xref: /openbmc/linux/fs/xfs/xfs_dir2_readdir.c (revision 161f4089)
1 /*
2  * Copyright (c) 2000-2005 Silicon Graphics, Inc.
3  * Copyright (c) 2013 Red Hat, Inc.
4  * All Rights Reserved.
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License as
8  * published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it would be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program; if not, write the Free Software Foundation,
17  * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
18  */
19 #include "xfs.h"
20 #include "xfs_fs.h"
21 #include "xfs_types.h"
22 #include "xfs_bit.h"
23 #include "xfs_log.h"
24 #include "xfs_trans.h"
25 #include "xfs_sb.h"
26 #include "xfs_ag.h"
27 #include "xfs_mount.h"
28 #include "xfs_da_btree.h"
29 #include "xfs_bmap_btree.h"
30 #include "xfs_dinode.h"
31 #include "xfs_inode.h"
32 #include "xfs_dir2_format.h"
33 #include "xfs_dir2.h"
34 #include "xfs_dir2_priv.h"
35 #include "xfs_error.h"
36 #include "xfs_trace.h"
37 #include "xfs_bmap.h"
38 
39 /*
40  * Directory file type support functions
41  */
42 static unsigned char xfs_dir3_filetype_table[] = {
43 	DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK,
44 	DT_FIFO, DT_SOCK, DT_LNK, DT_WHT,
45 };
46 
47 unsigned char
48 xfs_dir3_get_dtype(
49 	struct xfs_mount	*mp,
50 	__uint8_t		filetype)
51 {
52 	if (!xfs_sb_version_hasftype(&mp->m_sb))
53 		return DT_UNKNOWN;
54 
55 	if (filetype >= XFS_DIR3_FT_MAX)
56 		return DT_UNKNOWN;
57 
58 	return xfs_dir3_filetype_table[filetype];
59 }
60 /*
61  * @mode, if set, indicates that the type field needs to be set up.
62  * This uses the transformation from file mode to DT_* as defined in linux/fs.h
63  * for file type specification. This will be propagated into the directory
64  * structure if appropriate for the given operation and filesystem config.
65  */
66 const unsigned char xfs_mode_to_ftype[S_IFMT >> S_SHIFT] = {
67 	[0]			= XFS_DIR3_FT_UNKNOWN,
68 	[S_IFREG >> S_SHIFT]    = XFS_DIR3_FT_REG_FILE,
69 	[S_IFDIR >> S_SHIFT]    = XFS_DIR3_FT_DIR,
70 	[S_IFCHR >> S_SHIFT]    = XFS_DIR3_FT_CHRDEV,
71 	[S_IFBLK >> S_SHIFT]    = XFS_DIR3_FT_BLKDEV,
72 	[S_IFIFO >> S_SHIFT]    = XFS_DIR3_FT_FIFO,
73 	[S_IFSOCK >> S_SHIFT]   = XFS_DIR3_FT_SOCK,
74 	[S_IFLNK >> S_SHIFT]    = XFS_DIR3_FT_SYMLINK,
75 };
76 
77 STATIC int
78 xfs_dir2_sf_getdents(
79 	xfs_inode_t		*dp,		/* incore directory inode */
80 	struct dir_context	*ctx)
81 {
82 	int			i;		/* shortform entry number */
83 	xfs_mount_t		*mp;		/* filesystem mount point */
84 	xfs_dir2_dataptr_t	off;		/* current entry's offset */
85 	xfs_dir2_sf_entry_t	*sfep;		/* shortform directory entry */
86 	xfs_dir2_sf_hdr_t	*sfp;		/* shortform structure */
87 	xfs_dir2_dataptr_t	dot_offset;
88 	xfs_dir2_dataptr_t	dotdot_offset;
89 	xfs_ino_t		ino;
90 
91 	mp = dp->i_mount;
92 
93 	ASSERT(dp->i_df.if_flags & XFS_IFINLINE);
94 	/*
95 	 * Give up if the directory is way too short.
96 	 */
97 	if (dp->i_d.di_size < offsetof(xfs_dir2_sf_hdr_t, parent)) {
98 		ASSERT(XFS_FORCED_SHUTDOWN(mp));
99 		return XFS_ERROR(EIO);
100 	}
101 
102 	ASSERT(dp->i_df.if_bytes == dp->i_d.di_size);
103 	ASSERT(dp->i_df.if_u1.if_data != NULL);
104 
105 	sfp = (xfs_dir2_sf_hdr_t *)dp->i_df.if_u1.if_data;
106 
107 	ASSERT(dp->i_d.di_size >= xfs_dir2_sf_hdr_size(sfp->i8count));
108 
109 	/*
110 	 * If the block number in the offset is out of range, we're done.
111 	 */
112 	if (xfs_dir2_dataptr_to_db(mp, ctx->pos) > mp->m_dirdatablk)
113 		return 0;
114 
115 	/*
116 	 * Precalculate offsets for . and .. as we will always need them.
117 	 *
118 	 * XXX(hch): the second argument is sometimes 0 and sometimes
119 	 * mp->m_dirdatablk.
120 	 */
121 	dot_offset = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk,
122 					     xfs_dir3_data_dot_offset(mp));
123 	dotdot_offset = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk,
124 						xfs_dir3_data_dotdot_offset(mp));
125 
126 	/*
127 	 * Put . entry unless we're starting past it.
128 	 */
129 	if (ctx->pos <= dot_offset) {
130 		ctx->pos = dot_offset & 0x7fffffff;
131 		if (!dir_emit(ctx, ".", 1, dp->i_ino, DT_DIR))
132 			return 0;
133 	}
134 
135 	/*
136 	 * Put .. entry unless we're starting past it.
137 	 */
138 	if (ctx->pos <= dotdot_offset) {
139 		ino = xfs_dir2_sf_get_parent_ino(sfp);
140 		ctx->pos = dotdot_offset & 0x7fffffff;
141 		if (!dir_emit(ctx, "..", 2, ino, DT_DIR))
142 			return 0;
143 	}
144 
145 	/*
146 	 * Loop while there are more entries and put'ing works.
147 	 */
148 	sfep = xfs_dir2_sf_firstentry(sfp);
149 	for (i = 0; i < sfp->count; i++) {
150 		__uint8_t filetype;
151 
152 		off = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk,
153 				xfs_dir2_sf_get_offset(sfep));
154 
155 		if (ctx->pos > off) {
156 			sfep = xfs_dir3_sf_nextentry(mp, sfp, sfep);
157 			continue;
158 		}
159 
160 		ino = xfs_dir3_sfe_get_ino(mp, sfp, sfep);
161 		filetype = xfs_dir3_sfe_get_ftype(mp, sfp, sfep);
162 		ctx->pos = off & 0x7fffffff;
163 		if (!dir_emit(ctx, (char *)sfep->name, sfep->namelen, ino,
164 			    xfs_dir3_get_dtype(mp, filetype)))
165 			return 0;
166 		sfep = xfs_dir3_sf_nextentry(mp, sfp, sfep);
167 	}
168 
169 	ctx->pos = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk + 1, 0) &
170 			0x7fffffff;
171 	return 0;
172 }
173 
174 /*
175  * Readdir for block directories.
176  */
177 STATIC int
178 xfs_dir2_block_getdents(
179 	xfs_inode_t		*dp,		/* incore inode */
180 	struct dir_context	*ctx)
181 {
182 	xfs_dir2_data_hdr_t	*hdr;		/* block header */
183 	struct xfs_buf		*bp;		/* buffer for block */
184 	xfs_dir2_block_tail_t	*btp;		/* block tail */
185 	xfs_dir2_data_entry_t	*dep;		/* block data entry */
186 	xfs_dir2_data_unused_t	*dup;		/* block unused entry */
187 	char			*endptr;	/* end of the data entries */
188 	int			error;		/* error return value */
189 	xfs_mount_t		*mp;		/* filesystem mount point */
190 	char			*ptr;		/* current data entry */
191 	int			wantoff;	/* starting block offset */
192 	xfs_off_t		cook;
193 
194 	mp = dp->i_mount;
195 	/*
196 	 * If the block number in the offset is out of range, we're done.
197 	 */
198 	if (xfs_dir2_dataptr_to_db(mp, ctx->pos) > mp->m_dirdatablk)
199 		return 0;
200 
201 	error = xfs_dir3_block_read(NULL, dp, &bp);
202 	if (error)
203 		return error;
204 
205 	/*
206 	 * Extract the byte offset we start at from the seek pointer.
207 	 * We'll skip entries before this.
208 	 */
209 	wantoff = xfs_dir2_dataptr_to_off(mp, ctx->pos);
210 	hdr = bp->b_addr;
211 	xfs_dir3_data_check(dp, bp);
212 	/*
213 	 * Set up values for the loop.
214 	 */
215 	btp = xfs_dir2_block_tail_p(mp, hdr);
216 	ptr = (char *)xfs_dir3_data_entry_p(hdr);
217 	endptr = (char *)xfs_dir2_block_leaf_p(btp);
218 
219 	/*
220 	 * Loop over the data portion of the block.
221 	 * Each object is a real entry (dep) or an unused one (dup).
222 	 */
223 	while (ptr < endptr) {
224 		__uint8_t filetype;
225 
226 		dup = (xfs_dir2_data_unused_t *)ptr;
227 		/*
228 		 * Unused, skip it.
229 		 */
230 		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
231 			ptr += be16_to_cpu(dup->length);
232 			continue;
233 		}
234 
235 		dep = (xfs_dir2_data_entry_t *)ptr;
236 
237 		/*
238 		 * Bump pointer for the next iteration.
239 		 */
240 		ptr += xfs_dir3_data_entsize(mp, dep->namelen);
241 		/*
242 		 * The entry is before the desired starting point, skip it.
243 		 */
244 		if ((char *)dep - (char *)hdr < wantoff)
245 			continue;
246 
247 		cook = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk,
248 					    (char *)dep - (char *)hdr);
249 
250 		ctx->pos = cook & 0x7fffffff;
251 		filetype = xfs_dir3_dirent_get_ftype(mp, dep);
252 		/*
253 		 * If it didn't fit, set the final offset to here & return.
254 		 */
255 		if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
256 			    be64_to_cpu(dep->inumber),
257 			    xfs_dir3_get_dtype(mp, filetype))) {
258 			xfs_trans_brelse(NULL, bp);
259 			return 0;
260 		}
261 	}
262 
263 	/*
264 	 * Reached the end of the block.
265 	 * Set the offset to a non-existent block 1 and return.
266 	 */
267 	ctx->pos = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk + 1, 0) &
268 			0x7fffffff;
269 	xfs_trans_brelse(NULL, bp);
270 	return 0;
271 }
272 
273 struct xfs_dir2_leaf_map_info {
274 	xfs_extlen_t	map_blocks;	/* number of fsbs in map */
275 	xfs_dablk_t	map_off;	/* last mapped file offset */
276 	int		map_size;	/* total entries in *map */
277 	int		map_valid;	/* valid entries in *map */
278 	int		nmap;		/* mappings to ask xfs_bmapi */
279 	xfs_dir2_db_t	curdb;		/* db for current block */
280 	int		ra_current;	/* number of read-ahead blks */
281 	int		ra_index;	/* *map index for read-ahead */
282 	int		ra_offset;	/* map entry offset for ra */
283 	int		ra_want;	/* readahead count wanted */
284 	struct xfs_bmbt_irec map[];	/* map vector for blocks */
285 };
286 
287 STATIC int
288 xfs_dir2_leaf_readbuf(
289 	struct xfs_inode	*dp,
290 	size_t			bufsize,
291 	struct xfs_dir2_leaf_map_info *mip,
292 	xfs_dir2_off_t		*curoff,
293 	struct xfs_buf		**bpp)
294 {
295 	struct xfs_mount	*mp = dp->i_mount;
296 	struct xfs_buf		*bp = *bpp;
297 	struct xfs_bmbt_irec	*map = mip->map;
298 	struct blk_plug		plug;
299 	int			error = 0;
300 	int			length;
301 	int			i;
302 	int			j;
303 
304 	/*
305 	 * If we have a buffer, we need to release it and
306 	 * take it out of the mapping.
307 	 */
308 
309 	if (bp) {
310 		xfs_trans_brelse(NULL, bp);
311 		bp = NULL;
312 		mip->map_blocks -= mp->m_dirblkfsbs;
313 		/*
314 		 * Loop to get rid of the extents for the
315 		 * directory block.
316 		 */
317 		for (i = mp->m_dirblkfsbs; i > 0; ) {
318 			j = min_t(int, map->br_blockcount, i);
319 			map->br_blockcount -= j;
320 			map->br_startblock += j;
321 			map->br_startoff += j;
322 			/*
323 			 * If mapping is done, pitch it from
324 			 * the table.
325 			 */
326 			if (!map->br_blockcount && --mip->map_valid)
327 				memmove(&map[0], &map[1],
328 					sizeof(map[0]) * mip->map_valid);
329 			i -= j;
330 		}
331 	}
332 
333 	/*
334 	 * Recalculate the readahead blocks wanted.
335 	 */
336 	mip->ra_want = howmany(bufsize + mp->m_dirblksize,
337 			       mp->m_sb.sb_blocksize) - 1;
338 	ASSERT(mip->ra_want >= 0);
339 
340 	/*
341 	 * If we don't have as many as we want, and we haven't
342 	 * run out of data blocks, get some more mappings.
343 	 */
344 	if (1 + mip->ra_want > mip->map_blocks &&
345 	    mip->map_off < xfs_dir2_byte_to_da(mp, XFS_DIR2_LEAF_OFFSET)) {
346 		/*
347 		 * Get more bmaps, fill in after the ones
348 		 * we already have in the table.
349 		 */
350 		mip->nmap = mip->map_size - mip->map_valid;
351 		error = xfs_bmapi_read(dp, mip->map_off,
352 				xfs_dir2_byte_to_da(mp, XFS_DIR2_LEAF_OFFSET) -
353 								mip->map_off,
354 				&map[mip->map_valid], &mip->nmap, 0);
355 
356 		/*
357 		 * Don't know if we should ignore this or try to return an
358 		 * error.  The trouble with returning errors is that readdir
359 		 * will just stop without actually passing the error through.
360 		 */
361 		if (error)
362 			goto out;	/* XXX */
363 
364 		/*
365 		 * If we got all the mappings we asked for, set the final map
366 		 * offset based on the last bmap value received.  Otherwise,
367 		 * we've reached the end.
368 		 */
369 		if (mip->nmap == mip->map_size - mip->map_valid) {
370 			i = mip->map_valid + mip->nmap - 1;
371 			mip->map_off = map[i].br_startoff + map[i].br_blockcount;
372 		} else
373 			mip->map_off = xfs_dir2_byte_to_da(mp,
374 							XFS_DIR2_LEAF_OFFSET);
375 
376 		/*
377 		 * Look for holes in the mapping, and eliminate them.  Count up
378 		 * the valid blocks.
379 		 */
380 		for (i = mip->map_valid; i < mip->map_valid + mip->nmap; ) {
381 			if (map[i].br_startblock == HOLESTARTBLOCK) {
382 				mip->nmap--;
383 				length = mip->map_valid + mip->nmap - i;
384 				if (length)
385 					memmove(&map[i], &map[i + 1],
386 						sizeof(map[i]) * length);
387 			} else {
388 				mip->map_blocks += map[i].br_blockcount;
389 				i++;
390 			}
391 		}
392 		mip->map_valid += mip->nmap;
393 	}
394 
395 	/*
396 	 * No valid mappings, so no more data blocks.
397 	 */
398 	if (!mip->map_valid) {
399 		*curoff = xfs_dir2_da_to_byte(mp, mip->map_off);
400 		goto out;
401 	}
402 
403 	/*
404 	 * Read the directory block starting at the first mapping.
405 	 */
406 	mip->curdb = xfs_dir2_da_to_db(mp, map->br_startoff);
407 	error = xfs_dir3_data_read(NULL, dp, map->br_startoff,
408 			map->br_blockcount >= mp->m_dirblkfsbs ?
409 			    XFS_FSB_TO_DADDR(mp, map->br_startblock) : -1, &bp);
410 
411 	/*
412 	 * Should just skip over the data block instead of giving up.
413 	 */
414 	if (error)
415 		goto out;	/* XXX */
416 
417 	/*
418 	 * Adjust the current amount of read-ahead: we just read a block that
419 	 * was previously ra.
420 	 */
421 	if (mip->ra_current)
422 		mip->ra_current -= mp->m_dirblkfsbs;
423 
424 	/*
425 	 * Do we need more readahead?
426 	 */
427 	blk_start_plug(&plug);
428 	for (mip->ra_index = mip->ra_offset = i = 0;
429 	     mip->ra_want > mip->ra_current && i < mip->map_blocks;
430 	     i += mp->m_dirblkfsbs) {
431 		ASSERT(mip->ra_index < mip->map_valid);
432 		/*
433 		 * Read-ahead a contiguous directory block.
434 		 */
435 		if (i > mip->ra_current &&
436 		    map[mip->ra_index].br_blockcount >= mp->m_dirblkfsbs) {
437 			xfs_dir3_data_readahead(NULL, dp,
438 				map[mip->ra_index].br_startoff + mip->ra_offset,
439 				XFS_FSB_TO_DADDR(mp,
440 					map[mip->ra_index].br_startblock +
441 							mip->ra_offset));
442 			mip->ra_current = i;
443 		}
444 
445 		/*
446 		 * Read-ahead a non-contiguous directory block.  This doesn't
447 		 * use our mapping, but this is a very rare case.
448 		 */
449 		else if (i > mip->ra_current) {
450 			xfs_dir3_data_readahead(NULL, dp,
451 					map[mip->ra_index].br_startoff +
452 							mip->ra_offset, -1);
453 			mip->ra_current = i;
454 		}
455 
456 		/*
457 		 * Advance offset through the mapping table.
458 		 */
459 		for (j = 0; j < mp->m_dirblkfsbs; j++) {
460 			/*
461 			 * The rest of this extent but not more than a dir
462 			 * block.
463 			 */
464 			length = min_t(int, mp->m_dirblkfsbs,
465 					map[mip->ra_index].br_blockcount -
466 							mip->ra_offset);
467 			j += length;
468 			mip->ra_offset += length;
469 
470 			/*
471 			 * Advance to the next mapping if this one is used up.
472 			 */
473 			if (mip->ra_offset == map[mip->ra_index].br_blockcount) {
474 				mip->ra_offset = 0;
475 				mip->ra_index++;
476 			}
477 		}
478 	}
479 	blk_finish_plug(&plug);
480 
481 out:
482 	*bpp = bp;
483 	return error;
484 }
485 
486 /*
487  * Getdents (readdir) for leaf and node directories.
488  * This reads the data blocks only, so is the same for both forms.
489  */
490 STATIC int
491 xfs_dir2_leaf_getdents(
492 	xfs_inode_t		*dp,		/* incore directory inode */
493 	struct dir_context	*ctx,
494 	size_t			bufsize)
495 {
496 	struct xfs_buf		*bp = NULL;	/* data block buffer */
497 	xfs_dir2_data_hdr_t	*hdr;		/* data block header */
498 	xfs_dir2_data_entry_t	*dep;		/* data entry */
499 	xfs_dir2_data_unused_t	*dup;		/* unused entry */
500 	int			error = 0;	/* error return value */
501 	int			length;		/* temporary length value */
502 	xfs_mount_t		*mp;		/* filesystem mount point */
503 	int			byteoff;	/* offset in current block */
504 	xfs_dir2_off_t		curoff;		/* current overall offset */
505 	xfs_dir2_off_t		newoff;		/* new curoff after new blk */
506 	char			*ptr = NULL;	/* pointer to current data */
507 	struct xfs_dir2_leaf_map_info *map_info;
508 
509 	/*
510 	 * If the offset is at or past the largest allowed value,
511 	 * give up right away.
512 	 */
513 	if (ctx->pos >= XFS_DIR2_MAX_DATAPTR)
514 		return 0;
515 
516 	mp = dp->i_mount;
517 
518 	/*
519 	 * Set up to bmap a number of blocks based on the caller's
520 	 * buffer size, the directory block size, and the filesystem
521 	 * block size.
522 	 */
523 	length = howmany(bufsize + mp->m_dirblksize,
524 				     mp->m_sb.sb_blocksize);
525 	map_info = kmem_zalloc(offsetof(struct xfs_dir2_leaf_map_info, map) +
526 				(length * sizeof(struct xfs_bmbt_irec)),
527 			       KM_SLEEP | KM_NOFS);
528 	map_info->map_size = length;
529 
530 	/*
531 	 * Inside the loop we keep the main offset value as a byte offset
532 	 * in the directory file.
533 	 */
534 	curoff = xfs_dir2_dataptr_to_byte(mp, ctx->pos);
535 
536 	/*
537 	 * Force this conversion through db so we truncate the offset
538 	 * down to get the start of the data block.
539 	 */
540 	map_info->map_off = xfs_dir2_db_to_da(mp,
541 					      xfs_dir2_byte_to_db(mp, curoff));
542 
543 	/*
544 	 * Loop over directory entries until we reach the end offset.
545 	 * Get more blocks and readahead as necessary.
546 	 */
547 	while (curoff < XFS_DIR2_LEAF_OFFSET) {
548 		__uint8_t filetype;
549 
550 		/*
551 		 * If we have no buffer, or we're off the end of the
552 		 * current buffer, need to get another one.
553 		 */
554 		if (!bp || ptr >= (char *)bp->b_addr + mp->m_dirblksize) {
555 
556 			error = xfs_dir2_leaf_readbuf(dp, bufsize, map_info,
557 						      &curoff, &bp);
558 			if (error || !map_info->map_valid)
559 				break;
560 
561 			/*
562 			 * Having done a read, we need to set a new offset.
563 			 */
564 			newoff = xfs_dir2_db_off_to_byte(mp, map_info->curdb, 0);
565 			/*
566 			 * Start of the current block.
567 			 */
568 			if (curoff < newoff)
569 				curoff = newoff;
570 			/*
571 			 * Make sure we're in the right block.
572 			 */
573 			else if (curoff > newoff)
574 				ASSERT(xfs_dir2_byte_to_db(mp, curoff) ==
575 				       map_info->curdb);
576 			hdr = bp->b_addr;
577 			xfs_dir3_data_check(dp, bp);
578 			/*
579 			 * Find our position in the block.
580 			 */
581 			ptr = (char *)xfs_dir3_data_entry_p(hdr);
582 			byteoff = xfs_dir2_byte_to_off(mp, curoff);
583 			/*
584 			 * Skip past the header.
585 			 */
586 			if (byteoff == 0)
587 				curoff += xfs_dir3_data_entry_offset(hdr);
588 			/*
589 			 * Skip past entries until we reach our offset.
590 			 */
591 			else {
592 				while ((char *)ptr - (char *)hdr < byteoff) {
593 					dup = (xfs_dir2_data_unused_t *)ptr;
594 
595 					if (be16_to_cpu(dup->freetag)
596 						  == XFS_DIR2_DATA_FREE_TAG) {
597 
598 						length = be16_to_cpu(dup->length);
599 						ptr += length;
600 						continue;
601 					}
602 					dep = (xfs_dir2_data_entry_t *)ptr;
603 					length =
604 					   xfs_dir3_data_entsize(mp, dep->namelen);
605 					ptr += length;
606 				}
607 				/*
608 				 * Now set our real offset.
609 				 */
610 				curoff =
611 					xfs_dir2_db_off_to_byte(mp,
612 					    xfs_dir2_byte_to_db(mp, curoff),
613 					    (char *)ptr - (char *)hdr);
614 				if (ptr >= (char *)hdr + mp->m_dirblksize) {
615 					continue;
616 				}
617 			}
618 		}
619 		/*
620 		 * We have a pointer to an entry.
621 		 * Is it a live one?
622 		 */
623 		dup = (xfs_dir2_data_unused_t *)ptr;
624 		/*
625 		 * No, it's unused, skip over it.
626 		 */
627 		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
628 			length = be16_to_cpu(dup->length);
629 			ptr += length;
630 			curoff += length;
631 			continue;
632 		}
633 
634 		dep = (xfs_dir2_data_entry_t *)ptr;
635 		length = xfs_dir3_data_entsize(mp, dep->namelen);
636 		filetype = xfs_dir3_dirent_get_ftype(mp, dep);
637 
638 		ctx->pos = xfs_dir2_byte_to_dataptr(mp, curoff) & 0x7fffffff;
639 		if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
640 			    be64_to_cpu(dep->inumber),
641 			    xfs_dir3_get_dtype(mp, filetype)))
642 			break;
643 
644 		/*
645 		 * Advance to next entry in the block.
646 		 */
647 		ptr += length;
648 		curoff += length;
649 		/* bufsize may have just been a guess; don't go negative */
650 		bufsize = bufsize > length ? bufsize - length : 0;
651 	}
652 
653 	/*
654 	 * All done.  Set output offset value to current offset.
655 	 */
656 	if (curoff > xfs_dir2_dataptr_to_byte(mp, XFS_DIR2_MAX_DATAPTR))
657 		ctx->pos = XFS_DIR2_MAX_DATAPTR & 0x7fffffff;
658 	else
659 		ctx->pos = xfs_dir2_byte_to_dataptr(mp, curoff) & 0x7fffffff;
660 	kmem_free(map_info);
661 	if (bp)
662 		xfs_trans_brelse(NULL, bp);
663 	return error;
664 }
665 
666 /*
667  * Read a directory.
668  */
669 int
670 xfs_readdir(
671 	xfs_inode_t	*dp,
672 	struct dir_context *ctx,
673 	size_t		bufsize)
674 {
675 	int		rval;		/* return value */
676 	int		v;		/* type-checking value */
677 
678 	trace_xfs_readdir(dp);
679 
680 	if (XFS_FORCED_SHUTDOWN(dp->i_mount))
681 		return XFS_ERROR(EIO);
682 
683 	ASSERT(S_ISDIR(dp->i_d.di_mode));
684 	XFS_STATS_INC(xs_dir_getdents);
685 
686 	if (dp->i_d.di_format == XFS_DINODE_FMT_LOCAL)
687 		rval = xfs_dir2_sf_getdents(dp, ctx);
688 	else if ((rval = xfs_dir2_isblock(NULL, dp, &v)))
689 		;
690 	else if (v)
691 		rval = xfs_dir2_block_getdents(dp, ctx);
692 	else
693 		rval = xfs_dir2_leaf_getdents(dp, ctx, bufsize);
694 	return rval;
695 }
696