fuse: fuse: add time_gran to INIT_OUT

Allow userspace fs to specify time granularity.

This is needed because with writeback_cache mode the kernel is responsible
for generating mtime and ctime, but if the underlying filesystem doesn't
support nanosecond granularity then the cache will contain a different
value from the one stored on the filesystem resulting in a change of times
after a cache flush.

Make the default granularity 1s.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 5997e4940512..560eafcdd6a7 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -891,6 +891,11 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
                                 fc->async_dio = 1;
                         if (arg->flags & FUSE_WRITEBACK_CACHE)
                                 fc->writeback_cache = 1;
+                        if (arg->time_gran && arg->time_gran <= 1000000000)
+                                fc->sb->s_time_gran = arg->time_gran;
+                        else
+                                fc->sb->s_time_gran = 1000000000;
+
                 } else {
                         ra_pages = fc->max_read / PAGE_CACHE_SIZE;
                         fc->no_lock = 1;