xref: /openbmc/linux/fs/xfs/xfs_dir2_readdir.c (revision 68198dca)
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_format.h"
22 #include "xfs_log_format.h"
23 #include "xfs_trans_resv.h"
24 #include "xfs_bit.h"
25 #include "xfs_mount.h"
26 #include "xfs_da_format.h"
27 #include "xfs_da_btree.h"
28 #include "xfs_inode.h"
29 #include "xfs_dir2.h"
30 #include "xfs_dir2_priv.h"
31 #include "xfs_error.h"
32 #include "xfs_trace.h"
33 #include "xfs_bmap.h"
34 #include "xfs_trans.h"
35 
36 /*
37  * Directory file type support functions
38  */
39 static unsigned char xfs_dir3_filetype_table[] = {
40 	DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK,
41 	DT_FIFO, DT_SOCK, DT_LNK, DT_WHT,
42 };
43 
44 unsigned char
45 xfs_dir3_get_dtype(
46 	struct xfs_mount	*mp,
47 	uint8_t			filetype)
48 {
49 	if (!xfs_sb_version_hasftype(&mp->m_sb))
50 		return DT_UNKNOWN;
51 
52 	if (filetype >= XFS_DIR3_FT_MAX)
53 		return DT_UNKNOWN;
54 
55 	return xfs_dir3_filetype_table[filetype];
56 }
57 
58 STATIC int
59 xfs_dir2_sf_getdents(
60 	struct xfs_da_args	*args,
61 	struct dir_context	*ctx)
62 {
63 	int			i;		/* shortform entry number */
64 	struct xfs_inode	*dp = args->dp;	/* incore directory inode */
65 	xfs_dir2_dataptr_t	off;		/* current entry's offset */
66 	xfs_dir2_sf_entry_t	*sfep;		/* shortform directory entry */
67 	xfs_dir2_sf_hdr_t	*sfp;		/* shortform structure */
68 	xfs_dir2_dataptr_t	dot_offset;
69 	xfs_dir2_dataptr_t	dotdot_offset;
70 	xfs_ino_t		ino;
71 	struct xfs_da_geometry	*geo = args->geo;
72 
73 	ASSERT(dp->i_df.if_flags & XFS_IFINLINE);
74 	ASSERT(dp->i_df.if_bytes == dp->i_d.di_size);
75 	ASSERT(dp->i_df.if_u1.if_data != NULL);
76 
77 	sfp = (xfs_dir2_sf_hdr_t *)dp->i_df.if_u1.if_data;
78 
79 	/*
80 	 * If the block number in the offset is out of range, we're done.
81 	 */
82 	if (xfs_dir2_dataptr_to_db(geo, ctx->pos) > geo->datablk)
83 		return 0;
84 
85 	/*
86 	 * Precalculate offsets for . and .. as we will always need them.
87 	 *
88 	 * XXX(hch): the second argument is sometimes 0 and sometimes
89 	 * geo->datablk
90 	 */
91 	dot_offset = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
92 						dp->d_ops->data_dot_offset);
93 	dotdot_offset = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
94 						dp->d_ops->data_dotdot_offset);
95 
96 	/*
97 	 * Put . entry unless we're starting past it.
98 	 */
99 	if (ctx->pos <= dot_offset) {
100 		ctx->pos = dot_offset & 0x7fffffff;
101 		if (!dir_emit(ctx, ".", 1, dp->i_ino, DT_DIR))
102 			return 0;
103 	}
104 
105 	/*
106 	 * Put .. entry unless we're starting past it.
107 	 */
108 	if (ctx->pos <= dotdot_offset) {
109 		ino = dp->d_ops->sf_get_parent_ino(sfp);
110 		ctx->pos = dotdot_offset & 0x7fffffff;
111 		if (!dir_emit(ctx, "..", 2, ino, DT_DIR))
112 			return 0;
113 	}
114 
115 	/*
116 	 * Loop while there are more entries and put'ing works.
117 	 */
118 	sfep = xfs_dir2_sf_firstentry(sfp);
119 	for (i = 0; i < sfp->count; i++) {
120 		uint8_t filetype;
121 
122 		off = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
123 				xfs_dir2_sf_get_offset(sfep));
124 
125 		if (ctx->pos > off) {
126 			sfep = dp->d_ops->sf_nextentry(sfp, sfep);
127 			continue;
128 		}
129 
130 		ino = dp->d_ops->sf_get_ino(sfp, sfep);
131 		filetype = dp->d_ops->sf_get_ftype(sfep);
132 		ctx->pos = off & 0x7fffffff;
133 		if (!dir_emit(ctx, (char *)sfep->name, sfep->namelen, ino,
134 			    xfs_dir3_get_dtype(dp->i_mount, filetype)))
135 			return 0;
136 		sfep = dp->d_ops->sf_nextentry(sfp, sfep);
137 	}
138 
139 	ctx->pos = xfs_dir2_db_off_to_dataptr(geo, geo->datablk + 1, 0) &
140 								0x7fffffff;
141 	return 0;
142 }
143 
144 /*
145  * Readdir for block directories.
146  */
147 STATIC int
148 xfs_dir2_block_getdents(
149 	struct xfs_da_args	*args,
150 	struct dir_context	*ctx)
151 {
152 	struct xfs_inode	*dp = args->dp;	/* incore directory inode */
153 	xfs_dir2_data_hdr_t	*hdr;		/* block header */
154 	struct xfs_buf		*bp;		/* buffer for block */
155 	xfs_dir2_block_tail_t	*btp;		/* block tail */
156 	xfs_dir2_data_entry_t	*dep;		/* block data entry */
157 	xfs_dir2_data_unused_t	*dup;		/* block unused entry */
158 	char			*endptr;	/* end of the data entries */
159 	int			error;		/* error return value */
160 	char			*ptr;		/* current data entry */
161 	int			wantoff;	/* starting block offset */
162 	xfs_off_t		cook;
163 	struct xfs_da_geometry	*geo = args->geo;
164 	int			lock_mode;
165 
166 	/*
167 	 * If the block number in the offset is out of range, we're done.
168 	 */
169 	if (xfs_dir2_dataptr_to_db(geo, ctx->pos) > geo->datablk)
170 		return 0;
171 
172 	lock_mode = xfs_ilock_data_map_shared(dp);
173 	error = xfs_dir3_block_read(args->trans, dp, &bp);
174 	xfs_iunlock(dp, lock_mode);
175 	if (error)
176 		return error;
177 
178 	/*
179 	 * Extract the byte offset we start at from the seek pointer.
180 	 * We'll skip entries before this.
181 	 */
182 	wantoff = xfs_dir2_dataptr_to_off(geo, ctx->pos);
183 	hdr = bp->b_addr;
184 	xfs_dir3_data_check(dp, bp);
185 	/*
186 	 * Set up values for the loop.
187 	 */
188 	btp = xfs_dir2_block_tail_p(geo, hdr);
189 	ptr = (char *)dp->d_ops->data_entry_p(hdr);
190 	endptr = (char *)xfs_dir2_block_leaf_p(btp);
191 
192 	/*
193 	 * Loop over the data portion of the block.
194 	 * Each object is a real entry (dep) or an unused one (dup).
195 	 */
196 	while (ptr < endptr) {
197 		uint8_t filetype;
198 
199 		dup = (xfs_dir2_data_unused_t *)ptr;
200 		/*
201 		 * Unused, skip it.
202 		 */
203 		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
204 			ptr += be16_to_cpu(dup->length);
205 			continue;
206 		}
207 
208 		dep = (xfs_dir2_data_entry_t *)ptr;
209 
210 		/*
211 		 * Bump pointer for the next iteration.
212 		 */
213 		ptr += dp->d_ops->data_entsize(dep->namelen);
214 		/*
215 		 * The entry is before the desired starting point, skip it.
216 		 */
217 		if ((char *)dep - (char *)hdr < wantoff)
218 			continue;
219 
220 		cook = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
221 					    (char *)dep - (char *)hdr);
222 
223 		ctx->pos = cook & 0x7fffffff;
224 		filetype = dp->d_ops->data_get_ftype(dep);
225 		/*
226 		 * If it didn't fit, set the final offset to here & return.
227 		 */
228 		if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
229 			    be64_to_cpu(dep->inumber),
230 			    xfs_dir3_get_dtype(dp->i_mount, filetype))) {
231 			xfs_trans_brelse(args->trans, bp);
232 			return 0;
233 		}
234 	}
235 
236 	/*
237 	 * Reached the end of the block.
238 	 * Set the offset to a non-existent block 1 and return.
239 	 */
240 	ctx->pos = xfs_dir2_db_off_to_dataptr(geo, geo->datablk + 1, 0) &
241 								0x7fffffff;
242 	xfs_trans_brelse(args->trans, bp);
243 	return 0;
244 }
245 
246 /*
247  * Read a directory block and initiate readahead for blocks beyond that.
248  * We maintain a sliding readahead window of the remaining space in the
249  * buffer rounded up to the nearest block.
250  */
251 STATIC int
252 xfs_dir2_leaf_readbuf(
253 	struct xfs_da_args	*args,
254 	size_t			bufsize,
255 	xfs_dir2_off_t		*cur_off,
256 	xfs_dablk_t		*ra_blk,
257 	struct xfs_buf		**bpp)
258 {
259 	struct xfs_inode	*dp = args->dp;
260 	struct xfs_buf		*bp = NULL;
261 	struct xfs_da_geometry	*geo = args->geo;
262 	struct xfs_ifork	*ifp = XFS_IFORK_PTR(dp, XFS_DATA_FORK);
263 	struct xfs_bmbt_irec	map;
264 	struct blk_plug		plug;
265 	xfs_dir2_off_t		new_off;
266 	xfs_dablk_t		next_ra;
267 	xfs_dablk_t		map_off;
268 	xfs_dablk_t		last_da;
269 	struct xfs_iext_cursor	icur;
270 	int			ra_want;
271 	int			error = 0;
272 
273 	if (!(ifp->if_flags & XFS_IFEXTENTS)) {
274 		error = xfs_iread_extents(args->trans, dp, XFS_DATA_FORK);
275 		if (error)
276 			goto out;
277 	}
278 
279 	/*
280 	 * Look for mapped directory blocks at or above the current offset.
281 	 * Truncate down to the nearest directory block to start the scanning
282 	 * operation.
283 	 */
284 	last_da = xfs_dir2_byte_to_da(geo, XFS_DIR2_LEAF_OFFSET);
285 	map_off = xfs_dir2_db_to_da(geo, xfs_dir2_byte_to_db(geo, *cur_off));
286 	if (!xfs_iext_lookup_extent(dp, ifp, map_off, &icur, &map))
287 		goto out;
288 	if (map.br_startoff >= last_da)
289 		goto out;
290 	xfs_trim_extent(&map, map_off, last_da - map_off);
291 
292 	/* Read the directory block of that first mapping. */
293 	new_off = xfs_dir2_da_to_byte(geo, map.br_startoff);
294 	if (new_off > *cur_off)
295 		*cur_off = new_off;
296 	error = xfs_dir3_data_read(args->trans, dp, map.br_startoff, -1, &bp);
297 	if (error)
298 		goto out;
299 
300 	/*
301 	 * Start readahead for the next bufsize's worth of dir data blocks.
302 	 * We may have already issued readahead for some of that range;
303 	 * ra_blk tracks the last block we tried to read(ahead).
304 	 */
305 	ra_want = howmany(bufsize + geo->blksize, (1 << geo->fsblog));
306 	if (*ra_blk >= last_da)
307 		goto out;
308 	else if (*ra_blk == 0)
309 		*ra_blk = map.br_startoff;
310 	next_ra = map.br_startoff + geo->fsbcount;
311 	if (next_ra >= last_da)
312 		goto out_no_ra;
313 	if (map.br_blockcount < geo->fsbcount &&
314 	    !xfs_iext_next_extent(ifp, &icur, &map))
315 		goto out_no_ra;
316 	if (map.br_startoff >= last_da)
317 		goto out_no_ra;
318 	xfs_trim_extent(&map, next_ra, last_da - next_ra);
319 
320 	/* Start ra for each dir (not fs) block that has a mapping. */
321 	blk_start_plug(&plug);
322 	while (ra_want > 0) {
323 		next_ra = roundup((xfs_dablk_t)map.br_startoff, geo->fsbcount);
324 		while (ra_want > 0 &&
325 		       next_ra < map.br_startoff + map.br_blockcount) {
326 			if (next_ra >= last_da) {
327 				*ra_blk = last_da;
328 				break;
329 			}
330 			if (next_ra > *ra_blk) {
331 				xfs_dir3_data_readahead(dp, next_ra, -2);
332 				*ra_blk = next_ra;
333 			}
334 			ra_want -= geo->fsbcount;
335 			next_ra += geo->fsbcount;
336 		}
337 		if (!xfs_iext_next_extent(ifp, &icur, &map)) {
338 			*ra_blk = last_da;
339 			break;
340 		}
341 	}
342 	blk_finish_plug(&plug);
343 
344 out:
345 	*bpp = bp;
346 	return error;
347 out_no_ra:
348 	*ra_blk = last_da;
349 	goto out;
350 }
351 
352 /*
353  * Getdents (readdir) for leaf and node directories.
354  * This reads the data blocks only, so is the same for both forms.
355  */
356 STATIC int
357 xfs_dir2_leaf_getdents(
358 	struct xfs_da_args	*args,
359 	struct dir_context	*ctx,
360 	size_t			bufsize)
361 {
362 	struct xfs_inode	*dp = args->dp;
363 	struct xfs_buf		*bp = NULL;	/* data block buffer */
364 	xfs_dir2_data_hdr_t	*hdr;		/* data block header */
365 	xfs_dir2_data_entry_t	*dep;		/* data entry */
366 	xfs_dir2_data_unused_t	*dup;		/* unused entry */
367 	char			*ptr = NULL;	/* pointer to current data */
368 	struct xfs_da_geometry	*geo = args->geo;
369 	xfs_dablk_t		rablk = 0;	/* current readahead block */
370 	xfs_dir2_off_t		curoff;		/* current overall offset */
371 	int			length;		/* temporary length value */
372 	int			byteoff;	/* offset in current block */
373 	int			lock_mode;
374 	int			error = 0;	/* error return value */
375 
376 	/*
377 	 * If the offset is at or past the largest allowed value,
378 	 * give up right away.
379 	 */
380 	if (ctx->pos >= XFS_DIR2_MAX_DATAPTR)
381 		return 0;
382 
383 	/*
384 	 * Inside the loop we keep the main offset value as a byte offset
385 	 * in the directory file.
386 	 */
387 	curoff = xfs_dir2_dataptr_to_byte(ctx->pos);
388 
389 	/*
390 	 * Loop over directory entries until we reach the end offset.
391 	 * Get more blocks and readahead as necessary.
392 	 */
393 	while (curoff < XFS_DIR2_LEAF_OFFSET) {
394 		uint8_t filetype;
395 
396 		/*
397 		 * If we have no buffer, or we're off the end of the
398 		 * current buffer, need to get another one.
399 		 */
400 		if (!bp || ptr >= (char *)bp->b_addr + geo->blksize) {
401 			if (bp) {
402 				xfs_trans_brelse(args->trans, bp);
403 				bp = NULL;
404 			}
405 
406 			lock_mode = xfs_ilock_data_map_shared(dp);
407 			error = xfs_dir2_leaf_readbuf(args, bufsize, &curoff,
408 					&rablk, &bp);
409 			xfs_iunlock(dp, lock_mode);
410 			if (error || !bp)
411 				break;
412 
413 			hdr = bp->b_addr;
414 			xfs_dir3_data_check(dp, bp);
415 			/*
416 			 * Find our position in the block.
417 			 */
418 			ptr = (char *)dp->d_ops->data_entry_p(hdr);
419 			byteoff = xfs_dir2_byte_to_off(geo, curoff);
420 			/*
421 			 * Skip past the header.
422 			 */
423 			if (byteoff == 0)
424 				curoff += dp->d_ops->data_entry_offset;
425 			/*
426 			 * Skip past entries until we reach our offset.
427 			 */
428 			else {
429 				while ((char *)ptr - (char *)hdr < byteoff) {
430 					dup = (xfs_dir2_data_unused_t *)ptr;
431 
432 					if (be16_to_cpu(dup->freetag)
433 						  == XFS_DIR2_DATA_FREE_TAG) {
434 
435 						length = be16_to_cpu(dup->length);
436 						ptr += length;
437 						continue;
438 					}
439 					dep = (xfs_dir2_data_entry_t *)ptr;
440 					length =
441 					   dp->d_ops->data_entsize(dep->namelen);
442 					ptr += length;
443 				}
444 				/*
445 				 * Now set our real offset.
446 				 */
447 				curoff =
448 					xfs_dir2_db_off_to_byte(geo,
449 					    xfs_dir2_byte_to_db(geo, curoff),
450 					    (char *)ptr - (char *)hdr);
451 				if (ptr >= (char *)hdr + geo->blksize) {
452 					continue;
453 				}
454 			}
455 		}
456 		/*
457 		 * We have a pointer to an entry.
458 		 * Is it a live one?
459 		 */
460 		dup = (xfs_dir2_data_unused_t *)ptr;
461 		/*
462 		 * No, it's unused, skip over it.
463 		 */
464 		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
465 			length = be16_to_cpu(dup->length);
466 			ptr += length;
467 			curoff += length;
468 			continue;
469 		}
470 
471 		dep = (xfs_dir2_data_entry_t *)ptr;
472 		length = dp->d_ops->data_entsize(dep->namelen);
473 		filetype = dp->d_ops->data_get_ftype(dep);
474 
475 		ctx->pos = xfs_dir2_byte_to_dataptr(curoff) & 0x7fffffff;
476 		if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
477 			    be64_to_cpu(dep->inumber),
478 			    xfs_dir3_get_dtype(dp->i_mount, filetype)))
479 			break;
480 
481 		/*
482 		 * Advance to next entry in the block.
483 		 */
484 		ptr += length;
485 		curoff += length;
486 		/* bufsize may have just been a guess; don't go negative */
487 		bufsize = bufsize > length ? bufsize - length : 0;
488 	}
489 
490 	/*
491 	 * All done.  Set output offset value to current offset.
492 	 */
493 	if (curoff > xfs_dir2_dataptr_to_byte(XFS_DIR2_MAX_DATAPTR))
494 		ctx->pos = XFS_DIR2_MAX_DATAPTR & 0x7fffffff;
495 	else
496 		ctx->pos = xfs_dir2_byte_to_dataptr(curoff) & 0x7fffffff;
497 	if (bp)
498 		xfs_trans_brelse(args->trans, bp);
499 	return error;
500 }
501 
502 /*
503  * Read a directory.
504  *
505  * If supplied, the transaction collects locked dir buffers to avoid
506  * nested buffer deadlocks.  This function does not dirty the
507  * transaction.  The caller should ensure that the inode is locked
508  * before calling this function.
509  */
510 int
511 xfs_readdir(
512 	struct xfs_trans	*tp,
513 	struct xfs_inode	*dp,
514 	struct dir_context	*ctx,
515 	size_t			bufsize)
516 {
517 	struct xfs_da_args	args = { NULL };
518 	int			rval;
519 	int			v;
520 
521 	trace_xfs_readdir(dp);
522 
523 	if (XFS_FORCED_SHUTDOWN(dp->i_mount))
524 		return -EIO;
525 
526 	ASSERT(S_ISDIR(VFS_I(dp)->i_mode));
527 	XFS_STATS_INC(dp->i_mount, xs_dir_getdents);
528 
529 	args.dp = dp;
530 	args.geo = dp->i_mount->m_dir_geo;
531 	args.trans = tp;
532 
533 	if (dp->i_d.di_format == XFS_DINODE_FMT_LOCAL)
534 		rval = xfs_dir2_sf_getdents(&args, ctx);
535 	else if ((rval = xfs_dir2_isblock(&args, &v)))
536 		;
537 	else if (v)
538 		rval = xfs_dir2_block_getdents(&args, ctx);
539 	else
540 		rval = xfs_dir2_leaf_getdents(&args, ctx, bufsize);
541 
542 	return rval;
543 }
544