From: Michal Privoznik <mprivozn@redhat.com>
Date: Mon, 28 Feb 2022 12:26:14 +0000 (+0100)
Subject: lxc_fuse: Prefer fuse_file_info::direct_io over mount option
X-Git-Tag: v8.2.0-rc1~176
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3f2454ca0c9b033c070e865defe4134c0c209512;p=thirdparty%2Flibvirt.git

lxc_fuse: Prefer fuse_file_info::direct_io over mount option

When mounting a FUSE it is possible to bypass kernel cache by
specifying -odirect_io mount option. This is what we currently
do. However, FUSEv3 has a different approach - the open callback
(lxcProcOpen() in our case) can set direct_io member of
fuse_file_info struct. This results in the same behaviour, but
also works with both FUSEv1 and FUSEv3. The latter does not have
the mount option and uses per file approach.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---

diff --git a/src/lxc/lxc_fuse.c b/src/lxc/lxc_fuse.c
index b068d21cf4..73d3ab1015 100644
--- a/src/lxc/lxc_fuse.c
+++ b/src/lxc/lxc_fuse.c
@@ -117,6 +117,7 @@ lxcProcOpen(const char *path,
     if ((fi->flags & O_ACCMODE) != O_RDONLY)
         return -EACCES;
 
+    fi->direct_io = 1;
     return 0;
 }
 
@@ -329,7 +330,6 @@ lxcSetupFuse(struct virLXCFuse **f,
 
     /* process name is libvirt_lxc */
     if (fuse_opt_add_arg(&args, "libvirt_lxc") == -1 ||
-        fuse_opt_add_arg(&args, "-odirect_io") == -1 ||
         fuse_opt_add_arg(&args, "-oallow_other") == -1 ||
         fuse_opt_add_arg(&args, "-ofsname=libvirt") == -1)
         goto error;