nilfs2: refactor nilfs_palloc_find_available_slot()

The current implementation of nilfs_palloc_find_available_slot() function
is overkill.  The underlying bit search routine is well optimized, so this
uses it more simply in nilfs_palloc_find_available_slot().

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/nilfs2/alloc.c b/fs/nilfs2/alloc.c
index ff0d62ce165b02135e436cfe0ccb903eb39cdf72..b15daf871f996554f024b83be393bb09f1baafd4 100644 (file)
--- a/fs/nilfs2/alloc.c
+++ b/fs/nilfs2/alloc.c
@@ -335,39 +335,33 @@ void *nilfs_palloc_block_get_entry(const struct inode *inode, __u64 nr,
  */
 static int nilfs_palloc_find_available_slot(unsigned char *bitmap,
                                            unsigned long target,
-                                           int bsize,
+                                           unsigned bsize,
                                            spinlock_t *lock)
 {
-       int curr, pos, end, i;
+       int pos, end = bsize;
 
-       if (target > 0) {
-               end = (target + BITS_PER_LONG - 1) & ~(BITS_PER_LONG - 1);
-               if (end > bsize)
-                       end = bsize;
-               pos = nilfs_find_next_zero_bit(bitmap, end, target);
-               if (pos < end && !nilfs_set_bit_atomic(lock, pos, bitmap))
-                       return pos;
-       } else {
-               end = 0;
+       if (likely(target < bsize)) {
+               pos = target;
+               do {
+                       pos = nilfs_find_next_zero_bit(bitmap, end, pos);
+                       if (pos >= end)
+                               break;
+                       if (!nilfs_set_bit_atomic(lock, pos, bitmap))
+                               return pos;
+               } while (++pos < end);
+
+               end = target;
        }
 
-       for (i = 0, curr = end;
-            i < bsize;
-            i += BITS_PER_LONG, curr += BITS_PER_LONG) {
-               /* wrap around */
-               if (curr >= bsize)
-                       curr = 0;
-               while (*((unsigned long *)bitmap + curr / BITS_PER_LONG)
-                      != ~0UL) {
-                       end = curr + BITS_PER_LONG;
-                       if (end > bsize)
-                               end = bsize;
-                       pos = nilfs_find_next_zero_bit(bitmap, end, curr);
-                       if (pos < end &&
-                           !nilfs_set_bit_atomic(lock, pos, bitmap))
-                               return pos;
-               }
+       /* wrap around */
+       for (pos = 0; pos < end; pos++) {
+               pos = nilfs_find_next_zero_bit(bitmap, end, pos);
+               if (pos >= end)
+                       break;
+               if (!nilfs_set_bit_atomic(lock, pos, bitmap))
+                       return pos;
        }
+
        return -ENOSPC;
 }