[PATCH] kernel: force atomic renames in ubifs

[Rafał Miłecki]

From: Rafał Miłecki <rafal at milecki.pl>

This deals with user-spaces apps that don't handle all syncing
correctly. It prevents user ending up with an empty file.

Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
---
 .../510-ubifs-force-atomic-renames.patch      | 46 +++++++++++++++++++
 .../510-ubifs-force-atomic-renames.patch      | 46 +++++++++++++++++++
 2 files changed, 92 insertions(+)
 create mode 100644 target/linux/generic/pending-5.10/510-ubifs-force-atomic-renames.patch
 create mode 100644 target/linux/generic/pending-5.4/510-ubifs-force-atomic-renames.patch

diff --git a/target/linux/generic/pending-5.10/510-ubifs-force-atomic-renames.patch b/target/linux/generic/pending-5.10/510-ubifs-force-atomic-renames.patch
new file mode 100644
index 0000000000..80f5f1b910
--- /dev/null
+++ b/target/linux/generic/pending-5.10/510-ubifs-force-atomic-renames.patch
@@ -0,0 +1,46 @@
+From: Richard Weinberger <richard at nod.at>
+Date: Mon, 28 Feb 2022 16:07:41 +0100
+Subject: [PATCH] ubifs: force atomic renames
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Before actual rename make sure that the old inode data has been flash
+written. This is similar to what other filesystems do and workarounds
+bugs in some user-space apps.
+
+With this change updating file using tmpfile & rename() will never
+result in losing all content e.g. on power cut.
+
+Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
+---
+ fs/ubifs/dir.c | 18 ++++++++++++++----
+ 1 file changed, 14 insertions(+), 4 deletions(-)
+
+--- a/fs/ubifs/dir.c
++++ b/fs/ubifs/dir.c
+@@ -1287,10 +1287,20 @@ static int do_rename(struct inode *old_d
+ 			return err;
+ 	}
+ 
+-	if (unlink && is_dir) {
+-		err = ubifs_check_dir_empty(new_inode);
+-		if (err)
+-			return err;
++	if (unlink) {
++		if (is_dir) {
++			err = ubifs_check_dir_empty(new_inode);
++			if (err)
++				return err;
++		} else {
++			err = filemap_fdatawrite(old_inode->i_mapping);
++			if (err)
++				return err;
++
++			err = ubifs_sync_wbufs_by_inode(c, old_inode);
++			if (err)
++				return err;
++		}
+ 	}
+ 
+ 	err = fscrypt_setup_filename(old_dir, &old_dentry->d_name, 0, &old_nm);
diff --git a/target/linux/generic/pending-5.4/510-ubifs-force-atomic-renames.patch b/target/linux/generic/pending-5.4/510-ubifs-force-atomic-renames.patch
new file mode 100644
index 0000000000..30bc686854
--- /dev/null
+++ b/target/linux/generic/pending-5.4/510-ubifs-force-atomic-renames.patch
@@ -0,0 +1,46 @@
+From: Richard Weinberger <richard at nod.at>
+Date: Mon, 28 Feb 2022 16:07:41 +0100
+Subject: [PATCH] ubifs: force atomic renames
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Before actual rename make sure that the old inode data has been flash
+written. This is similar to what other filesystems do and workarounds
+bugs in some user-space apps.
+
+With this change updating file using tmpfile & rename() will never
+result in losing all content e.g. on power cut.
+
+Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
+---
+ fs/ubifs/dir.c | 18 ++++++++++++++----
+ 1 file changed, 14 insertions(+), 4 deletions(-)
+
+--- a/fs/ubifs/dir.c
++++ b/fs/ubifs/dir.c
+@@ -1295,10 +1295,20 @@ static int do_rename(struct inode *old_d
+ 			return err;
+ 	}
+ 
+-	if (unlink && is_dir) {
+-		err = ubifs_check_dir_empty(new_inode);
+-		if (err)
+-			return err;
++	if (unlink) {
++		if (is_dir) {
++			err = ubifs_check_dir_empty(new_inode);
++			if (err)
++				return err;
++		} else {
++			err = filemap_fdatawrite(old_inode->i_mapping);
++			if (err)
++				return err;
++
++			err = ubifs_sync_wbufs_by_inode(c, old_inode);
++			if (err)
++				return err;
++		}
+ 	}
+ 
+ 	err = fscrypt_setup_filename(old_dir, &old_dentry->d_name, 0, &old_nm);
-- 
2.34.1