From 1123e7b0efbe356dd193747aefebbf9345cb5758 Mon Sep 17 00:00:00 2001
From: Bill Zissimopoulos <billziss@navimatics.com>
Date: Tue, 8 May 2018 10:51:29 -0700
Subject: [PATCH] dll: fuse: optimize symlinks aways when readlink returns
 -ENOSYS

---
 src/dll/fuse/fuse.c    | 9 +++++++++
 src/dll/fuse/library.h | 3 ++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/dll/fuse/fuse.c b/src/dll/fuse/fuse.c
index b3b522f7..d742642d 100644
--- a/src/dll/fuse/fuse.c
+++ b/src/dll/fuse/fuse.c
@@ -376,6 +376,15 @@ static NTSTATUS fsp_fuse_svcstart(FSP_SERVICE *Service, ULONG argc, PWSTR *argv)
                     &f->VolumeParams.VolumeCreationTime);
         }
     }
+    if (0 != f->ops.readlink)
+    {
+        char buf[FSP_FSCTL_TRANSACT_PATH_SIZEMAX / sizeof(WCHAR)];
+        int err;
+
+        /* this should always fail with ENOSYS or EINVAL */
+        err = f->ops.readlink("/", buf, sizeof buf);
+        f->has_symlinks = -ENOSYS != err;
+    }
 
     /* the FSD does not currently limit these VolumeParams fields; do so here! */
     if (f->VolumeParams.SectorSize < FSP_FUSE_SECTORSIZE_MIN ||
diff --git a/src/dll/fuse/library.h b/src/dll/fuse/library.h
index 12474be7..96e7c962 100644
--- a/src/dll/fuse/library.h
+++ b/src/dll/fuse/library.h
@@ -29,7 +29,7 @@
 #define FSP_FUSE_CONTEXT_FROM_HDR(h)    \
     (struct fuse_context *)((PUINT8)(h) + sizeof(struct fsp_fuse_context_header))
 
-#define FSP_FUSE_HAS_SYMLINKS(f)        (0 != (f)->ops.readlink)
+#define FSP_FUSE_HAS_SYMLINKS(f)        ((f)->has_symlinks)
 
 struct fuse
 {
@@ -44,6 +44,7 @@ struct fuse
     void *data;
     unsigned conn_want;
     BOOLEAN fsinit;
+    BOOLEAN has_symlinks;
     UINT32 DebugLog;
     FSP_FILE_SYSTEM_OPERATION_GUARD_STRATEGY OpGuardStrategy;
     FSP_FSCTL_VOLUME_PARAMS VolumeParams;