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Linux/fs/affs/file.c

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  1 /*
  2  *  linux/fs/affs/file.c
  3  *
  4  *  (c) 1996  Hans-Joachim Widmaier - Rewritten
  5  *
  6  *  (C) 1993  Ray Burr - Modified for Amiga FFS filesystem.
  7  *
  8  *  (C) 1992  Eric Youngdale Modified for ISO 9660 filesystem.
  9  *
 10  *  (C) 1991  Linus Torvalds - minix filesystem
 11  *
 12  *  affs regular file handling primitives
 13  */
 14 
 15 #include <linux/uio.h>
 16 #include "affs.h"
 17 
 18 static struct buffer_head *affs_get_extblock_slow(struct inode *inode, u32 ext);
 19 
 20 static int
 21 affs_file_open(struct inode *inode, struct file *filp)
 22 {
 23         pr_debug("open(%lu,%d)\n",
 24                  inode->i_ino, atomic_read(&AFFS_I(inode)->i_opencnt));
 25         atomic_inc(&AFFS_I(inode)->i_opencnt);
 26         return 0;
 27 }
 28 
 29 static int
 30 affs_file_release(struct inode *inode, struct file *filp)
 31 {
 32         pr_debug("release(%lu, %d)\n",
 33                  inode->i_ino, atomic_read(&AFFS_I(inode)->i_opencnt));
 34 
 35         if (atomic_dec_and_test(&AFFS_I(inode)->i_opencnt)) {
 36                 inode_lock(inode);
 37                 if (inode->i_size != AFFS_I(inode)->mmu_private)
 38                         affs_truncate(inode);
 39                 affs_free_prealloc(inode);
 40                 inode_unlock(inode);
 41         }
 42 
 43         return 0;
 44 }
 45 
 46 static int
 47 affs_grow_extcache(struct inode *inode, u32 lc_idx)
 48 {
 49         struct super_block      *sb = inode->i_sb;
 50         struct buffer_head      *bh;
 51         u32 lc_max;
 52         int i, j, key;
 53 
 54         if (!AFFS_I(inode)->i_lc) {
 55                 char *ptr = (char *)get_zeroed_page(GFP_NOFS);
 56                 if (!ptr)
 57                         return -ENOMEM;
 58                 AFFS_I(inode)->i_lc = (u32 *)ptr;
 59                 AFFS_I(inode)->i_ac = (struct affs_ext_key *)(ptr + AFFS_CACHE_SIZE / 2);
 60         }
 61 
 62         lc_max = AFFS_LC_SIZE << AFFS_I(inode)->i_lc_shift;
 63 
 64         if (AFFS_I(inode)->i_extcnt > lc_max) {
 65                 u32 lc_shift, lc_mask, tmp, off;
 66 
 67                 /* need to recalculate linear cache, start from old size */
 68                 lc_shift = AFFS_I(inode)->i_lc_shift;
 69                 tmp = (AFFS_I(inode)->i_extcnt / AFFS_LC_SIZE) >> lc_shift;
 70                 for (; tmp; tmp >>= 1)
 71                         lc_shift++;
 72                 lc_mask = (1 << lc_shift) - 1;
 73 
 74                 /* fix idx and old size to new shift */
 75                 lc_idx >>= (lc_shift - AFFS_I(inode)->i_lc_shift);
 76                 AFFS_I(inode)->i_lc_size >>= (lc_shift - AFFS_I(inode)->i_lc_shift);
 77 
 78                 /* first shrink old cache to make more space */
 79                 off = 1 << (lc_shift - AFFS_I(inode)->i_lc_shift);
 80                 for (i = 1, j = off; j < AFFS_LC_SIZE; i++, j += off)
 81                         AFFS_I(inode)->i_ac[i] = AFFS_I(inode)->i_ac[j];
 82 
 83                 AFFS_I(inode)->i_lc_shift = lc_shift;
 84                 AFFS_I(inode)->i_lc_mask = lc_mask;
 85         }
 86 
 87         /* fill cache to the needed index */
 88         i = AFFS_I(inode)->i_lc_size;
 89         AFFS_I(inode)->i_lc_size = lc_idx + 1;
 90         for (; i <= lc_idx; i++) {
 91                 if (!i) {
 92                         AFFS_I(inode)->i_lc[0] = inode->i_ino;
 93                         continue;
 94                 }
 95                 key = AFFS_I(inode)->i_lc[i - 1];
 96                 j = AFFS_I(inode)->i_lc_mask + 1;
 97                 // unlock cache
 98                 for (; j > 0; j--) {
 99                         bh = affs_bread(sb, key);
100                         if (!bh)
101                                 goto err;
102                         key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
103                         affs_brelse(bh);
104                 }
105                 // lock cache
106                 AFFS_I(inode)->i_lc[i] = key;
107         }
108 
109         return 0;
110 
111 err:
112         // lock cache
113         return -EIO;
114 }
115 
116 static struct buffer_head *
117 affs_alloc_extblock(struct inode *inode, struct buffer_head *bh, u32 ext)
118 {
119         struct super_block *sb = inode->i_sb;
120         struct buffer_head *new_bh;
121         u32 blocknr, tmp;
122 
123         blocknr = affs_alloc_block(inode, bh->b_blocknr);
124         if (!blocknr)
125                 return ERR_PTR(-ENOSPC);
126 
127         new_bh = affs_getzeroblk(sb, blocknr);
128         if (!new_bh) {
129                 affs_free_block(sb, blocknr);
130                 return ERR_PTR(-EIO);
131         }
132 
133         AFFS_HEAD(new_bh)->ptype = cpu_to_be32(T_LIST);
134         AFFS_HEAD(new_bh)->key = cpu_to_be32(blocknr);
135         AFFS_TAIL(sb, new_bh)->stype = cpu_to_be32(ST_FILE);
136         AFFS_TAIL(sb, new_bh)->parent = cpu_to_be32(inode->i_ino);
137         affs_fix_checksum(sb, new_bh);
138 
139         mark_buffer_dirty_inode(new_bh, inode);
140 
141         tmp = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
142         if (tmp)
143                 affs_warning(sb, "alloc_ext", "previous extension set (%x)", tmp);
144         AFFS_TAIL(sb, bh)->extension = cpu_to_be32(blocknr);
145         affs_adjust_checksum(bh, blocknr - tmp);
146         mark_buffer_dirty_inode(bh, inode);
147 
148         AFFS_I(inode)->i_extcnt++;
149         mark_inode_dirty(inode);
150 
151         return new_bh;
152 }
153 
154 static inline struct buffer_head *
155 affs_get_extblock(struct inode *inode, u32 ext)
156 {
157         /* inline the simplest case: same extended block as last time */
158         struct buffer_head *bh = AFFS_I(inode)->i_ext_bh;
159         if (ext == AFFS_I(inode)->i_ext_last)
160                 get_bh(bh);
161         else
162                 /* we have to do more (not inlined) */
163                 bh = affs_get_extblock_slow(inode, ext);
164 
165         return bh;
166 }
167 
168 static struct buffer_head *
169 affs_get_extblock_slow(struct inode *inode, u32 ext)
170 {
171         struct super_block *sb = inode->i_sb;
172         struct buffer_head *bh;
173         u32 ext_key;
174         u32 lc_idx, lc_off, ac_idx;
175         u32 tmp, idx;
176 
177         if (ext == AFFS_I(inode)->i_ext_last + 1) {
178                 /* read the next extended block from the current one */
179                 bh = AFFS_I(inode)->i_ext_bh;
180                 ext_key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
181                 if (ext < AFFS_I(inode)->i_extcnt)
182                         goto read_ext;
183                 BUG_ON(ext > AFFS_I(inode)->i_extcnt);
184                 bh = affs_alloc_extblock(inode, bh, ext);
185                 if (IS_ERR(bh))
186                         return bh;
187                 goto store_ext;
188         }
189 
190         if (ext == 0) {
191                 /* we seek back to the file header block */
192                 ext_key = inode->i_ino;
193                 goto read_ext;
194         }
195 
196         if (ext >= AFFS_I(inode)->i_extcnt) {
197                 struct buffer_head *prev_bh;
198 
199                 /* allocate a new extended block */
200                 BUG_ON(ext > AFFS_I(inode)->i_extcnt);
201 
202                 /* get previous extended block */
203                 prev_bh = affs_get_extblock(inode, ext - 1);
204                 if (IS_ERR(prev_bh))
205                         return prev_bh;
206                 bh = affs_alloc_extblock(inode, prev_bh, ext);
207                 affs_brelse(prev_bh);
208                 if (IS_ERR(bh))
209                         return bh;
210                 goto store_ext;
211         }
212 
213 again:
214         /* check if there is an extended cache and whether it's large enough */
215         lc_idx = ext >> AFFS_I(inode)->i_lc_shift;
216         lc_off = ext & AFFS_I(inode)->i_lc_mask;
217 
218         if (lc_idx >= AFFS_I(inode)->i_lc_size) {
219                 int err;
220 
221                 err = affs_grow_extcache(inode, lc_idx);
222                 if (err)
223                         return ERR_PTR(err);
224                 goto again;
225         }
226 
227         /* every n'th key we find in the linear cache */
228         if (!lc_off) {
229                 ext_key = AFFS_I(inode)->i_lc[lc_idx];
230                 goto read_ext;
231         }
232 
233         /* maybe it's still in the associative cache */
234         ac_idx = (ext - lc_idx - 1) & AFFS_AC_MASK;
235         if (AFFS_I(inode)->i_ac[ac_idx].ext == ext) {
236                 ext_key = AFFS_I(inode)->i_ac[ac_idx].key;
237                 goto read_ext;
238         }
239 
240         /* try to find one of the previous extended blocks */
241         tmp = ext;
242         idx = ac_idx;
243         while (--tmp, --lc_off > 0) {
244                 idx = (idx - 1) & AFFS_AC_MASK;
245                 if (AFFS_I(inode)->i_ac[idx].ext == tmp) {
246                         ext_key = AFFS_I(inode)->i_ac[idx].key;
247                         goto find_ext;
248                 }
249         }
250 
251         /* fall back to the linear cache */
252         ext_key = AFFS_I(inode)->i_lc[lc_idx];
253 find_ext:
254         /* read all extended blocks until we find the one we need */
255         //unlock cache
256         do {
257                 bh = affs_bread(sb, ext_key);
258                 if (!bh)
259                         goto err_bread;
260                 ext_key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
261                 affs_brelse(bh);
262                 tmp++;
263         } while (tmp < ext);
264         //lock cache
265 
266         /* store it in the associative cache */
267         // recalculate ac_idx?
268         AFFS_I(inode)->i_ac[ac_idx].ext = ext;
269         AFFS_I(inode)->i_ac[ac_idx].key = ext_key;
270 
271 read_ext:
272         /* finally read the right extended block */
273         //unlock cache
274         bh = affs_bread(sb, ext_key);
275         if (!bh)
276                 goto err_bread;
277         //lock cache
278 
279 store_ext:
280         /* release old cached extended block and store the new one */
281         affs_brelse(AFFS_I(inode)->i_ext_bh);
282         AFFS_I(inode)->i_ext_last = ext;
283         AFFS_I(inode)->i_ext_bh = bh;
284         get_bh(bh);
285 
286         return bh;
287 
288 err_bread:
289         affs_brelse(bh);
290         return ERR_PTR(-EIO);
291 }
292 
293 static int
294 affs_get_block(struct inode *inode, sector_t block, struct buffer_head *bh_result, int create)
295 {
296         struct super_block      *sb = inode->i_sb;
297         struct buffer_head      *ext_bh;
298         u32                      ext;
299 
300         pr_debug("%s(%lu, %llu)\n", __func__, inode->i_ino,
301                  (unsigned long long)block);
302 
303         BUG_ON(block > (sector_t)0x7fffffffUL);
304 
305         if (block >= AFFS_I(inode)->i_blkcnt) {
306                 if (block > AFFS_I(inode)->i_blkcnt || !create)
307                         goto err_big;
308         } else
309                 create = 0;
310 
311         //lock cache
312         affs_lock_ext(inode);
313 
314         ext = (u32)block / AFFS_SB(sb)->s_hashsize;
315         block -= ext * AFFS_SB(sb)->s_hashsize;
316         ext_bh = affs_get_extblock(inode, ext);
317         if (IS_ERR(ext_bh))
318                 goto err_ext;
319         map_bh(bh_result, sb, (sector_t)be32_to_cpu(AFFS_BLOCK(sb, ext_bh, block)));
320 
321         if (create) {
322                 u32 blocknr = affs_alloc_block(inode, ext_bh->b_blocknr);
323                 if (!blocknr)
324                         goto err_alloc;
325                 set_buffer_new(bh_result);
326                 AFFS_I(inode)->mmu_private += AFFS_SB(sb)->s_data_blksize;
327                 AFFS_I(inode)->i_blkcnt++;
328 
329                 /* store new block */
330                 if (bh_result->b_blocknr)
331                         affs_warning(sb, "get_block",
332                                      "block already set (%llx)",
333                                      (unsigned long long)bh_result->b_blocknr);
334                 AFFS_BLOCK(sb, ext_bh, block) = cpu_to_be32(blocknr);
335                 AFFS_HEAD(ext_bh)->block_count = cpu_to_be32(block + 1);
336                 affs_adjust_checksum(ext_bh, blocknr - bh_result->b_blocknr + 1);
337                 bh_result->b_blocknr = blocknr;
338 
339                 if (!block) {
340                         /* insert first block into header block */
341                         u32 tmp = be32_to_cpu(AFFS_HEAD(ext_bh)->first_data);
342                         if (tmp)
343                                 affs_warning(sb, "get_block", "first block already set (%d)", tmp);
344                         AFFS_HEAD(ext_bh)->first_data = cpu_to_be32(blocknr);
345                         affs_adjust_checksum(ext_bh, blocknr - tmp);
346                 }
347         }
348 
349         affs_brelse(ext_bh);
350         //unlock cache
351         affs_unlock_ext(inode);
352         return 0;
353 
354 err_big:
355         affs_error(inode->i_sb, "get_block", "strange block request %llu",
356                    (unsigned long long)block);
357         return -EIO;
358 err_ext:
359         // unlock cache
360         affs_unlock_ext(inode);
361         return PTR_ERR(ext_bh);
362 err_alloc:
363         brelse(ext_bh);
364         clear_buffer_mapped(bh_result);
365         bh_result->b_bdev = NULL;
366         // unlock cache
367         affs_unlock_ext(inode);
368         return -ENOSPC;
369 }
370 
371 static int affs_writepage(struct page *page, struct writeback_control *wbc)
372 {
373         return block_write_full_page(page, affs_get_block, wbc);
374 }
375 
376 static int affs_readpage(struct file *file, struct page *page)
377 {
378         return block_read_full_page(page, affs_get_block);
379 }
380 
381 static void affs_write_failed(struct address_space *mapping, loff_t to)
382 {
383         struct inode *inode = mapping->host;
384 
385         if (to > inode->i_size) {
386                 truncate_pagecache(inode, inode->i_size);
387                 affs_truncate(inode);
388         }
389 }
390 
391 static ssize_t
392 affs_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t offset)
393 {
394         struct file *file = iocb->ki_filp;
395         struct address_space *mapping = file->f_mapping;
396         struct inode *inode = mapping->host;
397         size_t count = iov_iter_count(iter);
398         ssize_t ret;
399 
400         if (iov_iter_rw(iter) == WRITE) {
401                 loff_t size = offset + count;
402 
403                 if (AFFS_I(inode)->mmu_private < size)
404                         return 0;
405         }
406 
407         ret = blockdev_direct_IO(iocb, inode, iter, offset, affs_get_block);
408         if (ret < 0 && iov_iter_rw(iter) == WRITE)
409                 affs_write_failed(mapping, offset + count);
410         return ret;
411 }
412 
413 static int affs_write_begin(struct file *file, struct address_space *mapping,
414                         loff_t pos, unsigned len, unsigned flags,
415                         struct page **pagep, void **fsdata)
416 {
417         int ret;
418 
419         *pagep = NULL;
420         ret = cont_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
421                                 affs_get_block,
422                                 &AFFS_I(mapping->host)->mmu_private);
423         if (unlikely(ret))
424                 affs_write_failed(mapping, pos + len);
425 
426         return ret;
427 }
428 
429 static sector_t _affs_bmap(struct address_space *mapping, sector_t block)
430 {
431         return generic_block_bmap(mapping,block,affs_get_block);
432 }
433 
434 const struct address_space_operations affs_aops = {
435         .readpage = affs_readpage,
436         .writepage = affs_writepage,
437         .write_begin = affs_write_begin,
438         .write_end = generic_write_end,
439         .direct_IO = affs_direct_IO,
440         .bmap = _affs_bmap
441 };
442 
443 static inline struct buffer_head *
444 affs_bread_ino(struct inode *inode, int block, int create)
445 {
446         struct buffer_head *bh, tmp_bh;
447         int err;
448 
449         tmp_bh.b_state = 0;
450         err = affs_get_block(inode, block, &tmp_bh, create);
451         if (!err) {
452                 bh = affs_bread(inode->i_sb, tmp_bh.b_blocknr);
453                 if (bh) {
454                         bh->b_state |= tmp_bh.b_state;
455                         return bh;
456                 }
457                 err = -EIO;
458         }
459         return ERR_PTR(err);
460 }
461 
462 static inline struct buffer_head *
463 affs_getzeroblk_ino(struct inode *inode, int block)
464 {
465         struct buffer_head *bh, tmp_bh;
466         int err;
467 
468         tmp_bh.b_state = 0;
469         err = affs_get_block(inode, block, &tmp_bh, 1);
470         if (!err) {
471                 bh = affs_getzeroblk(inode->i_sb, tmp_bh.b_blocknr);
472                 if (bh) {
473                         bh->b_state |= tmp_bh.b_state;
474                         return bh;
475                 }
476                 err = -EIO;
477         }
478         return ERR_PTR(err);
479 }
480 
481 static inline struct buffer_head *
482 affs_getemptyblk_ino(struct inode *inode, int block)
483 {
484         struct buffer_head *bh, tmp_bh;
485         int err;
486 
487         tmp_bh.b_state = 0;
488         err = affs_get_block(inode, block, &tmp_bh, 1);
489         if (!err) {
490                 bh = affs_getemptyblk(inode->i_sb, tmp_bh.b_blocknr);
491                 if (bh) {
492                         bh->b_state |= tmp_bh.b_state;
493                         return bh;
494                 }
495                 err = -EIO;
496         }
497         return ERR_PTR(err);
498 }
499 
500 static int
501 affs_do_readpage_ofs(struct page *page, unsigned to)
502 {
503         struct inode *inode = page->mapping->host;
504         struct super_block *sb = inode->i_sb;
505         struct buffer_head *bh;
506         char *data;
507         unsigned pos = 0;
508         u32 bidx, boff, bsize;
509         u32 tmp;
510 
511         pr_debug("%s(%lu, %ld, 0, %d)\n", __func__, inode->i_ino,
512                  page->index, to);
513         BUG_ON(to > PAGE_SIZE);
514         bsize = AFFS_SB(sb)->s_data_blksize;
515         tmp = page->index << PAGE_SHIFT;
516         bidx = tmp / bsize;
517         boff = tmp % bsize;
518 
519         while (pos < to) {
520                 bh = affs_bread_ino(inode, bidx, 0);
521                 if (IS_ERR(bh))
522                         return PTR_ERR(bh);
523                 tmp = min(bsize - boff, to - pos);
524                 BUG_ON(pos + tmp > to || tmp > bsize);
525                 data = kmap_atomic(page);
526                 memcpy(data + pos, AFFS_DATA(bh) + boff, tmp);
527                 kunmap_atomic(data);
528                 affs_brelse(bh);
529                 bidx++;
530                 pos += tmp;
531                 boff = 0;
532         }
533         flush_dcache_page(page);
534         return 0;
535 }
536 
537 static int
538 affs_extent_file_ofs(struct inode *inode, u32 newsize)
539 {
540         struct super_block *sb = inode->i_sb;
541         struct buffer_head *bh, *prev_bh;
542         u32 bidx, boff;
543         u32 size, bsize;
544         u32 tmp;
545 
546         pr_debug("%s(%lu, %d)\n", __func__, inode->i_ino, newsize);
547         bsize = AFFS_SB(sb)->s_data_blksize;
548         bh = NULL;
549         size = AFFS_I(inode)->mmu_private;
550         bidx = size / bsize;
551         boff = size % bsize;
552         if (boff) {
553                 bh = affs_bread_ino(inode, bidx, 0);
554                 if (IS_ERR(bh))
555                         return PTR_ERR(bh);
556                 tmp = min(bsize - boff, newsize - size);
557                 BUG_ON(boff + tmp > bsize || tmp > bsize);
558                 memset(AFFS_DATA(bh) + boff, 0, tmp);
559                 be32_add_cpu(&AFFS_DATA_HEAD(bh)->size, tmp);
560                 affs_fix_checksum(sb, bh);
561                 mark_buffer_dirty_inode(bh, inode);
562                 size += tmp;
563                 bidx++;
564         } else if (bidx) {
565                 bh = affs_bread_ino(inode, bidx - 1, 0);
566                 if (IS_ERR(bh))
567                         return PTR_ERR(bh);
568         }
569 
570         while (size < newsize) {
571                 prev_bh = bh;
572                 bh = affs_getzeroblk_ino(inode, bidx);
573                 if (IS_ERR(bh))
574                         goto out;
575                 tmp = min(bsize, newsize - size);
576                 BUG_ON(tmp > bsize);
577                 AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
578                 AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
579                 AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
580                 AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
581                 affs_fix_checksum(sb, bh);
582                 bh->b_state &= ~(1UL << BH_New);
583                 mark_buffer_dirty_inode(bh, inode);
584                 if (prev_bh) {
585                         u32 tmp_next = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
586 
587                         if (tmp_next)
588                                 affs_warning(sb, "extent_file_ofs",
589                                              "next block already set for %d (%d)",
590                                              bidx, tmp_next);
591                         AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
592                         affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp_next);
593                         mark_buffer_dirty_inode(prev_bh, inode);
594                         affs_brelse(prev_bh);
595                 }
596                 size += bsize;
597                 bidx++;
598         }
599         affs_brelse(bh);
600         inode->i_size = AFFS_I(inode)->mmu_private = newsize;
601         return 0;
602 
603 out:
604         inode->i_size = AFFS_I(inode)->mmu_private = newsize;
605         return PTR_ERR(bh);
606 }
607 
608 static int
609 affs_readpage_ofs(struct file *file, struct page *page)
610 {
611         struct inode *inode = page->mapping->host;
612         u32 to;
613         int err;
614 
615         pr_debug("%s(%lu, %ld)\n", __func__, inode->i_ino, page->index);
616         to = PAGE_SIZE;
617         if (((page->index + 1) << PAGE_SHIFT) > inode->i_size) {
618                 to = inode->i_size & ~PAGE_MASK;
619                 memset(page_address(page) + to, 0, PAGE_SIZE - to);
620         }
621 
622         err = affs_do_readpage_ofs(page, to);
623         if (!err)
624                 SetPageUptodate(page);
625         unlock_page(page);
626         return err;
627 }
628 
629 static int affs_write_begin_ofs(struct file *file, struct address_space *mapping,
630                                 loff_t pos, unsigned len, unsigned flags,
631                                 struct page **pagep, void **fsdata)
632 {
633         struct inode *inode = mapping->host;
634         struct page *page;
635         pgoff_t index;
636         int err = 0;
637 
638         pr_debug("%s(%lu, %llu, %llu)\n", __func__, inode->i_ino, pos,
639                  pos + len);
640         if (pos > AFFS_I(inode)->mmu_private) {
641                 /* XXX: this probably leaves a too-big i_size in case of
642                  * failure. Should really be updating i_size at write_end time
643                  */
644                 err = affs_extent_file_ofs(inode, pos);
645                 if (err)
646                         return err;
647         }
648 
649         index = pos >> PAGE_SHIFT;
650         page = grab_cache_page_write_begin(mapping, index, flags);
651         if (!page)
652                 return -ENOMEM;
653         *pagep = page;
654 
655         if (PageUptodate(page))
656                 return 0;
657 
658         /* XXX: inefficient but safe in the face of short writes */
659         err = affs_do_readpage_ofs(page, PAGE_SIZE);
660         if (err) {
661                 unlock_page(page);
662                 put_page(page);
663         }
664         return err;
665 }
666 
667 static int affs_write_end_ofs(struct file *file, struct address_space *mapping,
668                                 loff_t pos, unsigned len, unsigned copied,
669                                 struct page *page, void *fsdata)
670 {
671         struct inode *inode = mapping->host;
672         struct super_block *sb = inode->i_sb;
673         struct buffer_head *bh, *prev_bh;
674         char *data;
675         u32 bidx, boff, bsize;
676         unsigned from, to;
677         u32 tmp;
678         int written;
679 
680         from = pos & (PAGE_SIZE - 1);
681         to = pos + len;
682         /*
683          * XXX: not sure if this can handle short copies (len < copied), but
684          * we don't have to, because the page should always be uptodate here,
685          * due to write_begin.
686          */
687 
688         pr_debug("%s(%lu, %llu, %llu)\n", __func__, inode->i_ino, pos,
689                  pos + len);
690         bsize = AFFS_SB(sb)->s_data_blksize;
691         data = page_address(page);
692 
693         bh = NULL;
694         written = 0;
695         tmp = (page->index << PAGE_SHIFT) + from;
696         bidx = tmp / bsize;
697         boff = tmp % bsize;
698         if (boff) {
699                 bh = affs_bread_ino(inode, bidx, 0);
700                 if (IS_ERR(bh)) {
701                         written = PTR_ERR(bh);
702                         goto err_first_bh;
703                 }
704                 tmp = min(bsize - boff, to - from);
705                 BUG_ON(boff + tmp > bsize || tmp > bsize);
706                 memcpy(AFFS_DATA(bh) + boff, data + from, tmp);
707                 be32_add_cpu(&AFFS_DATA_HEAD(bh)->size, tmp);
708                 affs_fix_checksum(sb, bh);
709                 mark_buffer_dirty_inode(bh, inode);
710                 written += tmp;
711                 from += tmp;
712                 bidx++;
713         } else if (bidx) {
714                 bh = affs_bread_ino(inode, bidx - 1, 0);
715                 if (IS_ERR(bh)) {
716                         written = PTR_ERR(bh);
717                         goto err_first_bh;
718                 }
719         }
720         while (from + bsize <= to) {
721                 prev_bh = bh;
722                 bh = affs_getemptyblk_ino(inode, bidx);
723                 if (IS_ERR(bh))
724                         goto err_bh;
725                 memcpy(AFFS_DATA(bh), data + from, bsize);
726                 if (buffer_new(bh)) {
727                         AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
728                         AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
729                         AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
730                         AFFS_DATA_HEAD(bh)->size = cpu_to_be32(bsize);
731                         AFFS_DATA_HEAD(bh)->next = 0;
732                         bh->b_state &= ~(1UL << BH_New);
733                         if (prev_bh) {
734                                 u32 tmp_next = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
735 
736                                 if (tmp_next)
737                                         affs_warning(sb, "commit_write_ofs",
738                                                      "next block already set for %d (%d)",
739                                                      bidx, tmp_next);
740                                 AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
741                                 affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp_next);
742                                 mark_buffer_dirty_inode(prev_bh, inode);
743                         }
744                 }
745                 affs_brelse(prev_bh);
746                 affs_fix_checksum(sb, bh);
747                 mark_buffer_dirty_inode(bh, inode);
748                 written += bsize;
749                 from += bsize;
750                 bidx++;
751         }
752         if (from < to) {
753                 prev_bh = bh;
754                 bh = affs_bread_ino(inode, bidx, 1);
755                 if (IS_ERR(bh))
756                         goto err_bh;
757                 tmp = min(bsize, to - from);
758                 BUG_ON(tmp > bsize);
759                 memcpy(AFFS_DATA(bh), data + from, tmp);
760                 if (buffer_new(bh)) {
761                         AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
762                         AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
763                         AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
764                         AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
765                         AFFS_DATA_HEAD(bh)->next = 0;
766                         bh->b_state &= ~(1UL << BH_New);
767                         if (prev_bh) {
768                                 u32 tmp_next = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
769 
770                                 if (tmp_next)
771                                         affs_warning(sb, "commit_write_ofs",
772                                                      "next block already set for %d (%d)",
773                                                      bidx, tmp_next);
774                                 AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
775                                 affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp_next);
776                                 mark_buffer_dirty_inode(prev_bh, inode);
777                         }
778                 } else if (be32_to_cpu(AFFS_DATA_HEAD(bh)->size) < tmp)
779                         AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
780                 affs_brelse(prev_bh);
781                 affs_fix_checksum(sb, bh);
782                 mark_buffer_dirty_inode(bh, inode);
783                 written += tmp;
784                 from += tmp;
785                 bidx++;
786         }
787         SetPageUptodate(page);
788 
789 done:
790         affs_brelse(bh);
791         tmp = (page->index << PAGE_SHIFT) + from;
792         if (tmp > inode->i_size)
793                 inode->i_size = AFFS_I(inode)->mmu_private = tmp;
794 
795 err_first_bh:
796         unlock_page(page);
797         put_page(page);
798 
799         return written;
800 
801 err_bh:
802         bh = prev_bh;
803         if (!written)
804                 written = PTR_ERR(bh);
805         goto done;
806 }
807 
808 const struct address_space_operations affs_aops_ofs = {
809         .readpage = affs_readpage_ofs,
810         //.writepage = affs_writepage_ofs,
811         .write_begin = affs_write_begin_ofs,
812         .write_end = affs_write_end_ofs
813 };
814 
815 /* Free any preallocated blocks. */
816 
817 void
818 affs_free_prealloc(struct inode *inode)
819 {
820         struct super_block *sb = inode->i_sb;
821 
822         pr_debug("free_prealloc(ino=%lu)\n", inode->i_ino);
823 
824         while (AFFS_I(inode)->i_pa_cnt) {
825                 AFFS_I(inode)->i_pa_cnt--;
826                 affs_free_block(sb, ++AFFS_I(inode)->i_lastalloc);
827         }
828 }
829 
830 /* Truncate (or enlarge) a file to the requested size. */
831 
832 void
833 affs_truncate(struct inode *inode)
834 {
835         struct super_block *sb = inode->i_sb;
836         u32 ext, ext_key;
837         u32 last_blk, blkcnt, blk;
838         u32 size;
839         struct buffer_head *ext_bh;
840         int i;
841 
842         pr_debug("truncate(inode=%lu, oldsize=%llu, newsize=%llu)\n",
843                  inode->i_ino, AFFS_I(inode)->mmu_private, inode->i_size);
844 
845         last_blk = 0;
846         ext = 0;
847         if (inode->i_size) {
848                 last_blk = ((u32)inode->i_size - 1) / AFFS_SB(sb)->s_data_blksize;
849                 ext = last_blk / AFFS_SB(sb)->s_hashsize;
850         }
851 
852         if (inode->i_size > AFFS_I(inode)->mmu_private) {
853                 struct address_space *mapping = inode->i_mapping;
854                 struct page *page;
855                 void *fsdata;
856                 loff_t isize = inode->i_size;
857                 int res;
858 
859                 res = mapping->a_ops->write_begin(NULL, mapping, isize, 0, 0, &page, &fsdata);
860                 if (!res)
861                         res = mapping->a_ops->write_end(NULL, mapping, isize, 0, 0, page, fsdata);
862                 else
863                         inode->i_size = AFFS_I(inode)->mmu_private;
864                 mark_inode_dirty(inode);
865                 return;
866         } else if (inode->i_size == AFFS_I(inode)->mmu_private)
867                 return;
868 
869         // lock cache
870         ext_bh = affs_get_extblock(inode, ext);
871         if (IS_ERR(ext_bh)) {
872                 affs_warning(sb, "truncate",
873                              "unexpected read error for ext block %u (%ld)",
874                              ext, PTR_ERR(ext_bh));
875                 return;
876         }
877         if (AFFS_I(inode)->i_lc) {
878                 /* clear linear cache */
879                 i = (ext + 1) >> AFFS_I(inode)->i_lc_shift;
880                 if (AFFS_I(inode)->i_lc_size > i) {
881                         AFFS_I(inode)->i_lc_size = i;
882                         for (; i < AFFS_LC_SIZE; i++)
883                                 AFFS_I(inode)->i_lc[i] = 0;
884                 }
885                 /* clear associative cache */
886                 for (i = 0; i < AFFS_AC_SIZE; i++)
887                         if (AFFS_I(inode)->i_ac[i].ext >= ext)
888                                 AFFS_I(inode)->i_ac[i].ext = 0;
889         }
890         ext_key = be32_to_cpu(AFFS_TAIL(sb, ext_bh)->extension);
891 
892         blkcnt = AFFS_I(inode)->i_blkcnt;
893         i = 0;
894         blk = last_blk;
895         if (inode->i_size) {
896                 i = last_blk % AFFS_SB(sb)->s_hashsize + 1;
897                 blk++;
898         } else
899                 AFFS_HEAD(ext_bh)->first_data = 0;
900         AFFS_HEAD(ext_bh)->block_count = cpu_to_be32(i);
901         size = AFFS_SB(sb)->s_hashsize;
902         if (size > blkcnt - blk + i)
903                 size = blkcnt - blk + i;
904         for (; i < size; i++, blk++) {
905                 affs_free_block(sb, be32_to_cpu(AFFS_BLOCK(sb, ext_bh, i)));
906                 AFFS_BLOCK(sb, ext_bh, i) = 0;
907         }
908         AFFS_TAIL(sb, ext_bh)->extension = 0;
909         affs_fix_checksum(sb, ext_bh);
910         mark_buffer_dirty_inode(ext_bh, inode);
911         affs_brelse(ext_bh);
912 
913         if (inode->i_size) {
914                 AFFS_I(inode)->i_blkcnt = last_blk + 1;
915                 AFFS_I(inode)->i_extcnt = ext + 1;
916                 if (affs_test_opt(AFFS_SB(sb)->s_flags, SF_OFS)) {
917                         struct buffer_head *bh = affs_bread_ino(inode, last_blk, 0);
918                         u32 tmp;
919                         if (IS_ERR(bh)) {
920                                 affs_warning(sb, "truncate",
921                                              "unexpected read error for last block %u (%ld)",
922                                              ext, PTR_ERR(bh));
923                                 return;
924                         }
925                         tmp = be32_to_cpu(AFFS_DATA_HEAD(bh)->next);
926                         AFFS_DATA_HEAD(bh)->next = 0;
927                         affs_adjust_checksum(bh, -tmp);
928                         affs_brelse(bh);
929                 }
930         } else {
931                 AFFS_I(inode)->i_blkcnt = 0;
932                 AFFS_I(inode)->i_extcnt = 1;
933         }
934         AFFS_I(inode)->mmu_private = inode->i_size;
935         // unlock cache
936 
937         while (ext_key) {
938                 ext_bh = affs_bread(sb, ext_key);
939                 size = AFFS_SB(sb)->s_hashsize;
940                 if (size > blkcnt - blk)
941                         size = blkcnt - blk;
942                 for (i = 0; i < size; i++, blk++)
943                         affs_free_block(sb, be32_to_cpu(AFFS_BLOCK(sb, ext_bh, i)));
944                 affs_free_block(sb, ext_key);
945                 ext_key = be32_to_cpu(AFFS_TAIL(sb, ext_bh)->extension);
946                 affs_brelse(ext_bh);
947         }
948         affs_free_prealloc(inode);
949 }
950 
951 int affs_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
952 {
953         struct inode *inode = filp->f_mapping->host;
954         int ret, err;
955 
956         err = filemap_write_and_wait_range(inode->i_mapping, start, end);
957         if (err)
958                 return err;
959 
960         inode_lock(inode);
961         ret = write_inode_now(inode, 0);
962         err = sync_blockdev(inode->i_sb->s_bdev);
963         if (!ret)
964                 ret = err;
965         inode_unlock(inode);
966         return ret;
967 }
968 const struct file_operations affs_file_operations = {
969         .llseek         = generic_file_llseek,
970         .read_iter      = generic_file_read_iter,
971         .write_iter     = generic_file_write_iter,
972         .mmap           = generic_file_mmap,
973         .open           = affs_file_open,
974         .release        = affs_file_release,
975         .fsync          = affs_file_fsync,
976         .splice_read    = generic_file_splice_read,
977 };
978 
979 const struct inode_operations affs_file_inode_operations = {
980         .setattr        = affs_notify_change,
981 };
982 

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