[PATCH] fuse: Add filesystem attribute in sysfs control dir.

[Lepton Wu <ytht.net@gmail.com>]

With this, user space can have more control to just abort some kind of
fuse connections. Currently, in Android, it will write to abort file
to abort all fuse connections while in some cases, we'd like to keep
some fuse connections. This can help that.

Signed-off-by: Lepton Wu <ytht.net@gmail.com>
---
 fs/fuse/control.c | 31 ++++++++++++++++++++++++++++++-
 fs/fuse/fuse_i.h  |  2 +-
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/control.c b/fs/fuse/control.c
index c23f6f243ad42..85a56d2de50d5 100644
--- a/fs/fuse/control.c
+++ b/fs/fuse/control.c
@@ -64,6 +64,27 @@ static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
 	return simple_read_from_buffer(buf, len, ppos, tmp, size);
 }
 
+static ssize_t fuse_conn_file_system_read(struct file *file, char __user *buf,
+					  size_t len, loff_t *ppos)
+{
+	char tmp[32];
+	size_t size;
+
+	if (!*ppos) {
+		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
+
+		if (!fc)
+			return 0;
+		if (fc->sb && fc->sb->s_type)
+			file->private_data = (void *)fc->sb->s_type->name;
+		else
+			file->private_data = "(NULL)";
+		fuse_conn_put(fc);
+	}
+	size = sprintf(tmp, "%.30s\n", (char *)file->private_data);
+	return simple_read_from_buffer(buf, len, ppos, tmp, size);
+}
+
 static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
 				    size_t len, loff_t *ppos, unsigned val)
 {
@@ -217,6 +238,12 @@ static const struct file_operations fuse_conn_congestion_threshold_ops = {
 	.llseek = no_llseek,
 };
 
+static const struct file_operations fuse_conn_file_system_ops = {
+	.open = nonseekable_open,
+	.read = fuse_conn_file_system_read,
+	.llseek = no_llseek,
+};
+
 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
 					  struct fuse_conn *fc,
 					  const char *name,
@@ -285,7 +312,9 @@ int fuse_ctl_add_conn(struct fuse_conn *fc)
 				 1, NULL, &fuse_conn_max_background_ops) ||
 	    !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
 				 S_IFREG | 0600, 1, NULL,
-				 &fuse_conn_congestion_threshold_ops))
+				 &fuse_conn_congestion_threshold_ops) ||
+	    !fuse_ctl_add_dentry(parent, fc, "filesystem", S_IFREG | 0400, 1,
+				 NULL, &fuse_conn_file_system_ops))
 		goto err;
 
 	return 0;
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 740a8a7d7ae6f..59390ed37bbad 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -45,7 +45,7 @@
 #define FUSE_NAME_MAX 1024
 
 /** Number of dentries for each connection in the control filesystem */
-#define FUSE_CTL_NUM_DENTRIES 5
+#define FUSE_CTL_NUM_DENTRIES 6
 
 /** List of active connections */
 extern struct list_head fuse_conn_list;
-- 
2.28.0.163.g6104cc2f0b6-goog