1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* AFS filesystem directory editing
3 *
4 * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #include <linux/kernel.h>
9 #include <linux/fs.h>
10 #include <linux/namei.h>
11 #include <linux/pagemap.h>
12 #include <linux/iversion.h>
13 #include "internal.h"
14 #include "xdr_fs.h"
15
16 /*
17 * Find a number of contiguous clear bits in a directory block bitmask.
18 *
19 * There are 64 slots, which means we can load the entire bitmap into a
20 * variable. The first bit doesn't count as it corresponds to the block header
21 * slot. nr_slots is between 1 and 9.
22 */
afs_find_contig_bits(union afs_xdr_dir_block * block,unsigned int nr_slots)23 static int afs_find_contig_bits(union afs_xdr_dir_block *block, unsigned int nr_slots)
24 {
25 u64 bitmap;
26 u32 mask;
27 int bit, n;
28
29 bitmap = (u64)block->hdr.bitmap[0] << 0 * 8;
30 bitmap |= (u64)block->hdr.bitmap[1] << 1 * 8;
31 bitmap |= (u64)block->hdr.bitmap[2] << 2 * 8;
32 bitmap |= (u64)block->hdr.bitmap[3] << 3 * 8;
33 bitmap |= (u64)block->hdr.bitmap[4] << 4 * 8;
34 bitmap |= (u64)block->hdr.bitmap[5] << 5 * 8;
35 bitmap |= (u64)block->hdr.bitmap[6] << 6 * 8;
36 bitmap |= (u64)block->hdr.bitmap[7] << 7 * 8;
37 bitmap >>= 1; /* The first entry is metadata */
38 bit = 1;
39 mask = (1 << nr_slots) - 1;
40
41 do {
42 if (sizeof(unsigned long) == 8)
43 n = ffz(bitmap);
44 else
45 n = ((u32)bitmap) != 0 ?
46 ffz((u32)bitmap) :
47 ffz((u32)(bitmap >> 32)) + 32;
48 bitmap >>= n;
49 bit += n;
50
51 if ((bitmap & mask) == 0) {
52 if (bit > 64 - nr_slots)
53 return -1;
54 return bit;
55 }
56
57 n = __ffs(bitmap);
58 bitmap >>= n;
59 bit += n;
60 } while (bitmap);
61
62 return -1;
63 }
64
65 /*
66 * Set a number of contiguous bits in the directory block bitmap.
67 */
afs_set_contig_bits(union afs_xdr_dir_block * block,int bit,unsigned int nr_slots)68 static void afs_set_contig_bits(union afs_xdr_dir_block *block,
69 int bit, unsigned int nr_slots)
70 {
71 u64 mask;
72
73 mask = (1 << nr_slots) - 1;
74 mask <<= bit;
75
76 block->hdr.bitmap[0] |= (u8)(mask >> 0 * 8);
77 block->hdr.bitmap[1] |= (u8)(mask >> 1 * 8);
78 block->hdr.bitmap[2] |= (u8)(mask >> 2 * 8);
79 block->hdr.bitmap[3] |= (u8)(mask >> 3 * 8);
80 block->hdr.bitmap[4] |= (u8)(mask >> 4 * 8);
81 block->hdr.bitmap[5] |= (u8)(mask >> 5 * 8);
82 block->hdr.bitmap[6] |= (u8)(mask >> 6 * 8);
83 block->hdr.bitmap[7] |= (u8)(mask >> 7 * 8);
84 }
85
86 /*
87 * Clear a number of contiguous bits in the directory block bitmap.
88 */
afs_clear_contig_bits(union afs_xdr_dir_block * block,int bit,unsigned int nr_slots)89 static void afs_clear_contig_bits(union afs_xdr_dir_block *block,
90 int bit, unsigned int nr_slots)
91 {
92 u64 mask;
93
94 mask = (1 << nr_slots) - 1;
95 mask <<= bit;
96
97 block->hdr.bitmap[0] &= ~(u8)(mask >> 0 * 8);
98 block->hdr.bitmap[1] &= ~(u8)(mask >> 1 * 8);
99 block->hdr.bitmap[2] &= ~(u8)(mask >> 2 * 8);
100 block->hdr.bitmap[3] &= ~(u8)(mask >> 3 * 8);
101 block->hdr.bitmap[4] &= ~(u8)(mask >> 4 * 8);
102 block->hdr.bitmap[5] &= ~(u8)(mask >> 5 * 8);
103 block->hdr.bitmap[6] &= ~(u8)(mask >> 6 * 8);
104 block->hdr.bitmap[7] &= ~(u8)(mask >> 7 * 8);
105 }
106
107 /*
108 * Scan a directory block looking for a dirent of the right name.
109 */
afs_dir_scan_block(union afs_xdr_dir_block * block,struct qstr * name,unsigned int blocknum)110 static int afs_dir_scan_block(union afs_xdr_dir_block *block, struct qstr *name,
111 unsigned int blocknum)
112 {
113 union afs_xdr_dirent *de;
114 u64 bitmap;
115 int d, len, n;
116
117 _enter("");
118
119 bitmap = (u64)block->hdr.bitmap[0] << 0 * 8;
120 bitmap |= (u64)block->hdr.bitmap[1] << 1 * 8;
121 bitmap |= (u64)block->hdr.bitmap[2] << 2 * 8;
122 bitmap |= (u64)block->hdr.bitmap[3] << 3 * 8;
123 bitmap |= (u64)block->hdr.bitmap[4] << 4 * 8;
124 bitmap |= (u64)block->hdr.bitmap[5] << 5 * 8;
125 bitmap |= (u64)block->hdr.bitmap[6] << 6 * 8;
126 bitmap |= (u64)block->hdr.bitmap[7] << 7 * 8;
127
128 for (d = (blocknum == 0 ? AFS_DIR_RESV_BLOCKS0 : AFS_DIR_RESV_BLOCKS);
129 d < AFS_DIR_SLOTS_PER_BLOCK;
130 d++) {
131 if (!((bitmap >> d) & 1))
132 continue;
133 de = &block->dirents[d];
134 if (de->u.valid != 1)
135 continue;
136
137 /* The block was NUL-terminated by afs_dir_check_page(). */
138 len = strlen(de->u.name);
139 if (len == name->len &&
140 memcmp(de->u.name, name->name, name->len) == 0)
141 return d;
142
143 n = round_up(12 + len + 1 + 4, AFS_DIR_DIRENT_SIZE);
144 n /= AFS_DIR_DIRENT_SIZE;
145 d += n - 1;
146 }
147
148 return -1;
149 }
150
151 /*
152 * Initialise a new directory block. Note that block 0 is special and contains
153 * some extra metadata.
154 */
afs_edit_init_block(union afs_xdr_dir_block * meta,union afs_xdr_dir_block * block,int block_num)155 static void afs_edit_init_block(union afs_xdr_dir_block *meta,
156 union afs_xdr_dir_block *block, int block_num)
157 {
158 memset(block, 0, sizeof(*block));
159 block->hdr.npages = htons(1);
160 block->hdr.magic = AFS_DIR_MAGIC;
161 block->hdr.bitmap[0] = 1;
162
163 if (block_num == 0) {
164 block->hdr.bitmap[0] = 0xff;
165 block->hdr.bitmap[1] = 0x1f;
166 memset(block->meta.alloc_ctrs,
167 AFS_DIR_SLOTS_PER_BLOCK,
168 sizeof(block->meta.alloc_ctrs));
169 meta->meta.alloc_ctrs[0] =
170 AFS_DIR_SLOTS_PER_BLOCK - AFS_DIR_RESV_BLOCKS0;
171 }
172
173 if (block_num < AFS_DIR_BLOCKS_WITH_CTR)
174 meta->meta.alloc_ctrs[block_num] =
175 AFS_DIR_SLOTS_PER_BLOCK - AFS_DIR_RESV_BLOCKS;
176 }
177
178 /*
179 * Edit a directory's file data to add a new directory entry. Doing this after
180 * create, mkdir, symlink, link or rename if the data version number is
181 * incremented by exactly one avoids the need to re-download the entire
182 * directory contents.
183 *
184 * The caller must hold the inode locked.
185 */
afs_edit_dir_add(struct afs_vnode * vnode,struct qstr * name,struct afs_fid * new_fid,enum afs_edit_dir_reason why)186 void afs_edit_dir_add(struct afs_vnode *vnode,
187 struct qstr *name, struct afs_fid *new_fid,
188 enum afs_edit_dir_reason why)
189 {
190 union afs_xdr_dir_block *meta, *block;
191 struct afs_xdr_dir_page *meta_page, *dir_page;
192 union afs_xdr_dirent *de;
193 struct page *page0, *page;
194 unsigned int need_slots, nr_blocks, b;
195 pgoff_t index;
196 loff_t i_size;
197 gfp_t gfp;
198 int slot;
199
200 _enter(",,{%d,%s},", name->len, name->name);
201
202 i_size = i_size_read(&vnode->vfs_inode);
203 if (i_size > AFS_DIR_BLOCK_SIZE * AFS_DIR_MAX_BLOCKS ||
204 (i_size & (AFS_DIR_BLOCK_SIZE - 1))) {
205 clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
206 return;
207 }
208
209 gfp = vnode->vfs_inode.i_mapping->gfp_mask;
210 page0 = find_or_create_page(vnode->vfs_inode.i_mapping, 0, gfp);
211 if (!page0) {
212 clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
213 _leave(" [fgp]");
214 return;
215 }
216
217 /* Work out how many slots we're going to need. */
218 need_slots = afs_dir_calc_slots(name->len);
219
220 meta_page = kmap(page0);
221 meta = &meta_page->blocks[0];
222 if (i_size == 0)
223 goto new_directory;
224 nr_blocks = i_size / AFS_DIR_BLOCK_SIZE;
225
226 /* Find a block that has sufficient slots available. Each VM page
227 * contains two or more directory blocks.
228 */
229 for (b = 0; b < nr_blocks + 1; b++) {
230 /* If the directory extended into a new page, then we need to
231 * tack a new page on the end.
232 */
233 index = b / AFS_DIR_BLOCKS_PER_PAGE;
234 if (index == 0) {
235 page = page0;
236 dir_page = meta_page;
237 } else {
238 if (nr_blocks >= AFS_DIR_MAX_BLOCKS)
239 goto error;
240 gfp = vnode->vfs_inode.i_mapping->gfp_mask;
241 page = find_or_create_page(vnode->vfs_inode.i_mapping,
242 index, gfp);
243 if (!page)
244 goto error;
245 if (!PagePrivate(page))
246 attach_page_private(page, (void *)1);
247 dir_page = kmap(page);
248 }
249
250 /* Abandon the edit if we got a callback break. */
251 if (!test_bit(AFS_VNODE_DIR_VALID, &vnode->flags))
252 goto invalidated;
253
254 block = &dir_page->blocks[b % AFS_DIR_BLOCKS_PER_PAGE];
255
256 _debug("block %u: %2u %3u %u",
257 b,
258 (b < AFS_DIR_BLOCKS_WITH_CTR) ? meta->meta.alloc_ctrs[b] : 99,
259 ntohs(block->hdr.npages),
260 ntohs(block->hdr.magic));
261
262 /* Initialise the block if necessary. */
263 if (b == nr_blocks) {
264 _debug("init %u", b);
265 afs_edit_init_block(meta, block, b);
266 i_size_write(&vnode->vfs_inode, (b + 1) * AFS_DIR_BLOCK_SIZE);
267 }
268
269 /* Only lower dir pages have a counter in the header. */
270 if (b >= AFS_DIR_BLOCKS_WITH_CTR ||
271 meta->meta.alloc_ctrs[b] >= need_slots) {
272 /* We need to try and find one or more consecutive
273 * slots to hold the entry.
274 */
275 slot = afs_find_contig_bits(block, need_slots);
276 if (slot >= 0) {
277 _debug("slot %u", slot);
278 goto found_space;
279 }
280 }
281
282 if (page != page0) {
283 unlock_page(page);
284 kunmap(page);
285 put_page(page);
286 }
287 }
288
289 /* There are no spare slots of sufficient size, yet the operation
290 * succeeded. Download the directory again.
291 */
292 trace_afs_edit_dir(vnode, why, afs_edit_dir_create_nospc, 0, 0, 0, 0, name->name);
293 clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
294 goto out_unmap;
295
296 new_directory:
297 afs_edit_init_block(meta, meta, 0);
298 i_size = AFS_DIR_BLOCK_SIZE;
299 i_size_write(&vnode->vfs_inode, i_size);
300 slot = AFS_DIR_RESV_BLOCKS0;
301 page = page0;
302 block = meta;
303 nr_blocks = 1;
304 b = 0;
305
306 found_space:
307 /* Set the dirent slot. */
308 trace_afs_edit_dir(vnode, why, afs_edit_dir_create, b, slot,
309 new_fid->vnode, new_fid->unique, name->name);
310 de = &block->dirents[slot];
311 de->u.valid = 1;
312 de->u.unused[0] = 0;
313 de->u.hash_next = 0; // TODO: Really need to maintain this
314 de->u.vnode = htonl(new_fid->vnode);
315 de->u.unique = htonl(new_fid->unique);
316 memcpy(de->u.name, name->name, name->len + 1);
317 de->u.name[name->len] = 0;
318
319 /* Adjust the bitmap. */
320 afs_set_contig_bits(block, slot, need_slots);
321 if (page != page0) {
322 unlock_page(page);
323 kunmap(page);
324 put_page(page);
325 }
326
327 /* Adjust the allocation counter. */
328 if (b < AFS_DIR_BLOCKS_WITH_CTR)
329 meta->meta.alloc_ctrs[b] -= need_slots;
330
331 inode_inc_iversion_raw(&vnode->vfs_inode);
332 afs_stat_v(vnode, n_dir_cr);
333 _debug("Insert %s in %u[%u]", name->name, b, slot);
334
335 out_unmap:
336 unlock_page(page0);
337 kunmap(page0);
338 put_page(page0);
339 _leave("");
340 return;
341
342 invalidated:
343 trace_afs_edit_dir(vnode, why, afs_edit_dir_create_inval, 0, 0, 0, 0, name->name);
344 clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
345 if (page != page0) {
346 kunmap(page);
347 put_page(page);
348 }
349 goto out_unmap;
350
351 error:
352 trace_afs_edit_dir(vnode, why, afs_edit_dir_create_error, 0, 0, 0, 0, name->name);
353 clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
354 goto out_unmap;
355 }
356
357 /*
358 * Edit a directory's file data to remove a new directory entry. Doing this
359 * after unlink, rmdir or rename if the data version number is incremented by
360 * exactly one avoids the need to re-download the entire directory contents.
361 *
362 * The caller must hold the inode locked.
363 */
afs_edit_dir_remove(struct afs_vnode * vnode,struct qstr * name,enum afs_edit_dir_reason why)364 void afs_edit_dir_remove(struct afs_vnode *vnode,
365 struct qstr *name, enum afs_edit_dir_reason why)
366 {
367 struct afs_xdr_dir_page *meta_page, *dir_page;
368 union afs_xdr_dir_block *meta, *block;
369 union afs_xdr_dirent *de;
370 struct page *page0, *page;
371 unsigned int need_slots, nr_blocks, b;
372 pgoff_t index;
373 loff_t i_size;
374 int slot;
375
376 _enter(",,{%d,%s},", name->len, name->name);
377
378 i_size = i_size_read(&vnode->vfs_inode);
379 if (i_size < AFS_DIR_BLOCK_SIZE ||
380 i_size > AFS_DIR_BLOCK_SIZE * AFS_DIR_MAX_BLOCKS ||
381 (i_size & (AFS_DIR_BLOCK_SIZE - 1))) {
382 clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
383 return;
384 }
385 nr_blocks = i_size / AFS_DIR_BLOCK_SIZE;
386
387 page0 = find_lock_page(vnode->vfs_inode.i_mapping, 0);
388 if (!page0) {
389 clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
390 _leave(" [fgp]");
391 return;
392 }
393
394 /* Work out how many slots we're going to discard. */
395 need_slots = afs_dir_calc_slots(name->len);
396
397 meta_page = kmap(page0);
398 meta = &meta_page->blocks[0];
399
400 /* Find a page that has sufficient slots available. Each VM page
401 * contains two or more directory blocks.
402 */
403 for (b = 0; b < nr_blocks; b++) {
404 index = b / AFS_DIR_BLOCKS_PER_PAGE;
405 if (index != 0) {
406 page = find_lock_page(vnode->vfs_inode.i_mapping, index);
407 if (!page)
408 goto error;
409 dir_page = kmap(page);
410 } else {
411 page = page0;
412 dir_page = meta_page;
413 }
414
415 /* Abandon the edit if we got a callback break. */
416 if (!test_bit(AFS_VNODE_DIR_VALID, &vnode->flags))
417 goto invalidated;
418
419 block = &dir_page->blocks[b % AFS_DIR_BLOCKS_PER_PAGE];
420
421 if (b > AFS_DIR_BLOCKS_WITH_CTR ||
422 meta->meta.alloc_ctrs[b] <= AFS_DIR_SLOTS_PER_BLOCK - 1 - need_slots) {
423 slot = afs_dir_scan_block(block, name, b);
424 if (slot >= 0)
425 goto found_dirent;
426 }
427
428 if (page != page0) {
429 unlock_page(page);
430 kunmap(page);
431 put_page(page);
432 }
433 }
434
435 /* Didn't find the dirent to clobber. Download the directory again. */
436 trace_afs_edit_dir(vnode, why, afs_edit_dir_delete_noent,
437 0, 0, 0, 0, name->name);
438 clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
439 goto out_unmap;
440
441 found_dirent:
442 de = &block->dirents[slot];
443
444 trace_afs_edit_dir(vnode, why, afs_edit_dir_delete, b, slot,
445 ntohl(de->u.vnode), ntohl(de->u.unique),
446 name->name);
447
448 memset(de, 0, sizeof(*de) * need_slots);
449
450 /* Adjust the bitmap. */
451 afs_clear_contig_bits(block, slot, need_slots);
452 if (page != page0) {
453 unlock_page(page);
454 kunmap(page);
455 put_page(page);
456 }
457
458 /* Adjust the allocation counter. */
459 if (b < AFS_DIR_BLOCKS_WITH_CTR)
460 meta->meta.alloc_ctrs[b] += need_slots;
461
462 inode_set_iversion_raw(&vnode->vfs_inode, vnode->status.data_version);
463 afs_stat_v(vnode, n_dir_rm);
464 _debug("Remove %s from %u[%u]", name->name, b, slot);
465
466 out_unmap:
467 unlock_page(page0);
468 kunmap(page0);
469 put_page(page0);
470 _leave("");
471 return;
472
473 invalidated:
474 trace_afs_edit_dir(vnode, why, afs_edit_dir_delete_inval,
475 0, 0, 0, 0, name->name);
476 clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
477 if (page != page0) {
478 unlock_page(page);
479 kunmap(page);
480 put_page(page);
481 }
482 goto out_unmap;
483
484 error:
485 trace_afs_edit_dir(vnode, why, afs_edit_dir_delete_error,
486 0, 0, 0, 0, name->name);
487 clear_bit(AFS_VNODE_DIR_VALID, &vnode->flags);
488 goto out_unmap;
489 }
490