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