[PATCH v3 2/2] Btrfs: compression must free at least PAGE_SIZE

[Timofey Titovets <nefelim4ag@gmail.com>]

Btrfs already skip store of data where compression didn't free at least one byte.
So make logic better and make check that compression free at least one PAGE_SIZE,
because in another case it useless to store this data compressed

Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
---
 fs/btrfs/lzo.c  | 5 ++++-
 fs/btrfs/zlib.c | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c
index bd0b0938..39678499 100644
--- a/fs/btrfs/lzo.c
+++ b/fs/btrfs/lzo.c
@@ -229,8 +229,11 @@ static int lzo_compress_pages(struct list_head *ws,
 		in_len = min(bytes_left, PAGE_SIZE);
 	}

-	if (tot_out > tot_in)
+	/* Compression must save at least one PAGE_SIZE */
+	if (tot_out + PAGE_SIZE > tot_in) {
+		ret = -E2BIG;
 		goto out;
+	}

 	/* store the size of all chunks of compressed data */
 	cpage_out = kmap(pages[0]);
diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index 135b1082..11e117b5 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -191,7 +191,8 @@ static int zlib_compress_pages(struct list_head *ws,
 		goto out;
 	}

-	if (workspace->strm.total_out >= workspace->strm.total_in) {
+	/* Compression must save at least one PAGE_SIZE */
+	if (workspace->strm.total_out + PAGE_SIZE > workspace->strm.total_in) {
 		ret = -E2BIG;
 		goto out;
 	}
--
2.13.0