omfs: add bitmap routines

Add block allocation and block bitmap management routines for OMFS.

Signed-off-by: Bob Copeland

---
fs/omfs/bitmap.c | 192 ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++
1 file changed, 192 insertions(+)

Index: linux-2.6/fs/omfs/bitmap.c
================================================== =================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/fs/omfs/bitmap.c 2008-04-26 15:34:08.000000000 -0400
@@ -0,0 +1,192 @@
+#include
+#include
+#include
+#include
+#include "omfs.h"
+
+unsigned long omfs_count_free(struct super_block *sb)
+{
+ unsigned int i;
+ unsigned long sum = 0;
+ struct omfs_sb_info *sbi = OMFS_SB(sb);
+ int nbits = sb->s_blocksize * 8;
+
+ for (i = 0; i < sbi->s_imap_size; i++)
+ sum += nbits - bitmap_weight(sbi->s_imap[i], nbits);
+
+ return sum;
+}
+
+/*
+ * Counts the run of zero bits starting at bit up to max.
+ * It handles the case where a run might spill over a buffer.
+ * Called with bitmap lock.
+ */
+static int count_run(unsigned long **addr, int nbits,
+ int addrlen, int bit, int max)
+{
+ int count = 0;
+ int x;
+
+ for (; addrlen > 0; addrlen--, addr++) {
+ x = find_next_bit(*addr, nbits, bit);
+ count += x - bit;
+
+ if (x < nbits || count > max)
+ return min(count, max);
+
+ bit = 0;
+ }
+ return min(count, max);
+}
+
+/*
+ * Sets or clears the run of count bits starting with bit.
+ * Called with bitmap lock.
+ */
+static int set_run(struct super_block *sb, int map,
+ int nbits, int bit, int count, int set)
+{
+ int i;
+ int err;
+ struct buffer_head *bh;
+ struct omfs_sb_info *sbi = OMFS_SB(sb);
+
+ err = -ENOMEM;
+ bh = sb_bread(sb, clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
+ if (!bh)
+ goto out;
+
+ for (i = 0; i < count; i++, bit++) {
+ 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, (long *) bh->b_data);
+ } else {
+ clear_bit(bit, sbi->s_imap[map]);
+ clear_bit(bit, (long *) bh->b_data);
+ }
+ }
+ mark_buffer_dirty(bh);
+ brelse(bh);
+ err = 0;
+out:
+ return err;
+}
+
+/*
+ * Tries to allocate exactly one block. Returns true if sucessful.
+ */
+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;
+ 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, (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,
+ sbi->s_imap_size-i, bit, max_request);
+
+ if (run >= min_request)
+ goto found;
+ bit += run;
+ }
+ }
+ ret = -ENOSPC;
+ goto out;
+
+found:
+ *return_block = i * bits_per_entry + bit;
+ *return_size = run;
+ ret = set_run(sb, i, bits_per_entry, bit, run, 1);
+
+out:
+ mutex_unlock(&sbi->s_bitmap_lock);
+ return ret;
+}
+
+/*
+ * Clears count bits starting at a given block.
+ */
+int omfs_clear_range(struct super_block *sb, u64 block, int count)
+{
+ struct omfs_sb_info *sbi = OMFS_SB(sb);
+ int bits_per_entry = 8 * sb->s_blocksize;
+ u64 tmp;
+ int map, bit, ret;
+
+ tmp = block;
+ bit = do_div(tmp, bits_per_entry);
+ map = tmp;
+
+ if (map >= sbi->s_imap_size)
+ return 0;
+
+ mutex_lock(&sbi->s_bitmap_lock);
+ ret = set_run(sb, map, bits_per_entry, bit, count, 0);
+ mutex_unlock(&sbi->s_bitmap_lock);
+ return ret;
+}

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