From cef8c8b249023fb8129ae791e0998cbca771f96a Mon Sep 17 00:00:00 2001
From: yangyun50 <149988609+yangyun50@users.noreply.github.com>
Date: Tue, 4 Jun 2024 19:50:48 +0800
Subject: Add support for no_interrupt (#956)

The function fuse_session_process_buf_int() would do much things
for FUSE_INTERRUPT requests, even there are no FUSE_INTERRUPT requests:

1. check every non-FUSE_INTERRUPT request and add these requests to the
linked list(se->list) under a big lock(se->lock).
2. the function fuse_free_req() frees every request and remove them from
the linked list(se->list) under a bing lock(se->lock).

These operations are not meaningful when there are no FUSE_INTERRUPT requests,
and have a great impact on the performance of fuse filesystem because the big
lock for each request.

In some cases, FUSE_INTERRUPT requests are infrequent, even none at all.
Besides, the user-defined filesystem may do nothing for FUSE_INTERRUPT requests.

And the kernel side has the option "no_interrupt" in struct fuse_conn. This kernel option
can be enabled by return ENOSYS in libfuse for the reply of FUSE_INTERRUPT request.
But I don't find the code to enable the "no_interrupt" kernel option in libfuse.

So add the no_interrupt support, and when this operaion is enabled:
1. remove the useless locking operaions and list operations.
2. return ENOSYS for the reply of FUSE_INTERRUPT request to inform the kernel to disable
FUSE_INTERRUPT request.
---
 example/notify_inval_inode.c | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'example/notify_inval_inode.c')

diff --git a/example/notify_inval_inode.c b/example/notify_inval_inode.c
index c0b1112..de88c87 100644
--- a/example/notify_inval_inode.c
+++ b/example/notify_inval_inode.c
@@ -123,6 +123,13 @@ static int tfs_stat(fuse_ino_t ino, struct stat *stbuf) {
     return 0;
 }
 
+static void tfs_init(void *userdata, struct fuse_conn_info *conn) {
+	(void)userdata;
+
+	/* Disable the receiving and processing of FUSE_INTERRUPT requests */
+	conn->no_interrupt = 1;
+}
+
 static void tfs_destroy(void *userarg)
 {
     (void)userarg;
@@ -250,6 +257,7 @@ static void tfs_read(fuse_req_t req, fuse_ino_t ino, size_t size,
 }
 
 static const struct fuse_lowlevel_ops tfs_oper = {
+    .init       = tfs_init,
     .destroy    = tfs_destroy,
     .lookup	= tfs_lookup,
     .getattr	= tfs_getattr,
-- 
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