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>

1 files changed, 17 insertions, 15 deletions

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index d5a2c9ed9aa7..c3ea8f8cc80a 100644
--- 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;
 }