On Thu, Dec 12, 2019 at 04:38:56PM +0000, Dr. David Alan Gilbert (git) wrote: > From: Vivek Goyal <vgoyal@redhat.com> > > If an application wants to do direct IO and opens a file with O_DIRECT > in guest, that does not necessarily mean that we need to bypass page > cache on host as well. So reset this flag on host. > > If somebody needs to bypass page cache on host as well (and it is safe to > do so), we can add a knob in daemon later to control this behavior. > > I check virtio-9p and they do reset O_DIRECT flag. > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com> > --- > tools/virtiofsd/passthrough_ll.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Regards, Daniel
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index cf6b548eee..6b3d396b6f 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -1705,6 +1705,13 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name, goto out; } + /* + * O_DIRECT in guest should not necessarily mean bypassing page + * cache on host as well. If somebody needs that behavior, it + * probably should be a configuration knob in daemon. + */ + fi->flags &= ~O_DIRECT; + fd = openat(parent_inode->fd, name, (fi->flags | O_CREAT) & ~O_NOFOLLOW, mode); err = fd == -1 ? errno : 0; @@ -1934,6 +1941,13 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) fi->flags &= ~O_APPEND; } + /* + * O_DIRECT in guest should not necessarily mean bypassing page + * cache on host as well. If somebody needs that behavior, it + * probably should be a configuration knob in daemon. + */ + fi->flags &= ~O_DIRECT; + sprintf(buf, "%i", lo_fd(req, ino)); fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW); if (fd == -1) {