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Subject[PATCH 1/3] f2fs: remove costly bit operations for f2fs_find_entry
Date
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>
---
fs/f2fs/dir.c | 32 +++++++++++++++++---------------
1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index d5a2c9e..c3ea8f8 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;
}

--
1.8.4.474.g128a96c


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