1// SPDX-License-Identifier: GPL-2.0+
   2/*
   3 * Copyright (C) 2016 Oracle.  All Rights Reserved.
   4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
   5 */
   6#include "xfs.h"
   7#include "xfs_fs.h"
   8#include "xfs_shared.h"
   9#include "xfs_format.h"
  10#include "xfs_log_format.h"
  11#include "xfs_trans_resv.h"
  12#include "xfs_mount.h"
  13#include "xfs_defer.h"
  14#include "xfs_inode.h"
  15#include "xfs_trans.h"
  16#include "xfs_bmap.h"
  17#include "xfs_bmap_util.h"
  18#include "xfs_trace.h"
  19#include "xfs_icache.h"
  20#include "xfs_btree.h"
  21#include "xfs_refcount_btree.h"
  22#include "xfs_refcount.h"
  23#include "xfs_bmap_btree.h"
  24#include "xfs_trans_space.h"
  25#include "xfs_bit.h"
  26#include "xfs_alloc.h"
  27#include "xfs_quota.h"
  28#include "xfs_reflink.h"
  29#include "xfs_iomap.h"
  30#include "xfs_ag.h"
  31#include "xfs_ag_resv.h"
  32
  33/*
  34 * Copy on Write of Shared Blocks
  35 *
  36 * XFS must preserve "the usual" file semantics even when two files share
  37 * the same physical blocks.  This means that a write to one file must not
  38 * alter the blocks in a different file; the way that we'll do that is
  39 * through the use of a copy-on-write mechanism.  At a high level, that
  40 * means that when we want to write to a shared block, we allocate a new
  41 * block, write the data to the new block, and if that succeeds we map the
  42 * new block into the file.
  43 *
  44 * XFS provides a "delayed allocation" mechanism that defers the allocation
  45 * of disk blocks to dirty-but-not-yet-mapped file blocks as long as
  46 * possible.  This reduces fragmentation by enabling the filesystem to ask
  47 * for bigger chunks less often, which is exactly what we want for CoW.
  48 *
  49 * The delalloc mechanism begins when the kernel wants to make a block
  50 * writable (write_begin or page_mkwrite).  If the offset is not mapped, we
  51 * create a delalloc mapping, which is a regular in-core extent, but without
  52 * a real startblock.  (For delalloc mappings, the startblock encodes both
  53 * a flag that this is a delalloc mapping, and a worst-case estimate of how
  54 * many blocks might be required to put the mapping into the BMBT.)  delalloc
  55 * mappings are a reservation against the free space in the filesystem;
  56 * adjacent mappings can also be combined into fewer larger mappings.
  57 *
  58 * As an optimization, the CoW extent size hint (cowextsz) creates
  59 * outsized aligned delalloc reservations in the hope of landing out of
  60 * order nearby CoW writes in a single extent on disk, thereby reducing
  61 * fragmentation and improving future performance.
  62 *
  63 * D: --RRRRRRSSSRRRRRRRR--- (data fork)
  64 * C: ------DDDDDDD--------- (CoW fork)
  65 *
  66 * When dirty pages are being written out (typically in writepage), the
  67 * delalloc reservations are converted into unwritten mappings by
  68 * allocating blocks and replacing the delalloc mapping with real ones.
  69 * A delalloc mapping can be replaced by several unwritten ones if the
  70 * free space is fragmented.
  71 *
  72 * D: --RRRRRRSSSRRRRRRRR---
  73 * C: ------UUUUUUU---------
  74 *
  75 * We want to adapt the delalloc mechanism for copy-on-write, since the
  76 * write paths are similar.  The first two steps (creating the reservation
  77 * and allocating the blocks) are exactly the same as delalloc except that
  78 * the mappings must be stored in a separate CoW fork because we do not want
  79 * to disturb the mapping in the data fork until we're sure that the write
  80 * succeeded.  IO completion in this case is the process of removing the old
  81 * mapping from the data fork and moving the new mapping from the CoW fork to
  82 * the data fork.  This will be discussed shortly.
  83 *
  84 * For now, unaligned directio writes will be bounced back to the page cache.
  85 * Block-aligned directio writes will use the same mechanism as buffered
  86 * writes.
  87 *
  88 * Just prior to submitting the actual disk write requests, we convert
  89 * the extents representing the range of the file actually being written
  90 * (as opposed to extra pieces created for the cowextsize hint) to real
  91 * extents.  This will become important in the next step:
  92 *
  93 * D: --RRRRRRSSSRRRRRRRR---
  94 * C: ------UUrrUUU---------
  95 *
  96 * CoW remapping must be done after the data block write completes,
  97 * because we don't want to destroy the old data fork map until we're sure
  98 * the new block has been written.  Since the new mappings are kept in a
  99 * separate fork, we can simply iterate these mappings to find the ones
 100 * that cover the file blocks that we just CoW'd.  For each extent, simply
 101 * unmap the corresponding range in the data fork, map the new range into
 102 * the data fork, and remove the extent from the CoW fork.  Because of
 103 * the presence of the cowextsize hint, however, we must be careful
 104 * only to remap the blocks that we've actually written out --  we must
 105 * never remap delalloc reservations nor CoW staging blocks that have
 106 * yet to be written.  This corresponds exactly to the real extents in
 107 * the CoW fork:
 108 *
 109 * D: --RRRRRRrrSRRRRRRRR---
 110 * C: ------UU--UUU---------
 111 *
 112 * Since the remapping operation can be applied to an arbitrary file
 113 * range, we record the need for the remap step as a flag in the ioend
 114 * instead of declaring a new IO type.  This is required for direct io
 115 * because we only have ioend for the whole dio, and we have to be able to
 116 * remember the presence of unwritten blocks and CoW blocks with a single
 117 * ioend structure.  Better yet, the more ground we can cover with one
 118 * ioend, the better.
 119 */
 120
 121/*
 122 * Given an AG extent, find the lowest-numbered run of shared blocks
 123 * within that range and return the range in fbno/flen.  If
 124 * find_end_of_shared is true, return the longest contiguous extent of
 125 * shared blocks.  If there are no shared extents, fbno and flen will
 126 * be set to NULLAGBLOCK and 0, respectively.
 127 */
 128static int
 129xfs_reflink_find_shared(
 130	struct xfs_perag	*pag,
 131	struct xfs_trans	*tp,
 
 132	xfs_agblock_t		agbno,
 133	xfs_extlen_t		aglen,
 134	xfs_agblock_t		*fbno,
 135	xfs_extlen_t		*flen,
 136	bool			find_end_of_shared)
 137{
 138	struct xfs_buf		*agbp;
 139	struct xfs_btree_cur	*cur;
 140	int			error;
 141
 142	error = xfs_alloc_read_agf(pag, tp, 0, &agbp);
 143	if (error)
 144		return error;
 
 
 145
 146	cur = xfs_refcountbt_init_cursor(pag->pag_mount, tp, agbp, pag);
 147
 148	error = xfs_refcount_find_shared(cur, agbno, aglen, fbno, flen,
 149			find_end_of_shared);
 150
 151	xfs_btree_del_cursor(cur, error);
 152
 153	xfs_trans_brelse(tp, agbp);
 154	return error;
 155}
 156
 157/*
 158 * Trim the mapping to the next block where there's a change in the
 159 * shared/unshared status.  More specifically, this means that we
 160 * find the lowest-numbered extent of shared blocks that coincides with
 161 * the given block mapping.  If the shared extent overlaps the start of
 162 * the mapping, trim the mapping to the end of the shared extent.  If
 163 * the shared region intersects the mapping, trim the mapping to the
 164 * start of the shared extent.  If there are no shared regions that
 165 * overlap, just return the original extent.
 166 */
 167int
 168xfs_reflink_trim_around_shared(
 169	struct xfs_inode	*ip,
 170	struct xfs_bmbt_irec	*irec,
 171	bool			*shared)
 172{
 173	struct xfs_mount	*mp = ip->i_mount;
 174	struct xfs_perag	*pag;
 175	xfs_agblock_t		agbno;
 176	xfs_extlen_t		aglen;
 177	xfs_agblock_t		fbno;
 178	xfs_extlen_t		flen;
 179	int			error = 0;
 180
 181	/* Holes, unwritten, and delalloc extents cannot be shared */
 182	if (!xfs_is_cow_inode(ip) || !xfs_bmap_is_written_extent(irec)) {
 183		*shared = false;
 184		return 0;
 185	}
 186
 187	trace_xfs_reflink_trim_around_shared(ip, irec);
 188
 189	pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, irec->br_startblock));
 190	agbno = XFS_FSB_TO_AGBNO(mp, irec->br_startblock);
 191	aglen = irec->br_blockcount;
 192
 193	error = xfs_reflink_find_shared(pag, NULL, agbno, aglen, &fbno, &flen,
 194			true);
 195	xfs_perag_put(pag);
 196	if (error)
 197		return error;
 198
 199	*shared = false;
 200	if (fbno == NULLAGBLOCK) {
 201		/* No shared blocks at all. */
 202		return 0;
 203	}
 204
 205	if (fbno == agbno) {
 206		/*
 207		 * The start of this extent is shared.  Truncate the
 208		 * mapping at the end of the shared region so that a
 209		 * subsequent iteration starts at the start of the
 210		 * unshared region.
 211		 */
 212		irec->br_blockcount = flen;
 213		*shared = true;
 214		return 0;
 
 
 
 
 
 
 
 
 
 215	}
 216
 217	/*
 218	 * There's a shared extent midway through this extent.
 219	 * Truncate the mapping at the start of the shared
 220	 * extent so that a subsequent iteration starts at the
 221	 * start of the shared region.
 222	 */
 223	irec->br_blockcount = fbno - agbno;
 224	return 0;
 225}
 226
 227int
 228xfs_bmap_trim_cow(
 229	struct xfs_inode	*ip,
 230	struct xfs_bmbt_irec	*imap,
 231	bool			*shared)
 232{
 233	/* We can't update any real extents in always COW mode. */
 234	if (xfs_is_always_cow_inode(ip) &&
 235	    !isnullstartblock(imap->br_startblock)) {
 236		*shared = true;
 237		return 0;
 238	}
 239
 240	/* Trim the mapping to the nearest shared extent boundary. */
 241	return xfs_reflink_trim_around_shared(ip, imap, shared);
 242}
 243
 244static int
 245xfs_reflink_convert_cow_locked(
 246	struct xfs_inode	*ip,
 247	xfs_fileoff_t		offset_fsb,
 248	xfs_filblks_t		count_fsb)
 249{
 250	struct xfs_iext_cursor	icur;
 251	struct xfs_bmbt_irec	got;
 252	struct xfs_btree_cur	*dummy_cur = NULL;
 253	int			dummy_logflags;
 254	int			error = 0;
 255
 256	if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got))
 257		return 0;
 258
 259	do {
 260		if (got.br_startoff >= offset_fsb + count_fsb)
 261			break;
 262		if (got.br_state == XFS_EXT_NORM)
 263			continue;
 264		if (WARN_ON_ONCE(isnullstartblock(got.br_startblock)))
 265			return -EIO;
 266
 267		xfs_trim_extent(&got, offset_fsb, count_fsb);
 268		if (!got.br_blockcount)
 269			continue;
 270
 271		got.br_state = XFS_EXT_NORM;
 272		error = xfs_bmap_add_extent_unwritten_real(NULL, ip,
 273				XFS_COW_FORK, &icur, &dummy_cur, &got,
 274				&dummy_logflags);
 275		if (error)
 276			return error;
 277	} while (xfs_iext_next_extent(ip->i_cowfp, &icur, &got));
 278
 279	return error;
 280}
 281
 282/* Convert all of the unwritten CoW extents in a file's range to real ones. */
 283int
 284xfs_reflink_convert_cow(
 285	struct xfs_inode	*ip,
 286	xfs_off_t		offset,
 287	xfs_off_t		count)
 288{
 289	struct xfs_mount	*mp = ip->i_mount;
 290	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);
 291	xfs_fileoff_t		end_fsb = XFS_B_TO_FSB(mp, offset + count);
 292	xfs_filblks_t		count_fsb = end_fsb - offset_fsb;
 293	int			error;
 294
 295	ASSERT(count != 0);
 296
 297	xfs_ilock(ip, XFS_ILOCK_EXCL);
 298	error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
 299	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 300	return error;
 301}
 302
 303/*
 304 * Find the extent that maps the given range in the COW fork. Even if the extent
 305 * is not shared we might have a preallocation for it in the COW fork. If so we
 306 * use it that rather than trigger a new allocation.
 307 */
 308static int
 309xfs_find_trim_cow_extent(
 310	struct xfs_inode	*ip,
 311	struct xfs_bmbt_irec	*imap,
 312	struct xfs_bmbt_irec	*cmap,
 313	bool			*shared,
 314	bool			*found)
 315{
 316	xfs_fileoff_t		offset_fsb = imap->br_startoff;
 317	xfs_filblks_t		count_fsb = imap->br_blockcount;
 318	struct xfs_iext_cursor	icur;
 
 319
 320	*found = false;
 321
 322	/*
 323	 * If we don't find an overlapping extent, trim the range we need to
 324	 * allocate to fit the hole we found.
 325	 */
 326	if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, cmap))
 327		cmap->br_startoff = offset_fsb + count_fsb;
 328	if (cmap->br_startoff > offset_fsb) {
 329		xfs_trim_extent(imap, imap->br_startoff,
 330				cmap->br_startoff - imap->br_startoff);
 331		return xfs_bmap_trim_cow(ip, imap, shared);
 332	}
 333
 334	*shared = true;
 335	if (isnullstartblock(cmap->br_startblock)) {
 336		xfs_trim_extent(imap, cmap->br_startoff, cmap->br_blockcount);
 337		return 0;
 338	}
 339
 340	/* real extent found - no need to allocate */
 341	xfs_trim_extent(cmap, offset_fsb, count_fsb);
 
 342	*found = true;
 343	return 0;
 344}
 345
 346static int
 347xfs_reflink_convert_unwritten(
 348	struct xfs_inode	*ip,
 349	struct xfs_bmbt_irec	*imap,
 350	struct xfs_bmbt_irec	*cmap,
 351	bool			convert_now)
 352{
 353	xfs_fileoff_t		offset_fsb = imap->br_startoff;
 354	xfs_filblks_t		count_fsb = imap->br_blockcount;
 355	int			error;
 356
 357	/*
 358	 * cmap might larger than imap due to cowextsize hint.
 359	 */
 360	xfs_trim_extent(cmap, offset_fsb, count_fsb);
 361
 362	/*
 363	 * COW fork extents are supposed to remain unwritten until we're ready
 364	 * to initiate a disk write.  For direct I/O we are going to write the
 365	 * data and need the conversion, but for buffered writes we're done.
 366	 */
 367	if (!convert_now || cmap->br_state == XFS_EXT_NORM)
 368		return 0;
 369
 370	trace_xfs_reflink_convert_cow(ip, cmap);
 371
 372	error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
 373	if (!error)
 374		cmap->br_state = XFS_EXT_NORM;
 375
 376	return error;
 377}
 378
 379static int
 380xfs_reflink_fill_cow_hole(
 381	struct xfs_inode	*ip,
 382	struct xfs_bmbt_irec	*imap,
 383	struct xfs_bmbt_irec	*cmap,
 384	bool			*shared,
 385	uint			*lockmode,
 386	bool			convert_now)
 387{
 388	struct xfs_mount	*mp = ip->i_mount;
 
 
 389	struct xfs_trans	*tp;
 390	xfs_filblks_t		resaligned;
 391	xfs_extlen_t		resblks;
 392	int			nimaps;
 393	int			error;
 394	bool			found;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 395
 396	resaligned = xfs_aligned_fsb_count(imap->br_startoff,
 397		imap->br_blockcount, xfs_get_cowextsz_hint(ip));
 398	resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
 399
 400	xfs_iunlock(ip, *lockmode);
 401	*lockmode = 0;
 
 
 402
 403	error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, resblks, 0,
 404			false, &tp);
 405	if (error)
 406		return error;
 407
 408	*lockmode = XFS_ILOCK_EXCL;
 
 
 409
 410	error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found);
 
 
 
 411	if (error || !*shared)
 412		goto out_trans_cancel;
 413
 414	if (found) {
 415		xfs_trans_cancel(tp);
 416		goto convert;
 417	}
 418
 
 
 
 
 
 
 
 419	/* Allocate the entire reservation as unwritten blocks. */
 420	nimaps = 1;
 421	error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount,
 422			XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0, cmap,
 423			&nimaps);
 424	if (error)
 425		goto out_trans_cancel;
 426
 427	xfs_inode_set_cowblocks_tag(ip);
 428	error = xfs_trans_commit(tp);
 429	if (error)
 430		return error;
 431
 432	/*
 433	 * Allocation succeeded but the requested range was not even partially
 434	 * satisfied?  Bail out!
 435	 */
 436	if (nimaps == 0)
 437		return -ENOSPC;
 438
 439convert:
 440	return xfs_reflink_convert_unwritten(ip, imap, cmap, convert_now);
 441
 442out_trans_cancel:
 443	xfs_trans_cancel(tp);
 444	return error;
 445}
 446
 447static int
 448xfs_reflink_fill_delalloc(
 449	struct xfs_inode	*ip,
 450	struct xfs_bmbt_irec	*imap,
 451	struct xfs_bmbt_irec	*cmap,
 452	bool			*shared,
 453	uint			*lockmode,
 454	bool			convert_now)
 455{
 456	struct xfs_mount	*mp = ip->i_mount;
 457	struct xfs_trans	*tp;
 458	int			nimaps;
 459	int			error;
 460	bool			found;
 461
 462	do {
 463		xfs_iunlock(ip, *lockmode);
 464		*lockmode = 0;
 465
 466		error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, 0, 0,
 467				false, &tp);
 468		if (error)
 469			return error;
 470
 471		*lockmode = XFS_ILOCK_EXCL;
 472
 473		error = xfs_find_trim_cow_extent(ip, imap, cmap, shared,
 474				&found);
 475		if (error || !*shared)
 476			goto out_trans_cancel;
 477
 478		if (found) {
 479			xfs_trans_cancel(tp);
 480			break;
 481		}
 482
 483		ASSERT(isnullstartblock(cmap->br_startblock) ||
 484		       cmap->br_startblock == DELAYSTARTBLOCK);
 485
 486		/*
 487		 * Replace delalloc reservation with an unwritten extent.
 488		 */
 489		nimaps = 1;
 490		error = xfs_bmapi_write(tp, ip, cmap->br_startoff,
 491				cmap->br_blockcount,
 492				XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0,
 493				cmap, &nimaps);
 494		if (error)
 495			goto out_trans_cancel;
 496
 497		xfs_inode_set_cowblocks_tag(ip);
 498		error = xfs_trans_commit(tp);
 499		if (error)
 500			return error;
 501
 502		/*
 503		 * Allocation succeeded but the requested range was not even
 504		 * partially satisfied?  Bail out!
 505		 */
 506		if (nimaps == 0)
 507			return -ENOSPC;
 508	} while (cmap->br_startoff + cmap->br_blockcount <= imap->br_startoff);
 509
 510	return xfs_reflink_convert_unwritten(ip, imap, cmap, convert_now);
 511
 
 
 
 512out_trans_cancel:
 513	xfs_trans_cancel(tp);
 514	return error;
 515}
 516
 517/* Allocate all CoW reservations covering a range of blocks in a file. */
 518int
 519xfs_reflink_allocate_cow(
 520	struct xfs_inode	*ip,
 521	struct xfs_bmbt_irec	*imap,
 522	struct xfs_bmbt_irec	*cmap,
 523	bool			*shared,
 524	uint			*lockmode,
 525	bool			convert_now)
 526{
 527	int			error;
 528	bool			found;
 529
 530	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
 531	if (!ip->i_cowfp) {
 532		ASSERT(!xfs_is_reflink_inode(ip));
 533		xfs_ifork_init_cow(ip);
 534	}
 535
 536	error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found);
 537	if (error || !*shared)
 538		return error;
 539
 540	/* CoW fork has a real extent */
 541	if (found)
 542		return xfs_reflink_convert_unwritten(ip, imap, cmap,
 543				convert_now);
 544
 545	/*
 546	 * CoW fork does not have an extent and data extent is shared.
 547	 * Allocate a real extent in the CoW fork.
 548	 */
 549	if (cmap->br_startoff > imap->br_startoff)
 550		return xfs_reflink_fill_cow_hole(ip, imap, cmap, shared,
 551				lockmode, convert_now);
 552
 553	/*
 554	 * CoW fork has a delalloc reservation. Replace it with a real extent.
 555	 * There may or may not be a data fork mapping.
 556	 */
 557	if (isnullstartblock(cmap->br_startblock) ||
 558	    cmap->br_startblock == DELAYSTARTBLOCK)
 559		return xfs_reflink_fill_delalloc(ip, imap, cmap, shared,
 560				lockmode, convert_now);
 561
 562	/* Shouldn't get here. */
 563	ASSERT(0);
 564	return -EFSCORRUPTED;
 565}
 566
 567/*
 568 * Cancel CoW reservations for some block range of an inode.
 569 *
 570 * If cancel_real is true this function cancels all COW fork extents for the
 571 * inode; if cancel_real is false, real extents are not cleared.
 572 *
 573 * Caller must have already joined the inode to the current transaction. The
 574 * inode will be joined to the transaction returned to the caller.
 575 */
 576int
 577xfs_reflink_cancel_cow_blocks(
 578	struct xfs_inode		*ip,
 579	struct xfs_trans		**tpp,
 580	xfs_fileoff_t			offset_fsb,
 581	xfs_fileoff_t			end_fsb,
 582	bool				cancel_real)
 583{
 584	struct xfs_ifork		*ifp = xfs_ifork_ptr(ip, XFS_COW_FORK);
 585	struct xfs_bmbt_irec		got, del;
 586	struct xfs_iext_cursor		icur;
 587	int				error = 0;
 588
 589	if (!xfs_inode_has_cow_data(ip))
 590		return 0;
 591	if (!xfs_iext_lookup_extent_before(ip, ifp, &end_fsb, &icur, &got))
 592		return 0;
 593
 594	/* Walk backwards until we're out of the I/O range... */
 595	while (got.br_startoff + got.br_blockcount > offset_fsb) {
 596		del = got;
 597		xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb);
 598
 599		/* Extent delete may have bumped ext forward */
 600		if (!del.br_blockcount) {
 601			xfs_iext_prev(ifp, &icur);
 602			goto next_extent;
 603		}
 604
 605		trace_xfs_reflink_cancel_cow(ip, &del);
 606
 607		if (isnullstartblock(del.br_startblock)) {
 608			error = xfs_bmap_del_extent_delay(ip, XFS_COW_FORK,
 609					&icur, &got, &del);
 610			if (error)
 611				break;
 612		} else if (del.br_state == XFS_EXT_UNWRITTEN || cancel_real) {
 613			ASSERT((*tpp)->t_highest_agno == NULLAGNUMBER);
 614
 615			/* Free the CoW orphan record. */
 616			xfs_refcount_free_cow_extent(*tpp, del.br_startblock,
 617					del.br_blockcount);
 618
 619			error = xfs_free_extent_later(*tpp, del.br_startblock,
 620					del.br_blockcount, NULL,
 621					XFS_AG_RESV_NONE, false);
 622			if (error)
 623				break;
 624
 625			/* Roll the transaction */
 626			error = xfs_defer_finish(tpp);
 627			if (error)
 628				break;
 629
 630			/* Remove the mapping from the CoW fork. */
 631			xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
 632
 633			/* Remove the quota reservation */
 634			error = xfs_quota_unreserve_blkres(ip,
 635					del.br_blockcount);
 
 636			if (error)
 637				break;
 638		} else {
 639			/* Didn't do anything, push cursor back. */
 640			xfs_iext_prev(ifp, &icur);
 641		}
 642next_extent:
 643		if (!xfs_iext_get_extent(ifp, &icur, &got))
 644			break;
 645	}
 646
 647	/* clear tag if cow fork is emptied */
 648	if (!ifp->if_bytes)
 649		xfs_inode_clear_cowblocks_tag(ip);
 650	return error;
 651}
 652
 653/*
 654 * Cancel CoW reservations for some byte range of an inode.
 655 *
 656 * If cancel_real is true this function cancels all COW fork extents for the
 657 * inode; if cancel_real is false, real extents are not cleared.
 658 */
 659int
 660xfs_reflink_cancel_cow_range(
 661	struct xfs_inode	*ip,
 662	xfs_off_t		offset,
 663	xfs_off_t		count,
 664	bool			cancel_real)
 665{
 666	struct xfs_trans	*tp;
 667	xfs_fileoff_t		offset_fsb;
 668	xfs_fileoff_t		end_fsb;
 669	int			error;
 670
 671	trace_xfs_reflink_cancel_cow_range(ip, offset, count);
 672	ASSERT(ip->i_cowfp);
 673
 674	offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
 675	if (count == NULLFILEOFF)
 676		end_fsb = NULLFILEOFF;
 677	else
 678		end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
 679
 680	/* Start a rolling transaction to remove the mappings */
 681	error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
 682			0, 0, 0, &tp);
 683	if (error)
 684		goto out;
 685
 686	xfs_ilock(ip, XFS_ILOCK_EXCL);
 687	xfs_trans_ijoin(tp, ip, 0);
 688
 689	/* Scrape out the old CoW reservations */
 690	error = xfs_reflink_cancel_cow_blocks(ip, &tp, offset_fsb, end_fsb,
 691			cancel_real);
 692	if (error)
 693		goto out_cancel;
 694
 695	error = xfs_trans_commit(tp);
 696
 697	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 698	return error;
 699
 700out_cancel:
 701	xfs_trans_cancel(tp);
 702	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 703out:
 704	trace_xfs_reflink_cancel_cow_range_error(ip, error, _RET_IP_);
 705	return error;
 706}
 707
 708/*
 709 * Remap part of the CoW fork into the data fork.
 710 *
 711 * We aim to remap the range starting at @offset_fsb and ending at @end_fsb
 712 * into the data fork; this function will remap what it can (at the end of the
 713 * range) and update @end_fsb appropriately.  Each remap gets its own
 714 * transaction because we can end up merging and splitting bmbt blocks for
 715 * every remap operation and we'd like to keep the block reservation
 716 * requirements as low as possible.
 717 */
 718STATIC int
 719xfs_reflink_end_cow_extent(
 720	struct xfs_inode	*ip,
 721	xfs_fileoff_t		*offset_fsb,
 722	xfs_fileoff_t		end_fsb)
 723{
 
 724	struct xfs_iext_cursor	icur;
 725	struct xfs_bmbt_irec	got, del, data;
 726	struct xfs_mount	*mp = ip->i_mount;
 727	struct xfs_trans	*tp;
 728	struct xfs_ifork	*ifp = xfs_ifork_ptr(ip, XFS_COW_FORK);
 
 729	unsigned int		resblks;
 730	int			nmaps;
 731	int			error;
 732
 733	/* No COW extents?  That's easy! */
 734	if (ifp->if_bytes == 0) {
 735		*offset_fsb = end_fsb;
 736		return 0;
 737	}
 738
 739	resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
 740	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
 741			XFS_TRANS_RESERVE, &tp);
 742	if (error)
 743		return error;
 744
 745	/*
 746	 * Lock the inode.  We have to ijoin without automatic unlock because
 747	 * the lead transaction is the refcountbt record deletion; the data
 748	 * fork update follows as a deferred log item.
 749	 */
 750	xfs_ilock(ip, XFS_ILOCK_EXCL);
 751	xfs_trans_ijoin(tp, ip, 0);
 752
 753	error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
 754			XFS_IEXT_REFLINK_END_COW_CNT);
 755	if (error == -EFBIG)
 756		error = xfs_iext_count_upgrade(tp, ip,
 757				XFS_IEXT_REFLINK_END_COW_CNT);
 758	if (error)
 759		goto out_cancel;
 760
 761	/*
 762	 * In case of racing, overlapping AIO writes no COW extents might be
 763	 * left by the time I/O completes for the loser of the race.  In that
 764	 * case we are done.
 765	 */
 766	if (!xfs_iext_lookup_extent(ip, ifp, *offset_fsb, &icur, &got) ||
 767	    got.br_startoff >= end_fsb) {
 768		*offset_fsb = end_fsb;
 769		goto out_cancel;
 770	}
 771
 772	/*
 773	 * Only remap real extents that contain data.  With AIO, speculative
 774	 * preallocations can leak into the range we are called upon, and we
 775	 * need to skip them.  Preserve @got for the eventual CoW fork
 776	 * deletion; from now on @del represents the mapping that we're
 777	 * actually remapping.
 778	 */
 779	while (!xfs_bmap_is_written_extent(&got)) {
 780		if (!xfs_iext_next_extent(ifp, &icur, &got) ||
 781		    got.br_startoff >= end_fsb) {
 782			*offset_fsb = end_fsb;
 783			goto out_cancel;
 784		}
 785	}
 786	del = got;
 787	xfs_trim_extent(&del, *offset_fsb, end_fsb - *offset_fsb);
 788
 789	/* Grab the corresponding mapping in the data fork. */
 790	nmaps = 1;
 791	error = xfs_bmapi_read(ip, del.br_startoff, del.br_blockcount, &data,
 792			&nmaps, 0);
 793	if (error)
 794		goto out_cancel;
 795
 796	/* We can only remap the smaller of the two extent sizes. */
 797	data.br_blockcount = min(data.br_blockcount, del.br_blockcount);
 798	del.br_blockcount = data.br_blockcount;
 799
 800	trace_xfs_reflink_cow_remap_from(ip, &del);
 801	trace_xfs_reflink_cow_remap_to(ip, &data);
 
 
 
 
 
 
 
 802
 803	if (xfs_bmap_is_real_extent(&data)) {
 804		/*
 805		 * If the extent we're remapping is backed by storage (written
 806		 * or not), unmap the extent and drop its refcount.
 807		 */
 808		xfs_bmap_unmap_extent(tp, ip, &data);
 809		xfs_refcount_decrease_extent(tp, &data);
 810		xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT,
 811				-data.br_blockcount);
 812	} else if (data.br_startblock == DELAYSTARTBLOCK) {
 813		int		done;
 814
 815		/*
 816		 * If the extent we're remapping is a delalloc reservation,
 817		 * we can use the regular bunmapi function to release the
 818		 * incore state.  Dropping the delalloc reservation takes care
 819		 * of the quota reservation for us.
 820		 */
 821		error = xfs_bunmapi(NULL, ip, data.br_startoff,
 822				data.br_blockcount, 0, 1, &done);
 823		if (error)
 824			goto out_cancel;
 825		ASSERT(done);
 826	}
 827
 828	/* Free the CoW orphan record. */
 829	xfs_refcount_free_cow_extent(tp, del.br_startblock, del.br_blockcount);
 830
 831	/* Map the new blocks into the data fork. */
 832	xfs_bmap_map_extent(tp, ip, &del);
 833
 834	/* Charge this new data fork mapping to the on-disk quota. */
 835	xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_DELBCOUNT,
 836			(long)del.br_blockcount);
 837
 838	/* Remove the mapping from the CoW fork. */
 839	xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
 840
 841	error = xfs_trans_commit(tp);
 842	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 843	if (error)
 844		return error;
 845
 846	/* Update the caller about how much progress we made. */
 847	*offset_fsb = del.br_startoff + del.br_blockcount;
 848	return 0;
 849
 850out_cancel:
 851	xfs_trans_cancel(tp);
 852	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 853	return error;
 854}
 855
 856/*
 857 * Remap parts of a file's data fork after a successful CoW.
 858 */
 859int
 860xfs_reflink_end_cow(
 861	struct xfs_inode		*ip,
 862	xfs_off_t			offset,
 863	xfs_off_t			count)
 864{
 865	xfs_fileoff_t			offset_fsb;
 866	xfs_fileoff_t			end_fsb;
 867	int				error = 0;
 868
 869	trace_xfs_reflink_end_cow(ip, offset, count);
 870
 871	offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
 872	end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
 873
 874	/*
 875	 * Walk forwards until we've remapped the I/O range.  The loop function
 876	 * repeatedly cycles the ILOCK to allocate one transaction per remapped
 877	 * extent.
 878	 *
 879	 * If we're being called by writeback then the pages will still
 880	 * have PageWriteback set, which prevents races with reflink remapping
 881	 * and truncate.  Reflink remapping prevents races with writeback by
 882	 * taking the iolock and mmaplock before flushing the pages and
 883	 * remapping, which means there won't be any further writeback or page
 884	 * cache dirtying until the reflink completes.
 885	 *
 886	 * We should never have two threads issuing writeback for the same file
 887	 * region.  There are also have post-eof checks in the writeback
 888	 * preparation code so that we don't bother writing out pages that are
 889	 * about to be truncated.
 890	 *
 891	 * If we're being called as part of directio write completion, the dio
 892	 * count is still elevated, which reflink and truncate will wait for.
 893	 * Reflink remapping takes the iolock and mmaplock and waits for
 894	 * pending dio to finish, which should prevent any directio until the
 895	 * remap completes.  Multiple concurrent directio writes to the same
 896	 * region are handled by end_cow processing only occurring for the
 897	 * threads which succeed; the outcome of multiple overlapping direct
 898	 * writes is not well defined anyway.
 899	 *
 900	 * It's possible that a buffered write and a direct write could collide
 901	 * here (the buffered write stumbles in after the dio flushes and
 902	 * invalidates the page cache and immediately queues writeback), but we
 903	 * have never supported this 100%.  If either disk write succeeds the
 904	 * blocks will be remapped.
 905	 */
 906	while (end_fsb > offset_fsb && !error)
 907		error = xfs_reflink_end_cow_extent(ip, &offset_fsb, end_fsb);
 908
 909	if (error)
 910		trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
 911	return error;
 912}
 913
 914/*
 915 * Free all CoW staging blocks that are still referenced by the ondisk refcount
 916 * metadata.  The ondisk metadata does not track which inode created the
 917 * staging extent, so callers must ensure that there are no cached inodes with
 918 * live CoW staging extents.
 919 */
 920int
 921xfs_reflink_recover_cow(
 922	struct xfs_mount	*mp)
 923{
 924	struct xfs_perag	*pag;
 925	xfs_agnumber_t		agno;
 926	int			error = 0;
 927
 928	if (!xfs_has_reflink(mp))
 929		return 0;
 930
 931	for_each_perag(mp, agno, pag) {
 932		error = xfs_refcount_recover_cow_leftovers(mp, pag);
 933		if (error) {
 934			xfs_perag_rele(pag);
 935			break;
 936		}
 937	}
 938
 939	return error;
 940}
 941
 942/*
 943 * Reflinking (Block) Ranges of Two Files Together
 944 *
 945 * First, ensure that the reflink flag is set on both inodes.  The flag is an
 946 * optimization to avoid unnecessary refcount btree lookups in the write path.
 947 *
 948 * Now we can iteratively remap the range of extents (and holes) in src to the
 949 * corresponding ranges in dest.  Let drange and srange denote the ranges of
 950 * logical blocks in dest and src touched by the reflink operation.
 951 *
 952 * While the length of drange is greater than zero,
 953 *    - Read src's bmbt at the start of srange ("imap")
 954 *    - If imap doesn't exist, make imap appear to start at the end of srange
 955 *      with zero length.
 956 *    - If imap starts before srange, advance imap to start at srange.
 957 *    - If imap goes beyond srange, truncate imap to end at the end of srange.
 958 *    - Punch (imap start - srange start + imap len) blocks from dest at
 959 *      offset (drange start).
 960 *    - If imap points to a real range of pblks,
 961 *         > Increase the refcount of the imap's pblks
 962 *         > Map imap's pblks into dest at the offset
 963 *           (drange start + imap start - srange start)
 964 *    - Advance drange and srange by (imap start - srange start + imap len)
 965 *
 966 * Finally, if the reflink made dest longer, update both the in-core and
 967 * on-disk file sizes.
 968 *
 969 * ASCII Art Demonstration:
 970 *
 971 * Let's say we want to reflink this source file:
 972 *
 973 * ----SSSSSSS-SSSSS----SSSSSS (src file)
 974 *   <-------------------->
 975 *
 976 * into this destination file:
 977 *
 978 * --DDDDDDDDDDDDDDDDDDD--DDD (dest file)
 979 *        <-------------------->
 980 * '-' means a hole, and 'S' and 'D' are written blocks in the src and dest.
 981 * Observe that the range has different logical offsets in either file.
 982 *
 983 * Consider that the first extent in the source file doesn't line up with our
 984 * reflink range.  Unmapping  and remapping are separate operations, so we can
 985 * unmap more blocks from the destination file than we remap.
 986 *
 987 * ----SSSSSSS-SSSSS----SSSSSS
 988 *   <------->
 989 * --DDDDD---------DDDDD--DDD
 990 *        <------->
 991 *
 992 * Now remap the source extent into the destination file:
 993 *
 994 * ----SSSSSSS-SSSSS----SSSSSS
 995 *   <------->
 996 * --DDDDD--SSSSSSSDDDDD--DDD
 997 *        <------->
 998 *
 999 * Do likewise with the second hole and extent in our range.  Holes in the
1000 * unmap range don't affect our operation.
1001 *
1002 * ----SSSSSSS-SSSSS----SSSSSS
1003 *            <---->
1004 * --DDDDD--SSSSSSS-SSSSS-DDD
1005 *                 <---->
1006 *
1007 * Finally, unmap and remap part of the third extent.  This will increase the
1008 * size of the destination file.
1009 *
1010 * ----SSSSSSS-SSSSS----SSSSSS
1011 *                  <----->
1012 * --DDDDD--SSSSSSS-SSSSS----SSS
1013 *                       <----->
1014 *
1015 * Once we update the destination file's i_size, we're done.
1016 */
1017
1018/*
1019 * Ensure the reflink bit is set in both inodes.
1020 */
1021STATIC int
1022xfs_reflink_set_inode_flag(
1023	struct xfs_inode	*src,
1024	struct xfs_inode	*dest)
1025{
1026	struct xfs_mount	*mp = src->i_mount;
1027	int			error;
1028	struct xfs_trans	*tp;
1029
1030	if (xfs_is_reflink_inode(src) && xfs_is_reflink_inode(dest))
1031		return 0;
1032
1033	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
1034	if (error)
1035		goto out_error;
1036
1037	/* Lock both files against IO */
1038	if (src->i_ino == dest->i_ino)
1039		xfs_ilock(src, XFS_ILOCK_EXCL);
1040	else
1041		xfs_lock_two_inodes(src, XFS_ILOCK_EXCL, dest, XFS_ILOCK_EXCL);
1042
1043	if (!xfs_is_reflink_inode(src)) {
1044		trace_xfs_reflink_set_inode_flag(src);
1045		xfs_trans_ijoin(tp, src, XFS_ILOCK_EXCL);
1046		src->i_diflags2 |= XFS_DIFLAG2_REFLINK;
1047		xfs_trans_log_inode(tp, src, XFS_ILOG_CORE);
1048		xfs_ifork_init_cow(src);
1049	} else
1050		xfs_iunlock(src, XFS_ILOCK_EXCL);
1051
1052	if (src->i_ino == dest->i_ino)
1053		goto commit_flags;
1054
1055	if (!xfs_is_reflink_inode(dest)) {
1056		trace_xfs_reflink_set_inode_flag(dest);
1057		xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
1058		dest->i_diflags2 |= XFS_DIFLAG2_REFLINK;
1059		xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
1060		xfs_ifork_init_cow(dest);
1061	} else
1062		xfs_iunlock(dest, XFS_ILOCK_EXCL);
1063
1064commit_flags:
1065	error = xfs_trans_commit(tp);
1066	if (error)
1067		goto out_error;
1068	return error;
1069
1070out_error:
1071	trace_xfs_reflink_set_inode_flag_error(dest, error, _RET_IP_);
1072	return error;
1073}
1074
1075/*
1076 * Update destination inode size & cowextsize hint, if necessary.
1077 */
1078int
1079xfs_reflink_update_dest(
1080	struct xfs_inode	*dest,
1081	xfs_off_t		newlen,
1082	xfs_extlen_t		cowextsize,
1083	unsigned int		remap_flags)
1084{
1085	struct xfs_mount	*mp = dest->i_mount;
1086	struct xfs_trans	*tp;
1087	int			error;
1088
1089	if (newlen <= i_size_read(VFS_I(dest)) && cowextsize == 0)
1090		return 0;
1091
1092	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
1093	if (error)
1094		goto out_error;
1095
1096	xfs_ilock(dest, XFS_ILOCK_EXCL);
1097	xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
1098
1099	if (newlen > i_size_read(VFS_I(dest))) {
1100		trace_xfs_reflink_update_inode_size(dest, newlen);
1101		i_size_write(VFS_I(dest), newlen);
1102		dest->i_disk_size = newlen;
1103	}
1104
1105	if (cowextsize) {
1106		dest->i_cowextsize = cowextsize;
1107		dest->i_diflags2 |= XFS_DIFLAG2_COWEXTSIZE;
1108	}
1109
1110	xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
1111
1112	error = xfs_trans_commit(tp);
1113	if (error)
1114		goto out_error;
1115	return error;
1116
1117out_error:
1118	trace_xfs_reflink_update_inode_size_error(dest, error, _RET_IP_);
1119	return error;
1120}
1121
1122/*
1123 * Do we have enough reserve in this AG to handle a reflink?  The refcount
1124 * btree already reserved all the space it needs, but the rmap btree can grow
1125 * infinitely, so we won't allow more reflinks when the AG is down to the
1126 * btree reserves.
1127 */
1128static int
1129xfs_reflink_ag_has_free_space(
1130	struct xfs_mount	*mp,
1131	xfs_agnumber_t		agno)
1132{
1133	struct xfs_perag	*pag;
1134	int			error = 0;
1135
1136	if (!xfs_has_rmapbt(mp))
1137		return 0;
1138
1139	pag = xfs_perag_get(mp, agno);
1140	if (xfs_ag_resv_critical(pag, XFS_AG_RESV_RMAPBT) ||
1141	    xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA))
1142		error = -ENOSPC;
1143	xfs_perag_put(pag);
1144	return error;
1145}
1146
1147/*
1148 * Remap the given extent into the file.  The dmap blockcount will be set to
1149 * the number of blocks that were actually remapped.
 
1150 */
1151STATIC int
1152xfs_reflink_remap_extent(
1153	struct xfs_inode	*ip,
1154	struct xfs_bmbt_irec	*dmap,
 
1155	xfs_off_t		new_isize)
1156{
1157	struct xfs_bmbt_irec	smap;
1158	struct xfs_mount	*mp = ip->i_mount;
 
1159	struct xfs_trans	*tp;
1160	xfs_off_t		newlen;
1161	int64_t			qdelta = 0;
1162	unsigned int		resblks;
1163	bool			quota_reserved = true;
1164	bool			smap_real;
1165	bool			dmap_written = xfs_bmap_is_written_extent(dmap);
1166	int			iext_delta = 0;
1167	int			nimaps;
1168	int			error;
1169
1170	/*
1171	 * Start a rolling transaction to switch the mappings.
1172	 *
1173	 * Adding a written extent to the extent map can cause a bmbt split,
1174	 * and removing a mapped extent from the extent can cause a bmbt split.
1175	 * The two operations cannot both cause a split since they operate on
1176	 * the same index in the bmap btree, so we only need a reservation for
1177	 * one bmbt split if either thing is happening.  However, we haven't
1178	 * locked the inode yet, so we reserve assuming this is the case.
1179	 *
1180	 * The first allocation call tries to reserve enough space to handle
1181	 * mapping dmap into a sparse part of the file plus the bmbt split.  We
1182	 * haven't locked the inode or read the existing mapping yet, so we do
1183	 * not know for sure that we need the space.  This should succeed most
1184	 * of the time.
1185	 *
1186	 * If the first attempt fails, try again but reserving only enough
1187	 * space to handle a bmbt split.  This is the hard minimum requirement,
1188	 * and we revisit quota reservations later when we know more about what
1189	 * we're remapping.
1190	 */
1191	resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
1192	error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
1193			resblks + dmap->br_blockcount, 0, false, &tp);
1194	if (error == -EDQUOT || error == -ENOSPC) {
1195		quota_reserved = false;
1196		error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
1197				resblks, 0, false, &tp);
1198	}
1199	if (error)
1200		goto out;
1201
1202	/*
1203	 * Read what's currently mapped in the destination file into smap.
1204	 * If smap isn't a hole, we will have to remove it before we can add
1205	 * dmap to the destination file.
1206	 */
1207	nimaps = 1;
1208	error = xfs_bmapi_read(ip, dmap->br_startoff, dmap->br_blockcount,
1209			&smap, &nimaps, 0);
1210	if (error)
1211		goto out_cancel;
1212	ASSERT(nimaps == 1 && smap.br_startoff == dmap->br_startoff);
1213	smap_real = xfs_bmap_is_real_extent(&smap);
1214
1215	/*
1216	 * We can only remap as many blocks as the smaller of the two extent
1217	 * maps, because we can only remap one extent at a time.
1218	 */
1219	dmap->br_blockcount = min(dmap->br_blockcount, smap.br_blockcount);
1220	ASSERT(dmap->br_blockcount == smap.br_blockcount);
1221
1222	trace_xfs_reflink_remap_extent_dest(ip, &smap);
1223
1224	/*
1225	 * Two extents mapped to the same physical block must not have
1226	 * different states; that's filesystem corruption.  Move on to the next
1227	 * extent if they're both holes or both the same physical extent.
1228	 */
1229	if (dmap->br_startblock == smap.br_startblock) {
1230		if (dmap->br_state != smap.br_state)
1231			error = -EFSCORRUPTED;
1232		goto out_cancel;
1233	}
1234
1235	/* If both extents are unwritten, leave them alone. */
1236	if (dmap->br_state == XFS_EXT_UNWRITTEN &&
1237	    smap.br_state == XFS_EXT_UNWRITTEN)
1238		goto out_cancel;
1239
1240	/* No reflinking if the AG of the dest mapping is low on space. */
1241	if (dmap_written) {
1242		error = xfs_reflink_ag_has_free_space(mp,
1243				XFS_FSB_TO_AGNO(mp, dmap->br_startblock));
1244		if (error)
1245			goto out_cancel;
1246	}
1247
1248	/*
1249	 * Increase quota reservation if we think the quota block counter for
1250	 * this file could increase.
1251	 *
1252	 * If we are mapping a written extent into the file, we need to have
1253	 * enough quota block count reservation to handle the blocks in that
1254	 * extent.  We log only the delta to the quota block counts, so if the
1255	 * extent we're unmapping also has blocks allocated to it, we don't
1256	 * need a quota reservation for the extent itself.
1257	 *
1258	 * Note that if we're replacing a delalloc reservation with a written
1259	 * extent, we have to take the full quota reservation because removing
1260	 * the delalloc reservation gives the block count back to the quota
1261	 * count.  This is suboptimal, but the VFS flushed the dest range
1262	 * before we started.  That should have removed all the delalloc
1263	 * reservations, but we code defensively.
1264	 *
1265	 * xfs_trans_alloc_inode above already tried to grab an even larger
1266	 * quota reservation, and kicked off a blockgc scan if it couldn't.
1267	 * If we can't get a potentially smaller quota reservation now, we're
1268	 * done.
1269	 */
1270	if (!quota_reserved && !smap_real && dmap_written) {
1271		error = xfs_trans_reserve_quota_nblks(tp, ip,
1272				dmap->br_blockcount, 0, false);
1273		if (error)
1274			goto out_cancel;
1275	}
1276
1277	if (smap_real)
1278		++iext_delta;
 
 
 
 
 
 
1279
1280	if (dmap_written)
1281		++iext_delta;
 
1282
1283	error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK, iext_delta);
1284	if (error == -EFBIG)
1285		error = xfs_iext_count_upgrade(tp, ip, iext_delta);
1286	if (error)
1287		goto out_cancel;
1288
1289	if (smap_real) {
1290		/*
1291		 * If the extent we're unmapping is backed by storage (written
1292		 * or not), unmap the extent and drop its refcount.
1293		 */
1294		xfs_bmap_unmap_extent(tp, ip, &smap);
1295		xfs_refcount_decrease_extent(tp, &smap);
1296		qdelta -= smap.br_blockcount;
1297	} else if (smap.br_startblock == DELAYSTARTBLOCK) {
1298		int		done;
1299
1300		/*
1301		 * If the extent we're unmapping is a delalloc reservation,
1302		 * we can use the regular bunmapi function to release the
1303		 * incore state.  Dropping the delalloc reservation takes care
1304		 * of the quota reservation for us.
1305		 */
1306		error = xfs_bunmapi(NULL, ip, smap.br_startoff,
1307				smap.br_blockcount, 0, 1, &done);
1308		if (error)
1309			goto out_cancel;
1310		ASSERT(done);
1311	}
1312
1313	/*
1314	 * If the extent we're sharing is backed by written storage, increase
1315	 * its refcount and map it into the file.
1316	 */
1317	if (dmap_written) {
1318		xfs_refcount_increase_extent(tp, dmap);
1319		xfs_bmap_map_extent(tp, ip, dmap);
1320		qdelta += dmap->br_blockcount;
1321	}
1322
1323	xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT, qdelta);
 
 
 
 
 
 
 
 
 
1324
1325	/* Update dest isize if needed. */
1326	newlen = XFS_FSB_TO_B(mp, dmap->br_startoff + dmap->br_blockcount);
1327	newlen = min_t(xfs_off_t, newlen, new_isize);
1328	if (newlen > i_size_read(VFS_I(ip))) {
1329		trace_xfs_reflink_update_inode_size(ip, newlen);
1330		i_size_write(VFS_I(ip), newlen);
1331		ip->i_disk_size = newlen;
1332		xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
1333	}
1334
1335	/* Commit everything and unlock. */
1336	error = xfs_trans_commit(tp);
1337	goto out_unlock;
 
 
 
1338
1339out_cancel:
1340	xfs_trans_cancel(tp);
1341out_unlock:
1342	xfs_iunlock(ip, XFS_ILOCK_EXCL);
1343out:
1344	if (error)
1345		trace_xfs_reflink_remap_extent_error(ip, error, _RET_IP_);
1346	return error;
1347}
1348
1349/* Remap a range of one file to the other. */
 
 
1350int
1351xfs_reflink_remap_blocks(
1352	struct xfs_inode	*src,
1353	loff_t			pos_in,
1354	struct xfs_inode	*dest,
1355	loff_t			pos_out,
1356	loff_t			remap_len,
1357	loff_t			*remapped)
1358{
1359	struct xfs_bmbt_irec	imap;
1360	struct xfs_mount	*mp = src->i_mount;
1361	xfs_fileoff_t		srcoff = XFS_B_TO_FSBT(mp, pos_in);
1362	xfs_fileoff_t		destoff = XFS_B_TO_FSBT(mp, pos_out);
1363	xfs_filblks_t		len;
 
1364	xfs_filblks_t		remapped_len = 0;
1365	xfs_off_t		new_isize = pos_out + remap_len;
1366	int			nimaps;
1367	int			error = 0;
1368
1369	len = min_t(xfs_filblks_t, XFS_B_TO_FSB(mp, remap_len),
1370			XFS_MAX_FILEOFF);
1371
1372	trace_xfs_reflink_remap_blocks(src, srcoff, len, dest, destoff);
 
 
 
1373
1374	while (len > 0) {
1375		unsigned int	lock_mode;
1376
1377		/* Read extent from the source file */
1378		nimaps = 1;
1379		lock_mode = xfs_ilock_data_map_shared(src);
1380		error = xfs_bmapi_read(src, srcoff, len, &imap, &nimaps, 0);
1381		xfs_iunlock(src, lock_mode);
1382		if (error)
1383			break;
1384		/*
1385		 * The caller supposedly flushed all dirty pages in the source
1386		 * file range, which means that writeback should have allocated
1387		 * or deleted all delalloc reservations in that range.  If we
1388		 * find one, that's a good sign that something is seriously
1389		 * wrong here.
1390		 */
1391		ASSERT(nimaps == 1 && imap.br_startoff == srcoff);
1392		if (imap.br_startblock == DELAYSTARTBLOCK) {
1393			ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
1394			error = -EFSCORRUPTED;
1395			break;
1396		}
1397
1398		trace_xfs_reflink_remap_extent_src(src, &imap);
 
1399
1400		/* Remap into the destination file at the given offset. */
1401		imap.br_startoff = destoff;
1402		error = xfs_reflink_remap_extent(dest, &imap, new_isize);
 
 
 
 
1403		if (error)
1404			break;
1405
1406		if (fatal_signal_pending(current)) {
1407			error = -EINTR;
1408			break;
1409		}
1410
1411		/* Advance drange/srange */
1412		srcoff += imap.br_blockcount;
1413		destoff += imap.br_blockcount;
1414		len -= imap.br_blockcount;
1415		remapped_len += imap.br_blockcount;
1416	}
1417
1418	if (error)
1419		trace_xfs_reflink_remap_blocks_error(dest, error, _RET_IP_);
1420	*remapped = min_t(loff_t, remap_len,
1421			  XFS_FSB_TO_B(src->i_mount, remapped_len));
1422	return error;
1423}
1424
1425/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1426 * If we're reflinking to a point past the destination file's EOF, we must
1427 * zero any speculative post-EOF preallocations that sit between the old EOF
1428 * and the destination file offset.
1429 */
1430static int
1431xfs_reflink_zero_posteof(
1432	struct xfs_inode	*ip,
1433	loff_t			pos)
1434{
1435	loff_t			isize = i_size_read(VFS_I(ip));
1436
1437	if (pos <= isize)
1438		return 0;
1439
1440	trace_xfs_zero_eof(ip, isize, pos - isize);
1441	return xfs_zero_range(ip, isize, pos - isize, NULL);
 
1442}
1443
1444/*
1445 * Prepare two files for range cloning.  Upon a successful return both inodes
1446 * will have the iolock and mmaplock held, the page cache of the out file will
1447 * be truncated, and any leases on the out file will have been broken.  This
1448 * function borrows heavily from xfs_file_aio_write_checks.
1449 *
1450 * The VFS allows partial EOF blocks to "match" for dedupe even though it hasn't
1451 * checked that the bytes beyond EOF physically match. Hence we cannot use the
1452 * EOF block in the source dedupe range because it's not a complete block match,
1453 * hence can introduce a corruption into the file that has it's block replaced.
1454 *
1455 * In similar fashion, the VFS file cloning also allows partial EOF blocks to be
1456 * "block aligned" for the purposes of cloning entire files.  However, if the
1457 * source file range includes the EOF block and it lands within the existing EOF
1458 * of the destination file, then we can expose stale data from beyond the source
1459 * file EOF in the destination file.
1460 *
1461 * XFS doesn't support partial block sharing, so in both cases we have check
1462 * these cases ourselves. For dedupe, we can simply round the length to dedupe
1463 * down to the previous whole block and ignore the partial EOF block. While this
1464 * means we can't dedupe the last block of a file, this is an acceptible
1465 * tradeoff for simplicity on implementation.
1466 *
1467 * For cloning, we want to share the partial EOF block if it is also the new EOF
1468 * block of the destination file. If the partial EOF block lies inside the
1469 * existing destination EOF, then we have to abort the clone to avoid exposing
1470 * stale data in the destination file. Hence we reject these clone attempts with
1471 * -EINVAL in this case.
1472 */
1473int
1474xfs_reflink_remap_prep(
1475	struct file		*file_in,
1476	loff_t			pos_in,
1477	struct file		*file_out,
1478	loff_t			pos_out,
1479	loff_t			*len,
1480	unsigned int		remap_flags)
1481{
1482	struct inode		*inode_in = file_inode(file_in);
1483	struct xfs_inode	*src = XFS_I(inode_in);
1484	struct inode		*inode_out = file_inode(file_out);
1485	struct xfs_inode	*dest = XFS_I(inode_out);
1486	int			ret;
 
1487
1488	/* Lock both files against IO */
1489	ret = xfs_ilock2_io_mmap(src, dest);
1490	if (ret)
1491		return ret;
 
 
 
 
 
1492
1493	/* Check file eligibility and prepare for block sharing. */
1494	ret = -EINVAL;
1495	/* Don't reflink realtime inodes */
1496	if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
1497		goto out_unlock;
1498
1499	/* Don't share DAX file data with non-DAX file. */
1500	if (IS_DAX(inode_in) != IS_DAX(inode_out))
1501		goto out_unlock;
1502
1503	if (!IS_DAX(inode_in))
1504		ret = generic_remap_file_range_prep(file_in, pos_in, file_out,
1505				pos_out, len, remap_flags);
1506	else
1507		ret = dax_remap_file_range_prep(file_in, pos_in, file_out,
1508				pos_out, len, remap_flags, &xfs_read_iomap_ops);
1509	if (ret || *len == 0)
1510		goto out_unlock;
1511
1512	/* Attach dquots to dest inode before changing block map */
1513	ret = xfs_qm_dqattach(dest);
1514	if (ret)
1515		goto out_unlock;
1516
1517	/*
1518	 * Zero existing post-eof speculative preallocations in the destination
1519	 * file.
1520	 */
1521	ret = xfs_reflink_zero_posteof(dest, pos_out);
1522	if (ret)
1523		goto out_unlock;
1524
1525	/* Set flags and remap blocks. */
1526	ret = xfs_reflink_set_inode_flag(src, dest);
1527	if (ret)
1528		goto out_unlock;
1529
1530	/*
1531	 * If pos_out > EOF, we may have dirtied blocks between EOF and
1532	 * pos_out. In that case, we need to extend the flush and unmap to cover
1533	 * from EOF to the end of the copy length.
1534	 */
1535	if (pos_out > XFS_ISIZE(dest)) {
1536		loff_t	flen = *len + (pos_out - XFS_ISIZE(dest));
1537		ret = xfs_flush_unmap_range(dest, XFS_ISIZE(dest), flen);
1538	} else {
1539		ret = xfs_flush_unmap_range(dest, pos_out, *len);
1540	}
1541	if (ret)
1542		goto out_unlock;
1543
1544	xfs_iflags_set(src, XFS_IREMAPPING);
1545	if (inode_in != inode_out)
1546		xfs_ilock_demote(src, XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL);
1547
1548	return 0;
1549out_unlock:
1550	xfs_iunlock2_io_mmap(src, dest);
1551	return ret;
1552}
1553
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1554/* Does this inode need the reflink flag? */
1555int
1556xfs_reflink_inode_has_shared_extents(
1557	struct xfs_trans		*tp,
1558	struct xfs_inode		*ip,
1559	bool				*has_shared)
1560{
1561	struct xfs_bmbt_irec		got;
1562	struct xfs_mount		*mp = ip->i_mount;
1563	struct xfs_ifork		*ifp;
 
 
 
 
 
1564	struct xfs_iext_cursor		icur;
1565	bool				found;
1566	int				error;
1567
1568	ifp = xfs_ifork_ptr(ip, XFS_DATA_FORK);
1569	error = xfs_iread_extents(tp, ip, XFS_DATA_FORK);
1570	if (error)
1571		return error;
 
 
1572
1573	*has_shared = false;
1574	found = xfs_iext_lookup_extent(ip, ifp, 0, &icur, &got);
1575	while (found) {
1576		struct xfs_perag	*pag;
1577		xfs_agblock_t		agbno;
1578		xfs_extlen_t		aglen;
1579		xfs_agblock_t		rbno;
1580		xfs_extlen_t		rlen;
1581
1582		if (isnullstartblock(got.br_startblock) ||
1583		    got.br_state != XFS_EXT_NORM)
1584			goto next;
1585
1586		pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, got.br_startblock));
1587		agbno = XFS_FSB_TO_AGBNO(mp, got.br_startblock);
1588		aglen = got.br_blockcount;
1589		error = xfs_reflink_find_shared(pag, tp, agbno, aglen,
 
1590				&rbno, &rlen, false);
1591		xfs_perag_put(pag);
1592		if (error)
1593			return error;
1594
1595		/* Is there still a shared block here? */
1596		if (rbno != NULLAGBLOCK) {
1597			*has_shared = true;
1598			return 0;
1599		}
1600next:
1601		found = xfs_iext_next_extent(ifp, &icur, &got);
1602	}
1603
1604	return 0;
1605}
1606
1607/*
1608 * Clear the inode reflink flag if there are no shared extents.
1609 *
1610 * The caller is responsible for joining the inode to the transaction passed in.
1611 * The inode will be joined to the transaction that is returned to the caller.
1612 */
1613int
1614xfs_reflink_clear_inode_flag(
1615	struct xfs_inode	*ip,
1616	struct xfs_trans	**tpp)
1617{
1618	bool			needs_flag;
1619	int			error = 0;
1620
1621	ASSERT(xfs_is_reflink_inode(ip));
1622
1623	error = xfs_reflink_inode_has_shared_extents(*tpp, ip, &needs_flag);
1624	if (error || needs_flag)
1625		return error;
1626
1627	/*
1628	 * We didn't find any shared blocks so turn off the reflink flag.
1629	 * First, get rid of any leftover CoW mappings.
1630	 */
1631	error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, XFS_MAX_FILEOFF,
1632			true);
1633	if (error)
1634		return error;
1635
1636	/* Clear the inode flag. */
1637	trace_xfs_reflink_unset_inode_flag(ip);
1638	ip->i_diflags2 &= ~XFS_DIFLAG2_REFLINK;
1639	xfs_inode_clear_cowblocks_tag(ip);
1640	xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
1641
1642	return error;
1643}
1644
1645/*
1646 * Clear the inode reflink flag if there are no shared extents and the size
1647 * hasn't changed.
1648 */
1649STATIC int
1650xfs_reflink_try_clear_inode_flag(
1651	struct xfs_inode	*ip)
1652{
1653	struct xfs_mount	*mp = ip->i_mount;
1654	struct xfs_trans	*tp;
1655	int			error = 0;
1656
1657	/* Start a rolling transaction to remove the mappings */
1658	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1659	if (error)
1660		return error;
1661
1662	xfs_ilock(ip, XFS_ILOCK_EXCL);
1663	xfs_trans_ijoin(tp, ip, 0);
1664
1665	error = xfs_reflink_clear_inode_flag(ip, &tp);
1666	if (error)
1667		goto cancel;
1668
1669	error = xfs_trans_commit(tp);
1670	if (error)
1671		goto out;
1672
1673	xfs_iunlock(ip, XFS_ILOCK_EXCL);
1674	return 0;
1675cancel:
1676	xfs_trans_cancel(tp);
1677out:
1678	xfs_iunlock(ip, XFS_ILOCK_EXCL);
1679	return error;
1680}
1681
1682/*
1683 * Pre-COW all shared blocks within a given byte range of a file and turn off
1684 * the reflink flag if we unshare all of the file's blocks.
1685 */
1686int
1687xfs_reflink_unshare(
1688	struct xfs_inode	*ip,
1689	xfs_off_t		offset,
1690	xfs_off_t		len)
1691{
1692	struct inode		*inode = VFS_I(ip);
 
 
 
1693	int			error;
1694
1695	if (!xfs_is_reflink_inode(ip))
1696		return 0;
1697
1698	trace_xfs_reflink_unshare(ip, offset, len);
1699
1700	inode_dio_wait(inode);
1701
1702	if (IS_DAX(inode))
1703		error = dax_file_unshare(inode, offset, len,
1704				&xfs_dax_write_iomap_ops);
1705	else
1706		error = iomap_file_unshare(inode, offset, len,
1707				&xfs_buffered_write_iomap_ops);
1708	if (error)
1709		goto out;
 
1710
1711	error = filemap_write_and_wait_range(inode->i_mapping, offset,
1712			offset + len - 1);
1713	if (error)
1714		goto out;
1715
1716	/* Turn off the reflink flag if possible. */
1717	error = xfs_reflink_try_clear_inode_flag(ip);
1718	if (error)
1719		goto out;
 
1720	return 0;
1721
 
 
1722out:
1723	trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
1724	return error;
1725}