linux/fs/xfs/xfs_iomap.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
   4 * Copyright (c) 2016-2018 Christoph Hellwig.
   5 * All Rights Reserved.
   6 */
   7#include "xfs.h"
   8#include "xfs_fs.h"
   9#include "xfs_shared.h"
  10#include "xfs_format.h"
  11#include "xfs_log_format.h"
  12#include "xfs_trans_resv.h"
  13#include "xfs_mount.h"
  14#include "xfs_inode.h"
  15#include "xfs_btree.h"
  16#include "xfs_bmap_btree.h"
  17#include "xfs_bmap.h"
  18#include "xfs_bmap_util.h"
  19#include "xfs_errortag.h"
  20#include "xfs_error.h"
  21#include "xfs_trans.h"
  22#include "xfs_trans_space.h"
  23#include "xfs_inode_item.h"
  24#include "xfs_iomap.h"
  25#include "xfs_trace.h"
  26#include "xfs_quota.h"
  27#include "xfs_dquot_item.h"
  28#include "xfs_dquot.h"
  29#include "xfs_reflink.h"
  30
  31
  32#define XFS_WRITEIO_ALIGN(mp,off)       (((off) >> mp->m_writeio_log) \
  33                                                << mp->m_writeio_log)
  34
  35static int
  36xfs_alert_fsblock_zero(
  37        xfs_inode_t     *ip,
  38        xfs_bmbt_irec_t *imap)
  39{
  40        xfs_alert_tag(ip->i_mount, XFS_PTAG_FSBLOCK_ZERO,
  41                        "Access to block zero in inode %llu "
  42                        "start_block: %llx start_off: %llx "
  43                        "blkcnt: %llx extent-state: %x",
  44                (unsigned long long)ip->i_ino,
  45                (unsigned long long)imap->br_startblock,
  46                (unsigned long long)imap->br_startoff,
  47                (unsigned long long)imap->br_blockcount,
  48                imap->br_state);
  49        return -EFSCORRUPTED;
  50}
  51
  52int
  53xfs_bmbt_to_iomap(
  54        struct xfs_inode        *ip,
  55        struct iomap            *iomap,
  56        struct xfs_bmbt_irec    *imap,
  57        bool                    shared)
  58{
  59        struct xfs_mount        *mp = ip->i_mount;
  60
  61        if (unlikely(!xfs_valid_startblock(ip, imap->br_startblock)))
  62                return xfs_alert_fsblock_zero(ip, imap);
  63
  64        if (imap->br_startblock == HOLESTARTBLOCK) {
  65                iomap->addr = IOMAP_NULL_ADDR;
  66                iomap->type = IOMAP_HOLE;
  67        } else if (imap->br_startblock == DELAYSTARTBLOCK ||
  68                   isnullstartblock(imap->br_startblock)) {
  69                iomap->addr = IOMAP_NULL_ADDR;
  70                iomap->type = IOMAP_DELALLOC;
  71        } else {
  72                iomap->addr = BBTOB(xfs_fsb_to_db(ip, imap->br_startblock));
  73                if (imap->br_state == XFS_EXT_UNWRITTEN)
  74                        iomap->type = IOMAP_UNWRITTEN;
  75                else
  76                        iomap->type = IOMAP_MAPPED;
  77        }
  78        iomap->offset = XFS_FSB_TO_B(mp, imap->br_startoff);
  79        iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount);
  80        iomap->bdev = xfs_find_bdev_for_inode(VFS_I(ip));
  81        iomap->dax_dev = xfs_find_daxdev_for_inode(VFS_I(ip));
  82
  83        if (xfs_ipincount(ip) &&
  84            (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
  85                iomap->flags |= IOMAP_F_DIRTY;
  86        if (shared)
  87                iomap->flags |= IOMAP_F_SHARED;
  88        return 0;
  89}
  90
  91static void
  92xfs_hole_to_iomap(
  93        struct xfs_inode        *ip,
  94        struct iomap            *iomap,
  95        xfs_fileoff_t           offset_fsb,
  96        xfs_fileoff_t           end_fsb)
  97{
  98        iomap->addr = IOMAP_NULL_ADDR;
  99        iomap->type = IOMAP_HOLE;
 100        iomap->offset = XFS_FSB_TO_B(ip->i_mount, offset_fsb);
 101        iomap->length = XFS_FSB_TO_B(ip->i_mount, end_fsb - offset_fsb);
 102        iomap->bdev = xfs_find_bdev_for_inode(VFS_I(ip));
 103        iomap->dax_dev = xfs_find_daxdev_for_inode(VFS_I(ip));
 104}
 105
 106xfs_extlen_t
 107xfs_eof_alignment(
 108        struct xfs_inode        *ip,
 109        xfs_extlen_t            extsize)
 110{
 111        struct xfs_mount        *mp = ip->i_mount;
 112        xfs_extlen_t            align = 0;
 113
 114        if (!XFS_IS_REALTIME_INODE(ip)) {
 115                /*
 116                 * Round up the allocation request to a stripe unit
 117                 * (m_dalign) boundary if the file size is >= stripe unit
 118                 * size, and we are allocating past the allocation eof.
 119                 *
 120                 * If mounted with the "-o swalloc" option the alignment is
 121                 * increased from the strip unit size to the stripe width.
 122                 */
 123                if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC))
 124                        align = mp->m_swidth;
 125                else if (mp->m_dalign)
 126                        align = mp->m_dalign;
 127
 128                if (align && XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, align))
 129                        align = 0;
 130        }
 131
 132        /*
 133         * Always round up the allocation request to an extent boundary
 134         * (when file on a real-time subvolume or has di_extsize hint).
 135         */
 136        if (extsize) {
 137                if (align)
 138                        align = roundup_64(align, extsize);
 139                else
 140                        align = extsize;
 141        }
 142
 143        return align;
 144}
 145
 146STATIC int
 147xfs_iomap_eof_align_last_fsb(
 148        struct xfs_inode        *ip,
 149        xfs_extlen_t            extsize,
 150        xfs_fileoff_t           *last_fsb)
 151{
 152        xfs_extlen_t            align = xfs_eof_alignment(ip, extsize);
 153
 154        if (align) {
 155                xfs_fileoff_t   new_last_fsb = roundup_64(*last_fsb, align);
 156                int             eof, error;
 157
 158                error = xfs_bmap_eof(ip, new_last_fsb, XFS_DATA_FORK, &eof);
 159                if (error)
 160                        return error;
 161                if (eof)
 162                        *last_fsb = new_last_fsb;
 163        }
 164        return 0;
 165}
 166
 167int
 168xfs_iomap_write_direct(
 169        xfs_inode_t     *ip,
 170        xfs_off_t       offset,
 171        size_t          count,
 172        xfs_bmbt_irec_t *imap,
 173        int             nmaps)
 174{
 175        xfs_mount_t     *mp = ip->i_mount;
 176        xfs_fileoff_t   offset_fsb;
 177        xfs_fileoff_t   last_fsb;
 178        xfs_filblks_t   count_fsb, resaligned;
 179        xfs_extlen_t    extsz;
 180        int             nimaps;
 181        int             quota_flag;
 182        int             rt;
 183        xfs_trans_t     *tp;
 184        uint            qblocks, resblks, resrtextents;
 185        int             error;
 186        int             lockmode;
 187        int             bmapi_flags = XFS_BMAPI_PREALLOC;
 188        uint            tflags = 0;
 189
 190        rt = XFS_IS_REALTIME_INODE(ip);
 191        extsz = xfs_get_extsz_hint(ip);
 192        lockmode = XFS_ILOCK_SHARED;    /* locked by caller */
 193
 194        ASSERT(xfs_isilocked(ip, lockmode));
 195
 196        offset_fsb = XFS_B_TO_FSBT(mp, offset);
 197        last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));
 198        if ((offset + count) > XFS_ISIZE(ip)) {
 199                /*
 200                 * Assert that the in-core extent list is present since this can
 201                 * call xfs_iread_extents() and we only have the ilock shared.
 202                 * This should be safe because the lock was held around a bmapi
 203                 * call in the caller and we only need it to access the in-core
 204                 * list.
 205                 */
 206                ASSERT(XFS_IFORK_PTR(ip, XFS_DATA_FORK)->if_flags &
 207                                                                XFS_IFEXTENTS);
 208                error = xfs_iomap_eof_align_last_fsb(ip, extsz, &last_fsb);
 209                if (error)
 210                        goto out_unlock;
 211        } else {
 212                if (nmaps && (imap->br_startblock == HOLESTARTBLOCK))
 213                        last_fsb = min(last_fsb, (xfs_fileoff_t)
 214                                        imap->br_blockcount +
 215                                        imap->br_startoff);
 216        }
 217        count_fsb = last_fsb - offset_fsb;
 218        ASSERT(count_fsb > 0);
 219        resaligned = xfs_aligned_fsb_count(offset_fsb, count_fsb, extsz);
 220
 221        if (unlikely(rt)) {
 222                resrtextents = qblocks = resaligned;
 223                resrtextents /= mp->m_sb.sb_rextsize;
 224                resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
 225                quota_flag = XFS_QMOPT_RES_RTBLKS;
 226        } else {
 227                resrtextents = 0;
 228                resblks = qblocks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
 229                quota_flag = XFS_QMOPT_RES_REGBLKS;
 230        }
 231
 232        /*
 233         * Drop the shared lock acquired by the caller, attach the dquot if
 234         * necessary and move on to transaction setup.
 235         */
 236        xfs_iunlock(ip, lockmode);
 237        error = xfs_qm_dqattach(ip);
 238        if (error)
 239                return error;
 240
 241        /*
 242         * For DAX, we do not allocate unwritten extents, but instead we zero
 243         * the block before we commit the transaction.  Ideally we'd like to do
 244         * this outside the transaction context, but if we commit and then crash
 245         * we may not have zeroed the blocks and this will be exposed on
 246         * recovery of the allocation. Hence we must zero before commit.
 247         *
 248         * Further, if we are mapping unwritten extents here, we need to zero
 249         * and convert them to written so that we don't need an unwritten extent
 250         * callback for DAX. This also means that we need to be able to dip into
 251         * the reserve block pool for bmbt block allocation if there is no space
 252         * left but we need to do unwritten extent conversion.
 253         */
 254        if (IS_DAX(VFS_I(ip))) {
 255                bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;
 256                if (imap->br_state == XFS_EXT_UNWRITTEN) {
 257                        tflags |= XFS_TRANS_RESERVE;
 258                        resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
 259                }
 260        }
 261        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, resrtextents,
 262                        tflags, &tp);
 263        if (error)
 264                return error;
 265
 266        lockmode = XFS_ILOCK_EXCL;
 267        xfs_ilock(ip, lockmode);
 268
 269        error = xfs_trans_reserve_quota_nblks(tp, ip, qblocks, 0, quota_flag);
 270        if (error)
 271                goto out_trans_cancel;
 272
 273        xfs_trans_ijoin(tp, ip, 0);
 274
 275        /*
 276         * From this point onwards we overwrite the imap pointer that the
 277         * caller gave to us.
 278         */
 279        nimaps = 1;
 280        error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
 281                                bmapi_flags, resblks, imap, &nimaps);
 282        if (error)
 283                goto out_res_cancel;
 284
 285        /*
 286         * Complete the transaction
 287         */
 288        error = xfs_trans_commit(tp);
 289        if (error)
 290                goto out_unlock;
 291
 292        /*
 293         * Copy any maps to caller's array and return any error.
 294         */
 295        if (nimaps == 0) {
 296                error = -ENOSPC;
 297                goto out_unlock;
 298        }
 299
 300        if (unlikely(!xfs_valid_startblock(ip, imap->br_startblock)))
 301                error = xfs_alert_fsblock_zero(ip, imap);
 302
 303out_unlock:
 304        xfs_iunlock(ip, lockmode);
 305        return error;
 306
 307out_res_cancel:
 308        xfs_trans_unreserve_quota_nblks(tp, ip, (long)qblocks, 0, quota_flag);
 309out_trans_cancel:
 310        xfs_trans_cancel(tp);
 311        goto out_unlock;
 312}
 313
 314STATIC bool
 315xfs_quota_need_throttle(
 316        struct xfs_inode *ip,
 317        int type,
 318        xfs_fsblock_t alloc_blocks)
 319{
 320        struct xfs_dquot *dq = xfs_inode_dquot(ip, type);
 321
 322        if (!dq || !xfs_this_quota_on(ip->i_mount, type))
 323                return false;
 324
 325        /* no hi watermark, no throttle */
 326        if (!dq->q_prealloc_hi_wmark)
 327                return false;
 328
 329        /* under the lo watermark, no throttle */
 330        if (dq->q_res_bcount + alloc_blocks < dq->q_prealloc_lo_wmark)
 331                return false;
 332
 333        return true;
 334}
 335
 336STATIC void
 337xfs_quota_calc_throttle(
 338        struct xfs_inode *ip,
 339        int type,
 340        xfs_fsblock_t *qblocks,
 341        int *qshift,
 342        int64_t *qfreesp)
 343{
 344        int64_t freesp;
 345        int shift = 0;
 346        struct xfs_dquot *dq = xfs_inode_dquot(ip, type);
 347
 348        /* no dq, or over hi wmark, squash the prealloc completely */
 349        if (!dq || dq->q_res_bcount >= dq->q_prealloc_hi_wmark) {
 350                *qblocks = 0;
 351                *qfreesp = 0;
 352                return;
 353        }
 354
 355        freesp = dq->q_prealloc_hi_wmark - dq->q_res_bcount;
 356        if (freesp < dq->q_low_space[XFS_QLOWSP_5_PCNT]) {
 357                shift = 2;
 358                if (freesp < dq->q_low_space[XFS_QLOWSP_3_PCNT])
 359                        shift += 2;
 360                if (freesp < dq->q_low_space[XFS_QLOWSP_1_PCNT])
 361                        shift += 2;
 362        }
 363
 364        if (freesp < *qfreesp)
 365                *qfreesp = freesp;
 366
 367        /* only overwrite the throttle values if we are more aggressive */
 368        if ((freesp >> shift) < (*qblocks >> *qshift)) {
 369                *qblocks = freesp;
 370                *qshift = shift;
 371        }
 372}
 373
 374/*
 375 * If we are doing a write at the end of the file and there are no allocations
 376 * past this one, then extend the allocation out to the file system's write
 377 * iosize.
 378 *
 379 * If we don't have a user specified preallocation size, dynamically increase
 380 * the preallocation size as the size of the file grows.  Cap the maximum size
 381 * at a single extent or less if the filesystem is near full. The closer the
 382 * filesystem is to full, the smaller the maximum prealocation.
 383 *
 384 * As an exception we don't do any preallocation at all if the file is smaller
 385 * than the minimum preallocation and we are using the default dynamic
 386 * preallocation scheme, as it is likely this is the only write to the file that
 387 * is going to be done.
 388 *
 389 * We clean up any extra space left over when the file is closed in
 390 * xfs_inactive().
 391 */
 392STATIC xfs_fsblock_t
 393xfs_iomap_prealloc_size(
 394        struct xfs_inode        *ip,
 395        int                     whichfork,
 396        loff_t                  offset,
 397        loff_t                  count,
 398        struct xfs_iext_cursor  *icur)
 399{
 400        struct xfs_mount        *mp = ip->i_mount;
 401        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
 402        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
 403        struct xfs_bmbt_irec    prev;
 404        int                     shift = 0;
 405        int64_t                 freesp;
 406        xfs_fsblock_t           qblocks;
 407        int                     qshift = 0;
 408        xfs_fsblock_t           alloc_blocks = 0;
 409
 410        if (offset + count <= XFS_ISIZE(ip))
 411                return 0;
 412
 413        if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE) &&
 414            (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_writeio_blocks)))
 415                return 0;
 416
 417        /*
 418         * If an explicit allocsize is set, the file is small, or we
 419         * are writing behind a hole, then use the minimum prealloc:
 420         */
 421        if ((mp->m_flags & XFS_MOUNT_DFLT_IOSIZE) ||
 422            XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) ||
 423            !xfs_iext_peek_prev_extent(ifp, icur, &prev) ||
 424            prev.br_startoff + prev.br_blockcount < offset_fsb)
 425                return mp->m_writeio_blocks;
 426
 427        /*
 428         * Determine the initial size of the preallocation. We are beyond the
 429         * current EOF here, but we need to take into account whether this is
 430         * a sparse write or an extending write when determining the
 431         * preallocation size.  Hence we need to look up the extent that ends
 432         * at the current write offset and use the result to determine the
 433         * preallocation size.
 434         *
 435         * If the extent is a hole, then preallocation is essentially disabled.
 436         * Otherwise we take the size of the preceding data extent as the basis
 437         * for the preallocation size. If the size of the extent is greater than
 438         * half the maximum extent length, then use the current offset as the
 439         * basis. This ensures that for large files the preallocation size
 440         * always extends to MAXEXTLEN rather than falling short due to things
 441         * like stripe unit/width alignment of real extents.
 442         */
 443        if (prev.br_blockcount <= (MAXEXTLEN >> 1))
 444                alloc_blocks = prev.br_blockcount << 1;
 445        else
 446                alloc_blocks = XFS_B_TO_FSB(mp, offset);
 447        if (!alloc_blocks)
 448                goto check_writeio;
 449        qblocks = alloc_blocks;
 450
 451        /*
 452         * MAXEXTLEN is not a power of two value but we round the prealloc down
 453         * to the nearest power of two value after throttling. To prevent the
 454         * round down from unconditionally reducing the maximum supported prealloc
 455         * size, we round up first, apply appropriate throttling, round down and
 456         * cap the value to MAXEXTLEN.
 457         */
 458        alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(MAXEXTLEN),
 459                                       alloc_blocks);
 460
 461        freesp = percpu_counter_read_positive(&mp->m_fdblocks);
 462        if (freesp < mp->m_low_space[XFS_LOWSP_5_PCNT]) {
 463                shift = 2;
 464                if (freesp < mp->m_low_space[XFS_LOWSP_4_PCNT])
 465                        shift++;
 466                if (freesp < mp->m_low_space[XFS_LOWSP_3_PCNT])
 467                        shift++;
 468                if (freesp < mp->m_low_space[XFS_LOWSP_2_PCNT])
 469                        shift++;
 470                if (freesp < mp->m_low_space[XFS_LOWSP_1_PCNT])
 471                        shift++;
 472        }
 473
 474        /*
 475         * Check each quota to cap the prealloc size, provide a shift value to
 476         * throttle with and adjust amount of available space.
 477         */
 478        if (xfs_quota_need_throttle(ip, XFS_DQ_USER, alloc_blocks))
 479                xfs_quota_calc_throttle(ip, XFS_DQ_USER, &qblocks, &qshift,
 480                                        &freesp);
 481        if (xfs_quota_need_throttle(ip, XFS_DQ_GROUP, alloc_blocks))
 482                xfs_quota_calc_throttle(ip, XFS_DQ_GROUP, &qblocks, &qshift,
 483                                        &freesp);
 484        if (xfs_quota_need_throttle(ip, XFS_DQ_PROJ, alloc_blocks))
 485                xfs_quota_calc_throttle(ip, XFS_DQ_PROJ, &qblocks, &qshift,
 486                                        &freesp);
 487
 488        /*
 489         * The final prealloc size is set to the minimum of free space available
 490         * in each of the quotas and the overall filesystem.
 491         *
 492         * The shift throttle value is set to the maximum value as determined by
 493         * the global low free space values and per-quota low free space values.
 494         */
 495        alloc_blocks = min(alloc_blocks, qblocks);
 496        shift = max(shift, qshift);
 497
 498        if (shift)
 499                alloc_blocks >>= shift;
 500        /*
 501         * rounddown_pow_of_two() returns an undefined result if we pass in
 502         * alloc_blocks = 0.
 503         */
 504        if (alloc_blocks)
 505                alloc_blocks = rounddown_pow_of_two(alloc_blocks);
 506        if (alloc_blocks > MAXEXTLEN)
 507                alloc_blocks = MAXEXTLEN;
 508
 509        /*
 510         * If we are still trying to allocate more space than is
 511         * available, squash the prealloc hard. This can happen if we
 512         * have a large file on a small filesystem and the above
 513         * lowspace thresholds are smaller than MAXEXTLEN.
 514         */
 515        while (alloc_blocks && alloc_blocks >= freesp)
 516                alloc_blocks >>= 4;
 517check_writeio:
 518        if (alloc_blocks < mp->m_writeio_blocks)
 519                alloc_blocks = mp->m_writeio_blocks;
 520        trace_xfs_iomap_prealloc_size(ip, alloc_blocks, shift,
 521                                      mp->m_writeio_blocks);
 522        return alloc_blocks;
 523}
 524
 525static int
 526xfs_file_iomap_begin_delay(
 527        struct inode            *inode,
 528        loff_t                  offset,
 529        loff_t                  count,
 530        unsigned                flags,
 531        struct iomap            *iomap)
 532{
 533        struct xfs_inode        *ip = XFS_I(inode);
 534        struct xfs_mount        *mp = ip->i_mount;
 535        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
 536        xfs_fileoff_t           maxbytes_fsb =
 537                XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
 538        xfs_fileoff_t           end_fsb;
 539        struct xfs_bmbt_irec    imap, cmap;
 540        struct xfs_iext_cursor  icur, ccur;
 541        xfs_fsblock_t           prealloc_blocks = 0;
 542        bool                    eof = false, cow_eof = false, shared = false;
 543        int                     whichfork = XFS_DATA_FORK;
 544        int                     error = 0;
 545
 546        ASSERT(!XFS_IS_REALTIME_INODE(ip));
 547        ASSERT(!xfs_get_extsz_hint(ip));
 548
 549        xfs_ilock(ip, XFS_ILOCK_EXCL);
 550
 551        if (unlikely(XFS_TEST_ERROR(
 552            (XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_EXTENTS &&
 553             XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_BTREE),
 554             mp, XFS_ERRTAG_BMAPIFORMAT))) {
 555                XFS_ERROR_REPORT(__func__, XFS_ERRLEVEL_LOW, mp);
 556                error = -EFSCORRUPTED;
 557                goto out_unlock;
 558        }
 559
 560        XFS_STATS_INC(mp, xs_blk_mapw);
 561
 562        if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) {
 563                error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
 564                if (error)
 565                        goto out_unlock;
 566        }
 567
 568        end_fsb = min(XFS_B_TO_FSB(mp, offset + count), maxbytes_fsb);
 569
 570        /*
 571         * Search the data fork fork first to look up our source mapping.  We
 572         * always need the data fork map, as we have to return it to the
 573         * iomap code so that the higher level write code can read data in to
 574         * perform read-modify-write cycles for unaligned writes.
 575         */
 576        eof = !xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap);
 577        if (eof)
 578                imap.br_startoff = end_fsb; /* fake hole until the end */
 579
 580        /* We never need to allocate blocks for zeroing a hole. */
 581        if ((flags & IOMAP_ZERO) && imap.br_startoff > offset_fsb) {
 582                xfs_hole_to_iomap(ip, iomap, offset_fsb, imap.br_startoff);
 583                goto out_unlock;
 584        }
 585
 586        /*
 587         * Search the COW fork extent list even if we did not find a data fork
 588         * extent.  This serves two purposes: first this implements the
 589         * speculative preallocation using cowextsize, so that we also unshare
 590         * block adjacent to shared blocks instead of just the shared blocks
 591         * themselves.  Second the lookup in the extent list is generally faster
 592         * than going out to the shared extent tree.
 593         */
 594        if (xfs_is_cow_inode(ip)) {
 595                if (!ip->i_cowfp) {
 596                        ASSERT(!xfs_is_reflink_inode(ip));
 597                        xfs_ifork_init_cow(ip);
 598                }
 599                cow_eof = !xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb,
 600                                &ccur, &cmap);
 601                if (!cow_eof && cmap.br_startoff <= offset_fsb) {
 602                        trace_xfs_reflink_cow_found(ip, &cmap);
 603                        whichfork = XFS_COW_FORK;
 604                        goto done;
 605                }
 606        }
 607
 608        if (imap.br_startoff <= offset_fsb) {
 609                /*
 610                 * For reflink files we may need a delalloc reservation when
 611                 * overwriting shared extents.   This includes zeroing of
 612                 * existing extents that contain data.
 613                 */
 614                if (!xfs_is_cow_inode(ip) ||
 615                    ((flags & IOMAP_ZERO) && imap.br_state != XFS_EXT_NORM)) {
 616                        trace_xfs_iomap_found(ip, offset, count, XFS_DATA_FORK,
 617                                        &imap);
 618                        goto done;
 619                }
 620
 621                xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);
 622
 623                /* Trim the mapping to the nearest shared extent boundary. */
 624                error = xfs_inode_need_cow(ip, &imap, &shared);
 625                if (error)
 626                        goto out_unlock;
 627
 628                /* Not shared?  Just report the (potentially capped) extent. */
 629                if (!shared) {
 630                        trace_xfs_iomap_found(ip, offset, count, XFS_DATA_FORK,
 631                                        &imap);
 632                        goto done;
 633                }
 634
 635                /*
 636                 * Fork all the shared blocks from our write offset until the
 637                 * end of the extent.
 638                 */
 639                whichfork = XFS_COW_FORK;
 640                end_fsb = imap.br_startoff + imap.br_blockcount;
 641        } else {
 642                /*
 643                 * We cap the maximum length we map here to MAX_WRITEBACK_PAGES
 644                 * pages to keep the chunks of work done where somewhat
 645                 * symmetric with the work writeback does.  This is a completely
 646                 * arbitrary number pulled out of thin air.
 647                 *
 648                 * Note that the values needs to be less than 32-bits wide until
 649                 * the lower level functions are updated.
 650                 */
 651                count = min_t(loff_t, count, 1024 * PAGE_SIZE);
 652                end_fsb = min(XFS_B_TO_FSB(mp, offset + count), maxbytes_fsb);
 653
 654                if (xfs_is_always_cow_inode(ip))
 655                        whichfork = XFS_COW_FORK;
 656        }
 657
 658        error = xfs_qm_dqattach_locked(ip, false);
 659        if (error)
 660                goto out_unlock;
 661
 662        if (eof) {
 663                prealloc_blocks = xfs_iomap_prealloc_size(ip, whichfork, offset,
 664                                count, &icur);
 665                if (prealloc_blocks) {
 666                        xfs_extlen_t    align;
 667                        xfs_off_t       end_offset;
 668                        xfs_fileoff_t   p_end_fsb;
 669
 670                        end_offset = XFS_WRITEIO_ALIGN(mp, offset + count - 1);
 671                        p_end_fsb = XFS_B_TO_FSBT(mp, end_offset) +
 672                                        prealloc_blocks;
 673
 674                        align = xfs_eof_alignment(ip, 0);
 675                        if (align)
 676                                p_end_fsb = roundup_64(p_end_fsb, align);
 677
 678                        p_end_fsb = min(p_end_fsb, maxbytes_fsb);
 679                        ASSERT(p_end_fsb > offset_fsb);
 680                        prealloc_blocks = p_end_fsb - end_fsb;
 681                }
 682        }
 683
 684retry:
 685        error = xfs_bmapi_reserve_delalloc(ip, whichfork, offset_fsb,
 686                        end_fsb - offset_fsb, prealloc_blocks,
 687                        whichfork == XFS_DATA_FORK ? &imap : &cmap,
 688                        whichfork == XFS_DATA_FORK ? &icur : &ccur,
 689                        whichfork == XFS_DATA_FORK ? eof : cow_eof);
 690        switch (error) {
 691        case 0:
 692                break;
 693        case -ENOSPC:
 694        case -EDQUOT:
 695                /* retry without any preallocation */
 696                trace_xfs_delalloc_enospc(ip, offset, count);
 697                if (prealloc_blocks) {
 698                        prealloc_blocks = 0;
 699                        goto retry;
 700                }
 701                /*FALLTHRU*/
 702        default:
 703                goto out_unlock;
 704        }
 705
 706        /*
 707         * Flag newly allocated delalloc blocks with IOMAP_F_NEW so we punch
 708         * them out if the write happens to fail.
 709         */
 710        iomap->flags |= IOMAP_F_NEW;
 711        trace_xfs_iomap_alloc(ip, offset, count, whichfork,
 712                        whichfork == XFS_DATA_FORK ? &imap : &cmap);
 713done:
 714        if (whichfork == XFS_COW_FORK) {
 715                if (imap.br_startoff > offset_fsb) {
 716                        xfs_trim_extent(&cmap, offset_fsb,
 717                                        imap.br_startoff - offset_fsb);
 718                        error = xfs_bmbt_to_iomap(ip, iomap, &cmap, true);
 719                        goto out_unlock;
 720                }
 721                /* ensure we only report blocks we have a reservation for */
 722                xfs_trim_extent(&imap, cmap.br_startoff, cmap.br_blockcount);
 723                shared = true;
 724        }
 725        error = xfs_bmbt_to_iomap(ip, iomap, &imap, shared);
 726out_unlock:
 727        xfs_iunlock(ip, XFS_ILOCK_EXCL);
 728        return error;
 729}
 730
 731int
 732xfs_iomap_write_unwritten(
 733        xfs_inode_t     *ip,
 734        xfs_off_t       offset,
 735        xfs_off_t       count,
 736        bool            update_isize)
 737{
 738        xfs_mount_t     *mp = ip->i_mount;
 739        xfs_fileoff_t   offset_fsb;
 740        xfs_filblks_t   count_fsb;
 741        xfs_filblks_t   numblks_fsb;
 742        int             nimaps;
 743        xfs_trans_t     *tp;
 744        xfs_bmbt_irec_t imap;
 745        struct inode    *inode = VFS_I(ip);
 746        xfs_fsize_t     i_size;
 747        uint            resblks;
 748        int             error;
 749
 750        trace_xfs_unwritten_convert(ip, offset, count);
 751
 752        offset_fsb = XFS_B_TO_FSBT(mp, offset);
 753        count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
 754        count_fsb = (xfs_filblks_t)(count_fsb - offset_fsb);
 755
 756        /*
 757         * Reserve enough blocks in this transaction for two complete extent
 758         * btree splits.  We may be converting the middle part of an unwritten
 759         * extent and in this case we will insert two new extents in the btree
 760         * each of which could cause a full split.
 761         *
 762         * This reservation amount will be used in the first call to
 763         * xfs_bmbt_split() to select an AG with enough space to satisfy the
 764         * rest of the operation.
 765         */
 766        resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
 767
 768        do {
 769                /*
 770                 * Set up a transaction to convert the range of extents
 771                 * from unwritten to real. Do allocations in a loop until
 772                 * we have covered the range passed in.
 773                 *
 774                 * Note that we can't risk to recursing back into the filesystem
 775                 * here as we might be asked to write out the same inode that we
 776                 * complete here and might deadlock on the iolock.
 777                 */
 778                error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
 779                                XFS_TRANS_RESERVE, &tp);
 780                if (error)
 781                        return error;
 782
 783                xfs_ilock(ip, XFS_ILOCK_EXCL);
 784                xfs_trans_ijoin(tp, ip, 0);
 785
 786                /*
 787                 * Modify the unwritten extent state of the buffer.
 788                 */
 789                nimaps = 1;
 790                error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
 791                                        XFS_BMAPI_CONVERT, resblks, &imap,
 792                                        &nimaps);
 793                if (error)
 794                        goto error_on_bmapi_transaction;
 795
 796                /*
 797                 * Log the updated inode size as we go.  We have to be careful
 798                 * to only log it up to the actual write offset if it is
 799                 * halfway into a block.
 800                 */
 801                i_size = XFS_FSB_TO_B(mp, offset_fsb + count_fsb);
 802                if (i_size > offset + count)
 803                        i_size = offset + count;
 804                if (update_isize && i_size > i_size_read(inode))
 805                        i_size_write(inode, i_size);
 806                i_size = xfs_new_eof(ip, i_size);
 807                if (i_size) {
 808                        ip->i_d.di_size = i_size;
 809                        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 810                }
 811
 812                error = xfs_trans_commit(tp);
 813                xfs_iunlock(ip, XFS_ILOCK_EXCL);
 814                if (error)
 815                        return error;
 816
 817                if (unlikely(!xfs_valid_startblock(ip, imap.br_startblock)))
 818                        return xfs_alert_fsblock_zero(ip, &imap);
 819
 820                if ((numblks_fsb = imap.br_blockcount) == 0) {
 821                        /*
 822                         * The numblks_fsb value should always get
 823                         * smaller, otherwise the loop is stuck.
 824                         */
 825                        ASSERT(imap.br_blockcount);
 826                        break;
 827                }
 828                offset_fsb += numblks_fsb;
 829                count_fsb -= numblks_fsb;
 830        } while (count_fsb > 0);
 831
 832        return 0;
 833
 834error_on_bmapi_transaction:
 835        xfs_trans_cancel(tp);
 836        xfs_iunlock(ip, XFS_ILOCK_EXCL);
 837        return error;
 838}
 839
 840static inline bool
 841imap_needs_alloc(
 842        struct inode            *inode,
 843        struct xfs_bmbt_irec    *imap,
 844        int                     nimaps)
 845{
 846        return !nimaps ||
 847                imap->br_startblock == HOLESTARTBLOCK ||
 848                imap->br_startblock == DELAYSTARTBLOCK ||
 849                (IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN);
 850}
 851
 852static inline bool
 853needs_cow_for_zeroing(
 854        struct xfs_bmbt_irec    *imap,
 855        int                     nimaps)
 856{
 857        return nimaps &&
 858                imap->br_startblock != HOLESTARTBLOCK &&
 859                imap->br_state != XFS_EXT_UNWRITTEN;
 860}
 861
 862static int
 863xfs_ilock_for_iomap(
 864        struct xfs_inode        *ip,
 865        unsigned                flags,
 866        unsigned                *lockmode)
 867{
 868        unsigned                mode = XFS_ILOCK_SHARED;
 869        bool                    is_write = flags & (IOMAP_WRITE | IOMAP_ZERO);
 870
 871        /*
 872         * COW writes may allocate delalloc space or convert unwritten COW
 873         * extents, so we need to make sure to take the lock exclusively here.
 874         */
 875        if (xfs_is_cow_inode(ip) && is_write) {
 876                /*
 877                 * FIXME: It could still overwrite on unshared extents and not
 878                 * need allocation.
 879                 */
 880                if (flags & IOMAP_NOWAIT)
 881                        return -EAGAIN;
 882                mode = XFS_ILOCK_EXCL;
 883        }
 884
 885        /*
 886         * Extents not yet cached requires exclusive access, don't block.  This
 887         * is an opencoded xfs_ilock_data_map_shared() call but with
 888         * non-blocking behaviour.
 889         */
 890        if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) {
 891                if (flags & IOMAP_NOWAIT)
 892                        return -EAGAIN;
 893                mode = XFS_ILOCK_EXCL;
 894        }
 895
 896relock:
 897        if (flags & IOMAP_NOWAIT) {
 898                if (!xfs_ilock_nowait(ip, mode))
 899                        return -EAGAIN;
 900        } else {
 901                xfs_ilock(ip, mode);
 902        }
 903
 904        /*
 905         * The reflink iflag could have changed since the earlier unlocked
 906         * check, so if we got ILOCK_SHARED for a write and but we're now a
 907         * reflink inode we have to switch to ILOCK_EXCL and relock.
 908         */
 909        if (mode == XFS_ILOCK_SHARED && is_write && xfs_is_cow_inode(ip)) {
 910                xfs_iunlock(ip, mode);
 911                mode = XFS_ILOCK_EXCL;
 912                goto relock;
 913        }
 914
 915        *lockmode = mode;
 916        return 0;
 917}
 918
 919static int
 920xfs_file_iomap_begin(
 921        struct inode            *inode,
 922        loff_t                  offset,
 923        loff_t                  length,
 924        unsigned                flags,
 925        struct iomap            *iomap)
 926{
 927        struct xfs_inode        *ip = XFS_I(inode);
 928        struct xfs_mount        *mp = ip->i_mount;
 929        struct xfs_bmbt_irec    imap;
 930        xfs_fileoff_t           offset_fsb, end_fsb;
 931        int                     nimaps = 1, error = 0;
 932        bool                    shared = false;
 933        unsigned                lockmode;
 934
 935        if (XFS_FORCED_SHUTDOWN(mp))
 936                return -EIO;
 937
 938        if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && !(flags & IOMAP_DIRECT) &&
 939                        !IS_DAX(inode) && !xfs_get_extsz_hint(ip)) {
 940                /* Reserve delalloc blocks for regular writeback. */
 941                return xfs_file_iomap_begin_delay(inode, offset, length, flags,
 942                                iomap);
 943        }
 944
 945        /*
 946         * Lock the inode in the manner required for the specified operation and
 947         * check for as many conditions that would result in blocking as
 948         * possible. This removes most of the non-blocking checks from the
 949         * mapping code below.
 950         */
 951        error = xfs_ilock_for_iomap(ip, flags, &lockmode);
 952        if (error)
 953                return error;
 954
 955        ASSERT(offset <= mp->m_super->s_maxbytes);
 956        if (offset > mp->m_super->s_maxbytes - length)
 957                length = mp->m_super->s_maxbytes - offset;
 958        offset_fsb = XFS_B_TO_FSBT(mp, offset);
 959        end_fsb = XFS_B_TO_FSB(mp, offset + length);
 960
 961        error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
 962                               &nimaps, 0);
 963        if (error)
 964                goto out_unlock;
 965
 966        if (flags & IOMAP_REPORT) {
 967                /* Trim the mapping to the nearest shared extent boundary. */
 968                error = xfs_reflink_trim_around_shared(ip, &imap, &shared);
 969                if (error)
 970                        goto out_unlock;
 971        }
 972
 973        /* Non-modifying mapping requested, so we are done */
 974        if (!(flags & (IOMAP_WRITE | IOMAP_ZERO)))
 975                goto out_found;
 976
 977        /*
 978         * Break shared extents if necessary. Checks for non-blocking IO have
 979         * been done up front, so we don't need to do them here.
 980         */
 981        if (xfs_is_cow_inode(ip)) {
 982                struct xfs_bmbt_irec    cmap;
 983                bool                    directio = (flags & IOMAP_DIRECT);
 984
 985                /* if zeroing doesn't need COW allocation, then we are done. */
 986                if ((flags & IOMAP_ZERO) &&
 987                    !needs_cow_for_zeroing(&imap, nimaps))
 988                        goto out_found;
 989
 990                /* may drop and re-acquire the ilock */
 991                cmap = imap;
 992                error = xfs_reflink_allocate_cow(ip, &cmap, &shared, &lockmode,
 993                                directio);
 994                if (error)
 995                        goto out_unlock;
 996
 997                /*
 998                 * For buffered writes we need to report the address of the
 999                 * previous block (if there was any) so that the higher level
1000                 * write code can perform read-modify-write operations; we
1001                 * won't need the CoW fork mapping until writeback.  For direct
1002                 * I/O, which must be block aligned, we need to report the
1003                 * newly allocated address.  If the data fork has a hole, copy
1004                 * the COW fork mapping to avoid allocating to the data fork.
1005                 */
1006                if (directio || imap.br_startblock == HOLESTARTBLOCK)
1007                        imap = cmap;
1008
1009                end_fsb = imap.br_startoff + imap.br_blockcount;
1010                length = XFS_FSB_TO_B(mp, end_fsb) - offset;
1011        }
1012
1013        /* Don't need to allocate over holes when doing zeroing operations. */
1014        if (flags & IOMAP_ZERO)
1015                goto out_found;
1016
1017        if (!imap_needs_alloc(inode, &imap, nimaps))
1018                goto out_found;
1019
1020        /* If nowait is set bail since we are going to make allocations. */
1021        if (flags & IOMAP_NOWAIT) {
1022                error = -EAGAIN;
1023                goto out_unlock;
1024        }
1025
1026        /*
1027         * We cap the maximum length we map to a sane size  to keep the chunks
1028         * of work done where somewhat symmetric with the work writeback does.
1029         * This is a completely arbitrary number pulled out of thin air as a
1030         * best guess for initial testing.
1031         *
1032         * Note that the values needs to be less than 32-bits wide until the
1033         * lower level functions are updated.
1034         */
1035        length = min_t(loff_t, length, 1024 * PAGE_SIZE);
1036
1037        /*
1038         * xfs_iomap_write_direct() expects the shared lock. It is unlocked on
1039         * return.
1040         */
1041        if (lockmode == XFS_ILOCK_EXCL)
1042                xfs_ilock_demote(ip, lockmode);
1043        error = xfs_iomap_write_direct(ip, offset, length, &imap,
1044                        nimaps);
1045        if (error)
1046                return error;
1047
1048        iomap->flags |= IOMAP_F_NEW;
1049        trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);
1050
1051out_finish:
1052        return xfs_bmbt_to_iomap(ip, iomap, &imap, shared);
1053
1054out_found:
1055        ASSERT(nimaps);
1056        xfs_iunlock(ip, lockmode);
1057        trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
1058        goto out_finish;
1059
1060out_unlock:
1061        xfs_iunlock(ip, lockmode);
1062        return error;
1063}
1064
1065static int
1066xfs_file_iomap_end_delalloc(
1067        struct xfs_inode        *ip,
1068        loff_t                  offset,
1069        loff_t                  length,
1070        ssize_t                 written,
1071        struct iomap            *iomap)
1072{
1073        struct xfs_mount        *mp = ip->i_mount;
1074        xfs_fileoff_t           start_fsb;
1075        xfs_fileoff_t           end_fsb;
1076        int                     error = 0;
1077
1078        /*
1079         * Behave as if the write failed if drop writes is enabled. Set the NEW
1080         * flag to force delalloc cleanup.
1081         */
1082        if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_DROP_WRITES)) {
1083                iomap->flags |= IOMAP_F_NEW;
1084                written = 0;
1085        }
1086
1087        /*
1088         * start_fsb refers to the first unused block after a short write. If
1089         * nothing was written, round offset down to point at the first block in
1090         * the range.
1091         */
1092        if (unlikely(!written))
1093                start_fsb = XFS_B_TO_FSBT(mp, offset);
1094        else
1095                start_fsb = XFS_B_TO_FSB(mp, offset + written);
1096        end_fsb = XFS_B_TO_FSB(mp, offset + length);
1097
1098        /*
1099         * Trim delalloc blocks if they were allocated by this write and we
1100         * didn't manage to write the whole range.
1101         *
1102         * We don't need to care about racing delalloc as we hold i_mutex
1103         * across the reserve/allocate/unreserve calls. If there are delalloc
1104         * blocks in the range, they are ours.
1105         */
1106        if ((iomap->flags & IOMAP_F_NEW) && start_fsb < end_fsb) {
1107                truncate_pagecache_range(VFS_I(ip), XFS_FSB_TO_B(mp, start_fsb),
1108                                         XFS_FSB_TO_B(mp, end_fsb) - 1);
1109
1110                error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
1111                                               end_fsb - start_fsb);
1112                if (error && !XFS_FORCED_SHUTDOWN(mp)) {
1113                        xfs_alert(mp, "%s: unable to clean up ino %lld",
1114                                __func__, ip->i_ino);
1115                        return error;
1116                }
1117        }
1118
1119        return 0;
1120}
1121
1122static int
1123xfs_file_iomap_end(
1124        struct inode            *inode,
1125        loff_t                  offset,
1126        loff_t                  length,
1127        ssize_t                 written,
1128        unsigned                flags,
1129        struct iomap            *iomap)
1130{
1131        if ((flags & IOMAP_WRITE) && iomap->type == IOMAP_DELALLOC)
1132                return xfs_file_iomap_end_delalloc(XFS_I(inode), offset,
1133                                length, written, iomap);
1134        return 0;
1135}
1136
1137const struct iomap_ops xfs_iomap_ops = {
1138        .iomap_begin            = xfs_file_iomap_begin,
1139        .iomap_end              = xfs_file_iomap_end,
1140};
1141
1142static int
1143xfs_seek_iomap_begin(
1144        struct inode            *inode,
1145        loff_t                  offset,
1146        loff_t                  length,
1147        unsigned                flags,
1148        struct iomap            *iomap)
1149{
1150        struct xfs_inode        *ip = XFS_I(inode);
1151        struct xfs_mount        *mp = ip->i_mount;
1152        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
1153        xfs_fileoff_t           end_fsb = XFS_B_TO_FSB(mp, offset + length);
1154        xfs_fileoff_t           cow_fsb = NULLFILEOFF, data_fsb = NULLFILEOFF;
1155        struct xfs_iext_cursor  icur;
1156        struct xfs_bmbt_irec    imap, cmap;
1157        int                     error = 0;
1158        unsigned                lockmode;
1159
1160        if (XFS_FORCED_SHUTDOWN(mp))
1161                return -EIO;
1162
1163        lockmode = xfs_ilock_data_map_shared(ip);
1164        if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) {
1165                error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
1166                if (error)
1167                        goto out_unlock;
1168        }
1169
1170        if (xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap)) {
1171                /*
1172                 * If we found a data extent we are done.
1173                 */
1174                if (imap.br_startoff <= offset_fsb)
1175                        goto done;
1176                data_fsb = imap.br_startoff;
1177        } else {
1178                /*
1179                 * Fake a hole until the end of the file.
1180                 */
1181                data_fsb = min(XFS_B_TO_FSB(mp, offset + length),
1182                               XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes));
1183        }
1184
1185        /*
1186         * If a COW fork extent covers the hole, report it - capped to the next
1187         * data fork extent:
1188         */
1189        if (xfs_inode_has_cow_data(ip) &&
1190            xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &cmap))
1191                cow_fsb = cmap.br_startoff;
1192        if (cow_fsb != NULLFILEOFF && cow_fsb <= offset_fsb) {
1193                if (data_fsb < cow_fsb + cmap.br_blockcount)
1194                        end_fsb = min(end_fsb, data_fsb);
1195                xfs_trim_extent(&cmap, offset_fsb, end_fsb);
1196                error = xfs_bmbt_to_iomap(ip, iomap, &cmap, true);
1197                /*
1198                 * This is a COW extent, so we must probe the page cache
1199                 * because there could be dirty page cache being backed
1200                 * by this extent.
1201                 */
1202                iomap->type = IOMAP_UNWRITTEN;
1203                goto out_unlock;
1204        }
1205
1206        /*
1207         * Else report a hole, capped to the next found data or COW extent.
1208         */
1209        if (cow_fsb != NULLFILEOFF && cow_fsb < data_fsb)
1210                imap.br_blockcount = cow_fsb - offset_fsb;
1211        else
1212                imap.br_blockcount = data_fsb - offset_fsb;
1213        imap.br_startoff = offset_fsb;
1214        imap.br_startblock = HOLESTARTBLOCK;
1215        imap.br_state = XFS_EXT_NORM;
1216done:
1217        xfs_trim_extent(&imap, offset_fsb, end_fsb);
1218        error = xfs_bmbt_to_iomap(ip, iomap, &imap, false);
1219out_unlock:
1220        xfs_iunlock(ip, lockmode);
1221        return error;
1222}
1223
1224const struct iomap_ops xfs_seek_iomap_ops = {
1225        .iomap_begin            = xfs_seek_iomap_begin,
1226};
1227
1228static int
1229xfs_xattr_iomap_begin(
1230        struct inode            *inode,
1231        loff_t                  offset,
1232        loff_t                  length,
1233        unsigned                flags,
1234        struct iomap            *iomap)
1235{
1236        struct xfs_inode        *ip = XFS_I(inode);
1237        struct xfs_mount        *mp = ip->i_mount;
1238        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
1239        xfs_fileoff_t           end_fsb = XFS_B_TO_FSB(mp, offset + length);
1240        struct xfs_bmbt_irec    imap;
1241        int                     nimaps = 1, error = 0;
1242        unsigned                lockmode;
1243
1244        if (XFS_FORCED_SHUTDOWN(mp))
1245                return -EIO;
1246
1247        lockmode = xfs_ilock_attr_map_shared(ip);
1248
1249        /* if there are no attribute fork or extents, return ENOENT */
1250        if (!XFS_IFORK_Q(ip) || !ip->i_d.di_anextents) {
1251                error = -ENOENT;
1252                goto out_unlock;
1253        }
1254
1255        ASSERT(ip->i_d.di_aformat != XFS_DINODE_FMT_LOCAL);
1256        error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
1257                               &nimaps, XFS_BMAPI_ATTRFORK);
1258out_unlock:
1259        xfs_iunlock(ip, lockmode);
1260
1261        if (error)
1262                return error;
1263        ASSERT(nimaps);
1264        return xfs_bmbt_to_iomap(ip, iomap, &imap, false);
1265}
1266
1267const struct iomap_ops xfs_xattr_iomap_ops = {
1268        .iomap_begin            = xfs_xattr_iomap_begin,
1269};
1270