[PATCH] test-container: Use xcopy_file_range for cross-device copy [BZ #23597]

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Fri, Aug 31, 2018 at 9:23 AM, Carlos O'Donell <carlos@redhat.com> wrote:
>>
>> That is what io/copy_file_range-compat.c does.  Are you suggesting
>> cut and paste, instead of #include?
>
> Not quite.
>
> We are suggesting a unique and simplified copy of those sources to
> be placed into the support/ directory as a *.c file that can be
> used for support purposes.
>
> Coupling support behaviour and runtime behaviour is a bad choice,
> so we should not do it. Even if it means some code duplication.
>

Like this?

-- 
H.J.

From f08d598bcc973c4747d6baa1a832d683f2c917a8 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Fri, 31 Aug 2018 11:26:16 -0700
Subject: [PATCH] test-container: Use xcopy_file_range for cross-device copy
 [BZ #23597]

copy_file_range can't be used to copy a file from glibc source directory
to glibc build directory since they may be on different filesystems.
This patch adds xcopy_file_range to use it for cross-device copy.

	[BZ #23597]
	* support/Makefile (libsupport-routines): Add xcopy_file_range.
	* support/test-container.c (copy_one_file): Call xcopy_file_rang
	instead of copy_file_range.
	* support/xcopy_file_range.c: New file.  Copied and modified
	from io/copy_file_range-compat.c.
	* support/xunistd.h (xcopy_file_range): New prototype.
---
 support/Makefile           |   1 +
 support/test-container.c   |   2 +-
 support/xcopy_file_range.c | 142 +++++++++++++++++++++++++++++++++++++
 support/xunistd.h          |   3 +
 4 files changed, 147 insertions(+), 1 deletion(-)
 create mode 100644 support/xcopy_file_range.c

diff --git a/support/Makefile b/support/Makefile
index b528f538a6..7758465bb7 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -74,6 +74,7 @@ libsupport-routines = \
   xchroot \
   xclose \
   xconnect \
+  xcopy_file_range \
   xdlfcn \
   xdup2 \
   xfclose \
diff --git a/support/test-container.c b/support/test-container.c
index 2e91bdf9ec..476a5574e6 100644
--- a/support/test-container.c
+++ b/support/test-container.c
@@ -383,7 +383,7 @@ copy_one_file (const char *sname, const char *dname)
   if (dfd < 0)
     FAIL_EXIT1 ("unable to open %s for writing\n", dname);
 
-  if (copy_file_range (sfd, 0, dfd, 0, st.st_size, 0) != st.st_size)
+  if (xcopy_file_range (sfd, 0, dfd, 0, st.st_size, 0) != st.st_size)
     FAIL_EXIT1 ("cannot copy file %s to %s\n", sname, dname);
 
   xclose (sfd);
diff --git a/support/xcopy_file_range.c b/support/xcopy_file_range.c
new file mode 100644
index 0000000000..e6ba141eee
--- /dev/null
+++ b/support/xcopy_file_range.c
@@ -0,0 +1,142 @@
+/* Simplified copy_file_range with cross-device copy
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+ssize_t
+xcopy_file_range (int infd, __off64_t *pinoff,
+		  int outfd, __off64_t *poutoff,
+		  size_t length, unsigned int flags)
+{
+  if (flags != 0)
+    {
+      errno = EINVAL;
+      return -1;
+    }
+
+  struct stat64 instat;
+  struct stat64 outstat;
+  if (fstat64 (infd, &instat) != 0 || fstat64 (outfd, &outstat) != 0)
+    return -1;
+  if (S_ISDIR (instat.st_mode) || S_ISDIR (outstat.st_mode))
+    {
+      errno = EISDIR;
+      return -1;
+    }
+  if (!S_ISREG (instat.st_mode) || !S_ISREG (outstat.st_mode))
+    {
+      /* We need a regular input file so that the we can seek
+	 backwards in case of a write failure.  */
+      errno = EINVAL;
+      return -1;
+    }
+
+  /* The output descriptor must not have O_APPEND set.  */
+  if (fcntl (outfd, F_GETFL) & O_APPEND)
+    {
+      errno = EBADF;
+      return -1;
+    }
+
+  /* Avoid an overflow in the result.  */
+  if (length > SSIZE_MAX)
+    length = SSIZE_MAX;
+
+  /* Main copying loop.  The buffer size is arbitrary and is a
+     trade-off between stack size consumption, cache usage, and
+     amortization of system call overhead.  */
+  size_t copied = 0;
+  char buf[8192];
+  while (length > 0)
+    {
+      size_t to_read = length;
+      if (to_read > sizeof (buf))
+	to_read = sizeof (buf);
+
+      /* Fill the buffer.  */
+      ssize_t read_count;
+      if (pinoff == NULL)
+	read_count = read (infd, buf, to_read);
+      else
+	read_count = pread64 (infd, buf, to_read, *pinoff);
+      if (read_count == 0)
+	/* End of file reached prematurely.  */
+	return copied;
+      if (read_count < 0)
+	{
+	  if (copied > 0)
+	    /* Report the number of bytes copied so far.  */
+	    return copied;
+	  return -1;
+	}
+      if (pinoff != NULL)
+	*pinoff += read_count;
+
+      /* Write the buffer part which was read to the destination.  */
+      char *end = buf + read_count;
+      for (char *p = buf; p < end; )
+	{
+	  ssize_t write_count;
+	  if (poutoff == NULL)
+	    write_count = write (outfd, p, end - p);
+	  else
+	    write_count = pwrite64 (outfd, p, end - p, *poutoff);
+	  if (write_count < 0)
+	    {
+	      /* Adjust the input read position to match what we have
+		 written, so that the caller can pick up after the
+		 error.  */
+	      size_t written = p - buf;
+	      /* NB: This needs to be signed so that we can form the
+		 negative value below.  */
+	      ssize_t overread = read_count - written;
+	      if (pinoff == NULL)
+		{
+		  if (overread > 0)
+		    {
+		      /* We are on an error recovery path, so we
+			 cannot deal with failure here.  */
+		      int save_errno = errno;
+		      (void) lseek64 (infd, -overread, SEEK_CUR);
+		      errno = save_errno;
+		    }
+		}
+	      else /* pinoff != NULL */
+		*pinoff -= overread;
+
+	      if (copied + written > 0)
+		/* Report the number of bytes copied so far.  */
+		return copied + written;
+	      return -1;
+	    }
+	  p += write_count;
+	  if (poutoff != NULL)
+	    *poutoff += write_count;
+	} /* Write loop.  */
+
+      copied += read_count;
+      length -= read_count;
+    }
+  return copied;
+}
diff --git a/support/xunistd.h b/support/xunistd.h
index cdd4e8d92d..f99f362cb4 100644
--- a/support/xunistd.h
+++ b/support/xunistd.h
@@ -64,6 +64,9 @@ void *xmmap (void *addr, size_t length, int prot, int flags, int fd);
 void xmprotect (void *addr, size_t length, int prot);
 void xmunmap (void *addr, size_t length);
 
+ssize_t xcopy_file_range(int fd_in, loff_t *off_in, int fd_out,
+			 loff_t *off_out, size_t len, unsigned int flags);
+
 __END_DECLS
 
 #endif /* SUPPORT_XUNISTD_H */
-- 
2.17.1