[RFC PATCH 4/7] FUSE: Add the fuse_fsnotify_send_request to FUSE

Ioannis Angelakopoulos
2021-10-25T20:47:45Z

The function "fuse_fsnotify_send_request" is responsible for sending an
fsnotify FUSE request to the FUSE server (virtiofsd).

The request contains all the information that is stored within the
"fuse_notify_fsnotify_in" struct, i.e., the event mask for the inotify
watch, the action to be performed on the watch (create, modify or delete)
and the group identifier which is essentially the 64bit (fsnotify_group)
pointer that corresponds to one inotify instance created by a user space
process.

Since each group identifier is unique, the FUSE server can create an equal
number of inotify instances to the ones created by the user space
processes.

Signed-off-by: Ioannis Angelakopoulos <iangelak@redhat.com>
---
fs/fuse/dev.c | 37 +++++++++++++++++++++++++++++++++++++
fs/fuse/fuse_i.h | 3 +++
2 files changed, 40 insertions(+)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index dde341a6388a..89eea8abac4b 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1795,6 +1795,43 @@ static int fuse_notify(struct fuse_conn *fc, enum fuse_notify_code code,
}
}

+/* Send a request for a watch placement to the FUSE server */
+int fuse_fsnotify_send_request(struct inode *inode, uint32_t mask,
+ uint32_t action, uint64_t group)
+{
+ struct fuse_mount *fm = get_fuse_mount(inode);
+ struct fuse_notify_fsnotify_in inarg;
+ int err;
+ FUSE_ARGS(args);
+
+ /* The server does not support remote fsnotify events */
+ if (fm->fc->no_fsnotify)
+ return 0;
+
+ /*
+ * Send the mask the action (remove, add, modify) and the
+ * unique identifier that is the fsnotify group that is
+ * interested in the watch to the FUSE server
+ */
+ memset(&inarg, 0, sizeof(struct fuse_notify_fsnotify_in));
+ inarg.mask = mask;
+ inarg.action = action;
+ inarg.group = (uint64_t)group;
+
+ args.opcode = FUSE_FSNOTIFY;
+ args.nodeid = get_node_id(inode);
+ args.in_numargs = 1;
+ args.in_args[0].size = sizeof(struct fuse_notify_fsnotify_in);
+ args.in_args[0].value = &inarg;
+ args.out_numargs = 0;
+ args.force = true;
+
+ err = fuse_simple_request(fm, &args);
+
+ return err;
+}
+EXPORT_SYMBOL(fuse_fsnotify_send_request);
+
/* Look up request on processing list by unique ID */
static struct fuse_req *request_find(struct fuse_pqueue *fpq, u64 unique)
{
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index c3cebfb936d2..5c83c4535608 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1243,6 +1243,9 @@ struct posix_acl *fuse_get_acl(struct inode *inode, int type, bool rcu);
int fuse_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
struct posix_acl *acl, int type);

+int fuse_fsnotify_send_request(struct inode *inode, uint32_t mask,
+ uint32_t action, uint64_t group);
+
/* readdir.c */
int fuse_readdir(struct file *file, struct dir_context *ctx);

--
2.33.0