On 8/21/20 1:58 PM, Daniel P. Berrangé wrote: > On Fri, Aug 21, 2020 at 11:41:26AM +0800, Jiachen Zhang wrote: >> Due to the commit 65da4539803373ec4eec97ffc49ee90083e56efd, the O_DIRECT >> open flag of guest applications will be discarded by virtiofsd. While >> this behavior makes it consistent with the virtio-9p scheme when guest >> applications using direct I/O, we no longer have any chance to bypass >> the host page cache. >> >> Therefore, we add a flag 'allow_directio' to lo_data. If '-o no_directio' >> option is added, or none of '-o no_directio' or '-o allow_directio' is >> added, the 'allow_directio' will be set to 0, and virtiofsd discards >> O_DIRECT as before. If '-o allow_directio' is added to the stariting >> command-line, 'allow_directio' will be set to 1, so that the O_DIRECT >> flags will be retained and host page cache can be bypassed. >> >> Signed-off-by: Jiachen Zhang <zhangjiachen.jay...@bytedance.com> >> --- >> tools/virtiofsd/helper.c | 4 ++++ >> tools/virtiofsd/passthrough_ll.c | 20 ++++++++++++++------ >> 2 files changed, 18 insertions(+), 6 deletions(-) >> >> diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c >> index 3105b6c23a..534ff52c64 100644 >> --- a/tools/virtiofsd/helper.c >> +++ b/tools/virtiofsd/helper.c >> @@ -180,6 +180,10 @@ void fuse_cmdline_help(void) >> " (0 leaves rlimit unchanged)\n" >> " default: min(1000000, >> fs.file-max - 16384)\n" >> " if the current rlimit >> is lower\n" >> + " -o allow_directio|no_directio\n" >> + " retain/discard O_DIRECT flags >> passed down\n" >> + " to virtiofsd from guest >> applications.\n" >> + " default: no_directio\n" >> ); > > The standard naming convention from existing options is to use > $OPTNAME and no_$OPTNAME. > > IOW, don't use the "allow_" prefix. The options should be just > "directio" and "no_directio"
As we have 'max_idle_threads' (and not maxidlethreads), can we use 'direct_io' instead? > > Regards, > Daniel >
