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omfs: add bitmap routines
Add block allocation and block bitmap management routines for OMFS. Signed-off-by: Bob Copeland <me@bobcopeland.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Bob Copeland
Linus Torvalds
parent
8f09e98768
commit
36cc410a67
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@ -0,0 +1,192 @@
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#include <linux/kernel.h>
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#include <linux/fs.h>
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#include <linux/buffer_head.h>
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#include <asm/div64.h>
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#include "omfs.h"
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unsigned long omfs_count_free(struct super_block *sb)
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{
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unsigned int i;
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unsigned long sum = 0;
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struct omfs_sb_info *sbi = OMFS_SB(sb);
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int nbits = sb->s_blocksize * 8;
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for (i = 0; i < sbi->s_imap_size; i++)
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sum += nbits - bitmap_weight(sbi->s_imap[i], nbits);
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return sum;
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}
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/*
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* Counts the run of zero bits starting at bit up to max.
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* It handles the case where a run might spill over a buffer.
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* Called with bitmap lock.
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*/
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static int count_run(unsigned long **addr, int nbits,
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int addrlen, int bit, int max)
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{
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int count = 0;
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int x;
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for (; addrlen > 0; addrlen--, addr++) {
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x = find_next_bit(*addr, nbits, bit);
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count += x - bit;
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if (x < nbits || count > max)
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return min(count, max);
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bit = 0;
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}
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return min(count, max);
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}
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/*
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* Sets or clears the run of count bits starting with bit.
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* Called with bitmap lock.
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*/
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static int set_run(struct super_block *sb, int map,
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int nbits, int bit, int count, int set)
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{
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int i;
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int err;
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struct buffer_head *bh;
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struct omfs_sb_info *sbi = OMFS_SB(sb);
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err = -ENOMEM;
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bh = sb_bread(sb, clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
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if (!bh)
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goto out;
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for (i = 0; i < count; i++, bit++) {
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if (bit >= nbits) {
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bit = 0;
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map++;
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mark_buffer_dirty(bh);
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brelse(bh);
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bh = sb_bread(sb,
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clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
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if (!bh)
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goto out;
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}
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if (set) {
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set_bit(bit, sbi->s_imap[map]);
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set_bit(bit, (long *) bh->b_data);
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} else {
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clear_bit(bit, sbi->s_imap[map]);
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clear_bit(bit, (long *) bh->b_data);
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}
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}
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mark_buffer_dirty(bh);
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brelse(bh);
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err = 0;
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out:
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return err;
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}
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/*
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* Tries to allocate exactly one block. Returns true if sucessful.
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*/
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int omfs_allocate_block(struct super_block *sb, u64 block)
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{
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struct buffer_head *bh;
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struct omfs_sb_info *sbi = OMFS_SB(sb);
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int bits_per_entry = 8 * sb->s_blocksize;
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int map, bit;
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int ret = 0;
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u64 tmp;
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tmp = block;
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bit = do_div(tmp, bits_per_entry);
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map = tmp;
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mutex_lock(&sbi->s_bitmap_lock);
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if (map >= sbi->s_imap_size || test_and_set_bit(bit, sbi->s_imap[map]))
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goto out;
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if (sbi->s_bitmap_ino > 0) {
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bh = sb_bread(sb, clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
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if (!bh)
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goto out;
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set_bit(bit, (long *) bh->b_data);
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mark_buffer_dirty(bh);
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brelse(bh);
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}
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ret = 1;
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out:
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mutex_unlock(&sbi->s_bitmap_lock);
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return ret;
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}
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/*
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* Tries to allocate a set of blocks. The request size depends on the
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* type: for inodes, we must allocate sbi->s_mirrors blocks, and for file
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* blocks, we try to allocate sbi->s_clustersize, but can always get away
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* with just one block.
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*/
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int omfs_allocate_range(struct super_block *sb,
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int min_request,
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int max_request,
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u64 *return_block,
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int *return_size)
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{
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struct omfs_sb_info *sbi = OMFS_SB(sb);
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int bits_per_entry = 8 * sb->s_blocksize;
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int ret = 0;
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int i, run, bit;
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mutex_lock(&sbi->s_bitmap_lock);
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for (i = 0; i < sbi->s_imap_size; i++) {
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bit = 0;
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while (bit < bits_per_entry) {
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bit = find_next_zero_bit(sbi->s_imap[i], bits_per_entry,
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bit);
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if (bit == bits_per_entry)
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break;
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run = count_run(&sbi->s_imap[i], bits_per_entry,
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sbi->s_imap_size-i, bit, max_request);
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if (run >= min_request)
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goto found;
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bit += run;
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}
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}
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ret = -ENOSPC;
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goto out;
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found:
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*return_block = i * bits_per_entry + bit;
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*return_size = run;
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ret = set_run(sb, i, bits_per_entry, bit, run, 1);
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out:
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mutex_unlock(&sbi->s_bitmap_lock);
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return ret;
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}
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/*
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* Clears count bits starting at a given block.
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*/
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int omfs_clear_range(struct super_block *sb, u64 block, int count)
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{
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struct omfs_sb_info *sbi = OMFS_SB(sb);
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int bits_per_entry = 8 * sb->s_blocksize;
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u64 tmp;
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int map, bit, ret;
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tmp = block;
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bit = do_div(tmp, bits_per_entry);
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map = tmp;
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if (map >= sbi->s_imap_size)
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return 0;
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mutex_lock(&sbi->s_bitmap_lock);
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ret = set_run(sb, map, bits_per_entry, bit, count, 0);
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mutex_unlock(&sbi->s_bitmap_lock);
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return ret;
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}
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