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Linux/fs/ext2/inode.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  *  linux/fs/ext2/inode.c
  4  *
  5  * Copyright (C) 1992, 1993, 1994, 1995
  6  * Remy Card (card@masi.ibp.fr)
  7  * Laboratoire MASI - Institut Blaise Pascal
  8  * Universite Pierre et Marie Curie (Paris VI)
  9  *
 10  *  from
 11  *
 12  *  linux/fs/minix/inode.c
 13  *
 14  *  Copyright (C) 1991, 1992  Linus Torvalds
 15  *
 16  *  Goal-directed block allocation by Stephen Tweedie
 17  *      (sct@dcs.ed.ac.uk), 1993, 1998
 18  *  Big-endian to little-endian byte-swapping/bitmaps by
 19  *        David S. Miller (davem@caip.rutgers.edu), 1995
 20  *  64-bit file support on 64-bit platforms by Jakub Jelinek
 21  *      (jj@sunsite.ms.mff.cuni.cz)
 22  *
 23  *  Assorted race fixes, rewrite of ext2_get_block() by Al Viro, 2000
 24  */
 25 
 26 #include <linux/time.h>
 27 #include <linux/highuid.h>
 28 #include <linux/pagemap.h>
 29 #include <linux/dax.h>
 30 #include <linux/blkdev.h>
 31 #include <linux/quotaops.h>
 32 #include <linux/writeback.h>
 33 #include <linux/buffer_head.h>
 34 #include <linux/mpage.h>
 35 #include <linux/fiemap.h>
 36 #include <linux/iomap.h>
 37 #include <linux/namei.h>
 38 #include <linux/uio.h>
 39 #include <linux/fiemap.h>
 40 #include "ext2.h"
 41 #include "acl.h"
 42 #include "xattr.h"
 43 
 44 static int __ext2_write_inode(struct inode *inode, int do_sync);
 45 
 46 /*
 47  * Test whether an inode is a fast symlink.
 48  */
 49 static inline int ext2_inode_is_fast_symlink(struct inode *inode)
 50 {
 51         int ea_blocks = EXT2_I(inode)->i_file_acl ?
 52                 (inode->i_sb->s_blocksize >> 9) : 0;
 53 
 54         return (S_ISLNK(inode->i_mode) &&
 55                 inode->i_blocks - ea_blocks == 0);
 56 }
 57 
 58 static void ext2_truncate_blocks(struct inode *inode, loff_t offset);
 59 
 60 static void ext2_write_failed(struct address_space *mapping, loff_t to)
 61 {
 62         struct inode *inode = mapping->host;
 63 
 64         if (to > inode->i_size) {
 65                 truncate_pagecache(inode, inode->i_size);
 66                 ext2_truncate_blocks(inode, inode->i_size);
 67         }
 68 }
 69 
 70 /*
 71  * Called at the last iput() if i_nlink is zero.
 72  */
 73 void ext2_evict_inode(struct inode * inode)
 74 {
 75         struct ext2_block_alloc_info *rsv;
 76         int want_delete = 0;
 77 
 78         if (!inode->i_nlink && !is_bad_inode(inode)) {
 79                 want_delete = 1;
 80                 dquot_initialize(inode);
 81         } else {
 82                 dquot_drop(inode);
 83         }
 84 
 85         truncate_inode_pages_final(&inode->i_data);
 86 
 87         if (want_delete) {
 88                 sb_start_intwrite(inode->i_sb);
 89                 /* set dtime */
 90                 EXT2_I(inode)->i_dtime  = ktime_get_real_seconds();
 91                 mark_inode_dirty(inode);
 92                 __ext2_write_inode(inode, inode_needs_sync(inode));
 93                 /* truncate to 0 */
 94                 inode->i_size = 0;
 95                 if (inode->i_blocks)
 96                         ext2_truncate_blocks(inode, 0);
 97                 ext2_xattr_delete_inode(inode);
 98         }
 99 
100         invalidate_inode_buffers(inode);
101         clear_inode(inode);
102 
103         ext2_discard_reservation(inode);
104         rsv = EXT2_I(inode)->i_block_alloc_info;
105         EXT2_I(inode)->i_block_alloc_info = NULL;
106         if (unlikely(rsv))
107                 kfree(rsv);
108 
109         if (want_delete) {
110                 ext2_free_inode(inode);
111                 sb_end_intwrite(inode->i_sb);
112         }
113 }
114 
115 typedef struct {
116         __le32  *p;
117         __le32  key;
118         struct buffer_head *bh;
119 } Indirect;
120 
121 static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
122 {
123         p->key = *(p->p = v);
124         p->bh = bh;
125 }
126 
127 static inline int verify_chain(Indirect *from, Indirect *to)
128 {
129         while (from <= to && from->key == *from->p)
130                 from++;
131         return (from > to);
132 }
133 
134 /**
135  *      ext2_block_to_path - parse the block number into array of offsets
136  *      @inode: inode in question (we are only interested in its superblock)
137  *      @i_block: block number to be parsed
138  *      @offsets: array to store the offsets in
139  *      @boundary: set this non-zero if the referred-to block is likely to be
140  *             followed (on disk) by an indirect block.
141  *      To store the locations of file's data ext2 uses a data structure common
142  *      for UNIX filesystems - tree of pointers anchored in the inode, with
143  *      data blocks at leaves and indirect blocks in intermediate nodes.
144  *      This function translates the block number into path in that tree -
145  *      return value is the path length and @offsets[n] is the offset of
146  *      pointer to (n+1)th node in the nth one. If @block is out of range
147  *      (negative or too large) warning is printed and zero returned.
148  *
149  *      Note: function doesn't find node addresses, so no IO is needed. All
150  *      we need to know is the capacity of indirect blocks (taken from the
151  *      inode->i_sb).
152  */
153 
154 /*
155  * Portability note: the last comparison (check that we fit into triple
156  * indirect block) is spelled differently, because otherwise on an
157  * architecture with 32-bit longs and 8Kb pages we might get into trouble
158  * if our filesystem had 8Kb blocks. We might use long long, but that would
159  * kill us on x86. Oh, well, at least the sign propagation does not matter -
160  * i_block would have to be negative in the very beginning, so we would not
161  * get there at all.
162  */
163 
164 static int ext2_block_to_path(struct inode *inode,
165                         long i_block, int offsets[4], int *boundary)
166 {
167         int ptrs = EXT2_ADDR_PER_BLOCK(inode->i_sb);
168         int ptrs_bits = EXT2_ADDR_PER_BLOCK_BITS(inode->i_sb);
169         const long direct_blocks = EXT2_NDIR_BLOCKS,
170                 indirect_blocks = ptrs,
171                 double_blocks = (1 << (ptrs_bits * 2));
172         int n = 0;
173         int final = 0;
174 
175         if (i_block < 0) {
176                 ext2_msg(inode->i_sb, KERN_WARNING,
177                         "warning: %s: block < 0", __func__);
178         } else if (i_block < direct_blocks) {
179                 offsets[n++] = i_block;
180                 final = direct_blocks;
181         } else if ( (i_block -= direct_blocks) < indirect_blocks) {
182                 offsets[n++] = EXT2_IND_BLOCK;
183                 offsets[n++] = i_block;
184                 final = ptrs;
185         } else if ((i_block -= indirect_blocks) < double_blocks) {
186                 offsets[n++] = EXT2_DIND_BLOCK;
187                 offsets[n++] = i_block >> ptrs_bits;
188                 offsets[n++] = i_block & (ptrs - 1);
189                 final = ptrs;
190         } else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
191                 offsets[n++] = EXT2_TIND_BLOCK;
192                 offsets[n++] = i_block >> (ptrs_bits * 2);
193                 offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
194                 offsets[n++] = i_block & (ptrs - 1);
195                 final = ptrs;
196         } else {
197                 ext2_msg(inode->i_sb, KERN_WARNING,
198                         "warning: %s: block is too big", __func__);
199         }
200         if (boundary)
201                 *boundary = final - 1 - (i_block & (ptrs - 1));
202 
203         return n;
204 }
205 
206 /**
207  *      ext2_get_branch - read the chain of indirect blocks leading to data
208  *      @inode: inode in question
209  *      @depth: depth of the chain (1 - direct pointer, etc.)
210  *      @offsets: offsets of pointers in inode/indirect blocks
211  *      @chain: place to store the result
212  *      @err: here we store the error value
213  *
214  *      Function fills the array of triples <key, p, bh> and returns %NULL
215  *      if everything went OK or the pointer to the last filled triple
216  *      (incomplete one) otherwise. Upon the return chain[i].key contains
217  *      the number of (i+1)-th block in the chain (as it is stored in memory,
218  *      i.e. little-endian 32-bit), chain[i].p contains the address of that
219  *      number (it points into struct inode for i==0 and into the bh->b_data
220  *      for i>0) and chain[i].bh points to the buffer_head of i-th indirect
221  *      block for i>0 and NULL for i==0. In other words, it holds the block
222  *      numbers of the chain, addresses they were taken from (and where we can
223  *      verify that chain did not change) and buffer_heads hosting these
224  *      numbers.
225  *
226  *      Function stops when it stumbles upon zero pointer (absent block)
227  *              (pointer to last triple returned, *@err == 0)
228  *      or when it gets an IO error reading an indirect block
229  *              (ditto, *@err == -EIO)
230  *      or when it notices that chain had been changed while it was reading
231  *              (ditto, *@err == -EAGAIN)
232  *      or when it reads all @depth-1 indirect blocks successfully and finds
233  *      the whole chain, all way to the data (returns %NULL, *err == 0).
234  */
235 static Indirect *ext2_get_branch(struct inode *inode,
236                                  int depth,
237                                  int *offsets,
238                                  Indirect chain[4],
239                                  int *err)
240 {
241         struct super_block *sb = inode->i_sb;
242         Indirect *p = chain;
243         struct buffer_head *bh;
244 
245         *err = 0;
246         /* i_data is not going away, no lock needed */
247         add_chain (chain, NULL, EXT2_I(inode)->i_data + *offsets);
248         if (!p->key)
249                 goto no_block;
250         while (--depth) {
251                 bh = sb_bread(sb, le32_to_cpu(p->key));
252                 if (!bh)
253                         goto failure;
254                 read_lock(&EXT2_I(inode)->i_meta_lock);
255                 if (!verify_chain(chain, p))
256                         goto changed;
257                 add_chain(++p, bh, (__le32*)bh->b_data + *++offsets);
258                 read_unlock(&EXT2_I(inode)->i_meta_lock);
259                 if (!p->key)
260                         goto no_block;
261         }
262         return NULL;
263 
264 changed:
265         read_unlock(&EXT2_I(inode)->i_meta_lock);
266         brelse(bh);
267         *err = -EAGAIN;
268         goto no_block;
269 failure:
270         *err = -EIO;
271 no_block:
272         return p;
273 }
274 
275 /**
276  *      ext2_find_near - find a place for allocation with sufficient locality
277  *      @inode: owner
278  *      @ind: descriptor of indirect block.
279  *
280  *      This function returns the preferred place for block allocation.
281  *      It is used when heuristic for sequential allocation fails.
282  *      Rules are:
283  *        + if there is a block to the left of our position - allocate near it.
284  *        + if pointer will live in indirect block - allocate near that block.
285  *        + if pointer will live in inode - allocate in the same cylinder group.
286  *
287  * In the latter case we colour the starting block by the callers PID to
288  * prevent it from clashing with concurrent allocations for a different inode
289  * in the same block group.   The PID is used here so that functionally related
290  * files will be close-by on-disk.
291  *
292  *      Caller must make sure that @ind is valid and will stay that way.
293  */
294 
295 static ext2_fsblk_t ext2_find_near(struct inode *inode, Indirect *ind)
296 {
297         struct ext2_inode_info *ei = EXT2_I(inode);
298         __le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
299         __le32 *p;
300         ext2_fsblk_t bg_start;
301         ext2_fsblk_t colour;
302 
303         /* Try to find previous block */
304         for (p = ind->p - 1; p >= start; p--)
305                 if (*p)
306                         return le32_to_cpu(*p);
307 
308         /* No such thing, so let's try location of indirect block */
309         if (ind->bh)
310                 return ind->bh->b_blocknr;
311 
312         /*
313          * It is going to be referred from inode itself? OK, just put it into
314          * the same cylinder group then.
315          */
316         bg_start = ext2_group_first_block_no(inode->i_sb, ei->i_block_group);
317         colour = (current->pid % 16) *
318                         (EXT2_BLOCKS_PER_GROUP(inode->i_sb) / 16);
319         return bg_start + colour;
320 }
321 
322 /**
323  *      ext2_find_goal - find a preferred place for allocation.
324  *      @inode: owner
325  *      @block:  block we want
326  *      @partial: pointer to the last triple within a chain
327  *
328  *      Returns preferred place for a block (the goal).
329  */
330 
331 static inline ext2_fsblk_t ext2_find_goal(struct inode *inode, long block,
332                                           Indirect *partial)
333 {
334         struct ext2_block_alloc_info *block_i;
335 
336         block_i = EXT2_I(inode)->i_block_alloc_info;
337 
338         /*
339          * try the heuristic for sequential allocation,
340          * failing that at least try to get decent locality.
341          */
342         if (block_i && (block == block_i->last_alloc_logical_block + 1)
343                 && (block_i->last_alloc_physical_block != 0)) {
344                 return block_i->last_alloc_physical_block + 1;
345         }
346 
347         return ext2_find_near(inode, partial);
348 }
349 
350 /**
351  *      ext2_blks_to_allocate: Look up the block map and count the number
352  *      of direct blocks need to be allocated for the given branch.
353  *
354  *      @branch: chain of indirect blocks
355  *      @k: number of blocks need for indirect blocks
356  *      @blks: number of data blocks to be mapped.
357  *      @blocks_to_boundary:  the offset in the indirect block
358  *
359  *      return the number of direct blocks to allocate.
360  */
361 static int
362 ext2_blks_to_allocate(Indirect * branch, int k, unsigned long blks,
363                 int blocks_to_boundary)
364 {
365         unsigned long count = 0;
366 
367         /*
368          * Simple case, [t,d]Indirect block(s) has not allocated yet
369          * then it's clear blocks on that path have not allocated
370          */
371         if (k > 0) {
372                 /* right now don't hanel cross boundary allocation */
373                 if (blks < blocks_to_boundary + 1)
374                         count += blks;
375                 else
376                         count += blocks_to_boundary + 1;
377                 return count;
378         }
379 
380         count++;
381         while (count < blks && count <= blocks_to_boundary
382                 && le32_to_cpu(*(branch[0].p + count)) == 0) {
383                 count++;
384         }
385         return count;
386 }
387 
388 /**
389  *      ext2_alloc_blocks: multiple allocate blocks needed for a branch
390  *      @indirect_blks: the number of blocks need to allocate for indirect
391  *                      blocks
392  *      @blks: the number of blocks need to allocate for direct blocks
393  *      @new_blocks: on return it will store the new block numbers for
394  *      the indirect blocks(if needed) and the first direct block,
395  */
396 static int ext2_alloc_blocks(struct inode *inode,
397                         ext2_fsblk_t goal, int indirect_blks, int blks,
398                         ext2_fsblk_t new_blocks[4], int *err)
399 {
400         int target, i;
401         unsigned long count = 0;
402         int index = 0;
403         ext2_fsblk_t current_block = 0;
404         int ret = 0;
405 
406         /*
407          * Here we try to allocate the requested multiple blocks at once,
408          * on a best-effort basis.
409          * To build a branch, we should allocate blocks for
410          * the indirect blocks(if not allocated yet), and at least
411          * the first direct block of this branch.  That's the
412          * minimum number of blocks need to allocate(required)
413          */
414         target = blks + indirect_blks;
415 
416         while (1) {
417                 count = target;
418                 /* allocating blocks for indirect blocks and direct blocks */
419                 current_block = ext2_new_blocks(inode,goal,&count,err);
420                 if (*err)
421                         goto failed_out;
422 
423                 target -= count;
424                 /* allocate blocks for indirect blocks */
425                 while (index < indirect_blks && count) {
426                         new_blocks[index++] = current_block++;
427                         count--;
428                 }
429 
430                 if (count > 0)
431                         break;
432         }
433 
434         /* save the new block number for the first direct block */
435         new_blocks[index] = current_block;
436 
437         /* total number of blocks allocated for direct blocks */
438         ret = count;
439         *err = 0;
440         return ret;
441 failed_out:
442         for (i = 0; i <index; i++)
443                 ext2_free_blocks(inode, new_blocks[i], 1);
444         if (index)
445                 mark_inode_dirty(inode);
446         return ret;
447 }
448 
449 /**
450  *      ext2_alloc_branch - allocate and set up a chain of blocks.
451  *      @inode: owner
452  *      @indirect_blks: depth of the chain (number of blocks to allocate)
453  *      @blks: number of allocated direct blocks
454  *      @goal: preferred place for allocation
455  *      @offsets: offsets (in the blocks) to store the pointers to next.
456  *      @branch: place to store the chain in.
457  *
458  *      This function allocates @num blocks, zeroes out all but the last one,
459  *      links them into chain and (if we are synchronous) writes them to disk.
460  *      In other words, it prepares a branch that can be spliced onto the
461  *      inode. It stores the information about that chain in the branch[], in
462  *      the same format as ext2_get_branch() would do. We are calling it after
463  *      we had read the existing part of chain and partial points to the last
464  *      triple of that (one with zero ->key). Upon the exit we have the same
465  *      picture as after the successful ext2_get_block(), except that in one
466  *      place chain is disconnected - *branch->p is still zero (we did not
467  *      set the last link), but branch->key contains the number that should
468  *      be placed into *branch->p to fill that gap.
469  *
470  *      If allocation fails we free all blocks we've allocated (and forget
471  *      their buffer_heads) and return the error value the from failed
472  *      ext2_alloc_block() (normally -ENOSPC). Otherwise we set the chain
473  *      as described above and return 0.
474  */
475 
476 static int ext2_alloc_branch(struct inode *inode,
477                         int indirect_blks, int *blks, ext2_fsblk_t goal,
478                         int *offsets, Indirect *branch)
479 {
480         int blocksize = inode->i_sb->s_blocksize;
481         int i, n = 0;
482         int err = 0;
483         struct buffer_head *bh;
484         int num;
485         ext2_fsblk_t new_blocks[4];
486         ext2_fsblk_t current_block;
487 
488         num = ext2_alloc_blocks(inode, goal, indirect_blks,
489                                 *blks, new_blocks, &err);
490         if (err)
491                 return err;
492 
493         branch[0].key = cpu_to_le32(new_blocks[0]);
494         /*
495          * metadata blocks and data blocks are allocated.
496          */
497         for (n = 1; n <= indirect_blks;  n++) {
498                 /*
499                  * Get buffer_head for parent block, zero it out
500                  * and set the pointer to new one, then send
501                  * parent to disk.
502                  */
503                 bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
504                 if (unlikely(!bh)) {
505                         err = -ENOMEM;
506                         goto failed;
507                 }
508                 branch[n].bh = bh;
509                 lock_buffer(bh);
510                 memset(bh->b_data, 0, blocksize);
511                 branch[n].p = (__le32 *) bh->b_data + offsets[n];
512                 branch[n].key = cpu_to_le32(new_blocks[n]);
513                 *branch[n].p = branch[n].key;
514                 if ( n == indirect_blks) {
515                         current_block = new_blocks[n];
516                         /*
517                          * End of chain, update the last new metablock of
518                          * the chain to point to the new allocated
519                          * data blocks numbers
520                          */
521                         for (i=1; i < num; i++)
522                                 *(branch[n].p + i) = cpu_to_le32(++current_block);
523                 }
524                 set_buffer_uptodate(bh);
525                 unlock_buffer(bh);
526                 mark_buffer_dirty_inode(bh, inode);
527                 /* We used to sync bh here if IS_SYNC(inode).
528                  * But we now rely upon generic_write_sync()
529                  * and b_inode_buffers.  But not for directories.
530                  */
531                 if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode))
532                         sync_dirty_buffer(bh);
533         }
534         *blks = num;
535         return err;
536 
537 failed:
538         for (i = 1; i < n; i++)
539                 bforget(branch[i].bh);
540         for (i = 0; i < indirect_blks; i++)
541                 ext2_free_blocks(inode, new_blocks[i], 1);
542         ext2_free_blocks(inode, new_blocks[i], num);
543         return err;
544 }
545 
546 /**
547  * ext2_splice_branch - splice the allocated branch onto inode.
548  * @inode: owner
549  * @block: (logical) number of block we are adding
550  * @where: location of missing link
551  * @num:   number of indirect blocks we are adding
552  * @blks:  number of direct blocks we are adding
553  *
554  * This function fills the missing link and does all housekeeping needed in
555  * inode (->i_blocks, etc.). In case of success we end up with the full
556  * chain to new block and return 0.
557  */
558 static void ext2_splice_branch(struct inode *inode,
559                         long block, Indirect *where, int num, int blks)
560 {
561         int i;
562         struct ext2_block_alloc_info *block_i;
563         ext2_fsblk_t current_block;
564 
565         block_i = EXT2_I(inode)->i_block_alloc_info;
566 
567         /* XXX LOCKING probably should have i_meta_lock ?*/
568         /* That's it */
569 
570         *where->p = where->key;
571 
572         /*
573          * Update the host buffer_head or inode to point to more just allocated
574          * direct blocks blocks
575          */
576         if (num == 0 && blks > 1) {
577                 current_block = le32_to_cpu(where->key) + 1;
578                 for (i = 1; i < blks; i++)
579                         *(where->p + i ) = cpu_to_le32(current_block++);
580         }
581 
582         /*
583          * update the most recently allocated logical & physical block
584          * in i_block_alloc_info, to assist find the proper goal block for next
585          * allocation
586          */
587         if (block_i) {
588                 block_i->last_alloc_logical_block = block + blks - 1;
589                 block_i->last_alloc_physical_block =
590                                 le32_to_cpu(where[num].key) + blks - 1;
591         }
592 
593         /* We are done with atomic stuff, now do the rest of housekeeping */
594 
595         /* had we spliced it onto indirect block? */
596         if (where->bh)
597                 mark_buffer_dirty_inode(where->bh, inode);
598 
599         inode->i_ctime = current_time(inode);
600         mark_inode_dirty(inode);
601 }
602 
603 /*
604  * Allocation strategy is simple: if we have to allocate something, we will
605  * have to go the whole way to leaf. So let's do it before attaching anything
606  * to tree, set linkage between the newborn blocks, write them if sync is
607  * required, recheck the path, free and repeat if check fails, otherwise
608  * set the last missing link (that will protect us from any truncate-generated
609  * removals - all blocks on the path are immune now) and possibly force the
610  * write on the parent block.
611  * That has a nice additional property: no special recovery from the failed
612  * allocations is needed - we simply release blocks and do not touch anything
613  * reachable from inode.
614  *
615  * `handle' can be NULL if create == 0.
616  *
617  * return > 0, # of blocks mapped or allocated.
618  * return = 0, if plain lookup failed.
619  * return < 0, error case.
620  */
621 static int ext2_get_blocks(struct inode *inode,
622                            sector_t iblock, unsigned long maxblocks,
623                            u32 *bno, bool *new, bool *boundary,
624                            int create)
625 {
626         int err;
627         int offsets[4];
628         Indirect chain[4];
629         Indirect *partial;
630         ext2_fsblk_t goal;
631         int indirect_blks;
632         int blocks_to_boundary = 0;
633         int depth;
634         struct ext2_inode_info *ei = EXT2_I(inode);
635         int count = 0;
636         ext2_fsblk_t first_block = 0;
637 
638         BUG_ON(maxblocks == 0);
639 
640         depth = ext2_block_to_path(inode,iblock,offsets,&blocks_to_boundary);
641 
642         if (depth == 0)
643                 return -EIO;
644 
645         partial = ext2_get_branch(inode, depth, offsets, chain, &err);
646         /* Simplest case - block found, no allocation needed */
647         if (!partial) {
648                 first_block = le32_to_cpu(chain[depth - 1].key);
649                 count++;
650                 /*map more blocks*/
651                 while (count < maxblocks && count <= blocks_to_boundary) {
652                         ext2_fsblk_t blk;
653 
654                         if (!verify_chain(chain, chain + depth - 1)) {
655                                 /*
656                                  * Indirect block might be removed by
657                                  * truncate while we were reading it.
658                                  * Handling of that case: forget what we've
659                                  * got now, go to reread.
660                                  */
661                                 err = -EAGAIN;
662                                 count = 0;
663                                 partial = chain + depth - 1;
664                                 break;
665                         }
666                         blk = le32_to_cpu(*(chain[depth-1].p + count));
667                         if (blk == first_block + count)
668                                 count++;
669                         else
670                                 break;
671                 }
672                 if (err != -EAGAIN)
673                         goto got_it;
674         }
675 
676         /* Next simple case - plain lookup or failed read of indirect block */
677         if (!create || err == -EIO)
678                 goto cleanup;
679 
680         mutex_lock(&ei->truncate_mutex);
681         /*
682          * If the indirect block is missing while we are reading
683          * the chain(ext2_get_branch() returns -EAGAIN err), or
684          * if the chain has been changed after we grab the semaphore,
685          * (either because another process truncated this branch, or
686          * another get_block allocated this branch) re-grab the chain to see if
687          * the request block has been allocated or not.
688          *
689          * Since we already block the truncate/other get_block
690          * at this point, we will have the current copy of the chain when we
691          * splice the branch into the tree.
692          */
693         if (err == -EAGAIN || !verify_chain(chain, partial)) {
694                 while (partial > chain) {
695                         brelse(partial->bh);
696                         partial--;
697                 }
698                 partial = ext2_get_branch(inode, depth, offsets, chain, &err);
699                 if (!partial) {
700                         count++;
701                         mutex_unlock(&ei->truncate_mutex);
702                         goto got_it;
703                 }
704 
705                 if (err) {
706                         mutex_unlock(&ei->truncate_mutex);
707                         goto cleanup;
708                 }
709         }
710 
711         /*
712          * Okay, we need to do block allocation.  Lazily initialize the block
713          * allocation info here if necessary
714         */
715         if (S_ISREG(inode->i_mode) && (!ei->i_block_alloc_info))
716                 ext2_init_block_alloc_info(inode);
717 
718         goal = ext2_find_goal(inode, iblock, partial);
719 
720         /* the number of blocks need to allocate for [d,t]indirect blocks */
721         indirect_blks = (chain + depth) - partial - 1;
722         /*
723          * Next look up the indirect map to count the total number of
724          * direct blocks to allocate for this branch.
725          */
726         count = ext2_blks_to_allocate(partial, indirect_blks,
727                                         maxblocks, blocks_to_boundary);
728         /*
729          * XXX ???? Block out ext2_truncate while we alter the tree
730          */
731         err = ext2_alloc_branch(inode, indirect_blks, &count, goal,
732                                 offsets + (partial - chain), partial);
733 
734         if (err) {
735                 mutex_unlock(&ei->truncate_mutex);
736                 goto cleanup;
737         }
738 
739         if (IS_DAX(inode)) {
740                 /*
741                  * We must unmap blocks before zeroing so that writeback cannot
742                  * overwrite zeros with stale data from block device page cache.
743                  */
744                 clean_bdev_aliases(inode->i_sb->s_bdev,
745                                    le32_to_cpu(chain[depth-1].key),
746                                    count);
747                 /*
748                  * block must be initialised before we put it in the tree
749                  * so that it's not found by another thread before it's
750                  * initialised
751                  */
752                 err = sb_issue_zeroout(inode->i_sb,
753                                 le32_to_cpu(chain[depth-1].key), count,
754                                 GFP_NOFS);
755                 if (err) {
756                         mutex_unlock(&ei->truncate_mutex);
757                         goto cleanup;
758                 }
759         }
760         *new = true;
761 
762         ext2_splice_branch(inode, iblock, partial, indirect_blks, count);
763         mutex_unlock(&ei->truncate_mutex);
764 got_it:
765         if (count > blocks_to_boundary)
766                 *boundary = true;
767         err = count;
768         /* Clean up and exit */
769         partial = chain + depth - 1;    /* the whole chain */
770 cleanup:
771         while (partial > chain) {
772                 brelse(partial->bh);
773                 partial--;
774         }
775         if (err > 0)
776                 *bno = le32_to_cpu(chain[depth-1].key);
777         return err;
778 }
779 
780 int ext2_get_block(struct inode *inode, sector_t iblock,
781                 struct buffer_head *bh_result, int create)
782 {
783         unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
784         bool new = false, boundary = false;
785         u32 bno;
786         int ret;
787 
788         ret = ext2_get_blocks(inode, iblock, max_blocks, &bno, &new, &boundary,
789                         create);
790         if (ret <= 0)
791                 return ret;
792 
793         map_bh(bh_result, inode->i_sb, bno);
794         bh_result->b_size = (ret << inode->i_blkbits);
795         if (new)
796                 set_buffer_new(bh_result);
797         if (boundary)
798                 set_buffer_boundary(bh_result);
799         return 0;
800 
801 }
802 
803 #ifdef CONFIG_FS_DAX
804 static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
805                 unsigned flags, struct iomap *iomap, struct iomap *srcmap)
806 {
807         unsigned int blkbits = inode->i_blkbits;
808         unsigned long first_block = offset >> blkbits;
809         unsigned long max_blocks = (length + (1 << blkbits) - 1) >> blkbits;
810         struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
811         bool new = false, boundary = false;
812         u32 bno;
813         int ret;
814 
815         ret = ext2_get_blocks(inode, first_block, max_blocks,
816                         &bno, &new, &boundary, flags & IOMAP_WRITE);
817         if (ret < 0)
818                 return ret;
819 
820         iomap->flags = 0;
821         iomap->bdev = inode->i_sb->s_bdev;
822         iomap->offset = (u64)first_block << blkbits;
823         iomap->dax_dev = sbi->s_daxdev;
824 
825         if (ret == 0) {
826                 iomap->type = IOMAP_HOLE;
827                 iomap->addr = IOMAP_NULL_ADDR;
828                 iomap->length = 1 << blkbits;
829         } else {
830                 iomap->type = IOMAP_MAPPED;
831                 iomap->addr = (u64)bno << blkbits;
832                 iomap->length = (u64)ret << blkbits;
833                 iomap->flags |= IOMAP_F_MERGED;
834         }
835 
836         if (new)
837                 iomap->flags |= IOMAP_F_NEW;
838         return 0;
839 }
840 
841 static int
842 ext2_iomap_end(struct inode *inode, loff_t offset, loff_t length,
843                 ssize_t written, unsigned flags, struct iomap *iomap)
844 {
845         if (iomap->type == IOMAP_MAPPED &&
846             written < length &&
847             (flags & IOMAP_WRITE))
848                 ext2_write_failed(inode->i_mapping, offset + length);
849         return 0;
850 }
851 
852 const struct iomap_ops ext2_iomap_ops = {
853         .iomap_begin            = ext2_iomap_begin,
854         .iomap_end              = ext2_iomap_end,
855 };
856 #else
857 /* Define empty ops for !CONFIG_FS_DAX case to avoid ugly ifdefs */
858 const struct iomap_ops ext2_iomap_ops;
859 #endif /* CONFIG_FS_DAX */
860 
861 int ext2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
862                 u64 start, u64 len)
863 {
864         return generic_block_fiemap(inode, fieinfo, start, len,
865                                     ext2_get_block);
866 }
867 
868 static int ext2_writepage(struct page *page, struct writeback_control *wbc)
869 {
870         return block_write_full_page(page, ext2_get_block, wbc);
871 }
872 
873 static int ext2_readpage(struct file *file, struct page *page)
874 {
875         return mpage_readpage(page, ext2_get_block);
876 }
877 
878 static void ext2_readahead(struct readahead_control *rac)
879 {
880         mpage_readahead(rac, ext2_get_block);
881 }
882 
883 static int
884 ext2_write_begin(struct file *file, struct address_space *mapping,
885                 loff_t pos, unsigned len, unsigned flags,
886                 struct page **pagep, void **fsdata)
887 {
888         int ret;
889 
890         ret = block_write_begin(mapping, pos, len, flags, pagep,
891                                 ext2_get_block);
892         if (ret < 0)
893                 ext2_write_failed(mapping, pos + len);
894         return ret;
895 }
896 
897 static int ext2_write_end(struct file *file, struct address_space *mapping,
898                         loff_t pos, unsigned len, unsigned copied,
899                         struct page *page, void *fsdata)
900 {
901         int ret;
902 
903         ret = generic_write_end(file, mapping, pos, len, copied, page, fsdata);
904         if (ret < len)
905                 ext2_write_failed(mapping, pos + len);
906         return ret;
907 }
908 
909 static int
910 ext2_nobh_write_begin(struct file *file, struct address_space *mapping,
911                 loff_t pos, unsigned len, unsigned flags,
912                 struct page **pagep, void **fsdata)
913 {
914         int ret;
915 
916         ret = nobh_write_begin(mapping, pos, len, flags, pagep, fsdata,
917                                ext2_get_block);
918         if (ret < 0)
919                 ext2_write_failed(mapping, pos + len);
920         return ret;
921 }
922 
923 static int ext2_nobh_writepage(struct page *page,
924                         struct writeback_control *wbc)
925 {
926         return nobh_writepage(page, ext2_get_block, wbc);
927 }
928 
929 static sector_t ext2_bmap(struct address_space *mapping, sector_t block)
930 {
931         return generic_block_bmap(mapping,block,ext2_get_block);
932 }
933 
934 static ssize_t
935 ext2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
936 {
937         struct file *file = iocb->ki_filp;
938         struct address_space *mapping = file->f_mapping;
939         struct inode *inode = mapping->host;
940         size_t count = iov_iter_count(iter);
941         loff_t offset = iocb->ki_pos;
942         ssize_t ret;
943 
944         ret = blockdev_direct_IO(iocb, inode, iter, ext2_get_block);
945         if (ret < 0 && iov_iter_rw(iter) == WRITE)
946                 ext2_write_failed(mapping, offset + count);
947         return ret;
948 }
949 
950 static int
951 ext2_writepages(struct address_space *mapping, struct writeback_control *wbc)
952 {
953         return mpage_writepages(mapping, wbc, ext2_get_block);
954 }
955 
956 static int
957 ext2_dax_writepages(struct address_space *mapping, struct writeback_control *wbc)
958 {
959         struct ext2_sb_info *sbi = EXT2_SB(mapping->host->i_sb);
960 
961         return dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
962 }
963 
964 const struct address_space_operations ext2_aops = {
965         .readpage               = ext2_readpage,
966         .readahead              = ext2_readahead,
967         .writepage              = ext2_writepage,
968         .write_begin            = ext2_write_begin,
969         .write_end              = ext2_write_end,
970         .bmap                   = ext2_bmap,
971         .direct_IO              = ext2_direct_IO,
972         .writepages             = ext2_writepages,
973         .migratepage            = buffer_migrate_page,
974         .is_partially_uptodate  = block_is_partially_uptodate,
975         .error_remove_page      = generic_error_remove_page,
976 };
977 
978 const struct address_space_operations ext2_nobh_aops = {
979         .readpage               = ext2_readpage,
980         .readahead              = ext2_readahead,
981         .writepage              = ext2_nobh_writepage,
982         .write_begin            = ext2_nobh_write_begin,
983         .write_end              = nobh_write_end,
984         .bmap                   = ext2_bmap,
985         .direct_IO              = ext2_direct_IO,
986         .writepages             = ext2_writepages,
987         .migratepage            = buffer_migrate_page,
988         .error_remove_page      = generic_error_remove_page,
989 };
990 
991 static const struct address_space_operations ext2_dax_aops = {
992         .writepages             = ext2_dax_writepages,
993         .direct_IO              = noop_direct_IO,
994         .set_page_dirty         = noop_set_page_dirty,
995         .invalidatepage         = noop_invalidatepage,
996 };
997 
998 /*
999  * Probably it should be a library function... search for first non-zero word
1000  * or memcmp with zero_page, whatever is better for particular architecture.
1001  * Linus?
1002  */
1003 static inline int all_zeroes(__le32 *p, __le32 *q)
1004 {
1005         while (p < q)
1006                 if (*p++)
1007                         return 0;
1008         return 1;
1009 }
1010 
1011 /**
1012  *      ext2_find_shared - find the indirect blocks for partial truncation.
1013  *      @inode:   inode in question
1014  *      @depth:   depth of the affected branch
1015  *      @offsets: offsets of pointers in that branch (see ext2_block_to_path)
1016  *      @chain:   place to store the pointers to partial indirect blocks
1017  *      @top:     place to the (detached) top of branch
1018  *
1019  *      This is a helper function used by ext2_truncate().
1020  *
1021  *      When we do truncate() we may have to clean the ends of several indirect
1022  *      blocks but leave the blocks themselves alive. Block is partially
1023  *      truncated if some data below the new i_size is referred from it (and
1024  *      it is on the path to the first completely truncated data block, indeed).
1025  *      We have to free the top of that path along with everything to the right
1026  *      of the path. Since no allocation past the truncation point is possible
1027  *      until ext2_truncate() finishes, we may safely do the latter, but top
1028  *      of branch may require special attention - pageout below the truncation
1029  *      point might try to populate it.
1030  *
1031  *      We atomically detach the top of branch from the tree, store the block
1032  *      number of its root in *@top, pointers to buffer_heads of partially
1033  *      truncated blocks - in @chain[].bh and pointers to their last elements
1034  *      that should not be removed - in @chain[].p. Return value is the pointer
1035  *      to last filled element of @chain.
1036  *
1037  *      The work left to caller to do the actual freeing of subtrees:
1038  *              a) free the subtree starting from *@top
1039  *              b) free the subtrees whose roots are stored in
1040  *                      (@chain[i].p+1 .. end of @chain[i].bh->b_data)
1041  *              c) free the subtrees growing from the inode past the @chain[0].p
1042  *                      (no partially truncated stuff there).
1043  */
1044 
1045 static Indirect *ext2_find_shared(struct inode *inode,
1046                                 int depth,
1047                                 int offsets[4],
1048                                 Indirect chain[4],
1049                                 __le32 *top)
1050 {
1051         Indirect *partial, *p;
1052         int k, err;
1053 
1054         *top = 0;
1055         for (k = depth; k > 1 && !offsets[k-1]; k--)
1056                 ;
1057         partial = ext2_get_branch(inode, k, offsets, chain, &err);
1058         if (!partial)
1059                 partial = chain + k-1;
1060         /*
1061          * If the branch acquired continuation since we've looked at it -
1062          * fine, it should all survive and (new) top doesn't belong to us.
1063          */
1064         write_lock(&EXT2_I(inode)->i_meta_lock);
1065         if (!partial->key && *partial->p) {
1066                 write_unlock(&EXT2_I(inode)->i_meta_lock);
1067                 goto no_top;
1068         }
1069         for (p=partial; p>chain && all_zeroes((__le32*)p->bh->b_data,p->p); p--)
1070                 ;
1071         /*
1072          * OK, we've found the last block that must survive. The rest of our
1073          * branch should be detached before unlocking. However, if that rest
1074          * of branch is all ours and does not grow immediately from the inode
1075          * it's easier to cheat and just decrement partial->p.
1076          */
1077         if (p == chain + k - 1 && p > chain) {
1078                 p->p--;
1079         } else {
1080                 *top = *p->p;
1081                 *p->p = 0;
1082         }
1083         write_unlock(&EXT2_I(inode)->i_meta_lock);
1084 
1085         while(partial > p)
1086         {
1087                 brelse(partial->bh);
1088                 partial--;
1089         }
1090 no_top:
1091         return partial;
1092 }
1093 
1094 /**
1095  *      ext2_free_data - free a list of data blocks
1096  *      @inode: inode we are dealing with
1097  *      @p:     array of block numbers
1098  *      @q:     points immediately past the end of array
1099  *
1100  *      We are freeing all blocks referred from that array (numbers are
1101  *      stored as little-endian 32-bit) and updating @inode->i_blocks
1102  *      appropriately.
1103  */
1104 static inline void ext2_free_data(struct inode *inode, __le32 *p, __le32 *q)
1105 {
1106         unsigned long block_to_free = 0, count = 0;
1107         unsigned long nr;
1108 
1109         for ( ; p < q ; p++) {
1110                 nr = le32_to_cpu(*p);
1111                 if (nr) {
1112                         *p = 0;
1113                         /* accumulate blocks to free if they're contiguous */
1114                         if (count == 0)
1115                                 goto free_this;
1116                         else if (block_to_free == nr - count)
1117                                 count++;
1118                         else {
1119                                 ext2_free_blocks (inode, block_to_free, count);
1120                                 mark_inode_dirty(inode);
1121                         free_this:
1122                                 block_to_free = nr;
1123                                 count = 1;
1124                         }
1125                 }
1126         }
1127         if (count > 0) {
1128                 ext2_free_blocks (inode, block_to_free, count);
1129                 mark_inode_dirty(inode);
1130         }
1131 }
1132 
1133 /**
1134  *      ext2_free_branches - free an array of branches
1135  *      @inode: inode we are dealing with
1136  *      @p:     array of block numbers
1137  *      @q:     pointer immediately past the end of array
1138  *      @depth: depth of the branches to free
1139  *
1140  *      We are freeing all blocks referred from these branches (numbers are
1141  *      stored as little-endian 32-bit) and updating @inode->i_blocks
1142  *      appropriately.
1143  */
1144 static void ext2_free_branches(struct inode *inode, __le32 *p, __le32 *q, int depth)
1145 {
1146         struct buffer_head * bh;
1147         unsigned long nr;
1148 
1149         if (depth--) {
1150                 int addr_per_block = EXT2_ADDR_PER_BLOCK(inode->i_sb);
1151                 for ( ; p < q ; p++) {
1152                         nr = le32_to_cpu(*p);
1153                         if (!nr)
1154                                 continue;
1155                         *p = 0;
1156                         bh = sb_bread(inode->i_sb, nr);
1157                         /*
1158                          * A read failure? Report error and clear slot
1159                          * (should be rare).
1160                          */ 
1161                         if (!bh) {
1162                                 ext2_error(inode->i_sb, "ext2_free_branches",
1163                                         "Read failure, inode=%ld, block=%ld",
1164                                         inode->i_ino, nr);
1165                                 continue;
1166                         }
1167                         ext2_free_branches(inode,
1168                                            (__le32*)bh->b_data,
1169                                            (__le32*)bh->b_data + addr_per_block,
1170                                            depth);
1171                         bforget(bh);
1172                         ext2_free_blocks(inode, nr, 1);
1173                         mark_inode_dirty(inode);
1174                 }
1175         } else
1176                 ext2_free_data(inode, p, q);
1177 }
1178 
1179 /* dax_sem must be held when calling this function */
1180 static void __ext2_truncate_blocks(struct inode *inode, loff_t offset)
1181 {
1182         __le32 *i_data = EXT2_I(inode)->i_data;
1183         struct ext2_inode_info *ei = EXT2_I(inode);
1184         int addr_per_block = EXT2_ADDR_PER_BLOCK(inode->i_sb);
1185         int offsets[4];
1186         Indirect chain[4];
1187         Indirect *partial;
1188         __le32 nr = 0;
1189         int n;
1190         long iblock;
1191         unsigned blocksize;
1192         blocksize = inode->i_sb->s_blocksize;
1193         iblock = (offset + blocksize-1) >> EXT2_BLOCK_SIZE_BITS(inode->i_sb);
1194 
1195 #ifdef CONFIG_FS_DAX
1196         WARN_ON(!rwsem_is_locked(&ei->dax_sem));
1197 #endif
1198 
1199         n = ext2_block_to_path(inode, iblock, offsets, NULL);
1200         if (n == 0)
1201                 return;
1202 
1203         /*
1204          * From here we block out all ext2_get_block() callers who want to
1205          * modify the block allocation tree.
1206          */
1207         mutex_lock(&ei->truncate_mutex);
1208 
1209         if (n == 1) {
1210                 ext2_free_data(inode, i_data+offsets[0],
1211                                         i_data + EXT2_NDIR_BLOCKS);
1212                 goto do_indirects;
1213         }
1214 
1215         partial = ext2_find_shared(inode, n, offsets, chain, &nr);
1216         /* Kill the top of shared branch (already detached) */
1217         if (nr) {
1218                 if (partial == chain)
1219                         mark_inode_dirty(inode);
1220                 else
1221                         mark_buffer_dirty_inode(partial->bh, inode);
1222                 ext2_free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
1223         }
1224         /* Clear the ends of indirect blocks on the shared branch */
1225         while (partial > chain) {
1226                 ext2_free_branches(inode,
1227                                    partial->p + 1,
1228                                    (__le32*)partial->bh->b_data+addr_per_block,
1229                                    (chain+n-1) - partial);
1230                 mark_buffer_dirty_inode(partial->bh, inode);
1231                 brelse (partial->bh);
1232                 partial--;
1233         }
1234 do_indirects:
1235         /* Kill the remaining (whole) subtrees */
1236         switch (offsets[0]) {
1237                 default:
1238                         nr = i_data[EXT2_IND_BLOCK];
1239                         if (nr) {
1240                                 i_data[EXT2_IND_BLOCK] = 0;
1241                                 mark_inode_dirty(inode);
1242                                 ext2_free_branches(inode, &nr, &nr+1, 1);
1243                         }
1244                         fallthrough;
1245                 case EXT2_IND_BLOCK:
1246                         nr = i_data[EXT2_DIND_BLOCK];
1247                         if (nr) {
1248                                 i_data[EXT2_DIND_BLOCK] = 0;
1249                                 mark_inode_dirty(inode);
1250                                 ext2_free_branches(inode, &nr, &nr+1, 2);
1251                         }
1252                         fallthrough;
1253                 case EXT2_DIND_BLOCK:
1254                         nr = i_data[EXT2_TIND_BLOCK];
1255                         if (nr) {
1256                                 i_data[EXT2_TIND_BLOCK] = 0;
1257                                 mark_inode_dirty(inode);
1258                                 ext2_free_branches(inode, &nr, &nr+1, 3);
1259                         }
1260                 case EXT2_TIND_BLOCK:
1261                         ;
1262         }
1263 
1264         ext2_discard_reservation(inode);
1265 
1266         mutex_unlock(&ei->truncate_mutex);
1267 }
1268 
1269 static void ext2_truncate_blocks(struct inode *inode, loff_t offset)
1270 {
1271         if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
1272             S_ISLNK(inode->i_mode)))
1273                 return;
1274         if (ext2_inode_is_fast_symlink(inode))
1275                 return;
1276 
1277         dax_sem_down_write(EXT2_I(inode));
1278         __ext2_truncate_blocks(inode, offset);
1279         dax_sem_up_write(EXT2_I(inode));
1280 }
1281 
1282 static int ext2_setsize(struct inode *inode, loff_t newsize)
1283 {
1284         int error;
1285 
1286         if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
1287             S_ISLNK(inode->i_mode)))
1288                 return -EINVAL;
1289         if (ext2_inode_is_fast_symlink(inode))
1290                 return -EINVAL;
1291         if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
1292                 return -EPERM;
1293 
1294         inode_dio_wait(inode);
1295 
1296         if (IS_DAX(inode)) {
1297                 error = iomap_zero_range(inode, newsize,
1298                                          PAGE_ALIGN(newsize) - newsize, NULL,
1299                                          &ext2_iomap_ops);
1300         } else if (test_opt(inode->i_sb, NOBH))
1301                 error = nobh_truncate_page(inode->i_mapping,
1302                                 newsize, ext2_get_block);
1303         else
1304                 error = block_truncate_page(inode->i_mapping,
1305                                 newsize, ext2_get_block);
1306         if (error)
1307                 return error;
1308 
1309         dax_sem_down_write(EXT2_I(inode));
1310         truncate_setsize(inode, newsize);
1311         __ext2_truncate_blocks(inode, newsize);
1312         dax_sem_up_write(EXT2_I(inode));
1313 
1314         inode->i_mtime = inode->i_ctime = current_time(inode);
1315         if (inode_needs_sync(inode)) {
1316                 sync_mapping_buffers(inode->i_mapping);
1317                 sync_inode_metadata(inode, 1);
1318         } else {
1319                 mark_inode_dirty(inode);
1320         }
1321 
1322         return 0;
1323 }
1324 
1325 static struct ext2_inode *ext2_get_inode(struct super_block *sb, ino_t ino,
1326                                         struct buffer_head **p)
1327 {
1328         struct buffer_head * bh;
1329         unsigned long block_group;
1330         unsigned long block;
1331         unsigned long offset;
1332         struct ext2_group_desc * gdp;
1333 
1334         *p = NULL;
1335         if ((ino != EXT2_ROOT_INO && ino < EXT2_FIRST_INO(sb)) ||
1336             ino > le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count))
1337                 goto Einval;
1338 
1339         block_group = (ino - 1) / EXT2_INODES_PER_GROUP(sb);
1340         gdp = ext2_get_group_desc(sb, block_group, NULL);
1341         if (!gdp)
1342                 goto Egdp;
1343         /*
1344          * Figure out the offset within the block group inode table
1345          */
1346         offset = ((ino - 1) % EXT2_INODES_PER_GROUP(sb)) * EXT2_INODE_SIZE(sb);
1347         block = le32_to_cpu(gdp->bg_inode_table) +
1348                 (offset >> EXT2_BLOCK_SIZE_BITS(sb));
1349         if (!(bh = sb_bread(sb, block)))
1350                 goto Eio;
1351 
1352         *p = bh;
1353         offset &= (EXT2_BLOCK_SIZE(sb) - 1);
1354         return (struct ext2_inode *) (bh->b_data + offset);
1355 
1356 Einval:
1357         ext2_error(sb, "ext2_get_inode", "bad inode number: %lu",
1358                    (unsigned long) ino);
1359         return ERR_PTR(-EINVAL);
1360 Eio:
1361         ext2_error(sb, "ext2_get_inode",
1362                    "unable to read inode block - inode=%lu, block=%lu",
1363                    (unsigned long) ino, block);
1364 Egdp:
1365         return ERR_PTR(-EIO);
1366 }
1367 
1368 void ext2_set_inode_flags(struct inode *inode)
1369 {
1370         unsigned int flags = EXT2_I(inode)->i_flags;
1371 
1372         inode->i_flags &= ~(S_SYNC | S_APPEND | S_IMMUTABLE | S_NOATIME |
1373                                 S_DIRSYNC | S_DAX);
1374         if (flags & EXT2_SYNC_FL)
1375                 inode->i_flags |= S_SYNC;
1376         if (flags & EXT2_APPEND_FL)
1377                 inode->i_flags |= S_APPEND;
1378         if (flags & EXT2_IMMUTABLE_FL)
1379                 inode->i_flags |= S_IMMUTABLE;
1380         if (flags & EXT2_NOATIME_FL)
1381                 inode->i_flags |= S_NOATIME;
1382         if (flags & EXT2_DIRSYNC_FL)
1383                 inode->i_flags |= S_DIRSYNC;
1384         if (test_opt(inode->i_sb, DAX) && S_ISREG(inode->i_mode))
1385                 inode->i_flags |= S_DAX;
1386 }
1387 
1388 void ext2_set_file_ops(struct inode *inode)
1389 {
1390         inode->i_op = &ext2_file_inode_operations;
1391         inode->i_fop = &ext2_file_operations;
1392         if (IS_DAX(inode))
1393                 inode->i_mapping->a_ops = &ext2_dax_aops;
1394         else if (test_opt(inode->i_sb, NOBH))
1395                 inode->i_mapping->a_ops = &ext2_nobh_aops;
1396         else
1397                 inode->i_mapping->a_ops = &ext2_aops;
1398 }
1399 
1400 struct inode *ext2_iget (struct super_block *sb, unsigned long ino)
1401 {
1402         struct ext2_inode_info *ei;
1403         struct buffer_head * bh = NULL;
1404         struct ext2_inode *raw_inode;
1405         struct inode *inode;
1406         long ret = -EIO;
1407         int n;
1408         uid_t i_uid;
1409         gid_t i_gid;
1410 
1411         inode = iget_locked(sb, ino);
1412         if (!inode)
1413                 return ERR_PTR(-ENOMEM);
1414         if (!(inode->i_state & I_NEW))
1415                 return inode;
1416 
1417         ei = EXT2_I(inode);
1418         ei->i_block_alloc_info = NULL;
1419 
1420         raw_inode = ext2_get_inode(inode->i_sb, ino, &bh);
1421         if (IS_ERR(raw_inode)) {
1422                 ret = PTR_ERR(raw_inode);
1423                 goto bad_inode;
1424         }
1425 
1426         inode->i_mode = le16_to_cpu(raw_inode->i_mode);
1427         i_uid = (uid_t)le16_to_cpu(raw_inode->i_uid_low);
1428         i_gid = (gid_t)le16_to_cpu(raw_inode->i_gid_low);
1429         if (!(test_opt (inode->i_sb, NO_UID32))) {
1430                 i_uid |= le16_to_cpu(raw_inode->i_uid_high) << 16;
1431                 i_gid |= le16_to_cpu(raw_inode->i_gid_high) << 16;
1432         }
1433         i_uid_write(inode, i_uid);
1434         i_gid_write(inode, i_gid);
1435         set_nlink(inode, le16_to_cpu(raw_inode->i_links_count));
1436         inode->i_size = le32_to_cpu(raw_inode->i_size);
1437         inode->i_atime.tv_sec = (signed)le32_to_cpu(raw_inode->i_atime);
1438         inode->i_ctime.tv_sec = (signed)le32_to_cpu(raw_inode->i_ctime);
1439         inode->i_mtime.tv_sec = (signed)le32_to_cpu(raw_inode->i_mtime);
1440         inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0;
1441         ei->i_dtime = le32_to_cpu(raw_inode->i_dtime);
1442         /* We now have enough fields to check if the inode was active or not.
1443          * This is needed because nfsd might try to access dead inodes
1444          * the test is that same one that e2fsck uses
1445          * NeilBrown 1999oct15
1446          */
1447         if (inode->i_nlink == 0 && (inode->i_mode == 0 || ei->i_dtime)) {
1448                 /* this inode is deleted */
1449                 ret = -ESTALE;
1450                 goto bad_inode;
1451         }
1452         inode->i_blocks = le32_to_cpu(raw_inode->i_blocks);
1453         ei->i_flags = le32_to_cpu(raw_inode->i_flags);
1454         ext2_set_inode_flags(inode);
1455         ei->i_faddr = le32_to_cpu(raw_inode->i_faddr);
1456         ei->i_frag_no = raw_inode->i_frag;
1457         ei->i_frag_size = raw_inode->i_fsize;
1458         ei->i_file_acl = le32_to_cpu(raw_inode->i_file_acl);
1459         ei->i_dir_acl = 0;
1460 
1461         if (ei->i_file_acl &&
1462             !ext2_data_block_valid(EXT2_SB(sb), ei->i_file_acl, 1)) {
1463                 ext2_error(sb, "ext2_iget", "bad extended attribute block %u",
1464                            ei->i_file_acl);
1465                 ret = -EFSCORRUPTED;
1466                 goto bad_inode;
1467         }
1468 
1469         if (S_ISREG(inode->i_mode))
1470                 inode->i_size |= ((__u64)le32_to_cpu(raw_inode->i_size_high)) << 32;
1471         else
1472                 ei->i_dir_acl = le32_to_cpu(raw_inode->i_dir_acl);
1473         if (i_size_read(inode) < 0) {
1474                 ret = -EFSCORRUPTED;
1475                 goto bad_inode;
1476         }
1477         ei->i_dtime = 0;
1478         inode->i_generation = le32_to_cpu(raw_inode->i_generation);
1479         ei->i_state = 0;
1480         ei->i_block_group = (ino - 1) / EXT2_INODES_PER_GROUP(inode->i_sb);
1481         ei->i_dir_start_lookup = 0;
1482 
1483         /*
1484          * NOTE! The in-memory inode i_data array is in little-endian order
1485          * even on big-endian machines: we do NOT byteswap the block numbers!
1486          */
1487         for (n = 0; n < EXT2_N_BLOCKS; n++)
1488                 ei->i_data[n] = raw_inode->i_block[n];
1489 
1490         if (S_ISREG(inode->i_mode)) {
1491                 ext2_set_file_ops(inode);
1492         } else if (S_ISDIR(inode->i_mode)) {
1493                 inode->i_op = &ext2_dir_inode_operations;
1494                 inode->i_fop = &ext2_dir_operations;
1495                 if (test_opt(inode->i_sb, NOBH))
1496                         inode->i_mapping->a_ops = &ext2_nobh_aops;
1497                 else
1498                         inode->i_mapping->a_ops = &ext2_aops;
1499         } else if (S_ISLNK(inode->i_mode)) {
1500                 if (ext2_inode_is_fast_symlink(inode)) {
1501                         inode->i_link = (char *)ei->i_data;
1502                         inode->i_op = &ext2_fast_symlink_inode_operations;
1503                         nd_terminate_link(ei->i_data, inode->i_size,
1504                                 sizeof(ei->i_data) - 1);
1505                 } else {
1506                         inode->i_op = &ext2_symlink_inode_operations;
1507                         inode_nohighmem(inode);
1508                         if (test_opt(inode->i_sb, NOBH))
1509                                 inode->i_mapping->a_ops = &ext2_nobh_aops;
1510                         else
1511                                 inode->i_mapping->a_ops = &ext2_aops;
1512                 }
1513         } else {
1514                 inode->i_op = &ext2_special_inode_operations;
1515                 if (raw_inode->i_block[0])
1516                         init_special_inode(inode, inode->i_mode,
1517                            old_decode_dev(le32_to_cpu(raw_inode->i_block[0])));
1518                 else 
1519                         init_special_inode(inode, inode->i_mode,
1520                            new_decode_dev(le32_to_cpu(raw_inode->i_block[1])));
1521         }
1522         brelse (bh);
1523         unlock_new_inode(inode);
1524         return inode;
1525         
1526 bad_inode:
1527         brelse(bh);
1528         iget_failed(inode);
1529         return ERR_PTR(ret);
1530 }
1531 
1532 static int __ext2_write_inode(struct inode *inode, int do_sync)
1533 {
1534         struct ext2_inode_info *ei = EXT2_I(inode);
1535         struct super_block *sb = inode->i_sb;
1536         ino_t ino = inode->i_ino;
1537         uid_t uid = i_uid_read(inode);
1538         gid_t gid = i_gid_read(inode);
1539         struct buffer_head * bh;
1540         struct ext2_inode * raw_inode = ext2_get_inode(sb, ino, &bh);
1541         int n;
1542         int err = 0;
1543 
1544         if (IS_ERR(raw_inode))
1545                 return -EIO;
1546 
1547         /* For fields not not tracking in the in-memory inode,
1548          * initialise them to zero for new inodes. */
1549         if (ei->i_state & EXT2_STATE_NEW)
1550                 memset(raw_inode, 0, EXT2_SB(sb)->s_inode_size);
1551 
1552         raw_inode->i_mode = cpu_to_le16(inode->i_mode);
1553         if (!(test_opt(sb, NO_UID32))) {
1554                 raw_inode->i_uid_low = cpu_to_le16(low_16_bits(uid));
1555                 raw_inode->i_gid_low = cpu_to_le16(low_16_bits(gid));
1556 /*
1557  * Fix up interoperability with old kernels. Otherwise, old inodes get
1558  * re-used with the upper 16 bits of the uid/gid intact
1559  */
1560                 if (!ei->i_dtime) {
1561                         raw_inode->i_uid_high = cpu_to_le16(high_16_bits(uid));
1562                         raw_inode->i_gid_high = cpu_to_le16(high_16_bits(gid));
1563                 } else {
1564                         raw_inode->i_uid_high = 0;
1565                         raw_inode->i_gid_high = 0;
1566                 }
1567         } else {
1568                 raw_inode->i_uid_low = cpu_to_le16(fs_high2lowuid(uid));
1569                 raw_inode->i_gid_low = cpu_to_le16(fs_high2lowgid(gid));
1570                 raw_inode->i_uid_high = 0;
1571                 raw_inode->i_gid_high = 0;
1572         }
1573         raw_inode->i_links_count = cpu_to_le16(inode->i_nlink);
1574         raw_inode->i_size = cpu_to_le32(inode->i_size);
1575         raw_inode->i_atime = cpu_to_le32(inode->i_atime.tv_sec);
1576         raw_inode->i_ctime = cpu_to_le32(inode->i_ctime.tv_sec);
1577         raw_inode->i_mtime = cpu_to_le32(inode->i_mtime.tv_sec);
1578 
1579         raw_inode->i_blocks = cpu_to_le32(inode->i_blocks);
1580         raw_inode->i_dtime = cpu_to_le32(ei->i_dtime);
1581         raw_inode->i_flags = cpu_to_le32(ei->i_flags);
1582         raw_inode->i_faddr = cpu_to_le32(ei->i_faddr);
1583         raw_inode->i_frag = ei->i_frag_no;
1584         raw_inode->i_fsize = ei->i_frag_size;
1585         raw_inode->i_file_acl = cpu_to_le32(ei->i_file_acl);
1586         if (!S_ISREG(inode->i_mode))
1587                 raw_inode->i_dir_acl = cpu_to_le32(ei->i_dir_acl);
1588         else {
1589                 raw_inode->i_size_high = cpu_to_le32(inode->i_size >> 32);
1590                 if (inode->i_size > 0x7fffffffULL) {
1591                         if (!EXT2_HAS_RO_COMPAT_FEATURE(sb,
1592                                         EXT2_FEATURE_RO_COMPAT_LARGE_FILE) ||
1593                             EXT2_SB(sb)->s_es->s_rev_level ==
1594                                         cpu_to_le32(EXT2_GOOD_OLD_REV)) {
1595                                /* If this is the first large file
1596                                 * created, add a flag to the superblock.
1597                                 */
1598                                 spin_lock(&EXT2_SB(sb)->s_lock);
1599                                 ext2_update_dynamic_rev(sb);
1600                                 EXT2_SET_RO_COMPAT_FEATURE(sb,
1601                                         EXT2_FEATURE_RO_COMPAT_LARGE_FILE);
1602                                 spin_unlock(&EXT2_SB(sb)->s_lock);
1603                                 ext2_sync_super(sb, EXT2_SB(sb)->s_es, 1);
1604                         }
1605                 }
1606         }
1607         
1608         raw_inode->i_generation = cpu_to_le32(inode->i_generation);
1609         if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) {
1610                 if (old_valid_dev(inode->i_rdev)) {
1611                         raw_inode->i_block[0] =
1612                                 cpu_to_le32(old_encode_dev(inode->i_rdev));
1613                         raw_inode->i_block[1] = 0;
1614                 } else {
1615                         raw_inode->i_block[0] = 0;
1616                         raw_inode->i_block[1] =
1617                                 cpu_to_le32(new_encode_dev(inode->i_rdev));
1618                         raw_inode->i_block[2] = 0;
1619                 }
1620         } else for (n = 0; n < EXT2_N_BLOCKS; n++)
1621                 raw_inode->i_block[n] = ei->i_data[n];
1622         mark_buffer_dirty(bh);
1623         if (do_sync) {
1624                 sync_dirty_buffer(bh);
1625                 if (buffer_req(bh) && !buffer_uptodate(bh)) {
1626                         printk ("IO error syncing ext2 inode [%s:%08lx]\n",
1627                                 sb->s_id, (unsigned long) ino);
1628                         err = -EIO;
1629                 }
1630         }
1631         ei->i_state &= ~EXT2_STATE_NEW;
1632         brelse (bh);
1633         return err;
1634 }
1635 
1636 int ext2_write_inode(struct inode *inode, struct writeback_control *wbc)
1637 {
1638         return __ext2_write_inode(inode, wbc->sync_mode == WB_SYNC_ALL);
1639 }
1640 
1641 int ext2_getattr(const struct path *path, struct kstat *stat,
1642                 u32 request_mask, unsigned int query_flags)
1643 {
1644         struct inode *inode = d_inode(path->dentry);
1645         struct ext2_inode_info *ei = EXT2_I(inode);
1646         unsigned int flags;
1647 
1648         flags = ei->i_flags & EXT2_FL_USER_VISIBLE;
1649         if (flags & EXT2_APPEND_FL)
1650                 stat->attributes |= STATX_ATTR_APPEND;
1651         if (flags & EXT2_COMPR_FL)
1652                 stat->attributes |= STATX_ATTR_COMPRESSED;
1653         if (flags & EXT2_IMMUTABLE_FL)
1654                 stat->attributes |= STATX_ATTR_IMMUTABLE;
1655         if (flags & EXT2_NODUMP_FL)
1656                 stat->attributes |= STATX_ATTR_NODUMP;
1657         stat->attributes_mask |= (STATX_ATTR_APPEND |
1658                         STATX_ATTR_COMPRESSED |
1659                         STATX_ATTR_ENCRYPTED |
1660                         STATX_ATTR_IMMUTABLE |
1661                         STATX_ATTR_NODUMP);
1662 
1663         generic_fillattr(inode, stat);
1664         return 0;
1665 }
1666 
1667 int ext2_setattr(struct dentry *dentry, struct iattr *iattr)
1668 {
1669         struct inode *inode = d_inode(dentry);
1670         int error;
1671 
1672         error = setattr_prepare(dentry, iattr);
1673         if (error)
1674                 return error;
1675 
1676         if (is_quota_modification(inode, iattr)) {
1677                 error = dquot_initialize(inode);
1678                 if (error)
1679                         return error;
1680         }
1681         if ((iattr->ia_valid & ATTR_UID && !uid_eq(iattr->ia_uid, inode->i_uid)) ||
1682             (iattr->ia_valid & ATTR_GID && !gid_eq(iattr->ia_gid, inode->i_gid))) {
1683                 error = dquot_transfer(inode, iattr);
1684                 if (error)
1685                         return error;
1686         }
1687         if (iattr->ia_valid & ATTR_SIZE && iattr->ia_size != inode->i_size) {
1688                 error = ext2_setsize(inode, iattr->ia_size);
1689                 if (error)
1690                         return error;
1691         }
1692         setattr_copy(inode, iattr);
1693         if (iattr->ia_valid & ATTR_MODE)
1694                 error = posix_acl_chmod(inode, inode->i_mode);
1695         mark_inode_dirty(inode);
1696 
1697         return error;
1698 }
1699 

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