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Linux/fs/xfs/xfs_buf.c

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  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 
 46 static kmem_zone_t *xfs_buf_zone;
 47 
 48 #ifdef XFS_BUF_LOCK_TRACKING
 49 # define XB_SET_OWNER(bp)       ((bp)->b_last_holder = current->pid)
 50 # define XB_CLEAR_OWNER(bp)     ((bp)->b_last_holder = -1)
 51 # define XB_GET_OWNER(bp)       ((bp)->b_last_holder)
 52 #else
 53 # define XB_SET_OWNER(bp)       do { } while (0)
 54 # define XB_CLEAR_OWNER(bp)     do { } while (0)
 55 # define XB_GET_OWNER(bp)       do { } while (0)
 56 #endif
 57 
 58 #define xb_to_gfp(flags) \
 59         ((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : GFP_NOFS) | __GFP_NOWARN)
 60 
 61 
 62 static inline int
 63 xfs_buf_is_vmapped(
 64         struct xfs_buf  *bp)
 65 {
 66         /*
 67          * Return true if the buffer is vmapped.
 68          *
 69          * b_addr is null if the buffer is not mapped, but the code is clever
 70          * enough to know it doesn't have to map a single page, so the check has
 71          * to be both for b_addr and bp->b_page_count > 1.
 72          */
 73         return bp->b_addr && bp->b_page_count > 1;
 74 }
 75 
 76 static inline int
 77 xfs_buf_vmap_len(
 78         struct xfs_buf  *bp)
 79 {
 80         return (bp->b_page_count * PAGE_SIZE) - bp->b_offset;
 81 }
 82 
 83 /*
 84  * Bump the I/O in flight count on the buftarg if we haven't yet done so for
 85  * this buffer. The count is incremented once per buffer (per hold cycle)
 86  * because the corresponding decrement is deferred to buffer release. Buffers
 87  * can undergo I/O multiple times in a hold-release cycle and per buffer I/O
 88  * tracking adds unnecessary overhead. This is used for sychronization purposes
 89  * with unmount (see xfs_wait_buftarg()), so all we really need is a count of
 90  * in-flight buffers.
 91  *
 92  * Buffers that are never released (e.g., superblock, iclog buffers) must set
 93  * the XBF_NO_IOACCT flag before I/O submission. Otherwise, the buftarg count
 94  * never reaches zero and unmount hangs indefinitely.
 95  */
 96 static inline void
 97 xfs_buf_ioacct_inc(
 98         struct xfs_buf  *bp)
 99 {
100         if (bp->b_flags & XBF_NO_IOACCT)
101                 return;
102 
103         ASSERT(bp->b_flags & XBF_ASYNC);
104         spin_lock(&bp->b_lock);
105         if (!(bp->b_state & XFS_BSTATE_IN_FLIGHT)) {
106                 bp->b_state |= XFS_BSTATE_IN_FLIGHT;
107                 percpu_counter_inc(&bp->b_target->bt_io_count);
108         }
109         spin_unlock(&bp->b_lock);
110 }
111 
112 /*
113  * Clear the in-flight state on a buffer about to be released to the LRU or
114  * freed and unaccount from the buftarg.
115  */
116 static inline void
117 __xfs_buf_ioacct_dec(
118         struct xfs_buf  *bp)
119 {
120         ASSERT(spin_is_locked(&bp->b_lock));
121 
122         if (bp->b_state & XFS_BSTATE_IN_FLIGHT) {
123                 bp->b_state &= ~XFS_BSTATE_IN_FLIGHT;
124                 percpu_counter_dec(&bp->b_target->bt_io_count);
125         }
126 }
127 
128 static inline void
129 xfs_buf_ioacct_dec(
130         struct xfs_buf  *bp)
131 {
132         spin_lock(&bp->b_lock);
133         __xfs_buf_ioacct_dec(bp);
134         spin_unlock(&bp->b_lock);
135 }
136 
137 /*
138  * When we mark a buffer stale, we remove the buffer from the LRU and clear the
139  * b_lru_ref count so that the buffer is freed immediately when the buffer
140  * reference count falls to zero. If the buffer is already on the LRU, we need
141  * to remove the reference that LRU holds on the buffer.
142  *
143  * This prevents build-up of stale buffers on the LRU.
144  */
145 void
146 xfs_buf_stale(
147         struct xfs_buf  *bp)
148 {
149         ASSERT(xfs_buf_islocked(bp));
150 
151         bp->b_flags |= XBF_STALE;
152 
153         /*
154          * Clear the delwri status so that a delwri queue walker will not
155          * flush this buffer to disk now that it is stale. The delwri queue has
156          * a reference to the buffer, so this is safe to do.
157          */
158         bp->b_flags &= ~_XBF_DELWRI_Q;
159 
160         /*
161          * Once the buffer is marked stale and unlocked, a subsequent lookup
162          * could reset b_flags. There is no guarantee that the buffer is
163          * unaccounted (released to LRU) before that occurs. Drop in-flight
164          * status now to preserve accounting consistency.
165          */
166         spin_lock(&bp->b_lock);
167         __xfs_buf_ioacct_dec(bp);
168 
169         atomic_set(&bp->b_lru_ref, 0);
170         if (!(bp->b_state & XFS_BSTATE_DISPOSE) &&
171             (list_lru_del(&bp->b_target->bt_lru, &bp->b_lru)))
172                 atomic_dec(&bp->b_hold);
173 
174         ASSERT(atomic_read(&bp->b_hold) >= 1);
175         spin_unlock(&bp->b_lock);
176 }
177 
178 static int
179 xfs_buf_get_maps(
180         struct xfs_buf          *bp,
181         int                     map_count)
182 {
183         ASSERT(bp->b_maps == NULL);
184         bp->b_map_count = map_count;
185 
186         if (map_count == 1) {
187                 bp->b_maps = &bp->__b_map;
188                 return 0;
189         }
190 
191         bp->b_maps = kmem_zalloc(map_count * sizeof(struct xfs_buf_map),
192                                 KM_NOFS);
193         if (!bp->b_maps)
194                 return -ENOMEM;
195         return 0;
196 }
197 
198 /*
199  *      Frees b_pages if it was allocated.
200  */
201 static void
202 xfs_buf_free_maps(
203         struct xfs_buf  *bp)
204 {
205         if (bp->b_maps != &bp->__b_map) {
206                 kmem_free(bp->b_maps);
207                 bp->b_maps = NULL;
208         }
209 }
210 
211 struct xfs_buf *
212 _xfs_buf_alloc(
213         struct xfs_buftarg      *target,
214         struct xfs_buf_map      *map,
215         int                     nmaps,
216         xfs_buf_flags_t         flags)
217 {
218         struct xfs_buf          *bp;
219         int                     error;
220         int                     i;
221 
222         bp = kmem_zone_zalloc(xfs_buf_zone, KM_NOFS);
223         if (unlikely(!bp))
224                 return NULL;
225 
226         /*
227          * We don't want certain flags to appear in b_flags unless they are
228          * specifically set by later operations on the buffer.
229          */
230         flags &= ~(XBF_UNMAPPED | XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD);
231 
232         atomic_set(&bp->b_hold, 1);
233         atomic_set(&bp->b_lru_ref, 1);
234         init_completion(&bp->b_iowait);
235         INIT_LIST_HEAD(&bp->b_lru);
236         INIT_LIST_HEAD(&bp->b_list);
237         sema_init(&bp->b_sema, 0); /* held, no waiters */
238         spin_lock_init(&bp->b_lock);
239         XB_SET_OWNER(bp);
240         bp->b_target = target;
241         bp->b_flags = flags;
242 
243         /*
244          * Set length and io_length to the same value initially.
245          * I/O routines should use io_length, which will be the same in
246          * most cases but may be reset (e.g. XFS recovery).
247          */
248         error = xfs_buf_get_maps(bp, nmaps);
249         if (error)  {
250                 kmem_zone_free(xfs_buf_zone, bp);
251                 return NULL;
252         }
253 
254         bp->b_bn = map[0].bm_bn;
255         bp->b_length = 0;
256         for (i = 0; i < nmaps; i++) {
257                 bp->b_maps[i].bm_bn = map[i].bm_bn;
258                 bp->b_maps[i].bm_len = map[i].bm_len;
259                 bp->b_length += map[i].bm_len;
260         }
261         bp->b_io_length = bp->b_length;
262 
263         atomic_set(&bp->b_pin_count, 0);
264         init_waitqueue_head(&bp->b_waiters);
265 
266         XFS_STATS_INC(target->bt_mount, xb_create);
267         trace_xfs_buf_init(bp, _RET_IP_);
268 
269         return bp;
270 }
271 
272 /*
273  *      Allocate a page array capable of holding a specified number
274  *      of pages, and point the page buf at it.
275  */
276 STATIC int
277 _xfs_buf_get_pages(
278         xfs_buf_t               *bp,
279         int                     page_count)
280 {
281         /* Make sure that we have a page list */
282         if (bp->b_pages == NULL) {
283                 bp->b_page_count = page_count;
284                 if (page_count <= XB_PAGES) {
285                         bp->b_pages = bp->b_page_array;
286                 } else {
287                         bp->b_pages = kmem_alloc(sizeof(struct page *) *
288                                                  page_count, KM_NOFS);
289                         if (bp->b_pages == NULL)
290                                 return -ENOMEM;
291                 }
292                 memset(bp->b_pages, 0, sizeof(struct page *) * page_count);
293         }
294         return 0;
295 }
296 
297 /*
298  *      Frees b_pages if it was allocated.
299  */
300 STATIC void
301 _xfs_buf_free_pages(
302         xfs_buf_t       *bp)
303 {
304         if (bp->b_pages != bp->b_page_array) {
305                 kmem_free(bp->b_pages);
306                 bp->b_pages = NULL;
307         }
308 }
309 
310 /*
311  *      Releases the specified buffer.
312  *
313  *      The modification state of any associated pages is left unchanged.
314  *      The buffer must not be on any hash - use xfs_buf_rele instead for
315  *      hashed and refcounted buffers
316  */
317 void
318 xfs_buf_free(
319         xfs_buf_t               *bp)
320 {
321         trace_xfs_buf_free(bp, _RET_IP_);
322 
323         ASSERT(list_empty(&bp->b_lru));
324 
325         if (bp->b_flags & _XBF_PAGES) {
326                 uint            i;
327 
328                 if (xfs_buf_is_vmapped(bp))
329                         vm_unmap_ram(bp->b_addr - bp->b_offset,
330                                         bp->b_page_count);
331 
332                 for (i = 0; i < bp->b_page_count; i++) {
333                         struct page     *page = bp->b_pages[i];
334 
335                         __free_page(page);
336                 }
337         } else if (bp->b_flags & _XBF_KMEM)
338                 kmem_free(bp->b_addr);
339         _xfs_buf_free_pages(bp);
340         xfs_buf_free_maps(bp);
341         kmem_zone_free(xfs_buf_zone, bp);
342 }
343 
344 /*
345  * Allocates all the pages for buffer in question and builds it's page list.
346  */
347 STATIC int
348 xfs_buf_allocate_memory(
349         xfs_buf_t               *bp,
350         uint                    flags)
351 {
352         size_t                  size;
353         size_t                  nbytes, offset;
354         gfp_t                   gfp_mask = xb_to_gfp(flags);
355         unsigned short          page_count, i;
356         xfs_off_t               start, end;
357         int                     error;
358 
359         /*
360          * for buffers that are contained within a single page, just allocate
361          * the memory from the heap - there's no need for the complexity of
362          * page arrays to keep allocation down to order 0.
363          */
364         size = BBTOB(bp->b_length);
365         if (size < PAGE_SIZE) {
366                 bp->b_addr = kmem_alloc(size, KM_NOFS);
367                 if (!bp->b_addr) {
368                         /* low memory - use alloc_page loop instead */
369                         goto use_alloc_page;
370                 }
371 
372                 if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
373                     ((unsigned long)bp->b_addr & PAGE_MASK)) {
374                         /* b_addr spans two pages - use alloc_page instead */
375                         kmem_free(bp->b_addr);
376                         bp->b_addr = NULL;
377                         goto use_alloc_page;
378                 }
379                 bp->b_offset = offset_in_page(bp->b_addr);
380                 bp->b_pages = bp->b_page_array;
381                 bp->b_pages[0] = virt_to_page(bp->b_addr);
382                 bp->b_page_count = 1;
383                 bp->b_flags |= _XBF_KMEM;
384                 return 0;
385         }
386 
387 use_alloc_page:
388         start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
389         end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
390                                                                 >> PAGE_SHIFT;
391         page_count = end - start;
392         error = _xfs_buf_get_pages(bp, page_count);
393         if (unlikely(error))
394                 return error;
395 
396         offset = bp->b_offset;
397         bp->b_flags |= _XBF_PAGES;
398 
399         for (i = 0; i < bp->b_page_count; i++) {
400                 struct page     *page;
401                 uint            retries = 0;
402 retry:
403                 page = alloc_page(gfp_mask);
404                 if (unlikely(page == NULL)) {
405                         if (flags & XBF_READ_AHEAD) {
406                                 bp->b_page_count = i;
407                                 error = -ENOMEM;
408                                 goto out_free_pages;
409                         }
410 
411                         /*
412                          * This could deadlock.
413                          *
414                          * But until all the XFS lowlevel code is revamped to
415                          * handle buffer allocation failures we can't do much.
416                          */
417                         if (!(++retries % 100))
418                                 xfs_err(NULL,
419                 "%s(%u) possible memory allocation deadlock in %s (mode:0x%x)",
420                                         current->comm, current->pid,
421                                         __func__, gfp_mask);
422 
423                         XFS_STATS_INC(bp->b_target->bt_mount, xb_page_retries);
424                         congestion_wait(BLK_RW_ASYNC, HZ/50);
425                         goto retry;
426                 }
427 
428                 XFS_STATS_INC(bp->b_target->bt_mount, xb_page_found);
429 
430                 nbytes = min_t(size_t, size, PAGE_SIZE - offset);
431                 size -= nbytes;
432                 bp->b_pages[i] = page;
433                 offset = 0;
434         }
435         return 0;
436 
437 out_free_pages:
438         for (i = 0; i < bp->b_page_count; i++)
439                 __free_page(bp->b_pages[i]);
440         bp->b_flags &= ~_XBF_PAGES;
441         return error;
442 }
443 
444 /*
445  *      Map buffer into kernel address-space if necessary.
446  */
447 STATIC int
448 _xfs_buf_map_pages(
449         xfs_buf_t               *bp,
450         uint                    flags)
451 {
452         ASSERT(bp->b_flags & _XBF_PAGES);
453         if (bp->b_page_count == 1) {
454                 /* A single page buffer is always mappable */
455                 bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
456         } else if (flags & XBF_UNMAPPED) {
457                 bp->b_addr = NULL;
458         } else {
459                 int retried = 0;
460                 unsigned noio_flag;
461 
462                 /*
463                  * vm_map_ram() will allocate auxillary structures (e.g.
464                  * pagetables) with GFP_KERNEL, yet we are likely to be under
465                  * GFP_NOFS context here. Hence we need to tell memory reclaim
466                  * that we are in such a context via PF_MEMALLOC_NOIO to prevent
467                  * memory reclaim re-entering the filesystem here and
468                  * potentially deadlocking.
469                  */
470                 noio_flag = memalloc_noio_save();
471                 do {
472                         bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
473                                                 -1, PAGE_KERNEL);
474                         if (bp->b_addr)
475                                 break;
476                         vm_unmap_aliases();
477                 } while (retried++ <= 1);
478                 memalloc_noio_restore(noio_flag);
479 
480                 if (!bp->b_addr)
481                         return -ENOMEM;
482                 bp->b_addr += bp->b_offset;
483         }
484 
485         return 0;
486 }
487 
488 /*
489  *      Finding and Reading Buffers
490  */
491 static int
492 _xfs_buf_obj_cmp(
493         struct rhashtable_compare_arg   *arg,
494         const void                      *obj)
495 {
496         const struct xfs_buf_map        *map = arg->key;
497         const struct xfs_buf            *bp = obj;
498 
499         /*
500          * The key hashing in the lookup path depends on the key being the
501          * first element of the compare_arg, make sure to assert this.
502          */
503         BUILD_BUG_ON(offsetof(struct xfs_buf_map, bm_bn) != 0);
504 
505         if (bp->b_bn != map->bm_bn)
506                 return 1;
507 
508         if (unlikely(bp->b_length != map->bm_len)) {
509                 /*
510                  * found a block number match. If the range doesn't
511                  * match, the only way this is allowed is if the buffer
512                  * in the cache is stale and the transaction that made
513                  * it stale has not yet committed. i.e. we are
514                  * reallocating a busy extent. Skip this buffer and
515                  * continue searching for an exact match.
516                  */
517                 ASSERT(bp->b_flags & XBF_STALE);
518                 return 1;
519         }
520         return 0;
521 }
522 
523 static const struct rhashtable_params xfs_buf_hash_params = {
524         .min_size               = 32,   /* empty AGs have minimal footprint */
525         .nelem_hint             = 16,
526         .key_len                = sizeof(xfs_daddr_t),
527         .key_offset             = offsetof(struct xfs_buf, b_bn),
528         .head_offset            = offsetof(struct xfs_buf, b_rhash_head),
529         .automatic_shrinking    = true,
530         .obj_cmpfn              = _xfs_buf_obj_cmp,
531 };
532 
533 int
534 xfs_buf_hash_init(
535         struct xfs_perag        *pag)
536 {
537         spin_lock_init(&pag->pag_buf_lock);
538         return rhashtable_init(&pag->pag_buf_hash, &xfs_buf_hash_params);
539 }
540 
541 void
542 xfs_buf_hash_destroy(
543         struct xfs_perag        *pag)
544 {
545         rhashtable_destroy(&pag->pag_buf_hash);
546 }
547 
548 /*
549  *      Look up, and creates if absent, a lockable buffer for
550  *      a given range of an inode.  The buffer is returned
551  *      locked. No I/O is implied by this call.
552  */
553 xfs_buf_t *
554 _xfs_buf_find(
555         struct xfs_buftarg      *btp,
556         struct xfs_buf_map      *map,
557         int                     nmaps,
558         xfs_buf_flags_t         flags,
559         xfs_buf_t               *new_bp)
560 {
561         struct xfs_perag        *pag;
562         xfs_buf_t               *bp;
563         struct xfs_buf_map      cmap = { .bm_bn = map[0].bm_bn };
564         xfs_daddr_t             eofs;
565         int                     i;
566 
567         for (i = 0; i < nmaps; i++)
568                 cmap.bm_len += map[i].bm_len;
569 
570         /* Check for IOs smaller than the sector size / not sector aligned */
571         ASSERT(!(BBTOB(cmap.bm_len) < btp->bt_meta_sectorsize));
572         ASSERT(!(BBTOB(cmap.bm_bn) & (xfs_off_t)btp->bt_meta_sectormask));
573 
574         /*
575          * Corrupted block numbers can get through to here, unfortunately, so we
576          * have to check that the buffer falls within the filesystem bounds.
577          */
578         eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
579         if (cmap.bm_bn < 0 || cmap.bm_bn >= eofs) {
580                 /*
581                  * XXX (dgc): we should really be returning -EFSCORRUPTED here,
582                  * but none of the higher level infrastructure supports
583                  * returning a specific error on buffer lookup failures.
584                  */
585                 xfs_alert(btp->bt_mount,
586                           "%s: Block out of range: block 0x%llx, EOFS 0x%llx ",
587                           __func__, cmap.bm_bn, eofs);
588                 WARN_ON(1);
589                 return NULL;
590         }
591 
592         pag = xfs_perag_get(btp->bt_mount,
593                             xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
594 
595         spin_lock(&pag->pag_buf_lock);
596         bp = rhashtable_lookup_fast(&pag->pag_buf_hash, &cmap,
597                                     xfs_buf_hash_params);
598         if (bp) {
599                 atomic_inc(&bp->b_hold);
600                 goto found;
601         }
602 
603         /* No match found */
604         if (new_bp) {
605                 /* the buffer keeps the perag reference until it is freed */
606                 new_bp->b_pag = pag;
607                 rhashtable_insert_fast(&pag->pag_buf_hash,
608                                        &new_bp->b_rhash_head,
609                                        xfs_buf_hash_params);
610                 spin_unlock(&pag->pag_buf_lock);
611         } else {
612                 XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
613                 spin_unlock(&pag->pag_buf_lock);
614                 xfs_perag_put(pag);
615         }
616         return new_bp;
617 
618 found:
619         spin_unlock(&pag->pag_buf_lock);
620         xfs_perag_put(pag);
621 
622         if (!xfs_buf_trylock(bp)) {
623                 if (flags & XBF_TRYLOCK) {
624                         xfs_buf_rele(bp);
625                         XFS_STATS_INC(btp->bt_mount, xb_busy_locked);
626                         return NULL;
627                 }
628                 xfs_buf_lock(bp);
629                 XFS_STATS_INC(btp->bt_mount, xb_get_locked_waited);
630         }
631 
632         /*
633          * if the buffer is stale, clear all the external state associated with
634          * it. We need to keep flags such as how we allocated the buffer memory
635          * intact here.
636          */
637         if (bp->b_flags & XBF_STALE) {
638                 ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
639                 ASSERT(bp->b_iodone == NULL);
640                 bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
641                 bp->b_ops = NULL;
642         }
643 
644         trace_xfs_buf_find(bp, flags, _RET_IP_);
645         XFS_STATS_INC(btp->bt_mount, xb_get_locked);
646         return bp;
647 }
648 
649 /*
650  * Assembles a buffer covering the specified range. The code is optimised for
651  * cache hits, as metadata intensive workloads will see 3 orders of magnitude
652  * more hits than misses.
653  */
654 struct xfs_buf *
655 xfs_buf_get_map(
656         struct xfs_buftarg      *target,
657         struct xfs_buf_map      *map,
658         int                     nmaps,
659         xfs_buf_flags_t         flags)
660 {
661         struct xfs_buf          *bp;
662         struct xfs_buf          *new_bp;
663         int                     error = 0;
664 
665         bp = _xfs_buf_find(target, map, nmaps, flags, NULL);
666         if (likely(bp))
667                 goto found;
668 
669         new_bp = _xfs_buf_alloc(target, map, nmaps, flags);
670         if (unlikely(!new_bp))
671                 return NULL;
672 
673         error = xfs_buf_allocate_memory(new_bp, flags);
674         if (error) {
675                 xfs_buf_free(new_bp);
676                 return NULL;
677         }
678 
679         bp = _xfs_buf_find(target, map, nmaps, flags, new_bp);
680         if (!bp) {
681                 xfs_buf_free(new_bp);
682                 return NULL;
683         }
684 
685         if (bp != new_bp)
686                 xfs_buf_free(new_bp);
687 
688 found:
689         if (!bp->b_addr) {
690                 error = _xfs_buf_map_pages(bp, flags);
691                 if (unlikely(error)) {
692                         xfs_warn(target->bt_mount,
693                                 "%s: failed to map pagesn", __func__);
694                         xfs_buf_relse(bp);
695                         return NULL;
696                 }
697         }
698 
699         /*
700          * Clear b_error if this is a lookup from a caller that doesn't expect
701          * valid data to be found in the buffer.
702          */
703         if (!(flags & XBF_READ))
704                 xfs_buf_ioerror(bp, 0);
705 
706         XFS_STATS_INC(target->bt_mount, xb_get);
707         trace_xfs_buf_get(bp, flags, _RET_IP_);
708         return bp;
709 }
710 
711 STATIC int
712 _xfs_buf_read(
713         xfs_buf_t               *bp,
714         xfs_buf_flags_t         flags)
715 {
716         ASSERT(!(flags & XBF_WRITE));
717         ASSERT(bp->b_maps[0].bm_bn != XFS_BUF_DADDR_NULL);
718 
719         bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
720         bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
721 
722         if (flags & XBF_ASYNC) {
723                 xfs_buf_submit(bp);
724                 return 0;
725         }
726         return xfs_buf_submit_wait(bp);
727 }
728 
729 xfs_buf_t *
730 xfs_buf_read_map(
731         struct xfs_buftarg      *target,
732         struct xfs_buf_map      *map,
733         int                     nmaps,
734         xfs_buf_flags_t         flags,
735         const struct xfs_buf_ops *ops)
736 {
737         struct xfs_buf          *bp;
738 
739         flags |= XBF_READ;
740 
741         bp = xfs_buf_get_map(target, map, nmaps, flags);
742         if (bp) {
743                 trace_xfs_buf_read(bp, flags, _RET_IP_);
744 
745                 if (!(bp->b_flags & XBF_DONE)) {
746                         XFS_STATS_INC(target->bt_mount, xb_get_read);
747                         bp->b_ops = ops;
748                         _xfs_buf_read(bp, flags);
749                 } else if (flags & XBF_ASYNC) {
750                         /*
751                          * Read ahead call which is already satisfied,
752                          * drop the buffer
753                          */
754                         xfs_buf_relse(bp);
755                         return NULL;
756                 } else {
757                         /* We do not want read in the flags */
758                         bp->b_flags &= ~XBF_READ;
759                 }
760         }
761 
762         return bp;
763 }
764 
765 /*
766  *      If we are not low on memory then do the readahead in a deadlock
767  *      safe manner.
768  */
769 void
770 xfs_buf_readahead_map(
771         struct xfs_buftarg      *target,
772         struct xfs_buf_map      *map,
773         int                     nmaps,
774         const struct xfs_buf_ops *ops)
775 {
776         if (bdi_read_congested(target->bt_bdev->bd_bdi))
777                 return;
778 
779         xfs_buf_read_map(target, map, nmaps,
780                      XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD, ops);
781 }
782 
783 /*
784  * Read an uncached buffer from disk. Allocates and returns a locked
785  * buffer containing the disk contents or nothing.
786  */
787 int
788 xfs_buf_read_uncached(
789         struct xfs_buftarg      *target,
790         xfs_daddr_t             daddr,
791         size_t                  numblks,
792         int                     flags,
793         struct xfs_buf          **bpp,
794         const struct xfs_buf_ops *ops)
795 {
796         struct xfs_buf          *bp;
797 
798         *bpp = NULL;
799 
800         bp = xfs_buf_get_uncached(target, numblks, flags);
801         if (!bp)
802                 return -ENOMEM;
803 
804         /* set up the buffer for a read IO */
805         ASSERT(bp->b_map_count == 1);
806         bp->b_bn = XFS_BUF_DADDR_NULL;  /* always null for uncached buffers */
807         bp->b_maps[0].bm_bn = daddr;
808         bp->b_flags |= XBF_READ;
809         bp->b_ops = ops;
810 
811         xfs_buf_submit_wait(bp);
812         if (bp->b_error) {
813                 int     error = bp->b_error;
814                 xfs_buf_relse(bp);
815                 return error;
816         }
817 
818         *bpp = bp;
819         return 0;
820 }
821 
822 /*
823  * Return a buffer allocated as an empty buffer and associated to external
824  * memory via xfs_buf_associate_memory() back to it's empty state.
825  */
826 void
827 xfs_buf_set_empty(
828         struct xfs_buf          *bp,
829         size_t                  numblks)
830 {
831         if (bp->b_pages)
832                 _xfs_buf_free_pages(bp);
833 
834         bp->b_pages = NULL;
835         bp->b_page_count = 0;
836         bp->b_addr = NULL;
837         bp->b_length = numblks;
838         bp->b_io_length = numblks;
839 
840         ASSERT(bp->b_map_count == 1);
841         bp->b_bn = XFS_BUF_DADDR_NULL;
842         bp->b_maps[0].bm_bn = XFS_BUF_DADDR_NULL;
843         bp->b_maps[0].bm_len = bp->b_length;
844 }
845 
846 static inline struct page *
847 mem_to_page(
848         void                    *addr)
849 {
850         if ((!is_vmalloc_addr(addr))) {
851                 return virt_to_page(addr);
852         } else {
853                 return vmalloc_to_page(addr);
854         }
855 }
856 
857 int
858 xfs_buf_associate_memory(
859         xfs_buf_t               *bp,
860         void                    *mem,
861         size_t                  len)
862 {
863         int                     rval;
864         int                     i = 0;
865         unsigned long           pageaddr;
866         unsigned long           offset;
867         size_t                  buflen;
868         int                     page_count;
869 
870         pageaddr = (unsigned long)mem & PAGE_MASK;
871         offset = (unsigned long)mem - pageaddr;
872         buflen = PAGE_ALIGN(len + offset);
873         page_count = buflen >> PAGE_SHIFT;
874 
875         /* Free any previous set of page pointers */
876         if (bp->b_pages)
877                 _xfs_buf_free_pages(bp);
878 
879         bp->b_pages = NULL;
880         bp->b_addr = mem;
881 
882         rval = _xfs_buf_get_pages(bp, page_count);
883         if (rval)
884                 return rval;
885 
886         bp->b_offset = offset;
887 
888         for (i = 0; i < bp->b_page_count; i++) {
889                 bp->b_pages[i] = mem_to_page((void *)pageaddr);
890                 pageaddr += PAGE_SIZE;
891         }
892 
893         bp->b_io_length = BTOBB(len);
894         bp->b_length = BTOBB(buflen);
895 
896         return 0;
897 }
898 
899 xfs_buf_t *
900 xfs_buf_get_uncached(
901         struct xfs_buftarg      *target,
902         size_t                  numblks,
903         int                     flags)
904 {
905         unsigned long           page_count;
906         int                     error, i;
907         struct xfs_buf          *bp;
908         DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
909 
910         /* flags might contain irrelevant bits, pass only what we care about */
911         bp = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT);
912         if (unlikely(bp == NULL))
913                 goto fail;
914 
915         page_count = PAGE_ALIGN(numblks << BBSHIFT) >> PAGE_SHIFT;
916         error = _xfs_buf_get_pages(bp, page_count);
917         if (error)
918                 goto fail_free_buf;
919 
920         for (i = 0; i < page_count; i++) {
921                 bp->b_pages[i] = alloc_page(xb_to_gfp(flags));
922                 if (!bp->b_pages[i])
923                         goto fail_free_mem;
924         }
925         bp->b_flags |= _XBF_PAGES;
926 
927         error = _xfs_buf_map_pages(bp, 0);
928         if (unlikely(error)) {
929                 xfs_warn(target->bt_mount,
930                         "%s: failed to map pages", __func__);
931                 goto fail_free_mem;
932         }
933 
934         trace_xfs_buf_get_uncached(bp, _RET_IP_);
935         return bp;
936 
937  fail_free_mem:
938         while (--i >= 0)
939                 __free_page(bp->b_pages[i]);
940         _xfs_buf_free_pages(bp);
941  fail_free_buf:
942         xfs_buf_free_maps(bp);
943         kmem_zone_free(xfs_buf_zone, bp);
944  fail:
945         return NULL;
946 }
947 
948 /*
949  *      Increment reference count on buffer, to hold the buffer concurrently
950  *      with another thread which may release (free) the buffer asynchronously.
951  *      Must hold the buffer already to call this function.
952  */
953 void
954 xfs_buf_hold(
955         xfs_buf_t               *bp)
956 {
957         trace_xfs_buf_hold(bp, _RET_IP_);
958         atomic_inc(&bp->b_hold);
959 }
960 
961 /*
962  * Release a hold on the specified buffer. If the hold count is 1, the buffer is
963  * placed on LRU or freed (depending on b_lru_ref).
964  */
965 void
966 xfs_buf_rele(
967         xfs_buf_t               *bp)
968 {
969         struct xfs_perag        *pag = bp->b_pag;
970         bool                    release;
971         bool                    freebuf = false;
972 
973         trace_xfs_buf_rele(bp, _RET_IP_);
974 
975         if (!pag) {
976                 ASSERT(list_empty(&bp->b_lru));
977                 if (atomic_dec_and_test(&bp->b_hold)) {
978                         xfs_buf_ioacct_dec(bp);
979                         xfs_buf_free(bp);
980                 }
981                 return;
982         }
983 
984         ASSERT(atomic_read(&bp->b_hold) > 0);
985 
986         release = atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock);
987         spin_lock(&bp->b_lock);
988         if (!release) {
989                 /*
990                  * Drop the in-flight state if the buffer is already on the LRU
991                  * and it holds the only reference. This is racy because we
992                  * haven't acquired the pag lock, but the use of _XBF_IN_FLIGHT
993                  * ensures the decrement occurs only once per-buf.
994                  */
995                 if ((atomic_read(&bp->b_hold) == 1) && !list_empty(&bp->b_lru))
996                         __xfs_buf_ioacct_dec(bp);
997                 goto out_unlock;
998         }
999 
1000         /* the last reference has been dropped ... */
1001         __xfs_buf_ioacct_dec(bp);
1002         if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
1003                 /*
1004                  * If the buffer is added to the LRU take a new reference to the
1005                  * buffer for the LRU and clear the (now stale) dispose list
1006                  * state flag
1007                  */
1008                 if (list_lru_add(&bp->b_target->bt_lru, &bp->b_lru)) {
1009                         bp->b_state &= ~XFS_BSTATE_DISPOSE;
1010                         atomic_inc(&bp->b_hold);
1011                 }
1012                 spin_unlock(&pag->pag_buf_lock);
1013         } else {
1014                 /*
1015                  * most of the time buffers will already be removed from the
1016                  * LRU, so optimise that case by checking for the
1017                  * XFS_BSTATE_DISPOSE flag indicating the last list the buffer
1018                  * was on was the disposal list
1019                  */
1020                 if (!(bp->b_state & XFS_BSTATE_DISPOSE)) {
1021                         list_lru_del(&bp->b_target->bt_lru, &bp->b_lru);
1022                 } else {
1023                         ASSERT(list_empty(&bp->b_lru));
1024                 }
1025 
1026                 ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1027                 rhashtable_remove_fast(&pag->pag_buf_hash, &bp->b_rhash_head,
1028                                        xfs_buf_hash_params);
1029                 spin_unlock(&pag->pag_buf_lock);
1030                 xfs_perag_put(pag);
1031                 freebuf = true;
1032         }
1033 
1034 out_unlock:
1035         spin_unlock(&bp->b_lock);
1036 
1037         if (freebuf)
1038                 xfs_buf_free(bp);
1039 }
1040 
1041 
1042 /*
1043  *      Lock a buffer object, if it is not already locked.
1044  *
1045  *      If we come across a stale, pinned, locked buffer, we know that we are
1046  *      being asked to lock a buffer that has been reallocated. Because it is
1047  *      pinned, we know that the log has not been pushed to disk and hence it
1048  *      will still be locked.  Rather than continuing to have trylock attempts
1049  *      fail until someone else pushes the log, push it ourselves before
1050  *      returning.  This means that the xfsaild will not get stuck trying
1051  *      to push on stale inode buffers.
1052  */
1053 int
1054 xfs_buf_trylock(
1055         struct xfs_buf          *bp)
1056 {
1057         int                     locked;
1058 
1059         locked = down_trylock(&bp->b_sema) == 0;
1060         if (locked) {
1061                 XB_SET_OWNER(bp);
1062                 trace_xfs_buf_trylock(bp, _RET_IP_);
1063         } else {
1064                 trace_xfs_buf_trylock_fail(bp, _RET_IP_);
1065         }
1066         return locked;
1067 }
1068 
1069 /*
1070  *      Lock a buffer object.
1071  *
1072  *      If we come across a stale, pinned, locked buffer, we know that we
1073  *      are being asked to lock a buffer that has been reallocated. Because
1074  *      it is pinned, we know that the log has not been pushed to disk and
1075  *      hence it will still be locked. Rather than sleeping until someone
1076  *      else pushes the log, push it ourselves before trying to get the lock.
1077  */
1078 void
1079 xfs_buf_lock(
1080         struct xfs_buf          *bp)
1081 {
1082         trace_xfs_buf_lock(bp, _RET_IP_);
1083 
1084         if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
1085                 xfs_log_force(bp->b_target->bt_mount, 0);
1086         down(&bp->b_sema);
1087         XB_SET_OWNER(bp);
1088 
1089         trace_xfs_buf_lock_done(bp, _RET_IP_);
1090 }
1091 
1092 void
1093 xfs_buf_unlock(
1094         struct xfs_buf          *bp)
1095 {
1096         ASSERT(xfs_buf_islocked(bp));
1097 
1098         XB_CLEAR_OWNER(bp);
1099         up(&bp->b_sema);
1100 
1101         trace_xfs_buf_unlock(bp, _RET_IP_);
1102 }
1103 
1104 STATIC void
1105 xfs_buf_wait_unpin(
1106         xfs_buf_t               *bp)
1107 {
1108         DECLARE_WAITQUEUE       (wait, current);
1109 
1110         if (atomic_read(&bp->b_pin_count) == 0)
1111                 return;
1112 
1113         add_wait_queue(&bp->b_waiters, &wait);
1114         for (;;) {
1115                 set_current_state(TASK_UNINTERRUPTIBLE);
1116                 if (atomic_read(&bp->b_pin_count) == 0)
1117                         break;
1118                 io_schedule();
1119         }
1120         remove_wait_queue(&bp->b_waiters, &wait);
1121         set_current_state(TASK_RUNNING);
1122 }
1123 
1124 /*
1125  *      Buffer Utility Routines
1126  */
1127 
1128 void
1129 xfs_buf_ioend(
1130         struct xfs_buf  *bp)
1131 {
1132         bool            read = bp->b_flags & XBF_READ;
1133 
1134         trace_xfs_buf_iodone(bp, _RET_IP_);
1135 
1136         bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
1137 
1138         /*
1139          * Pull in IO completion errors now. We are guaranteed to be running
1140          * single threaded, so we don't need the lock to read b_io_error.
1141          */
1142         if (!bp->b_error && bp->b_io_error)
1143                 xfs_buf_ioerror(bp, bp->b_io_error);
1144 
1145         /* Only validate buffers that were read without errors */
1146         if (read && !bp->b_error && bp->b_ops) {
1147                 ASSERT(!bp->b_iodone);
1148                 bp->b_ops->verify_read(bp);
1149         }
1150 
1151         if (!bp->b_error)
1152                 bp->b_flags |= XBF_DONE;
1153 
1154         if (bp->b_iodone)
1155                 (*(bp->b_iodone))(bp);
1156         else if (bp->b_flags & XBF_ASYNC)
1157                 xfs_buf_relse(bp);
1158         else
1159                 complete(&bp->b_iowait);
1160 }
1161 
1162 static void
1163 xfs_buf_ioend_work(
1164         struct work_struct      *work)
1165 {
1166         struct xfs_buf          *bp =
1167                 container_of(work, xfs_buf_t, b_ioend_work);
1168 
1169         xfs_buf_ioend(bp);
1170 }
1171 
1172 static void
1173 xfs_buf_ioend_async(
1174         struct xfs_buf  *bp)
1175 {
1176         INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work);
1177         queue_work(bp->b_ioend_wq, &bp->b_ioend_work);
1178 }
1179 
1180 void
1181 xfs_buf_ioerror(
1182         xfs_buf_t               *bp,
1183         int                     error)
1184 {
1185         ASSERT(error <= 0 && error >= -1000);
1186         bp->b_error = error;
1187         trace_xfs_buf_ioerror(bp, error, _RET_IP_);
1188 }
1189 
1190 void
1191 xfs_buf_ioerror_alert(
1192         struct xfs_buf          *bp,
1193         const char              *func)
1194 {
1195         xfs_alert(bp->b_target->bt_mount,
1196 "metadata I/O error: block 0x%llx (\"%s\") error %d numblks %d",
1197                 (__uint64_t)XFS_BUF_ADDR(bp), func, -bp->b_error, bp->b_length);
1198 }
1199 
1200 int
1201 xfs_bwrite(
1202         struct xfs_buf          *bp)
1203 {
1204         int                     error;
1205 
1206         ASSERT(xfs_buf_islocked(bp));
1207 
1208         bp->b_flags |= XBF_WRITE;
1209         bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q |
1210                          XBF_WRITE_FAIL | XBF_DONE);
1211 
1212         error = xfs_buf_submit_wait(bp);
1213         if (error) {
1214                 xfs_force_shutdown(bp->b_target->bt_mount,
1215                                    SHUTDOWN_META_IO_ERROR);
1216         }
1217         return error;
1218 }
1219 
1220 static void
1221 xfs_buf_bio_end_io(
1222         struct bio              *bio)
1223 {
1224         struct xfs_buf          *bp = (struct xfs_buf *)bio->bi_private;
1225 
1226         /*
1227          * don't overwrite existing errors - otherwise we can lose errors on
1228          * buffers that require multiple bios to complete.
1229          */
1230         if (bio->bi_error)
1231                 cmpxchg(&bp->b_io_error, 0, bio->bi_error);
1232 
1233         if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
1234                 invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
1235 
1236         if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
1237                 xfs_buf_ioend_async(bp);
1238         bio_put(bio);
1239 }
1240 
1241 static void
1242 xfs_buf_ioapply_map(
1243         struct xfs_buf  *bp,
1244         int             map,
1245         int             *buf_offset,
1246         int             *count,
1247         int             op,
1248         int             op_flags)
1249 {
1250         int             page_index;
1251         int             total_nr_pages = bp->b_page_count;
1252         int             nr_pages;
1253         struct bio      *bio;
1254         sector_t        sector =  bp->b_maps[map].bm_bn;
1255         int             size;
1256         int             offset;
1257 
1258         total_nr_pages = bp->b_page_count;
1259 
1260         /* skip the pages in the buffer before the start offset */
1261         page_index = 0;
1262         offset = *buf_offset;
1263         while (offset >= PAGE_SIZE) {
1264                 page_index++;
1265                 offset -= PAGE_SIZE;
1266         }
1267 
1268         /*
1269          * Limit the IO size to the length of the current vector, and update the
1270          * remaining IO count for the next time around.
1271          */
1272         size = min_t(int, BBTOB(bp->b_maps[map].bm_len), *count);
1273         *count -= size;
1274         *buf_offset += size;
1275 
1276 next_chunk:
1277         atomic_inc(&bp->b_io_remaining);
1278         nr_pages = min(total_nr_pages, BIO_MAX_PAGES);
1279 
1280         bio = bio_alloc(GFP_NOIO, nr_pages);
1281         bio->bi_bdev = bp->b_target->bt_bdev;
1282         bio->bi_iter.bi_sector = sector;
1283         bio->bi_end_io = xfs_buf_bio_end_io;
1284         bio->bi_private = bp;
1285         bio_set_op_attrs(bio, op, op_flags);
1286 
1287         for (; size && nr_pages; nr_pages--, page_index++) {
1288                 int     rbytes, nbytes = PAGE_SIZE - offset;
1289 
1290                 if (nbytes > size)
1291                         nbytes = size;
1292 
1293                 rbytes = bio_add_page(bio, bp->b_pages[page_index], nbytes,
1294                                       offset);
1295                 if (rbytes < nbytes)
1296                         break;
1297 
1298                 offset = 0;
1299                 sector += BTOBB(nbytes);
1300                 size -= nbytes;
1301                 total_nr_pages--;
1302         }
1303 
1304         if (likely(bio->bi_iter.bi_size)) {
1305                 if (xfs_buf_is_vmapped(bp)) {
1306                         flush_kernel_vmap_range(bp->b_addr,
1307                                                 xfs_buf_vmap_len(bp));
1308                 }
1309                 submit_bio(bio);
1310                 if (size)
1311                         goto next_chunk;
1312         } else {
1313                 /*
1314                  * This is guaranteed not to be the last io reference count
1315                  * because the caller (xfs_buf_submit) holds a count itself.
1316                  */
1317                 atomic_dec(&bp->b_io_remaining);
1318                 xfs_buf_ioerror(bp, -EIO);
1319                 bio_put(bio);
1320         }
1321 
1322 }
1323 
1324 STATIC void
1325 _xfs_buf_ioapply(
1326         struct xfs_buf  *bp)
1327 {
1328         struct blk_plug plug;
1329         int             op;
1330         int             op_flags = 0;
1331         int             offset;
1332         int             size;
1333         int             i;
1334 
1335         /*
1336          * Make sure we capture only current IO errors rather than stale errors
1337          * left over from previous use of the buffer (e.g. failed readahead).
1338          */
1339         bp->b_error = 0;
1340 
1341         /*
1342          * Initialize the I/O completion workqueue if we haven't yet or the
1343          * submitter has not opted to specify a custom one.
1344          */
1345         if (!bp->b_ioend_wq)
1346                 bp->b_ioend_wq = bp->b_target->bt_mount->m_buf_workqueue;
1347 
1348         if (bp->b_flags & XBF_WRITE) {
1349                 op = REQ_OP_WRITE;
1350                 if (bp->b_flags & XBF_SYNCIO)
1351                         op_flags = REQ_SYNC;
1352                 if (bp->b_flags & XBF_FUA)
1353                         op_flags |= REQ_FUA;
1354                 if (bp->b_flags & XBF_FLUSH)
1355                         op_flags |= REQ_PREFLUSH;
1356 
1357                 /*
1358                  * Run the write verifier callback function if it exists. If
1359                  * this function fails it will mark the buffer with an error and
1360                  * the IO should not be dispatched.
1361                  */
1362                 if (bp->b_ops) {
1363                         bp->b_ops->verify_write(bp);
1364                         if (bp->b_error) {
1365                                 xfs_force_shutdown(bp->b_target->bt_mount,
1366                                                    SHUTDOWN_CORRUPT_INCORE);
1367                                 return;
1368                         }
1369                 } else if (bp->b_bn != XFS_BUF_DADDR_NULL) {
1370                         struct xfs_mount *mp = bp->b_target->bt_mount;
1371 
1372                         /*
1373                          * non-crc filesystems don't attach verifiers during
1374                          * log recovery, so don't warn for such filesystems.
1375                          */
1376                         if (xfs_sb_version_hascrc(&mp->m_sb)) {
1377                                 xfs_warn(mp,
1378                                         "%s: no ops on block 0x%llx/0x%x",
1379                                         __func__, bp->b_bn, bp->b_length);
1380                                 xfs_hex_dump(bp->b_addr, 64);
1381                                 dump_stack();
1382                         }
1383                 }
1384         } else if (bp->b_flags & XBF_READ_AHEAD) {
1385                 op = REQ_OP_READ;
1386                 op_flags = REQ_RAHEAD;
1387         } else {
1388                 op = REQ_OP_READ;
1389         }
1390 
1391         /* we only use the buffer cache for meta-data */
1392         op_flags |= REQ_META;
1393 
1394         /*
1395          * Walk all the vectors issuing IO on them. Set up the initial offset
1396          * into the buffer and the desired IO size before we start -
1397          * _xfs_buf_ioapply_vec() will modify them appropriately for each
1398          * subsequent call.
1399          */
1400         offset = bp->b_offset;
1401         size = BBTOB(bp->b_io_length);
1402         blk_start_plug(&plug);
1403         for (i = 0; i < bp->b_map_count; i++) {
1404                 xfs_buf_ioapply_map(bp, i, &offset, &size, op, op_flags);
1405                 if (bp->b_error)
1406                         break;
1407                 if (size <= 0)
1408                         break;  /* all done */
1409         }
1410         blk_finish_plug(&plug);
1411 }
1412 
1413 /*
1414  * Asynchronous IO submission path. This transfers the buffer lock ownership and
1415  * the current reference to the IO. It is not safe to reference the buffer after
1416  * a call to this function unless the caller holds an additional reference
1417  * itself.
1418  */
1419 void
1420 xfs_buf_submit(
1421         struct xfs_buf  *bp)
1422 {
1423         trace_xfs_buf_submit(bp, _RET_IP_);
1424 
1425         ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1426         ASSERT(bp->b_flags & XBF_ASYNC);
1427 
1428         /* on shutdown we stale and complete the buffer immediately */
1429         if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
1430                 xfs_buf_ioerror(bp, -EIO);
1431                 bp->b_flags &= ~XBF_DONE;
1432                 xfs_buf_stale(bp);
1433                 xfs_buf_ioend(bp);
1434                 return;
1435         }
1436 
1437         if (bp->b_flags & XBF_WRITE)
1438                 xfs_buf_wait_unpin(bp);
1439 
1440         /* clear the internal error state to avoid spurious errors */
1441         bp->b_io_error = 0;
1442 
1443         /*
1444          * The caller's reference is released during I/O completion.
1445          * This occurs some time after the last b_io_remaining reference is
1446          * released, so after we drop our Io reference we have to have some
1447          * other reference to ensure the buffer doesn't go away from underneath
1448          * us. Take a direct reference to ensure we have safe access to the
1449          * buffer until we are finished with it.
1450          */
1451         xfs_buf_hold(bp);
1452 
1453         /*
1454          * Set the count to 1 initially, this will stop an I/O completion
1455          * callout which happens before we have started all the I/O from calling
1456          * xfs_buf_ioend too early.
1457          */
1458         atomic_set(&bp->b_io_remaining, 1);
1459         xfs_buf_ioacct_inc(bp);
1460         _xfs_buf_ioapply(bp);
1461 
1462         /*
1463          * If _xfs_buf_ioapply failed, we can get back here with only the IO
1464          * reference we took above. If we drop it to zero, run completion so
1465          * that we don't return to the caller with completion still pending.
1466          */
1467         if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
1468                 if (bp->b_error)
1469                         xfs_buf_ioend(bp);
1470                 else
1471                         xfs_buf_ioend_async(bp);
1472         }
1473 
1474         xfs_buf_rele(bp);
1475         /* Note: it is not safe to reference bp now we've dropped our ref */
1476 }
1477 
1478 /*
1479  * Synchronous buffer IO submission path, read or write.
1480  */
1481 int
1482 xfs_buf_submit_wait(
1483         struct xfs_buf  *bp)
1484 {
1485         int             error;
1486 
1487         trace_xfs_buf_submit_wait(bp, _RET_IP_);
1488 
1489         ASSERT(!(bp->b_flags & (_XBF_DELWRI_Q | XBF_ASYNC)));
1490 
1491         if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
1492                 xfs_buf_ioerror(bp, -EIO);
1493                 xfs_buf_stale(bp);
1494                 bp->b_flags &= ~XBF_DONE;
1495                 return -EIO;
1496         }
1497 
1498         if (bp->b_flags & XBF_WRITE)
1499                 xfs_buf_wait_unpin(bp);
1500 
1501         /* clear the internal error state to avoid spurious errors */
1502         bp->b_io_error = 0;
1503 
1504         /*
1505          * For synchronous IO, the IO does not inherit the submitters reference
1506          * count, nor the buffer lock. Hence we cannot release the reference we
1507          * are about to take until we've waited for all IO completion to occur,
1508          * including any xfs_buf_ioend_async() work that may be pending.
1509          */
1510         xfs_buf_hold(bp);
1511 
1512         /*
1513          * Set the count to 1 initially, this will stop an I/O completion
1514          * callout which happens before we have started all the I/O from calling
1515          * xfs_buf_ioend too early.
1516          */
1517         atomic_set(&bp->b_io_remaining, 1);
1518         _xfs_buf_ioapply(bp);
1519 
1520         /*
1521          * make sure we run completion synchronously if it raced with us and is
1522          * already complete.
1523          */
1524         if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
1525                 xfs_buf_ioend(bp);
1526 
1527         /* wait for completion before gathering the error from the buffer */
1528         trace_xfs_buf_iowait(bp, _RET_IP_);
1529         wait_for_completion(&bp->b_iowait);
1530         trace_xfs_buf_iowait_done(bp, _RET_IP_);
1531         error = bp->b_error;
1532 
1533         /*
1534          * all done now, we can release the hold that keeps the buffer
1535          * referenced for the entire IO.
1536          */
1537         xfs_buf_rele(bp);
1538         return error;
1539 }
1540 
1541 void *
1542 xfs_buf_offset(
1543         struct xfs_buf          *bp,
1544         size_t                  offset)
1545 {
1546         struct page             *page;
1547 
1548         if (bp->b_addr)
1549                 return bp->b_addr + offset;
1550 
1551         offset += bp->b_offset;
1552         page = bp->b_pages[offset >> PAGE_SHIFT];
1553         return page_address(page) + (offset & (PAGE_SIZE-1));
1554 }
1555 
1556 /*
1557  *      Move data into or out of a buffer.
1558  */
1559 void
1560 xfs_buf_iomove(
1561         xfs_buf_t               *bp,    /* buffer to process            */
1562         size_t                  boff,   /* starting buffer offset       */
1563         size_t                  bsize,  /* length to copy               */
1564         void                    *data,  /* data address                 */
1565         xfs_buf_rw_t            mode)   /* read/write/zero flag         */
1566 {
1567         size_t                  bend;
1568 
1569         bend = boff + bsize;
1570         while (boff < bend) {
1571                 struct page     *page;
1572                 int             page_index, page_offset, csize;
1573 
1574                 page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
1575                 page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
1576                 page = bp->b_pages[page_index];
1577                 csize = min_t(size_t, PAGE_SIZE - page_offset,
1578                                       BBTOB(bp->b_io_length) - boff);
1579 
1580                 ASSERT((csize + page_offset) <= PAGE_SIZE);
1581 
1582                 switch (mode) {
1583                 case XBRW_ZERO:
1584                         memset(page_address(page) + page_offset, 0, csize);
1585                         break;
1586                 case XBRW_READ:
1587                         memcpy(data, page_address(page) + page_offset, csize);
1588                         break;
1589                 case XBRW_WRITE:
1590                         memcpy(page_address(page) + page_offset, data, csize);
1591                 }
1592 
1593                 boff += csize;
1594                 data += csize;
1595         }
1596 }
1597 
1598 /*
1599  *      Handling of buffer targets (buftargs).
1600  */
1601 
1602 /*
1603  * Wait for any bufs with callbacks that have been submitted but have not yet
1604  * returned. These buffers will have an elevated hold count, so wait on those
1605  * while freeing all the buffers only held by the LRU.
1606  */
1607 static enum lru_status
1608 xfs_buftarg_wait_rele(
1609         struct list_head        *item,
1610         struct list_lru_one     *lru,
1611         spinlock_t              *lru_lock,
1612         void                    *arg)
1613 
1614 {
1615         struct xfs_buf          *bp = container_of(item, struct xfs_buf, b_lru);
1616         struct list_head        *dispose = arg;
1617 
1618         if (atomic_read(&bp->b_hold) > 1) {
1619                 /* need to wait, so skip it this pass */
1620                 trace_xfs_buf_wait_buftarg(bp, _RET_IP_);
1621                 return LRU_SKIP;
1622         }
1623         if (!spin_trylock(&bp->b_lock))
1624                 return LRU_SKIP;
1625 
1626         /*
1627          * clear the LRU reference count so the buffer doesn't get
1628          * ignored in xfs_buf_rele().
1629          */
1630         atomic_set(&bp->b_lru_ref, 0);
1631         bp->b_state |= XFS_BSTATE_DISPOSE;
1632         list_lru_isolate_move(lru, item, dispose);
1633         spin_unlock(&bp->b_lock);
1634         return LRU_REMOVED;
1635 }
1636 
1637 void
1638 xfs_wait_buftarg(
1639         struct xfs_buftarg      *btp)
1640 {
1641         LIST_HEAD(dispose);
1642         int loop = 0;
1643 
1644         /*
1645          * First wait on the buftarg I/O count for all in-flight buffers to be
1646          * released. This is critical as new buffers do not make the LRU until
1647          * they are released.
1648          *
1649          * Next, flush the buffer workqueue to ensure all completion processing
1650          * has finished. Just waiting on buffer locks is not sufficient for
1651          * async IO as the reference count held over IO is not released until
1652          * after the buffer lock is dropped. Hence we need to ensure here that
1653          * all reference counts have been dropped before we start walking the
1654          * LRU list.
1655          */
1656         while (percpu_counter_sum(&btp->bt_io_count))
1657                 delay(100);
1658         flush_workqueue(btp->bt_mount->m_buf_workqueue);
1659 
1660         /* loop until there is nothing left on the lru list. */
1661         while (list_lru_count(&btp->bt_lru)) {
1662                 list_lru_walk(&btp->bt_lru, xfs_buftarg_wait_rele,
1663                               &dispose, LONG_MAX);
1664 
1665                 while (!list_empty(&dispose)) {
1666                         struct xfs_buf *bp;
1667                         bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1668                         list_del_init(&bp->b_lru);
1669                         if (bp->b_flags & XBF_WRITE_FAIL) {
1670                                 xfs_alert(btp->bt_mount,
1671 "Corruption Alert: Buffer at block 0x%llx had permanent write failures!",
1672                                         (long long)bp->b_bn);
1673                                 xfs_alert(btp->bt_mount,
1674 "Please run xfs_repair to determine the extent of the problem.");
1675                         }
1676                         xfs_buf_rele(bp);
1677                 }
1678                 if (loop++ != 0)
1679                         delay(100);
1680         }
1681 }
1682 
1683 static enum lru_status
1684 xfs_buftarg_isolate(
1685         struct list_head        *item,
1686         struct list_lru_one     *lru,
1687         spinlock_t              *lru_lock,
1688         void                    *arg)
1689 {
1690         struct xfs_buf          *bp = container_of(item, struct xfs_buf, b_lru);
1691         struct list_head        *dispose = arg;
1692 
1693         /*
1694          * we are inverting the lru lock/bp->b_lock here, so use a trylock.
1695          * If we fail to get the lock, just skip it.
1696          */
1697         if (!spin_trylock(&bp->b_lock))
1698                 return LRU_SKIP;
1699         /*
1700          * Decrement the b_lru_ref count unless the value is already
1701          * zero. If the value is already zero, we need to reclaim the
1702          * buffer, otherwise it gets another trip through the LRU.
1703          */
1704         if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
1705                 spin_unlock(&bp->b_lock);
1706                 return LRU_ROTATE;
1707         }
1708 
1709         bp->b_state |= XFS_BSTATE_DISPOSE;
1710         list_lru_isolate_move(lru, item, dispose);
1711         spin_unlock(&bp->b_lock);
1712         return LRU_REMOVED;
1713 }
1714 
1715 static unsigned long
1716 xfs_buftarg_shrink_scan(
1717         struct shrinker         *shrink,
1718         struct shrink_control   *sc)
1719 {
1720         struct xfs_buftarg      *btp = container_of(shrink,
1721                                         struct xfs_buftarg, bt_shrinker);
1722         LIST_HEAD(dispose);
1723         unsigned long           freed;
1724 
1725         freed = list_lru_shrink_walk(&btp->bt_lru, sc,
1726                                      xfs_buftarg_isolate, &dispose);
1727 
1728         while (!list_empty(&dispose)) {
1729                 struct xfs_buf *bp;
1730                 bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1731                 list_del_init(&bp->b_lru);
1732                 xfs_buf_rele(bp);
1733         }
1734 
1735         return freed;
1736 }
1737 
1738 static unsigned long
1739 xfs_buftarg_shrink_count(
1740         struct shrinker         *shrink,
1741         struct shrink_control   *sc)
1742 {
1743         struct xfs_buftarg      *btp = container_of(shrink,
1744                                         struct xfs_buftarg, bt_shrinker);
1745         return list_lru_shrink_count(&btp->bt_lru, sc);
1746 }
1747 
1748 void
1749 xfs_free_buftarg(
1750         struct xfs_mount        *mp,
1751         struct xfs_buftarg      *btp)
1752 {
1753         unregister_shrinker(&btp->bt_shrinker);
1754         ASSERT(percpu_counter_sum(&btp->bt_io_count) == 0);
1755         percpu_counter_destroy(&btp->bt_io_count);
1756         list_lru_destroy(&btp->bt_lru);
1757 
1758         xfs_blkdev_issue_flush(btp);
1759 
1760         kmem_free(btp);
1761 }
1762 
1763 int
1764 xfs_setsize_buftarg(
1765         xfs_buftarg_t           *btp,
1766         unsigned int            sectorsize)
1767 {
1768         /* Set up metadata sector size info */
1769         btp->bt_meta_sectorsize = sectorsize;
1770         btp->bt_meta_sectormask = sectorsize - 1;
1771 
1772         if (set_blocksize(btp->bt_bdev, sectorsize)) {
1773                 xfs_warn(btp->bt_mount,
1774                         "Cannot set_blocksize to %u on device %pg",
1775                         sectorsize, btp->bt_bdev);
1776                 return -EINVAL;
1777         }
1778 
1779         /* Set up device logical sector size mask */
1780         btp->bt_logical_sectorsize = bdev_logical_block_size(btp->bt_bdev);
1781         btp->bt_logical_sectormask = bdev_logical_block_size(btp->bt_bdev) - 1;
1782 
1783         return 0;
1784 }
1785 
1786 /*
1787  * When allocating the initial buffer target we have not yet
1788  * read in the superblock, so don't know what sized sectors
1789  * are being used at this early stage.  Play safe.
1790  */
1791 STATIC int
1792 xfs_setsize_buftarg_early(
1793         xfs_buftarg_t           *btp,
1794         struct block_device     *bdev)
1795 {
1796         return xfs_setsize_buftarg(btp, bdev_logical_block_size(bdev));
1797 }
1798 
1799 xfs_buftarg_t *
1800 xfs_alloc_buftarg(
1801         struct xfs_mount        *mp,
1802         struct block_device     *bdev)
1803 {
1804         xfs_buftarg_t           *btp;
1805 
1806         btp = kmem_zalloc(sizeof(*btp), KM_SLEEP | KM_NOFS);
1807 
1808         btp->bt_mount = mp;
1809         btp->bt_dev =  bdev->bd_dev;
1810         btp->bt_bdev = bdev;
1811 
1812         if (xfs_setsize_buftarg_early(btp, bdev))
1813                 goto error;
1814 
1815         if (list_lru_init(&btp->bt_lru))
1816                 goto error;
1817 
1818         if (percpu_counter_init(&btp->bt_io_count, 0, GFP_KERNEL))
1819                 goto error;
1820 
1821         btp->bt_shrinker.count_objects = xfs_buftarg_shrink_count;
1822         btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
1823         btp->bt_shrinker.seeks = DEFAULT_SEEKS;
1824         btp->bt_shrinker.flags = SHRINKER_NUMA_AWARE;
1825         register_shrinker(&btp->bt_shrinker);
1826         return btp;
1827 
1828 error:
1829         kmem_free(btp);
1830         return NULL;
1831 }
1832 
1833 /*
1834  * Cancel a delayed write list.
1835  *
1836  * Remove each buffer from the list, clear the delwri queue flag and drop the
1837  * associated buffer reference.
1838  */
1839 void
1840 xfs_buf_delwri_cancel(
1841         struct list_head        *list)
1842 {
1843         struct xfs_buf          *bp;
1844 
1845         while (!list_empty(list)) {
1846                 bp = list_first_entry(list, struct xfs_buf, b_list);
1847 
1848                 xfs_buf_lock(bp);
1849                 bp->b_flags &= ~_XBF_DELWRI_Q;
1850                 list_del_init(&bp->b_list);
1851                 xfs_buf_relse(bp);
1852         }
1853 }
1854 
1855 /*
1856  * Add a buffer to the delayed write list.
1857  *
1858  * This queues a buffer for writeout if it hasn't already been.  Note that
1859  * neither this routine nor the buffer list submission functions perform
1860  * any internal synchronization.  It is expected that the lists are thread-local
1861  * to the callers.
1862  *
1863  * Returns true if we queued up the buffer, or false if it already had
1864  * been on the buffer list.
1865  */
1866 bool
1867 xfs_buf_delwri_queue(
1868         struct xfs_buf          *bp,
1869         struct list_head        *list)
1870 {
1871         ASSERT(xfs_buf_islocked(bp));
1872         ASSERT(!(bp->b_flags & XBF_READ));
1873 
1874         /*
1875          * If the buffer is already marked delwri it already is queued up
1876          * by someone else for imediate writeout.  Just ignore it in that
1877          * case.
1878          */
1879         if (bp->b_flags & _XBF_DELWRI_Q) {
1880                 trace_xfs_buf_delwri_queued(bp, _RET_IP_);
1881                 return false;
1882         }
1883 
1884         trace_xfs_buf_delwri_queue(bp, _RET_IP_);
1885 
1886         /*
1887          * If a buffer gets written out synchronously or marked stale while it
1888          * is on a delwri list we lazily remove it. To do this, the other party
1889          * clears the  _XBF_DELWRI_Q flag but otherwise leaves the buffer alone.
1890          * It remains referenced and on the list.  In a rare corner case it
1891          * might get readded to a delwri list after the synchronous writeout, in
1892          * which case we need just need to re-add the flag here.
1893          */
1894         bp->b_flags |= _XBF_DELWRI_Q;
1895         if (list_empty(&bp->b_list)) {
1896                 atomic_inc(&bp->b_hold);
1897                 list_add_tail(&bp->b_list, list);
1898         }
1899 
1900         return true;
1901 }
1902 
1903 /*
1904  * Compare function is more complex than it needs to be because
1905  * the return value is only 32 bits and we are doing comparisons
1906  * on 64 bit values
1907  */
1908 static int
1909 xfs_buf_cmp(
1910         void            *priv,
1911         struct list_head *a,
1912         struct list_head *b)
1913 {
1914         struct xfs_buf  *ap = container_of(a, struct xfs_buf, b_list);
1915         struct xfs_buf  *bp = container_of(b, struct xfs_buf, b_list);
1916         xfs_daddr_t             diff;
1917 
1918         diff = ap->b_maps[0].bm_bn - bp->b_maps[0].bm_bn;
1919         if (diff < 0)
1920                 return -1;
1921         if (diff > 0)
1922                 return 1;
1923         return 0;
1924 }
1925 
1926 /*
1927  * submit buffers for write.
1928  *
1929  * When we have a large buffer list, we do not want to hold all the buffers
1930  * locked while we block on the request queue waiting for IO dispatch. To avoid
1931  * this problem, we lock and submit buffers in groups of 50, thereby minimising
1932  * the lock hold times for lists which may contain thousands of objects.
1933  *
1934  * To do this, we sort the buffer list before we walk the list to lock and
1935  * submit buffers, and we plug and unplug around each group of buffers we
1936  * submit.
1937  */
1938 static int
1939 xfs_buf_delwri_submit_buffers(
1940         struct list_head        *buffer_list,
1941         struct list_head        *wait_list)
1942 {
1943         struct xfs_buf          *bp, *n;
1944         LIST_HEAD               (submit_list);
1945         int                     pinned = 0;
1946         struct blk_plug         plug;
1947 
1948         list_sort(NULL, buffer_list, xfs_buf_cmp);
1949 
1950         blk_start_plug(&plug);
1951         list_for_each_entry_safe(bp, n, buffer_list, b_list) {
1952                 if (!wait_list) {
1953                         if (xfs_buf_ispinned(bp)) {
1954                                 pinned++;
1955                                 continue;
1956                         }
1957                         if (!xfs_buf_trylock(bp))
1958                                 continue;
1959                 } else {
1960                         xfs_buf_lock(bp);
1961                 }
1962 
1963                 /*
1964                  * Someone else might have written the buffer synchronously or
1965                  * marked it stale in the meantime.  In that case only the
1966                  * _XBF_DELWRI_Q flag got cleared, and we have to drop the
1967                  * reference and remove it from the list here.
1968                  */
1969                 if (!(bp->b_flags & _XBF_DELWRI_Q)) {
1970                         list_del_init(&bp->b_list);
1971                         xfs_buf_relse(bp);
1972                         continue;
1973                 }
1974 
1975                 trace_xfs_buf_delwri_split(bp, _RET_IP_);
1976 
1977                 /*
1978                  * We do all IO submission async. This means if we need
1979                  * to wait for IO completion we need to take an extra
1980                  * reference so the buffer is still valid on the other
1981                  * side. We need to move the buffer onto the io_list
1982                  * at this point so the caller can still access it.
1983                  */
1984                 bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_WRITE_FAIL);
1985                 bp->b_flags |= XBF_WRITE | XBF_ASYNC;
1986                 if (wait_list) {
1987                         xfs_buf_hold(bp);
1988                         list_move_tail(&bp->b_list, wait_list);
1989                 } else
1990                         list_del_init(&bp->b_list);
1991 
1992                 xfs_buf_submit(bp);
1993         }
1994         blk_finish_plug(&plug);
1995 
1996         return pinned;
1997 }
1998 
1999 /*
2000  * Write out a buffer list asynchronously.
2001  *
2002  * This will take the @buffer_list, write all non-locked and non-pinned buffers
2003  * out and not wait for I/O completion on any of the buffers.  This interface
2004  * is only safely useable for callers that can track I/O completion by higher
2005  * level means, e.g. AIL pushing as the @buffer_list is consumed in this
2006  * function.
2007  */
2008 int
2009 xfs_buf_delwri_submit_nowait(
2010         struct list_head        *buffer_list)
2011 {
2012         return xfs_buf_delwri_submit_buffers(buffer_list, NULL);
2013 }
2014 
2015 /*
2016  * Write out a buffer list synchronously.
2017  *
2018  * This will take the @buffer_list, write all buffers out and wait for I/O
2019  * completion on all of the buffers. @buffer_list is consumed by the function,
2020  * so callers must have some other way of tracking buffers if they require such
2021  * functionality.
2022  */
2023 int
2024 xfs_buf_delwri_submit(
2025         struct list_head        *buffer_list)
2026 {
2027         LIST_HEAD               (wait_list);
2028         int                     error = 0, error2;
2029         struct xfs_buf          *bp;
2030 
2031         xfs_buf_delwri_submit_buffers(buffer_list, &wait_list);
2032 
2033         /* Wait for IO to complete. */
2034         while (!list_empty(&wait_list)) {
2035                 bp = list_first_entry(&wait_list, struct xfs_buf, b_list);
2036 
2037                 list_del_init(&bp->b_list);
2038 
2039                 /* locking the buffer will wait for async IO completion. */
2040                 xfs_buf_lock(bp);
2041                 error2 = bp->b_error;
2042                 xfs_buf_relse(bp);
2043                 if (!error)
2044                         error = error2;
2045         }
2046 
2047         return error;
2048 }
2049 
2050 int __init
2051 xfs_buf_init(void)
2052 {
2053         xfs_buf_zone = kmem_zone_init_flags(sizeof(xfs_buf_t), "xfs_buf",
2054                                                 KM_ZONE_HWALIGN, NULL);
2055         if (!xfs_buf_zone)
2056                 goto out;
2057 
2058         return 0;
2059 
2060  out:
2061         return -ENOMEM;
2062 }
2063 
2064 void
2065 xfs_buf_terminate(void)
2066 {
2067         kmem_zone_destroy(xfs_buf_zone);
2068 }
2069 

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