[PATCH v6 3/3] fuse: add an implementation of open+getattr

[Horst Birthelmer]

From: Horst Birthelmer <hbirthelmer@xxxxxxx>

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@xxxxxxx>
---
 fs/fuse/file.c   | 111 +++++++++++++++++++++++++++++++++++++++++++++++--------
 fs/fuse/fuse_i.h |   4 +-
 fs/fuse/ioctl.c  |   2 +-
 3 files changed, 99 insertions(+), 18 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index a408a9668abbb361e2c1e386ebab9dfcb0a7a573..daa95a640c311fc393241bdf727e00a2bc714f35 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -136,8 +136,71 @@ static void fuse_file_put(struct fuse_file *ff, bool sync)
 	}
 }
 
+static int fuse_compound_open_getattr(struct fuse_mount *fm, u64 nodeid,
+				      struct inode *inode, int flags, int opcode,
+				      struct fuse_file *ff,
+				      struct fuse_attr_out *outattrp,
+				      struct fuse_open_out *outopenp)
+{
+	struct fuse_conn *fc = fm->fc;
+	struct fuse_compound_req *compound;
+	struct fuse_args open_args = {};
+	struct fuse_args getattr_args = {};
+	struct fuse_open_in open_in = {};
+	struct fuse_getattr_in getattr_in = {};
+	int err;
+
+	compound = fuse_compound_alloc(fm, 2, FUSE_COMPOUND_SEPARABLE);
+	if (!compound)
+		return -ENOMEM;
+
+	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;
+
+	fuse_open_args_fill(&open_args, nodeid, opcode, &open_in, outopenp);
+
+	err = fuse_compound_add(compound, &open_args, NULL);
+	if (err)
+		goto out;
+
+	fuse_getattr_args_fill(&getattr_args, nodeid, &getattr_in, outattrp);
+
+	err = fuse_compound_add(compound, &getattr_args, NULL);
+	if (err)
+		goto out;
+
+	err = fuse_compound_send(compound);
+	if (err)
+		goto out;
+
+	err = fuse_compound_get_error(compound, 0);
+	if (err)
+		goto out;
+
+	ff->fh = outopenp->fh;
+	ff->open_flags = outopenp->open_flags;
+
+	err = fuse_compound_get_error(compound, 1);
+	if (err)
+		goto out;
+
+	fuse_change_attributes(inode, &outattrp->attr, NULL,
+			       ATTR_TIMEOUT(outattrp),
+			       fuse_get_attr_version(fc));
+
+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;
@@ -163,23 +226,40 @@ 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;
 
-		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 (inode) {
+			struct fuse_attr_out attr_outarg;
+
+			err = fuse_compound_open_getattr(fm, nodeid, inode,
+							 open_flags, opcode, ff,
+							 &attr_outarg, outargp);
+		}
+
+		if (err == -ENOSYS) {
+			err = fuse_send_open(fm, nodeid, open_flags, opcode,
+					     outargp);
+			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;
 			}
 		}
 	}
@@ -195,11 +275,10 @@ 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 ff8222b66c4f7b04c0671a980237a43871affd0a..40409a4ab016a061eea20afee76c8a7fe9c15adb 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1588,7 +1588,9 @@ 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/ioctl.c b/fs/fuse/ioctl.c
index fdc175e93f74743eb4d2e5a4bc688df1c62e64c4..07a02e47b2c3a68633d213675a8cc380a0cf31d8 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)

-- 
2.53.0