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#include "xfs_health.h"
  33
  34/*
  35 * Copy on Write of Shared Blocks
  36 *
  37 * XFS must preserve "the usual" file semantics even when two files share
  38 * the same physical blocks.  This means that a write to one file must not
  39 * alter the blocks in a different file; the way that we'll do that is
  40 * through the use of a copy-on-write mechanism.  At a high level, that
  41 * means that when we want to write to a shared block, we allocate a new
  42 * block, write the data to the new block, and if that succeeds we map the
  43 * new block into the file.
  44 *
  45 * XFS provides a "delayed allocation" mechanism that defers the allocation
  46 * of disk blocks to dirty-but-not-yet-mapped file blocks as long as
  47 * possible.  This reduces fragmentation by enabling the filesystem to ask
  48 * for bigger chunks less often, which is exactly what we want for CoW.
  49 *
  50 * The delalloc mechanism begins when the kernel wants to make a block
  51 * writable (write_begin or page_mkwrite).  If the offset is not mapped, we
  52 * create a delalloc mapping, which is a regular in-core extent, but without
  53 * a real startblock.  (For delalloc mappings, the startblock encodes both
  54 * a flag that this is a delalloc mapping, and a worst-case estimate of how
  55 * many blocks might be required to put the mapping into the BMBT.)  delalloc
  56 * mappings are a reservation against the free space in the filesystem;
  57 * adjacent mappings can also be combined into fewer larger mappings.
  58 *
  59 * As an optimization, the CoW extent size hint (cowextsz) creates
  60 * outsized aligned delalloc reservations in the hope of landing out of
  61 * order nearby CoW writes in a single extent on disk, thereby reducing
  62 * fragmentation and improving future performance.
  63 *
  64 * D: --RRRRRRSSSRRRRRRRR--- (data fork)
  65 * C: ------DDDDDDD--------- (CoW fork)
  66 *
  67 * When dirty pages are being written out (typically in writepage), the
  68 * delalloc reservations are converted into unwritten mappings by
  69 * allocating blocks and replacing the delalloc mapping with real ones.
  70 * A delalloc mapping can be replaced by several unwritten ones if the
  71 * free space is fragmented.
  72 *
  73 * D: --RRRRRRSSSRRRRRRRR---
  74 * C: ------UUUUUUU---------
  75 *
  76 * We want to adapt the delalloc mechanism for copy-on-write, since the
  77 * write paths are similar.  The first two steps (creating the reservation
  78 * and allocating the blocks) are exactly the same as delalloc except that
  79 * the mappings must be stored in a separate CoW fork because we do not want
  80 * to disturb the mapping in the data fork until we're sure that the write
  81 * succeeded.  IO completion in this case is the process of removing the old
  82 * mapping from the data fork and moving the new mapping from the CoW fork to
  83 * the data fork.  This will be discussed shortly.
  84 *
  85 * For now, unaligned directio writes will be bounced back to the page cache.
  86 * Block-aligned directio writes will use the same mechanism as buffered
  87 * writes.
  88 *
  89 * Just prior to submitting the actual disk write requests, we convert
  90 * the extents representing the range of the file actually being written
  91 * (as opposed to extra pieces created for the cowextsize hint) to real
  92 * extents.  This will become important in the next step:
  93 *
  94 * D: --RRRRRRSSSRRRRRRRR---
  95 * C: ------UUrrUUU---------
  96 *
  97 * CoW remapping must be done after the data block write completes,
  98 * because we don't want to destroy the old data fork map until we're sure
  99 * the new block has been written.  Since the new mappings are kept in a
 100 * separate fork, we can simply iterate these mappings to find the ones
 101 * that cover the file blocks that we just CoW'd.  For each extent, simply
 102 * unmap the corresponding range in the data fork, map the new range into
 103 * the data fork, and remove the extent from the CoW fork.  Because of
 104 * the presence of the cowextsize hint, however, we must be careful
 105 * only to remap the blocks that we've actually written out --  we must
 106 * never remap delalloc reservations nor CoW staging blocks that have
 107 * yet to be written.  This corresponds exactly to the real extents in
 108 * the CoW fork:
 109 *
 110 * D: --RRRRRRrrSRRRRRRRR---
 111 * C: ------UU--UUU---------
 112 *
 113 * Since the remapping operation can be applied to an arbitrary file
 114 * range, we record the need for the remap step as a flag in the ioend
 115 * instead of declaring a new IO type.  This is required for direct io
 116 * because we only have ioend for the whole dio, and we have to be able to
 117 * remember the presence of unwritten blocks and CoW blocks with a single
 118 * ioend structure.  Better yet, the more ground we can cover with one
 119 * ioend, the better.
 120 */
 121
 122/*
 123 * Given an AG extent, find the lowest-numbered run of shared blocks
 124 * within that range and return the range in fbno/flen.  If
 125 * find_end_of_shared is true, return the longest contiguous extent of
 126 * shared blocks.  If there are no shared extents, fbno and flen will
 127 * be set to NULLAGBLOCK and 0, respectively.
 128 */
 129static int
 130xfs_reflink_find_shared(
 131	struct xfs_perag	*pag,
 132	struct xfs_trans	*tp,
 133	xfs_agblock_t		agbno,
 134	xfs_extlen_t		aglen,
 135	xfs_agblock_t		*fbno,
 136	xfs_extlen_t		*flen,
 137	bool			find_end_of_shared)
 138{
 139	struct xfs_buf		*agbp;
 140	struct xfs_btree_cur	*cur;
 141	int			error;
 142
 143	error = xfs_alloc_read_agf(pag, tp, 0, &agbp);
 144	if (error)
 145		return error;
 146
 147	cur = xfs_refcountbt_init_cursor(pag->pag_mount, tp, agbp, pag);
 148
 149	error = xfs_refcount_find_shared(cur, agbno, aglen, fbno, flen,
 150			find_end_of_shared);
 151
 152	xfs_btree_del_cursor(cur, error);
 153
 154	xfs_trans_brelse(tp, agbp);
 155	return error;
 156}
 157
 158/*
 159 * Trim the mapping to the next block where there's a change in the
 160 * shared/unshared status.  More specifically, this means that we
 161 * find the lowest-numbered extent of shared blocks that coincides with
 162 * the given block mapping.  If the shared extent overlaps the start of
 163 * the mapping, trim the mapping to the end of the shared extent.  If
 164 * the shared region intersects the mapping, trim the mapping to the
 165 * start of the shared extent.  If there are no shared regions that
 166 * overlap, just return the original extent.
 167 */
 168int
 169xfs_reflink_trim_around_shared(
 170	struct xfs_inode	*ip,
 171	struct xfs_bmbt_irec	*irec,
 172	bool			*shared)
 173{
 174	struct xfs_mount	*mp = ip->i_mount;
 175	struct xfs_perag	*pag;
 176	xfs_agblock_t		agbno;
 177	xfs_extlen_t		aglen;
 178	xfs_agblock_t		fbno;
 179	xfs_extlen_t		flen;
 180	int			error = 0;
 181
 182	/* Holes, unwritten, and delalloc extents cannot be shared */
 183	if (!xfs_is_cow_inode(ip) || !xfs_bmap_is_written_extent(irec)) {
 184		*shared = false;
 185		return 0;
 186	}
 187
 188	trace_xfs_reflink_trim_around_shared(ip, irec);
 189
 190	pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, irec->br_startblock));
 191	agbno = XFS_FSB_TO_AGBNO(mp, irec->br_startblock);
 192	aglen = irec->br_blockcount;
 193
 194	error = xfs_reflink_find_shared(pag, NULL, agbno, aglen, &fbno, &flen,
 195			true);
 196	xfs_perag_put(pag);
 197	if (error)
 198		return error;
 199
 200	*shared = false;
 201	if (fbno == NULLAGBLOCK) {
 202		/* No shared blocks at all. */
 203		return 0;
 204	}
 205
 206	if (fbno == agbno) {
 207		/*
 208		 * The start of this extent is shared.  Truncate the
 209		 * mapping at the end of the shared region so that a
 210		 * subsequent iteration starts at the start of the
 211		 * unshared region.
 212		 */
 213		irec->br_blockcount = flen;
 214		*shared = true;
 215		return 0;
 216	}
 217
 218	/*
 219	 * There's a shared extent midway through this extent.
 220	 * Truncate the mapping at the start of the shared
 221	 * extent so that a subsequent iteration starts at the
 222	 * start of the shared region.
 223	 */
 224	irec->br_blockcount = fbno - agbno;
 225	return 0;
 226}
 227
 228int
 229xfs_bmap_trim_cow(
 230	struct xfs_inode	*ip,
 231	struct xfs_bmbt_irec	*imap,
 232	bool			*shared)
 233{
 234	/* We can't update any real extents in always COW mode. */
 235	if (xfs_is_always_cow_inode(ip) &&
 236	    !isnullstartblock(imap->br_startblock)) {
 237		*shared = true;
 238		return 0;
 239	}
 240
 241	/* Trim the mapping to the nearest shared extent boundary. */
 242	return xfs_reflink_trim_around_shared(ip, imap, shared);
 243}
 244
 245static int
 246xfs_reflink_convert_cow_locked(
 247	struct xfs_inode	*ip,
 248	xfs_fileoff_t		offset_fsb,
 249	xfs_filblks_t		count_fsb)
 250{
 251	struct xfs_iext_cursor	icur;
 252	struct xfs_bmbt_irec	got;
 253	struct xfs_btree_cur	*dummy_cur = NULL;
 254	int			dummy_logflags;
 255	int			error = 0;
 256
 257	if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got))
 258		return 0;
 259
 260	do {
 261		if (got.br_startoff >= offset_fsb + count_fsb)
 262			break;
 263		if (got.br_state == XFS_EXT_NORM)
 264			continue;
 265		if (WARN_ON_ONCE(isnullstartblock(got.br_startblock)))
 266			return -EIO;
 267
 268		xfs_trim_extent(&got, offset_fsb, count_fsb);
 269		if (!got.br_blockcount)
 270			continue;
 271
 272		got.br_state = XFS_EXT_NORM;
 273		error = xfs_bmap_add_extent_unwritten_real(NULL, ip,
 274				XFS_COW_FORK, &icur, &dummy_cur, &got,
 275				&dummy_logflags);
 276		if (error)
 277			return error;
 278	} while (xfs_iext_next_extent(ip->i_cowfp, &icur, &got));
 279
 280	return error;
 281}
 282
 283/* Convert all of the unwritten CoW extents in a file's range to real ones. */
 284int
 285xfs_reflink_convert_cow(
 286	struct xfs_inode	*ip,
 287	xfs_off_t		offset,
 288	xfs_off_t		count)
 289{
 290	struct xfs_mount	*mp = ip->i_mount;
 291	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);
 292	xfs_fileoff_t		end_fsb = XFS_B_TO_FSB(mp, offset + count);
 293	xfs_filblks_t		count_fsb = end_fsb - offset_fsb;
 294	int			error;
 295
 296	ASSERT(count != 0);
 297
 298	xfs_ilock(ip, XFS_ILOCK_EXCL);
 299	error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
 300	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 301	return error;
 302}
 303
 304/*
 305 * Find the extent that maps the given range in the COW fork. Even if the extent
 306 * is not shared we might have a preallocation for it in the COW fork. If so we
 307 * use it that rather than trigger a new allocation.
 308 */
 309static int
 310xfs_find_trim_cow_extent(
 311	struct xfs_inode	*ip,
 312	struct xfs_bmbt_irec	*imap,
 313	struct xfs_bmbt_irec	*cmap,
 314	bool			*shared,
 315	bool			*found)
 316{
 317	xfs_fileoff_t		offset_fsb = imap->br_startoff;
 318	xfs_filblks_t		count_fsb = imap->br_blockcount;
 319	struct xfs_iext_cursor	icur;
 320
 321	*found = false;
 322
 323	/*
 324	 * If we don't find an overlapping extent, trim the range we need to
 325	 * allocate to fit the hole we found.
 326	 */
 327	if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, cmap))
 328		cmap->br_startoff = offset_fsb + count_fsb;
 329	if (cmap->br_startoff > offset_fsb) {
 330		xfs_trim_extent(imap, imap->br_startoff,
 331				cmap->br_startoff - imap->br_startoff);
 332		return xfs_bmap_trim_cow(ip, imap, shared);
 333	}
 334
 335	*shared = true;
 336	if (isnullstartblock(cmap->br_startblock)) {
 337		xfs_trim_extent(imap, cmap->br_startoff, cmap->br_blockcount);
 338		return 0;
 339	}
 340
 341	/* real extent found - no need to allocate */
 342	xfs_trim_extent(cmap, offset_fsb, count_fsb);
 343	*found = true;
 344	return 0;
 345}
 346
 347static int
 348xfs_reflink_convert_unwritten(
 349	struct xfs_inode	*ip,
 350	struct xfs_bmbt_irec	*imap,
 351	struct xfs_bmbt_irec	*cmap,
 352	bool			convert_now)
 353{
 354	xfs_fileoff_t		offset_fsb = imap->br_startoff;
 355	xfs_filblks_t		count_fsb = imap->br_blockcount;
 356	int			error;
 357
 358	/*
 359	 * cmap might larger than imap due to cowextsize hint.
 360	 */
 361	xfs_trim_extent(cmap, offset_fsb, count_fsb);
 362
 363	/*
 364	 * COW fork extents are supposed to remain unwritten until we're ready
 365	 * to initiate a disk write.  For direct I/O we are going to write the
 366	 * data and need the conversion, but for buffered writes we're done.
 367	 */
 368	if (!convert_now || cmap->br_state == XFS_EXT_NORM)
 369		return 0;
 370
 371	trace_xfs_reflink_convert_cow(ip, cmap);
 372
 373	error = xfs_reflink_convert_cow_locked(ip, offset_fsb, count_fsb);
 374	if (!error)
 375		cmap->br_state = XFS_EXT_NORM;
 376
 377	return error;
 378}
 379
 380static int
 381xfs_reflink_fill_cow_hole(
 382	struct xfs_inode	*ip,
 383	struct xfs_bmbt_irec	*imap,
 384	struct xfs_bmbt_irec	*cmap,
 385	bool			*shared,
 386	uint			*lockmode,
 387	bool			convert_now)
 388{
 389	struct xfs_mount	*mp = ip->i_mount;
 390	struct xfs_trans	*tp;
 391	xfs_filblks_t		resaligned;
 392	xfs_extlen_t		resblks;
 393	int			nimaps;
 394	int			error;
 395	bool			found;
 396
 397	resaligned = xfs_aligned_fsb_count(imap->br_startoff,
 398		imap->br_blockcount, xfs_get_cowextsz_hint(ip));
 399	resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
 400
 401	xfs_iunlock(ip, *lockmode);
 402	*lockmode = 0;
 403
 404	error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, resblks, 0,
 405			false, &tp);
 406	if (error)
 407		return error;
 408
 409	*lockmode = XFS_ILOCK_EXCL;
 410
 411	error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found);
 412	if (error || !*shared)
 413		goto out_trans_cancel;
 414
 415	if (found) {
 416		xfs_trans_cancel(tp);
 417		goto convert;
 418	}
 419
 420	/* Allocate the entire reservation as unwritten blocks. */
 421	nimaps = 1;
 422	error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount,
 423			XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0, cmap,
 424			&nimaps);
 425	if (error)
 426		goto out_trans_cancel;
 427
 428	xfs_inode_set_cowblocks_tag(ip);
 429	error = xfs_trans_commit(tp);
 430	if (error)
 431		return error;
 432
 433	/*
 434	 * Allocation succeeded but the requested range was not even partially
 435	 * satisfied?  Bail out!
 436	 */
 437	if (nimaps == 0)
 438		return -ENOSPC;
 439
 440convert:
 441	return xfs_reflink_convert_unwritten(ip, imap, cmap, convert_now);
 442
 443out_trans_cancel:
 444	xfs_trans_cancel(tp);
 445	return error;
 446}
 447
 448static int
 449xfs_reflink_fill_delalloc(
 450	struct xfs_inode	*ip,
 451	struct xfs_bmbt_irec	*imap,
 452	struct xfs_bmbt_irec	*cmap,
 453	bool			*shared,
 454	uint			*lockmode,
 455	bool			convert_now)
 456{
 457	struct xfs_mount	*mp = ip->i_mount;
 458	struct xfs_trans	*tp;
 459	int			nimaps;
 460	int			error;
 461	bool			found;
 462
 463	do {
 464		xfs_iunlock(ip, *lockmode);
 465		*lockmode = 0;
 466
 467		error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, 0, 0,
 468				false, &tp);
 469		if (error)
 470			return error;
 471
 472		*lockmode = XFS_ILOCK_EXCL;
 473
 474		error = xfs_find_trim_cow_extent(ip, imap, cmap, shared,
 475				&found);
 476		if (error || !*shared)
 477			goto out_trans_cancel;
 478
 479		if (found) {
 480			xfs_trans_cancel(tp);
 481			break;
 482		}
 483
 484		ASSERT(isnullstartblock(cmap->br_startblock) ||
 485		       cmap->br_startblock == DELAYSTARTBLOCK);
 486
 487		/*
 488		 * Replace delalloc reservation with an unwritten extent.
 489		 */
 490		nimaps = 1;
 491		error = xfs_bmapi_write(tp, ip, cmap->br_startoff,
 492				cmap->br_blockcount,
 493				XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, 0,
 494				cmap, &nimaps);
 495		if (error)
 496			goto out_trans_cancel;
 497
 498		xfs_inode_set_cowblocks_tag(ip);
 499		error = xfs_trans_commit(tp);
 500		if (error)
 501			return error;
 502
 503		/*
 504		 * Allocation succeeded but the requested range was not even
 505		 * partially satisfied?  Bail out!
 506		 */
 507		if (nimaps == 0)
 508			return -ENOSPC;
 509	} while (cmap->br_startoff + cmap->br_blockcount <= imap->br_startoff);
 510
 511	return xfs_reflink_convert_unwritten(ip, imap, cmap, convert_now);
 512
 513out_trans_cancel:
 514	xfs_trans_cancel(tp);
 515	return error;
 516}
 517
 518/* Allocate all CoW reservations covering a range of blocks in a file. */
 519int
 520xfs_reflink_allocate_cow(
 521	struct xfs_inode	*ip,
 522	struct xfs_bmbt_irec	*imap,
 523	struct xfs_bmbt_irec	*cmap,
 524	bool			*shared,
 525	uint			*lockmode,
 526	bool			convert_now)
 527{
 528	int			error;
 529	bool			found;
 530
 531	xfs_assert_ilocked(ip, XFS_ILOCK_EXCL);
 532	if (!ip->i_cowfp) {
 533		ASSERT(!xfs_is_reflink_inode(ip));
 534		xfs_ifork_init_cow(ip);
 535	}
 536
 537	error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found);
 538	if (error || !*shared)
 539		return error;
 540
 541	/* CoW fork has a real extent */
 542	if (found)
 543		return xfs_reflink_convert_unwritten(ip, imap, cmap,
 544				convert_now);
 545
 546	/*
 547	 * CoW fork does not have an extent and data extent is shared.
 548	 * Allocate a real extent in the CoW fork.
 549	 */
 550	if (cmap->br_startoff > imap->br_startoff)
 551		return xfs_reflink_fill_cow_hole(ip, imap, cmap, shared,
 552				lockmode, convert_now);
 553
 554	/*
 555	 * CoW fork has a delalloc reservation. Replace it with a real extent.
 556	 * There may or may not be a data fork mapping.
 557	 */
 558	if (isnullstartblock(cmap->br_startblock) ||
 559	    cmap->br_startblock == DELAYSTARTBLOCK)
 560		return xfs_reflink_fill_delalloc(ip, imap, cmap, shared,
 561				lockmode, convert_now);
 562
 563	/* Shouldn't get here. */
 564	ASSERT(0);
 565	return -EFSCORRUPTED;
 566}
 567
 568/*
 569 * Cancel CoW reservations for some block range of an inode.
 570 *
 571 * If cancel_real is true this function cancels all COW fork extents for the
 572 * inode; if cancel_real is false, real extents are not cleared.
 573 *
 574 * Caller must have already joined the inode to the current transaction. The
 575 * inode will be joined to the transaction returned to the caller.
 576 */
 577int
 578xfs_reflink_cancel_cow_blocks(
 579	struct xfs_inode		*ip,
 580	struct xfs_trans		**tpp,
 581	xfs_fileoff_t			offset_fsb,
 582	xfs_fileoff_t			end_fsb,
 583	bool				cancel_real)
 584{
 585	struct xfs_ifork		*ifp = xfs_ifork_ptr(ip, XFS_COW_FORK);
 586	struct xfs_bmbt_irec		got, del;
 587	struct xfs_iext_cursor		icur;
 588	int				error = 0;
 589
 590	if (!xfs_inode_has_cow_data(ip))
 591		return 0;
 592	if (!xfs_iext_lookup_extent_before(ip, ifp, &end_fsb, &icur, &got))
 593		return 0;
 594
 595	/* Walk backwards until we're out of the I/O range... */
 596	while (got.br_startoff + got.br_blockcount > offset_fsb) {
 597		del = got;
 598		xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb);
 599
 600		/* Extent delete may have bumped ext forward */
 601		if (!del.br_blockcount) {
 602			xfs_iext_prev(ifp, &icur);
 603			goto next_extent;
 604		}
 605
 606		trace_xfs_reflink_cancel_cow(ip, &del);
 607
 608		if (isnullstartblock(del.br_startblock)) {
 609			error = xfs_bmap_del_extent_delay(ip, XFS_COW_FORK,
 610					&icur, &got, &del);
 611			if (error)
 612				break;
 613		} else if (del.br_state == XFS_EXT_UNWRITTEN || cancel_real) {
 614			ASSERT((*tpp)->t_highest_agno == NULLAGNUMBER);
 615
 616			/* Free the CoW orphan record. */
 617			xfs_refcount_free_cow_extent(*tpp, del.br_startblock,
 618					del.br_blockcount);
 619
 620			error = xfs_free_extent_later(*tpp, del.br_startblock,
 621					del.br_blockcount, NULL,
 622					XFS_AG_RESV_NONE, false);
 623			if (error)
 624				break;
 625
 626			/* Roll the transaction */
 627			error = xfs_defer_finish(tpp);
 628			if (error)
 629				break;
 630
 631			/* Remove the mapping from the CoW fork. */
 632			xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
 633
 634			/* Remove the quota reservation */
 635			error = xfs_quota_unreserve_blkres(ip,
 636					del.br_blockcount);
 637			if (error)
 638				break;
 639		} else {
 640			/* Didn't do anything, push cursor back. */
 641			xfs_iext_prev(ifp, &icur);
 642		}
 643next_extent:
 644		if (!xfs_iext_get_extent(ifp, &icur, &got))
 645			break;
 646	}
 647
 648	/* clear tag if cow fork is emptied */
 649	if (!ifp->if_bytes)
 650		xfs_inode_clear_cowblocks_tag(ip);
 651	return error;
 652}
 653
 654/*
 655 * Cancel CoW reservations for some byte range of an inode.
 656 *
 657 * If cancel_real is true this function cancels all COW fork extents for the
 658 * inode; if cancel_real is false, real extents are not cleared.
 659 */
 660int
 661xfs_reflink_cancel_cow_range(
 662	struct xfs_inode	*ip,
 663	xfs_off_t		offset,
 664	xfs_off_t		count,
 665	bool			cancel_real)
 666{
 667	struct xfs_trans	*tp;
 668	xfs_fileoff_t		offset_fsb;
 669	xfs_fileoff_t		end_fsb;
 670	int			error;
 671
 672	trace_xfs_reflink_cancel_cow_range(ip, offset, count);
 673	ASSERT(ip->i_cowfp);
 674
 675	offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
 676	if (count == NULLFILEOFF)
 677		end_fsb = NULLFILEOFF;
 678	else
 679		end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
 680
 681	/* Start a rolling transaction to remove the mappings */
 682	error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
 683			0, 0, 0, &tp);
 684	if (error)
 685		goto out;
 686
 687	xfs_ilock(ip, XFS_ILOCK_EXCL);
 688	xfs_trans_ijoin(tp, ip, 0);
 689
 690	/* Scrape out the old CoW reservations */
 691	error = xfs_reflink_cancel_cow_blocks(ip, &tp, offset_fsb, end_fsb,
 692			cancel_real);
 693	if (error)
 694		goto out_cancel;
 695
 696	error = xfs_trans_commit(tp);
 697
 698	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 699	return error;
 700
 701out_cancel:
 702	xfs_trans_cancel(tp);
 703	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 704out:
 705	trace_xfs_reflink_cancel_cow_range_error(ip, error, _RET_IP_);
 706	return error;
 707}
 708
 709/*
 710 * Remap part of the CoW fork into the data fork.
 711 *
 712 * We aim to remap the range starting at @offset_fsb and ending at @end_fsb
 713 * into the data fork; this function will remap what it can (at the end of the
 714 * range) and update @end_fsb appropriately.  Each remap gets its own
 715 * transaction because we can end up merging and splitting bmbt blocks for
 716 * every remap operation and we'd like to keep the block reservation
 717 * requirements as low as possible.
 718 */
 719STATIC int
 720xfs_reflink_end_cow_extent(
 721	struct xfs_inode	*ip,
 722	xfs_fileoff_t		*offset_fsb,
 723	xfs_fileoff_t		end_fsb)
 724{
 725	struct xfs_iext_cursor	icur;
 726	struct xfs_bmbt_irec	got, del, data;
 727	struct xfs_mount	*mp = ip->i_mount;
 728	struct xfs_trans	*tp;
 729	struct xfs_ifork	*ifp = xfs_ifork_ptr(ip, XFS_COW_FORK);
 730	unsigned int		resblks;
 731	int			nmaps;
 732	int			error;
 733
 734	/* No COW extents?  That's easy! */
 735	if (ifp->if_bytes == 0) {
 736		*offset_fsb = end_fsb;
 737		return 0;
 738	}
 739
 740	resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
 741	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
 742			XFS_TRANS_RESERVE, &tp);
 743	if (error)
 744		return error;
 745
 746	/*
 747	 * Lock the inode.  We have to ijoin without automatic unlock because
 748	 * the lead transaction is the refcountbt record deletion; the data
 749	 * fork update follows as a deferred log item.
 750	 */
 751	xfs_ilock(ip, XFS_ILOCK_EXCL);
 752	xfs_trans_ijoin(tp, ip, 0);
 753
 754	error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
 755			XFS_IEXT_REFLINK_END_COW_CNT);
 756	if (error == -EFBIG)
 757		error = xfs_iext_count_upgrade(tp, ip,
 758				XFS_IEXT_REFLINK_END_COW_CNT);
 759	if (error)
 760		goto out_cancel;
 761
 762	/*
 763	 * In case of racing, overlapping AIO writes no COW extents might be
 764	 * left by the time I/O completes for the loser of the race.  In that
 765	 * case we are done.
 766	 */
 767	if (!xfs_iext_lookup_extent(ip, ifp, *offset_fsb, &icur, &got) ||
 768	    got.br_startoff >= end_fsb) {
 769		*offset_fsb = end_fsb;
 770		goto out_cancel;
 771	}
 772
 773	/*
 774	 * Only remap real extents that contain data.  With AIO, speculative
 775	 * preallocations can leak into the range we are called upon, and we
 776	 * need to skip them.  Preserve @got for the eventual CoW fork
 777	 * deletion; from now on @del represents the mapping that we're
 778	 * actually remapping.
 779	 */
 780	while (!xfs_bmap_is_written_extent(&got)) {
 781		if (!xfs_iext_next_extent(ifp, &icur, &got) ||
 782		    got.br_startoff >= end_fsb) {
 783			*offset_fsb = end_fsb;
 784			goto out_cancel;
 785		}
 786	}
 787	del = got;
 788	xfs_trim_extent(&del, *offset_fsb, end_fsb - *offset_fsb);
 789
 
 
 
 
 
 790	/* Grab the corresponding mapping in the data fork. */
 791	nmaps = 1;
 792	error = xfs_bmapi_read(ip, del.br_startoff, del.br_blockcount, &data,
 793			&nmaps, 0);
 794	if (error)
 795		goto out_cancel;
 796
 797	/* We can only remap the smaller of the two extent sizes. */
 798	data.br_blockcount = min(data.br_blockcount, del.br_blockcount);
 799	del.br_blockcount = data.br_blockcount;
 800
 801	trace_xfs_reflink_cow_remap_from(ip, &del);
 802	trace_xfs_reflink_cow_remap_to(ip, &data);
 803
 804	if (xfs_bmap_is_real_extent(&data)) {
 805		/*
 806		 * If the extent we're remapping is backed by storage (written
 807		 * or not), unmap the extent and drop its refcount.
 808		 */
 809		xfs_bmap_unmap_extent(tp, ip, XFS_DATA_FORK, &data);
 810		xfs_refcount_decrease_extent(tp, &data);
 811		xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT,
 812				-data.br_blockcount);
 813	} else if (data.br_startblock == DELAYSTARTBLOCK) {
 814		int		done;
 815
 816		/*
 817		 * If the extent we're remapping is a delalloc reservation,
 818		 * we can use the regular bunmapi function to release the
 819		 * incore state.  Dropping the delalloc reservation takes care
 820		 * of the quota reservation for us.
 821		 */
 822		error = xfs_bunmapi(NULL, ip, data.br_startoff,
 823				data.br_blockcount, 0, 1, &done);
 824		if (error)
 825			goto out_cancel;
 826		ASSERT(done);
 827	}
 828
 829	/* Free the CoW orphan record. */
 830	xfs_refcount_free_cow_extent(tp, del.br_startblock, del.br_blockcount);
 831
 832	/* Map the new blocks into the data fork. */
 833	xfs_bmap_map_extent(tp, ip, XFS_DATA_FORK, &del);
 834
 835	/* Charge this new data fork mapping to the on-disk quota. */
 836	xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_DELBCOUNT,
 837			(long)del.br_blockcount);
 838
 839	/* Remove the mapping from the CoW fork. */
 840	xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
 841
 842	error = xfs_trans_commit(tp);
 843	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 844	if (error)
 845		return error;
 846
 847	/* Update the caller about how much progress we made. */
 848	*offset_fsb = del.br_startoff + del.br_blockcount;
 849	return 0;
 850
 851out_cancel:
 852	xfs_trans_cancel(tp);
 853	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 854	return error;
 855}
 856
 857/*
 858 * Remap parts of a file's data fork after a successful CoW.
 859 */
 860int
 861xfs_reflink_end_cow(
 862	struct xfs_inode		*ip,
 863	xfs_off_t			offset,
 864	xfs_off_t			count)
 865{
 866	xfs_fileoff_t			offset_fsb;
 867	xfs_fileoff_t			end_fsb;
 868	int				error = 0;
 869
 870	trace_xfs_reflink_end_cow(ip, offset, count);
 871
 872	offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
 873	end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
 874
 875	/*
 876	 * Walk forwards until we've remapped the I/O range.  The loop function
 877	 * repeatedly cycles the ILOCK to allocate one transaction per remapped
 878	 * extent.
 879	 *
 880	 * If we're being called by writeback then the pages will still
 881	 * have PageWriteback set, which prevents races with reflink remapping
 882	 * and truncate.  Reflink remapping prevents races with writeback by
 883	 * taking the iolock and mmaplock before flushing the pages and
 884	 * remapping, which means there won't be any further writeback or page
 885	 * cache dirtying until the reflink completes.
 886	 *
 887	 * We should never have two threads issuing writeback for the same file
 888	 * region.  There are also have post-eof checks in the writeback
 889	 * preparation code so that we don't bother writing out pages that are
 890	 * about to be truncated.
 891	 *
 892	 * If we're being called as part of directio write completion, the dio
 893	 * count is still elevated, which reflink and truncate will wait for.
 894	 * Reflink remapping takes the iolock and mmaplock and waits for
 895	 * pending dio to finish, which should prevent any directio until the
 896	 * remap completes.  Multiple concurrent directio writes to the same
 897	 * region are handled by end_cow processing only occurring for the
 898	 * threads which succeed; the outcome of multiple overlapping direct
 899	 * writes is not well defined anyway.
 900	 *
 901	 * It's possible that a buffered write and a direct write could collide
 902	 * here (the buffered write stumbles in after the dio flushes and
 903	 * invalidates the page cache and immediately queues writeback), but we
 904	 * have never supported this 100%.  If either disk write succeeds the
 905	 * blocks will be remapped.
 906	 */
 907	while (end_fsb > offset_fsb && !error)
 908		error = xfs_reflink_end_cow_extent(ip, &offset_fsb, end_fsb);
 909
 910	if (error)
 911		trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
 912	return error;
 913}
 914
 915/*
 916 * Free all CoW staging blocks that are still referenced by the ondisk refcount
 917 * metadata.  The ondisk metadata does not track which inode created the
 918 * staging extent, so callers must ensure that there are no cached inodes with
 919 * live CoW staging extents.
 920 */
 921int
 922xfs_reflink_recover_cow(
 923	struct xfs_mount	*mp)
 924{
 925	struct xfs_perag	*pag;
 926	xfs_agnumber_t		agno;
 927	int			error = 0;
 928
 929	if (!xfs_has_reflink(mp))
 930		return 0;
 931
 932	for_each_perag(mp, agno, pag) {
 933		error = xfs_refcount_recover_cow_leftovers(mp, pag);
 934		if (error) {
 935			xfs_perag_rele(pag);
 936			break;
 937		}
 938	}
 939
 940	return error;
 941}
 942
 943/*
 944 * Reflinking (Block) Ranges of Two Files Together
 945 *
 946 * First, ensure that the reflink flag is set on both inodes.  The flag is an
 947 * optimization to avoid unnecessary refcount btree lookups in the write path.
 948 *
 949 * Now we can iteratively remap the range of extents (and holes) in src to the
 950 * corresponding ranges in dest.  Let drange and srange denote the ranges of
 951 * logical blocks in dest and src touched by the reflink operation.
 952 *
 953 * While the length of drange is greater than zero,
 954 *    - Read src's bmbt at the start of srange ("imap")
 955 *    - If imap doesn't exist, make imap appear to start at the end of srange
 956 *      with zero length.
 957 *    - If imap starts before srange, advance imap to start at srange.
 958 *    - If imap goes beyond srange, truncate imap to end at the end of srange.
 959 *    - Punch (imap start - srange start + imap len) blocks from dest at
 960 *      offset (drange start).
 961 *    - If imap points to a real range of pblks,
 962 *         > Increase the refcount of the imap's pblks
 963 *         > Map imap's pblks into dest at the offset
 964 *           (drange start + imap start - srange start)
 965 *    - Advance drange and srange by (imap start - srange start + imap len)
 966 *
 967 * Finally, if the reflink made dest longer, update both the in-core and
 968 * on-disk file sizes.
 969 *
 970 * ASCII Art Demonstration:
 971 *
 972 * Let's say we want to reflink this source file:
 973 *
 974 * ----SSSSSSS-SSSSS----SSSSSS (src file)
 975 *   <-------------------->
 976 *
 977 * into this destination file:
 978 *
 979 * --DDDDDDDDDDDDDDDDDDD--DDD (dest file)
 980 *        <-------------------->
 981 * '-' means a hole, and 'S' and 'D' are written blocks in the src and dest.
 982 * Observe that the range has different logical offsets in either file.
 983 *
 984 * Consider that the first extent in the source file doesn't line up with our
 985 * reflink range.  Unmapping  and remapping are separate operations, so we can
 986 * unmap more blocks from the destination file than we remap.
 987 *
 988 * ----SSSSSSS-SSSSS----SSSSSS
 989 *   <------->
 990 * --DDDDD---------DDDDD--DDD
 991 *        <------->
 992 *
 993 * Now remap the source extent into the destination file:
 994 *
 995 * ----SSSSSSS-SSSSS----SSSSSS
 996 *   <------->
 997 * --DDDDD--SSSSSSSDDDDD--DDD
 998 *        <------->
 999 *
1000 * Do likewise with the second hole and extent in our range.  Holes in the
1001 * unmap range don't affect our operation.
1002 *
1003 * ----SSSSSSS-SSSSS----SSSSSS
1004 *            <---->
1005 * --DDDDD--SSSSSSS-SSSSS-DDD
1006 *                 <---->
1007 *
1008 * Finally, unmap and remap part of the third extent.  This will increase the
1009 * size of the destination file.
1010 *
1011 * ----SSSSSSS-SSSSS----SSSSSS
1012 *                  <----->
1013 * --DDDDD--SSSSSSS-SSSSS----SSS
1014 *                       <----->
1015 *
1016 * Once we update the destination file's i_size, we're done.
1017 */
1018
1019/*
1020 * Ensure the reflink bit is set in both inodes.
1021 */
1022STATIC int
1023xfs_reflink_set_inode_flag(
1024	struct xfs_inode	*src,
1025	struct xfs_inode	*dest)
1026{
1027	struct xfs_mount	*mp = src->i_mount;
1028	int			error;
1029	struct xfs_trans	*tp;
1030
1031	if (xfs_is_reflink_inode(src) && xfs_is_reflink_inode(dest))
1032		return 0;
1033
1034	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
1035	if (error)
1036		goto out_error;
1037
1038	/* Lock both files against IO */
1039	if (src->i_ino == dest->i_ino)
1040		xfs_ilock(src, XFS_ILOCK_EXCL);
1041	else
1042		xfs_lock_two_inodes(src, XFS_ILOCK_EXCL, dest, XFS_ILOCK_EXCL);
1043
1044	if (!xfs_is_reflink_inode(src)) {
1045		trace_xfs_reflink_set_inode_flag(src);
1046		xfs_trans_ijoin(tp, src, XFS_ILOCK_EXCL);
1047		src->i_diflags2 |= XFS_DIFLAG2_REFLINK;
1048		xfs_trans_log_inode(tp, src, XFS_ILOG_CORE);
1049		xfs_ifork_init_cow(src);
1050	} else
1051		xfs_iunlock(src, XFS_ILOCK_EXCL);
1052
1053	if (src->i_ino == dest->i_ino)
1054		goto commit_flags;
1055
1056	if (!xfs_is_reflink_inode(dest)) {
1057		trace_xfs_reflink_set_inode_flag(dest);
1058		xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
1059		dest->i_diflags2 |= XFS_DIFLAG2_REFLINK;
1060		xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
1061		xfs_ifork_init_cow(dest);
1062	} else
1063		xfs_iunlock(dest, XFS_ILOCK_EXCL);
1064
1065commit_flags:
1066	error = xfs_trans_commit(tp);
1067	if (error)
1068		goto out_error;
1069	return error;
1070
1071out_error:
1072	trace_xfs_reflink_set_inode_flag_error(dest, error, _RET_IP_);
1073	return error;
1074}
1075
1076/*
1077 * Update destination inode size & cowextsize hint, if necessary.
1078 */
1079int
1080xfs_reflink_update_dest(
1081	struct xfs_inode	*dest,
1082	xfs_off_t		newlen,
1083	xfs_extlen_t		cowextsize,
1084	unsigned int		remap_flags)
1085{
1086	struct xfs_mount	*mp = dest->i_mount;
1087	struct xfs_trans	*tp;
1088	int			error;
1089
1090	if (newlen <= i_size_read(VFS_I(dest)) && cowextsize == 0)
1091		return 0;
1092
1093	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
1094	if (error)
1095		goto out_error;
1096
1097	xfs_ilock(dest, XFS_ILOCK_EXCL);
1098	xfs_trans_ijoin(tp, dest, XFS_ILOCK_EXCL);
1099
1100	if (newlen > i_size_read(VFS_I(dest))) {
1101		trace_xfs_reflink_update_inode_size(dest, newlen);
1102		i_size_write(VFS_I(dest), newlen);
1103		dest->i_disk_size = newlen;
1104	}
1105
1106	if (cowextsize) {
1107		dest->i_cowextsize = cowextsize;
1108		dest->i_diflags2 |= XFS_DIFLAG2_COWEXTSIZE;
1109	}
1110
1111	xfs_trans_log_inode(tp, dest, XFS_ILOG_CORE);
1112
1113	error = xfs_trans_commit(tp);
1114	if (error)
1115		goto out_error;
1116	return error;
1117
1118out_error:
1119	trace_xfs_reflink_update_inode_size_error(dest, error, _RET_IP_);
1120	return error;
1121}
1122
1123/*
1124 * Do we have enough reserve in this AG to handle a reflink?  The refcount
1125 * btree already reserved all the space it needs, but the rmap btree can grow
1126 * infinitely, so we won't allow more reflinks when the AG is down to the
1127 * btree reserves.
1128 */
1129static int
1130xfs_reflink_ag_has_free_space(
1131	struct xfs_mount	*mp,
1132	xfs_agnumber_t		agno)
1133{
1134	struct xfs_perag	*pag;
1135	int			error = 0;
1136
1137	if (!xfs_has_rmapbt(mp))
1138		return 0;
1139
1140	pag = xfs_perag_get(mp, agno);
1141	if (xfs_ag_resv_critical(pag, XFS_AG_RESV_RMAPBT) ||
1142	    xfs_ag_resv_critical(pag, XFS_AG_RESV_METADATA))
1143		error = -ENOSPC;
1144	xfs_perag_put(pag);
1145	return error;
1146}
1147
1148/*
1149 * Remap the given extent into the file.  The dmap blockcount will be set to
1150 * the number of blocks that were actually remapped.
1151 */
1152STATIC int
1153xfs_reflink_remap_extent(
1154	struct xfs_inode	*ip,
1155	struct xfs_bmbt_irec	*dmap,
1156	xfs_off_t		new_isize)
1157{
1158	struct xfs_bmbt_irec	smap;
1159	struct xfs_mount	*mp = ip->i_mount;
1160	struct xfs_trans	*tp;
1161	xfs_off_t		newlen;
1162	int64_t			qdelta = 0;
1163	unsigned int		resblks;
1164	bool			quota_reserved = true;
1165	bool			smap_real;
1166	bool			dmap_written = xfs_bmap_is_written_extent(dmap);
1167	int			iext_delta = 0;
1168	int			nimaps;
1169	int			error;
1170
1171	/*
1172	 * Start a rolling transaction to switch the mappings.
1173	 *
1174	 * Adding a written extent to the extent map can cause a bmbt split,
1175	 * and removing a mapped extent from the extent can cause a bmbt split.
1176	 * The two operations cannot both cause a split since they operate on
1177	 * the same index in the bmap btree, so we only need a reservation for
1178	 * one bmbt split if either thing is happening.  However, we haven't
1179	 * locked the inode yet, so we reserve assuming this is the case.
1180	 *
1181	 * The first allocation call tries to reserve enough space to handle
1182	 * mapping dmap into a sparse part of the file plus the bmbt split.  We
1183	 * haven't locked the inode or read the existing mapping yet, so we do
1184	 * not know for sure that we need the space.  This should succeed most
1185	 * of the time.
1186	 *
1187	 * If the first attempt fails, try again but reserving only enough
1188	 * space to handle a bmbt split.  This is the hard minimum requirement,
1189	 * and we revisit quota reservations later when we know more about what
1190	 * we're remapping.
1191	 */
1192	resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
1193	error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
1194			resblks + dmap->br_blockcount, 0, false, &tp);
1195	if (error == -EDQUOT || error == -ENOSPC) {
1196		quota_reserved = false;
1197		error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write,
1198				resblks, 0, false, &tp);
1199	}
1200	if (error)
1201		goto out;
1202
1203	/*
1204	 * Read what's currently mapped in the destination file into smap.
1205	 * If smap isn't a hole, we will have to remove it before we can add
1206	 * dmap to the destination file.
1207	 */
1208	nimaps = 1;
1209	error = xfs_bmapi_read(ip, dmap->br_startoff, dmap->br_blockcount,
1210			&smap, &nimaps, 0);
1211	if (error)
1212		goto out_cancel;
1213	ASSERT(nimaps == 1 && smap.br_startoff == dmap->br_startoff);
1214	smap_real = xfs_bmap_is_real_extent(&smap);
1215
1216	/*
1217	 * We can only remap as many blocks as the smaller of the two extent
1218	 * maps, because we can only remap one extent at a time.
1219	 */
1220	dmap->br_blockcount = min(dmap->br_blockcount, smap.br_blockcount);
1221	ASSERT(dmap->br_blockcount == smap.br_blockcount);
1222
1223	trace_xfs_reflink_remap_extent_dest(ip, &smap);
1224
1225	/*
1226	 * Two extents mapped to the same physical block must not have
1227	 * different states; that's filesystem corruption.  Move on to the next
1228	 * extent if they're both holes or both the same physical extent.
1229	 */
1230	if (dmap->br_startblock == smap.br_startblock) {
1231		if (dmap->br_state != smap.br_state) {
1232			xfs_bmap_mark_sick(ip, XFS_DATA_FORK);
1233			error = -EFSCORRUPTED;
1234		}
1235		goto out_cancel;
1236	}
1237
1238	/* If both extents are unwritten, leave them alone. */
1239	if (dmap->br_state == XFS_EXT_UNWRITTEN &&
1240	    smap.br_state == XFS_EXT_UNWRITTEN)
1241		goto out_cancel;
1242
1243	/* No reflinking if the AG of the dest mapping is low on space. */
1244	if (dmap_written) {
1245		error = xfs_reflink_ag_has_free_space(mp,
1246				XFS_FSB_TO_AGNO(mp, dmap->br_startblock));
1247		if (error)
1248			goto out_cancel;
1249	}
1250
1251	/*
1252	 * Increase quota reservation if we think the quota block counter for
1253	 * this file could increase.
1254	 *
1255	 * If we are mapping a written extent into the file, we need to have
1256	 * enough quota block count reservation to handle the blocks in that
1257	 * extent.  We log only the delta to the quota block counts, so if the
1258	 * extent we're unmapping also has blocks allocated to it, we don't
1259	 * need a quota reservation for the extent itself.
1260	 *
1261	 * Note that if we're replacing a delalloc reservation with a written
1262	 * extent, we have to take the full quota reservation because removing
1263	 * the delalloc reservation gives the block count back to the quota
1264	 * count.  This is suboptimal, but the VFS flushed the dest range
1265	 * before we started.  That should have removed all the delalloc
1266	 * reservations, but we code defensively.
1267	 *
1268	 * xfs_trans_alloc_inode above already tried to grab an even larger
1269	 * quota reservation, and kicked off a blockgc scan if it couldn't.
1270	 * If we can't get a potentially smaller quota reservation now, we're
1271	 * done.
1272	 */
1273	if (!quota_reserved && !smap_real && dmap_written) {
1274		error = xfs_trans_reserve_quota_nblks(tp, ip,
1275				dmap->br_blockcount, 0, false);
1276		if (error)
1277			goto out_cancel;
1278	}
1279
1280	if (smap_real)
1281		++iext_delta;
1282
1283	if (dmap_written)
1284		++iext_delta;
1285
1286	error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK, iext_delta);
1287	if (error == -EFBIG)
1288		error = xfs_iext_count_upgrade(tp, ip, iext_delta);
1289	if (error)
1290		goto out_cancel;
1291
1292	if (smap_real) {
1293		/*
1294		 * If the extent we're unmapping is backed by storage (written
1295		 * or not), unmap the extent and drop its refcount.
1296		 */
1297		xfs_bmap_unmap_extent(tp, ip, XFS_DATA_FORK, &smap);
1298		xfs_refcount_decrease_extent(tp, &smap);
1299		qdelta -= smap.br_blockcount;
1300	} else if (smap.br_startblock == DELAYSTARTBLOCK) {
1301		int		done;
1302
1303		/*
1304		 * If the extent we're unmapping is a delalloc reservation,
1305		 * we can use the regular bunmapi function to release the
1306		 * incore state.  Dropping the delalloc reservation takes care
1307		 * of the quota reservation for us.
1308		 */
1309		error = xfs_bunmapi(NULL, ip, smap.br_startoff,
1310				smap.br_blockcount, 0, 1, &done);
1311		if (error)
1312			goto out_cancel;
1313		ASSERT(done);
1314	}
1315
1316	/*
1317	 * If the extent we're sharing is backed by written storage, increase
1318	 * its refcount and map it into the file.
1319	 */
1320	if (dmap_written) {
1321		xfs_refcount_increase_extent(tp, dmap);
1322		xfs_bmap_map_extent(tp, ip, XFS_DATA_FORK, dmap);
1323		qdelta += dmap->br_blockcount;
1324	}
1325
1326	xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_BCOUNT, qdelta);
1327
1328	/* Update dest isize if needed. */
1329	newlen = XFS_FSB_TO_B(mp, dmap->br_startoff + dmap->br_blockcount);
1330	newlen = min_t(xfs_off_t, newlen, new_isize);
1331	if (newlen > i_size_read(VFS_I(ip))) {
1332		trace_xfs_reflink_update_inode_size(ip, newlen);
1333		i_size_write(VFS_I(ip), newlen);
1334		ip->i_disk_size = newlen;
1335		xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
1336	}
1337
1338	/* Commit everything and unlock. */
1339	error = xfs_trans_commit(tp);
1340	goto out_unlock;
1341
1342out_cancel:
1343	xfs_trans_cancel(tp);
1344out_unlock:
1345	xfs_iunlock(ip, XFS_ILOCK_EXCL);
1346out:
1347	if (error)
1348		trace_xfs_reflink_remap_extent_error(ip, error, _RET_IP_);
1349	return error;
1350}
1351
1352/* Remap a range of one file to the other. */
1353int
1354xfs_reflink_remap_blocks(
1355	struct xfs_inode	*src,
1356	loff_t			pos_in,
1357	struct xfs_inode	*dest,
1358	loff_t			pos_out,
1359	loff_t			remap_len,
1360	loff_t			*remapped)
1361{
1362	struct xfs_bmbt_irec	imap;
1363	struct xfs_mount	*mp = src->i_mount;
1364	xfs_fileoff_t		srcoff = XFS_B_TO_FSBT(mp, pos_in);
1365	xfs_fileoff_t		destoff = XFS_B_TO_FSBT(mp, pos_out);
1366	xfs_filblks_t		len;
1367	xfs_filblks_t		remapped_len = 0;
1368	xfs_off_t		new_isize = pos_out + remap_len;
1369	int			nimaps;
1370	int			error = 0;
1371
1372	len = min_t(xfs_filblks_t, XFS_B_TO_FSB(mp, remap_len),
1373			XFS_MAX_FILEOFF);
1374
1375	trace_xfs_reflink_remap_blocks(src, srcoff, len, dest, destoff);
1376
1377	while (len > 0) {
1378		unsigned int	lock_mode;
1379
1380		/* Read extent from the source file */
1381		nimaps = 1;
1382		lock_mode = xfs_ilock_data_map_shared(src);
1383		error = xfs_bmapi_read(src, srcoff, len, &imap, &nimaps, 0);
1384		xfs_iunlock(src, lock_mode);
1385		if (error)
1386			break;
1387		/*
1388		 * The caller supposedly flushed all dirty pages in the source
1389		 * file range, which means that writeback should have allocated
1390		 * or deleted all delalloc reservations in that range.  If we
1391		 * find one, that's a good sign that something is seriously
1392		 * wrong here.
1393		 */
1394		ASSERT(nimaps == 1 && imap.br_startoff == srcoff);
1395		if (imap.br_startblock == DELAYSTARTBLOCK) {
1396			ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
1397			xfs_bmap_mark_sick(src, XFS_DATA_FORK);
1398			error = -EFSCORRUPTED;
1399			break;
1400		}
1401
1402		trace_xfs_reflink_remap_extent_src(src, &imap);
1403
1404		/* Remap into the destination file at the given offset. */
1405		imap.br_startoff = destoff;
1406		error = xfs_reflink_remap_extent(dest, &imap, new_isize);
1407		if (error)
1408			break;
1409
1410		if (fatal_signal_pending(current)) {
1411			error = -EINTR;
1412			break;
1413		}
1414
1415		/* Advance drange/srange */
1416		srcoff += imap.br_blockcount;
1417		destoff += imap.br_blockcount;
1418		len -= imap.br_blockcount;
1419		remapped_len += imap.br_blockcount;
 
1420	}
1421
1422	if (error)
1423		trace_xfs_reflink_remap_blocks_error(dest, error, _RET_IP_);
1424	*remapped = min_t(loff_t, remap_len,
1425			  XFS_FSB_TO_B(src->i_mount, remapped_len));
1426	return error;
1427}
1428
1429/*
1430 * If we're reflinking to a point past the destination file's EOF, we must
1431 * zero any speculative post-EOF preallocations that sit between the old EOF
1432 * and the destination file offset.
1433 */
1434static int
1435xfs_reflink_zero_posteof(
1436	struct xfs_inode	*ip,
1437	loff_t			pos)
1438{
1439	loff_t			isize = i_size_read(VFS_I(ip));
1440
1441	if (pos <= isize)
1442		return 0;
1443
1444	trace_xfs_zero_eof(ip, isize, pos - isize);
1445	return xfs_zero_range(ip, isize, pos - isize, NULL);
1446}
1447
1448/*
1449 * Prepare two files for range cloning.  Upon a successful return both inodes
1450 * will have the iolock and mmaplock held, the page cache of the out file will
1451 * be truncated, and any leases on the out file will have been broken.  This
1452 * function borrows heavily from xfs_file_aio_write_checks.
1453 *
1454 * The VFS allows partial EOF blocks to "match" for dedupe even though it hasn't
1455 * checked that the bytes beyond EOF physically match. Hence we cannot use the
1456 * EOF block in the source dedupe range because it's not a complete block match,
1457 * hence can introduce a corruption into the file that has it's block replaced.
1458 *
1459 * In similar fashion, the VFS file cloning also allows partial EOF blocks to be
1460 * "block aligned" for the purposes of cloning entire files.  However, if the
1461 * source file range includes the EOF block and it lands within the existing EOF
1462 * of the destination file, then we can expose stale data from beyond the source
1463 * file EOF in the destination file.
1464 *
1465 * XFS doesn't support partial block sharing, so in both cases we have check
1466 * these cases ourselves. For dedupe, we can simply round the length to dedupe
1467 * down to the previous whole block and ignore the partial EOF block. While this
1468 * means we can't dedupe the last block of a file, this is an acceptible
1469 * tradeoff for simplicity on implementation.
1470 *
1471 * For cloning, we want to share the partial EOF block if it is also the new EOF
1472 * block of the destination file. If the partial EOF block lies inside the
1473 * existing destination EOF, then we have to abort the clone to avoid exposing
1474 * stale data in the destination file. Hence we reject these clone attempts with
1475 * -EINVAL in this case.
1476 */
1477int
1478xfs_reflink_remap_prep(
1479	struct file		*file_in,
1480	loff_t			pos_in,
1481	struct file		*file_out,
1482	loff_t			pos_out,
1483	loff_t			*len,
1484	unsigned int		remap_flags)
1485{
1486	struct inode		*inode_in = file_inode(file_in);
1487	struct xfs_inode	*src = XFS_I(inode_in);
1488	struct inode		*inode_out = file_inode(file_out);
1489	struct xfs_inode	*dest = XFS_I(inode_out);
1490	int			ret;
1491
1492	/* Lock both files against IO */
1493	ret = xfs_ilock2_io_mmap(src, dest);
1494	if (ret)
1495		return ret;
1496
1497	/* Check file eligibility and prepare for block sharing. */
1498	ret = -EINVAL;
1499	/* Don't reflink realtime inodes */
1500	if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
1501		goto out_unlock;
1502
1503	/* Don't share DAX file data with non-DAX file. */
1504	if (IS_DAX(inode_in) != IS_DAX(inode_out))
1505		goto out_unlock;
1506
1507	if (!IS_DAX(inode_in))
1508		ret = generic_remap_file_range_prep(file_in, pos_in, file_out,
1509				pos_out, len, remap_flags);
1510	else
1511		ret = dax_remap_file_range_prep(file_in, pos_in, file_out,
1512				pos_out, len, remap_flags, &xfs_read_iomap_ops);
1513	if (ret || *len == 0)
1514		goto out_unlock;
1515
1516	/* Attach dquots to dest inode before changing block map */
1517	ret = xfs_qm_dqattach(dest);
1518	if (ret)
1519		goto out_unlock;
1520
1521	/*
1522	 * Zero existing post-eof speculative preallocations in the destination
1523	 * file.
1524	 */
1525	ret = xfs_reflink_zero_posteof(dest, pos_out);
1526	if (ret)
1527		goto out_unlock;
1528
1529	/* Set flags and remap blocks. */
1530	ret = xfs_reflink_set_inode_flag(src, dest);
1531	if (ret)
1532		goto out_unlock;
1533
1534	/*
1535	 * If pos_out > EOF, we may have dirtied blocks between EOF and
1536	 * pos_out. In that case, we need to extend the flush and unmap to cover
1537	 * from EOF to the end of the copy length.
1538	 */
1539	if (pos_out > XFS_ISIZE(dest)) {
1540		loff_t	flen = *len + (pos_out - XFS_ISIZE(dest));
1541		ret = xfs_flush_unmap_range(dest, XFS_ISIZE(dest), flen);
1542	} else {
1543		ret = xfs_flush_unmap_range(dest, pos_out, *len);
1544	}
1545	if (ret)
1546		goto out_unlock;
1547
1548	xfs_iflags_set(src, XFS_IREMAPPING);
1549	if (inode_in != inode_out)
1550		xfs_ilock_demote(src, XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL);
1551
1552	return 0;
1553out_unlock:
1554	xfs_iunlock2_io_mmap(src, dest);
1555	return ret;
1556}
1557
1558/* Does this inode need the reflink flag? */
1559int
1560xfs_reflink_inode_has_shared_extents(
1561	struct xfs_trans		*tp,
1562	struct xfs_inode		*ip,
1563	bool				*has_shared)
1564{
1565	struct xfs_bmbt_irec		got;
1566	struct xfs_mount		*mp = ip->i_mount;
1567	struct xfs_ifork		*ifp;
1568	struct xfs_iext_cursor		icur;
1569	bool				found;
1570	int				error;
1571
1572	ifp = xfs_ifork_ptr(ip, XFS_DATA_FORK);
1573	error = xfs_iread_extents(tp, ip, XFS_DATA_FORK);
1574	if (error)
1575		return error;
1576
1577	*has_shared = false;
1578	found = xfs_iext_lookup_extent(ip, ifp, 0, &icur, &got);
1579	while (found) {
1580		struct xfs_perag	*pag;
1581		xfs_agblock_t		agbno;
1582		xfs_extlen_t		aglen;
1583		xfs_agblock_t		rbno;
1584		xfs_extlen_t		rlen;
1585
1586		if (isnullstartblock(got.br_startblock) ||
1587		    got.br_state != XFS_EXT_NORM)
1588			goto next;
1589
1590		pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, got.br_startblock));
1591		agbno = XFS_FSB_TO_AGBNO(mp, got.br_startblock);
1592		aglen = got.br_blockcount;
1593		error = xfs_reflink_find_shared(pag, tp, agbno, aglen,
1594				&rbno, &rlen, false);
1595		xfs_perag_put(pag);
1596		if (error)
1597			return error;
1598
1599		/* Is there still a shared block here? */
1600		if (rbno != NULLAGBLOCK) {
1601			*has_shared = true;
1602			return 0;
1603		}
1604next:
1605		found = xfs_iext_next_extent(ifp, &icur, &got);
1606	}
1607
1608	return 0;
1609}
1610
1611/*
1612 * Clear the inode reflink flag if there are no shared extents.
1613 *
1614 * The caller is responsible for joining the inode to the transaction passed in.
1615 * The inode will be joined to the transaction that is returned to the caller.
1616 */
1617int
1618xfs_reflink_clear_inode_flag(
1619	struct xfs_inode	*ip,
1620	struct xfs_trans	**tpp)
1621{
1622	bool			needs_flag;
1623	int			error = 0;
1624
1625	ASSERT(xfs_is_reflink_inode(ip));
 
 
 
1626
1627	error = xfs_reflink_inode_has_shared_extents(*tpp, ip, &needs_flag);
1628	if (error || needs_flag)
1629		return error;
1630
1631	/*
1632	 * We didn't find any shared blocks so turn off the reflink flag.
1633	 * First, get rid of any leftover CoW mappings.
1634	 */
1635	error = xfs_reflink_cancel_cow_blocks(ip, tpp, 0, XFS_MAX_FILEOFF,
1636			true);
1637	if (error)
1638		return error;
1639
1640	/* Clear the inode flag. */
1641	trace_xfs_reflink_unset_inode_flag(ip);
1642	ip->i_diflags2 &= ~XFS_DIFLAG2_REFLINK;
1643	xfs_inode_clear_cowblocks_tag(ip);
1644	xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
1645
1646	return error;
1647}
1648
1649/*
1650 * Clear the inode reflink flag if there are no shared extents and the size
1651 * hasn't changed.
1652 */
1653STATIC int
1654xfs_reflink_try_clear_inode_flag(
1655	struct xfs_inode	*ip)
1656{
1657	struct xfs_mount	*mp = ip->i_mount;
1658	struct xfs_trans	*tp;
1659	int			error = 0;
1660
1661	/* Start a rolling transaction to remove the mappings */
1662	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
1663	if (error)
1664		return error;
1665
1666	xfs_ilock(ip, XFS_ILOCK_EXCL);
1667	xfs_trans_ijoin(tp, ip, 0);
1668
1669	error = xfs_reflink_clear_inode_flag(ip, &tp);
1670	if (error)
1671		goto cancel;
1672
1673	error = xfs_trans_commit(tp);
1674	if (error)
1675		goto out;
1676
1677	xfs_iunlock(ip, XFS_ILOCK_EXCL);
1678	return 0;
1679cancel:
1680	xfs_trans_cancel(tp);
1681out:
1682	xfs_iunlock(ip, XFS_ILOCK_EXCL);
1683	return error;
1684}
1685
1686/*
1687 * Pre-COW all shared blocks within a given byte range of a file and turn off
1688 * the reflink flag if we unshare all of the file's blocks.
1689 */
1690int
1691xfs_reflink_unshare(
1692	struct xfs_inode	*ip,
1693	xfs_off_t		offset,
1694	xfs_off_t		len)
1695{
1696	struct inode		*inode = VFS_I(ip);
1697	int			error;
1698
1699	if (!xfs_is_reflink_inode(ip))
1700		return 0;
1701
1702	trace_xfs_reflink_unshare(ip, offset, len);
1703
1704	inode_dio_wait(inode);
1705
1706	if (IS_DAX(inode))
1707		error = dax_file_unshare(inode, offset, len,
1708				&xfs_dax_write_iomap_ops);
1709	else
1710		error = iomap_file_unshare(inode, offset, len,
1711				&xfs_buffered_write_iomap_ops);
1712	if (error)
1713		goto out;
1714
1715	error = filemap_write_and_wait_range(inode->i_mapping, offset,
1716			offset + len - 1);
1717	if (error)
1718		goto out;
1719
1720	/* Turn off the reflink flag if possible. */
1721	error = xfs_reflink_try_clear_inode_flag(ip);
1722	if (error)
1723		goto out;
1724	return 0;
1725
1726out:
1727	trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
1728	return error;
1729}