Copy sample data from input data range to sample buffer
then calculate byte type count for that sample into bucket.
Signed-off-by: Timofey Titovets <nefelim4ag@xxxxxxxxx>
---
fs/btrfs/heuristic.c | 38 +++++++++++++++++++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/heuristic.c b/fs/btrfs/heuristic.c
index e3924c87af08..5192e51ab81e 100644
--- a/fs/btrfs/heuristic.c
+++ b/fs/btrfs/heuristic.c
@@ -69,8 +69,20 @@ static struct list_head *heuristic_alloc_workspace(void)
static int heuristic(struct list_head *ws, struct inode *inode,
u64 start, u64 end)
{
+ struct workspace *workspace = list_entry(ws, struct workspace, list);
struct page *page;
u64 index, index_end;
+ u32 a, b;
+ u8 *in_data, *sample = workspace->sample;
+ u8 byte;
+
+ /*
+ * Compression only handle first 128kb of input range
+ * And just shift over range in loop for compressing it.
+ * Let's do the same.
+ */
+ if (end - start > BTRFS_MAX_UNCOMPRESSED)
+ end = start + BTRFS_MAX_UNCOMPRESSED;
index = start >> PAGE_SHIFT;
index_end = end >> PAGE_SHIFT;
@@ -79,13 +91,37 @@ static int heuristic(struct list_head *ws, struct inode *inode,
if (!IS_ALIGNED(end, PAGE_SIZE))
index_end++;
+ b = 0;
for (; index < index_end; index++) {
page = find_get_page(inode->i_mapping, index);
- kmap(page);
+ in_data = kmap(page);
+ /* Handle case where start unaligned to PAGE_SIZE */
+ a = start%PAGE_SIZE;
+ while (a < PAGE_SIZE - READ_SIZE) {
+ /* Prevent sample overflow */
+ if (b >= MAX_SAMPLE_SIZE)
+ break;
+ /* Don't sample mem trash from last page */
+ if (start > end - READ_SIZE)
+ break;
+ memcpy(&sample[b], &in_data[a], READ_SIZE);
+ a += ITER_SHIFT;
+ start += ITER_SHIFT;
+ b += READ_SIZE;
+ }
kunmap(page);
put_page(page);
}
+ workspace->sample_size = b;
+
+ memset(workspace->bucket, 0, sizeof(*workspace->bucket)*BUCKET_SIZE);
+
+ for (a = 0; a < workspace->sample_size; a++) {
+ byte = sample[a];
+ workspace->bucket[byte].count++;
+ }
+
return 1;
}
--
2.14.1
--
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