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