Walk over data sample and use memcmp to detect
repeated data (like zeroed)
Signed-off-by: Timofey Titovets <nefelim4ag@xxxxxxxxx>
---
fs/btrfs/compression.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index e2419639ae7f..1cb4df023d5e 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1200,6 +1200,16 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
return 1;
}
+
+static bool sample_repeated_patterns(struct heuristic_ws *ws)
+{
+ u32 half_of_sample = ws->sample_size / 2;
+ u8 *p = ws->sample;
+
+ return !memcmp(&p[0], &p[half_of_sample], half_of_sample);
+}
+
+
static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end,
struct heuristic_ws *ws)
{
@@ -1278,6 +1288,11 @@ int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
heuristic_collect_sample(inode, start, end, ws);
+ if (sample_repeated_patterns(ws)) {
+ ret = 1;
+ goto out;
+ }
+
memset(ws->bucket, 0, sizeof(*ws->bucket)*BUCKET_SIZE);
for (i = 0; i < ws->sample_size; i++) {
@@ -1285,7 +1300,7 @@ int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
ws->bucket[byte].count++;
}
+out:
__free_workspace(0, ws_list, true);
-
return ret;
}
--
2.14.2
--
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