fs: fuse: add dev id to /dev/fuse fdinfo

This commit add fuse connection device id to
fdinfo of opened /dev/fuse files.

Related discussions can be found at links below.

Link: https://lore.kernel.org/all/CAJfpegvEYUgEbpATpQx8NqVR33Mv-VK96C+gbTag1CEUeBqvnA@mail.gmail.com/
Signed-off-by: Chen Linxuan <[email protected]>
Signed-off-by: Miklos Szeredi <[email protected]>

Author: black-desk

fs/fuse/dev.c

@@ -23,6 +23,7 @@
 #include <linux/swap.h>
 #include <linux/splice.h>
 #include <linux/sched.h>
+#include <linux/seq_file.h>
 
 #define CREATE_TRACE_POINTS
 #include "fuse_trace.h"
@@ -2618,6 +2619,17 @@ static long fuse_dev_ioctl(struct file *file, unsigned int cmd,
 	}
 }
 
+#ifdef CONFIG_PROC_FS
+static void fuse_dev_show_fdinfo(struct seq_file *seq, struct file *file)
+{
+	struct fuse_dev *fud = fuse_get_dev(file);
+	if (!fud)
+		return;
+
+	seq_printf(seq, "fuse_connection:\t%u\n", fud->fc->dev);
+}
+#endif
+
 const struct file_operations fuse_dev_operations = {
 	.owner		= THIS_MODULE,
 	.open		= fuse_dev_open,
@@ -2633,6 +2645,9 @@ const struct file_operations fuse_dev_operations = {
 #ifdef CONFIG_FUSE_IO_URING
 	.uring_cmd	= fuse_uring_cmd,
 #endif
+#ifdef CONFIG_PROC_FS
+	.show_fdinfo	= fuse_dev_show_fdinfo,
+#endif
 };
 EXPORT_SYMBOL_GPL(fuse_dev_operations);