f2fs: remove costly bit operations for f2fs_find_entry

It turns out that a bit operation like find_next_bit is not always fast enough
for f2fs_find_entry.
Instead, it is pretty much simple and fast to traverse each dentries.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index d5a2c9ed9aa73d5c118843c91891452e2519af2e..c3ea8f8cc80a1d9b3a7ec4c330e2b800b3e3fb6e 100644 (file)
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -93,16 +93,20 @@ static struct f2fs_dir_entry *find_in_block(struct page *dentry_page,
                        f2fs_hash_t namehash, struct page **res_page)
 {
        struct f2fs_dir_entry *de;
-       unsigned long bit_pos, end_pos, next_pos;
+       unsigned long bit_pos = 0;
        struct f2fs_dentry_block *dentry_blk = kmap(dentry_page);
-       int slots;
+       int max_len = 0;
 
-       bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
-                                       NR_DENTRY_IN_BLOCK, 0);
        while (bit_pos < NR_DENTRY_IN_BLOCK) {
                de = &dentry_blk->dentry[bit_pos];
-               slots = GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
-
+               if (!test_bit_le(bit_pos, &dentry_blk->dentry_bitmap)) {
+                       if (bit_pos == 0)
+                               max_len = 1;
+                       else if (!test_bit_le(bit_pos - 1, &dentry_blk->dentry_bitmap))
+                               max_len++;
+                       bit_pos++;
+                       continue;
+               }
                if (early_match_name(name, namelen, namehash, de)) {
                        if (!memcmp(dentry_blk->filename[bit_pos],
                                                        name, namelen)) {
@@ -110,20 +114,18 @@ static struct f2fs_dir_entry *find_in_block(struct page *dentry_page,
                                goto found;
                        }
                }
-               next_pos = bit_pos + slots;
-               bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
-                               NR_DENTRY_IN_BLOCK, next_pos);
-               if (bit_pos >= NR_DENTRY_IN_BLOCK)
-                       end_pos = NR_DENTRY_IN_BLOCK;
-               else
-                       end_pos = bit_pos;
-               if (*max_slots < end_pos - next_pos)
-                       *max_slots = end_pos - next_pos;
+               if (max_len > *max_slots) {
+                       *max_slots = max_len;
+                       max_len = 0;
+               }
+               bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
        }
 
        de = NULL;
        kunmap(dentry_page);
 found:
+       if (max_len > *max_slots)
+               *max_slots = max_len;
        return de;
 }