From e432c526261848120b3f66c46e06bd2a4265c9bb Mon Sep 17 00:00:00 2001
From: normal <normal@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Wed, 28 Nov 2018 00:35:22 +0000
Subject: [PATCH] io.c: reduce IO.copy_stream stack usage on Linux

nogvl_copy_file_range and nogvl_copy_stream_sendfile each
used 344 bytes of stack before this change.  Now, they are
inlined into nogvl_copy_stream_func which only uses 200 bytes
of stack.

"struct stat" is 144 bytes on my 64-bit Linux.

Note: this doesn't affect GC (yet) since GVL is released;
but increases safety if called from deep machine stacks.

It will affect GC if Thread::Light is merged.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66053 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 io.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/io.c b/io.c
index 3a2e5b081b..138153bf4a 100644
--- a/io.c
+++ b/io.c
@@ -10848,22 +10848,23 @@ simple_copy_file_range(int in_fd, off_t *in_offset, int out_fd, off_t *out_offse
 static int
 nogvl_copy_file_range(struct copy_stream_struct *stp)
 {
-    struct stat src_stat, dst_stat;
+    struct stat sb;
     ssize_t ss;
+    off_t src_size;
     int ret;
-
     off_t copy_length, src_offset, *src_offset_ptr;
 
-    ret = fstat(stp->src_fd, &src_stat);
+    ret = fstat(stp->src_fd, &sb);
     if (ret == -1) {
         stp->syserr = "fstat";
         stp->error_no = errno;
         return -1;
     }
-    if (!S_ISREG(src_stat.st_mode))
+    if (!S_ISREG(sb.st_mode))
         return 0;
 
-    ret = fstat(stp->dst_fd, &dst_stat);
+    src_size = sb.st_size;
+    ret = fstat(stp->dst_fd, &sb);
     if (ret == -1) {
         stp->syserr = "fstat";
         stp->error_no = errno;
@@ -10889,10 +10890,10 @@ nogvl_copy_file_range(struct copy_stream_struct *stp)
                 stp->error_no = errno;
                 return -1;
             }
-	    copy_length = src_stat.st_size - current_offset;
+	    copy_length = src_size - current_offset;
 	}
 	else {
-	    copy_length = src_stat.st_size - src_offset;
+	    copy_length = src_size - src_offset;
 	}
     }
 
@@ -11003,31 +11004,32 @@ simple_sendfile(int out_fd, int in_fd, off_t *offset, off_t count)
 static int
 nogvl_copy_stream_sendfile(struct copy_stream_struct *stp)
 {
-    struct stat src_stat, dst_stat;
+    struct stat sb;
     ssize_t ss;
     int ret;
-
+    off_t src_size;
     off_t copy_length;
     off_t src_offset;
     int use_pread;
 
-    ret = fstat(stp->src_fd, &src_stat);
+    ret = fstat(stp->src_fd, &sb);
     if (ret == -1) {
         stp->syserr = "fstat";
         stp->error_no = errno;
         return -1;
     }
-    if (!S_ISREG(src_stat.st_mode))
+    if (!S_ISREG(sb.st_mode))
         return 0;
 
-    ret = fstat(stp->dst_fd, &dst_stat);
+    src_size = sb.st_size;
+    ret = fstat(stp->dst_fd, &sb);
     if (ret == -1) {
         stp->syserr = "fstat";
         stp->error_no = errno;
         return -1;
     }
 #ifndef __linux__
-    if ((dst_stat.st_mode & S_IFMT) != S_IFSOCK)
+    if ((sb.st_mode & S_IFMT) != S_IFSOCK)
 	return 0;
 #endif
 
@@ -11037,7 +11039,7 @@ nogvl_copy_stream_sendfile(struct copy_stream_struct *stp)
     copy_length = stp->copy_length;
     if (copy_length == (off_t)-1) {
         if (use_pread)
-            copy_length = src_stat.st_size - src_offset;
+            copy_length = src_size - src_offset;
         else {
             off_t cur;
             errno = 0;
@@ -11047,7 +11049,7 @@ nogvl_copy_stream_sendfile(struct copy_stream_struct *stp)
                 stp->error_no = errno;
                 return -1;
             }
-            copy_length = src_stat.st_size - cur;
+            copy_length = src_size - cur;
         }
     }