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Linux/fs/ext2/balloc.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  *  linux/fs/ext2/balloc.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  *  Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
 11  *  Big-endian to little-endian byte-swapping/bitmaps by
 12  *        David S. Miller (davem@caip.rutgers.edu), 1995
 13  */
 14 
 15 #include "ext2.h"
 16 #include <linux/quotaops.h>
 17 #include <linux/slab.h>
 18 #include <linux/sched.h>
 19 #include <linux/cred.h>
 20 #include <linux/buffer_head.h>
 21 #include <linux/capability.h>
 22 
 23 /*
 24  * balloc.c contains the blocks allocation and deallocation routines
 25  */
 26 
 27 /*
 28  * The free blocks are managed by bitmaps.  A file system contains several
 29  * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 30  * block for inodes, N blocks for the inode table and data blocks.
 31  *
 32  * The file system contains group descriptors which are located after the
 33  * super block.  Each descriptor contains the number of the bitmap block and
 34  * the free blocks count in the block.  The descriptors are loaded in memory
 35  * when a file system is mounted (see ext2_fill_super).
 36  */
 37 
 38 
 39 #define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
 40 
 41 struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
 42                                              unsigned int block_group,
 43                                              struct buffer_head ** bh)
 44 {
 45         unsigned long group_desc;
 46         unsigned long offset;
 47         struct ext2_group_desc * desc;
 48         struct ext2_sb_info *sbi = EXT2_SB(sb);
 49 
 50         if (block_group >= sbi->s_groups_count) {
 51                 ext2_error (sb, "ext2_get_group_desc",
 52                             "block_group >= groups_count - "
 53                             "block_group = %d, groups_count = %lu",
 54                             block_group, sbi->s_groups_count);
 55 
 56                 return NULL;
 57         }
 58 
 59         group_desc = block_group >> EXT2_DESC_PER_BLOCK_BITS(sb);
 60         offset = block_group & (EXT2_DESC_PER_BLOCK(sb) - 1);
 61         if (!sbi->s_group_desc[group_desc]) {
 62                 ext2_error (sb, "ext2_get_group_desc",
 63                             "Group descriptor not loaded - "
 64                             "block_group = %d, group_desc = %lu, desc = %lu",
 65                              block_group, group_desc, offset);
 66                 return NULL;
 67         }
 68 
 69         desc = (struct ext2_group_desc *) sbi->s_group_desc[group_desc]->b_data;
 70         if (bh)
 71                 *bh = sbi->s_group_desc[group_desc];
 72         return desc + offset;
 73 }
 74 
 75 static int ext2_valid_block_bitmap(struct super_block *sb,
 76                                         struct ext2_group_desc *desc,
 77                                         unsigned int block_group,
 78                                         struct buffer_head *bh)
 79 {
 80         ext2_grpblk_t offset;
 81         ext2_grpblk_t next_zero_bit;
 82         ext2_fsblk_t bitmap_blk;
 83         ext2_fsblk_t group_first_block;
 84 
 85         group_first_block = ext2_group_first_block_no(sb, block_group);
 86 
 87         /* check whether block bitmap block number is set */
 88         bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
 89         offset = bitmap_blk - group_first_block;
 90         if (!ext2_test_bit(offset, bh->b_data))
 91                 /* bad block bitmap */
 92                 goto err_out;
 93 
 94         /* check whether the inode bitmap block number is set */
 95         bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
 96         offset = bitmap_blk - group_first_block;
 97         if (!ext2_test_bit(offset, bh->b_data))
 98                 /* bad block bitmap */
 99                 goto err_out;
100 
101         /* check whether the inode table block number is set */
102         bitmap_blk = le32_to_cpu(desc->bg_inode_table);
103         offset = bitmap_blk - group_first_block;
104         next_zero_bit = ext2_find_next_zero_bit(bh->b_data,
105                                 offset + EXT2_SB(sb)->s_itb_per_group,
106                                 offset);
107         if (next_zero_bit >= offset + EXT2_SB(sb)->s_itb_per_group)
108                 /* good bitmap for inode tables */
109                 return 1;
110 
111 err_out:
112         ext2_error(sb, __func__,
113                         "Invalid block bitmap - "
114                         "block_group = %d, block = %lu",
115                         block_group, bitmap_blk);
116         return 0;
117 }
118 
119 /*
120  * Read the bitmap for a given block_group,and validate the
121  * bits for block/inode/inode tables are set in the bitmaps
122  *
123  * Return buffer_head on success or NULL in case of failure.
124  */
125 static struct buffer_head *
126 read_block_bitmap(struct super_block *sb, unsigned int block_group)
127 {
128         struct ext2_group_desc * desc;
129         struct buffer_head * bh = NULL;
130         ext2_fsblk_t bitmap_blk;
131 
132         desc = ext2_get_group_desc(sb, block_group, NULL);
133         if (!desc)
134                 return NULL;
135         bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
136         bh = sb_getblk(sb, bitmap_blk);
137         if (unlikely(!bh)) {
138                 ext2_error(sb, __func__,
139                             "Cannot read block bitmap - "
140                             "block_group = %d, block_bitmap = %u",
141                             block_group, le32_to_cpu(desc->bg_block_bitmap));
142                 return NULL;
143         }
144         if (likely(bh_uptodate_or_lock(bh)))
145                 return bh;
146 
147         if (bh_submit_read(bh) < 0) {
148                 brelse(bh);
149                 ext2_error(sb, __func__,
150                             "Cannot read block bitmap - "
151                             "block_group = %d, block_bitmap = %u",
152                             block_group, le32_to_cpu(desc->bg_block_bitmap));
153                 return NULL;
154         }
155 
156         ext2_valid_block_bitmap(sb, desc, block_group, bh);
157         /*
158          * file system mounted not to panic on error, continue with corrupt
159          * bitmap
160          */
161         return bh;
162 }
163 
164 static void group_adjust_blocks(struct super_block *sb, int group_no,
165         struct ext2_group_desc *desc, struct buffer_head *bh, int count)
166 {
167         if (count) {
168                 struct ext2_sb_info *sbi = EXT2_SB(sb);
169                 unsigned free_blocks;
170 
171                 spin_lock(sb_bgl_lock(sbi, group_no));
172                 free_blocks = le16_to_cpu(desc->bg_free_blocks_count);
173                 desc->bg_free_blocks_count = cpu_to_le16(free_blocks + count);
174                 spin_unlock(sb_bgl_lock(sbi, group_no));
175                 mark_buffer_dirty(bh);
176         }
177 }
178 
179 /*
180  * The reservation window structure operations
181  * --------------------------------------------
182  * Operations include:
183  * dump, find, add, remove, is_empty, find_next_reservable_window, etc.
184  *
185  * We use a red-black tree to represent per-filesystem reservation
186  * windows.
187  *
188  */
189 
190 /**
191  * __rsv_window_dump() -- Dump the filesystem block allocation reservation map
192  * @rb_root:            root of per-filesystem reservation rb tree
193  * @verbose:            verbose mode
194  * @fn:                 function which wishes to dump the reservation map
195  *
196  * If verbose is turned on, it will print the whole block reservation
197  * windows(start, end). Otherwise, it will only print out the "bad" windows,
198  * those windows that overlap with their immediate neighbors.
199  */
200 #if 1
201 static void __rsv_window_dump(struct rb_root *root, int verbose,
202                               const char *fn)
203 {
204         struct rb_node *n;
205         struct ext2_reserve_window_node *rsv, *prev;
206         int bad;
207 
208 restart:
209         n = rb_first(root);
210         bad = 0;
211         prev = NULL;
212 
213         printk("Block Allocation Reservation Windows Map (%s):\n", fn);
214         while (n) {
215                 rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
216                 if (verbose)
217                         printk("reservation window 0x%p "
218                                 "start: %lu, end: %lu\n",
219                                 rsv, rsv->rsv_start, rsv->rsv_end);
220                 if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) {
221                         printk("Bad reservation %p (start >= end)\n",
222                                rsv);
223                         bad = 1;
224                 }
225                 if (prev && prev->rsv_end >= rsv->rsv_start) {
226                         printk("Bad reservation %p (prev->end >= start)\n",
227                                rsv);
228                         bad = 1;
229                 }
230                 if (bad) {
231                         if (!verbose) {
232                                 printk("Restarting reservation walk in verbose mode\n");
233                                 verbose = 1;
234                                 goto restart;
235                         }
236                 }
237                 n = rb_next(n);
238                 prev = rsv;
239         }
240         printk("Window map complete.\n");
241         BUG_ON(bad);
242 }
243 #define rsv_window_dump(root, verbose) \
244         __rsv_window_dump((root), (verbose), __func__)
245 #else
246 #define rsv_window_dump(root, verbose) do {} while (0)
247 #endif
248 
249 /**
250  * goal_in_my_reservation()
251  * @rsv:                inode's reservation window
252  * @grp_goal:           given goal block relative to the allocation block group
253  * @group:              the current allocation block group
254  * @sb:                 filesystem super block
255  *
256  * Test if the given goal block (group relative) is within the file's
257  * own block reservation window range.
258  *
259  * If the reservation window is outside the goal allocation group, return 0;
260  * grp_goal (given goal block) could be -1, which means no specific
261  * goal block. In this case, always return 1.
262  * If the goal block is within the reservation window, return 1;
263  * otherwise, return 0;
264  */
265 static int
266 goal_in_my_reservation(struct ext2_reserve_window *rsv, ext2_grpblk_t grp_goal,
267                         unsigned int group, struct super_block * sb)
268 {
269         ext2_fsblk_t group_first_block, group_last_block;
270 
271         group_first_block = ext2_group_first_block_no(sb, group);
272         group_last_block = group_first_block + EXT2_BLOCKS_PER_GROUP(sb) - 1;
273 
274         if ((rsv->_rsv_start > group_last_block) ||
275             (rsv->_rsv_end < group_first_block))
276                 return 0;
277         if ((grp_goal >= 0) && ((grp_goal + group_first_block < rsv->_rsv_start)
278                 || (grp_goal + group_first_block > rsv->_rsv_end)))
279                 return 0;
280         return 1;
281 }
282 
283 /**
284  * search_reserve_window()
285  * @rb_root:            root of reservation tree
286  * @goal:               target allocation block
287  *
288  * Find the reserved window which includes the goal, or the previous one
289  * if the goal is not in any window.
290  * Returns NULL if there are no windows or if all windows start after the goal.
291  */
292 static struct ext2_reserve_window_node *
293 search_reserve_window(struct rb_root *root, ext2_fsblk_t goal)
294 {
295         struct rb_node *n = root->rb_node;
296         struct ext2_reserve_window_node *rsv;
297 
298         if (!n)
299                 return NULL;
300 
301         do {
302                 rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
303 
304                 if (goal < rsv->rsv_start)
305                         n = n->rb_left;
306                 else if (goal > rsv->rsv_end)
307                         n = n->rb_right;
308                 else
309                         return rsv;
310         } while (n);
311         /*
312          * We've fallen off the end of the tree: the goal wasn't inside
313          * any particular node.  OK, the previous node must be to one
314          * side of the interval containing the goal.  If it's the RHS,
315          * we need to back up one.
316          */
317         if (rsv->rsv_start > goal) {
318                 n = rb_prev(&rsv->rsv_node);
319                 rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
320         }
321         return rsv;
322 }
323 
324 /*
325  * ext2_rsv_window_add() -- Insert a window to the block reservation rb tree.
326  * @sb:                 super block
327  * @rsv:                reservation window to add
328  *
329  * Must be called with rsv_lock held.
330  */
331 void ext2_rsv_window_add(struct super_block *sb,
332                     struct ext2_reserve_window_node *rsv)
333 {
334         struct rb_root *root = &EXT2_SB(sb)->s_rsv_window_root;
335         struct rb_node *node = &rsv->rsv_node;
336         ext2_fsblk_t start = rsv->rsv_start;
337 
338         struct rb_node ** p = &root->rb_node;
339         struct rb_node * parent = NULL;
340         struct ext2_reserve_window_node *this;
341 
342         while (*p)
343         {
344                 parent = *p;
345                 this = rb_entry(parent, struct ext2_reserve_window_node, rsv_node);
346 
347                 if (start < this->rsv_start)
348                         p = &(*p)->rb_left;
349                 else if (start > this->rsv_end)
350                         p = &(*p)->rb_right;
351                 else {
352                         rsv_window_dump(root, 1);
353                         BUG();
354                 }
355         }
356 
357         rb_link_node(node, parent, p);
358         rb_insert_color(node, root);
359 }
360 
361 /**
362  * rsv_window_remove() -- unlink a window from the reservation rb tree
363  * @sb:                 super block
364  * @rsv:                reservation window to remove
365  *
366  * Mark the block reservation window as not allocated, and unlink it
367  * from the filesystem reservation window rb tree. Must be called with
368  * rsv_lock held.
369  */
370 static void rsv_window_remove(struct super_block *sb,
371                               struct ext2_reserve_window_node *rsv)
372 {
373         rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
374         rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
375         rsv->rsv_alloc_hit = 0;
376         rb_erase(&rsv->rsv_node, &EXT2_SB(sb)->s_rsv_window_root);
377 }
378 
379 /*
380  * rsv_is_empty() -- Check if the reservation window is allocated.
381  * @rsv:                given reservation window to check
382  *
383  * returns 1 if the end block is EXT2_RESERVE_WINDOW_NOT_ALLOCATED.
384  */
385 static inline int rsv_is_empty(struct ext2_reserve_window *rsv)
386 {
387         /* a valid reservation end block could not be 0 */
388         return (rsv->_rsv_end == EXT2_RESERVE_WINDOW_NOT_ALLOCATED);
389 }
390 
391 /**
392  * ext2_init_block_alloc_info()
393  * @inode:              file inode structure
394  *
395  * Allocate and initialize the  reservation window structure, and
396  * link the window to the ext2 inode structure at last
397  *
398  * The reservation window structure is only dynamically allocated
399  * and linked to ext2 inode the first time the open file
400  * needs a new block. So, before every ext2_new_block(s) call, for
401  * regular files, we should check whether the reservation window
402  * structure exists or not. In the latter case, this function is called.
403  * Fail to do so will result in block reservation being turned off for that
404  * open file.
405  *
406  * This function is called from ext2_get_blocks_handle(), also called
407  * when setting the reservation window size through ioctl before the file
408  * is open for write (needs block allocation).
409  *
410  * Needs truncate_mutex protection prior to calling this function.
411  */
412 void ext2_init_block_alloc_info(struct inode *inode)
413 {
414         struct ext2_inode_info *ei = EXT2_I(inode);
415         struct ext2_block_alloc_info *block_i;
416         struct super_block *sb = inode->i_sb;
417 
418         block_i = kmalloc(sizeof(*block_i), GFP_NOFS);
419         if (block_i) {
420                 struct ext2_reserve_window_node *rsv = &block_i->rsv_window_node;
421 
422                 rsv->rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
423                 rsv->rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
424 
425                 /*
426                  * if filesystem is mounted with NORESERVATION, the goal
427                  * reservation window size is set to zero to indicate
428                  * block reservation is off
429                  */
430                 if (!test_opt(sb, RESERVATION))
431                         rsv->rsv_goal_size = 0;
432                 else
433                         rsv->rsv_goal_size = EXT2_DEFAULT_RESERVE_BLOCKS;
434                 rsv->rsv_alloc_hit = 0;
435                 block_i->last_alloc_logical_block = 0;
436                 block_i->last_alloc_physical_block = 0;
437         }
438         ei->i_block_alloc_info = block_i;
439 }
440 
441 /**
442  * ext2_discard_reservation()
443  * @inode:              inode
444  *
445  * Discard(free) block reservation window on last file close, or truncate
446  * or at last iput().
447  *
448  * It is being called in three cases:
449  *      ext2_release_file(): last writer closes the file
450  *      ext2_clear_inode(): last iput(), when nobody links to this file.
451  *      ext2_truncate(): when the block indirect map is about to change.
452  */
453 void ext2_discard_reservation(struct inode *inode)
454 {
455         struct ext2_inode_info *ei = EXT2_I(inode);
456         struct ext2_block_alloc_info *block_i = ei->i_block_alloc_info;
457         struct ext2_reserve_window_node *rsv;
458         spinlock_t *rsv_lock = &EXT2_SB(inode->i_sb)->s_rsv_window_lock;
459 
460         if (!block_i)
461                 return;
462 
463         rsv = &block_i->rsv_window_node;
464         if (!rsv_is_empty(&rsv->rsv_window)) {
465                 spin_lock(rsv_lock);
466                 if (!rsv_is_empty(&rsv->rsv_window))
467                         rsv_window_remove(inode->i_sb, rsv);
468                 spin_unlock(rsv_lock);
469         }
470 }
471 
472 /**
473  * ext2_free_blocks() -- Free given blocks and update quota and i_blocks
474  * @inode:              inode
475  * @block:              start physical block to free
476  * @count:              number of blocks to free
477  */
478 void ext2_free_blocks (struct inode * inode, unsigned long block,
479                        unsigned long count)
480 {
481         struct buffer_head *bitmap_bh = NULL;
482         struct buffer_head * bh2;
483         unsigned long block_group;
484         unsigned long bit;
485         unsigned long i;
486         unsigned long overflow;
487         struct super_block * sb = inode->i_sb;
488         struct ext2_sb_info * sbi = EXT2_SB(sb);
489         struct ext2_group_desc * desc;
490         struct ext2_super_block * es = sbi->s_es;
491         unsigned freed = 0, group_freed;
492 
493         if (block < le32_to_cpu(es->s_first_data_block) ||
494             block + count < block ||
495             block + count > le32_to_cpu(es->s_blocks_count)) {
496                 ext2_error (sb, "ext2_free_blocks",
497                             "Freeing blocks not in datazone - "
498                             "block = %lu, count = %lu", block, count);
499                 goto error_return;
500         }
501 
502         ext2_debug ("freeing block(s) %lu-%lu\n", block, block + count - 1);
503 
504 do_more:
505         overflow = 0;
506         block_group = (block - le32_to_cpu(es->s_first_data_block)) /
507                       EXT2_BLOCKS_PER_GROUP(sb);
508         bit = (block - le32_to_cpu(es->s_first_data_block)) %
509                       EXT2_BLOCKS_PER_GROUP(sb);
510         /*
511          * Check to see if we are freeing blocks across a group
512          * boundary.
513          */
514         if (bit + count > EXT2_BLOCKS_PER_GROUP(sb)) {
515                 overflow = bit + count - EXT2_BLOCKS_PER_GROUP(sb);
516                 count -= overflow;
517         }
518         brelse(bitmap_bh);
519         bitmap_bh = read_block_bitmap(sb, block_group);
520         if (!bitmap_bh)
521                 goto error_return;
522 
523         desc = ext2_get_group_desc (sb, block_group, &bh2);
524         if (!desc)
525                 goto error_return;
526 
527         if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
528             in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
529             in_range (block, le32_to_cpu(desc->bg_inode_table),
530                       sbi->s_itb_per_group) ||
531             in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table),
532                       sbi->s_itb_per_group)) {
533                 ext2_error (sb, "ext2_free_blocks",
534                             "Freeing blocks in system zones - "
535                             "Block = %lu, count = %lu",
536                             block, count);
537                 goto error_return;
538         }
539 
540         for (i = 0, group_freed = 0; i < count; i++) {
541                 if (!ext2_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
542                                                 bit + i, bitmap_bh->b_data)) {
543                         ext2_error(sb, __func__,
544                                 "bit already cleared for block %lu", block + i);
545                 } else {
546                         group_freed++;
547                 }
548         }
549 
550         mark_buffer_dirty(bitmap_bh);
551         if (sb->s_flags & SB_SYNCHRONOUS)
552                 sync_dirty_buffer(bitmap_bh);
553 
554         group_adjust_blocks(sb, block_group, desc, bh2, group_freed);
555         freed += group_freed;
556 
557         if (overflow) {
558                 block += count;
559                 count = overflow;
560                 goto do_more;
561         }
562 error_return:
563         brelse(bitmap_bh);
564         if (freed) {
565                 percpu_counter_add(&sbi->s_freeblocks_counter, freed);
566                 dquot_free_block_nodirty(inode, freed);
567                 mark_inode_dirty(inode);
568         }
569 }
570 
571 /**
572  * bitmap_search_next_usable_block()
573  * @start:              the starting block (group relative) of the search
574  * @bh:                 bufferhead contains the block group bitmap
575  * @maxblocks:          the ending block (group relative) of the reservation
576  *
577  * The bitmap search --- search forward through the actual bitmap on disk until
578  * we find a bit free.
579  */
580 static ext2_grpblk_t
581 bitmap_search_next_usable_block(ext2_grpblk_t start, struct buffer_head *bh,
582                                         ext2_grpblk_t maxblocks)
583 {
584         ext2_grpblk_t next;
585 
586         next = ext2_find_next_zero_bit(bh->b_data, maxblocks, start);
587         if (next >= maxblocks)
588                 return -1;
589         return next;
590 }
591 
592 /**
593  * find_next_usable_block()
594  * @start:              the starting block (group relative) to find next
595  *                      allocatable block in bitmap.
596  * @bh:                 bufferhead contains the block group bitmap
597  * @maxblocks:          the ending block (group relative) for the search
598  *
599  * Find an allocatable block in a bitmap.  We perform the "most
600  * appropriate allocation" algorithm of looking for a free block near
601  * the initial goal; then for a free byte somewhere in the bitmap;
602  * then for any free bit in the bitmap.
603  */
604 static ext2_grpblk_t
605 find_next_usable_block(int start, struct buffer_head *bh, int maxblocks)
606 {
607         ext2_grpblk_t here, next;
608         char *p, *r;
609 
610         if (start > 0) {
611                 /*
612                  * The goal was occupied; search forward for a free 
613                  * block within the next XX blocks.
614                  *
615                  * end_goal is more or less random, but it has to be
616                  * less than EXT2_BLOCKS_PER_GROUP. Aligning up to the
617                  * next 64-bit boundary is simple..
618                  */
619                 ext2_grpblk_t end_goal = (start + 63) & ~63;
620                 if (end_goal > maxblocks)
621                         end_goal = maxblocks;
622                 here = ext2_find_next_zero_bit(bh->b_data, end_goal, start);
623                 if (here < end_goal)
624                         return here;
625                 ext2_debug("Bit not found near goal\n");
626         }
627 
628         here = start;
629         if (here < 0)
630                 here = 0;
631 
632         p = ((char *)bh->b_data) + (here >> 3);
633         r = memscan(p, 0, ((maxblocks + 7) >> 3) - (here >> 3));
634         next = (r - ((char *)bh->b_data)) << 3;
635 
636         if (next < maxblocks && next >= here)
637                 return next;
638 
639         here = bitmap_search_next_usable_block(here, bh, maxblocks);
640         return here;
641 }
642 
643 /**
644  * ext2_try_to_allocate()
645  * @sb:                 superblock
646  * @group:              given allocation block group
647  * @bitmap_bh:          bufferhead holds the block bitmap
648  * @grp_goal:           given target block within the group
649  * @count:              target number of blocks to allocate
650  * @my_rsv:             reservation window
651  *
652  * Attempt to allocate blocks within a give range. Set the range of allocation
653  * first, then find the first free bit(s) from the bitmap (within the range),
654  * and at last, allocate the blocks by claiming the found free bit as allocated.
655  *
656  * To set the range of this allocation:
657  *      if there is a reservation window, only try to allocate block(s)
658  *      from the file's own reservation window;
659  *      Otherwise, the allocation range starts from the give goal block,
660  *      ends at the block group's last block.
661  *
662  * If we failed to allocate the desired block then we may end up crossing to a
663  * new bitmap.
664  */
665 static int
666 ext2_try_to_allocate(struct super_block *sb, int group,
667                         struct buffer_head *bitmap_bh, ext2_grpblk_t grp_goal,
668                         unsigned long *count,
669                         struct ext2_reserve_window *my_rsv)
670 {
671         ext2_fsblk_t group_first_block;
672         ext2_grpblk_t start, end;
673         unsigned long num = 0;
674 
675         /* we do allocation within the reservation window if we have a window */
676         if (my_rsv) {
677                 group_first_block = ext2_group_first_block_no(sb, group);
678                 if (my_rsv->_rsv_start >= group_first_block)
679                         start = my_rsv->_rsv_start - group_first_block;
680                 else
681                         /* reservation window cross group boundary */
682                         start = 0;
683                 end = my_rsv->_rsv_end - group_first_block + 1;
684                 if (end > EXT2_BLOCKS_PER_GROUP(sb))
685                         /* reservation window crosses group boundary */
686                         end = EXT2_BLOCKS_PER_GROUP(sb);
687                 if ((start <= grp_goal) && (grp_goal < end))
688                         start = grp_goal;
689                 else
690                         grp_goal = -1;
691         } else {
692                 if (grp_goal > 0)
693                         start = grp_goal;
694                 else
695                         start = 0;
696                 end = EXT2_BLOCKS_PER_GROUP(sb);
697         }
698 
699         BUG_ON(start > EXT2_BLOCKS_PER_GROUP(sb));
700 
701 repeat:
702         if (grp_goal < 0) {
703                 grp_goal = find_next_usable_block(start, bitmap_bh, end);
704                 if (grp_goal < 0)
705                         goto fail_access;
706                 if (!my_rsv) {
707                         int i;
708 
709                         for (i = 0; i < 7 && grp_goal > start &&
710                                         !ext2_test_bit(grp_goal - 1,
711                                                         bitmap_bh->b_data);
712                                         i++, grp_goal--)
713                                 ;
714                 }
715         }
716         start = grp_goal;
717 
718         if (ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group), grp_goal,
719                                                         bitmap_bh->b_data)) {
720                 /*
721                  * The block was allocated by another thread, or it was
722                  * allocated and then freed by another thread
723                  */
724                 start++;
725                 grp_goal++;
726                 if (start >= end)
727                         goto fail_access;
728                 goto repeat;
729         }
730         num++;
731         grp_goal++;
732         while (num < *count && grp_goal < end
733                 && !ext2_set_bit_atomic(sb_bgl_lock(EXT2_SB(sb), group),
734                                         grp_goal, bitmap_bh->b_data)) {
735                 num++;
736                 grp_goal++;
737         }
738         *count = num;
739         return grp_goal - num;
740 fail_access:
741         *count = num;
742         return -1;
743 }
744 
745 /**
746  *      find_next_reservable_window():
747  *              find a reservable space within the given range.
748  *              It does not allocate the reservation window for now:
749  *              alloc_new_reservation() will do the work later.
750  *
751  *      @search_head: the head of the searching list;
752  *              This is not necessarily the list head of the whole filesystem
753  *
754  *              We have both head and start_block to assist the search
755  *              for the reservable space. The list starts from head,
756  *              but we will shift to the place where start_block is,
757  *              then start from there, when looking for a reservable space.
758  *
759  *      @size: the target new reservation window size
760  *
761  *      @group_first_block: the first block we consider to start
762  *                      the real search from
763  *
764  *      @last_block:
765  *              the maximum block number that our goal reservable space
766  *              could start from. This is normally the last block in this
767  *              group. The search will end when we found the start of next
768  *              possible reservable space is out of this boundary.
769  *              This could handle the cross boundary reservation window
770  *              request.
771  *
772  *      basically we search from the given range, rather than the whole
773  *      reservation double linked list, (start_block, last_block)
774  *      to find a free region that is of my size and has not
775  *      been reserved.
776  *
777  */
778 static int find_next_reservable_window(
779                                 struct ext2_reserve_window_node *search_head,
780                                 struct ext2_reserve_window_node *my_rsv,
781                                 struct super_block * sb,
782                                 ext2_fsblk_t start_block,
783                                 ext2_fsblk_t last_block)
784 {
785         struct rb_node *next;
786         struct ext2_reserve_window_node *rsv, *prev;
787         ext2_fsblk_t cur;
788         int size = my_rsv->rsv_goal_size;
789 
790         /* TODO: make the start of the reservation window byte-aligned */
791         /* cur = *start_block & ~7;*/
792         cur = start_block;
793         rsv = search_head;
794         if (!rsv)
795                 return -1;
796 
797         while (1) {
798                 if (cur <= rsv->rsv_end)
799                         cur = rsv->rsv_end + 1;
800 
801                 /* TODO?
802                  * in the case we could not find a reservable space
803                  * that is what is expected, during the re-search, we could
804                  * remember what's the largest reservable space we could have
805                  * and return that one.
806                  *
807                  * For now it will fail if we could not find the reservable
808                  * space with expected-size (or more)...
809                  */
810                 if (cur > last_block)
811                         return -1;              /* fail */
812 
813                 prev = rsv;
814                 next = rb_next(&rsv->rsv_node);
815                 rsv = rb_entry(next,struct ext2_reserve_window_node,rsv_node);
816 
817                 /*
818                  * Reached the last reservation, we can just append to the
819                  * previous one.
820                  */
821                 if (!next)
822                         break;
823 
824                 if (cur + size <= rsv->rsv_start) {
825                         /*
826                          * Found a reserveable space big enough.  We could
827                          * have a reservation across the group boundary here
828                          */
829                         break;
830                 }
831         }
832         /*
833          * we come here either :
834          * when we reach the end of the whole list,
835          * and there is empty reservable space after last entry in the list.
836          * append it to the end of the list.
837          *
838          * or we found one reservable space in the middle of the list,
839          * return the reservation window that we could append to.
840          * succeed.
841          */
842 
843         if ((prev != my_rsv) && (!rsv_is_empty(&my_rsv->rsv_window)))
844                 rsv_window_remove(sb, my_rsv);
845 
846         /*
847          * Let's book the whole available window for now.  We will check the
848          * disk bitmap later and then, if there are free blocks then we adjust
849          * the window size if it's larger than requested.
850          * Otherwise, we will remove this node from the tree next time
851          * call find_next_reservable_window.
852          */
853         my_rsv->rsv_start = cur;
854         my_rsv->rsv_end = cur + size - 1;
855         my_rsv->rsv_alloc_hit = 0;
856 
857         if (prev != my_rsv)
858                 ext2_rsv_window_add(sb, my_rsv);
859 
860         return 0;
861 }
862 
863 /**
864  *      alloc_new_reservation()--allocate a new reservation window
865  *
866  *              To make a new reservation, we search part of the filesystem
867  *              reservation list (the list that inside the group). We try to
868  *              allocate a new reservation window near the allocation goal,
869  *              or the beginning of the group, if there is no goal.
870  *
871  *              We first find a reservable space after the goal, then from
872  *              there, we check the bitmap for the first free block after
873  *              it. If there is no free block until the end of group, then the
874  *              whole group is full, we failed. Otherwise, check if the free
875  *              block is inside the expected reservable space, if so, we
876  *              succeed.
877  *              If the first free block is outside the reservable space, then
878  *              start from the first free block, we search for next available
879  *              space, and go on.
880  *
881  *      on succeed, a new reservation will be found and inserted into the list
882  *      It contains at least one free block, and it does not overlap with other
883  *      reservation windows.
884  *
885  *      failed: we failed to find a reservation window in this group
886  *
887  *      @rsv: the reservation
888  *
889  *      @grp_goal: The goal (group-relative).  It is where the search for a
890  *              free reservable space should start from.
891  *              if we have a goal(goal >0 ), then start from there,
892  *              no goal(goal = -1), we start from the first block
893  *              of the group.
894  *
895  *      @sb: the super block
896  *      @group: the group we are trying to allocate in
897  *      @bitmap_bh: the block group block bitmap
898  *
899  */
900 static int alloc_new_reservation(struct ext2_reserve_window_node *my_rsv,
901                 ext2_grpblk_t grp_goal, struct super_block *sb,
902                 unsigned int group, struct buffer_head *bitmap_bh)
903 {
904         struct ext2_reserve_window_node *search_head;
905         ext2_fsblk_t group_first_block, group_end_block, start_block;
906         ext2_grpblk_t first_free_block;
907         struct rb_root *fs_rsv_root = &EXT2_SB(sb)->s_rsv_window_root;
908         unsigned long size;
909         int ret;
910         spinlock_t *rsv_lock = &EXT2_SB(sb)->s_rsv_window_lock;
911 
912         group_first_block = ext2_group_first_block_no(sb, group);
913         group_end_block = group_first_block + (EXT2_BLOCKS_PER_GROUP(sb) - 1);
914 
915         if (grp_goal < 0)
916                 start_block = group_first_block;
917         else
918                 start_block = grp_goal + group_first_block;
919 
920         size = my_rsv->rsv_goal_size;
921 
922         if (!rsv_is_empty(&my_rsv->rsv_window)) {
923                 /*
924                  * if the old reservation is cross group boundary
925                  * and if the goal is inside the old reservation window,
926                  * we will come here when we just failed to allocate from
927                  * the first part of the window. We still have another part
928                  * that belongs to the next group. In this case, there is no
929                  * point to discard our window and try to allocate a new one
930                  * in this group(which will fail). we should
931                  * keep the reservation window, just simply move on.
932                  *
933                  * Maybe we could shift the start block of the reservation
934                  * window to the first block of next group.
935                  */
936 
937                 if ((my_rsv->rsv_start <= group_end_block) &&
938                                 (my_rsv->rsv_end > group_end_block) &&
939                                 (start_block >= my_rsv->rsv_start))
940                         return -1;
941 
942                 if ((my_rsv->rsv_alloc_hit >
943                      (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) {
944                         /*
945                          * if the previously allocation hit ratio is
946                          * greater than 1/2, then we double the size of
947                          * the reservation window the next time,
948                          * otherwise we keep the same size window
949                          */
950                         size = size * 2;
951                         if (size > EXT2_MAX_RESERVE_BLOCKS)
952                                 size = EXT2_MAX_RESERVE_BLOCKS;
953                         my_rsv->rsv_goal_size= size;
954                 }
955         }
956 
957         spin_lock(rsv_lock);
958         /*
959          * shift the search start to the window near the goal block
960          */
961         search_head = search_reserve_window(fs_rsv_root, start_block);
962 
963         /*
964          * find_next_reservable_window() simply finds a reservable window
965          * inside the given range(start_block, group_end_block).
966          *
967          * To make sure the reservation window has a free bit inside it, we
968          * need to check the bitmap after we found a reservable window.
969          */
970 retry:
971         ret = find_next_reservable_window(search_head, my_rsv, sb,
972                                                 start_block, group_end_block);
973 
974         if (ret == -1) {
975                 if (!rsv_is_empty(&my_rsv->rsv_window))
976                         rsv_window_remove(sb, my_rsv);
977                 spin_unlock(rsv_lock);
978                 return -1;
979         }
980 
981         /*
982          * On success, find_next_reservable_window() returns the
983          * reservation window where there is a reservable space after it.
984          * Before we reserve this reservable space, we need
985          * to make sure there is at least a free block inside this region.
986          *
987          * Search the first free bit on the block bitmap.  Search starts from
988          * the start block of the reservable space we just found.
989          */
990         spin_unlock(rsv_lock);
991         first_free_block = bitmap_search_next_usable_block(
992                         my_rsv->rsv_start - group_first_block,
993                         bitmap_bh, group_end_block - group_first_block + 1);
994 
995         if (first_free_block < 0) {
996                 /*
997                  * no free block left on the bitmap, no point
998                  * to reserve the space. return failed.
999                  */
1000                 spin_lock(rsv_lock);
1001                 if (!rsv_is_empty(&my_rsv->rsv_window))
1002                         rsv_window_remove(sb, my_rsv);
1003                 spin_unlock(rsv_lock);
1004                 return -1;              /* failed */
1005         }
1006 
1007         start_block = first_free_block + group_first_block;
1008         /*
1009          * check if the first free block is within the
1010          * free space we just reserved
1011          */
1012         if (start_block >= my_rsv->rsv_start && start_block <= my_rsv->rsv_end)
1013                 return 0;               /* success */
1014         /*
1015          * if the first free bit we found is out of the reservable space
1016          * continue search for next reservable space,
1017          * start from where the free block is,
1018          * we also shift the list head to where we stopped last time
1019          */
1020         search_head = my_rsv;
1021         spin_lock(rsv_lock);
1022         goto retry;
1023 }
1024 
1025 /**
1026  * try_to_extend_reservation()
1027  * @my_rsv:             given reservation window
1028  * @sb:                 super block
1029  * @size:               the delta to extend
1030  *
1031  * Attempt to expand the reservation window large enough to have
1032  * required number of free blocks
1033  *
1034  * Since ext2_try_to_allocate() will always allocate blocks within
1035  * the reservation window range, if the window size is too small,
1036  * multiple blocks allocation has to stop at the end of the reservation
1037  * window. To make this more efficient, given the total number of
1038  * blocks needed and the current size of the window, we try to
1039  * expand the reservation window size if necessary on a best-effort
1040  * basis before ext2_new_blocks() tries to allocate blocks.
1041  */
1042 static void try_to_extend_reservation(struct ext2_reserve_window_node *my_rsv,
1043                         struct super_block *sb, int size)
1044 {
1045         struct ext2_reserve_window_node *next_rsv;
1046         struct rb_node *next;
1047         spinlock_t *rsv_lock = &EXT2_SB(sb)->s_rsv_window_lock;
1048 
1049         if (!spin_trylock(rsv_lock))
1050                 return;
1051 
1052         next = rb_next(&my_rsv->rsv_node);
1053 
1054         if (!next)
1055                 my_rsv->rsv_end += size;
1056         else {
1057                 next_rsv = rb_entry(next, struct ext2_reserve_window_node, rsv_node);
1058 
1059                 if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size)
1060                         my_rsv->rsv_end += size;
1061                 else
1062                         my_rsv->rsv_end = next_rsv->rsv_start - 1;
1063         }
1064         spin_unlock(rsv_lock);
1065 }
1066 
1067 /**
1068  * ext2_try_to_allocate_with_rsv()
1069  * @sb:                 superblock
1070  * @group:              given allocation block group
1071  * @bitmap_bh:          bufferhead holds the block bitmap
1072  * @grp_goal:           given target block within the group
1073  * @count:              target number of blocks to allocate
1074  * @my_rsv:             reservation window
1075  *
1076  * This is the main function used to allocate a new block and its reservation
1077  * window.
1078  *
1079  * Each time when a new block allocation is need, first try to allocate from
1080  * its own reservation.  If it does not have a reservation window, instead of
1081  * looking for a free bit on bitmap first, then look up the reservation list to
1082  * see if it is inside somebody else's reservation window, we try to allocate a
1083  * reservation window for it starting from the goal first. Then do the block
1084  * allocation within the reservation window.
1085  *
1086  * This will avoid keeping on searching the reservation list again and
1087  * again when somebody is looking for a free block (without
1088  * reservation), and there are lots of free blocks, but they are all
1089  * being reserved.
1090  *
1091  * We use a red-black tree for the per-filesystem reservation list.
1092  */
1093 static ext2_grpblk_t
1094 ext2_try_to_allocate_with_rsv(struct super_block *sb, unsigned int group,
1095                         struct buffer_head *bitmap_bh, ext2_grpblk_t grp_goal,
1096                         struct ext2_reserve_window_node * my_rsv,
1097                         unsigned long *count)
1098 {
1099         ext2_fsblk_t group_first_block, group_last_block;
1100         ext2_grpblk_t ret = 0;
1101         unsigned long num = *count;
1102 
1103         /*
1104          * we don't deal with reservation when
1105          * filesystem is mounted without reservation
1106          * or the file is not a regular file
1107          * or last attempt to allocate a block with reservation turned on failed
1108          */
1109         if (my_rsv == NULL) {
1110                 return ext2_try_to_allocate(sb, group, bitmap_bh,
1111                                                 grp_goal, count, NULL);
1112         }
1113         /*
1114          * grp_goal is a group relative block number (if there is a goal)
1115          * 0 <= grp_goal < EXT2_BLOCKS_PER_GROUP(sb)
1116          * first block is a filesystem wide block number
1117          * first block is the block number of the first block in this group
1118          */
1119         group_first_block = ext2_group_first_block_no(sb, group);
1120         group_last_block = group_first_block + (EXT2_BLOCKS_PER_GROUP(sb) - 1);
1121 
1122         /*
1123          * Basically we will allocate a new block from inode's reservation
1124          * window.
1125          *
1126          * We need to allocate a new reservation window, if:
1127          * a) inode does not have a reservation window; or
1128          * b) last attempt to allocate a block from existing reservation
1129          *    failed; or
1130          * c) we come here with a goal and with a reservation window
1131          *
1132          * We do not need to allocate a new reservation window if we come here
1133          * at the beginning with a goal and the goal is inside the window, or
1134          * we don't have a goal but already have a reservation window.
1135          * then we could go to allocate from the reservation window directly.
1136          */
1137         while (1) {
1138                 if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
1139                         !goal_in_my_reservation(&my_rsv->rsv_window,
1140                                                 grp_goal, group, sb)) {
1141                         if (my_rsv->rsv_goal_size < *count)
1142                                 my_rsv->rsv_goal_size = *count;
1143                         ret = alloc_new_reservation(my_rsv, grp_goal, sb,
1144                                                         group, bitmap_bh);
1145                         if (ret < 0)
1146                                 break;                  /* failed */
1147 
1148                         if (!goal_in_my_reservation(&my_rsv->rsv_window,
1149                                                         grp_goal, group, sb))
1150                                 grp_goal = -1;
1151                 } else if (grp_goal >= 0) {
1152                         int curr = my_rsv->rsv_end -
1153                                         (grp_goal + group_first_block) + 1;
1154 
1155                         if (curr < *count)
1156                                 try_to_extend_reservation(my_rsv, sb,
1157                                                         *count - curr);
1158                 }
1159 
1160                 if ((my_rsv->rsv_start > group_last_block) ||
1161                                 (my_rsv->rsv_end < group_first_block)) {
1162                         rsv_window_dump(&EXT2_SB(sb)->s_rsv_window_root, 1);
1163                         BUG();
1164                 }
1165                 ret = ext2_try_to_allocate(sb, group, bitmap_bh, grp_goal,
1166                                            &num, &my_rsv->rsv_window);
1167                 if (ret >= 0) {
1168                         my_rsv->rsv_alloc_hit += num;
1169                         *count = num;
1170                         break;                          /* succeed */
1171                 }
1172                 num = *count;
1173         }
1174         return ret;
1175 }
1176 
1177 /**
1178  * ext2_has_free_blocks()
1179  * @sbi:                in-core super block structure.
1180  *
1181  * Check if filesystem has at least 1 free block available for allocation.
1182  */
1183 static int ext2_has_free_blocks(struct ext2_sb_info *sbi)
1184 {
1185         ext2_fsblk_t free_blocks, root_blocks;
1186 
1187         free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
1188         root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
1189         if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
1190                 !uid_eq(sbi->s_resuid, current_fsuid()) &&
1191                 (gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) ||
1192                  !in_group_p (sbi->s_resgid))) {
1193                 return 0;
1194         }
1195         return 1;
1196 }
1197 
1198 /*
1199  * Returns 1 if the passed-in block region is valid; 0 if some part overlaps
1200  * with filesystem metadata blocks.
1201  */
1202 int ext2_data_block_valid(struct ext2_sb_info *sbi, ext2_fsblk_t start_blk,
1203                           unsigned int count)
1204 {
1205         if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
1206             (start_blk + count < start_blk) ||
1207             (start_blk > le32_to_cpu(sbi->s_es->s_blocks_count)))
1208                 return 0;
1209 
1210         /* Ensure we do not step over superblock */
1211         if ((start_blk <= sbi->s_sb_block) &&
1212             (start_blk + count >= sbi->s_sb_block))
1213                 return 0;
1214 
1215         return 1;
1216 }
1217 
1218 /*
1219  * ext2_new_blocks() -- core block(s) allocation function
1220  * @inode:              file inode
1221  * @goal:               given target block(filesystem wide)
1222  * @count:              target number of blocks to allocate
1223  * @errp:               error code
1224  *
1225  * ext2_new_blocks uses a goal block to assist allocation.  If the goal is
1226  * free, or there is a free block within 32 blocks of the goal, that block
1227  * is allocated.  Otherwise a forward search is made for a free block; within 
1228  * each block group the search first looks for an entire free byte in the block
1229  * bitmap, and then for any free bit if that fails.
1230  * This function also updates quota and i_blocks field.
1231  */
1232 ext2_fsblk_t ext2_new_blocks(struct inode *inode, ext2_fsblk_t goal,
1233                     unsigned long *count, int *errp)
1234 {
1235         struct buffer_head *bitmap_bh = NULL;
1236         struct buffer_head *gdp_bh;
1237         int group_no;
1238         int goal_group;
1239         ext2_grpblk_t grp_target_blk;   /* blockgroup relative goal block */
1240         ext2_grpblk_t grp_alloc_blk;    /* blockgroup-relative allocated block*/
1241         ext2_fsblk_t ret_block;         /* filesyetem-wide allocated block */
1242         int bgi;                        /* blockgroup iteration index */
1243         int performed_allocation = 0;
1244         ext2_grpblk_t free_blocks;      /* number of free blocks in a group */
1245         struct super_block *sb;
1246         struct ext2_group_desc *gdp;
1247         struct ext2_super_block *es;
1248         struct ext2_sb_info *sbi;
1249         struct ext2_reserve_window_node *my_rsv = NULL;
1250         struct ext2_block_alloc_info *block_i;
1251         unsigned short windowsz = 0;
1252         unsigned long ngroups;
1253         unsigned long num = *count;
1254         int ret;
1255 
1256         *errp = -ENOSPC;
1257         sb = inode->i_sb;
1258 
1259         /*
1260          * Check quota for allocation of this block.
1261          */
1262         ret = dquot_alloc_block(inode, num);
1263         if (ret) {
1264                 *errp = ret;
1265                 return 0;
1266         }
1267 
1268         sbi = EXT2_SB(sb);
1269         es = EXT2_SB(sb)->s_es;
1270         ext2_debug("goal=%lu.\n", goal);
1271         /*
1272          * Allocate a block from reservation only when
1273          * filesystem is mounted with reservation(default,-o reservation), and
1274          * it's a regular file, and
1275          * the desired window size is greater than 0 (One could use ioctl
1276          * command EXT2_IOC_SETRSVSZ to set the window size to 0 to turn off
1277          * reservation on that particular file)
1278          */
1279         block_i = EXT2_I(inode)->i_block_alloc_info;
1280         if (block_i) {
1281                 windowsz = block_i->rsv_window_node.rsv_goal_size;
1282                 if (windowsz > 0)
1283                         my_rsv = &block_i->rsv_window_node;
1284         }
1285 
1286         if (!ext2_has_free_blocks(sbi)) {
1287                 *errp = -ENOSPC;
1288                 goto out;
1289         }
1290 
1291         /*
1292          * First, test whether the goal block is free.
1293          */
1294         if (goal < le32_to_cpu(es->s_first_data_block) ||
1295             goal >= le32_to_cpu(es->s_blocks_count))
1296                 goal = le32_to_cpu(es->s_first_data_block);
1297         group_no = (goal - le32_to_cpu(es->s_first_data_block)) /
1298                         EXT2_BLOCKS_PER_GROUP(sb);
1299         goal_group = group_no;
1300 retry_alloc:
1301         gdp = ext2_get_group_desc(sb, group_no, &gdp_bh);
1302         if (!gdp)
1303                 goto io_error;
1304 
1305         free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
1306         /*
1307          * if there is not enough free blocks to make a new resevation
1308          * turn off reservation for this allocation
1309          */
1310         if (my_rsv && (free_blocks < windowsz)
1311                 && (free_blocks > 0)
1312                 && (rsv_is_empty(&my_rsv->rsv_window)))
1313                 my_rsv = NULL;
1314 
1315         if (free_blocks > 0) {
1316                 grp_target_blk = ((goal - le32_to_cpu(es->s_first_data_block)) %
1317                                 EXT2_BLOCKS_PER_GROUP(sb));
1318                 bitmap_bh = read_block_bitmap(sb, group_no);
1319                 if (!bitmap_bh)
1320                         goto io_error;
1321                 grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
1322                                         bitmap_bh, grp_target_blk,
1323                                         my_rsv, &num);
1324                 if (grp_alloc_blk >= 0)
1325                         goto allocated;
1326         }
1327 
1328         ngroups = EXT2_SB(sb)->s_groups_count;
1329         smp_rmb();
1330 
1331         /*
1332          * Now search the rest of the groups.  We assume that
1333          * group_no and gdp correctly point to the last group visited.
1334          */
1335         for (bgi = 0; bgi < ngroups; bgi++) {
1336                 group_no++;
1337                 if (group_no >= ngroups)
1338                         group_no = 0;
1339                 gdp = ext2_get_group_desc(sb, group_no, &gdp_bh);
1340                 if (!gdp)
1341                         goto io_error;
1342 
1343                 free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
1344                 /*
1345                  * skip this group (and avoid loading bitmap) if there
1346                  * are no free blocks
1347                  */
1348                 if (!free_blocks)
1349                         continue;
1350                 /*
1351                  * skip this group if the number of
1352                  * free blocks is less than half of the reservation
1353                  * window size.
1354                  */
1355                 if (my_rsv && (free_blocks <= (windowsz/2)))
1356                         continue;
1357 
1358                 brelse(bitmap_bh);
1359                 bitmap_bh = read_block_bitmap(sb, group_no);
1360                 if (!bitmap_bh)
1361                         goto io_error;
1362                 /*
1363                  * try to allocate block(s) from this group, without a goal(-1).
1364                  */
1365                 grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
1366                                         bitmap_bh, -1, my_rsv, &num);
1367                 if (grp_alloc_blk >= 0)
1368                         goto allocated;
1369         }
1370         /*
1371          * We may end up a bogus earlier ENOSPC error due to
1372          * filesystem is "full" of reservations, but
1373          * there maybe indeed free blocks available on disk
1374          * In this case, we just forget about the reservations
1375          * just do block allocation as without reservations.
1376          */
1377         if (my_rsv) {
1378                 my_rsv = NULL;
1379                 windowsz = 0;
1380                 group_no = goal_group;
1381                 goto retry_alloc;
1382         }
1383         /* No space left on the device */
1384         *errp = -ENOSPC;
1385         goto out;
1386 
1387 allocated:
1388 
1389         ext2_debug("using block group %d(%d)\n",
1390                         group_no, gdp->bg_free_blocks_count);
1391 
1392         ret_block = grp_alloc_blk + ext2_group_first_block_no(sb, group_no);
1393 
1394         if (in_range(le32_to_cpu(gdp->bg_block_bitmap), ret_block, num) ||
1395             in_range(le32_to_cpu(gdp->bg_inode_bitmap), ret_block, num) ||
1396             in_range(ret_block, le32_to_cpu(gdp->bg_inode_table),
1397                       EXT2_SB(sb)->s_itb_per_group) ||
1398             in_range(ret_block + num - 1, le32_to_cpu(gdp->bg_inode_table),
1399                       EXT2_SB(sb)->s_itb_per_group)) {
1400                 ext2_error(sb, "ext2_new_blocks",
1401                             "Allocating block in system zone - "
1402                             "blocks from "E2FSBLK", length %lu",
1403                             ret_block, num);
1404                 /*
1405                  * ext2_try_to_allocate marked the blocks we allocated as in
1406                  * use.  So we may want to selectively mark some of the blocks
1407                  * as free
1408                  */
1409                 goto retry_alloc;
1410         }
1411 
1412         performed_allocation = 1;
1413 
1414         if (ret_block + num - 1 >= le32_to_cpu(es->s_blocks_count)) {
1415                 ext2_error(sb, "ext2_new_blocks",
1416                             "block("E2FSBLK") >= blocks count(%d) - "
1417                             "block_group = %d, es == %p ", ret_block,
1418                         le32_to_cpu(es->s_blocks_count), group_no, es);
1419                 goto out;
1420         }
1421 
1422         group_adjust_blocks(sb, group_no, gdp, gdp_bh, -num);
1423         percpu_counter_sub(&sbi->s_freeblocks_counter, num);
1424 
1425         mark_buffer_dirty(bitmap_bh);
1426         if (sb->s_flags & SB_SYNCHRONOUS)
1427                 sync_dirty_buffer(bitmap_bh);
1428 
1429         *errp = 0;
1430         brelse(bitmap_bh);
1431         if (num < *count) {
1432                 dquot_free_block_nodirty(inode, *count-num);
1433                 mark_inode_dirty(inode);
1434                 *count = num;
1435         }
1436         return ret_block;
1437 
1438 io_error:
1439         *errp = -EIO;
1440 out:
1441         /*
1442          * Undo the block allocation
1443          */
1444         if (!performed_allocation) {
1445                 dquot_free_block_nodirty(inode, *count);
1446                 mark_inode_dirty(inode);
1447         }
1448         brelse(bitmap_bh);
1449         return 0;
1450 }
1451 
1452 ext2_fsblk_t ext2_new_block(struct inode *inode, unsigned long goal, int *errp)
1453 {
1454         unsigned long count = 1;
1455 
1456         return ext2_new_blocks(inode, goal, &count, errp);
1457 }
1458 
1459 #ifdef EXT2FS_DEBUG
1460 
1461 unsigned long ext2_count_free(struct buffer_head *map, unsigned int numchars)
1462 {
1463         return numchars * BITS_PER_BYTE - memweight(map->b_data, numchars);
1464 }
1465 
1466 #endif  /*  EXT2FS_DEBUG  */
1467 
1468 unsigned long ext2_count_free_blocks (struct super_block * sb)
1469 {
1470         struct ext2_group_desc * desc;
1471         unsigned long desc_count = 0;
1472         int i;
1473 #ifdef EXT2FS_DEBUG
1474         unsigned long bitmap_count, x;
1475         struct ext2_super_block *es;
1476 
1477         es = EXT2_SB(sb)->s_es;
1478         desc_count = 0;
1479         bitmap_count = 0;
1480         desc = NULL;
1481         for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
1482                 struct buffer_head *bitmap_bh;
1483                 desc = ext2_get_group_desc (sb, i, NULL);
1484                 if (!desc)
1485                         continue;
1486                 desc_count += le16_to_cpu(desc->bg_free_blocks_count);
1487                 bitmap_bh = read_block_bitmap(sb, i);
1488                 if (!bitmap_bh)
1489                         continue;
1490                 
1491                 x = ext2_count_free(bitmap_bh, sb->s_blocksize);
1492                 printk ("group %d: stored = %d, counted = %lu\n",
1493                         i, le16_to_cpu(desc->bg_free_blocks_count), x);
1494                 bitmap_count += x;
1495                 brelse(bitmap_bh);
1496         }
1497         printk("ext2_count_free_blocks: stored = %lu, computed = %lu, %lu\n",
1498                 (long)le32_to_cpu(es->s_free_blocks_count),
1499                 desc_count, bitmap_count);
1500         return bitmap_count;
1501 #else
1502         for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++) {
1503                 desc = ext2_get_group_desc (sb, i, NULL);
1504                 if (!desc)
1505                         continue;
1506                 desc_count += le16_to_cpu(desc->bg_free_blocks_count);
1507         }
1508         return desc_count;
1509 #endif
1510 }
1511 
1512 static inline int test_root(int a, int b)
1513 {
1514         int num = b;
1515 
1516         while (a > num)
1517                 num *= b;
1518         return num == a;
1519 }
1520 
1521 static int ext2_group_sparse(int group)
1522 {
1523         if (group <= 1)
1524                 return 1;
1525         return (test_root(group, 3) || test_root(group, 5) ||
1526                 test_root(group, 7));
1527 }
1528 
1529 /**
1530  *      ext2_bg_has_super - number of blocks used by the superblock in group
1531  *      @sb: superblock for filesystem
1532  *      @group: group number to check
1533  *
1534  *      Return the number of blocks used by the superblock (primary or backup)
1535  *      in this group.  Currently this will be only 0 or 1.
1536  */
1537 int ext2_bg_has_super(struct super_block *sb, int group)
1538 {
1539         if (EXT2_HAS_RO_COMPAT_FEATURE(sb,EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
1540             !ext2_group_sparse(group))
1541                 return 0;
1542         return 1;
1543 }
1544 
1545 /**
1546  *      ext2_bg_num_gdb - number of blocks used by the group table in group
1547  *      @sb: superblock for filesystem
1548  *      @group: group number to check
1549  *
1550  *      Return the number of blocks used by the group descriptor table
1551  *      (primary or backup) in this group.  In the future there may be a
1552  *      different number of descriptor blocks in each group.
1553  */
1554 unsigned long ext2_bg_num_gdb(struct super_block *sb, int group)
1555 {
1556         return ext2_bg_has_super(sb, group) ? EXT2_SB(sb)->s_gdb_count : 0;
1557 }
1558 
1559 

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