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Message-Id: <20251223-fuse-compounds-upstream-v1-2-7bade663947b@ddn.com>
Date: Tue, 23 Dec 2025 13:05:30 +0100
From: Horst Birthelmer <hbirthelmer@...glemail.com>
To: Miklos Szeredi <miklos@...redi.hu>, Bernd Schubert <bschubert@....com>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
Horst Birthelmer <hbirthelmer@....com>
Subject: [PATCH RFC 2/2] fuse: add an implementation of open+getattr
The discussion about compound commands in fuse was
started over an argument to add a new operation that
will open a file and return its attributes in the same operation.
Here is a demonstration of that use case with compound commands.
Signed-off-by: Horst Birthelmer <hbirthelmer@....com>
---
fs/fuse/file.c | 115 +++++++++++++++++++++++++++++++++++++++++++++++--------
fs/fuse/fuse_i.h | 6 ++-
fs/fuse/inode.c | 6 +++
fs/fuse/ioctl.c | 2 +-
4 files changed, 111 insertions(+), 18 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 01bc894e9c2b..fd7f90f9f676 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -126,8 +126,74 @@ static void fuse_file_put(struct fuse_file *ff, bool sync)
}
}
+static int fuse_compound_open_getattr(struct fuse_mount *fm, u64 nodeid,
+ int flags, int opcode,
+ struct fuse_file *ff,
+ struct fuse_attr_out *outattrp,
+ struct fuse_open_out *outargp)
+{
+ struct fuse_compound_req *compound;
+ struct fuse_args open_args = {}, getattr_args = {};
+ struct fuse_open_in open_in = {};
+ struct fuse_getattr_in getattr_in = {};
+ int err;
+
+ /* Build compound request with flag to execute in the given order */
+ compound = fuse_compound_alloc(fm, 0);
+ if (IS_ERR(compound))
+ return PTR_ERR(compound);
+
+ /* Add OPEN */
+ open_in.flags = flags & ~(O_CREAT | O_EXCL | O_NOCTTY);
+ if (!fm->fc->atomic_o_trunc)
+ open_in.flags &= ~O_TRUNC;
+
+ if (fm->fc->handle_killpriv_v2 &&
+ (open_in.flags & O_TRUNC) && !capable(CAP_FSETID)) {
+ open_in.open_flags |= FUSE_OPEN_KILL_SUIDGID;
+ }
+ open_args.opcode = opcode;
+ open_args.nodeid = nodeid;
+ open_args.in_numargs = 1;
+ open_args.in_args[0].size = sizeof(open_in);
+ open_args.in_args[0].value = &open_in;
+ open_args.out_numargs = 1;
+ open_args.out_args[0].size = sizeof(struct fuse_open_out);
+ open_args.out_args[0].value = outargp;
+
+ err = fuse_compound_add(compound, &open_args);
+ if (err)
+ goto out;
+
+ /* Add GETATTR */
+ getattr_args.opcode = FUSE_GETATTR;
+ getattr_args.nodeid = nodeid;
+ getattr_args.in_numargs = 1;
+ getattr_args.in_args[0].size = sizeof(getattr_in);
+ getattr_args.in_args[0].value = &getattr_in;
+ getattr_args.out_numargs = 1;
+ getattr_args.out_args[0].size = sizeof(struct fuse_attr_out);
+ getattr_args.out_args[0].value = outattrp;
+
+ err = fuse_compound_add(compound, &getattr_args);
+ if (err)
+ goto out;
+
+ err = fuse_compound_send(compound);
+ if (err)
+ goto out;
+
+ ff->fh = outargp->fh;
+ ff->open_flags = outargp->open_flags;
+
+out:
+ fuse_compound_free(compound);
+ return err;
+}
+
struct fuse_file *fuse_file_open(struct fuse_mount *fm, u64 nodeid,
- unsigned int open_flags, bool isdir)
+ struct inode *inode,
+ unsigned int open_flags, bool isdir)
{
struct fuse_conn *fc = fm->fc;
struct fuse_file *ff;
@@ -153,23 +219,41 @@ struct fuse_file *fuse_file_open(struct fuse_mount *fm, u64 nodeid,
if (open) {
/* Store outarg for fuse_finish_open() */
struct fuse_open_out *outargp = &ff->args->open_outarg;
- int err;
+ int err = -ENOSYS;
+
+ if (inode && fc->compound_open_getattr) {
+ struct fuse_attr_out attr_outarg;
+ err = fuse_compound_open_getattr(fm, nodeid, open_flags,
+ opcode, ff, &attr_outarg, outargp);
+ if (!err)
+ fuse_change_attributes(inode, &attr_outarg.attr, NULL,
+ ATTR_TIMEOUT(&attr_outarg),
+ fuse_get_attr_version(fc));
+ }
+ if (err == -ENOSYS) {
+ err = fuse_send_open(fm, nodeid, open_flags, opcode, outargp);
- err = fuse_send_open(fm, nodeid, open_flags, opcode, outargp);
- if (!err) {
- ff->fh = outargp->fh;
- ff->open_flags = outargp->open_flags;
- } else if (err != -ENOSYS) {
- fuse_file_free(ff);
- return ERR_PTR(err);
- } else {
- if (isdir) {
+ if (!err) {
+ ff->fh = outargp->fh;
+ ff->open_flags = outargp->open_flags;
+ }
+ }
+
+ if (err) {
+ if (err != -ENOSYS) {
+ /* err is not ENOSYS */
+ fuse_file_free(ff);
+ return ERR_PTR(err);
+ } else {
/* No release needed */
kfree(ff->args);
ff->args = NULL;
- fc->no_opendir = 1;
- } else {
- fc->no_open = 1;
+
+ /* we don't have open */
+ if (isdir)
+ fc->no_opendir = 1;
+ else
+ fc->no_open = 1;
}
}
}
@@ -185,11 +269,10 @@ struct fuse_file *fuse_file_open(struct fuse_mount *fm, u64 nodeid,
int fuse_do_open(struct fuse_mount *fm, u64 nodeid, struct file *file,
bool isdir)
{
- struct fuse_file *ff = fuse_file_open(fm, nodeid, file->f_flags, isdir);
+ struct fuse_file *ff = fuse_file_open(fm, nodeid, file_inode(file), file->f_flags, isdir);
if (!IS_ERR(ff))
file->private_data = ff;
-
return PTR_ERR_OR_ZERO(ff);
}
EXPORT_SYMBOL_GPL(fuse_do_open);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 86253517f59b..98af019037c3 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -924,6 +924,9 @@ struct fuse_conn {
/* Use io_uring for communication */
unsigned int io_uring;
+ /* Does the filesystem support compound operations? */
+ unsigned int compound_open_getattr:1;
+
/** Maximum stack depth for passthrough backing files */
int max_stack_depth;
@@ -1557,7 +1560,8 @@ void fuse_file_io_release(struct fuse_file *ff, struct inode *inode);
/* file.c */
struct fuse_file *fuse_file_open(struct fuse_mount *fm, u64 nodeid,
- unsigned int open_flags, bool isdir);
+ struct inode *inode,
+ unsigned int open_flags, bool isdir);
void fuse_file_release(struct inode *inode, struct fuse_file *ff,
unsigned int open_flags, fl_owner_t id, bool isdir);
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 819e50d66622..a5fd721be96d 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -991,6 +991,12 @@ void fuse_conn_init(struct fuse_conn *fc, struct fuse_mount *fm,
fc->blocked = 0;
fc->initialized = 0;
fc->connected = 1;
+
+ /* pretend fuse server supports compound operations
+ * until it tells us otherwise.
+ */
+ fc->compound_open_getattr = 1;
+
atomic64_set(&fc->attr_version, 1);
atomic64_set(&fc->evict_ctr, 1);
get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key));
diff --git a/fs/fuse/ioctl.c b/fs/fuse/ioctl.c
index fdc175e93f74..07a02e47b2c3 100644
--- a/fs/fuse/ioctl.c
+++ b/fs/fuse/ioctl.c
@@ -494,7 +494,7 @@ static struct fuse_file *fuse_priv_ioctl_prepare(struct inode *inode)
if (!S_ISREG(inode->i_mode) && !isdir)
return ERR_PTR(-ENOTTY);
- return fuse_file_open(fm, get_node_id(inode), O_RDONLY, isdir);
+ return fuse_file_open(fm, get_node_id(inode), NULL, O_RDONLY, isdir);
}
static void fuse_priv_ioctl_cleanup(struct inode *inode, struct fuse_file *ff)
--
2.51.0
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