fuse: fix LOOKUP vs INIT compat handling

Analysis from Marc:

 "Commit 7078187a ("fuse: introduce fuse_simple_request() helper")
  from the above pull request triggers some EIO errors for me in some tests
  that rely on fuse

  Looking at the code changes and a bit of debugging info I think there's a
  general problem here that fuse_get_req checks and possibly waits for
  fc->initialized, and this was always called first.  But this commit
  changes the ordering and in many places fc->minor is now possibly used
  before fuse_get_req, and we can't be sure that fc has been initialized.
  In my case fuse_lookup_init sets req->out.args[0].size to the wrong size
  because fc->minor at that point is still 0, leading to the EIO error."

Fix by moving the compat adjustments into fuse_simple_request() to after
fuse_get_req().

This is also more readable than the original, since now compatibility is
handled in a single function instead of cluttering each operation.
Reported-by: Marc Dionne <marc.c.dionne@gmail.com>
Tested-by: Marc Dionne <marc.c.dionne@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Fixes: 7078187a ("fuse: introduce fuse_simple_request() helper")

fs/fuse/dev.c

@@ -511,6 +511,39 @@ void fuse_request_send(struct fuse_conn *fc, struct fuse_req *req)
 }
 EXPORT_SYMBOL_GPL(fuse_request_send);
 
+static void fuse_adjust_compat(struct fuse_conn *fc, struct fuse_args *args)
+{
+	if (fc->minor < 4 && args->in.h.opcode == FUSE_STATFS)
+		args->out.args[0].size = FUSE_COMPAT_STATFS_SIZE;
+
+	if (fc->minor < 9) {
+		switch (args->in.h.opcode) {
+		case FUSE_LOOKUP:
+		case FUSE_CREATE:
+		case FUSE_MKNOD:
+		case FUSE_MKDIR:
+		case FUSE_SYMLINK:
+		case FUSE_LINK:
+			args->out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
+			break;
+		case FUSE_GETATTR:
+		case FUSE_SETATTR:
+			args->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
+			break;
+		}
+	}
+	if (fc->minor < 12) {
+		switch (args->in.h.opcode) {
+		case FUSE_CREATE:
+			args->in.args[0].size = sizeof(struct fuse_open_in);
+			break;
+		case FUSE_MKNOD:
+			args->in.args[0].size = FUSE_COMPAT_MKNOD_IN_SIZE;
+			break;
+		}
+	}
+}
+
 ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args)
 {
 	struct fuse_req *req;
@@ -520,6 +553,9 @@ ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args)
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
+	/* Needs to be done after fuse_get_req() so that fc->minor is valid */
+	fuse_adjust_compat(fc, args);
+
 	req->in.h.opcode = args->in.h.opcode;
 	req->in.h.nodeid = args->in.h.nodeid;
 	req->in.numargs = args->in.numargs;

fs/fuse/dir.c

@@ -156,10 +156,7 @@ static void fuse_lookup_init(struct fuse_conn *fc, struct fuse_args *args,
 	args->in.args[0].size = name->len + 1;
 	args->in.args[0].value = name->name;
 	args->out.numargs = 1;
-	if (fc->minor < 9)
-		args->out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
-	else
-		args->out.args[0].size = sizeof(struct fuse_entry_out);
+	args->out.args[0].size = sizeof(struct fuse_entry_out);
 	args->out.args[0].value = outarg;
 }
 
@@ -422,16 +419,12 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
 	args.in.h.opcode = FUSE_CREATE;
 	args.in.h.nodeid = get_node_id(dir);
 	args.in.numargs = 2;
-	args.in.args[0].size = fc->minor < 12 ? sizeof(struct fuse_open_in) :
-						sizeof(inarg);
+	args.in.args[0].size = sizeof(inarg);
 	args.in.args[0].value = &inarg;
 	args.in.args[1].size = entry->d_name.len + 1;
 	args.in.args[1].value = entry->d_name.name;
 	args.out.numargs = 2;
-	if (fc->minor < 9)
-		args.out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
-	else
-		args.out.args[0].size = sizeof(outentry);
+	args.out.args[0].size = sizeof(outentry);
 	args.out.args[0].value = &outentry;
 	args.out.args[1].size = sizeof(outopen);
 	args.out.args[1].value = &outopen;
@@ -539,10 +532,7 @@ static int create_new_entry(struct fuse_conn *fc, struct fuse_args *args,
 	memset(&outarg, 0, sizeof(outarg));
 	args->in.h.nodeid = get_node_id(dir);
 	args->out.numargs = 1;
-	if (fc->minor < 9)
-		args->out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
-	else
-		args->out.args[0].size = sizeof(outarg);
+	args->out.args[0].size = sizeof(outarg);
 	args->out.args[0].value = &outarg;
 	err = fuse_simple_request(fc, args);
 	if (err)
@@ -592,8 +582,7 @@ static int fuse_mknod(struct inode *dir, struct dentry *entry, umode_t mode,
 	inarg.umask = current_umask();
 	args.in.h.opcode = FUSE_MKNOD;
 	args.in.numargs = 2;
-	args.in.args[0].size = fc->minor < 12 ? FUSE_COMPAT_MKNOD_IN_SIZE :
-						sizeof(inarg);
+	args.in.args[0].size = sizeof(inarg);
 	args.in.args[0].value = &inarg;
 	args.in.args[1].size = entry->d_name.len + 1;
 	args.in.args[1].value = entry->d_name.name;
@@ -899,10 +888,7 @@ static int fuse_do_getattr(struct inode *inode, struct kstat *stat,
 	args.in.args[0].size = sizeof(inarg);
 	args.in.args[0].value = &inarg;
 	args.out.numargs = 1;
-	if (fc->minor < 9)
-		args.out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
-	else
-		args.out.args[0].size = sizeof(outarg);
+	args.out.args[0].size = sizeof(outarg);
 	args.out.args[0].value = &outarg;
 	err = fuse_simple_request(fc, &args);
 	if (!err) {
@@ -1574,10 +1560,7 @@ static void fuse_setattr_fill(struct fuse_conn *fc, struct fuse_args *args,
 	args->in.args[0].size = sizeof(*inarg_p);
 	args->in.args[0].value = inarg_p;
 	args->out.numargs = 1;
-	if (fc->minor < 9)
-		args->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
-	else
-		args->out.args[0].size = sizeof(*outarg_p);
+	args->out.args[0].size = sizeof(*outarg_p);
 	args->out.args[0].value = outarg_p;
 }
 

fs/fuse/inode.c

@@ -424,8 +424,7 @@ static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
 	args.in.h.opcode = FUSE_STATFS;
 	args.in.h.nodeid = get_node_id(dentry->d_inode);
 	args.out.numargs = 1;
-	args.out.args[0].size =
-		fc->minor < 4 ? FUSE_COMPAT_STATFS_SIZE : sizeof(outarg);
+	args.out.args[0].size = sizeof(outarg);
 	args.out.args[0].value = &outarg;
 	err = fuse_simple_request(fc, &args);
 	if (!err)