Add max_read to fuse_conn_info

Eventually, this setting should be negotiated in the filesystem's init()
handler (like e.g. max_write). However, this requires corresponding
changes in the FUSE kernel module. In preparation for this (and to allow
a transition period) we already allow (and require) filesystems to set
the value in the init() handler in addition to the mount option.

The end-goal is tracked in issue #91.

4 files changed, 23 insertions, 0 deletions

diff --git a/lib/fuse_i.h b/lib/fuse_i.h
index 50962e3..ec29c4e 100644
--- a/lib/fuse_i.h
+++ b/lib/fuse_i.h
@@ -108,6 +108,7 @@ void fuse_chan_put(struct fuse_chan *ch);
 struct mount_opts *parse_mount_opts(struct fuse_args *args);
 void destroy_mount_opts(struct mount_opts *mo);
 void fuse_mount_version(void);
+unsigned get_max_read(struct mount_opts *o);
 void fuse_kern_unmount(const char *mountpoint, int fd);
 int fuse_kern_mount(const char *mountpoint, struct mount_opts *mo);
 
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index 45e9d32..8455669 100644
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -1916,6 +1916,14 @@ static void do_init(fuse_req_t req, fuse_ino_t nodeid, const void *inarg)
 	if (se->op.init)
 		se->op.init(se->userdata, &se->conn);
 
+	unsigned max_read_mo = get_max_read(se->mo);
+	if (se->conn.max_read != max_read_mo) {
+		fprintf(stderr, "fuse: error: init() and fuse_session_new() "
+			"requested different maximum read size (%u vs %u)\n",
+			se->conn.max_read, max_read_mo);
+		abort();
+	}
+
 	/* Always enable big writes, this is superseded
 	   by the max_write option */
 	outarg.flags |= FUSE_BIG_WRITES;
diff --git a/lib/mount.c b/lib/mount.c
index 051b424..bb13c30 100644
--- a/lib/mount.c
+++ b/lib/mount.c
@@ -73,6 +73,7 @@ struct mount_opts {
 	char *mtab_opts;
 	char *fusermount_opts;
 	char *kernel_opts;
+	unsigned max_read;
 };
 
 #define FUSE_MOUNT_OPT(t, p) { t, offsetof(struct mount_opts, p), 1 }
@@ -83,6 +84,7 @@ static const struct fuse_opt fuse_mount_opts[] = {
 	FUSE_MOUNT_OPT("blkdev",		blkdev),
 	FUSE_MOUNT_OPT("auto_unmount",		auto_unmount),
 	FUSE_MOUNT_OPT("fsname=%s",		fsname),
+	FUSE_MOUNT_OPT("max_read=%u",		max_read),
 	FUSE_MOUNT_OPT("subtype=%s",		subtype),
 	FUSE_OPT_KEY("allow_other",		KEY_KERN_OPT),
 	FUSE_OPT_KEY("allow_root",		KEY_ALLOW_ROOT),
@@ -157,6 +159,11 @@ static const struct mount_flags mount_flags[] = {
 	{NULL,	    0,		    0}
 };
 
+unsigned get_max_read(struct mount_opts *o)
+{
+	return o->max_read;
+}
+
 static void set_mount_flag(const char *s, int *flags)
 {
 	int i;
diff --git a/lib/mount_bsd.c b/lib/mount_bsd.c
index 9cf9dfa..8bff2cf 100644
--- a/lib/mount_bsd.c
+++ b/lib/mount_bsd.c
@@ -40,6 +40,7 @@ struct mount_opts {
 	int allow_other;
 	int allow_root;
 	char *kernel_opts;
+	unsigned max_read;
 };
 
 #define FUSE_DUAL_OPT_KEY(templ, key)				\
@@ -48,6 +49,7 @@ struct mount_opts {
 static const struct fuse_opt fuse_mount_opts[] = {
 	{ "allow_other", offsetof(struct mount_opts, allow_other), 1 },
 	{ "allow_root", offsetof(struct mount_opts, allow_root), 1 },
+	{ "max_read=%u", offsetof(struct mount_opts, max_read), 1 },
 	FUSE_OPT_KEY("allow_root",		KEY_ALLOW_ROOT),
 	FUSE_OPT_KEY("-r",			KEY_RO),
 	/* standard FreeBSD mount options */
@@ -98,6 +100,11 @@ void fuse_mount_version(void)
 	system(FUSERMOUNT_PROG " --version");
 }
 
+unsigned get_max_read(struct mount_opts *o)
+{
+	return o->max_read;
+}
+
 static int fuse_mount_opt_proc(void *data, const char *arg, int key,
 			       struct fuse_args *outargs)
 {