[PATCH v7 4/6] Btrfs: heuristic add detection of repeated data patterns
From: Timofey Titovets <hidden>
Date: 2017-08-25 09:19:14
Subsystem:
btrfs file system, filesystems (vfs and infrastructure), the rest · Maintainers:
Chris Mason, David Sterba, Alexander Viro, Christian Brauner, Linus Torvalds
Walk over data sample and use memcmp to detect repeated data (like zeroed) Signed-off-by: Timofey Titovets <redacted> --- fs/btrfs/heuristic.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/fs/btrfs/heuristic.c b/fs/btrfs/heuristic.c
index 5192e51ab81e..f1fa6e4f1c11 100644
--- a/fs/btrfs/heuristic.c
+++ b/fs/btrfs/heuristic.c@@ -66,6 +66,19 @@ static struct list_head *heuristic_alloc_workspace(void) return ERR_PTR(-ENOMEM); } +static bool sample_repeated_patterns(struct workspace *ws) +{ + u32 i = 0; + u8 *p = ws->sample; + + for (; i < ws->sample_size - READ_SIZE; i += READ_SIZE) { + if(memcpy(&p[i], &p[i + READ_SIZE], READ_SIZE)) + return false; + } + + return true; +} + static int heuristic(struct list_head *ws, struct inode *inode, u64 start, u64 end) {
@@ -115,6 +128,9 @@ static int heuristic(struct list_head *ws, struct inode *inode, workspace->sample_size = b; + if (sample_repeated_patterns(workspace)) + return 1; + memset(workspace->bucket, 0, sizeof(*workspace->bucket)*BUCKET_SIZE); for (a = 0; a < workspace->sample_size; a++) { --
2.14.1