diff options
| -rw-r--r-- | fs/btrfs/compression.c | 71 |
1 files changed, 62 insertions, 9 deletions
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 4f5d958c71ad..0e1561cc9578 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -746,6 +746,7 @@ struct bucket_item { struct heuristic_ws { /* Partial copy of input data */ u8 *sample; + u32 sample_size; /* Buckets store counters for each byte value */ struct bucket_item *bucket; struct list_head list; @@ -1221,6 +1222,58 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start, return 1; } +static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end, + struct heuristic_ws *ws) +{ + struct page *page; + u64 index, index_end; + u32 i, curr_sample_pos; + u8 *in_data; + + /* + * Compression handles the input data by chunks of 128KiB + * (defined by BTRFS_MAX_UNCOMPRESSED) + * + * We do the same for the heuristic and loop over the whole range. + * + * MAX_SAMPLE_SIZE - calculated under assumption that heuristic will + * process no more than BTRFS_MAX_UNCOMPRESSED at a time. + */ + if (end - start > BTRFS_MAX_UNCOMPRESSED) + end = start + BTRFS_MAX_UNCOMPRESSED; + + index = start >> PAGE_SHIFT; + index_end = end >> PAGE_SHIFT; + + /* Don't miss unaligned end */ + if (!IS_ALIGNED(end, PAGE_SIZE)) + index_end++; + + curr_sample_pos = 0; + while (index < index_end) { + page = find_get_page(inode->i_mapping, index); + in_data = kmap(page); + /* Handle case where the start is not aligned to PAGE_SIZE */ + i = start % PAGE_SIZE; + while (i < PAGE_SIZE - SAMPLING_READ_SIZE) { + /* Don't sample any garbage from the last page */ + if (start > end - SAMPLING_READ_SIZE) + break; + memcpy(&ws->sample[curr_sample_pos], &in_data[i], + SAMPLING_READ_SIZE); + i += SAMPLING_INTERVAL; + start += SAMPLING_INTERVAL; + curr_sample_pos += SAMPLING_READ_SIZE; + } + kunmap(page); + put_page(page); + + index++; + } + + ws->sample_size = curr_sample_pos; +} + /* * Compression heuristic. * @@ -1240,19 +1293,19 @@ int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end) { struct list_head *ws_list = __find_workspace(0, true); struct heuristic_ws *ws; - u64 index = start >> PAGE_SHIFT; - u64 end_index = end >> PAGE_SHIFT; - struct page *page; + u32 i; + u8 byte; int ret = 1; ws = list_entry(ws_list, struct heuristic_ws, list); - while (index <= end_index) { - page = find_get_page(inode->i_mapping, index); - kmap(page); - kunmap(page); - put_page(page); - index++; + heuristic_collect_sample(inode, start, end, ws); + + memset(ws->bucket, 0, sizeof(*ws->bucket)*BUCKET_SIZE); + + for (i = 0; i < ws->sample_size; i++) { + byte = ws->sample[i]; + ws->bucket[byte].count++; } __free_workspace(0, ws_list, true); |