NO-UPSTREAM: 9P: always use cached inode to fill in v9fs_vfs_getattr

Cherry-pick from kata-container patches:
https://github.com/kata-containers/packaging/tree/master/kernel/patches/0001-NO-UPSTREAM-9P-always-use-cached-inode-to-fill-in-v9.patch

So that if in cache=none mode, we don't have to lookup server that
might not support open-unlink-fstat operation.

fixes https://github.com/01org/cc-oci-runtime/issues/47
fixes https://github.com/01org/cc-oci-runtime/issues/1062Signed-off-by: NJulio Montes <julio.montes@intel.com>
Signed-off-by: NPeng Tao <bergwolf@gmail.com>
Signed-off-by: NEryu Guan <eguan@linux.alibaba.com>
Reviewed-by: NJiufei Xue <jiufei.xue@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

fs/9p/vfs_inode.c

@@ -1080,7 +1080,7 @@ v9fs_vfs_getattr(const struct path *path, struct kstat *stat,
 
 	p9_debug(P9_DEBUG_VFS, "dentry: %p\n", dentry);
 	v9ses = v9fs_dentry2v9ses(dentry);
-	if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) {
+	if (!d_really_is_negative(dentry) || v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) {
 		generic_fillattr(d_inode(dentry), stat);
 		return 0;
 	}

fs/9p/vfs_inode_dotl.c

@@ -480,7 +480,7 @@ v9fs_vfs_getattr_dotl(const struct path *path, struct kstat *stat,
 
 	p9_debug(P9_DEBUG_VFS, "dentry: %p\n", dentry);
 	v9ses = v9fs_dentry2v9ses(dentry);
-	if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) {
+	if (!d_really_is_negative(dentry) || v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) {
 		generic_fillattr(d_inode(dentry), stat);
 		return 0;
 	}