Signed-off-by: Qu Wenruo <w...@suse.com>
---
fs/btrfs/lzo.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c
index 0667ea07f766..3d2ae4c08876 100644
--- a/fs/btrfs/lzo.c
+++ b/fs/btrfs/lzo.c
@@ -17,6 +17,29 @@
#define LZO_LEN 4
+/*
+ * Btrfs LZO compression format
+ *
+ * Regular LZO compressed data extent is consist of:
+ * 1. Header
+ * Fixed size. LZO_LEN (4) bytes long, LE16.
+ * Records the total size (*includes* the header) of real compressed data.
+ *
+ * 2. Segment(s)
+ * Variable size. Includes one segment header, and then data payload.
+ * One btrfs compressed data can have one or more segments.
+ *
+ * 2.1 Segment header
+ * Fixed size. LZO_LEN (4) bytes long, LE16.
+ * Records the total size of the segment (*excludes* the header).
+ *
+ * 2.2 Data Payload
+ * Variable size. Size up limit should be lzo1x_worst_compress(PAGE_SIZE).
+ *
+ * While for inlined LZO compressed data extent, it doesn't have Header, just
+ * one Segment.
+ */
+
struct workspace {
void *mem;
void *buf; /* where decompressed data goes */
--
2.17.0
--
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