1/*
   2 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
   3 * All Rights Reserved.
   4 *
   5 * This program is free software; you can redistribute it and/or
   6 * modify it under the terms of the GNU General Public License as
   7 * published by the Free Software Foundation.
   8 *
   9 * This program is distributed in the hope that it would be useful,
  10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 * GNU General Public License for more details.
  13 *
  14 * You should have received a copy of the GNU General Public License
  15 * along with this program; if not, write the Free Software Foundation,
  16 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  17 */
  18#include "xfs.h"
  19#include <linux/stddef.h>
  20#include <linux/errno.h>
  21#include <linux/gfp.h>
  22#include <linux/pagemap.h>
  23#include <linux/init.h>
  24#include <linux/vmalloc.h>
  25#include <linux/bio.h>
  26#include <linux/sysctl.h>
  27#include <linux/proc_fs.h>
  28#include <linux/workqueue.h>
  29#include <linux/percpu.h>
  30#include <linux/blkdev.h>
  31#include <linux/hash.h>
  32#include <linux/kthread.h>
  33#include <linux/migrate.h>
  34#include <linux/backing-dev.h>
  35#include <linux/freezer.h>
  36#include <linux/sched/mm.h>
  37
  38#include "xfs_format.h"
  39#include "xfs_log_format.h"
  40#include "xfs_trans_resv.h"
  41#include "xfs_sb.h"
  42#include "xfs_mount.h"
  43#include "xfs_trace.h"
  44#include "xfs_log.h"
  45#include "xfs_errortag.h"
  46#include "xfs_error.h"
  47
  48static kmem_zone_t *xfs_buf_zone;
  49
  50#ifdef XFS_BUF_LOCK_TRACKING
  51# define XB_SET_OWNER(bp)	((bp)->b_last_holder = current->pid)
  52# define XB_CLEAR_OWNER(bp)	((bp)->b_last_holder = -1)
  53# define XB_GET_OWNER(bp)	((bp)->b_last_holder)
  54#else
  55# define XB_SET_OWNER(bp)	do { } while (0)
  56# define XB_CLEAR_OWNER(bp)	do { } while (0)
  57# define XB_GET_OWNER(bp)	do { } while (0)
  58#endif
  59
  60#define xb_to_gfp(flags) \
  61	((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : GFP_NOFS) | __GFP_NOWARN)
  62
  63
  64static inline int
  65xfs_buf_is_vmapped(
  66	struct xfs_buf	*bp)
  67{
  68	/*
  69	 * Return true if the buffer is vmapped.
  70	 *
  71	 * b_addr is null if the buffer is not mapped, but the code is clever
  72	 * enough to know it doesn't have to map a single page, so the check has
  73	 * to be both for b_addr and bp->b_page_count > 1.
  74	 */
  75	return bp->b_addr && bp->b_page_count > 1;
  76}
  77
  78static inline int
  79xfs_buf_vmap_len(
  80	struct xfs_buf	*bp)
  81{
  82	return (bp->b_page_count * PAGE_SIZE) - bp->b_offset;
  83}
  84
  85/*
  86 * Bump the I/O in flight count on the buftarg if we haven't yet done so for
  87 * this buffer. The count is incremented once per buffer (per hold cycle)
  88 * because the corresponding decrement is deferred to buffer release. Buffers
  89 * can undergo I/O multiple times in a hold-release cycle and per buffer I/O
  90 * tracking adds unnecessary overhead. This is used for sychronization purposes
  91 * with unmount (see xfs_wait_buftarg()), so all we really need is a count of
  92 * in-flight buffers.
  93 *
  94 * Buffers that are never released (e.g., superblock, iclog buffers) must set
  95 * the XBF_NO_IOACCT flag before I/O submission. Otherwise, the buftarg count
  96 * never reaches zero and unmount hangs indefinitely.
  97 */
  98static inline void
  99xfs_buf_ioacct_inc(
 100	struct xfs_buf	*bp)
 101{
 102	if (bp->b_flags & XBF_NO_IOACCT)
 103		return;
 104
 105	ASSERT(bp->b_flags & XBF_ASYNC);
 106	spin_lock(&bp->b_lock);
 107	if (!(bp->b_state & XFS_BSTATE_IN_FLIGHT)) {
 108		bp->b_state |= XFS_BSTATE_IN_FLIGHT;
 109		percpu_counter_inc(&bp->b_target->bt_io_count);
 110	}
 111	spin_unlock(&bp->b_lock);
 112}
 113
 114/*
 115 * Clear the in-flight state on a buffer about to be released to the LRU or
 116 * freed and unaccount from the buftarg.
 117 */
 118static inline void
 119__xfs_buf_ioacct_dec(
 120	struct xfs_buf	*bp)
 121{
 122	lockdep_assert_held(&bp->b_lock);
 123
 124	if (bp->b_state & XFS_BSTATE_IN_FLIGHT) {
 125		bp->b_state &= ~XFS_BSTATE_IN_FLIGHT;
 126		percpu_counter_dec(&bp->b_target->bt_io_count);
 127	}
 128}
 129
 130static inline void
 131xfs_buf_ioacct_dec(
 132	struct xfs_buf	*bp)
 133{
 134	spin_lock(&bp->b_lock);
 135	__xfs_buf_ioacct_dec(bp);
 136	spin_unlock(&bp->b_lock);
 
 
 137}
 138
 139/*
 140 * When we mark a buffer stale, we remove the buffer from the LRU and clear the
 141 * b_lru_ref count so that the buffer is freed immediately when the buffer
 142 * reference count falls to zero. If the buffer is already on the LRU, we need
 143 * to remove the reference that LRU holds on the buffer.
 144 *
 145 * This prevents build-up of stale buffers on the LRU.
 146 */
 147void
 148xfs_buf_stale(
 149	struct xfs_buf	*bp)
 150{
 151	ASSERT(xfs_buf_islocked(bp));
 152
 153	bp->b_flags |= XBF_STALE;
 154
 155	/*
 156	 * Clear the delwri status so that a delwri queue walker will not
 157	 * flush this buffer to disk now that it is stale. The delwri queue has
 158	 * a reference to the buffer, so this is safe to do.
 159	 */
 160	bp->b_flags &= ~_XBF_DELWRI_Q;
 161
 162	/*
 163	 * Once the buffer is marked stale and unlocked, a subsequent lookup
 164	 * could reset b_flags. There is no guarantee that the buffer is
 165	 * unaccounted (released to LRU) before that occurs. Drop in-flight
 166	 * status now to preserve accounting consistency.
 167	 */
 168	spin_lock(&bp->b_lock);
 169	__xfs_buf_ioacct_dec(bp);
 170
 
 171	atomic_set(&bp->b_lru_ref, 0);
 172	if (!(bp->b_state & XFS_BSTATE_DISPOSE) &&
 173	    (list_lru_del(&bp->b_target->bt_lru, &bp->b_lru)))
 174		atomic_dec(&bp->b_hold);
 175
 176	ASSERT(atomic_read(&bp->b_hold) >= 1);
 177	spin_unlock(&bp->b_lock);
 178}
 179
 180static int
 181xfs_buf_get_maps(
 182	struct xfs_buf		*bp,
 183	int			map_count)
 184{
 185	ASSERT(bp->b_maps == NULL);
 186	bp->b_map_count = map_count;
 187
 188	if (map_count == 1) {
 189		bp->b_maps = &bp->__b_map;
 190		return 0;
 191	}
 192
 193	bp->b_maps = kmem_zalloc(map_count * sizeof(struct xfs_buf_map),
 194				KM_NOFS);
 195	if (!bp->b_maps)
 196		return -ENOMEM;
 197	return 0;
 198}
 199
 200/*
 201 *	Frees b_pages if it was allocated.
 202 */
 203static void
 204xfs_buf_free_maps(
 205	struct xfs_buf	*bp)
 206{
 207	if (bp->b_maps != &bp->__b_map) {
 208		kmem_free(bp->b_maps);
 209		bp->b_maps = NULL;
 210	}
 211}
 212
 213struct xfs_buf *
 214_xfs_buf_alloc(
 215	struct xfs_buftarg	*target,
 216	struct xfs_buf_map	*map,
 217	int			nmaps,
 218	xfs_buf_flags_t		flags)
 219{
 220	struct xfs_buf		*bp;
 221	int			error;
 222	int			i;
 223
 224	bp = kmem_zone_zalloc(xfs_buf_zone, KM_NOFS);
 225	if (unlikely(!bp))
 226		return NULL;
 227
 228	/*
 229	 * We don't want certain flags to appear in b_flags unless they are
 230	 * specifically set by later operations on the buffer.
 231	 */
 232	flags &= ~(XBF_UNMAPPED | XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD);
 233
 234	atomic_set(&bp->b_hold, 1);
 235	atomic_set(&bp->b_lru_ref, 1);
 236	init_completion(&bp->b_iowait);
 237	INIT_LIST_HEAD(&bp->b_lru);
 238	INIT_LIST_HEAD(&bp->b_list);
 239	INIT_LIST_HEAD(&bp->b_li_list);
 240	sema_init(&bp->b_sema, 0); /* held, no waiters */
 241	spin_lock_init(&bp->b_lock);
 242	XB_SET_OWNER(bp);
 243	bp->b_target = target;
 244	bp->b_flags = flags;
 245
 246	/*
 247	 * Set length and io_length to the same value initially.
 248	 * I/O routines should use io_length, which will be the same in
 249	 * most cases but may be reset (e.g. XFS recovery).
 250	 */
 251	error = xfs_buf_get_maps(bp, nmaps);
 252	if (error)  {
 253		kmem_zone_free(xfs_buf_zone, bp);
 254		return NULL;
 255	}
 256
 257	bp->b_bn = map[0].bm_bn;
 258	bp->b_length = 0;
 259	for (i = 0; i < nmaps; i++) {
 260		bp->b_maps[i].bm_bn = map[i].bm_bn;
 261		bp->b_maps[i].bm_len = map[i].bm_len;
 262		bp->b_length += map[i].bm_len;
 263	}
 264	bp->b_io_length = bp->b_length;
 265
 266	atomic_set(&bp->b_pin_count, 0);
 267	init_waitqueue_head(&bp->b_waiters);
 268
 269	XFS_STATS_INC(target->bt_mount, xb_create);
 270	trace_xfs_buf_init(bp, _RET_IP_);
 271
 272	return bp;
 273}
 274
 275/*
 276 *	Allocate a page array capable of holding a specified number
 277 *	of pages, and point the page buf at it.
 278 */
 279STATIC int
 280_xfs_buf_get_pages(
 281	xfs_buf_t		*bp,
 282	int			page_count)
 283{
 284	/* Make sure that we have a page list */
 285	if (bp->b_pages == NULL) {
 286		bp->b_page_count = page_count;
 287		if (page_count <= XB_PAGES) {
 288			bp->b_pages = bp->b_page_array;
 289		} else {
 290			bp->b_pages = kmem_alloc(sizeof(struct page *) *
 291						 page_count, KM_NOFS);
 292			if (bp->b_pages == NULL)
 293				return -ENOMEM;
 294		}
 295		memset(bp->b_pages, 0, sizeof(struct page *) * page_count);
 296	}
 297	return 0;
 298}
 299
 300/*
 301 *	Frees b_pages if it was allocated.
 302 */
 303STATIC void
 304_xfs_buf_free_pages(
 305	xfs_buf_t	*bp)
 306{
 307	if (bp->b_pages != bp->b_page_array) {
 308		kmem_free(bp->b_pages);
 309		bp->b_pages = NULL;
 310	}
 311}
 312
 313/*
 314 *	Releases the specified buffer.
 315 *
 316 * 	The modification state of any associated pages is left unchanged.
 317 * 	The buffer must not be on any hash - use xfs_buf_rele instead for
 318 * 	hashed and refcounted buffers
 319 */
 320void
 321xfs_buf_free(
 322	xfs_buf_t		*bp)
 323{
 324	trace_xfs_buf_free(bp, _RET_IP_);
 325
 326	ASSERT(list_empty(&bp->b_lru));
 327
 328	if (bp->b_flags & _XBF_PAGES) {
 329		uint		i;
 330
 331		if (xfs_buf_is_vmapped(bp))
 332			vm_unmap_ram(bp->b_addr - bp->b_offset,
 333					bp->b_page_count);
 334
 335		for (i = 0; i < bp->b_page_count; i++) {
 336			struct page	*page = bp->b_pages[i];
 337
 338			__free_page(page);
 339		}
 340	} else if (bp->b_flags & _XBF_KMEM)
 341		kmem_free(bp->b_addr);
 342	_xfs_buf_free_pages(bp);
 343	xfs_buf_free_maps(bp);
 344	kmem_zone_free(xfs_buf_zone, bp);
 345}
 346
 347/*
 348 * Allocates all the pages for buffer in question and builds it's page list.
 349 */
 350STATIC int
 351xfs_buf_allocate_memory(
 352	xfs_buf_t		*bp,
 353	uint			flags)
 354{
 355	size_t			size;
 356	size_t			nbytes, offset;
 357	gfp_t			gfp_mask = xb_to_gfp(flags);
 358	unsigned short		page_count, i;
 359	xfs_off_t		start, end;
 360	int			error;
 361
 362	/*
 363	 * for buffers that are contained within a single page, just allocate
 364	 * the memory from the heap - there's no need for the complexity of
 365	 * page arrays to keep allocation down to order 0.
 366	 */
 367	size = BBTOB(bp->b_length);
 368	if (size < PAGE_SIZE) {
 369		bp->b_addr = kmem_alloc(size, KM_NOFS);
 370		if (!bp->b_addr) {
 371			/* low memory - use alloc_page loop instead */
 372			goto use_alloc_page;
 373		}
 374
 375		if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
 376		    ((unsigned long)bp->b_addr & PAGE_MASK)) {
 377			/* b_addr spans two pages - use alloc_page instead */
 378			kmem_free(bp->b_addr);
 379			bp->b_addr = NULL;
 380			goto use_alloc_page;
 381		}
 382		bp->b_offset = offset_in_page(bp->b_addr);
 383		bp->b_pages = bp->b_page_array;
 384		bp->b_pages[0] = virt_to_page(bp->b_addr);
 385		bp->b_page_count = 1;
 386		bp->b_flags |= _XBF_KMEM;
 387		return 0;
 388	}
 389
 390use_alloc_page:
 391	start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
 392	end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
 393								>> PAGE_SHIFT;
 394	page_count = end - start;
 395	error = _xfs_buf_get_pages(bp, page_count);
 396	if (unlikely(error))
 397		return error;
 398
 399	offset = bp->b_offset;
 400	bp->b_flags |= _XBF_PAGES;
 401
 402	for (i = 0; i < bp->b_page_count; i++) {
 403		struct page	*page;
 404		uint		retries = 0;
 405retry:
 406		page = alloc_page(gfp_mask);
 407		if (unlikely(page == NULL)) {
 408			if (flags & XBF_READ_AHEAD) {
 409				bp->b_page_count = i;
 410				error = -ENOMEM;
 411				goto out_free_pages;
 412			}
 413
 414			/*
 415			 * This could deadlock.
 416			 *
 417			 * But until all the XFS lowlevel code is revamped to
 418			 * handle buffer allocation failures we can't do much.
 419			 */
 420			if (!(++retries % 100))
 421				xfs_err(NULL,
 422		"%s(%u) possible memory allocation deadlock in %s (mode:0x%x)",
 423					current->comm, current->pid,
 424					__func__, gfp_mask);
 425
 426			XFS_STATS_INC(bp->b_target->bt_mount, xb_page_retries);
 427			congestion_wait(BLK_RW_ASYNC, HZ/50);
 428			goto retry;
 429		}
 430
 431		XFS_STATS_INC(bp->b_target->bt_mount, xb_page_found);
 432
 433		nbytes = min_t(size_t, size, PAGE_SIZE - offset);
 434		size -= nbytes;
 435		bp->b_pages[i] = page;
 436		offset = 0;
 437	}
 438	return 0;
 439
 440out_free_pages:
 441	for (i = 0; i < bp->b_page_count; i++)
 442		__free_page(bp->b_pages[i]);
 443	bp->b_flags &= ~_XBF_PAGES;
 444	return error;
 445}
 446
 447/*
 448 *	Map buffer into kernel address-space if necessary.
 449 */
 450STATIC int
 451_xfs_buf_map_pages(
 452	xfs_buf_t		*bp,
 453	uint			flags)
 454{
 455	ASSERT(bp->b_flags & _XBF_PAGES);
 456	if (bp->b_page_count == 1) {
 457		/* A single page buffer is always mappable */
 458		bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
 459	} else if (flags & XBF_UNMAPPED) {
 460		bp->b_addr = NULL;
 461	} else {
 462		int retried = 0;
 463		unsigned nofs_flag;
 464
 465		/*
 466		 * vm_map_ram() will allocate auxillary structures (e.g.
 467		 * pagetables) with GFP_KERNEL, yet we are likely to be under
 468		 * GFP_NOFS context here. Hence we need to tell memory reclaim
 469		 * that we are in such a context via PF_MEMALLOC_NOFS to prevent
 470		 * memory reclaim re-entering the filesystem here and
 471		 * potentially deadlocking.
 472		 */
 473		nofs_flag = memalloc_nofs_save();
 474		do {
 475			bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
 476						-1, PAGE_KERNEL);
 477			if (bp->b_addr)
 478				break;
 479			vm_unmap_aliases();
 480		} while (retried++ <= 1);
 481		memalloc_nofs_restore(nofs_flag);
 482
 483		if (!bp->b_addr)
 484			return -ENOMEM;
 485		bp->b_addr += bp->b_offset;
 486	}
 487
 488	return 0;
 489}
 490
 491/*
 492 *	Finding and Reading Buffers
 493 */
 494static int
 495_xfs_buf_obj_cmp(
 496	struct rhashtable_compare_arg	*arg,
 497	const void			*obj)
 498{
 499	const struct xfs_buf_map	*map = arg->key;
 500	const struct xfs_buf		*bp = obj;
 501
 502	/*
 503	 * The key hashing in the lookup path depends on the key being the
 504	 * first element of the compare_arg, make sure to assert this.
 505	 */
 506	BUILD_BUG_ON(offsetof(struct xfs_buf_map, bm_bn) != 0);
 507
 508	if (bp->b_bn != map->bm_bn)
 509		return 1;
 510
 511	if (unlikely(bp->b_length != map->bm_len)) {
 512		/*
 513		 * found a block number match. If the range doesn't
 514		 * match, the only way this is allowed is if the buffer
 515		 * in the cache is stale and the transaction that made
 516		 * it stale has not yet committed. i.e. we are
 517		 * reallocating a busy extent. Skip this buffer and
 518		 * continue searching for an exact match.
 519		 */
 520		ASSERT(bp->b_flags & XBF_STALE);
 521		return 1;
 522	}
 523	return 0;
 524}
 525
 526static const struct rhashtable_params xfs_buf_hash_params = {
 527	.min_size		= 32,	/* empty AGs have minimal footprint */
 528	.nelem_hint		= 16,
 529	.key_len		= sizeof(xfs_daddr_t),
 530	.key_offset		= offsetof(struct xfs_buf, b_bn),
 531	.head_offset		= offsetof(struct xfs_buf, b_rhash_head),
 532	.automatic_shrinking	= true,
 533	.obj_cmpfn		= _xfs_buf_obj_cmp,
 534};
 535
 536int
 537xfs_buf_hash_init(
 538	struct xfs_perag	*pag)
 539{
 540	spin_lock_init(&pag->pag_buf_lock);
 541	return rhashtable_init(&pag->pag_buf_hash, &xfs_buf_hash_params);
 542}
 543
 544void
 545xfs_buf_hash_destroy(
 546	struct xfs_perag	*pag)
 547{
 548	rhashtable_destroy(&pag->pag_buf_hash);
 549}
 550
 551/*
 552 *	Look up, and creates if absent, a lockable buffer for
 553 *	a given range of an inode.  The buffer is returned
 554 *	locked.	No I/O is implied by this call.
 555 */
 556xfs_buf_t *
 557_xfs_buf_find(
 558	struct xfs_buftarg	*btp,
 559	struct xfs_buf_map	*map,
 560	int			nmaps,
 561	xfs_buf_flags_t		flags,
 562	xfs_buf_t		*new_bp)
 563{
 564	struct xfs_perag	*pag;
 565	xfs_buf_t		*bp;
 566	struct xfs_buf_map	cmap = { .bm_bn = map[0].bm_bn };
 567	xfs_daddr_t		eofs;
 568	int			i;
 569
 570	for (i = 0; i < nmaps; i++)
 571		cmap.bm_len += map[i].bm_len;
 572
 573	/* Check for IOs smaller than the sector size / not sector aligned */
 574	ASSERT(!(BBTOB(cmap.bm_len) < btp->bt_meta_sectorsize));
 575	ASSERT(!(BBTOB(cmap.bm_bn) & (xfs_off_t)btp->bt_meta_sectormask));
 576
 577	/*
 578	 * Corrupted block numbers can get through to here, unfortunately, so we
 579	 * have to check that the buffer falls within the filesystem bounds.
 580	 */
 581	eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
 582	if (cmap.bm_bn < 0 || cmap.bm_bn >= eofs) {
 583		/*
 584		 * XXX (dgc): we should really be returning -EFSCORRUPTED here,
 585		 * but none of the higher level infrastructure supports
 586		 * returning a specific error on buffer lookup failures.
 587		 */
 588		xfs_alert(btp->bt_mount,
 589			  "%s: daddr 0x%llx out of range, EOFS 0x%llx",
 590			  __func__, cmap.bm_bn, eofs);
 591		WARN_ON(1);
 592		return NULL;
 593	}
 594
 595	pag = xfs_perag_get(btp->bt_mount,
 596			    xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
 597
 598	spin_lock(&pag->pag_buf_lock);
 599	bp = rhashtable_lookup_fast(&pag->pag_buf_hash, &cmap,
 600				    xfs_buf_hash_params);
 601	if (bp) {
 602		atomic_inc(&bp->b_hold);
 603		goto found;
 604	}
 605
 606	/* No match found */
 607	if (new_bp) {
 608		/* the buffer keeps the perag reference until it is freed */
 609		new_bp->b_pag = pag;
 610		rhashtable_insert_fast(&pag->pag_buf_hash,
 611				       &new_bp->b_rhash_head,
 612				       xfs_buf_hash_params);
 613		spin_unlock(&pag->pag_buf_lock);
 614	} else {
 615		XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
 616		spin_unlock(&pag->pag_buf_lock);
 617		xfs_perag_put(pag);
 618	}
 619	return new_bp;
 620
 621found:
 622	spin_unlock(&pag->pag_buf_lock);
 623	xfs_perag_put(pag);
 624
 625	if (!xfs_buf_trylock(bp)) {
 626		if (flags & XBF_TRYLOCK) {
 627			xfs_buf_rele(bp);
 628			XFS_STATS_INC(btp->bt_mount, xb_busy_locked);
 629			return NULL;
 630		}
 631		xfs_buf_lock(bp);
 632		XFS_STATS_INC(btp->bt_mount, xb_get_locked_waited);
 633	}
 634
 635	/*
 636	 * if the buffer is stale, clear all the external state associated with
 637	 * it. We need to keep flags such as how we allocated the buffer memory
 638	 * intact here.
 639	 */
 640	if (bp->b_flags & XBF_STALE) {
 641		ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
 642		ASSERT(bp->b_iodone == NULL);
 643		bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
 644		bp->b_ops = NULL;
 645	}
 646
 647	trace_xfs_buf_find(bp, flags, _RET_IP_);
 648	XFS_STATS_INC(btp->bt_mount, xb_get_locked);
 649	return bp;
 650}
 651
 652/*
 653 * Assembles a buffer covering the specified range. The code is optimised for
 654 * cache hits, as metadata intensive workloads will see 3 orders of magnitude
 655 * more hits than misses.
 656 */
 657struct xfs_buf *
 658xfs_buf_get_map(
 659	struct xfs_buftarg	*target,
 660	struct xfs_buf_map	*map,
 661	int			nmaps,
 662	xfs_buf_flags_t		flags)
 663{
 664	struct xfs_buf		*bp;
 665	struct xfs_buf		*new_bp;
 666	int			error = 0;
 667
 668	bp = _xfs_buf_find(target, map, nmaps, flags, NULL);
 669	if (likely(bp))
 670		goto found;
 671
 672	new_bp = _xfs_buf_alloc(target, map, nmaps, flags);
 673	if (unlikely(!new_bp))
 674		return NULL;
 675
 676	error = xfs_buf_allocate_memory(new_bp, flags);
 677	if (error) {
 678		xfs_buf_free(new_bp);
 679		return NULL;
 680	}
 681
 682	bp = _xfs_buf_find(target, map, nmaps, flags, new_bp);
 683	if (!bp) {
 684		xfs_buf_free(new_bp);
 685		return NULL;
 686	}
 687
 688	if (bp != new_bp)
 689		xfs_buf_free(new_bp);
 690
 691found:
 692	if (!bp->b_addr) {
 693		error = _xfs_buf_map_pages(bp, flags);
 694		if (unlikely(error)) {
 695			xfs_warn(target->bt_mount,
 696				"%s: failed to map pagesn", __func__);
 697			xfs_buf_relse(bp);
 698			return NULL;
 699		}
 700	}
 701
 702	/*
 703	 * Clear b_error if this is a lookup from a caller that doesn't expect
 704	 * valid data to be found in the buffer.
 705	 */
 706	if (!(flags & XBF_READ))
 707		xfs_buf_ioerror(bp, 0);
 708
 709	XFS_STATS_INC(target->bt_mount, xb_get);
 710	trace_xfs_buf_get(bp, flags, _RET_IP_);
 711	return bp;
 712}
 713
 714STATIC int
 715_xfs_buf_read(
 716	xfs_buf_t		*bp,
 717	xfs_buf_flags_t		flags)
 718{
 719	ASSERT(!(flags & XBF_WRITE));
 720	ASSERT(bp->b_maps[0].bm_bn != XFS_BUF_DADDR_NULL);
 721
 722	bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
 723	bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
 724
 725	if (flags & XBF_ASYNC) {
 726		xfs_buf_submit(bp);
 727		return 0;
 728	}
 729	return xfs_buf_submit_wait(bp);
 730}
 731
 732xfs_buf_t *
 733xfs_buf_read_map(
 734	struct xfs_buftarg	*target,
 735	struct xfs_buf_map	*map,
 736	int			nmaps,
 737	xfs_buf_flags_t		flags,
 738	const struct xfs_buf_ops *ops)
 739{
 740	struct xfs_buf		*bp;
 741
 742	flags |= XBF_READ;
 743
 744	bp = xfs_buf_get_map(target, map, nmaps, flags);
 745	if (bp) {
 746		trace_xfs_buf_read(bp, flags, _RET_IP_);
 747
 748		if (!(bp->b_flags & XBF_DONE)) {
 749			XFS_STATS_INC(target->bt_mount, xb_get_read);
 750			bp->b_ops = ops;
 751			_xfs_buf_read(bp, flags);
 752		} else if (flags & XBF_ASYNC) {
 753			/*
 754			 * Read ahead call which is already satisfied,
 755			 * drop the buffer
 756			 */
 757			xfs_buf_relse(bp);
 758			return NULL;
 759		} else {
 760			/* We do not want read in the flags */
 761			bp->b_flags &= ~XBF_READ;
 762		}
 763	}
 764
 765	return bp;
 766}
 767
 768/*
 769 *	If we are not low on memory then do the readahead in a deadlock
 770 *	safe manner.
 771 */
 772void
 773xfs_buf_readahead_map(
 774	struct xfs_buftarg	*target,
 775	struct xfs_buf_map	*map,
 776	int			nmaps,
 777	const struct xfs_buf_ops *ops)
 778{
 779	if (bdi_read_congested(target->bt_bdev->bd_bdi))
 780		return;
 781
 782	xfs_buf_read_map(target, map, nmaps,
 783		     XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD, ops);
 784}
 785
 786/*
 787 * Read an uncached buffer from disk. Allocates and returns a locked
 788 * buffer containing the disk contents or nothing.
 789 */
 790int
 791xfs_buf_read_uncached(
 792	struct xfs_buftarg	*target,
 793	xfs_daddr_t		daddr,
 794	size_t			numblks,
 795	int			flags,
 796	struct xfs_buf		**bpp,
 797	const struct xfs_buf_ops *ops)
 798{
 799	struct xfs_buf		*bp;
 800
 801	*bpp = NULL;
 802
 803	bp = xfs_buf_get_uncached(target, numblks, flags);
 804	if (!bp)
 805		return -ENOMEM;
 806
 807	/* set up the buffer for a read IO */
 808	ASSERT(bp->b_map_count == 1);
 809	bp->b_bn = XFS_BUF_DADDR_NULL;  /* always null for uncached buffers */
 810	bp->b_maps[0].bm_bn = daddr;
 811	bp->b_flags |= XBF_READ;
 812	bp->b_ops = ops;
 813
 814	xfs_buf_submit_wait(bp);
 815	if (bp->b_error) {
 816		int	error = bp->b_error;
 817		xfs_buf_relse(bp);
 818		return error;
 819	}
 820
 821	*bpp = bp;
 822	return 0;
 823}
 824
 825/*
 826 * Return a buffer allocated as an empty buffer and associated to external
 827 * memory via xfs_buf_associate_memory() back to it's empty state.
 828 */
 829void
 830xfs_buf_set_empty(
 831	struct xfs_buf		*bp,
 832	size_t			numblks)
 833{
 834	if (bp->b_pages)
 835		_xfs_buf_free_pages(bp);
 836
 837	bp->b_pages = NULL;
 838	bp->b_page_count = 0;
 839	bp->b_addr = NULL;
 840	bp->b_length = numblks;
 841	bp->b_io_length = numblks;
 842
 843	ASSERT(bp->b_map_count == 1);
 844	bp->b_bn = XFS_BUF_DADDR_NULL;
 845	bp->b_maps[0].bm_bn = XFS_BUF_DADDR_NULL;
 846	bp->b_maps[0].bm_len = bp->b_length;
 847}
 848
 849static inline struct page *
 850mem_to_page(
 851	void			*addr)
 852{
 853	if ((!is_vmalloc_addr(addr))) {
 854		return virt_to_page(addr);
 855	} else {
 856		return vmalloc_to_page(addr);
 857	}
 858}
 859
 860int
 861xfs_buf_associate_memory(
 862	xfs_buf_t		*bp,
 863	void			*mem,
 864	size_t			len)
 865{
 866	int			rval;
 867	int			i = 0;
 868	unsigned long		pageaddr;
 869	unsigned long		offset;
 870	size_t			buflen;
 871	int			page_count;
 872
 873	pageaddr = (unsigned long)mem & PAGE_MASK;
 874	offset = (unsigned long)mem - pageaddr;
 875	buflen = PAGE_ALIGN(len + offset);
 876	page_count = buflen >> PAGE_SHIFT;
 877
 878	/* Free any previous set of page pointers */
 879	if (bp->b_pages)
 880		_xfs_buf_free_pages(bp);
 881
 882	bp->b_pages = NULL;
 883	bp->b_addr = mem;
 884
 885	rval = _xfs_buf_get_pages(bp, page_count);
 886	if (rval)
 887		return rval;
 888
 889	bp->b_offset = offset;
 890
 891	for (i = 0; i < bp->b_page_count; i++) {
 892		bp->b_pages[i] = mem_to_page((void *)pageaddr);
 893		pageaddr += PAGE_SIZE;
 894	}
 895
 896	bp->b_io_length = BTOBB(len);
 897	bp->b_length = BTOBB(buflen);
 898
 899	return 0;
 900}
 901
 902xfs_buf_t *
 903xfs_buf_get_uncached(
 904	struct xfs_buftarg	*target,
 905	size_t			numblks,
 906	int			flags)
 907{
 908	unsigned long		page_count;
 909	int			error, i;
 910	struct xfs_buf		*bp;
 911	DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
 912
 913	/* flags might contain irrelevant bits, pass only what we care about */
 914	bp = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT);
 915	if (unlikely(bp == NULL))
 916		goto fail;
 917
 918	page_count = PAGE_ALIGN(numblks << BBSHIFT) >> PAGE_SHIFT;
 919	error = _xfs_buf_get_pages(bp, page_count);
 920	if (error)
 921		goto fail_free_buf;
 922
 923	for (i = 0; i < page_count; i++) {
 924		bp->b_pages[i] = alloc_page(xb_to_gfp(flags));
 925		if (!bp->b_pages[i])
 926			goto fail_free_mem;
 927	}
 928	bp->b_flags |= _XBF_PAGES;
 929
 930	error = _xfs_buf_map_pages(bp, 0);
 931	if (unlikely(error)) {
 932		xfs_warn(target->bt_mount,
 933			"%s: failed to map pages", __func__);
 934		goto fail_free_mem;
 935	}
 936
 937	trace_xfs_buf_get_uncached(bp, _RET_IP_);
 938	return bp;
 939
 940 fail_free_mem:
 941	while (--i >= 0)
 942		__free_page(bp->b_pages[i]);
 943	_xfs_buf_free_pages(bp);
 944 fail_free_buf:
 945	xfs_buf_free_maps(bp);
 946	kmem_zone_free(xfs_buf_zone, bp);
 947 fail:
 948	return NULL;
 949}
 950
 951/*
 952 *	Increment reference count on buffer, to hold the buffer concurrently
 953 *	with another thread which may release (free) the buffer asynchronously.
 954 *	Must hold the buffer already to call this function.
 955 */
 956void
 957xfs_buf_hold(
 958	xfs_buf_t		*bp)
 959{
 960	trace_xfs_buf_hold(bp, _RET_IP_);
 961	atomic_inc(&bp->b_hold);
 962}
 963
 964/*
 965 * Release a hold on the specified buffer. If the hold count is 1, the buffer is
 966 * placed on LRU or freed (depending on b_lru_ref).
 967 */
 968void
 969xfs_buf_rele(
 970	xfs_buf_t		*bp)
 971{
 972	struct xfs_perag	*pag = bp->b_pag;
 973	bool			release;
 974	bool			freebuf = false;
 975
 976	trace_xfs_buf_rele(bp, _RET_IP_);
 977
 978	if (!pag) {
 979		ASSERT(list_empty(&bp->b_lru));
 980		if (atomic_dec_and_test(&bp->b_hold)) {
 981			xfs_buf_ioacct_dec(bp);
 982			xfs_buf_free(bp);
 983		}
 984		return;
 985	}
 986
 987	ASSERT(atomic_read(&bp->b_hold) > 0);
 988
 989	release = atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock);
 990	spin_lock(&bp->b_lock);
 991	if (!release) {
 992		/*
 993		 * Drop the in-flight state if the buffer is already on the LRU
 994		 * and it holds the only reference. This is racy because we
 995		 * haven't acquired the pag lock, but the use of _XBF_IN_FLIGHT
 996		 * ensures the decrement occurs only once per-buf.
 997		 */
 998		if ((atomic_read(&bp->b_hold) == 1) && !list_empty(&bp->b_lru))
 999			__xfs_buf_ioacct_dec(bp);
1000		goto out_unlock;
1001	}
1002
1003	/* the last reference has been dropped ... */
1004	__xfs_buf_ioacct_dec(bp);
1005	if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
1006		/*
1007		 * If the buffer is added to the LRU take a new reference to the
1008		 * buffer for the LRU and clear the (now stale) dispose list
1009		 * state flag
1010		 */
1011		if (list_lru_add(&bp->b_target->bt_lru, &bp->b_lru)) {
1012			bp->b_state &= ~XFS_BSTATE_DISPOSE;
1013			atomic_inc(&bp->b_hold);
1014		}
1015		spin_unlock(&pag->pag_buf_lock);
1016	} else {
1017		/*
1018		 * most of the time buffers will already be removed from the
1019		 * LRU, so optimise that case by checking for the
1020		 * XFS_BSTATE_DISPOSE flag indicating the last list the buffer
1021		 * was on was the disposal list
1022		 */
1023		if (!(bp->b_state & XFS_BSTATE_DISPOSE)) {
1024			list_lru_del(&bp->b_target->bt_lru, &bp->b_lru);
1025		} else {
1026			ASSERT(list_empty(&bp->b_lru));
1027		}
1028
1029		ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1030		rhashtable_remove_fast(&pag->pag_buf_hash, &bp->b_rhash_head,
1031				       xfs_buf_hash_params);
1032		spin_unlock(&pag->pag_buf_lock);
1033		xfs_perag_put(pag);
1034		freebuf = true;
1035	}
1036
1037out_unlock:
1038	spin_unlock(&bp->b_lock);
1039
1040	if (freebuf)
1041		xfs_buf_free(bp);
1042}
1043
1044
1045/*
1046 *	Lock a buffer object, if it is not already locked.
1047 *
1048 *	If we come across a stale, pinned, locked buffer, we know that we are
1049 *	being asked to lock a buffer that has been reallocated. Because it is
1050 *	pinned, we know that the log has not been pushed to disk and hence it
1051 *	will still be locked.  Rather than continuing to have trylock attempts
1052 *	fail until someone else pushes the log, push it ourselves before
1053 *	returning.  This means that the xfsaild will not get stuck trying
1054 *	to push on stale inode buffers.
1055 */
1056int
1057xfs_buf_trylock(
1058	struct xfs_buf		*bp)
1059{
1060	int			locked;
1061
1062	locked = down_trylock(&bp->b_sema) == 0;
1063	if (locked) {
1064		XB_SET_OWNER(bp);
1065		trace_xfs_buf_trylock(bp, _RET_IP_);
1066	} else {
1067		trace_xfs_buf_trylock_fail(bp, _RET_IP_);
1068	}
1069	return locked;
1070}
1071
1072/*
1073 *	Lock a buffer object.
1074 *
1075 *	If we come across a stale, pinned, locked buffer, we know that we
1076 *	are being asked to lock a buffer that has been reallocated. Because
1077 *	it is pinned, we know that the log has not been pushed to disk and
1078 *	hence it will still be locked. Rather than sleeping until someone
1079 *	else pushes the log, push it ourselves before trying to get the lock.
1080 */
1081void
1082xfs_buf_lock(
1083	struct xfs_buf		*bp)
1084{
1085	trace_xfs_buf_lock(bp, _RET_IP_);
1086
1087	if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
1088		xfs_log_force(bp->b_target->bt_mount, 0);
1089	down(&bp->b_sema);
1090	XB_SET_OWNER(bp);
1091
1092	trace_xfs_buf_lock_done(bp, _RET_IP_);
1093}
1094
1095void
1096xfs_buf_unlock(
1097	struct xfs_buf		*bp)
1098{
1099	ASSERT(xfs_buf_islocked(bp));
1100
1101	XB_CLEAR_OWNER(bp);
1102	up(&bp->b_sema);
1103
1104	trace_xfs_buf_unlock(bp, _RET_IP_);
1105}
1106
1107STATIC void
1108xfs_buf_wait_unpin(
1109	xfs_buf_t		*bp)
1110{
1111	DECLARE_WAITQUEUE	(wait, current);
1112
1113	if (atomic_read(&bp->b_pin_count) == 0)
1114		return;
1115
1116	add_wait_queue(&bp->b_waiters, &wait);
1117	for (;;) {
1118		set_current_state(TASK_UNINTERRUPTIBLE);
1119		if (atomic_read(&bp->b_pin_count) == 0)
1120			break;
1121		io_schedule();
1122	}
1123	remove_wait_queue(&bp->b_waiters, &wait);
1124	set_current_state(TASK_RUNNING);
1125}
1126
1127/*
1128 *	Buffer Utility Routines
1129 */
1130
1131void
1132xfs_buf_ioend(
1133	struct xfs_buf	*bp)
1134{
1135	bool		read = bp->b_flags & XBF_READ;
1136
1137	trace_xfs_buf_iodone(bp, _RET_IP_);
1138
1139	bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
1140
1141	/*
1142	 * Pull in IO completion errors now. We are guaranteed to be running
1143	 * single threaded, so we don't need the lock to read b_io_error.
1144	 */
1145	if (!bp->b_error && bp->b_io_error)
1146		xfs_buf_ioerror(bp, bp->b_io_error);
1147
1148	/* Only validate buffers that were read without errors */
1149	if (read && !bp->b_error && bp->b_ops) {
1150		ASSERT(!bp->b_iodone);
1151		bp->b_ops->verify_read(bp);
1152	}
1153
1154	if (!bp->b_error)
1155		bp->b_flags |= XBF_DONE;
1156
1157	if (bp->b_iodone)
1158		(*(bp->b_iodone))(bp);
1159	else if (bp->b_flags & XBF_ASYNC)
1160		xfs_buf_relse(bp);
1161	else
1162		complete(&bp->b_iowait);
1163}
1164
1165static void
1166xfs_buf_ioend_work(
1167	struct work_struct	*work)
1168{
1169	struct xfs_buf		*bp =
1170		container_of(work, xfs_buf_t, b_ioend_work);
1171
1172	xfs_buf_ioend(bp);
1173}
1174
1175static void
1176xfs_buf_ioend_async(
1177	struct xfs_buf	*bp)
1178{
1179	INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work);
1180	queue_work(bp->b_ioend_wq, &bp->b_ioend_work);
1181}
1182
1183void
1184__xfs_buf_ioerror(
1185	xfs_buf_t		*bp,
1186	int			error,
1187	xfs_failaddr_t		failaddr)
1188{
1189	ASSERT(error <= 0 && error >= -1000);
1190	bp->b_error = error;
1191	trace_xfs_buf_ioerror(bp, error, failaddr);
1192}
1193
1194void
1195xfs_buf_ioerror_alert(
1196	struct xfs_buf		*bp,
1197	const char		*func)
1198{
1199	xfs_alert(bp->b_target->bt_mount,
1200"metadata I/O error in \"%s\" at daddr 0x%llx len %d error %d",
1201			func, (uint64_t)XFS_BUF_ADDR(bp), bp->b_length,
1202			-bp->b_error);
1203}
1204
1205int
1206xfs_bwrite(
1207	struct xfs_buf		*bp)
1208{
1209	int			error;
1210
1211	ASSERT(xfs_buf_islocked(bp));
1212
1213	bp->b_flags |= XBF_WRITE;
1214	bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q |
1215			 XBF_WRITE_FAIL | XBF_DONE);
1216
1217	error = xfs_buf_submit_wait(bp);
1218	if (error) {
1219		xfs_force_shutdown(bp->b_target->bt_mount,
1220				   SHUTDOWN_META_IO_ERROR);
1221	}
1222	return error;
1223}
1224
1225static void
1226xfs_buf_bio_end_io(
1227	struct bio		*bio)
1228{
1229	struct xfs_buf		*bp = (struct xfs_buf *)bio->bi_private;
1230
1231	/*
1232	 * don't overwrite existing errors - otherwise we can lose errors on
1233	 * buffers that require multiple bios to complete.
1234	 */
1235	if (bio->bi_status) {
1236		int error = blk_status_to_errno(bio->bi_status);
1237
1238		cmpxchg(&bp->b_io_error, 0, error);
1239	}
1240
1241	if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
1242		invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
1243
1244	if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
1245		xfs_buf_ioend_async(bp);
1246	bio_put(bio);
1247}
1248
1249static void
1250xfs_buf_ioapply_map(
1251	struct xfs_buf	*bp,
1252	int		map,
1253	int		*buf_offset,
1254	int		*count,
1255	int		op,
1256	int		op_flags)
1257{
1258	int		page_index;
1259	int		total_nr_pages = bp->b_page_count;
1260	int		nr_pages;
1261	struct bio	*bio;
1262	sector_t	sector =  bp->b_maps[map].bm_bn;
1263	int		size;
1264	int		offset;
1265
 
 
1266	/* skip the pages in the buffer before the start offset */
1267	page_index = 0;
1268	offset = *buf_offset;
1269	while (offset >= PAGE_SIZE) {
1270		page_index++;
1271		offset -= PAGE_SIZE;
1272	}
1273
1274	/*
1275	 * Limit the IO size to the length of the current vector, and update the
1276	 * remaining IO count for the next time around.
1277	 */
1278	size = min_t(int, BBTOB(bp->b_maps[map].bm_len), *count);
1279	*count -= size;
1280	*buf_offset += size;
1281
1282next_chunk:
1283	atomic_inc(&bp->b_io_remaining);
1284	nr_pages = min(total_nr_pages, BIO_MAX_PAGES);
1285
1286	bio = bio_alloc(GFP_NOIO, nr_pages);
1287	bio_set_dev(bio, bp->b_target->bt_bdev);
1288	bio->bi_iter.bi_sector = sector;
1289	bio->bi_end_io = xfs_buf_bio_end_io;
1290	bio->bi_private = bp;
1291	bio_set_op_attrs(bio, op, op_flags);
1292
1293	for (; size && nr_pages; nr_pages--, page_index++) {
1294		int	rbytes, nbytes = PAGE_SIZE - offset;
1295
1296		if (nbytes > size)
1297			nbytes = size;
1298
1299		rbytes = bio_add_page(bio, bp->b_pages[page_index], nbytes,
1300				      offset);
1301		if (rbytes < nbytes)
1302			break;
1303
1304		offset = 0;
1305		sector += BTOBB(nbytes);
1306		size -= nbytes;
1307		total_nr_pages--;
1308	}
1309
1310	if (likely(bio->bi_iter.bi_size)) {
1311		if (xfs_buf_is_vmapped(bp)) {
1312			flush_kernel_vmap_range(bp->b_addr,
1313						xfs_buf_vmap_len(bp));
1314		}
1315		submit_bio(bio);
1316		if (size)
1317			goto next_chunk;
1318	} else {
1319		/*
1320		 * This is guaranteed not to be the last io reference count
1321		 * because the caller (xfs_buf_submit) holds a count itself.
1322		 */
1323		atomic_dec(&bp->b_io_remaining);
1324		xfs_buf_ioerror(bp, -EIO);
1325		bio_put(bio);
1326	}
1327
1328}
1329
1330STATIC void
1331_xfs_buf_ioapply(
1332	struct xfs_buf	*bp)
1333{
1334	struct blk_plug	plug;
1335	int		op;
1336	int		op_flags = 0;
1337	int		offset;
1338	int		size;
1339	int		i;
1340
1341	/*
1342	 * Make sure we capture only current IO errors rather than stale errors
1343	 * left over from previous use of the buffer (e.g. failed readahead).
1344	 */
1345	bp->b_error = 0;
1346
1347	/*
1348	 * Initialize the I/O completion workqueue if we haven't yet or the
1349	 * submitter has not opted to specify a custom one.
1350	 */
1351	if (!bp->b_ioend_wq)
1352		bp->b_ioend_wq = bp->b_target->bt_mount->m_buf_workqueue;
1353
1354	if (bp->b_flags & XBF_WRITE) {
1355		op = REQ_OP_WRITE;
1356		if (bp->b_flags & XBF_SYNCIO)
1357			op_flags = REQ_SYNC;
1358		if (bp->b_flags & XBF_FUA)
1359			op_flags |= REQ_FUA;
1360		if (bp->b_flags & XBF_FLUSH)
1361			op_flags |= REQ_PREFLUSH;
1362
1363		/*
1364		 * Run the write verifier callback function if it exists. If
1365		 * this function fails it will mark the buffer with an error and
1366		 * the IO should not be dispatched.
1367		 */
1368		if (bp->b_ops) {
1369			bp->b_ops->verify_write(bp);
1370			if (bp->b_error) {
1371				xfs_force_shutdown(bp->b_target->bt_mount,
1372						   SHUTDOWN_CORRUPT_INCORE);
1373				return;
1374			}
1375		} else if (bp->b_bn != XFS_BUF_DADDR_NULL) {
1376			struct xfs_mount *mp = bp->b_target->bt_mount;
1377
1378			/*
1379			 * non-crc filesystems don't attach verifiers during
1380			 * log recovery, so don't warn for such filesystems.
1381			 */
1382			if (xfs_sb_version_hascrc(&mp->m_sb)) {
1383				xfs_warn(mp,
1384					"%s: no buf ops on daddr 0x%llx len %d",
1385					__func__, bp->b_bn, bp->b_length);
1386				xfs_hex_dump(bp->b_addr,
1387						XFS_CORRUPTION_DUMP_LEN);
1388				dump_stack();
1389			}
1390		}
1391	} else if (bp->b_flags & XBF_READ_AHEAD) {
1392		op = REQ_OP_READ;
1393		op_flags = REQ_RAHEAD;
1394	} else {
1395		op = REQ_OP_READ;
1396	}
1397
1398	/* we only use the buffer cache for meta-data */
1399	op_flags |= REQ_META;
1400
1401	/*
1402	 * Walk all the vectors issuing IO on them. Set up the initial offset
1403	 * into the buffer and the desired IO size before we start -
1404	 * _xfs_buf_ioapply_vec() will modify them appropriately for each
1405	 * subsequent call.
1406	 */
1407	offset = bp->b_offset;
1408	size = BBTOB(bp->b_io_length);
1409	blk_start_plug(&plug);
1410	for (i = 0; i < bp->b_map_count; i++) {
1411		xfs_buf_ioapply_map(bp, i, &offset, &size, op, op_flags);
1412		if (bp->b_error)
1413			break;
1414		if (size <= 0)
1415			break;	/* all done */
1416	}
1417	blk_finish_plug(&plug);
1418}
1419
1420/*
1421 * Asynchronous IO submission path. This transfers the buffer lock ownership and
1422 * the current reference to the IO. It is not safe to reference the buffer after
1423 * a call to this function unless the caller holds an additional reference
1424 * itself.
1425 */
1426void
1427xfs_buf_submit(
1428	struct xfs_buf	*bp)
1429{
1430	trace_xfs_buf_submit(bp, _RET_IP_);
1431
1432	ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1433	ASSERT(bp->b_flags & XBF_ASYNC);
1434
1435	/* on shutdown we stale and complete the buffer immediately */
1436	if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
1437		xfs_buf_ioerror(bp, -EIO);
1438		bp->b_flags &= ~XBF_DONE;
1439		xfs_buf_stale(bp);
1440		xfs_buf_ioend(bp);
1441		return;
1442	}
1443
1444	if (bp->b_flags & XBF_WRITE)
1445		xfs_buf_wait_unpin(bp);
1446
1447	/* clear the internal error state to avoid spurious errors */
1448	bp->b_io_error = 0;
1449
1450	/*
1451	 * The caller's reference is released during I/O completion.
1452	 * This occurs some time after the last b_io_remaining reference is
1453	 * released, so after we drop our Io reference we have to have some
1454	 * other reference to ensure the buffer doesn't go away from underneath
1455	 * us. Take a direct reference to ensure we have safe access to the
1456	 * buffer until we are finished with it.
1457	 */
1458	xfs_buf_hold(bp);
1459
1460	/*
1461	 * Set the count to 1 initially, this will stop an I/O completion
1462	 * callout which happens before we have started all the I/O from calling
1463	 * xfs_buf_ioend too early.
1464	 */
1465	atomic_set(&bp->b_io_remaining, 1);
1466	xfs_buf_ioacct_inc(bp);
1467	_xfs_buf_ioapply(bp);
1468
1469	/*
1470	 * If _xfs_buf_ioapply failed, we can get back here with only the IO
1471	 * reference we took above. If we drop it to zero, run completion so
1472	 * that we don't return to the caller with completion still pending.
1473	 */
1474	if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
1475		if (bp->b_error)
1476			xfs_buf_ioend(bp);
1477		else
1478			xfs_buf_ioend_async(bp);
1479	}
1480
1481	xfs_buf_rele(bp);
1482	/* Note: it is not safe to reference bp now we've dropped our ref */
1483}
1484
1485/*
1486 * Synchronous buffer IO submission path, read or write.
1487 */
1488int
1489xfs_buf_submit_wait(
1490	struct xfs_buf	*bp)
1491{
1492	int		error;
1493
1494	trace_xfs_buf_submit_wait(bp, _RET_IP_);
1495
1496	ASSERT(!(bp->b_flags & (_XBF_DELWRI_Q | XBF_ASYNC)));
1497
1498	if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
1499		xfs_buf_ioerror(bp, -EIO);
1500		xfs_buf_stale(bp);
1501		bp->b_flags &= ~XBF_DONE;
1502		return -EIO;
1503	}
1504
1505	if (bp->b_flags & XBF_WRITE)
1506		xfs_buf_wait_unpin(bp);
1507
1508	/* clear the internal error state to avoid spurious errors */
1509	bp->b_io_error = 0;
1510
1511	/*
1512	 * For synchronous IO, the IO does not inherit the submitters reference
1513	 * count, nor the buffer lock. Hence we cannot release the reference we
1514	 * are about to take until we've waited for all IO completion to occur,
1515	 * including any xfs_buf_ioend_async() work that may be pending.
1516	 */
1517	xfs_buf_hold(bp);
1518
1519	/*
1520	 * Set the count to 1 initially, this will stop an I/O completion
1521	 * callout which happens before we have started all the I/O from calling
1522	 * xfs_buf_ioend too early.
1523	 */
1524	atomic_set(&bp->b_io_remaining, 1);
1525	_xfs_buf_ioapply(bp);
1526
1527	/*
1528	 * make sure we run completion synchronously if it raced with us and is
1529	 * already complete.
1530	 */
1531	if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
1532		xfs_buf_ioend(bp);
1533
1534	/* wait for completion before gathering the error from the buffer */
1535	trace_xfs_buf_iowait(bp, _RET_IP_);
1536	wait_for_completion(&bp->b_iowait);
1537	trace_xfs_buf_iowait_done(bp, _RET_IP_);
1538	error = bp->b_error;
1539
1540	/*
1541	 * all done now, we can release the hold that keeps the buffer
1542	 * referenced for the entire IO.
1543	 */
1544	xfs_buf_rele(bp);
1545	return error;
1546}
1547
1548void *
1549xfs_buf_offset(
1550	struct xfs_buf		*bp,
1551	size_t			offset)
1552{
1553	struct page		*page;
1554
1555	if (bp->b_addr)
1556		return bp->b_addr + offset;
1557
1558	offset += bp->b_offset;
1559	page = bp->b_pages[offset >> PAGE_SHIFT];
1560	return page_address(page) + (offset & (PAGE_SIZE-1));
1561}
1562
1563/*
1564 *	Move data into or out of a buffer.
1565 */
1566void
1567xfs_buf_iomove(
1568	xfs_buf_t		*bp,	/* buffer to process		*/
1569	size_t			boff,	/* starting buffer offset	*/
1570	size_t			bsize,	/* length to copy		*/
1571	void			*data,	/* data address			*/
1572	xfs_buf_rw_t		mode)	/* read/write/zero flag		*/
1573{
1574	size_t			bend;
1575
1576	bend = boff + bsize;
1577	while (boff < bend) {
1578		struct page	*page;
1579		int		page_index, page_offset, csize;
1580
1581		page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
1582		page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
1583		page = bp->b_pages[page_index];
1584		csize = min_t(size_t, PAGE_SIZE - page_offset,
1585				      BBTOB(bp->b_io_length) - boff);
1586
1587		ASSERT((csize + page_offset) <= PAGE_SIZE);
1588
1589		switch (mode) {
1590		case XBRW_ZERO:
1591			memset(page_address(page) + page_offset, 0, csize);
1592			break;
1593		case XBRW_READ:
1594			memcpy(data, page_address(page) + page_offset, csize);
1595			break;
1596		case XBRW_WRITE:
1597			memcpy(page_address(page) + page_offset, data, csize);
1598		}
1599
1600		boff += csize;
1601		data += csize;
1602	}
1603}
1604
1605/*
1606 *	Handling of buffer targets (buftargs).
1607 */
1608
1609/*
1610 * Wait for any bufs with callbacks that have been submitted but have not yet
1611 * returned. These buffers will have an elevated hold count, so wait on those
1612 * while freeing all the buffers only held by the LRU.
1613 */
1614static enum lru_status
1615xfs_buftarg_wait_rele(
1616	struct list_head	*item,
1617	struct list_lru_one	*lru,
1618	spinlock_t		*lru_lock,
1619	void			*arg)
1620
1621{
1622	struct xfs_buf		*bp = container_of(item, struct xfs_buf, b_lru);
1623	struct list_head	*dispose = arg;
1624
1625	if (atomic_read(&bp->b_hold) > 1) {
1626		/* need to wait, so skip it this pass */
1627		trace_xfs_buf_wait_buftarg(bp, _RET_IP_);
1628		return LRU_SKIP;
1629	}
1630	if (!spin_trylock(&bp->b_lock))
1631		return LRU_SKIP;
1632
1633	/*
1634	 * clear the LRU reference count so the buffer doesn't get
1635	 * ignored in xfs_buf_rele().
1636	 */
1637	atomic_set(&bp->b_lru_ref, 0);
1638	bp->b_state |= XFS_BSTATE_DISPOSE;
1639	list_lru_isolate_move(lru, item, dispose);
1640	spin_unlock(&bp->b_lock);
1641	return LRU_REMOVED;
1642}
1643
1644void
1645xfs_wait_buftarg(
1646	struct xfs_buftarg	*btp)
1647{
1648	LIST_HEAD(dispose);
1649	int loop = 0;
1650
1651	/*
1652	 * First wait on the buftarg I/O count for all in-flight buffers to be
1653	 * released. This is critical as new buffers do not make the LRU until
1654	 * they are released.
1655	 *
1656	 * Next, flush the buffer workqueue to ensure all completion processing
1657	 * has finished. Just waiting on buffer locks is not sufficient for
1658	 * async IO as the reference count held over IO is not released until
1659	 * after the buffer lock is dropped. Hence we need to ensure here that
1660	 * all reference counts have been dropped before we start walking the
1661	 * LRU list.
1662	 */
1663	while (percpu_counter_sum(&btp->bt_io_count))
1664		delay(100);
1665	flush_workqueue(btp->bt_mount->m_buf_workqueue);
1666
1667	/* loop until there is nothing left on the lru list. */
1668	while (list_lru_count(&btp->bt_lru)) {
1669		list_lru_walk(&btp->bt_lru, xfs_buftarg_wait_rele,
1670			      &dispose, LONG_MAX);
1671
1672		while (!list_empty(&dispose)) {
1673			struct xfs_buf *bp;
1674			bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1675			list_del_init(&bp->b_lru);
1676			if (bp->b_flags & XBF_WRITE_FAIL) {
1677				xfs_alert(btp->bt_mount,
1678"Corruption Alert: Buffer at daddr 0x%llx had permanent write failures!",
1679					(long long)bp->b_bn);
1680				xfs_alert(btp->bt_mount,
1681"Please run xfs_repair to determine the extent of the problem.");
1682			}
1683			xfs_buf_rele(bp);
1684		}
1685		if (loop++ != 0)
1686			delay(100);
1687	}
1688}
1689
1690static enum lru_status
1691xfs_buftarg_isolate(
1692	struct list_head	*item,
1693	struct list_lru_one	*lru,
1694	spinlock_t		*lru_lock,
1695	void			*arg)
1696{
1697	struct xfs_buf		*bp = container_of(item, struct xfs_buf, b_lru);
1698	struct list_head	*dispose = arg;
1699
1700	/*
1701	 * we are inverting the lru lock/bp->b_lock here, so use a trylock.
1702	 * If we fail to get the lock, just skip it.
1703	 */
1704	if (!spin_trylock(&bp->b_lock))
1705		return LRU_SKIP;
1706	/*
1707	 * Decrement the b_lru_ref count unless the value is already
1708	 * zero. If the value is already zero, we need to reclaim the
1709	 * buffer, otherwise it gets another trip through the LRU.
1710	 */
1711	if (atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
1712		spin_unlock(&bp->b_lock);
1713		return LRU_ROTATE;
1714	}
1715
1716	bp->b_state |= XFS_BSTATE_DISPOSE;
1717	list_lru_isolate_move(lru, item, dispose);
1718	spin_unlock(&bp->b_lock);
1719	return LRU_REMOVED;
1720}
1721
1722static unsigned long
1723xfs_buftarg_shrink_scan(
1724	struct shrinker		*shrink,
1725	struct shrink_control	*sc)
1726{
1727	struct xfs_buftarg	*btp = container_of(shrink,
1728					struct xfs_buftarg, bt_shrinker);
1729	LIST_HEAD(dispose);
1730	unsigned long		freed;
1731
1732	freed = list_lru_shrink_walk(&btp->bt_lru, sc,
1733				     xfs_buftarg_isolate, &dispose);
1734
1735	while (!list_empty(&dispose)) {
1736		struct xfs_buf *bp;
1737		bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1738		list_del_init(&bp->b_lru);
1739		xfs_buf_rele(bp);
1740	}
1741
1742	return freed;
1743}
1744
1745static unsigned long
1746xfs_buftarg_shrink_count(
1747	struct shrinker		*shrink,
1748	struct shrink_control	*sc)
1749{
1750	struct xfs_buftarg	*btp = container_of(shrink,
1751					struct xfs_buftarg, bt_shrinker);
1752	return list_lru_shrink_count(&btp->bt_lru, sc);
1753}
1754
1755void
1756xfs_free_buftarg(
 
1757	struct xfs_buftarg	*btp)
1758{
1759	unregister_shrinker(&btp->bt_shrinker);
1760	ASSERT(percpu_counter_sum(&btp->bt_io_count) == 0);
1761	percpu_counter_destroy(&btp->bt_io_count);
1762	list_lru_destroy(&btp->bt_lru);
1763
1764	xfs_blkdev_issue_flush(btp);
1765
1766	kmem_free(btp);
1767}
1768
1769int
1770xfs_setsize_buftarg(
1771	xfs_buftarg_t		*btp,
1772	unsigned int		sectorsize)
1773{
1774	/* Set up metadata sector size info */
1775	btp->bt_meta_sectorsize = sectorsize;
1776	btp->bt_meta_sectormask = sectorsize - 1;
1777
1778	if (set_blocksize(btp->bt_bdev, sectorsize)) {
1779		xfs_warn(btp->bt_mount,
1780			"Cannot set_blocksize to %u on device %pg",
1781			sectorsize, btp->bt_bdev);
1782		return -EINVAL;
1783	}
1784
1785	/* Set up device logical sector size mask */
1786	btp->bt_logical_sectorsize = bdev_logical_block_size(btp->bt_bdev);
1787	btp->bt_logical_sectormask = bdev_logical_block_size(btp->bt_bdev) - 1;
1788
1789	return 0;
1790}
1791
1792/*
1793 * When allocating the initial buffer target we have not yet
1794 * read in the superblock, so don't know what sized sectors
1795 * are being used at this early stage.  Play safe.
1796 */
1797STATIC int
1798xfs_setsize_buftarg_early(
1799	xfs_buftarg_t		*btp,
1800	struct block_device	*bdev)
1801{
1802	return xfs_setsize_buftarg(btp, bdev_logical_block_size(bdev));
1803}
1804
1805xfs_buftarg_t *
1806xfs_alloc_buftarg(
1807	struct xfs_mount	*mp,
1808	struct block_device	*bdev,
1809	struct dax_device	*dax_dev)
1810{
1811	xfs_buftarg_t		*btp;
1812
1813	btp = kmem_zalloc(sizeof(*btp), KM_SLEEP | KM_NOFS);
1814
1815	btp->bt_mount = mp;
1816	btp->bt_dev =  bdev->bd_dev;
1817	btp->bt_bdev = bdev;
1818	btp->bt_daxdev = dax_dev;
1819
1820	if (xfs_setsize_buftarg_early(btp, bdev))
1821		goto error_free;
1822
1823	if (list_lru_init(&btp->bt_lru))
1824		goto error_free;
1825
1826	if (percpu_counter_init(&btp->bt_io_count, 0, GFP_KERNEL))
1827		goto error_lru;
1828
1829	btp->bt_shrinker.count_objects = xfs_buftarg_shrink_count;
1830	btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
1831	btp->bt_shrinker.seeks = DEFAULT_SEEKS;
1832	btp->bt_shrinker.flags = SHRINKER_NUMA_AWARE;
1833	if (register_shrinker(&btp->bt_shrinker))
1834		goto error_pcpu;
1835	return btp;
1836
1837error_pcpu:
1838	percpu_counter_destroy(&btp->bt_io_count);
1839error_lru:
1840	list_lru_destroy(&btp->bt_lru);
1841error_free:
1842	kmem_free(btp);
1843	return NULL;
1844}
1845
1846/*
1847 * Cancel a delayed write list.
1848 *
1849 * Remove each buffer from the list, clear the delwri queue flag and drop the
1850 * associated buffer reference.
1851 */
1852void
1853xfs_buf_delwri_cancel(
1854	struct list_head	*list)
1855{
1856	struct xfs_buf		*bp;
1857
1858	while (!list_empty(list)) {
1859		bp = list_first_entry(list, struct xfs_buf, b_list);
1860
1861		xfs_buf_lock(bp);
1862		bp->b_flags &= ~_XBF_DELWRI_Q;
1863		list_del_init(&bp->b_list);
1864		xfs_buf_relse(bp);
1865	}
1866}
1867
1868/*
1869 * Add a buffer to the delayed write list.
1870 *
1871 * This queues a buffer for writeout if it hasn't already been.  Note that
1872 * neither this routine nor the buffer list submission functions perform
1873 * any internal synchronization.  It is expected that the lists are thread-local
1874 * to the callers.
1875 *
1876 * Returns true if we queued up the buffer, or false if it already had
1877 * been on the buffer list.
1878 */
1879bool
1880xfs_buf_delwri_queue(
1881	struct xfs_buf		*bp,
1882	struct list_head	*list)
1883{
1884	ASSERT(xfs_buf_islocked(bp));
1885	ASSERT(!(bp->b_flags & XBF_READ));
1886
1887	/*
1888	 * If the buffer is already marked delwri it already is queued up
1889	 * by someone else for imediate writeout.  Just ignore it in that
1890	 * case.
1891	 */
1892	if (bp->b_flags & _XBF_DELWRI_Q) {
1893		trace_xfs_buf_delwri_queued(bp, _RET_IP_);
1894		return false;
1895	}
1896
1897	trace_xfs_buf_delwri_queue(bp, _RET_IP_);
1898
1899	/*
1900	 * If a buffer gets written out synchronously or marked stale while it
1901	 * is on a delwri list we lazily remove it. To do this, the other party
1902	 * clears the  _XBF_DELWRI_Q flag but otherwise leaves the buffer alone.
1903	 * It remains referenced and on the list.  In a rare corner case it
1904	 * might get readded to a delwri list after the synchronous writeout, in
1905	 * which case we need just need to re-add the flag here.
1906	 */
1907	bp->b_flags |= _XBF_DELWRI_Q;
1908	if (list_empty(&bp->b_list)) {
1909		atomic_inc(&bp->b_hold);
1910		list_add_tail(&bp->b_list, list);
1911	}
1912
1913	return true;
1914}
1915
1916/*
1917 * Compare function is more complex than it needs to be because
1918 * the return value is only 32 bits and we are doing comparisons
1919 * on 64 bit values
1920 */
1921static int
1922xfs_buf_cmp(
1923	void		*priv,
1924	struct list_head *a,
1925	struct list_head *b)
1926{
1927	struct xfs_buf	*ap = container_of(a, struct xfs_buf, b_list);
1928	struct xfs_buf	*bp = container_of(b, struct xfs_buf, b_list);
1929	xfs_daddr_t		diff;
1930
1931	diff = ap->b_maps[0].bm_bn - bp->b_maps[0].bm_bn;
1932	if (diff < 0)
1933		return -1;
1934	if (diff > 0)
1935		return 1;
1936	return 0;
1937}
1938
1939/*
1940 * submit buffers for write.
1941 *
1942 * When we have a large buffer list, we do not want to hold all the buffers
1943 * locked while we block on the request queue waiting for IO dispatch. To avoid
1944 * this problem, we lock and submit buffers in groups of 50, thereby minimising
1945 * the lock hold times for lists which may contain thousands of objects.
1946 *
1947 * To do this, we sort the buffer list before we walk the list to lock and
1948 * submit buffers, and we plug and unplug around each group of buffers we
1949 * submit.
1950 */
1951static int
1952xfs_buf_delwri_submit_buffers(
1953	struct list_head	*buffer_list,
1954	struct list_head	*wait_list)
1955{
1956	struct xfs_buf		*bp, *n;
1957	LIST_HEAD		(submit_list);
1958	int			pinned = 0;
1959	struct blk_plug		plug;
1960
1961	list_sort(NULL, buffer_list, xfs_buf_cmp);
1962
1963	blk_start_plug(&plug);
1964	list_for_each_entry_safe(bp, n, buffer_list, b_list) {
1965		if (!wait_list) {
1966			if (xfs_buf_ispinned(bp)) {
1967				pinned++;
1968				continue;
1969			}
1970			if (!xfs_buf_trylock(bp))
1971				continue;
1972		} else {
1973			xfs_buf_lock(bp);
1974		}
1975
1976		/*
1977		 * Someone else might have written the buffer synchronously or
1978		 * marked it stale in the meantime.  In that case only the
1979		 * _XBF_DELWRI_Q flag got cleared, and we have to drop the
1980		 * reference and remove it from the list here.
1981		 */
1982		if (!(bp->b_flags & _XBF_DELWRI_Q)) {
1983			list_del_init(&bp->b_list);
1984			xfs_buf_relse(bp);
1985			continue;
1986		}
1987
1988		trace_xfs_buf_delwri_split(bp, _RET_IP_);
1989
1990		/*
1991		 * We do all IO submission async. This means if we need
1992		 * to wait for IO completion we need to take an extra
1993		 * reference so the buffer is still valid on the other
1994		 * side. We need to move the buffer onto the io_list
1995		 * at this point so the caller can still access it.
1996		 */
1997		bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_WRITE_FAIL);
1998		bp->b_flags |= XBF_WRITE | XBF_ASYNC;
1999		if (wait_list) {
2000			xfs_buf_hold(bp);
2001			list_move_tail(&bp->b_list, wait_list);
2002		} else
2003			list_del_init(&bp->b_list);
2004
2005		xfs_buf_submit(bp);
2006	}
2007	blk_finish_plug(&plug);
2008
2009	return pinned;
2010}
2011
2012/*
2013 * Write out a buffer list asynchronously.
2014 *
2015 * This will take the @buffer_list, write all non-locked and non-pinned buffers
2016 * out and not wait for I/O completion on any of the buffers.  This interface
2017 * is only safely useable for callers that can track I/O completion by higher
2018 * level means, e.g. AIL pushing as the @buffer_list is consumed in this
2019 * function.
2020 */
2021int
2022xfs_buf_delwri_submit_nowait(
2023	struct list_head	*buffer_list)
2024{
2025	return xfs_buf_delwri_submit_buffers(buffer_list, NULL);
2026}
2027
2028/*
2029 * Write out a buffer list synchronously.
2030 *
2031 * This will take the @buffer_list, write all buffers out and wait for I/O
2032 * completion on all of the buffers. @buffer_list is consumed by the function,
2033 * so callers must have some other way of tracking buffers if they require such
2034 * functionality.
2035 */
2036int
2037xfs_buf_delwri_submit(
2038	struct list_head	*buffer_list)
2039{
2040	LIST_HEAD		(wait_list);
2041	int			error = 0, error2;
2042	struct xfs_buf		*bp;
2043
2044	xfs_buf_delwri_submit_buffers(buffer_list, &wait_list);
2045
2046	/* Wait for IO to complete. */
2047	while (!list_empty(&wait_list)) {
2048		bp = list_first_entry(&wait_list, struct xfs_buf, b_list);
2049
2050		list_del_init(&bp->b_list);
2051
2052		/* locking the buffer will wait for async IO completion. */
2053		xfs_buf_lock(bp);
2054		error2 = bp->b_error;
2055		xfs_buf_relse(bp);
2056		if (!error)
2057			error = error2;
2058	}
2059
2060	return error;
2061}
2062
2063/*
2064 * Push a single buffer on a delwri queue.
2065 *
2066 * The purpose of this function is to submit a single buffer of a delwri queue
2067 * and return with the buffer still on the original queue. The waiting delwri
2068 * buffer submission infrastructure guarantees transfer of the delwri queue
2069 * buffer reference to a temporary wait list. We reuse this infrastructure to
2070 * transfer the buffer back to the original queue.
2071 *
2072 * Note the buffer transitions from the queued state, to the submitted and wait
2073 * listed state and back to the queued state during this call. The buffer
2074 * locking and queue management logic between _delwri_pushbuf() and
2075 * _delwri_queue() guarantee that the buffer cannot be queued to another list
2076 * before returning.
2077 */
2078int
2079xfs_buf_delwri_pushbuf(
2080	struct xfs_buf		*bp,
2081	struct list_head	*buffer_list)
2082{
2083	LIST_HEAD		(submit_list);
2084	int			error;
2085
2086	ASSERT(bp->b_flags & _XBF_DELWRI_Q);
2087
2088	trace_xfs_buf_delwri_pushbuf(bp, _RET_IP_);
2089
2090	/*
2091	 * Isolate the buffer to a new local list so we can submit it for I/O
2092	 * independently from the rest of the original list.
2093	 */
2094	xfs_buf_lock(bp);
2095	list_move(&bp->b_list, &submit_list);
2096	xfs_buf_unlock(bp);
2097
2098	/*
2099	 * Delwri submission clears the DELWRI_Q buffer flag and returns with
2100	 * the buffer on the wait list with an associated reference. Rather than
2101	 * bounce the buffer from a local wait list back to the original list
2102	 * after I/O completion, reuse the original list as the wait list.
2103	 */
2104	xfs_buf_delwri_submit_buffers(&submit_list, buffer_list);
2105
2106	/*
2107	 * The buffer is now under I/O and wait listed as during typical delwri
2108	 * submission. Lock the buffer to wait for I/O completion. Rather than
2109	 * remove the buffer from the wait list and release the reference, we
2110	 * want to return with the buffer queued to the original list. The
2111	 * buffer already sits on the original list with a wait list reference,
2112	 * however. If we let the queue inherit that wait list reference, all we
2113	 * need to do is reset the DELWRI_Q flag.
2114	 */
2115	xfs_buf_lock(bp);
2116	error = bp->b_error;
2117	bp->b_flags |= _XBF_DELWRI_Q;
2118	xfs_buf_unlock(bp);
2119
2120	return error;
2121}
2122
2123int __init
2124xfs_buf_init(void)
2125{
2126	xfs_buf_zone = kmem_zone_init_flags(sizeof(xfs_buf_t), "xfs_buf",
2127						KM_ZONE_HWALIGN, NULL);
2128	if (!xfs_buf_zone)
2129		goto out;
2130
2131	return 0;
2132
2133 out:
2134	return -ENOMEM;
2135}
2136
2137void
2138xfs_buf_terminate(void)
2139{
2140	kmem_zone_destroy(xfs_buf_zone);
2141}
2142
2143void xfs_buf_set_ref(struct xfs_buf *bp, int lru_ref)
2144{
2145	/*
2146	 * Set the lru reference count to 0 based on the error injection tag.
2147	 * This allows userspace to disrupt buffer caching for debug/testing
2148	 * purposes.
2149	 */
2150	if (XFS_TEST_ERROR(false, bp->b_target->bt_mount,
2151			   XFS_ERRTAG_BUF_LRU_REF))
2152		lru_ref = 0;
2153
2154	atomic_set(&bp->b_lru_ref, lru_ref);
2155}