[PATCH RFC v7 05/16] fuse: make args->in_args[0] to be always the header

Bernd Schubert
2024-11-27T13:40:59Z

This change sets up FUSE operations to have headers in args.in_args[0],
even for opcodes without an actual header. We do this to prepare for
cleanly separating payload from headers in the future.

For opcodes without a header, we use a zero-sized struct as a
placeholder. This approach:
- Keeps things consistent across all FUSE operations
- Will help with payload alignment later
- Avoids future issues when header sizes change

Signed-off-by: Bernd Schubert <bschubert@ddn.com>
---
fs/fuse/dax.c | 11 ++++++-----
fs/fuse/dev.c | 9 +++++----
fs/fuse/dir.c | 32 ++++++++++++++++++--------------
fs/fuse/fuse_i.h | 13 +++++++++++++
fs/fuse/xattr.c | 7 ++++---
5 files changed, 46 insertions(+), 26 deletions(-)

diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index 12ef91d170bb3091ac35a33d2b9dc38330b00948..44bd30d448e4e8c1d8c6b0499e50564fa0828efc 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -240,11 +240,12 @@ static int fuse_send_removemapping(struct inode *inode,

args.opcode = FUSE_REMOVEMAPPING;
args.nodeid = fi->nodeid;
- args.in_numargs = 2;
- args.in_args[0].size = sizeof(*inargp);
- args.in_args[0].value = inargp;
- args.in_args[1].size = inargp->count * sizeof(*remove_one);
- args.in_args[1].value = remove_one;
+ args.in_numargs = 3;
+ fuse_set_zero_arg0(&args);
+ args.in_args[1].size = sizeof(*inargp);
+ args.in_args[1].value = inargp;
+ args.in_args[2].size = inargp->count * sizeof(*remove_one);
+ args.in_args[2].value = remove_one;
return fuse_simple_request(fm, &args);
}

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index fd8898b0c1cca4d117982d5208d78078472b0dfb..63c3865aebb7811fdf4a5729b2181ee8321421dc 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1735,7 +1735,7 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
args = &ap->args;
args->nodeid = outarg->nodeid;
args->opcode = FUSE_NOTIFY_REPLY;
- args->in_numargs = 2;
+ args->in_numargs = 3;
args->in_pages = true;
args->end = fuse_retrieve_end;

@@ -1762,9 +1762,10 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
}
ra->inarg.offset = outarg->offset;
ra->inarg.size = total_len;
- args->in_args[0].size = sizeof(ra->inarg);
- args->in_args[0].value = &ra->inarg;
- args->in_args[1].size = total_len;
+ fuse_set_zero_arg0(args);
+ args->in_args[1].size = sizeof(ra->inarg);
+ args->in_args[1].value = &ra->inarg;
+ args->in_args[2].size = total_len;

err = fuse_simple_notify_reply(fm, args, outarg->notify_unique);
if (err)
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 54104dd48af7c94b312f1a8671c8905542d456c4..ccb240d4262f9399c9c90434aaeaf76b50f223ad 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -175,9 +175,10 @@ static void fuse_lookup_init(struct fuse_conn *fc, struct fuse_args *args,
memset(outarg, 0, sizeof(struct fuse_entry_out));
args->opcode = FUSE_LOOKUP;
args->nodeid = nodeid;
- args->in_numargs = 1;
- args->in_args[0].size = name->len + 1;
- args->in_args[0].value = name->name;
+ args->in_numargs = 2;
+ fuse_set_zero_arg0(args);
+ args->in_args[1].size = name->len + 1;
+ args->in_args[1].value = name->name;
args->out_numargs = 1;
args->out_args[0].size = sizeof(struct fuse_entry_out);
args->out_args[0].value = outarg;
@@ -927,11 +928,12 @@ static int fuse_symlink(struct mnt_idmap *idmap, struct inode *dir,
FUSE_ARGS(args);

args.opcode = FUSE_SYMLINK;
- args.in_numargs = 2;
- args.in_args[0].size = entry->d_name.len + 1;
- args.in_args[0].value = entry->d_name.name;
- args.in_args[1].size = len;
- args.in_args[1].value = link;
+ args.in_numargs = 3;
+ fuse_set_zero_arg0(&args);
+ args.in_args[1].size = entry->d_name.len + 1;
+ args.in_args[1].value = entry->d_name.name;
+ args.in_args[2].size = len;
+ args.in_args[2].value = link;
return create_new_entry(idmap, fm, &args, dir, entry, S_IFLNK);
}

@@ -991,9 +993,10 @@ static int fuse_unlink(struct inode *dir, struct dentry *entry)

args.opcode = FUSE_UNLINK;
args.nodeid = get_node_id(dir);
- args.in_numargs = 1;
- args.in_args[0].size = entry->d_name.len + 1;
- args.in_args[0].value = entry->d_name.name;
+ args.in_numargs = 2;
+ fuse_set_zero_arg0(&args);
+ args.in_args[1].size = entry->d_name.len + 1;
+ args.in_args[1].value = entry->d_name.name;
err = fuse_simple_request(fm, &args);
if (!err) {
fuse_dir_changed(dir);
@@ -1014,9 +1017,10 @@ static int fuse_rmdir(struct inode *dir, struct dentry *entry)

args.opcode = FUSE_RMDIR;
args.nodeid = get_node_id(dir);
- args.in_numargs = 1;
- args.in_args[0].size = entry->d_name.len + 1;
- args.in_args[0].value = entry->d_name.name;
+ args.in_numargs = 2;
+ fuse_set_zero_arg0(&args);
+ args.in_args[1].size = entry->d_name.len + 1;
+ args.in_args[1].value = entry->d_name.name;
err = fuse_simple_request(fm, &args);
if (!err) {
fuse_dir_changed(dir);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index e6cc3d552b1382fc43bfe5191efc46e956ca268c..e3748751e231d0991c050b31bdd84db0b8016f9f 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -938,6 +938,19 @@ struct fuse_mount {
struct rcu_head rcu;
};

+/*
+ * Empty header for FUSE opcodes without specific header needs.
+ * Used as a placeholder in args->in_args[0] for consistency
+ * across all FUSE operations, simplifying request handling.
+ */
+struct fuse_zero_header {};
+
+static inline void fuse_set_zero_arg0(struct fuse_args *args)
+{
+ args->in_args[0].size = sizeof(struct fuse_zero_header);
+ args->in_args[0].value = NULL;
+}
+
static inline struct fuse_mount *get_fuse_mount_super(struct super_block *sb)
{
return sb->s_fs_info;
diff --git a/fs/fuse/xattr.c b/fs/fuse/xattr.c
index 9f568d345c51236ddd421b162820a4ea9b0734f4..93dfb06b6cea045d6df90c61c900680968bda39f 100644
--- a/fs/fuse/xattr.c
+++ b/fs/fuse/xattr.c
@@ -164,9 +164,10 @@ int fuse_removexattr(struct inode *inode, const char *name)

args.opcode = FUSE_REMOVEXATTR;
args.nodeid = get_node_id(inode);
- args.in_numargs = 1;
- args.in_args[0].size = strlen(name) + 1;
- args.in_args[0].value = name;
+ args.in_numargs = 2;
+ fuse_set_zero_arg0(&args);
+ args.in_args[1].size = strlen(name) + 1;
+ args.in_args[1].value = name;
err = fuse_simple_request(fm, &args);
if (err == -ENOSYS) {
fm->fc->no_removexattr = 1;

--
2.43.0