Re: [PATCH 1/2] btrfs: avoid Wmaybe-uninitialized warnings

[Arnd Bergmann]

On Mon, Jul 10, 2023, at 21:12, Arnd Bergmann wrote:
>
> building for arm32 (see below), I get maybe 20 failed builds, but
> for x86 this is lower, maybe 2. I had attempted to work around
> each one of the ones I saw, but ended up with a huge patch to
> cover all architectures and compilers in random versions.

FWIW, this is the last version of my workaround patch from January
before I gave up on trying to fix all the btrfs warnings on
uninitialized variables.

     Arnd

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index db79e6b0a693f..ab2e54930ee5f 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5656,7 +5656,7 @@ struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry)
 	struct inode *inode;
 	struct btrfs_root *root = BTRFS_I(dir)->root;
 	struct btrfs_root *sub_root = root;
-	struct btrfs_key location;
+	struct btrfs_key location = {};
 	u8 di_type = 0;
 	int ret = 0;
 
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index ba769a1eb87ab..79e0c3a14c7fd 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1730,7 +1730,7 @@ static noinline int btrfs_ioctl_tree_search(struct inode *inode,
 					    void __user *argp)
 {
 	struct btrfs_ioctl_search_args __user *uargs = argp;
-	struct btrfs_ioctl_search_key sk;
+	struct btrfs_ioctl_search_key sk = {};
 	int ret;
 	size_t buf_size;
 
@@ -1760,7 +1760,7 @@ static noinline int btrfs_ioctl_tree_search_v2(struct inode *inode,
 					       void __user *argp)
 {
 	struct btrfs_ioctl_search_args_v2 __user *uarg = argp;
-	struct btrfs_ioctl_search_args_v2 args;
+	struct btrfs_ioctl_search_args_v2 args = {};
 	int ret;
 	size_t buf_size;
 	const size_t buf_limit = SZ_16M;
@@ -2971,7 +2971,7 @@ static void get_block_group_info(struct list_head *groups_list,
 static long btrfs_ioctl_space_info(struct btrfs_fs_info *fs_info,
 				   void __user *arg)
 {
-	struct btrfs_ioctl_space_args space_args;
+	struct btrfs_ioctl_space_args space_args = {};
 	struct btrfs_ioctl_space_info space;
 	struct btrfs_ioctl_space_info *dest;
 	struct btrfs_ioctl_space_info *dest_orig;
@@ -3132,7 +3132,7 @@ static noinline long btrfs_ioctl_start_sync(struct btrfs_root *root,
 static noinline long btrfs_ioctl_wait_sync(struct btrfs_fs_info *fs_info,
 					   void __user *argp)
 {
-	u64 transid;
+	u64 transid = 0;
 
 	if (argp) {
 		if (copy_from_user(&transid, argp, sizeof(transid)))
@@ -4106,7 +4106,7 @@ static int btrfs_ioctl_set_fslabel(struct file *file, void __user *arg)
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_super_block *super_block = fs_info->super_copy;
 	struct btrfs_trans_handle *trans;
-	char label[BTRFS_LABEL_SIZE];
+	char label[BTRFS_LABEL_SIZE] = {};
 	int ret;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -4248,7 +4248,7 @@ static int btrfs_ioctl_set_features(struct file *file, void __user *arg)
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_super_block *super_block = fs_info->super_copy;
-	struct btrfs_ioctl_feature_flags flags[2];
+	struct btrfs_ioctl_feature_flags flags[2] = {};
 	struct btrfs_trans_handle *trans;
 	u64 newflags;
 	int ret;
@@ -4320,7 +4320,7 @@ static int _btrfs_ioctl_send(struct inode *inode, void __user *argp, bool compat
 
 	if (compat) {
 #if defined(CONFIG_64BIT) && defined(CONFIG_COMPAT)
-		struct btrfs_ioctl_send_args_32 args32;
+		struct btrfs_ioctl_send_args_32 args32 = {};
 
 		ret = copy_from_user(&args32, argp, sizeof(args32));
 		if (ret)
@@ -4369,7 +4369,7 @@ static int btrfs_ioctl_encoded_read(struct file *file, void __user *argp,
 
 	if (compat) {
 #if defined(CONFIG_64BIT) && defined(CONFIG_COMPAT)
-		struct btrfs_ioctl_encoded_io_args_32 args32;
+		struct btrfs_ioctl_encoded_io_args_32 args32 = {};
 
 		copy_end = offsetofend(struct btrfs_ioctl_encoded_io_args_32,
 				       flags);
@@ -4433,7 +4433,7 @@ static int btrfs_ioctl_encoded_read(struct file *file, void __user *argp,
 
 static int btrfs_ioctl_encoded_write(struct file *file, void __user *argp, bool compat)
 {
-	struct btrfs_ioctl_encoded_io_args args;
+	struct btrfs_ioctl_encoded_io_args args = {};
 	struct iovec iovstack[UIO_FASTIOV];
 	struct iovec *iov = iovstack;
 	struct iov_iter iter;
@@ -4453,7 +4453,7 @@ static int btrfs_ioctl_encoded_write(struct file *file, void __user *argp, bool
 
 	if (compat) {
 #if defined(CONFIG_64BIT) && defined(CONFIG_COMPAT)
-		struct btrfs_ioctl_encoded_io_args_32 args32;
+		struct btrfs_ioctl_encoded_io_args_32 args32 = {};
 
 		if (copy_from_user(&args32, argp, sizeof(args32))) {
 			ret = -EFAULT;
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index f41da7ac360d8..e93583f3f928b 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -4362,6 +4362,10 @@ int btrfs_qgroup_trace_subtree_after_cow(struct btrfs_trans_handle *trans,
 	}
 	node = blocks->blocks[level].rb_node;
 
+	if (!node) {
+		spin_unlock(&blocks->lock);
+		goto out;
+	}
 	while (node) {
 		block = rb_entry(node, struct btrfs_qgroup_swapped_block, node);
 		if (block->subvol_bytenr < subvol_eb->start) {
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index e5c963bb873db..af2e153543a5c 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -1875,7 +1875,7 @@ static int get_cur_inode_state(struct send_ctx *sctx, u64 ino, u64 gen,
 	int left_ret;
 	int right_ret;
 	u64 left_gen;
-	u64 right_gen;
+	u64 right_gen = 0;
 	struct btrfs_inode_info info;
 
 	ret = get_inode_info(sctx->send_root, ino, &info);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index de96d26f81f64..43b200102d1e6 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2618,7 +2618,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	struct block_device *bdev;
 	struct super_block *sb = fs_info->sb;
 	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
-	struct btrfs_fs_devices *seed_devices;
+	struct btrfs_fs_devices *seed_devices = NULL;
 	u64 orig_super_total_bytes;
 	u64 orig_super_num_devices;
 	int ret = 0;