fs/xfs/xfs_buf.c

   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
  37 #include "xfs_sb.h"
  38 #include "xfs_inum.h"
  39 #include "xfs_log.h"
  40 #include "xfs_ag.h"
  41 #include "xfs_mount.h"
  42 #include "xfs_trace.h"
  43
  44 static kmem_zone_t *xfs_buf_zone;
  45 STATIC int xfsbufd(void *);
  46
  47 static struct workqueue_struct *xfslogd_workqueue;
  48 struct workqueue_struct *xfsdatad_workqueue;
  49 struct workqueue_struct *xfsconvertd_workqueue;
  50
  51 #ifdef XFS_BUF_LOCK_TRACKING
  52 # define XB_SET_OWNER(bp)       ((bp)->b_last_holder = current->pid)
  53 # define XB_CLEAR_OWNER(bp)     ((bp)->b_last_holder = -1)
  54 # define XB_GET_OWNER(bp)       ((bp)->b_last_holder)
  55 #else
  56 # define XB_SET_OWNER(bp)       do { } while (0)
  57 # define XB_CLEAR_OWNER(bp)     do { } while (0)
  58 # define XB_GET_OWNER(bp)       do { } while (0)
  59 #endif
  60
  61 #define xb_to_gfp(flags) \
  62         ((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : \
  63           ((flags) & XBF_DONT_BLOCK) ? GFP_NOFS : GFP_KERNEL) | __GFP_NOWARN)
  64
  65 #define xb_to_km(flags) \
  66          (((flags) & XBF_DONT_BLOCK) ? KM_NOFS : KM_SLEEP)
  67
  68 #define xfs_buf_allocate(flags) \
  69         kmem_zone_alloc(xfs_buf_zone, xb_to_km(flags))
  70 #define xfs_buf_deallocate(bp) \
  71         kmem_zone_free(xfs_buf_zone, (bp));
  72
  73 static inline int
  74 xfs_buf_is_vmapped(
  75         struct xfs_buf  *bp)
  76 {
  77         /*
  78          * Return true if the buffer is vmapped.
  79          *
  80          * The XBF_MAPPED flag is set if the buffer should be mapped, but the
  81          * code is clever enough to know it doesn't have to map a single page,
  82          * so the check has to be both for XBF_MAPPED and bp->b_page_count > 1.
  83          */
  84         return (bp->b_flags & XBF_MAPPED) && bp->b_page_count > 1;
  85 }
  86
  87 static inline int
  88 xfs_buf_vmap_len(
  89         struct xfs_buf  *bp)
  90 {
  91         return (bp->b_page_count * PAGE_SIZE) - bp->b_offset;
  92 }
  93
  94 /*
  95  * xfs_buf_lru_add - add a buffer to the LRU.
  96  *
  97  * The LRU takes a new reference to the buffer so that it will only be freed
  98  * once the shrinker takes the buffer off the LRU.
  99  */
 100 STATIC void
 101 xfs_buf_lru_add(
 102         struct xfs_buf  *bp)
 103 {
 104         struct xfs_buftarg *btp = bp->b_target;
 105
 106         spin_lock(&btp->bt_lru_lock);
 107         if (list_empty(&bp->b_lru)) {
 108                 atomic_inc(&bp->b_hold);
 109                 list_add_tail(&bp->b_lru, &btp->bt_lru);
 110                 btp->bt_lru_nr++;
 111         }
 112         spin_unlock(&btp->bt_lru_lock);
 113 }
 114
 115 /*
 116  * xfs_buf_lru_del - remove a buffer from the LRU
 117  *
 118  * The unlocked check is safe here because it only occurs when there are not
 119  * b_lru_ref counts left on the inode under the pag->pag_buf_lock. it is there
 120  * to optimise the shrinker removing the buffer from the LRU and calling
 121  * xfs_buf_free(). i.e. it removes an unnecessary round trip on the
 122  * bt_lru_lock.
 123  */
 124 STATIC void
 125 xfs_buf_lru_del(
 126         struct xfs_buf  *bp)
 127 {
 128         struct xfs_buftarg *btp = bp->b_target;
 129
 130         if (list_empty(&bp->b_lru))
 131                 return;
 132
 133         spin_lock(&btp->bt_lru_lock);
 134         if (!list_empty(&bp->b_lru)) {
 135                 list_del_init(&bp->b_lru);
 136                 btp->bt_lru_nr--;
 137         }
 138         spin_unlock(&btp->bt_lru_lock);
 139 }
 140
 141 /*
 142  * When we mark a buffer stale, we remove the buffer from the LRU and clear the
 143  * b_lru_ref count so that the buffer is freed immediately when the buffer
 144  * reference count falls to zero. If the buffer is already on the LRU, we need
 145  * to remove the reference that LRU holds on the buffer.
 146  *
 147  * This prevents build-up of stale buffers on the LRU.
 148  */
 149 void
 150 xfs_buf_stale(
 151         struct xfs_buf  *bp)
 152 {
 153         bp->b_flags |= XBF_STALE;
 154         xfs_buf_delwri_dequeue(bp);
 155         atomic_set(&(bp)->b_lru_ref, 0);
 156         if (!list_empty(&bp->b_lru)) {
 157                 struct xfs_buftarg *btp = bp->b_target;
 158
 159                 spin_lock(&btp->bt_lru_lock);
 160                 if (!list_empty(&bp->b_lru)) {
 161                         list_del_init(&bp->b_lru);
 162                         btp->bt_lru_nr--;
 163                         atomic_dec(&bp->b_hold);
 164                 }
 165                 spin_unlock(&btp->bt_lru_lock);
 166         }
 167         ASSERT(atomic_read(&bp->b_hold) >= 1);
 168 }
 169
 170 STATIC void
 171 _xfs_buf_initialize(
 172         xfs_buf_t               *bp,
 173         xfs_buftarg_t           *target,
 174         xfs_off_t               range_base,
 175         size_t                  range_length,
 176         xfs_buf_flags_t         flags)
 177 {
 178         /*
 179          * We don't want certain flags to appear in b_flags.
 180          */
 181         flags &= ~(XBF_LOCK|XBF_MAPPED|XBF_DONT_BLOCK|XBF_READ_AHEAD);
 182
 183         memset(bp, 0, sizeof(xfs_buf_t));
 184         atomic_set(&bp->b_hold, 1);
 185         atomic_set(&bp->b_lru_ref, 1);
 186         init_completion(&bp->b_iowait);
 187         INIT_LIST_HEAD(&bp->b_lru);
 188         INIT_LIST_HEAD(&bp->b_list);
 189         RB_CLEAR_NODE(&bp->b_rbnode);
 190         sema_init(&bp->b_sema, 0); /* held, no waiters */
 191         XB_SET_OWNER(bp);
 192         bp->b_target = target;
 193         bp->b_file_offset = range_base;
 194         /*
 195          * Set buffer_length and count_desired to the same value initially.
 196          * I/O routines should use count_desired, which will be the same in
 197          * most cases but may be reset (e.g. XFS recovery).
 198          */
 199         bp->b_buffer_length = bp->b_count_desired = range_length;
 200         bp->b_flags = flags;
 201         bp->b_bn = XFS_BUF_DADDR_NULL;
 202         atomic_set(&bp->b_pin_count, 0);
 203         init_waitqueue_head(&bp->b_waiters);
 204
 205         XFS_STATS_INC(xb_create);
 206
 207         trace_xfs_buf_init(bp, _RET_IP_);
 208 }
 209
 210 /*
 211  *      Allocate a page array capable of holding a specified number
 212  *      of pages, and point the page buf at it.
 213  */
 214 STATIC int
 215 _xfs_buf_get_pages(
 216         xfs_buf_t               *bp,
 217         int                     page_count,
 218         xfs_buf_flags_t         flags)
 219 {
 220         /* Make sure that we have a page list */
 221         if (bp->b_pages == NULL) {
 222                 bp->b_offset = xfs_buf_poff(bp->b_file_offset);
 223                 bp->b_page_count = page_count;
 224                 if (page_count <= XB_PAGES) {
 225                         bp->b_pages = bp->b_page_array;
 226                 } else {
 227                         bp->b_pages = kmem_alloc(sizeof(struct page *) *
 228                                         page_count, xb_to_km(flags));
 229                         if (bp->b_pages == NULL)
 230                                 return -ENOMEM;
 231                 }
 232                 memset(bp->b_pages, 0, sizeof(struct page *) * page_count);
 233         }
 234         return 0;
 235 }
 236
 237 /*
 238  *      Frees b_pages if it was allocated.
 239  */
 240 STATIC void
 241 _xfs_buf_free_pages(
 242         xfs_buf_t       *bp)
 243 {
 244         if (bp->b_pages != bp->b_page_array) {
 245                 kmem_free(bp->b_pages);
 246                 bp->b_pages = NULL;
 247         }
 248 }
 249
 250 /*
 251  *      Releases the specified buffer.
 252  *
 253  *      The modification state of any associated pages is left unchanged.
 254  *      The buffer most not be on any hash - use xfs_buf_rele instead for
 255  *      hashed and refcounted buffers
 256  */
 257 void
 258 xfs_buf_free(
 259         xfs_buf_t               *bp)
 260 {
 261         trace_xfs_buf_free(bp, _RET_IP_);
 262
 263         ASSERT(list_empty(&bp->b_lru));
 264
 265         if (bp->b_flags & _XBF_PAGES) {
 266                 uint            i;
 267
 268                 if (xfs_buf_is_vmapped(bp))
 269                         vm_unmap_ram(bp->b_addr - bp->b_offset,
 270                                         bp->b_page_count);
 271
 272                 for (i = 0; i < bp->b_page_count; i++) {
 273                         struct page     *page = bp->b_pages[i];
 274
 275                         __free_page(page);
 276                 }
 277         } else if (bp->b_flags & _XBF_KMEM)
 278                 kmem_free(bp->b_addr);
 279         _xfs_buf_free_pages(bp);
 280         xfs_buf_deallocate(bp);
 281 }
 282
 283 /*
 284  * Allocates all the pages for buffer in question and builds it's page list.
 285  */
 286 STATIC int
 287 xfs_buf_allocate_memory(
 288         xfs_buf_t               *bp,
 289         uint                    flags)
 290 {
 291         size_t                  size = bp->b_count_desired;
 292         size_t                  nbytes, offset;
 293         gfp_t                   gfp_mask = xb_to_gfp(flags);
 294         unsigned short          page_count, i;
 295         xfs_off_t               end;
 296         int                     error;
 297
 298         /*
 299          * for buffers that are contained within a single page, just allocate
 300          * the memory from the heap - there's no need for the complexity of
 301          * page arrays to keep allocation down to order 0.
 302          */
 303         if (bp->b_buffer_length < PAGE_SIZE) {
 304                 bp->b_addr = kmem_alloc(bp->b_buffer_length, xb_to_km(flags));
 305                 if (!bp->b_addr) {
 306                         /* low memory - use alloc_page loop instead */
 307                         goto use_alloc_page;
 308                 }
 309
 310                 if (((unsigned long)(bp->b_addr + bp->b_buffer_length - 1) &
 311                                                                 PAGE_MASK) !=
 312                     ((unsigned long)bp->b_addr & PAGE_MASK)) {
 313                         /* b_addr spans two pages - use alloc_page instead */
 314                         kmem_free(bp->b_addr);
 315                         bp->b_addr = NULL;
 316                         goto use_alloc_page;
 317                 }
 318                 bp->b_offset = offset_in_page(bp->b_addr);
 319                 bp->b_pages = bp->b_page_array;
 320                 bp->b_pages[0] = virt_to_page(bp->b_addr);
 321                 bp->b_page_count = 1;
 322                 bp->b_flags |= XBF_MAPPED | _XBF_KMEM;
 323                 return 0;
 324         }
 325
 326 use_alloc_page:
 327         end = bp->b_file_offset + bp->b_buffer_length;
 328         page_count = xfs_buf_btoc(end) - xfs_buf_btoct(bp->b_file_offset);
 329         error = _xfs_buf_get_pages(bp, page_count, flags);
 330         if (unlikely(error))
 331                 return error;
 332
 333         offset = bp->b_offset;
 334         bp->b_flags |= _XBF_PAGES;
 335
 336         for (i = 0; i < bp->b_page_count; i++) {
 337                 struct page     *page;
 338                 uint            retries = 0;
 339 retry:
 340                 page = alloc_page(gfp_mask);
 341                 if (unlikely(page == NULL)) {
 342                         if (flags & XBF_READ_AHEAD) {
 343                                 bp->b_page_count = i;
 344                                 error = ENOMEM;
 345                                 goto out_free_pages;
 346                         }
 347
 348                         /*
 349                          * This could deadlock.
 350                          *
 351                          * But until all the XFS lowlevel code is revamped to
 352                          * handle buffer allocation failures we can't do much.
 353                          */
 354                         if (!(++retries % 100))
 355                                 xfs_err(NULL,
 356                 "possible memory allocation deadlock in %s (mode:0x%x)",
 357                                         __func__, gfp_mask);
 358
 359                         XFS_STATS_INC(xb_page_retries);
 360                         congestion_wait(BLK_RW_ASYNC, HZ/50);
 361                         goto retry;
 362                 }
 363
 364                 XFS_STATS_INC(xb_page_found);
 365
 366                 nbytes = min_t(size_t, size, PAGE_SIZE - offset);
 367                 size -= nbytes;
 368                 bp->b_pages[i] = page;
 369                 offset = 0;
 370         }
 371         return 0;
 372
 373 out_free_pages:
 374         for (i = 0; i < bp->b_page_count; i++)
 375                 __free_page(bp->b_pages[i]);
 376         return error;
 377 }
 378
 379 /*
 380  *      Map buffer into kernel address-space if necessary.
 381  */
 382 STATIC int
 383 _xfs_buf_map_pages(
 384         xfs_buf_t               *bp,
 385         uint                    flags)
 386 {
 387         ASSERT(bp->b_flags & _XBF_PAGES);
 388         if (bp->b_page_count == 1) {
 389                 /* A single page buffer is always mappable */
 390                 bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
 391                 bp->b_flags |= XBF_MAPPED;
 392         } else if (flags & XBF_MAPPED) {
 393                 int retried = 0;
 394
 395                 do {
 396                         bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
 397                                                 -1, PAGE_KERNEL);
 398                         if (bp->b_addr)
 399                                 break;
 400                         vm_unmap_aliases();
 401                 } while (retried++ <= 1);
 402
 403                 if (!bp->b_addr)
 404                         return -ENOMEM;
 405                 bp->b_addr += bp->b_offset;
 406                 bp->b_flags |= XBF_MAPPED;
 407         }
 408
 409         return 0;
 410 }
 411
 412 /*
 413  *      Finding and Reading Buffers
 414  */
 415
 416 /*
 417  *      Look up, and creates if absent, a lockable buffer for
 418  *      a given range of an inode.  The buffer is returned
 419  *      locked. No I/O is implied by this call.
 420  */
 421 xfs_buf_t *
 422 _xfs_buf_find(
 423         xfs_buftarg_t           *btp,   /* block device target          */
 424         xfs_off_t               ioff,   /* starting offset of range     */
 425         size_t                  isize,  /* length of range              */
 426         xfs_buf_flags_t         flags,
 427         xfs_buf_t               *new_bp)
 428 {
 429         xfs_off_t               range_base;
 430         size_t                  range_length;
 431         struct xfs_perag        *pag;
 432         struct rb_node          **rbp;
 433         struct rb_node          *parent;
 434         xfs_buf_t               *bp;
 435
 436         range_base = (ioff << BBSHIFT);
 437         range_length = (isize << BBSHIFT);
 438
 439         /* Check for IOs smaller than the sector size / not sector aligned */
 440         ASSERT(!(range_length < (1 << btp->bt_sshift)));
 441         ASSERT(!(range_base & (xfs_off_t)btp->bt_smask));
 442
 443         /* get tree root */
 444         pag = xfs_perag_get(btp->bt_mount,
 445                                 xfs_daddr_to_agno(btp->bt_mount, ioff));
 446
 447         /* walk tree */
 448         spin_lock(&pag->pag_buf_lock);
 449         rbp = &pag->pag_buf_tree.rb_node;
 450         parent = NULL;
 451         bp = NULL;
 452         while (*rbp) {
 453                 parent = *rbp;
 454                 bp = rb_entry(parent, struct xfs_buf, b_rbnode);
 455
 456                 if (range_base < bp->b_file_offset)
 457                         rbp = &(*rbp)->rb_left;
 458                 else if (range_base > bp->b_file_offset)
 459                         rbp = &(*rbp)->rb_right;
 460                 else {
 461                         /*
 462                          * found a block offset match. If the range doesn't
 463                          * match, the only way this is allowed is if the buffer
 464                          * in the cache is stale and the transaction that made
 465                          * it stale has not yet committed. i.e. we are
 466                          * reallocating a busy extent. Skip this buffer and
 467                          * continue searching to the right for an exact match.
 468                          */
 469                         if (bp->b_buffer_length != range_length) {
 470                                 ASSERT(bp->b_flags & XBF_STALE);
 471                                 rbp = &(*rbp)->rb_right;
 472                                 continue;
 473                         }
 474                         atomic_inc(&bp->b_hold);
 475                         goto found;
 476                 }
 477         }
 478
 479         /* No match found */
 480         if (new_bp) {
 481                 rb_link_node(&new_bp->b_rbnode, parent, rbp);
 482                 rb_insert_color(&new_bp->b_rbnode, &pag->pag_buf_tree);
 483                 /* the buffer keeps the perag reference until it is freed */
 484                 new_bp->b_pag = pag;
 485                 spin_unlock(&pag->pag_buf_lock);
 486         } else {
 487                 XFS_STATS_INC(xb_miss_locked);
 488                 spin_unlock(&pag->pag_buf_lock);
 489                 xfs_perag_put(pag);
 490         }
 491         return new_bp;
 492
 493 found:
 494         spin_unlock(&pag->pag_buf_lock);
 495         xfs_perag_put(pag);
 496
 497         if (!xfs_buf_trylock(bp)) {
 498                 if (flags & XBF_TRYLOCK) {
 499                         xfs_buf_rele(bp);
 500                         XFS_STATS_INC(xb_busy_locked);
 501                         return NULL;
 502                 }
 503                 xfs_buf_lock(bp);
 504                 XFS_STATS_INC(xb_get_locked_waited);
 505         }
 506
 507         /*
 508          * if the buffer is stale, clear all the external state associated with
 509          * it. We need to keep flags such as how we allocated the buffer memory
 510          * intact here.
 511          */
 512         if (bp->b_flags & XBF_STALE) {
 513                 ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
 514                 bp->b_flags &= XBF_MAPPED | _XBF_KMEM | _XBF_PAGES;
 515         }
 516
 517         trace_xfs_buf_find(bp, flags, _RET_IP_);
 518         XFS_STATS_INC(xb_get_locked);
 519         return bp;
 520 }
 521
 522 /*
 523  * Assembles a buffer covering the specified range. The code is optimised for
 524  * cache hits, as metadata intensive workloads will see 3 orders of magnitude
 525  * more hits than misses.
 526  */
 527 struct xfs_buf *
 528 xfs_buf_get(
 529         xfs_buftarg_t           *target,/* target for buffer            */
 530         xfs_off_t               ioff,   /* starting offset of range     */
 531         size_t                  isize,  /* length of range              */
 532         xfs_buf_flags_t         flags)
 533 {
 534         struct xfs_buf          *bp;
 535         struct xfs_buf          *new_bp;
 536         int                     error = 0;
 537
 538         bp = _xfs_buf_find(target, ioff, isize, flags, NULL);
 539         if (likely(bp))
 540                 goto found;
 541
 542         new_bp = xfs_buf_allocate(flags);
 543         if (unlikely(!new_bp))
 544                 return NULL;
 545
 546         _xfs_buf_initialize(new_bp, target,
 547                             ioff << BBSHIFT, isize << BBSHIFT, flags);
 548
 549         bp = _xfs_buf_find(target, ioff, isize, flags, new_bp);
 550         if (!bp) {
 551                 xfs_buf_deallocate(new_bp);
 552                 return NULL;
 553         }
 554
 555         if (bp == new_bp) {
 556                 error = xfs_buf_allocate_memory(bp, flags);
 557                 if (error)
 558                         goto no_buffer;
 559         } else
 560                 xfs_buf_deallocate(new_bp);
 561
 562         /*
 563          * Now we have a workable buffer, fill in the block number so
 564          * that we can do IO on it.
 565          */
 566         bp->b_bn = ioff;
 567         bp->b_count_desired = bp->b_buffer_length;
 568
 569 found:
 570         if (!(bp->b_flags & XBF_MAPPED)) {
 571                 error = _xfs_buf_map_pages(bp, flags);
 572                 if (unlikely(error)) {
 573                         xfs_warn(target->bt_mount,
 574                                 "%s: failed to map pages\n", __func__);
 575                         goto no_buffer;
 576                 }
 577         }
 578
 579         XFS_STATS_INC(xb_get);
 580         trace_xfs_buf_get(bp, flags, _RET_IP_);
 581         return bp;
 582
 583 no_buffer:
 584         if (flags & (XBF_LOCK | XBF_TRYLOCK))
 585                 xfs_buf_unlock(bp);
 586         xfs_buf_rele(bp);
 587         return NULL;
 588 }
 589
 590 STATIC int
 591 _xfs_buf_read(
 592         xfs_buf_t               *bp,
 593         xfs_buf_flags_t         flags)
 594 {
 595         int                     status;
 596
 597         ASSERT(!(flags & (XBF_DELWRI|XBF_WRITE)));
 598         ASSERT(bp->b_bn != XFS_BUF_DADDR_NULL);
 599
 600         bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_DELWRI | XBF_READ_AHEAD);
 601         bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
 602
 603         status = xfs_buf_iorequest(bp);
 604         if (status || bp->b_error || (flags & XBF_ASYNC))
 605                 return status;
 606         return xfs_buf_iowait(bp);
 607 }
 608
 609 xfs_buf_t *
 610 xfs_buf_read(
 611         xfs_buftarg_t           *target,
 612         xfs_off_t               ioff,
 613         size_t                  isize,
 614         xfs_buf_flags_t         flags)
 615 {
 616         xfs_buf_t               *bp;
 617
 618         flags |= XBF_READ;
 619
 620         bp = xfs_buf_get(target, ioff, isize, flags);
 621         if (bp) {
 622                 trace_xfs_buf_read(bp, flags, _RET_IP_);
 623
 624                 if (!XFS_BUF_ISDONE(bp)) {
 625                         XFS_STATS_INC(xb_get_read);
 626                         _xfs_buf_read(bp, flags);
 627                 } else if (flags & XBF_ASYNC) {
 628                         /*
 629                          * Read ahead call which is already satisfied,
 630                          * drop the buffer
 631                          */
 632                         goto no_buffer;
 633                 } else {
 634                         /* We do not want read in the flags */
 635                         bp->b_flags &= ~XBF_READ;
 636                 }
 637         }
 638
 639         return bp;
 640
 641  no_buffer:
 642         if (flags & (XBF_LOCK | XBF_TRYLOCK))
 643                 xfs_buf_unlock(bp);
 644         xfs_buf_rele(bp);
 645         return NULL;
 646 }
 647
 648 /*
 649  *      If we are not low on memory then do the readahead in a deadlock
 650  *      safe manner.
 651  */
 652 void
 653 xfs_buf_readahead(
 654         xfs_buftarg_t           *target,
 655         xfs_off_t               ioff,
 656         size_t                  isize)
 657 {
 658         if (bdi_read_congested(target->bt_bdi))
 659                 return;
 660
 661         xfs_buf_read(target, ioff, isize,
 662                      XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD|XBF_DONT_BLOCK);
 663 }
 664
 665 /*
 666  * Read an uncached buffer from disk. Allocates and returns a locked
 667  * buffer containing the disk contents or nothing.
 668  */
 669 struct xfs_buf *
 670 xfs_buf_read_uncached(
 671         struct xfs_mount        *mp,
 672         struct xfs_buftarg      *target,
 673         xfs_daddr_t             daddr,
 674         size_t                  length,
 675         int                     flags)
 676 {
 677         xfs_buf_t               *bp;
 678         int                     error;
 679
 680         bp = xfs_buf_get_uncached(target, length, flags);
 681         if (!bp)
 682                 return NULL;
 683
 684         /* set up the buffer for a read IO */
 685         XFS_BUF_SET_ADDR(bp, daddr);
 686         XFS_BUF_READ(bp);
 687
 688         xfsbdstrat(mp, bp);
 689         error = xfs_buf_iowait(bp);
 690         if (error || bp->b_error) {
 691                 xfs_buf_relse(bp);
 692                 return NULL;
 693         }
 694         return bp;
 695 }
 696
 697 xfs_buf_t *
 698 xfs_buf_get_empty(
 699         size_t                  len,
 700         xfs_buftarg_t           *target)
 701 {
 702         xfs_buf_t               *bp;
 703
 704         bp = xfs_buf_allocate(0);
 705         if (bp)
 706                 _xfs_buf_initialize(bp, target, 0, len, 0);
 707         return bp;
 708 }
 709
 710 /*
 711  * Return a buffer allocated as an empty buffer and associated to external
 712  * memory via xfs_buf_associate_memory() back to it's empty state.
 713  */
 714 void
 715 xfs_buf_set_empty(
 716         struct xfs_buf          *bp,
 717         size_t                  len)
 718 {
 719         if (bp->b_pages)
 720                 _xfs_buf_free_pages(bp);
 721
 722         bp->b_pages = NULL;
 723         bp->b_page_count = 0;
 724         bp->b_addr = NULL;
 725         bp->b_file_offset = 0;
 726         bp->b_buffer_length = bp->b_count_desired = len;
 727         bp->b_bn = XFS_BUF_DADDR_NULL;
 728         bp->b_flags &= ~XBF_MAPPED;
 729 }
 730
 731 static inline struct page *
 732 mem_to_page(
 733         void                    *addr)
 734 {
 735         if ((!is_vmalloc_addr(addr))) {
 736                 return virt_to_page(addr);
 737         } else {
 738                 return vmalloc_to_page(addr);
 739         }
 740 }
 741
 742 int
 743 xfs_buf_associate_memory(
 744         xfs_buf_t               *bp,
 745         void                    *mem,
 746         size_t                  len)
 747 {
 748         int                     rval;
 749         int                     i = 0;
 750         unsigned long           pageaddr;
 751         unsigned long           offset;
 752         size_t                  buflen;
 753         int                     page_count;
 754
 755         pageaddr = (unsigned long)mem & PAGE_MASK;
 756         offset = (unsigned long)mem - pageaddr;
 757         buflen = PAGE_ALIGN(len + offset);
 758         page_count = buflen >> PAGE_SHIFT;
 759
 760         /* Free any previous set of page pointers */
 761         if (bp->b_pages)
 762                 _xfs_buf_free_pages(bp);
 763
 764         bp->b_pages = NULL;
 765         bp->b_addr = mem;
 766
 767         rval = _xfs_buf_get_pages(bp, page_count, XBF_DONT_BLOCK);
 768         if (rval)
 769                 return rval;
 770
 771         bp->b_offset = offset;
 772
 773         for (i = 0; i < bp->b_page_count; i++) {
 774                 bp->b_pages[i] = mem_to_page((void *)pageaddr);
 775                 pageaddr += PAGE_SIZE;
 776         }
 777
 778         bp->b_count_desired = len;
 779         bp->b_buffer_length = buflen;
 780         bp->b_flags |= XBF_MAPPED;
 781
 782         return 0;
 783 }
 784
 785 xfs_buf_t *
 786 xfs_buf_get_uncached(
 787         struct xfs_buftarg      *target,
 788         size_t                  len,
 789         int                     flags)
 790 {
 791         unsigned long           page_count = PAGE_ALIGN(len) >> PAGE_SHIFT;
 792         int                     error, i;
 793         xfs_buf_t               *bp;
 794
 795         bp = xfs_buf_allocate(0);
 796         if (unlikely(bp == NULL))
 797                 goto fail;
 798         _xfs_buf_initialize(bp, target, 0, len, 0);
 799
 800         error = _xfs_buf_get_pages(bp, page_count, 0);
 801         if (error)
 802                 goto fail_free_buf;
 803
 804         for (i = 0; i < page_count; i++) {
 805                 bp->b_pages[i] = alloc_page(xb_to_gfp(flags));
 806                 if (!bp->b_pages[i])
 807                         goto fail_free_mem;
 808         }
 809         bp->b_flags |= _XBF_PAGES;
 810
 811         error = _xfs_buf_map_pages(bp, XBF_MAPPED);
 812         if (unlikely(error)) {
 813                 xfs_warn(target->bt_mount,
 814                         "%s: failed to map pages\n", __func__);
 815                 goto fail_free_mem;
 816         }
 817
 818         trace_xfs_buf_get_uncached(bp, _RET_IP_);
 819         return bp;
 820
 821  fail_free_mem:
 822         while (--i >= 0)
 823                 __free_page(bp->b_pages[i]);
 824         _xfs_buf_free_pages(bp);
 825  fail_free_buf:
 826         xfs_buf_deallocate(bp);
 827  fail:
 828         return NULL;
 829 }
 830
 831 /*
 832  *      Increment reference count on buffer, to hold the buffer concurrently
 833  *      with another thread which may release (free) the buffer asynchronously.
 834  *      Must hold the buffer already to call this function.
 835  */
 836 void
 837 xfs_buf_hold(
 838         xfs_buf_t               *bp)
 839 {
 840         trace_xfs_buf_hold(bp, _RET_IP_);
 841         atomic_inc(&bp->b_hold);
 842 }
 843
 844 /*
 845  *      Releases a hold on the specified buffer.  If the
 846  *      the hold count is 1, calls xfs_buf_free.
 847  */
 848 void
 849 xfs_buf_rele(
 850         xfs_buf_t               *bp)
 851 {
 852         struct xfs_perag        *pag = bp->b_pag;
 853
 854         trace_xfs_buf_rele(bp, _RET_IP_);
 855
 856         if (!pag) {
 857                 ASSERT(list_empty(&bp->b_lru));
 858                 ASSERT(RB_EMPTY_NODE(&bp->b_rbnode));
 859                 if (atomic_dec_and_test(&bp->b_hold))
 860                         xfs_buf_free(bp);
 861                 return;
 862         }
 863
 864         ASSERT(!RB_EMPTY_NODE(&bp->b_rbnode));
 865
 866         ASSERT(atomic_read(&bp->b_hold) > 0);
 867         if (atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock)) {
 868                 if (!(bp->b_flags & XBF_STALE) &&
 869                            atomic_read(&bp->b_lru_ref)) {
 870                         xfs_buf_lru_add(bp);
 871                         spin_unlock(&pag->pag_buf_lock);
 872                 } else {
 873                         xfs_buf_lru_del(bp);
 874                         ASSERT(!(bp->b_flags & (XBF_DELWRI|_XBF_DELWRI_Q)));
 875                         rb_erase(&bp->b_rbnode, &pag->pag_buf_tree);
 876                         spin_unlock(&pag->pag_buf_lock);
 877                         xfs_perag_put(pag);
 878                         xfs_buf_free(bp);
 879                 }
 880         }
 881 }
 882
 883
 884 /*
 885  *      Lock a buffer object, if it is not already locked.
 886  *
 887  *      If we come across a stale, pinned, locked buffer, we know that we are
 888  *      being asked to lock a buffer that has been reallocated. Because it is
 889  *      pinned, we know that the log has not been pushed to disk and hence it
 890  *      will still be locked.  Rather than continuing to have trylock attempts
 891  *      fail until someone else pushes the log, push it ourselves before
 892  *      returning.  This means that the xfsaild will not get stuck trying
 893  *      to push on stale inode buffers.
 894  */
 895 int
 896 xfs_buf_trylock(
 897         struct xfs_buf          *bp)
 898 {
 899         int                     locked;
 900
 901         locked = down_trylock(&bp->b_sema) == 0;
 902         if (locked)
 903                 XB_SET_OWNER(bp);
 904         else if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
 905                 xfs_log_force(bp->b_target->bt_mount, 0);
 906
 907         trace_xfs_buf_trylock(bp, _RET_IP_);
 908         return locked;
 909 }
 910
 911 /*
 912  *      Lock a buffer object.
 913  *
 914  *      If we come across a stale, pinned, locked buffer, we know that we
 915  *      are being asked to lock a buffer that has been reallocated. Because
 916  *      it is pinned, we know that the log has not been pushed to disk and
 917  *      hence it will still be locked. Rather than sleeping until someone
 918  *      else pushes the log, push it ourselves before trying to get the lock.
 919  */
 920 void
 921 xfs_buf_lock(
 922         struct xfs_buf          *bp)
 923 {
 924         trace_xfs_buf_lock(bp, _RET_IP_);
 925
 926         if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
 927                 xfs_log_force(bp->b_target->bt_mount, 0);
 928         down(&bp->b_sema);
 929         XB_SET_OWNER(bp);
 930
 931         trace_xfs_buf_lock_done(bp, _RET_IP_);
 932 }
 933
 934 /*
 935  *      Releases the lock on the buffer object.
 936  *      If the buffer is marked delwri but is not queued, do so before we
 937  *      unlock the buffer as we need to set flags correctly.  We also need to
 938  *      take a reference for the delwri queue because the unlocker is going to
 939  *      drop their's and they don't know we just queued it.
 940  */
 941 void
 942 xfs_buf_unlock(
 943         struct xfs_buf          *bp)
 944 {
 945         XB_CLEAR_OWNER(bp);
 946         up(&bp->b_sema);
 947
 948         trace_xfs_buf_unlock(bp, _RET_IP_);
 949 }
 950
 951 STATIC void
 952 xfs_buf_wait_unpin(
 953         xfs_buf_t               *bp)
 954 {
 955         DECLARE_WAITQUEUE       (wait, current);
 956
 957         if (atomic_read(&bp->b_pin_count) == 0)
 958                 return;
 959
 960         add_wait_queue(&bp->b_waiters, &wait);
 961         for (;;) {
 962                 set_current_state(TASK_UNINTERRUPTIBLE);
 963                 if (atomic_read(&bp->b_pin_count) == 0)
 964                         break;
 965                 io_schedule();
 966         }
 967         remove_wait_queue(&bp->b_waiters, &wait);
 968         set_current_state(TASK_RUNNING);
 969 }
 970
 971 /*
 972  *      Buffer Utility Routines
 973  */
 974
 975 STATIC void
 976 xfs_buf_iodone_work(
 977         struct work_struct      *work)
 978 {
 979         xfs_buf_t               *bp =
 980                 container_of(work, xfs_buf_t, b_iodone_work);
 981
 982         if (bp->b_iodone)
 983                 (*(bp->b_iodone))(bp);
 984         else if (bp->b_flags & XBF_ASYNC)
 985                 xfs_buf_relse(bp);
 986 }
 987
 988 void
 989 xfs_buf_ioend(
 990         xfs_buf_t               *bp,
 991         int                     schedule)
 992 {
 993         trace_xfs_buf_iodone(bp, _RET_IP_);
 994
 995         bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
 996         if (bp->b_error == 0)
 997                 bp->b_flags |= XBF_DONE;
 998
 999         if ((bp->b_iodone) || (bp->b_flags & XBF_ASYNC)) {
1000                 if (schedule) {
1001                         INIT_WORK(&bp->b_iodone_work, xfs_buf_iodone_work);
1002                         queue_work(xfslogd_workqueue, &bp->b_iodone_work);
1003                 } else {
1004                         xfs_buf_iodone_work(&bp->b_iodone_work);
1005                 }
1006         } else {
1007                 complete(&bp->b_iowait);
1008         }
1009 }
1010
1011 void
1012 xfs_buf_ioerror(
1013         xfs_buf_t               *bp,
1014         int                     error)
1015 {
1016         ASSERT(error >= 0 && error <= 0xffff);
1017         bp->b_error = (unsigned short)error;
1018         trace_xfs_buf_ioerror(bp, error, _RET_IP_);
1019 }
1020
1021 int
1022 xfs_bwrite(
1023         struct xfs_buf          *bp)
1024 {
1025         int                     error;
1026
1027         bp->b_flags |= XBF_WRITE;
1028         bp->b_flags &= ~(XBF_ASYNC | XBF_READ);
1029
1030         xfs_buf_delwri_dequeue(bp);
1031         xfs_bdstrat_cb(bp);
1032
1033         error = xfs_buf_iowait(bp);
1034         if (error) {
1035                 xfs_force_shutdown(bp->b_target->bt_mount,
1036                                    SHUTDOWN_META_IO_ERROR);
1037         }
1038         return error;
1039 }
1040
1041 /*
1042  * Called when we want to stop a buffer from getting written or read.
1043  * We attach the EIO error, muck with its flags, and call xfs_buf_ioend
1044  * so that the proper iodone callbacks get called.
1045  */
1046 STATIC int
1047 xfs_bioerror(
1048         xfs_buf_t *bp)
1049 {
1050 #ifdef XFSERRORDEBUG
1051         ASSERT(XFS_BUF_ISREAD(bp) || bp->b_iodone);
1052 #endif
1053
1054         /*
1055          * No need to wait until the buffer is unpinned, we aren't flushing it.
1056          */
1057         xfs_buf_ioerror(bp, EIO);
1058
1059         /*
1060          * We're calling xfs_buf_ioend, so delete XBF_DONE flag.
1061          */
1062         XFS_BUF_UNREAD(bp);
1063         XFS_BUF_UNDONE(bp);
1064         xfs_buf_stale(bp);
1065
1066         xfs_buf_ioend(bp, 0);
1067
1068         return EIO;
1069 }
1070
1071 /*
1072  * Same as xfs_bioerror, except that we are releasing the buffer
1073  * here ourselves, and avoiding the xfs_buf_ioend call.
1074  * This is meant for userdata errors; metadata bufs come with
1075  * iodone functions attached, so that we can track down errors.
1076  */
1077 STATIC int
1078 xfs_bioerror_relse(
1079         struct xfs_buf  *bp)
1080 {
1081         int64_t         fl = bp->b_flags;
1082         /*
1083          * No need to wait until the buffer is unpinned.
1084          * We aren't flushing it.
1085          *
1086          * chunkhold expects B_DONE to be set, whether
1087          * we actually finish the I/O or not. We don't want to
1088          * change that interface.
1089          */
1090         XFS_BUF_UNREAD(bp);
1091         XFS_BUF_DONE(bp);
1092         xfs_buf_stale(bp);
1093         bp->b_iodone = NULL;
1094         if (!(fl & XBF_ASYNC)) {
1095                 /*
1096                  * Mark b_error and B_ERROR _both_.
1097                  * Lot's of chunkcache code assumes that.
1098                  * There's no reason to mark error for
1099                  * ASYNC buffers.
1100                  */
1101                 xfs_buf_ioerror(bp, EIO);
1102                 complete(&bp->b_iowait);
1103         } else {
1104                 xfs_buf_relse(bp);
1105         }
1106
1107         return EIO;
1108 }
1109
1110
1111 /*
1112  * All xfs metadata buffers except log state machine buffers
1113  * get this attached as their b_bdstrat callback function.
1114  * This is so that we can catch a buffer
1115  * after prematurely unpinning it to forcibly shutdown the filesystem.
1116  */
1117 int
1118 xfs_bdstrat_cb(
1119         struct xfs_buf  *bp)
1120 {
1121         if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
1122                 trace_xfs_bdstrat_shut(bp, _RET_IP_);
1123                 /*
1124                  * Metadata write that didn't get logged but
1125                  * written delayed anyway. These aren't associated
1126                  * with a transaction, and can be ignored.
1127                  */
1128                 if (!bp->b_iodone && !XFS_BUF_ISREAD(bp))
1129                         return xfs_bioerror_relse(bp);
1130                 else
1131                         return xfs_bioerror(bp);
1132         }
1133
1134         xfs_buf_iorequest(bp);
1135         return 0;
1136 }
1137
1138 /*
1139  * Wrapper around bdstrat so that we can stop data from going to disk in case
1140  * we are shutting down the filesystem.  Typically user data goes thru this
1141  * path; one of the exceptions is the superblock.
1142  */
1143 void
1144 xfsbdstrat(
1145         struct xfs_mount        *mp,
1146         struct xfs_buf          *bp)
1147 {
1148         if (XFS_FORCED_SHUTDOWN(mp)) {
1149                 trace_xfs_bdstrat_shut(bp, _RET_IP_);
1150                 xfs_bioerror_relse(bp);
1151                 return;
1152         }
1153
1154         xfs_buf_iorequest(bp);
1155 }
1156
1157 STATIC void
1158 _xfs_buf_ioend(
1159         xfs_buf_t               *bp,
1160         int                     schedule)
1161 {
1162         if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
1163                 xfs_buf_ioend(bp, schedule);
1164 }
1165
1166 STATIC void
1167 xfs_buf_bio_end_io(
1168         struct bio              *bio,
1169         int                     error)
1170 {
1171         xfs_buf_t               *bp = (xfs_buf_t *)bio->bi_private;
1172
1173         xfs_buf_ioerror(bp, -error);
1174
1175         if (!error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
1176                 invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
1177
1178         _xfs_buf_ioend(bp, 1);
1179         bio_put(bio);
1180 }
1181
1182 STATIC void
1183 _xfs_buf_ioapply(
1184         xfs_buf_t               *bp)
1185 {
1186         int                     rw, map_i, total_nr_pages, nr_pages;
1187         struct bio              *bio;
1188         int                     offset = bp->b_offset;
1189         int                     size = bp->b_count_desired;
1190         sector_t                sector = bp->b_bn;
1191
1192         total_nr_pages = bp->b_page_count;
1193         map_i = 0;
1194
1195         if (bp->b_flags & XBF_WRITE) {
1196                 if (bp->b_flags & XBF_SYNCIO)
1197                         rw = WRITE_SYNC;
1198                 else
1199                         rw = WRITE;
1200                 if (bp->b_flags & XBF_FUA)
1201                         rw |= REQ_FUA;
1202                 if (bp->b_flags & XBF_FLUSH)
1203                         rw |= REQ_FLUSH;
1204         } else if (bp->b_flags & XBF_READ_AHEAD) {
1205                 rw = READA;
1206         } else {
1207                 rw = READ;
1208         }
1209
1210         /* we only use the buffer cache for meta-data */
1211         rw |= REQ_META;
1212
1213 next_chunk:
1214         atomic_inc(&bp->b_io_remaining);
1215         nr_pages = BIO_MAX_SECTORS >> (PAGE_SHIFT - BBSHIFT);
1216         if (nr_pages > total_nr_pages)
1217                 nr_pages = total_nr_pages;
1218
1219         bio = bio_alloc(GFP_NOIO, nr_pages);
1220         bio->bi_bdev = bp->b_target->bt_bdev;
1221         bio->bi_sector = sector;
1222         bio->bi_end_io = xfs_buf_bio_end_io;
1223         bio->bi_private = bp;
1224
1225
1226         for (; size && nr_pages; nr_pages--, map_i++) {
1227                 int     rbytes, nbytes = PAGE_SIZE - offset;
1228
1229                 if (nbytes > size)
1230                         nbytes = size;
1231
1232                 rbytes = bio_add_page(bio, bp->b_pages[map_i], nbytes, offset);
1233                 if (rbytes < nbytes)
1234                         break;
1235
1236                 offset = 0;
1237                 sector += nbytes >> BBSHIFT;
1238                 size -= nbytes;
1239                 total_nr_pages--;
1240         }
1241
1242         if (likely(bio->bi_size)) {
1243                 if (xfs_buf_is_vmapped(bp)) {
1244                         flush_kernel_vmap_range(bp->b_addr,
1245                                                 xfs_buf_vmap_len(bp));
1246                 }
1247                 submit_bio(rw, bio);
1248                 if (size)
1249                         goto next_chunk;
1250         } else {
1251                 xfs_buf_ioerror(bp, EIO);
1252                 bio_put(bio);
1253         }
1254 }
1255
1256 int
1257 xfs_buf_iorequest(
1258         xfs_buf_t               *bp)
1259 {
1260         trace_xfs_buf_iorequest(bp, _RET_IP_);
1261
1262         ASSERT(!(bp->b_flags & XBF_DELWRI));
1263
1264         if (bp->b_flags & XBF_WRITE)
1265                 xfs_buf_wait_unpin(bp);
1266         xfs_buf_hold(bp);
1267
1268         /* Set the count to 1 initially, this will stop an I/O
1269          * completion callout which happens before we have started
1270          * all the I/O from calling xfs_buf_ioend too early.
1271          */
1272         atomic_set(&bp->b_io_remaining, 1);
1273         _xfs_buf_ioapply(bp);
1274         _xfs_buf_ioend(bp, 0);
1275
1276         xfs_buf_rele(bp);
1277         return 0;
1278 }
1279
1280 /*
1281  *      Waits for I/O to complete on the buffer supplied.
1282  *      It returns immediately if no I/O is pending.
1283  *      It returns the I/O error code, if any, or 0 if there was no error.
1284  */
1285 int
1286 xfs_buf_iowait(
1287         xfs_buf_t               *bp)
1288 {
1289         trace_xfs_buf_iowait(bp, _RET_IP_);
1290
1291         wait_for_completion(&bp->b_iowait);
1292
1293         trace_xfs_buf_iowait_done(bp, _RET_IP_);
1294         return bp->b_error;
1295 }
1296
1297 xfs_caddr_t
1298 xfs_buf_offset(
1299         xfs_buf_t               *bp,
1300         size_t                  offset)
1301 {
1302         struct page             *page;
1303
1304         if (bp->b_flags & XBF_MAPPED)
1305                 return bp->b_addr + offset;
1306
1307         offset += bp->b_offset;
1308         page = bp->b_pages[offset >> PAGE_SHIFT];
1309         return (xfs_caddr_t)page_address(page) + (offset & (PAGE_SIZE-1));
1310 }
1311
1312 /*
1313  *      Move data into or out of a buffer.
1314  */
1315 void
1316 xfs_buf_iomove(
1317         xfs_buf_t               *bp,    /* buffer to process            */
1318         size_t                  boff,   /* starting buffer offset       */
1319         size_t                  bsize,  /* length to copy               */
1320         void                    *data,  /* data address                 */
1321         xfs_buf_rw_t            mode)   /* read/write/zero flag         */
1322 {
1323         size_t                  bend, cpoff, csize;
1324         struct page             *page;
1325
1326         bend = boff + bsize;
1327         while (boff < bend) {
1328                 page = bp->b_pages[xfs_buf_btoct(boff + bp->b_offset)];
1329                 cpoff = xfs_buf_poff(boff + bp->b_offset);
1330                 csize = min_t(size_t,
1331                               PAGE_SIZE-cpoff, bp->b_count_desired-boff);
1332
1333                 ASSERT(((csize + cpoff) <= PAGE_SIZE));
1334
1335                 switch (mode) {
1336                 case XBRW_ZERO:
1337                         memset(page_address(page) + cpoff, 0, csize);
1338                         break;
1339                 case XBRW_READ:
1340                         memcpy(data, page_address(page) + cpoff, csize);
1341                         break;
1342                 case XBRW_WRITE:
1343                         memcpy(page_address(page) + cpoff, data, csize);
1344                 }
1345
1346                 boff += csize;
1347                 data += csize;
1348         }
1349 }
1350
1351 /*
1352  *      Handling of buffer targets (buftargs).
1353  */
1354
1355 /*
1356  * Wait for any bufs with callbacks that have been submitted but have not yet
1357  * returned. These buffers will have an elevated hold count, so wait on those
1358  * while freeing all the buffers only held by the LRU.
1359  */
1360 void
1361 xfs_wait_buftarg(
1362         struct xfs_buftarg      *btp)
1363 {
1364         struct xfs_buf          *bp;
1365
1366 restart:
1367         spin_lock(&btp->bt_lru_lock);
1368         while (!list_empty(&btp->bt_lru)) {
1369                 bp = list_first_entry(&btp->bt_lru, struct xfs_buf, b_lru);
1370                 if (atomic_read(&bp->b_hold) > 1) {
1371                         spin_unlock(&btp->bt_lru_lock);
1372                         delay(100);
1373                         goto restart;
1374                 }
1375                 /*
1376                  * clear the LRU reference count so the bufer doesn't get
1377                  * ignored in xfs_buf_rele().
1378                  */
1379                 atomic_set(&bp->b_lru_ref, 0);
1380                 spin_unlock(&btp->bt_lru_lock);
1381                 xfs_buf_rele(bp);
1382                 spin_lock(&btp->bt_lru_lock);
1383         }
1384         spin_unlock(&btp->bt_lru_lock);
1385 }
1386
1387 int
1388 xfs_buftarg_shrink(
1389         struct shrinker         *shrink,
1390         struct shrink_control   *sc)
1391 {
1392         struct xfs_buftarg      *btp = container_of(shrink,
1393                                         struct xfs_buftarg, bt_shrinker);
1394         struct xfs_buf          *bp;
1395         int nr_to_scan = sc->nr_to_scan;
1396         LIST_HEAD(dispose);
1397
1398         if (!nr_to_scan)
1399                 return btp->bt_lru_nr;
1400
1401         spin_lock(&btp->bt_lru_lock);
1402         while (!list_empty(&btp->bt_lru)) {
1403                 if (nr_to_scan-- <= 0)
1404                         break;
1405
1406                 bp = list_first_entry(&btp->bt_lru, struct xfs_buf, b_lru);
1407
1408                 /*
1409                  * Decrement the b_lru_ref count unless the value is already
1410                  * zero. If the value is already zero, we need to reclaim the
1411                  * buffer, otherwise it gets another trip through the LRU.
1412                  */
1413                 if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
1414                         list_move_tail(&bp->b_lru, &btp->bt_lru);
1415                         continue;
1416                 }
1417
1418                 /*
1419                  * remove the buffer from the LRU now to avoid needing another
1420                  * lock round trip inside xfs_buf_rele().
1421                  */
1422                 list_move(&bp->b_lru, &dispose);
1423                 btp->bt_lru_nr--;
1424         }
1425         spin_unlock(&btp->bt_lru_lock);
1426
1427         while (!list_empty(&dispose)) {
1428                 bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1429                 list_del_init(&bp->b_lru);
1430                 xfs_buf_rele(bp);
1431         }
1432
1433         return btp->bt_lru_nr;
1434 }
1435
1436 void
1437 xfs_free_buftarg(
1438         struct xfs_mount        *mp,
1439         struct xfs_buftarg      *btp)
1440 {
1441         unregister_shrinker(&btp->bt_shrinker);
1442
1443         xfs_flush_buftarg(btp, 1);
1444         if (mp->m_flags & XFS_MOUNT_BARRIER)
1445                 xfs_blkdev_issue_flush(btp);
1446
1447         kthread_stop(btp->bt_task);
1448         kmem_free(btp);
1449 }
1450
1451 STATIC int
1452 xfs_setsize_buftarg_flags(
1453         xfs_buftarg_t           *btp,
1454         unsigned int            blocksize,
1455         unsigned int            sectorsize,
1456         int                     verbose)
1457 {
1458         btp->bt_bsize = blocksize;
1459         btp->bt_sshift = ffs(sectorsize) - 1;
1460         btp->bt_smask = sectorsize - 1;
1461
1462         if (set_blocksize(btp->bt_bdev, sectorsize)) {
1463                 xfs_warn(btp->bt_mount,
1464                         "Cannot set_blocksize to %u on device %s\n",
1465                         sectorsize, xfs_buf_target_name(btp));
1466                 return EINVAL;
1467         }
1468
1469         return 0;
1470 }
1471
1472 /*
1473  *      When allocating the initial buffer target we have not yet
1474  *      read in the superblock, so don't know what sized sectors
1475  *      are being used is at this early stage.  Play safe.
1476  */
1477 STATIC int
1478 xfs_setsize_buftarg_early(
1479         xfs_buftarg_t           *btp,
1480         struct block_device     *bdev)
1481 {
1482         return xfs_setsize_buftarg_flags(btp,
1483                         PAGE_SIZE, bdev_logical_block_size(bdev), 0);
1484 }
1485
1486 int
1487 xfs_setsize_buftarg(
1488         xfs_buftarg_t           *btp,
1489         unsigned int            blocksize,
1490         unsigned int            sectorsize)
1491 {
1492         return xfs_setsize_buftarg_flags(btp, blocksize, sectorsize, 1);
1493 }
1494
1495 STATIC int
1496 xfs_alloc_delwri_queue(
1497         xfs_buftarg_t           *btp,
1498         const char              *fsname)
1499 {
1500         INIT_LIST_HEAD(&btp->bt_delwri_queue);
1501         spin_lock_init(&btp->bt_delwri_lock);
1502         btp->bt_flags = 0;
1503         btp->bt_task = kthread_run(xfsbufd, btp, "xfsbufd/%s", fsname);
1504         if (IS_ERR(btp->bt_task))
1505                 return PTR_ERR(btp->bt_task);
1506         return 0;
1507 }
1508
1509 xfs_buftarg_t *
1510 xfs_alloc_buftarg(
1511         struct xfs_mount        *mp,
1512         struct block_device     *bdev,
1513         int                     external,
1514         const char              *fsname)
1515 {
1516         xfs_buftarg_t           *btp;
1517
1518         btp = kmem_zalloc(sizeof(*btp), KM_SLEEP);
1519
1520         btp->bt_mount = mp;
1521         btp->bt_dev =  bdev->bd_dev;
1522         btp->bt_bdev = bdev;
1523         btp->bt_bdi = blk_get_backing_dev_info(bdev);
1524         if (!btp->bt_bdi)
1525                 goto error;
1526
1527         INIT_LIST_HEAD(&btp->bt_lru);
1528         spin_lock_init(&btp->bt_lru_lock);
1529         if (xfs_setsize_buftarg_early(btp, bdev))
1530                 goto error;
1531         if (xfs_alloc_delwri_queue(btp, fsname))
1532                 goto error;
1533         btp->bt_shrinker.shrink = xfs_buftarg_shrink;
1534         btp->bt_shrinker.seeks = DEFAULT_SEEKS;
1535         register_shrinker(&btp->bt_shrinker);
1536         return btp;
1537
1538 error:
1539         kmem_free(btp);
1540         return NULL;
1541 }
1542
1543
1544 /*
1545  *      Delayed write buffer handling
1546  */
1547 void
1548 xfs_buf_delwri_queue(
1549         xfs_buf_t               *bp)
1550 {
1551         struct xfs_buftarg      *btp = bp->b_target;
1552
1553         trace_xfs_buf_delwri_queue(bp, _RET_IP_);
1554
1555         ASSERT(!(bp->b_flags & XBF_READ));
1556
1557         spin_lock(&btp->bt_delwri_lock);
1558         if (!list_empty(&bp->b_list)) {
1559                 /* if already in the queue, move it to the tail */
1560                 ASSERT(bp->b_flags & _XBF_DELWRI_Q);
1561                 list_move_tail(&bp->b_list, &btp->bt_delwri_queue);
1562         } else {
1563                 /* start xfsbufd as it is about to have something to do */
1564                 if (list_empty(&btp->bt_delwri_queue))
1565                         wake_up_process(bp->b_target->bt_task);
1566
1567                 atomic_inc(&bp->b_hold);
1568                 bp->b_flags |= XBF_DELWRI | _XBF_DELWRI_Q | XBF_ASYNC;
1569                 list_add_tail(&bp->b_list, &btp->bt_delwri_queue);
1570         }
1571         bp->b_queuetime = jiffies;
1572         spin_unlock(&btp->bt_delwri_lock);
1573 }
1574
1575 void
1576 xfs_buf_delwri_dequeue(
1577         xfs_buf_t               *bp)
1578 {
1579         int                     dequeued = 0;
1580
1581         spin_lock(&bp->b_target->bt_delwri_lock);
1582         if ((bp->b_flags & XBF_DELWRI) && !list_empty(&bp->b_list)) {
1583                 ASSERT(bp->b_flags & _XBF_DELWRI_Q);
1584                 list_del_init(&bp->b_list);
1585                 dequeued = 1;
1586         }
1587         bp->b_flags &= ~(XBF_DELWRI|_XBF_DELWRI_Q);
1588         spin_unlock(&bp->b_target->bt_delwri_lock);
1589
1590         if (dequeued)
1591                 xfs_buf_rele(bp);
1592
1593         trace_xfs_buf_delwri_dequeue(bp, _RET_IP_);
1594 }
1595
1596 /*
1597  * If a delwri buffer needs to be pushed before it has aged out, then promote
1598  * it to the head of the delwri queue so that it will be flushed on the next
1599  * xfsbufd run. We do this by resetting the queuetime of the buffer to be older
1600  * than the age currently needed to flush the buffer. Hence the next time the
1601  * xfsbufd sees it is guaranteed to be considered old enough to flush.
1602  */
1603 void
1604 xfs_buf_delwri_promote(
1605         struct xfs_buf  *bp)
1606 {
1607         struct xfs_buftarg *btp = bp->b_target;
1608         long            age = xfs_buf_age_centisecs * msecs_to_jiffies(10) + 1;
1609
1610         ASSERT(bp->b_flags & XBF_DELWRI);
1611         ASSERT(bp->b_flags & _XBF_DELWRI_Q);
1612
1613         /*
1614          * Check the buffer age before locking the delayed write queue as we
1615          * don't need to promote buffers that are already past the flush age.
1616          */
1617         if (bp->b_queuetime < jiffies - age)
1618                 return;
1619         bp->b_queuetime = jiffies - age;
1620         spin_lock(&btp->bt_delwri_lock);
1621         list_move(&bp->b_list, &btp->bt_delwri_queue);
1622         spin_unlock(&btp->bt_delwri_lock);
1623 }
1624
1625 STATIC void
1626 xfs_buf_runall_queues(
1627         struct workqueue_struct *queue)
1628 {
1629         flush_workqueue(queue);
1630 }
1631
1632 /*
1633  * Move as many buffers as specified to the supplied list
1634  * idicating if we skipped any buffers to prevent deadlocks.
1635  */
1636 STATIC int
1637 xfs_buf_delwri_split(
1638         xfs_buftarg_t   *target,
1639         struct list_head *list,
1640         unsigned long   age)
1641 {
1642         xfs_buf_t       *bp, *n;
1643         int             skipped = 0;
1644         int             force;
1645
1646         force = test_and_clear_bit(XBT_FORCE_FLUSH, &target->bt_flags);
1647         INIT_LIST_HEAD(list);
1648         spin_lock(&target->bt_delwri_lock);
1649         list_for_each_entry_safe(bp, n, &target->bt_delwri_queue, b_list) {
1650                 ASSERT(bp->b_flags & XBF_DELWRI);
1651
1652                 if (!xfs_buf_ispinned(bp) && xfs_buf_trylock(bp)) {
1653                         if (!force &&
1654                             time_before(jiffies, bp->b_queuetime + age)) {
1655                                 xfs_buf_unlock(bp);
1656                                 break;
1657                         }
1658
1659                         bp->b_flags &= ~(XBF_DELWRI | _XBF_DELWRI_Q);
1660                         bp->b_flags |= XBF_WRITE;
1661                         list_move_tail(&bp->b_list, list);
1662                         trace_xfs_buf_delwri_split(bp, _RET_IP_);
1663                 } else
1664                         skipped++;
1665         }
1666
1667         spin_unlock(&target->bt_delwri_lock);
1668         return skipped;
1669 }
1670
1671 /*
1672  * Compare function is more complex than it needs to be because
1673  * the return value is only 32 bits and we are doing comparisons
1674  * on 64 bit values
1675  */
1676 static int
1677 xfs_buf_cmp(
1678         void            *priv,
1679         struct list_head *a,
1680         struct list_head *b)
1681 {
1682         struct xfs_buf  *ap = container_of(a, struct xfs_buf, b_list);
1683         struct xfs_buf  *bp = container_of(b, struct xfs_buf, b_list);
1684         xfs_daddr_t             diff;
1685
1686         diff = ap->b_bn - bp->b_bn;
1687         if (diff < 0)
1688                 return -1;
1689         if (diff > 0)
1690                 return 1;
1691         return 0;
1692 }
1693
1694 STATIC int
1695 xfsbufd(
1696         void            *data)
1697 {
1698         xfs_buftarg_t   *target = (xfs_buftarg_t *)data;
1699
1700         current->flags |= PF_MEMALLOC;
1701
1702         set_freezable();
1703
1704         do {
1705                 long    age = xfs_buf_age_centisecs * msecs_to_jiffies(10);
1706                 long    tout = xfs_buf_timer_centisecs * msecs_to_jiffies(10);
1707                 struct list_head tmp;
1708                 struct blk_plug plug;
1709
1710                 if (unlikely(freezing(current))) {
1711                         set_bit(XBT_FORCE_SLEEP, &target->bt_flags);
1712                         refrigerator();
1713                 } else {
1714                         clear_bit(XBT_FORCE_SLEEP, &target->bt_flags);
1715                 }
1716
1717                 /* sleep for a long time if there is nothing to do. */
1718                 if (list_empty(&target->bt_delwri_queue))
1719                         tout = MAX_SCHEDULE_TIMEOUT;
1720                 schedule_timeout_interruptible(tout);
1721
1722                 xfs_buf_delwri_split(target, &tmp, age);
1723                 list_sort(NULL, &tmp, xfs_buf_cmp);
1724
1725                 blk_start_plug(&plug);
1726                 while (!list_empty(&tmp)) {
1727                         struct xfs_buf *bp;
1728                         bp = list_first_entry(&tmp, struct xfs_buf, b_list);
1729                         list_del_init(&bp->b_list);
1730                         xfs_bdstrat_cb(bp);
1731                 }
1732                 blk_finish_plug(&plug);
1733         } while (!kthread_should_stop());
1734
1735         return 0;
1736 }
1737
1738 /*
1739  *      Go through all incore buffers, and release buffers if they belong to
1740  *      the given device. This is used in filesystem error handling to
1741  *      preserve the consistency of its metadata.
1742  */
1743 int
1744 xfs_flush_buftarg(
1745         xfs_buftarg_t   *target,
1746         int             wait)
1747 {
1748         xfs_buf_t       *bp;
1749         int             pincount = 0;
1750         LIST_HEAD(tmp_list);
1751         LIST_HEAD(wait_list);
1752         struct blk_plug plug;
1753
1754         xfs_buf_runall_queues(xfsconvertd_workqueue);
1755         xfs_buf_runall_queues(xfsdatad_workqueue);
1756         xfs_buf_runall_queues(xfslogd_workqueue);
1757
1758         set_bit(XBT_FORCE_FLUSH, &target->bt_flags);
1759         pincount = xfs_buf_delwri_split(target, &tmp_list, 0);
1760
1761         /*
1762          * Dropped the delayed write list lock, now walk the temporary list.
1763          * All I/O is issued async and then if we need to wait for completion
1764          * we do that after issuing all the IO.
1765          */
1766         list_sort(NULL, &tmp_list, xfs_buf_cmp);
1767
1768         blk_start_plug(&plug);
1769         while (!list_empty(&tmp_list)) {
1770                 bp = list_first_entry(&tmp_list, struct xfs_buf, b_list);
1771                 ASSERT(target == bp->b_target);
1772                 list_del_init(&bp->b_list);
1773                 if (wait) {
1774                         bp->b_flags &= ~XBF_ASYNC;
1775                         list_add(&bp->b_list, &wait_list);
1776                 }
1777                 xfs_bdstrat_cb(bp);
1778         }
1779         blk_finish_plug(&plug);
1780
1781         if (wait) {
1782                 /* Wait for IO to complete. */
1783                 while (!list_empty(&wait_list)) {
1784                         bp = list_first_entry(&wait_list, struct xfs_buf, b_list);
1785
1786                         list_del_init(&bp->b_list);
1787                         xfs_buf_iowait(bp);
1788                         xfs_buf_relse(bp);
1789                 }
1790         }
1791
1792         return pincount;
1793 }
1794
1795 int __init
1796 xfs_buf_init(void)
1797 {
1798         xfs_buf_zone = kmem_zone_init_flags(sizeof(xfs_buf_t), "xfs_buf",
1799                                                 KM_ZONE_HWALIGN, NULL);
1800         if (!xfs_buf_zone)
1801                 goto out;
1802
1803         xfslogd_workqueue = alloc_workqueue("xfslogd",
1804                                         WQ_MEM_RECLAIM | WQ_HIGHPRI, 1);
1805         if (!xfslogd_workqueue)
1806                 goto out_free_buf_zone;
1807
1808         xfsdatad_workqueue = alloc_workqueue("xfsdatad", WQ_MEM_RECLAIM, 1);
1809         if (!xfsdatad_workqueue)
1810                 goto out_destroy_xfslogd_workqueue;
1811
1812         xfsconvertd_workqueue = alloc_workqueue("xfsconvertd",
1813                                                 WQ_MEM_RECLAIM, 1);
1814         if (!xfsconvertd_workqueue)
1815                 goto out_destroy_xfsdatad_workqueue;
1816
1817         return 0;
1818
1819  out_destroy_xfsdatad_workqueue:
1820         destroy_workqueue(xfsdatad_workqueue);
1821  out_destroy_xfslogd_workqueue:
1822         destroy_workqueue(xfslogd_workqueue);
1823  out_free_buf_zone:
1824         kmem_zone_destroy(xfs_buf_zone);
1825  out:
1826         return -ENOMEM;
1827 }
1828
1829 void
1830 xfs_buf_terminate(void)
1831 {
1832         destroy_workqueue(xfsconvertd_workqueue);
1833         destroy_workqueue(xfsdatad_workqueue);
1834         destroy_workqueue(xfslogd_workqueue);
1835         kmem_zone_destroy(xfs_buf_zone);
1836 }