[PATCH v5 4/6] Btrfs: heuristic add detection of zeroed sample
From: Timofey Titovets <hidden>
Date: 2017-08-23 00:27:12
Subsystem:
btrfs file system, filesystems (vfs and infrastructure), the rest · Maintainers:
Chris Mason, David Sterba, Alexander Viro, Christian Brauner, Linus Torvalds
Use memcmp for check sample data to zeroes. Signed-off-by: Timofey Titovets <redacted> --- fs/btrfs/heuristic.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/fs/btrfs/heuristic.c b/fs/btrfs/heuristic.c
index 5336638a3b7c..4557ea1db373 100644
--- a/fs/btrfs/heuristic.c
+++ b/fs/btrfs/heuristic.c@@ -73,6 +73,21 @@ static struct list_head *heuristic_alloc_workspace(void) return ERR_PTR(-ENOMEM); } +static bool sample_zeroed(struct workspace *workspace) +{ + u32 i; + u8 zero[READ_SIZE]; + + memset(&zero, 0, sizeof(zero)); + + for (i = 0; i < workspace->sample_size; i += sizeof(zero)) { + if (memcmp(&workspace->sample[i], &zero, sizeof(zero))) + return false; + } + + return true; +} + static int heuristic(struct list_head *ws, struct inode *inode, u64 start, u64 end) {
@@ -110,6 +125,9 @@ static int heuristic(struct list_head *ws, struct inode *inode, workspace->sample_size = b; + if (sample_zeroed(workspace)) + return 1; + memset(workspace->bucket, 0, sizeof(*workspace->bucket)*BUCKET_SIZE); for (a = 0; a < workspace->sample_size; a++) { --
2.14.1