[PATCH] btrfs: inode: Don't compress if NODATASUM or NODATACOW set

[Qu Wenruo <wqu@suse.com>]

As btrfs(5) specified:

	Note
	If nodatacow or nodatasum are enabled, compression is disabled.

If NODATASUM or NODATACOW set, we should not compress the extent.

And in fact, we have bug report about corrupted compressed extent
leading to memory corruption in mail list.
Although it's mostly buggy lzo implementation causing the problem, btrfs
still needs to be fixed to meet the specification.

Reported-by: James Harvey <jamespharvey20@gmail.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/inode.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d241285a0d2a..dbef3f404559 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -396,6 +396,14 @@ static inline int inode_need_compress(struct inode *inode, u64 start, u64 end)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 
+	/*
+	 * Btrfs doesn't support compression without csum or CoW.
+	 * This should have the highest priority.
+	 */
+	if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW ||
+	    BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
+		return 0;
+
 	/* force compress */
 	if (btrfs_test_opt(fs_info, FORCE_COMPRESS))
 		return 1;
-- 
2.17.0