size_t			numblks,
 911	xfs_buf_flags_t		flags,
 912	struct xfs_buf		**bpp,
 913	const struct xfs_buf_ops *ops)
 914{
 915	struct xfs_buf		*bp;
 916	int			error;
 917
 918	*bpp = NULL;
 919
 920	error = xfs_buf_get_uncached(target, numblks, flags, &bp);
 921	if (error)
 922		return error;
 923
 924	/* set up the buffer for a read IO */
 925	ASSERT(bp->b_map_count == 1);
 926	bp->b_rhash_key = XFS_BUF_DADDR_NULL;
 927	bp->b_maps[0].bm_bn = daddr;
 928	bp->b_flags |= XBF_READ;
 929	bp->b_ops = ops;
 930
 931	xfs_buf_submit(bp);
 932	if (bp->b_error) {
 933		error = bp->b_error;
 934		xfs_buf_relse(bp);
 935		return error;
 936	}
 937
 938	*bpp = bp;
 939	return 0;
 940}
 941
 942int
 943xfs_buf_get_uncached(
 944	struct xfs_buftarg	*target,
 945	size_t			numblks,
 946	xfs_buf_flags_t		flags,
 947	struct xfs_buf		**bpp)
 948{
 949	int			error;
 950	struct xfs_buf		*bp;
 951	DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
 952
 953	*bpp = NULL;
 954
 955	/* flags might contain irrelevant bits, pass only what we care about */
 956	error = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT, &bp);
 957	if (error)
 958		return error;
 959
 960	error = xfs_buf_alloc_pages(bp, flags);
 961	if (error)
 962		goto fail_free_buf;
 963
 964	error = _xfs_buf_map_pages(bp, 0);
 965	if (unlikely(error)) {
 966		xfs_warn(target->bt_mount,
 967			"%s: failed to map pages", __func__);
 968		goto fail_free_buf;
 969	}
 970
 971	trace_xfs_buf_get_uncached(bp, _RET_IP_);
 972	*bpp = bp;
 973	return 0;
 974
 975fail_free_buf:
 976	xfs_buf_free(bp);
 977	return error;
 978}
 979
 980/*
 981 *	Increment reference count on buffer, to hold the buffer concurrently
 982 *	with another thread which may release (free) the buffer asynchronously.
 983 *	Must hold the buffer already to call this function.
 984 */
 985void
 986xfs_buf_hold(
 987	struct xfs_buf		*bp)
 988{
 989	trace_xfs_buf_hold(bp, _RET_IP_);
 990	atomic_inc(&bp->b_hold);
 991}
 992
 993/*
 994 * Release a hold on the specified buffer. If the hold count is 1, the buffer is
 995 * placed on LRU or freed (depending on b_lru_ref).
 996 */
 997void
 998xfs_buf_rele(
 999	struct xfs_buf		*bp)
1000{
1001	struct xfs_perag	*pag = bp->b_pag;
1002	bool			release;
1003	bool			freebuf = false;
1004
1005	trace_xfs_buf_rele(bp, _RET_IP_);
1006
1007	if (!pag) {
1008		ASSERT(list_empty(&bp->b_lru));
1009		if (atomic_dec_and_test(&bp->b_hold)) {
1010			xfs_buf_ioacct_dec(bp);
1011			xfs_buf_free(bp);
1012		}
1013		return;
1014	}
1015
1016	ASSERT(atomic_read(&bp->b_hold) > 0);
1017
1018	/*
1019	 * We grab the b_lock here first to serialise racing xfs_buf_rele()
1020	 * calls. The pag_buf_lock being taken on the last reference only
1021	 * serialises against racing lookups in xfs_buf_find(). IOWs, the second
1022	 * to last reference we drop here is not serialised against the last
1023	 * reference until we take bp->b_lock. Hence if we don't grab b_lock
1024	 * first, the last "release" reference can win the race to the lock and
1025	 * free the buffer before the second-to-last reference is processed,
1026	 * leading to a use-after-free scenario.
1027	 */
1028	spin_lock(&bp->b_lock);
1029	release = atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock);
1030	if (!release) {
1031		/*
1032		 * Drop the in-flight state if the buffer is already on the LRU
1033		 * and it holds the only reference. This is racy because we
1034		 * haven't acquired the pag lock, but the use of _XBF_IN_FLIGHT
1035		 * ensures the decrement occurs only once per-buf.
1036		 */
1037		if ((atomic_read(&bp->b_hold) == 1) && !list_empty(&bp->b_lru))
1038			__xfs_buf_ioacct_dec(bp);
1039		goto out_unlock;
1040	}
1041
1042	/* the last reference has been dropped ... */
1043	__xfs_buf_ioacct_dec(bp);
1044	if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
1045		/*
1046		 * If the buffer is added to the LRU take a new reference to the
1047		 * buffer for the LRU and clear the (now stale) dispose list
1048		 * state flag
1049		 */
1050		if (list_lru_add_obj(&bp->b_target->bt_lru, &bp->b_lru)) {
1051			bp->b_state &= ~XFS_BSTATE_DISPOSE;
1052			atomic_inc(&bp->b_hold);
1053		}
1054		spin_unlock(&pag->pag_buf_lock);
1055	} else {
1056		/*
1057		 * most of the time buffers will already be removed from the
1058		 * LRU, so optimise that case by checking for the
1059		 * XFS_BSTATE_DISPOSE flag indicating the last list the buffer
1060		 * was on was the disposal list
1061		 */
1062		if (!(bp->b_state & XFS_BSTATE_DISPOSE)) {
1063			list_lru_del_obj(&bp->b_target->bt_lru, &bp->b_lru);
1064		} else {
1065			ASSERT(list_empty(&bp->b_lru));
1066		}
1067
1068		ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1069		rhashtable_remove_fast(&pag->pag_buf_hash, &bp->b_rhash_head,
1070				       xfs_buf_hash_params);
1071		spin_unlock(&pag->pag_buf_lock);
1072		xfs_perag_put(pag);
1073		freebuf = true;
1074	}
1075
1076out_unlock:
1077	spin_unlock(&bp->b_lock);
1078
1079	if (freebuf)
1080		xfs_buf_free(bp);
1081}
1082
1083
1084/*
1085 *	Lock a buffer object, if it is not already locked.
1086 *
1087 *	If we come across a stale, pinned, locked buffer, we know that we are
1088 *	being asked to lock a buffer that has been reallocated. Because it is
1089 *	pinned, we know that the log has not been pushed to disk and hence it
1090 *	will still be locked.  Rather than continuing to have trylock attempts
1091 *	fail until someone else pushes the log, push it ourselves before
1092 *	returning.  This means that the xfsaild will not get stuck trying
1093 *	to push on stale inode buffers.
1094 */
1095int
1096xfs_buf_trylock(
1097	struct xfs_buf		*bp)
1098{
1099	int			locked;
1100
1101	locked = down_trylock(&bp->b_sema) == 0;
1102	if (locked)
1103		trace_xfs_buf_trylock(bp, _RET_IP_);
1104	else
1105		trace_xfs_buf_trylock_fail(bp, _RET_IP_);
1106	return locked;
1107}
1108
1109/*
1110 *	Lock a buffer object.
1111 *
1112 *	If we come across a stale, pinned, locked buffer, we know that we
1113 *	are being asked to lock a buffer that has been reallocated. Because
1114 *	it is pinned, we know that the log has not been pushed to disk and
1115 *	hence it will still be locked. Rather than sleeping until someone
1116 *	else pushes the log, push it ourselves before trying to get the lock.
1117 */
1118void
1119xfs_buf_lock(
1120	struct xfs_buf		*bp)
1121{
1122	trace_xfs_buf_lock(bp, _RET_IP_);
1123
1124	if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
1125		xfs_log_force(bp->b_mount, 0);
1126	down(&bp->b_sema);
1127
1128	trace_xfs_buf_lock_done(bp, _RET_IP_);
1129}
1130
1131void
1132xfs_buf_unlock(
1133	struct xfs_buf		*bp)
1134{
1135	ASSERT(xfs_buf_islocked(bp));
1136
1137	up(&bp->b_sema);
1138	trace_xfs_buf_unlock(bp, _RET_IP_);
1139}
1140
1141STATIC void
1142xfs_buf_wait_unpin(
1143	struct xfs_buf		*bp)
1144{
1145	DECLARE_WAITQUEUE	(wait, current);
1146
1147	if (atomic_read(&bp->b_pin_count) == 0)
1148		return;
1149
1150	add_wait_queue(&bp->b_waiters, &wait);
1151	for (;;) {
1152		set_current_state(TASK_UNINTERRUPTIBLE);
1153		if (atomic_read(&bp->b_pin_count) == 0)
1154			break;
1155		io_schedule();
1156	}
1157	remove_wait_queue(&bp->b_waiters, &wait);
1158	set_current_state(TASK_RUNNING);
1159}
1160
1161static void
1162xfs_buf_ioerror_alert_ratelimited(
1163	struct xfs_buf		*bp)
1164{
1165	static unsigned long	lasttime;
1166	static struct xfs_buftarg *lasttarg;
1167
1168	if (bp->b_target != lasttarg ||
1169	    time_after(jiffies, (lasttime + 5*HZ))) {
1170		lasttime = jiffies;
1171		xfs_buf_ioerror_alert(bp, __this_address);
1172	}
1173	lasttarg = bp->b_target;
1174}
1175
1176/*
1177 * Account for this latest trip around the retry handler, and decide if
1178 * we've failed enough times to constitute a permanent failure.
1179 */
1180static bool
1181xfs_buf_ioerror_permanent(
1182	struct xfs_buf		*bp,
1183	struct xfs_error_cfg	*cfg)
1184{
1185	struct xfs_mount	*mp = bp->b_mount;
1186
1187	if (cfg->max_retries != XFS_ERR_RETRY_FOREVER &&
1188	    ++bp->b_retries > cfg->max_retries)
1189		return true;
1190	if (cfg->retry_timeout != XFS_ERR_RETRY_FOREVER &&
1191	    time_after(jiffies, cfg->retry_timeout + bp->b_first_retry_time))
1192		return true;
1193
1194	/* At unmount we may treat errors differently */
1195	if (xfs_is_unmounting(mp) && mp->m_fail_unmount)
1196		return true;
1197
1198	return false;
1199}
1200
1201/*
1202 * On a sync write or shutdown we just want to stale the buffer and let the
1203 * caller handle the error in bp->b_error appropriately.
1204 *
1205 * If the write was asynchronous then no one will be looking for the error.  If
1206 * this is the first failure of this type, clear the error state and write the
1207 * buffer out again. This means we always retry an async write failure at least
1208 * once, but we also need to set the buffer up to behave correctly now for
1209 * repeated failures.
1210 *
1211 * If we get repeated async write failures, then we take action according to the
1212 * error configuration we have been set up to use.
1213 *
1214 * Returns true if this function took care of error handling and the caller must
1215 * not touch the buffer again.  Return false if the caller should proceed with
1216 * normal I/O completion handling.
1217 */
1218static bool
1219xfs_buf_ioend_handle_error(
1220	struct xfs_buf		*bp)
1221{
1222	struct xfs_mount	*mp = bp->b_mount;
1223	struct xfs_error_cfg	*cfg;
1224
1225	/*
1226	 * If we've already shutdown the journal because of I/O errors, there's
1227	 * no point in giving this a retry.
1228	 */
1229	if (xlog_is_shutdown(mp->m_log))
1230		goto out_stale;
1231
1232	xfs_buf_ioerror_alert_ratelimited(bp);
1233
1234	/*
1235	 * We're not going to bother about retrying this during recovery.
1236	 * One strike!
1237	 */
1238	if (bp->b_flags & _XBF_LOGRECOVERY) {
1239		xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR);
1240		return false;
1241	}
1242
1243	/*
1244	 * Synchronous writes will have callers process the error.
1245	 */
1246	if (!(bp->b_flags & XBF_ASYNC))
1247		goto out_stale;
1248
1249	trace_xfs_buf_iodone_async(bp, _RET_IP_);
1250
1251	cfg = xfs_error_get_cfg(mp, XFS_ERR_METADATA, bp->b_error);
1252	if (bp->b_last_error != bp->b_error ||
1253	    !(bp->b_flags & (XBF_STALE | XBF_WRITE_FAIL))) {
1254		bp->b_last_error = bp->b_error;
1255		if (cfg->retry_timeout != XFS_ERR_RETRY_FOREVER &&
1256		    !bp->b_first_retry_time)
1257			bp->b_first_retry_time = jiffies;
1258		goto resubmit;
1259	}
1260
1261	/*
1262	 * Permanent error - we need to trigger a shutdown if we haven't already
1263	 * to indicate that inconsistency will result from this action.
1264	 */
1265	if (xfs_buf_ioerror_permanent(bp, cfg)) {
1266		xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR);
1267		goto out_stale;
1268	}
1269
1270	/* Still considered a transient error. Caller will schedule retries. */
1271	if (bp->b_flags & _XBF_INODES)
1272		xfs_buf_inode_io_fail(bp);
1273	else if (bp->b_flags & _XBF_DQUOTS)
1274		xfs_buf_dquot_io_fail(bp);
1275	else
1276		ASSERT(list_empty(&bp->b_li_list));
1277	xfs_buf_ioerror(bp, 0);
1278	xfs_buf_relse(bp);
1279	return true;
1280
1281resubmit:
1282	xfs_buf_ioerror(bp, 0);
1283	bp->b_flags |= (XBF_DONE | XBF_WRITE_FAIL);
1284	xfs_buf_submit(bp);
1285	return true;
1286out_stale:
1287	xfs_buf_stale(bp);
1288	bp->b_flags |= XBF_DONE;
1289	bp->b_flags &= ~XBF_WRITE;
1290	trace_xfs_buf_error_relse(bp, _RET_IP_);
1291	return false;
1292}
1293
1294static void
1295xfs_buf_ioend(
1296	struct xfs_buf	*bp)
1297{
1298	trace_xfs_buf_iodone(bp, _RET_IP_);
1299
1300	/*
1301	 * Pull in IO completion errors now. We are guaranteed to be running
1302	 * single threaded, so we don't need the lock to read b_io_error.
1303	 */
1304	if (!bp->b_error && bp->b_io_error)
1305		xfs_buf_ioerror(bp, bp->b_io_error);
1306
1307	if (bp->b_flags & XBF_READ) {
1308		if (!bp->b_error && bp->b_ops)
1309			bp->b_ops->verify_read(bp);
1310		if (!bp->b_error)
1311			bp->b_flags |= XBF_DONE;
1312	} else {
1313		if (!bp->b_error) {
1314			bp->b_flags &= ~XBF_WRITE_FAIL;
1315			bp->b_flags |= XBF_DONE;
1316		}
1317
1318		if (unlikely(bp->b_error) && xfs_buf_ioend_handle_error(bp))
1319			return;
1320
1321		/* clear the retry state */
1322		bp->b_last_error = 0;
1323		bp->b_retries = 0;
1324		bp->b_first_retry_time = 0;
1325
1326		/*
1327		 * Note that for things like remote attribute buffers, there may
1328		 * not be a buffer log item here, so processing the buffer log
1329		 * item must remain optional.
1330		 */
1331		if (bp->b_log_item)
1332			xfs_buf_item_done(bp);
1333
1334		if (bp->b_flags & _XBF_INODES)
1335			xfs_buf_inode_iodone(bp);
1336		else if (bp->b_flags & _XBF_DQUOTS)
1337			xfs_buf_dquot_iodone(bp);
1338
1339	}
1340
1341	bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD |
1342			 _XBF_LOGRECOVERY);
1343
1344	if (bp->b_flags & XBF_ASYNC)
1345		xfs_buf_relse(bp);
1346	else
1347		complete(&bp->b_iowait);
1348}
1349
1350static void
1351xfs_buf_ioend_work(
1352	struct work_struct	*work)
1353{
1354	struct xfs_buf		*bp =
1355		container_of(work, struct xfs_buf, b_ioend_work);
1356
1357	xfs_buf_ioend(bp);
1358}
1359
1360static void
1361xfs_buf_ioend_async(
1362	struct xfs_buf	*bp)
1363{
1364	INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work);
1365	queue_work(bp->b_mount->m_buf_workqueue, &bp->b_ioend_work);
1366}
1367
1368void
1369__xfs_buf_ioerror(
1370	struct xfs_buf		*bp,
1371	int			error,
1372	xfs_failaddr_t		failaddr)
1373{
1374	ASSERT(error <= 0 && error >= -1000);
1375	bp->b_error = error;
1376	trace_xfs_buf_ioerror(bp, error, failaddr);
1377}
1378
1379void
1380xfs_buf_ioerror_alert(
1381	struct xfs_buf		*bp,
1382	xfs_failaddr_t		func)
1383{
1384	xfs_buf_alert_ratelimited(bp, "XFS: metadata IO error",
1385		"metadata I/O error in \"%pS\" at daddr 0x%llx len %d error %d",
1386				  func, (uint64_t)xfs_buf_daddr(bp),
1387				  bp->b_length, -bp->b_error);
1388}
1389
1390/*
1391 * To simulate an I/O failure, the buffer must be locked and held with at least
1392 * three references. The LRU reference is dropped by the stale call. The buf
1393 * item reference is dropped via ioend processing. The third reference is owned
1394 * by the caller and is dropped on I/O completion if the buffer is XBF_ASYNC.
1395 */
1396void
1397xfs_buf_ioend_fail(
1398	struct xfs_buf	*bp)
1399{
1400	bp->b_flags &= ~XBF_DONE;
1401	xfs_buf_stale(bp);
1402	xfs_buf_ioerror(bp, -EIO);
1403	xfs_buf_ioend(bp);
1404}
1405
1406int
1407xfs_bwrite(
1408	struct xfs_buf		*bp)
1409{
1410	int			error;
1411
1412	ASSERT(xfs_buf_islocked(bp));
1413
1414	bp->b_flags |= XBF_WRITE;
1415	bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q |
1416			 XBF_DONE);
1417
1418	error = xfs_buf_submit(bp);
1419	if (error)
1420		xfs_force_shutdown(bp->b_mount, SHUTDOWN_META_IO_ERROR);
1421	return error;
1422}
1423
1424static void
1425xfs_buf_bio_end_io(
1426	struct bio		*bio)
1427{
1428	struct xfs_buf		*bp = (struct xfs_buf *)bio->bi_private;
1429
1430	if (!bio->bi_status &&
1431	    (bp->b_flags & XBF_WRITE) && (bp->b_flags & XBF_ASYNC) &&
1432	    XFS_TEST_ERROR(false, bp->b_mount, XFS_ERRTAG_BUF_IOERROR))
1433		bio->bi_status = BLK_STS_IOERR;
1434
1435	/*
1436	 * don't overwrite existing errors - otherwise we can lose errors on
1437	 * buffers that require multiple bios to complete.
1438	 */
1439	if (bio->bi_status) {
1440		int error = blk_status_to_errno(bio->bi_status);
1441
1442		cmpxchg(&bp->b_io_error, 0, error);
1443	}
1444
1445	if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
1446		invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
1447
1448	if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
1449		xfs_buf_ioend_async(bp);
1450	bio_put(bio);
1451}
1452
1453static void
1454xfs_buf_ioapply_map(
1455	struct xfs_buf	*bp,
1456	int		map,
1457	int		*buf_offset,
1458	int		*count,
1459	blk_opf_t	op)
1460{
1461	int		page_index;
1462	unsigned int	total_nr_pages = bp->b_page_count;
1463	int		nr_pages;
1464	struct bio	*bio;
1465	sector_t	sector =  bp->b_maps[map].bm_bn;
1466	int		size;
1467	int		offset;
1468
1469	/* skip the pages in the buffer before the start offset */
1470	page_index = 0;
1471	offset = *buf_offset;
1472	while (offset >= PAGE_SIZE) {
1473		page_index++;
1474		offset -= PAGE_SIZE;
1475	}
1476
1477	/*
1478	 * Limit the IO size to the length of the current vector, and update the
1479	 * remaining IO count for the next time around.
1480	 */
1481	size = min_t(int, BBTOB(bp->b_maps[map].bm_len), *count);
1482	*count -= size;
1483	*buf_offset += size;
1484
1485next_chunk:
1486	atomic_inc(&bp->b_io_remaining);
1487	nr_pages = bio_max_segs(total_nr_pages);
1488
1489	bio = bio_alloc(bp->b_target->bt_bdev, nr_pages, op, GFP_NOIO);
1490	bio->bi_iter.bi_sector = sector;
1491	bio->bi_end_io = xfs_buf_bio_end_io;
1492	bio->bi_private = bp;
1493
1494	for (; size && nr_pages; nr_pages--, page_index++) {
1495		int	rbytes, nbytes = PAGE_SIZE - offset;
1496
1497		if (nbytes > size)
1498			nbytes = size;
1499
1500		rbytes = bio_add_page(bio, bp->b_pages[page_index], nbytes,
1501				      offset);
1502		if (rbytes < nbytes)
1503			break;
1504
1505		offset = 0;
1506		sector += BTOBB(nbytes);
1507		size -= nbytes;
1508		total_nr_pages--;
1509	}
1510
1511	if (likely(bio->bi_iter.bi_size)) {
1512		if (xfs_buf_is_vmapped(bp)) {
1513			flush_kernel_vmap_range(bp->b_addr,
1514						xfs_buf_vmap_len(bp));
1515		}
1516		submit_bio(bio);
1517		if (size)
1518			goto next_chunk;
1519	} else {
1520		/*
1521		 * This is guaranteed not to be the last io reference count
1522		 * because the caller (xfs_buf_submit) holds a count itself.
1523		 */
1524		atomic_dec(&bp->b_io_remaining);
1525		xfs_buf_ioerror(bp, -EIO);
1526		bio_put(bio);
1527	}
1528
1529}
1530
1531STATIC void
1532_xfs_buf_ioapply(
1533	struct xfs_buf	*bp)
1534{
1535	struct blk_plug	plug;
1536	blk_opf_t	op;
1537	int		offset;
1538	int		size;
1539	int		i;
1540
1541	/*
1542	 * Make sure we capture only current IO errors rather than stale errors
1543	 * left over from previous use of the buffer (e.g. failed readahead).
1544	 */
1545	bp->b_error = 0;
1546
1547	if (bp->b_flags & XBF_WRITE) {
1548		op = REQ_OP_WRITE;
1549
1550		/*
1551		 * Run the write verifier callback function if it exists. If
1552		 * this function fails it will mark the buffer with an error and
1553		 * the IO should not be dispatched.
1554		 */
1555		if (bp->b_ops) {
1556			bp->b_ops->verify_write(bp);
1557			if (bp->b_error) {
1558				xfs_force_shutdown(bp->b_mount,
1559						   SHUTDOWN_CORRUPT_INCORE);
1560				return;
1561			}
1562		} else if (bp->b_rhash_key != XFS_BUF_DADDR_NULL) {
1563			struct xfs_mount *mp = bp->b_mount;
1564
1565			/*
1566			 * non-crc filesystems don't attach verifiers during
1567			 * log recovery, so don't warn for such filesystems.
1568			 */
1569			if (xfs_has_crc(mp)) {
1570				xfs_warn(mp,
1571					"%s: no buf ops on daddr 0x%llx len %d",
1572					__func__, xfs_buf_daddr(bp),
1573					bp->b_length);
1574				xfs_hex_dump(bp->b_addr,
1575						XFS_CORRUPTION_DUMP_LEN);
1576				dump_stack();
1577			}
1578		}
1579	} else {
1580		op = REQ_OP_READ;
1581		if (bp->b_flags & XBF_READ_AHEAD)
1582			op |= REQ_RAHEAD;
1583	}
1584
1585	/* we only use the buffer cache for meta-data */
1586	op |= REQ_META;
1587
1588	/*
1589	 * Walk all the vectors issuing IO on them. Set up the initial offset
1590	 * into the buffer and the desired IO size before we start -
1591	 * _xfs_buf_ioapply_vec() will modify them appropriately for each
1592	 * subsequent call.
1593	 */
1594	offset = bp->b_offset;
1595	size = BBTOB(bp->b_length);
1596	blk_start_plug(&plug);
1597	for (i = 0; i < bp->b_map_count; i++) {
1598		xfs_buf_ioapply_map(bp, i, &offset, &size, op);
1599		if (bp->b_error)
1600			break;
1601		if (size <= 0)
1602			break;	/* all done */
1603	}
1604	blk_finish_plug(&plug);
1605}
1606
1607/*
1608 * Wait for I/O completion of a sync buffer and return the I/O error code.
1609 */
1610static int
1611xfs_buf_iowait(
1612	struct xfs_buf	*bp)
1613{
1614	ASSERT(!(bp->b_flags & XBF_ASYNC));
1615
1616	trace_xfs_buf_iowait(bp, _RET_IP_);
1617	wait_for_completion(&bp->b_iowait);
1618	trace_xfs_buf_iowait_done(bp, _RET_IP_);
1619
1620	return bp->b_error;
1621}
1622
1623/*
1624 * Buffer I/O submission path, read or write. Asynchronous submission transfers
1625 * the buffer lock ownership and the current reference to the IO. It is not
1626 * safe to reference the buffer after a call to this function unless the caller
1627 * holds an additional reference itself.
1628 */
1629static int
1630__xfs_buf_submit(
1631	struct xfs_buf	*bp,
1632	bool		wait)
1633{
1634	int		error = 0;
1635
1636	trace_xfs_buf_submit(bp, _RET_IP_);
1637
1638	ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1639
1640	/*
1641	 * On log shutdown we stale and complete the buffer immediately. We can
1642	 * be called to read the superblock before the log has been set up, so
1643	 * be careful checking the log state.
1644	 *
1645	 * Checking the mount shutdown state here can result in the log tail
1646	 * moving inappropriately on disk as the log may not yet be shut down.
1647	 * i.e. failing this buffer on mount shutdown can remove it from the AIL
1648	 * and move the tail of the log forwards without having written this
1649	 * buffer to disk. This corrupts the log tail state in memory, and
1650	 * because the log may not be shut down yet, it can then be propagated
1651	 * to disk before the log is shutdown. Hence we check log shutdown
1652	 * state here rather than mount state to avoid corrupting the log tail
1653	 * on shutdown.
1654	 */
1655	if (bp->b_mount->m_log &&
1656	    xlog_is_shutdown(bp->b_mount->m_log)) {
1657		xfs_buf_ioend_fail(bp);
1658		return -EIO;
1659	}
1660
1661	/*
1662	 * Grab a reference so the buffer does not go away underneath us. For
1663	 * async buffers, I/O completion drops the callers reference, which
1664	 * could occur before submission returns.
1665	 */
1666	xfs_buf_hold(bp);
1667
1668	if (bp->b_flags & XBF_WRITE)
1669		xfs_buf_wait_unpin(bp);
1670
1671	/* clear the internal error state to avoid spurious errors */
1672	bp->b_io_error = 0;
1673
1674	/*
1675	 * Set the count to 1 initially, this will stop an I/O completion
1676	 * callout which happens before we have started all the I/O from calling
1677	 * xfs_buf_ioend too early.
1678	 */
1679	atomic_set(&bp->b_io_remaining, 1);
1680	if (bp->b_flags & XBF_ASYNC)
1681		xfs_buf_ioacct_inc(bp);
1682	_xfs_buf_ioapply(bp);
1683
1684	/*
1685	 * If _xfs_buf_ioapply failed, we can get back here with only the IO
1686	 * reference we took above. If we drop it to zero, run completion so
1687	 * that we don't return to the caller with completion still pending.
1688	 */
1689	if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
1690		if (bp->b_error || !(bp->b_flags & XBF_ASYNC))
1691			xfs_buf_ioend(bp);
1692		else
1693			xfs_buf_ioend_async(bp);
1694	}
1695
1696	if (wait)
1697		error = xfs_buf_iowait(bp);
1698
1699	/*
1700	 * Release the hold that keeps the buffer referenced for the entire
1701	 * I/O. Note that if the buffer is async, it is not safe to reference
1702	 * after this release.
1703	 */
1704	xfs_buf_rele(bp);
1705	return error;
1706}
1707
1708void *
1709xfs_buf_offset(
1710	struct xfs_buf		*bp,
1711	size_t			offset)
1712{
1713	struct page		*page;
1714
1715	if (bp->b_addr)
1716		return bp->b_addr + offset;
1717
1718	page = bp->b_pages[offset >> PAGE_SHIFT];
1719	return page_address(page) + (offset & (PAGE_SIZE-1));
1720}
1721
1722void
1723xfs_buf_zero(
1724	struct xfs_buf		*bp,
1725	size_t			boff,
1726	size_t			bsize)
1727{
1728	size_t			bend;
1729
1730	bend = boff + bsize;
1731	while (boff < bend) {
1732		struct page	*page;
1733		int		page_index, page_offset, csize;
1734
1735		page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
1736		page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
1737		page = bp->b_pages[page_index];
1738		csize = min_t(size_t, PAGE_SIZE - page_offset,
1739				      BBTOB(bp->b_length) - boff);
1740
1741		ASSERT((csize + page_offset) <= PAGE_SIZE);
1742
1743		memset(page_address(page) + page_offset, 0, csize);
1744
1745		boff += csize;
1746	}
1747}
1748
1749/*
1750 * Log a message about and stale a buffer that a caller has decided is corrupt.
1751 *
1752 * This function should be called for the kinds of metadata corruption that
1753 * cannot be detect from a verifier, such as incorrect inter-block relationship
1754 * data.  Do /not/ call this function from a verifier function.
1755 *
1756 * The buffer must be XBF_DONE prior to the call.  Afterwards, the buffer will
1757 * be marked stale, but b_error will not be set.  The caller is responsible for
1758 * releasing the buffer or fixing it.
1759 */
1760void
1761__xfs_buf_mark_corrupt(
1762	struct xfs_buf		*bp,
1763	xfs_failaddr_t		fa)
1764{
1765	ASSERT(bp->b_flags & XBF_DONE);
1766
1767	xfs_buf_corruption_error(bp, fa);
1768	xfs_buf_stale(bp);
1769}
1770
1771/*
1772 *	Handling of buffer targets (buftargs).
1773 */
1774
1775/*
1776 * Wait for any bufs with callbacks that have been submitted but have not yet
1777 * returned. These buffers will have an elevated hold count, so wait on those
1778 * while freeing all the buffers only held by the LRU.
1779 */
1780static enum lru_status
1781xfs_buftarg_drain_rele(
1782	struct list_head	*item,
1783	struct list_lru_one	*lru,
1784	spinlock_t		*lru_lock,
1785	void			*arg)
1786
1787{
1788	struct xfs_buf		*bp = container_of(item, struct xfs_buf, b_lru);
1789	struct list_head	*dispose = arg;
1790
1791	if (atomic_read(&bp->b_hold) > 1) {
1792		/* need to wait, so skip it this pass */
1793		trace_xfs_buf_drain_buftarg(bp, _RET_IP_);
1794		return LRU_SKIP;
1795	}
1796	if (!spin_trylock(&bp->b_lock))
1797		return LRU_SKIP;
1798
1799	/*
1800	 * clear the LRU reference count so the buffer doesn't get
1801	 * ignored in xfs_buf_rele().
1802	 */
1803	atomic_set(&bp->b_lru_ref, 0);
1804	bp->b_state |= XFS_BSTATE_DISPOSE;
1805	list_lru_isolate_move(lru, item, dispose);
1806	spin_unlock(&bp->b_lock);
1807	return LRU_REMOVED;
1808}
1809
1810/*
1811 * Wait for outstanding I/O on the buftarg to complete.
1812 */
1813void
1814xfs_buftarg_wait(
1815	struct xfs_buftarg	*btp)
1816{
1817	/*
1818	 * First wait on the buftarg I/O count for all in-flight buffers to be
1819	 * released. This is critical as new buffers do not make the LRU until
1820	 * they are released.
1821	 *
1822	 * Next, flush the buffer workqueue to ensure all completion processing
1823	 * has finished. Just waiting on buffer locks is not sufficient for
1824	 * async IO as the reference count held over IO is not released until
1825	 * after the buffer lock is dropped. Hence we need to ensure here that
1826	 * all reference counts have been dropped before we start walking the
1827	 * LRU list.
1828	 */
1829	while (percpu_counter_sum(&btp->bt_io_count))
1830		delay(100);
1831	flush_workqueue(btp->bt_mount->m_buf_workqueue);
1832}
1833
1834void
1835xfs_buftarg_drain(
1836	struct xfs_buftarg	*btp)
1837{
1838	LIST_HEAD(dispose);
1839	int			loop = 0;
1840	bool			write_fail = false;
1841
1842	xfs_buftarg_wait(btp);
1843
1844	/* loop until there is nothing left on the lru list. */
1845	while (list_lru_count(&btp->bt_lru)) {
1846		list_lru_walk(&btp->bt_lru, xfs_buftarg_drain_rele,
1847			      &dispose, LONG_MAX);
1848
1849		while (!list_empty(&dispose)) {
1850			struct xfs_buf *bp;
1851			bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1852			list_del_init(&bp->b_lru);
1853			if (bp->b_flags & XBF_WRITE_FAIL) {
1854				write_fail = true;
1855				xfs_buf_alert_ratelimited(bp,
1856					"XFS: Corruption Alert",
1857"Corruption Alert: Buffer at daddr 0x%llx had permanent write failures!",
1858					(long long)xfs_buf_daddr(bp));
1859			}
1860			xfs_buf_rele(bp);
1861		}
1862		if (loop++ != 0)
1863			delay(100);
1864	}
1865
1866	/*
1867	 * If one or more failed buffers were freed, that means dirty metadata
1868	 * was thrown away. This should only ever happen after I/O completion
1869	 * handling has elevated I/O error(s) to permanent failures and shuts
1870	 * down the journal.
1871	 */
1872	if (write_fail) {
1873		ASSERT(xlog_is_shutdown(btp->bt_mount->m_log));
1874		xfs_alert(btp->bt_mount,
1875	      "Please run xfs_repair to determine the extent of the problem.");
1876	}
1877}
1878
1879static enum lru_status
1880xfs_buftarg_isolate(
1881	struct list_head	*item,
1882	struct list_lru_one	*lru,
1883	spinlock_t		*lru_lock,
1884	void			*arg)
1885{
1886	struct xfs_buf		*bp = container_of(item, struct xfs_buf, b_lru);
1887	struct list_head	*dispose = arg;
1888
1889	/*
1890	 * we are inverting the lru lock/bp->b_lock here, so use a trylock.
1891	 * If we fail to get the lock, just skip it.
1892	 */
1893	if (!spin_trylock(&bp->b_lock))
1894		return LRU_SKIP;
1895	/*
1896	 * Decrement the b_lru_ref count unless the value is already
1897	 * zero. If the value is already zero, we need to reclaim the
1898	 * buffer, otherwise it gets another trip through the LRU.
1899	 */
1900	if (atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
1901		spin_unlock(&bp->b_lock);
1902		return LRU_ROTATE;
1903	}
1904
1905	bp->b_state |= XFS_BSTATE_DISPOSE;
1906	list_lru_isolate_move(lru, item, dispose);
1907	spin_unlock(&bp->b_lock);
1908	return LRU_REMOVED;
1909}
1910
1911static unsigned long
1912xfs_buftarg_shrink_scan(
1913	struct shrinker		*shrink,
1914	struct shrink_control	*sc)
1915{
1916	struct xfs_buftarg	*btp = shrink->private_data;
 
1917	LIST_HEAD(dispose);
1918	unsigned long		freed;
1919
1920	freed = list_lru_shrink_walk(&btp->bt_lru, sc,
1921				     xfs_buftarg_isolate, &dispose);
1922
1923	while (!list_empty(&dispose)) {
1924		struct xfs_buf *bp;
1925		bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1926		list_del_init(&bp->b_lru);
1927		xfs_buf_rele(bp);
1928	}
1929
1930	return freed;
1931}
1932
1933static unsigned long
1934xfs_buftarg_shrink_count(
1935	struct shrinker		*shrink,
1936	struct shrink_control	*sc)
1937{
1938	struct xfs_buftarg	*btp = shrink->private_data;
 
1939	return list_lru_shrink_count(&btp->bt_lru, sc);
1940}
1941
1942void
1943xfs_free_buftarg(
1944	struct xfs_buftarg	*btp)
1945{
1946	shrinker_free(btp->bt_shrinker);
1947	ASSERT(percpu_counter_sum(&btp->bt_io_count) == 0);
1948	percpu_counter_destroy(&btp->bt_io_count);
1949	list_lru_destroy(&btp->bt_lru);
1950
 
 
1951	fs_put_dax(btp->bt_daxdev, btp->bt_mount);
1952	/* the main block device is closed by kill_block_super */
1953	if (btp->bt_bdev != btp->bt_mount->m_super->s_bdev)
1954		bdev_release(btp->bt_bdev_handle);
1955
1956	kmem_free(btp);
1957}
1958
1959int
1960xfs_setsize_buftarg(
1961	xfs_buftarg_t		*btp,
1962	unsigned int		sectorsize)
1963{
1964	/* Set up metadata sector size info */
1965	btp->bt_meta_sectorsize = sectorsize;
1966	btp->bt_meta_sectormask = sectorsize - 1;
1967
1968	if (set_blocksize(btp->bt_bdev, sectorsize)) {
1969		xfs_warn(btp->bt_mount,
1970			"Cannot set_blocksize to %u on device %pg",
1971			sectorsize, btp->bt_bdev);
1972		return -EINVAL;
1973	}
1974
1975	/* Set up device logical sector size mask */
1976	btp->bt_logical_sectorsize = bdev_logical_block_size(btp->bt_bdev);
1977	btp->bt_logical_sectormask = bdev_logical_block_size(btp->bt_bdev) - 1;
1978
1979	return 0;
1980}
1981
1982/*
1983 * When allocating the initial buffer target we have not yet
1984 * read in the superblock, so don't know what sized sectors
1985 * are being used at this early stage.  Play safe.
1986 */
1987STATIC int
1988xfs_setsize_buftarg_early(
1989	xfs_buftarg_t		*btp)
 
1990{
1991	return xfs_setsize_buftarg(btp, bdev_logical_block_size(btp->bt_bdev));
1992}
1993
1994struct xfs_buftarg *
1995xfs_alloc_buftarg(
1996	struct xfs_mount	*mp,
1997	struct bdev_handle	*bdev_handle)
1998{
1999	xfs_buftarg_t		*btp;
2000	const struct dax_holder_operations *ops = NULL;
2001
2002#if defined(CONFIG_FS_DAX) && defined(CONFIG_MEMORY_FAILURE)
2003	ops = &xfs_dax_holder_operations;
2004#endif
2005	btp = kmem_zalloc(sizeof(*btp), KM_NOFS);
2006
2007	btp->bt_mount = mp;
2008	btp->bt_bdev_handle = bdev_handle;
2009	btp->bt_dev = bdev_handle->bdev->bd_dev;
2010	btp->bt_bdev = bdev_handle->bdev;
2011	btp->bt_daxdev = fs_dax_get_by_bdev(btp->bt_bdev, &btp->bt_dax_part_off,
2012					    mp, ops);
2013
2014	/*
2015	 * Buffer IO error rate limiting. Limit it to no more than 10 messages
2016	 * per 30 seconds so as to not spam logs too much on repeated errors.
2017	 */
2018	ratelimit_state_init(&btp->bt_ioerror_rl, 30 * HZ,
2019			     DEFAULT_RATELIMIT_BURST);
2020
2021	if (xfs_setsize_buftarg_early(btp))
2022		goto error_free;
2023
2024	if (list_lru_init(&btp->bt_lru))
2025		goto error_free;
2026
2027	if (percpu_counter_init(&btp->bt_io_count, 0, GFP_KERNEL))
2028		goto error_lru;
2029
2030	btp->bt_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE, "xfs-buf:%s",
2031					  mp->m_super->s_id);
2032	if (!btp->bt_shrinker)
 
 
 
2033		goto error_pcpu;
2034
2035	btp->bt_shrinker->count_objects = xfs_buftarg_shrink_count;
2036	btp->bt_shrinker->scan_objects = xfs_buftarg_shrink_scan;
2037	btp->bt_shrinker->private_data = btp;
2038
2039	shrinker_register(btp->bt_shrinker);
2040
2041	return btp;
2042
2043error_pcpu:
2044	percpu_counter_destroy(&btp->bt_io_count);
2045error_lru:
2046	list_lru_destroy(&btp->bt_lru);
2047error_free:
2048	kmem_free(btp);
2049	return NULL;
2050}
2051
2052static inline void
2053xfs_buf_list_del(
2054	struct xfs_buf		*bp)
2055{
2056	list_del_init(&bp->b_list);
2057	wake_up_var(&bp->b_list);
2058}
2059
2060/*
2061 * Cancel a delayed write list.
2062 *
2063 * Remove each buffer from the list, clear the delwri queue flag and drop the
2064 * associated buffer reference.
2065 */
2066void
2067xfs_buf_delwri_cancel(
2068	struct list_head	*list)
2069{
2070	struct xfs_buf		*bp;
2071
2072	while (!list_empty(list)) {
2073		bp = list_first_entry(list, struct xfs_buf, b_list);
2074
2075		xfs_buf_lock(bp);
2076		bp->b_flags &= ~_XBF_DELWRI_Q;
2077		xfs_buf_list_del(bp);
2078		xfs_buf_relse(bp);
2079	}
2080}
2081
2082/*
2083 * Add a buffer to the delayed write list.
2084 *
2085 * This queues a buffer for writeout if it hasn't already been.  Note that
2086 * neither this routine nor the buffer list submission functions perform
2087 * any internal synchronization.  It is expected that the lists are thread-local
2088 * to the callers.
2089 *
2090 * Returns true if we queued up the buffer, or false if it already had
2091 * been on the buffer list.
2092 */
2093bool
2094xfs_buf_delwri_queue(
2095	struct xfs_buf		*bp,
2096	struct list_head	*list)
2097{
2098	ASSERT(xfs_buf_islocked(bp));
2099	ASSERT(!(bp->b_flags & XBF_READ));
2100
2101	/*
2102	 * If the buffer is already marked delwri it already is queued up
2103	 * by someone else for imediate writeout.  Just ignore it in that
2104	 * case.
2105	 */
2106	if (bp->b_flags & _XBF_DELWRI_Q) {
2107		trace_xfs_buf_delwri_queued(bp, _RET_IP_);
2108		return false;
2109	}
2110
2111	trace_xfs_buf_delwri_queue(bp, _RET_IP_);
2112
2113	/*
2114	 * If a buffer gets written out synchronously or marked stale while it
2115	 * is on a delwri list we lazily remove it. To do this, the other party
2116	 * clears the  _XBF_DELWRI_Q flag but otherwise leaves the buffer alone.
2117	 * It remains referenced and on the list.  In a rare corner case it
2118	 * might get readded to a delwri list after the synchronous writeout, in
2119	 * which case we need just need to re-add the flag here.
2120	 */
2121	bp->b_flags |= _XBF_DELWRI_Q;
2122	if (list_empty(&bp->b_list)) {
2123		atomic_inc(&bp->b_hold);
2124		list_add_tail(&bp->b_list, list);
2125	}
2126
2127	return true;
2128}
2129
2130/*
2131 * Queue a buffer to this delwri list as part of a data integrity operation.
2132 * If the buffer is on any other delwri list, we'll wait for that to clear
2133 * so that the caller can submit the buffer for IO and wait for the result.
2134 * Callers must ensure the buffer is not already on the list.
2135 */
2136void
2137xfs_buf_delwri_queue_here(
2138	struct xfs_buf		*bp,
2139	struct list_head	*buffer_list)
2140{
2141	/*
2142	 * We need this buffer to end up on the /caller's/ delwri list, not any
2143	 * old list.  This can happen if the buffer is marked stale (which
2144	 * clears DELWRI_Q) after the AIL queues the buffer to its list but
2145	 * before the AIL has a chance to submit the list.
2146	 */
2147	while (!list_empty(&bp->b_list)) {
2148		xfs_buf_unlock(bp);
2149		wait_var_event(&bp->b_list, list_empty(&bp->b_list));
2150		xfs_buf_lock(bp);
2151	}
2152
2153	ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
2154
2155	xfs_buf_delwri_queue(bp, buffer_list);
2156}
2157
2158/*
2159 * Compare function is more complex than it needs to be because
2160 * the return value is only 32 bits and we are doing comparisons
2161 * on 64 bit values
2162 */
2163static int
2164xfs_buf_cmp(
2165	void			*priv,
2166	const struct list_head	*a,
2167	const struct list_head	*b)
2168{
2169	struct xfs_buf	*ap = container_of(a, struct xfs_buf, b_list);
2170	struct xfs_buf	*bp = container_of(b, struct xfs_buf, b_list);
2171	xfs_daddr_t		diff;
2172
2173	diff = ap->b_maps[0].bm_bn - bp->b_maps[0].bm_bn;
2174	if (diff < 0)
2175		return -1;
2176	if (diff > 0)
2177		return 1;
2178	return 0;
2179}
2180
2181/*
2182 * Submit buffers for write. If wait_list is specified, the buffers are
2183 * submitted using sync I/O and placed on the wait list such that the caller can
2184 * iowait each buffer. Otherwise async I/O is used and the buffers are released
2185 * at I/O completion time. In either case, buffers remain locked until I/O
2186 * completes and the buffer is released from the queue.
2187 */
2188static int
2189xfs_buf_delwri_submit_buffers(
2190	struct list_head	*buffer_list,
2191	struct list_head	*wait_list)
2192{
2193	struct xfs_buf		*bp, *n;
2194	int			pinned = 0;
2195	struct blk_plug		plug;
2196
2197	list_sort(NULL, buffer_list, xfs_buf_cmp);
2198
2199	blk_start_plug(&plug);
2200	list_for_each_entry_safe(bp, n, buffer_list, b_list) {
2201		if (!wait_list) {
2202			if (!xfs_buf_trylock(bp))
2203				continue;
2204			if (xfs_buf_ispinned(bp)) {
2205				xfs_buf_unlock(bp);
2206				pinned++;
2207				continue;
2208			}
2209		} else {
2210			xfs_buf_lock(bp);
2211		}
2212
2213		/*
2214		 * Someone else might have written the buffer synchronously or
2215		 * marked it stale in the meantime.  In that case only the
2216		 * _XBF_DELWRI_Q flag got cleared, and we have to drop the
2217		 * reference and remove it from the list here.
2218		 */
2219		if (!(bp->b_flags & _XBF_DELWRI_Q)) {
2220			xfs_buf_list_del(bp);
2221			xfs_buf_relse(bp);
2222			continue;
2223		}
2224
2225		trace_xfs_buf_delwri_split(bp, _RET_IP_);
2226
2227		/*
2228		 * If we have a wait list, each buffer (and associated delwri
2229		 * queue reference) transfers to it and is submitted
2230		 * synchronously. Otherwise, drop the buffer from the delwri
2231		 * queue and submit async.
2232		 */
2233		bp->b_flags &= ~_XBF_DELWRI_Q;
2234		bp->b_flags |= XBF_WRITE;
2235		if (wait_list) {
2236			bp->b_flags &= ~XBF_ASYNC;
2237			list_move_tail(&bp->b_list, wait_list);
2238		} else {
2239			bp->b_flags |= XBF_ASYNC;
2240			xfs_buf_list_del(bp);
2241		}
2242		__xfs_buf_submit(bp, false);
2243	}
2244	blk_finish_plug(&plug);
2245
2246	return pinned;
2247}
2248
2249/*
2250 * Write out a buffer list asynchronously.
2251 *
2252 * This will take the @buffer_list, write all non-locked and non-pinned buffers
2253 * out and not wait for I/O completion on any of the buffers.  This interface
2254 * is only safely useable for callers that can track I/O completion by higher
2255 * level means, e.g. AIL pushing as the @buffer_list is consumed in this
2256 * function.
2257 *
2258 * Note: this function will skip buffers it would block on, and in doing so
2259 * leaves them on @buffer_list so they can be retried on a later pass. As such,
2260 * it is up to the caller to ensure that the buffer list is fully submitted or
2261 * cancelled appropriately when they are finished with the list. Failure to
2262 * cancel or resubmit the list until it is empty will result in leaked buffers
2263 * at unmount time.
2264 */
2265int
2266xfs_buf_delwri_submit_nowait(
2267	struct list_head	*buffer_list)
2268{
2269	return xfs_buf_delwri_submit_buffers(buffer_list, NULL);
2270}
2271
2272/*
2273 * Write out a buffer list synchronously.
2274 *
2275 * This will take the @buffer_list, write all buffers out and wait for I/O
2276 * completion on all of the buffers. @buffer_list is consumed by the function,
2277 * so callers must have some other way of tracking buffers if they require such
2278 * functionality.
2279 */
2280int
2281xfs_buf_delwri_submit(
2282	struct list_head	*buffer_list)
2283{
2284	LIST_HEAD		(wait_list);
2285	int			error = 0, error2;
2286	struct xfs_buf		*bp;
2287
2288	xfs_buf_delwri_submit_buffers(buffer_list, &wait_list);
2289
2290	/* Wait for IO to complete. */
2291	while (!list_empty(&wait_list)) {
2292		bp = list_first_entry(&wait_list, struct xfs_buf, b_list);
2293
2294		xfs_buf_list_del(bp);
2295
2296		/*
2297		 * Wait on the locked buffer, check for errors and unlock and
2298		 * release the delwri queue reference.
2299		 */
2300		error2 = xfs_buf_iowait(bp);
2301		xfs_buf_relse(bp);
2302		if (!error)
2303			error = error2;
2304	}
2305
2306	return error;
2307}
2308
2309/*
2310 * Push a single buffer on a delwri queue.
2311 *
2312 * The purpose of this function is to submit a single buffer of a delwri queue
2313 * and return with the buffer still on the original queue. The waiting delwri
2314 * buffer submission infrastructure guarantees transfer of the delwri queue
2315 * buffer reference to a temporary wait list. We reuse this infrastructure to
2316 * transfer the buffer back to the original queue.
2317 *
2318 * Note the buffer transitions from the queued state, to the submitted and wait
2319 * listed state and back to the queued state during this call. The buffer
2320 * locking and queue management logic between _delwri_pushbuf() and
2321 * _delwri_queue() guarantee that the buffer cannot be queued to another list
2322 * before returning.
2323 */
2324int
2325xfs_buf_delwri_pushbuf(
2326	struct xfs_buf		*bp,
2327	struct list_head	*buffer_list)
2328{
2329	LIST_HEAD		(submit_list);
2330	int			error;
2331
2332	ASSERT(bp->b_flags & _XBF_DELWRI_Q);
2333
2334	trace_xfs_buf_delwri_pushbuf(bp, _RET_IP_);
2335
2336	/*
2337	 * Isolate the buffer to a new local list so we can submit it for I/O
2338	 * independently from the rest of the original list.
2339	 */
2340	xfs_buf_lock(bp);
2341	list_move(&bp->b_list, &submit_list);
2342	xfs_buf_unlock(bp);
2343
2344	/*
2345	 * Delwri submission clears the DELWRI_Q buffer flag and returns with
2346	 * the buffer on the wait list with the original reference. Rather than
2347	 * bounce the buffer from a local wait list back to the original list
2348	 * after I/O completion, reuse the original list as the wait list.
2349	 */
2350	xfs_buf_delwri_submit_buffers(&submit_list, buffer_list);
2351
2352	/*
2353	 * The buffer is now locked, under I/O and wait listed on the original
2354	 * delwri queue. Wait for I/O completion, restore the DELWRI_Q flag and
2355	 * return with the buffer unlocked and on the original queue.
2356	 */
2357	error = xfs_buf_iowait(bp);
2358	bp->b_flags |= _XBF_DELWRI_Q;
2359	xfs_buf_unlock(bp);
2360
2361	return error;
2362}
2363
2364void xfs_buf_set_ref(struct xfs_buf *bp, int lru_ref)
2365{
2366	/*
2367	 * Set the lru reference count to 0 based on the error injection tag.
2368	 * This allows userspace to disrupt buffer caching for debug/testing
2369	 * purposes.
2370	 */
2371	if (XFS_TEST_ERROR(false, bp->b_mount, XFS_ERRTAG_BUF_LRU_REF))
2372		lru_ref = 0;
2373
2374	atomic_set(&bp->b_lru_ref, lru_ref);
2375}
2376
2377/*
2378 * Verify an on-disk magic value against the magic value specified in the
2379 * verifier structure. The verifier magic is in disk byte order so the caller is
2380 * expected to pass the value directly from disk.
2381 */
2382bool
2383xfs_verify_magic(
2384	struct xfs_buf		*bp,
2385	__be32			dmagic)
2386{
2387	struct xfs_mount	*mp = bp->b_mount;
2388	int			idx;
2389
2390	idx = xfs_has_crc(mp);
2391	if (WARN_ON(!bp->b_ops || !bp->b_ops->magic[idx]))
2392		return false;
2393	return dmagic == bp->b_ops->magic[idx];
2394}
2395/*
2396 * Verify an on-disk magic value against the magic value specified in the
2397 * verifier structure. The verifier magic is in disk byte order so the caller is
2398 * expected to pass the value directly from disk.
2399 */
2400bool
2401xfs_verify_magic16(
2402	struct xfs_buf		*bp,
2403	__be16			dmagic)
2404{
2405	struct xfs_mount	*mp = bp->b_mount;
2406	int			idx;
2407
2408	idx = xfs_has_crc(mp);
2409	if (WARN_ON(!bp->b_ops || !bp->b_ops->magic16[idx]))
2410		return false;
2411	return dmagic == bp->b_ops->magic16[idx];
2412}