[PATCH v2 4/4] btrfs: Fix compression related ioctl to run atomic operations in one transaction

[Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>]

From: Naohiro Aota <naota@elisp.net>

Fix the following two problems in compression related ioctl() code.

  a) Updating compression flags and updating inode attribute
     in two separated transaction. So, if something bad happens
     after the former, and before the latter, file system
     would become inconsistent state.

     This patch move them into one transaction.

  b) It updates compression flags here and calls btrfs_set_prop()
     after that. However flags are also updated in this function.

     This patch removes the duplicated code for updating flags
     from ioctl code and aggregates this work to
     btrfs_set_prop_trans() at all. 

Signed-off-by: Naohiro Aota <naota@elisp.net>
Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
---
changelog
	v1->v2: Reflect the following comment from David
        https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg37513.html
---
 fs/btrfs/ioctl.c | 32 +++++++++++---------------------
 1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 0ff2127..40a0fdd 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -221,6 +221,7 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 	u64 ip_oldflags;
 	unsigned int i_oldflags;
 	umode_t mode;
+	const char *comp;
 
 	if (!inode_owner_or_capable(inode))
 		return -EPERM;
@@ -310,40 +311,29 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 	 * things smaller.
 	 */
 	if (flags & FS_NOCOMP_FL) {
-		ip->flags &= ~BTRFS_INODE_COMPRESS;
-		ip->flags |= BTRFS_INODE_NOCOMPRESS;
-
-		ret = btrfs_set_prop(inode, "btrfs.compression", NULL, 0, 0);
-		if (ret && ret != -ENODATA)
-			goto out_drop;
+		comp = "off";
 	} else if (flags & FS_COMPR_FL) {
-		const char *comp;
-
-		ip->flags |= BTRFS_INODE_COMPRESS;
-		ip->flags &= ~BTRFS_INODE_NOCOMPRESS;
-
 		if (root->fs_info->compress_type == BTRFS_COMPRESS_LZO)
 			comp = "lzo";
 		else
 			comp = "zlib";
-		ret = btrfs_set_prop(inode, "btrfs.compression",
-				     comp, strlen(comp), 0);
-		if (ret)
-			goto out_drop;
-
 	} else {
-		ret = btrfs_set_prop(inode, "btrfs.compression", NULL, 0, 0);
-		if (ret && ret != -ENODATA)
-			goto out_drop;
-		ip->flags &= ~(BTRFS_INODE_COMPRESS | BTRFS_INODE_NOCOMPRESS);
+		comp = "";
 	}
 
-	trans = btrfs_start_transaction(root, 1);
+	trans = btrfs_start_transaction(root, 2);
 	if (IS_ERR(trans)) {
 		ret = PTR_ERR(trans);
 		goto out_drop;
 	}
 
+	ret = btrfs_set_prop_trans(trans, inode, "btrfs.compression", comp,
+			       strlen(comp), 0);
+	if (ret && ret != -ENODATA) {
+		btrfs_end_transaction(trans, root);
+		goto out_drop;
+	}
+
 	btrfs_update_iflags(inode);
 	inode_inc_iversion(inode);
 	inode->i_ctime = CURRENT_TIME;
-- 1.8.3.1