1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
4 * Copyright (c) 2013 Red Hat, Inc.
5 * All Rights Reserved.
6 */
7#include "xfs.h"
8#include "xfs_fs.h"
9#include "xfs_shared.h"
10#include "xfs_format.h"
11#include "xfs_log_format.h"
12#include "xfs_trans_resv.h"
13#include "xfs_bit.h"
14#include "xfs_mount.h"
15#include "xfs_defer.h"
16#include "xfs_da_format.h"
17#include "xfs_da_btree.h"
18#include "xfs_inode.h"
19#include "xfs_trans.h"
20#include "xfs_bmap.h"
21#include "xfs_attr.h"
22#include "xfs_attr_remote.h"
23#include "xfs_trace.h"
24#include "xfs_error.h"
25#include "xfs_health.h"
26
27#define ATTR_RMTVALUE_MAPSIZE 1 /* # of map entries at once */
28
29/*
30 * Remote Attribute Values
31 * =======================
32 *
33 * Remote extended attribute values are conceptually simple -- they're written
34 * to data blocks mapped by an inode's attribute fork, and they have an upper
35 * size limit of 64k. Setting a value does not involve the XFS log.
36 *
37 * However, on a v5 filesystem, maximally sized remote attr values require one
38 * block more than 64k worth of space to hold both the remote attribute value
39 * header (64 bytes). On a 4k block filesystem this results in a 68k buffer;
40 * on a 64k block filesystem, this would be a 128k buffer. Note that the log
41 * format can only handle a dirty buffer of XFS_MAX_BLOCKSIZE length (64k).
42 * Therefore, we /must/ ensure that remote attribute value buffers never touch
43 * the logging system and therefore never have a log item.
44 */
45
46/*
47 * Each contiguous block has a header, so it is not just a simple attribute
48 * length to FSB conversion.
49 */
50int
51xfs_attr3_rmt_blocks(
52 struct xfs_mount *mp,
53 int attrlen)
54{
55 if (xfs_has_crc(mp)) {
56 int buflen = XFS_ATTR3_RMT_BUF_SPACE(mp, mp->m_sb.sb_blocksize);
57 return (attrlen + buflen - 1) / buflen;
58 }
59 return XFS_B_TO_FSB(mp, attrlen);
60}
61
62/*
63 * Checking of the remote attribute header is split into two parts. The verifier
64 * does CRC, location and bounds checking, the unpacking function checks the
65 * attribute parameters and owner.
66 */
67static xfs_failaddr_t
68xfs_attr3_rmt_hdr_ok(
69 void *ptr,
70 xfs_ino_t ino,
71 uint32_t offset,
72 uint32_t size,
73 xfs_daddr_t bno)
74{
75 struct xfs_attr3_rmt_hdr *rmt = ptr;
76
77 if (bno != be64_to_cpu(rmt->rm_blkno))
78 return __this_address;
79 if (offset != be32_to_cpu(rmt->rm_offset))
80 return __this_address;
81 if (size != be32_to_cpu(rmt->rm_bytes))
82 return __this_address;
83 if (ino != be64_to_cpu(rmt->rm_owner))
84 return __this_address;
85
86 /* ok */
87 return NULL;
88}
89
90static xfs_failaddr_t
91xfs_attr3_rmt_verify(
92 struct xfs_mount *mp,
93 struct xfs_buf *bp,
94 void *ptr,
95 int fsbsize,
96 xfs_daddr_t bno)
97{
98 struct xfs_attr3_rmt_hdr *rmt = ptr;
99
100 if (!xfs_verify_magic(bp, rmt->rm_magic))
101 return __this_address;
102 if (!uuid_equal(&rmt->rm_uuid, &mp->m_sb.sb_meta_uuid))
103 return __this_address;
104 if (be64_to_cpu(rmt->rm_blkno) != bno)
105 return __this_address;
106 if (be32_to_cpu(rmt->rm_bytes) > fsbsize - sizeof(*rmt))
107 return __this_address;
108 if (be32_to_cpu(rmt->rm_offset) +
109 be32_to_cpu(rmt->rm_bytes) > XFS_XATTR_SIZE_MAX)
110 return __this_address;
111 if (rmt->rm_owner == 0)
112 return __this_address;
113
114 return NULL;
115}
116
117static int
118__xfs_attr3_rmt_read_verify(
119 struct xfs_buf *bp,
120 bool check_crc,
121 xfs_failaddr_t *failaddr)
122{
123 struct xfs_mount *mp = bp->b_mount;
124 char *ptr;
125 int len;
126 xfs_daddr_t bno;
127 int blksize = mp->m_attr_geo->blksize;
128
129 /* no verification of non-crc buffers */
130 if (!xfs_has_crc(mp))
131 return 0;
132
133 ptr = bp->b_addr;
134 bno = xfs_buf_daddr(bp);
135 len = BBTOB(bp->b_length);
136 ASSERT(len >= blksize);
137
138 while (len > 0) {
139 if (check_crc &&
140 !xfs_verify_cksum(ptr, blksize, XFS_ATTR3_RMT_CRC_OFF)) {
141 *failaddr = __this_address;
142 return -EFSBADCRC;
143 }
144 *failaddr = xfs_attr3_rmt_verify(mp, bp, ptr, blksize, bno);
145 if (*failaddr)
146 return -EFSCORRUPTED;
147 len -= blksize;
148 ptr += blksize;
149 bno += BTOBB(blksize);
150 }
151
152 if (len != 0) {
153 *failaddr = __this_address;
154 return -EFSCORRUPTED;
155 }
156
157 return 0;
158}
159
160static void
161xfs_attr3_rmt_read_verify(
162 struct xfs_buf *bp)
163{
164 xfs_failaddr_t fa;
165 int error;
166
167 error = __xfs_attr3_rmt_read_verify(bp, true, &fa);
168 if (error)
169 xfs_verifier_error(bp, error, fa);
170}
171
172static xfs_failaddr_t
173xfs_attr3_rmt_verify_struct(
174 struct xfs_buf *bp)
175{
176 xfs_failaddr_t fa;
177 int error;
178
179 error = __xfs_attr3_rmt_read_verify(bp, false, &fa);
180 return error ? fa : NULL;
181}
182
183static void
184xfs_attr3_rmt_write_verify(
185 struct xfs_buf *bp)
186{
187 struct xfs_mount *mp = bp->b_mount;
188 xfs_failaddr_t fa;
189 int blksize = mp->m_attr_geo->blksize;
190 char *ptr;
191 int len;
192 xfs_daddr_t bno;
193
194 /* no verification of non-crc buffers */
195 if (!xfs_has_crc(mp))
196 return;
197
198 ptr = bp->b_addr;
199 bno = xfs_buf_daddr(bp);
200 len = BBTOB(bp->b_length);
201 ASSERT(len >= blksize);
202
203 while (len > 0) {
204 struct xfs_attr3_rmt_hdr *rmt = (struct xfs_attr3_rmt_hdr *)ptr;
205
206 fa = xfs_attr3_rmt_verify(mp, bp, ptr, blksize, bno);
207 if (fa) {
208 xfs_verifier_error(bp, -EFSCORRUPTED, fa);
209 return;
210 }
211
212 /*
213 * Ensure we aren't writing bogus LSNs to disk. See
214 * xfs_attr3_rmt_hdr_set() for the explanation.
215 */
216 if (rmt->rm_lsn != cpu_to_be64(NULLCOMMITLSN)) {
217 xfs_verifier_error(bp, -EFSCORRUPTED, __this_address);
218 return;
219 }
220 xfs_update_cksum(ptr, blksize, XFS_ATTR3_RMT_CRC_OFF);
221
222 len -= blksize;
223 ptr += blksize;
224 bno += BTOBB(blksize);
225 }
226
227 if (len != 0)
228 xfs_verifier_error(bp, -EFSCORRUPTED, __this_address);
229}
230
231const struct xfs_buf_ops xfs_attr3_rmt_buf_ops = {
232 .name = "xfs_attr3_rmt",
233 .magic = { 0, cpu_to_be32(XFS_ATTR3_RMT_MAGIC) },
234 .verify_read = xfs_attr3_rmt_read_verify,
235 .verify_write = xfs_attr3_rmt_write_verify,
236 .verify_struct = xfs_attr3_rmt_verify_struct,
237};
238
239STATIC int
240xfs_attr3_rmt_hdr_set(
241 struct xfs_mount *mp,
242 void *ptr,
243 xfs_ino_t ino,
244 uint32_t offset,
245 uint32_t size,
246 xfs_daddr_t bno)
247{
248 struct xfs_attr3_rmt_hdr *rmt = ptr;
249
250 if (!xfs_has_crc(mp))
251 return 0;
252
253 rmt->rm_magic = cpu_to_be32(XFS_ATTR3_RMT_MAGIC);
254 rmt->rm_offset = cpu_to_be32(offset);
255 rmt->rm_bytes = cpu_to_be32(size);
256 uuid_copy(&rmt->rm_uuid, &mp->m_sb.sb_meta_uuid);
257 rmt->rm_owner = cpu_to_be64(ino);
258 rmt->rm_blkno = cpu_to_be64(bno);
259
260 /*
261 * Remote attribute blocks are written synchronously, so we don't
262 * have an LSN that we can stamp in them that makes any sense to log
263 * recovery. To ensure that log recovery handles overwrites of these
264 * blocks sanely (i.e. once they've been freed and reallocated as some
265 * other type of metadata) we need to ensure that the LSN has a value
266 * that tells log recovery to ignore the LSN and overwrite the buffer
267 * with whatever is in it's log. To do this, we use the magic
268 * NULLCOMMITLSN to indicate that the LSN is invalid.
269 */
270 rmt->rm_lsn = cpu_to_be64(NULLCOMMITLSN);
271
272 return sizeof(struct xfs_attr3_rmt_hdr);
273}
274
275/*
276 * Helper functions to copy attribute data in and out of the one disk extents
277 */
278STATIC int
279xfs_attr_rmtval_copyout(
280 struct xfs_mount *mp,
281 struct xfs_buf *bp,
282 struct xfs_inode *dp,
283 int *offset,
284 int *valuelen,
285 uint8_t **dst)
286{
287 char *src = bp->b_addr;
288 xfs_ino_t ino = dp->i_ino;
289 xfs_daddr_t bno = xfs_buf_daddr(bp);
290 int len = BBTOB(bp->b_length);
291 int blksize = mp->m_attr_geo->blksize;
292
293 ASSERT(len >= blksize);
294
295 while (len > 0 && *valuelen > 0) {
296 int hdr_size = 0;
297 int byte_cnt = XFS_ATTR3_RMT_BUF_SPACE(mp, blksize);
298
299 byte_cnt = min(*valuelen, byte_cnt);
300
301 if (xfs_has_crc(mp)) {
302 if (xfs_attr3_rmt_hdr_ok(src, ino, *offset,
303 byte_cnt, bno)) {
304 xfs_alert(mp,
305"remote attribute header mismatch bno/off/len/owner (0x%llx/0x%x/Ox%x/0x%llx)",
306 bno, *offset, byte_cnt, ino);
307 xfs_dirattr_mark_sick(dp, XFS_ATTR_FORK);
308 return -EFSCORRUPTED;
309 }
310 hdr_size = sizeof(struct xfs_attr3_rmt_hdr);
311 }
312
313 memcpy(*dst, src + hdr_size, byte_cnt);
314
315 /* roll buffer forwards */
316 len -= blksize;
317 src += blksize;
318 bno += BTOBB(blksize);
319
320 /* roll attribute data forwards */
321 *valuelen -= byte_cnt;
322 *dst += byte_cnt;
323 *offset += byte_cnt;
324 }
325 return 0;
326}
327
328STATIC void
329xfs_attr_rmtval_copyin(
330 struct xfs_mount *mp,
331 struct xfs_buf *bp,
332 xfs_ino_t ino,
333 int *offset,
334 int *valuelen,
335 uint8_t **src)
336{
337 char *dst = bp->b_addr;
338 xfs_daddr_t bno = xfs_buf_daddr(bp);
339 int len = BBTOB(bp->b_length);
340 int blksize = mp->m_attr_geo->blksize;
341
342 ASSERT(len >= blksize);
343
344 while (len > 0 && *valuelen > 0) {
345 int hdr_size;
346 int byte_cnt = XFS_ATTR3_RMT_BUF_SPACE(mp, blksize);
347
348 byte_cnt = min(*valuelen, byte_cnt);
349 hdr_size = xfs_attr3_rmt_hdr_set(mp, dst, ino, *offset,
350 byte_cnt, bno);
351
352 memcpy(dst + hdr_size, *src, byte_cnt);
353
354 /*
355 * If this is the last block, zero the remainder of it.
356 * Check that we are actually the last block, too.
357 */
358 if (byte_cnt + hdr_size < blksize) {
359 ASSERT(*valuelen - byte_cnt == 0);
360 ASSERT(len == blksize);
361 memset(dst + hdr_size + byte_cnt, 0,
362 blksize - hdr_size - byte_cnt);
363 }
364
365 /* roll buffer forwards */
366 len -= blksize;
367 dst += blksize;
368 bno += BTOBB(blksize);
369
370 /* roll attribute data forwards */
371 *valuelen -= byte_cnt;
372 *src += byte_cnt;
373 *offset += byte_cnt;
374 }
375}
376
377/*
378 * Read the value associated with an attribute from the out-of-line buffer
379 * that we stored it in.
380 *
381 * Returns 0 on successful retrieval, otherwise an error.
382 */
383int
384xfs_attr_rmtval_get(
385 struct xfs_da_args *args)
386{
387 struct xfs_bmbt_irec map[ATTR_RMTVALUE_MAPSIZE];
388 struct xfs_mount *mp = args->dp->i_mount;
389 struct xfs_buf *bp;
390 xfs_dablk_t lblkno = args->rmtblkno;
391 uint8_t *dst = args->value;
392 int valuelen;
393 int nmap;
394 int error;
395 int blkcnt = args->rmtblkcnt;
396 int i;
397 int offset = 0;
398
399 trace_xfs_attr_rmtval_get(args);
400
401 ASSERT(args->valuelen != 0);
402 ASSERT(args->rmtvaluelen == args->valuelen);
403
404 valuelen = args->rmtvaluelen;
405 while (valuelen > 0) {
406 nmap = ATTR_RMTVALUE_MAPSIZE;
407 error = xfs_bmapi_read(args->dp, (xfs_fileoff_t)lblkno,
408 blkcnt, map, &nmap,
409 XFS_BMAPI_ATTRFORK);
410 if (error)
411 return error;
412 ASSERT(nmap >= 1);
413
414 for (i = 0; (i < nmap) && (valuelen > 0); i++) {
415 xfs_daddr_t dblkno;
416 int dblkcnt;
417
418 ASSERT((map[i].br_startblock != DELAYSTARTBLOCK) &&
419 (map[i].br_startblock != HOLESTARTBLOCK));
420 dblkno = XFS_FSB_TO_DADDR(mp, map[i].br_startblock);
421 dblkcnt = XFS_FSB_TO_BB(mp, map[i].br_blockcount);
422 error = xfs_buf_read(mp->m_ddev_targp, dblkno, dblkcnt,
423 0, &bp, &xfs_attr3_rmt_buf_ops);
424 if (xfs_metadata_is_sick(error))
425 xfs_dirattr_mark_sick(args->dp, XFS_ATTR_FORK);
426 if (error)
427 return error;
428
429 error = xfs_attr_rmtval_copyout(mp, bp, args->dp,
430 &offset, &valuelen,
431 &dst);
432 xfs_buf_relse(bp);
433 if (error)
434 return error;
435
436 /* roll attribute extent map forwards */
437 lblkno += map[i].br_blockcount;
438 blkcnt -= map[i].br_blockcount;
439 }
440 }
441 ASSERT(valuelen == 0);
442 return 0;
443}
444
445/*
446 * Find a "hole" in the attribute address space large enough for us to drop the
447 * new attributes value into
448 */
449int
450xfs_attr_rmt_find_hole(
451 struct xfs_da_args *args)
452{
453 struct xfs_inode *dp = args->dp;
454 struct xfs_mount *mp = dp->i_mount;
455 int error;
456 int blkcnt;
457 xfs_fileoff_t lfileoff = 0;
458
459 /*
460 * Because CRC enable attributes have headers, we can't just do a
461 * straight byte to FSB conversion and have to take the header space
462 * into account.
463 */
464 blkcnt = xfs_attr3_rmt_blocks(mp, attrlen: args->rmtvaluelen);
465 error = xfs_bmap_first_unused(args->trans, args->dp, blkcnt, &lfileoff,
466 XFS_ATTR_FORK);
467 if (error)
468 return error;
469
470 args->rmtblkno = (xfs_dablk_t)lfileoff;
471 args->rmtblkcnt = blkcnt;
472
473 return 0;
474}
475
476int
477xfs_attr_rmtval_set_value(
478 struct xfs_da_args *args)
479{
480 struct xfs_inode *dp = args->dp;
481 struct xfs_mount *mp = dp->i_mount;
482 struct xfs_bmbt_irec map;
483 xfs_dablk_t lblkno;
484 uint8_t *src = args->value;
485 int blkcnt;
486 int valuelen;
487 int nmap;
488 int error;
489 int offset = 0;
490
491 /*
492 * Roll through the "value", copying the attribute value to the
493 * already-allocated blocks. Blocks are written synchronously
494 * so that we can know they are all on disk before we turn off
495 * the INCOMPLETE flag.
496 */
497 lblkno = args->rmtblkno;
498 blkcnt = args->rmtblkcnt;
499 valuelen = args->rmtvaluelen;
500 while (valuelen > 0) {
501 struct xfs_buf *bp;
502 xfs_daddr_t dblkno;
503 int dblkcnt;
504
505 ASSERT(blkcnt > 0);
506
507 nmap = 1;
508 error = xfs_bmapi_read(dp, (xfs_fileoff_t)lblkno,
509 blkcnt, &map, &nmap,
510 XFS_BMAPI_ATTRFORK);
511 if (error)
512 return error;
513 ASSERT(nmap == 1);
514 ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
515 (map.br_startblock != HOLESTARTBLOCK));
516
517 dblkno = XFS_FSB_TO_DADDR(mp, map.br_startblock),
518 dblkcnt = XFS_FSB_TO_BB(mp, map.br_blockcount);
519
520 error = xfs_buf_get(mp->m_ddev_targp, dblkno, dblkcnt, &bp);
521 if (error)
522 return error;
523 bp->b_ops = &xfs_attr3_rmt_buf_ops;
524
525 xfs_attr_rmtval_copyin(mp, bp, args->dp->i_ino, &offset,
526 &valuelen, &src);
527
528 error = xfs_bwrite(bp); /* GROT: NOTE: synchronous write */
529 xfs_buf_relse(bp);
530 if (error)
531 return error;
532
533
534 /* roll attribute extent map forwards */
535 lblkno += map.br_blockcount;
536 blkcnt -= map.br_blockcount;
537 }
538 ASSERT(valuelen == 0);
539 return 0;
540}
541
542/* Mark stale any incore buffers for the remote value. */
543int
544xfs_attr_rmtval_stale(
545 struct xfs_inode *ip,
546 struct xfs_bmbt_irec *map,
547 xfs_buf_flags_t incore_flags)
548{
549 struct xfs_mount *mp = ip->i_mount;
550 struct xfs_buf *bp;
551 int error;
552
553 xfs_assert_ilocked(ip, XFS_ILOCK_EXCL);
554
555 if (XFS_IS_CORRUPT(mp, map->br_startblock == DELAYSTARTBLOCK) ||
556 XFS_IS_CORRUPT(mp, map->br_startblock == HOLESTARTBLOCK)) {
557 xfs_bmap_mark_sick(ip, XFS_ATTR_FORK);
558 return -EFSCORRUPTED;
559 }
560
561 error = xfs_buf_incore(mp->m_ddev_targp,
562 XFS_FSB_TO_DADDR(mp, map->br_startblock),
563 XFS_FSB_TO_BB(mp, map->br_blockcount),
564 incore_flags, &bp);
565 if (error) {
566 if (error == -ENOENT)
567 return 0;
568 return error;
569 }
570
571 xfs_buf_stale(bp);
572 xfs_buf_relse(bp);
573 return 0;
574}
575
576/*
577 * Find a hole for the attr and store it in the delayed attr context. This
578 * initializes the context to roll through allocating an attr extent for a
579 * delayed attr operation
580 */
581int
582xfs_attr_rmtval_find_space(
583 struct xfs_attr_intent *attr)
584{
585 struct xfs_da_args *args = attr->xattri_da_args;
586 struct xfs_bmbt_irec *map = &attr->xattri_map;
587 int error;
588
589 attr->xattri_lblkno = 0;
590 attr->xattri_blkcnt = 0;
591 args->rmtblkcnt = 0;
592 args->rmtblkno = 0;
593 memset(map, 0, sizeof(struct xfs_bmbt_irec));
594
595 error = xfs_attr_rmt_find_hole(args);
596 if (error)
597 return error;
598
599 attr->xattri_blkcnt = args->rmtblkcnt;
600 attr->xattri_lblkno = args->rmtblkno;
601
602 return 0;
603}
604
605/*
606 * Write one block of the value associated with an attribute into the
607 * out-of-line buffer that we have defined for it. This is similar to a subset
608 * of xfs_attr_rmtval_set, but records the current block to the delayed attr
609 * context, and leaves transaction handling to the caller.
610 */
611int
612xfs_attr_rmtval_set_blk(
613 struct xfs_attr_intent *attr)
614{
615 struct xfs_da_args *args = attr->xattri_da_args;
616 struct xfs_inode *dp = args->dp;
617 struct xfs_bmbt_irec *map = &attr->xattri_map;
618 int nmap;
619 int error;
620
621 nmap = 1;
622 error = xfs_bmapi_write(args->trans, dp,
623 (xfs_fileoff_t)attr->xattri_lblkno,
624 attr->xattri_blkcnt, XFS_BMAPI_ATTRFORK, args->total,
625 map, &nmap);
626 if (error)
627 return error;
628
629 ASSERT(nmap == 1);
630 ASSERT((map->br_startblock != DELAYSTARTBLOCK) &&
631 (map->br_startblock != HOLESTARTBLOCK));
632
633 /* roll attribute extent map forwards */
634 attr->xattri_lblkno += map->br_blockcount;
635 attr->xattri_blkcnt -= map->br_blockcount;
636
637 return 0;
638}
639
640/*
641 * Remove the value associated with an attribute by deleting the
642 * out-of-line buffer that it is stored on.
643 */
644int
645xfs_attr_rmtval_invalidate(
646 struct xfs_da_args *args)
647{
648 xfs_dablk_t lblkno;
649 int blkcnt;
650 int error;
651
652 /*
653 * Roll through the "value", invalidating the attribute value's blocks.
654 */
655 lblkno = args->rmtblkno;
656 blkcnt = args->rmtblkcnt;
657 while (blkcnt > 0) {
658 struct xfs_bmbt_irec map;
659 int nmap;
660
661 /*
662 * Try to remember where we decided to put the value.
663 */
664 nmap = 1;
665 error = xfs_bmapi_read(args->dp, (xfs_fileoff_t)lblkno,
666 blkcnt, &map, &nmap, XFS_BMAPI_ATTRFORK);
667 if (error)
668 return error;
669 if (XFS_IS_CORRUPT(args->dp->i_mount, nmap != 1)) {
670 xfs_bmap_mark_sick(args->dp, XFS_ATTR_FORK);
671 return -EFSCORRUPTED;
672 }
673 error = xfs_attr_rmtval_stale(args->dp, &map, XBF_TRYLOCK);
674 if (error)
675 return error;
676
677 lblkno += map.br_blockcount;
678 blkcnt -= map.br_blockcount;
679 }
680 return 0;
681}
682
683/*
684 * Remove the value associated with an attribute by deleting the out-of-line
685 * buffer that it is stored on. Returns -EAGAIN for the caller to refresh the
686 * transaction and re-call the function. Callers should keep calling this
687 * routine until it returns something other than -EAGAIN.
688 */
689int
690xfs_attr_rmtval_remove(
691 struct xfs_attr_intent *attr)
692{
693 struct xfs_da_args *args = attr->xattri_da_args;
694 int error, done;
695
696 /*
697 * Unmap value blocks for this attr.
698 */
699 error = xfs_bunmapi(args->trans, args->dp, args->rmtblkno,
700 args->rmtblkcnt, XFS_BMAPI_ATTRFORK, 1, &done);
701 if (error)
702 return error;
703
704 /*
705 * We don't need an explicit state here to pick up where we left off. We
706 * can figure it out using the !done return code. The actual value of
707 * attr->xattri_dela_state may be some value reminiscent of the calling
708 * function, but it's value is irrelevant with in the context of this
709 * function. Once we are done here, the next state is set as needed by
710 * the parent
711 */
712 if (!done) {
713 trace_xfs_attr_rmtval_remove_return(attr->xattri_dela_state,
714 args->dp);
715 return -EAGAIN;
716 }
717
718 args->rmtblkno = 0;
719 args->rmtblkcnt = 0;
720 return 0;
721}
722

source code of linux/fs/xfs/libxfs/xfs_attr_remote.c