fs/omfs/bitmap.c

Source file repositories/reference/linux-study-clean/fs/omfs/bitmap.c

File Facts

System
Linux kernel
Corpus path
fs/omfs/bitmap.c
Extension
.c
Size
4149 bytes
Lines
195
Domain
Core OS
Bucket
VFS And Filesystem Core
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

if (bit >= nbits) {
			bit = 0;
			map++;

			mark_buffer_dirty(bh);
			brelse(bh);
			bh = sb_bread(sb,
				clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
			if (!bh)
				goto out;
		}
		if (set) {
			set_bit(bit, sbi->s_imap[map]);
			set_bit(bit, (unsigned long *)bh->b_data);
		} else {
			clear_bit(bit, sbi->s_imap[map]);
			clear_bit(bit, (unsigned long *)bh->b_data);
		}
	}
	mark_buffer_dirty(bh);
	brelse(bh);
	err = 0;
out:
	return err;
}

/*
 * Tries to allocate exactly one block.  Returns true if successful.
 */
int omfs_allocate_block(struct super_block *sb, u64 block)
{
	struct buffer_head *bh;
	struct omfs_sb_info *sbi = OMFS_SB(sb);
	int bits_per_entry = 8 * sb->s_blocksize;
	unsigned int map, bit;
	int ret = 0;
	u64 tmp;

	tmp = block;
	bit = do_div(tmp, bits_per_entry);
	map = tmp;

	mutex_lock(&sbi->s_bitmap_lock);
	if (map >= sbi->s_imap_size || test_and_set_bit(bit, sbi->s_imap[map]))
		goto out;

	if (sbi->s_bitmap_ino > 0) {
		bh = sb_bread(sb, clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
		if (!bh)
			goto out;

		set_bit(bit, (unsigned long *)bh->b_data);
		mark_buffer_dirty(bh);
		brelse(bh);
	}
	ret = 1;
out:
	mutex_unlock(&sbi->s_bitmap_lock);
	return ret;
}


/*
 *  Tries to allocate a set of blocks.	The request size depends on the
 *  type: for inodes, we must allocate sbi->s_mirrors blocks, and for file
 *  blocks, we try to allocate sbi->s_clustersize, but can always get away
 *  with just one block.
 */
int omfs_allocate_range(struct super_block *sb,
			int min_request,
			int max_request,
			u64 *return_block,
			int *return_size)
{
	struct omfs_sb_info *sbi = OMFS_SB(sb);
	int bits_per_entry = 8 * sb->s_blocksize;
	int ret = 0;
	int i, run, bit;

	mutex_lock(&sbi->s_bitmap_lock);
	for (i = 0; i < sbi->s_imap_size; i++) {
		bit = 0;
		while (bit < bits_per_entry) {
			bit = find_next_zero_bit(sbi->s_imap[i], bits_per_entry,
				bit);

			if (bit == bits_per_entry)
				break;

			run = count_run(&sbi->s_imap[i], bits_per_entry,

Annotation

Implementation Notes