From 4b580522c11d4ab41ab9774e2ffde2516772cca9 Mon Sep 17 00:00:00 2001
From: Antonio SJ Musumeci <trapexit@spawn.link>
Date: Wed, 1 Oct 2025 08:39:22 -0500
Subject: [PATCH] Allow setting of passthrough max_stack_depth

---
 libfuse/lib/debug.cpp         | 16 +++++++++++++++-
 libfuse/lib/fuse_i.h          |  1 +
 libfuse/lib/fuse_lowlevel.cpp |  5 +++--
 src/config.hpp                |  1 +
 4 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/libfuse/lib/debug.cpp b/libfuse/lib/debug.cpp
index 0c8d99b5..b82bce98 100644
--- a/libfuse/lib/debug.cpp
+++ b/libfuse/lib/debug.cpp
@@ -861,11 +861,25 @@ fuse_syslog_fuse_init_out(const struct fuse_init_out *arg_)
   output = fmt::format("fuse_init_out:"
                        " major={};"
                        " minor={};"
+                       " max_readahead={};"
+                       " max_background={};"
+                       " congestion_threshold={};"
+                       " max_write={};"
+                       " time_gran={};"
                        " max_pages={};"
+                       " map_alignment={};"
+                       " max_stack_depth={};"
                        " flags=(",
                        arg_->major,
                        arg_->minor,
-                       arg_->max_pages);
+                       arg_->max_readahead,
+                       arg_->max_background,
+                       arg_->congestion_threshold,
+                       arg_->max_write,
+                       arg_->time_gran,
+                       arg_->max_pages,
+                       arg_->map_alignment,
+                       arg_->max_stack_depth);
 
   for(uint64_t i = 0; i < (sizeof(flags)*8); i++)
     {
diff --git a/libfuse/lib/fuse_i.h b/libfuse/lib/fuse_i.h
index e702971d..53a2dd52 100644
--- a/libfuse/lib/fuse_i.h
+++ b/libfuse/lib/fuse_i.h
@@ -69,6 +69,7 @@ struct fuse_ll
   int broken_splice_nonblock;
   uint64_t notify_ctr;
   struct fuse_notify_req notify_list;
+  int passthrough_max_stack_depth;
 };
 
 struct fuse_cmd
diff --git a/libfuse/lib/fuse_lowlevel.cpp b/libfuse/lib/fuse_lowlevel.cpp
index a7a8fdca..16000cb1 100644
--- a/libfuse/lib/fuse_lowlevel.cpp
+++ b/libfuse/lib/fuse_lowlevel.cpp
@@ -1117,7 +1117,7 @@ do_init(fuse_req_t             req,
         struct fuse_in_header *hdr_)
 {
   struct fuse_init_out outarg = {0};
-  struct fuse_init_in *arg = (struct fuse_init_in *) &hdr_[1];
+  struct fuse_init_in *arg = (struct fuse_init_in*)&hdr_[1];
   struct fuse_ll *f = req->f;
   size_t bufsize = fuse_chan_bufsize(req->ch);
   uint64_t inargflags;
@@ -1288,7 +1288,7 @@ do_init(fuse_req_t             req,
   if(f->conn.want & FUSE_CAP_PASSTHROUGH)
     {
       outargflags |= FUSE_PASSTHROUGH;
-      outarg.max_stack_depth = 2;
+      outarg.max_stack_depth = (f->passthrough_max_stack_depth + 1);
     }
 
   if(inargflags & FUSE_INIT_EXT)
@@ -1800,6 +1800,7 @@ enum {
 
 static const struct fuse_opt fuse_ll_opts[] =
   {
+    { "passthrough-max-stack-depth=%u", offsetof(struct fuse_ll, passthrough_max_stack_depth), 0 },
     { "debug", offsetof(struct fuse_ll, debug), 1 },
     { "-d", offsetof(struct fuse_ll, debug), 1 },
     { "max_readahead=%u", offsetof(struct fuse_ll, conn.max_readahead), 0 },
diff --git a/src/config.hpp b/src/config.hpp
index ceffd157..50300b57 100644
--- a/src/config.hpp
+++ b/src/config.hpp
@@ -124,6 +124,7 @@ public:
   NFSOpenHack    nfsopenhack;
   ConfigBOOL     nullrw;
   Passthrough    passthrough = Passthrough::ENUM::OFF;
+  ConfigINT      passthrough_depth = 1;
   ConfigBOOL     parallel_direct_writes;
   ConfigGetPid   pid;
   ConfigBOOL     posix_acl;