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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 27 deletions

diff --git a/fs/nilfs2/alloc.c b/fs/nilfs2/alloc.c
index ff0d62ce165b..b15daf871f99 100644
--- 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;
 }