From: Egor Chelak <egor.chelak@gmail.com>
Date: Fri, 6 Nov 2020 18:33:46 +0000 (+0200)
Subject: ul_copy_file: handle EAGAIN and EINTR
X-Git-Tag: v2.37-rc1~393^2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=212bde6cf7160422844daba5276c8a0d1412a937;p=thirdparty%2Futil-linux.git

ul_copy_file: handle EAGAIN and EINTR

I did this by implementing a function called sendfile_all() similar to
read_all()/write_all().

The manpage for sendfile doesn't mention EINTR, but I decided to check
it anyway, just in case.

Suggested-by: Karel Zak <kzak@redhat.com>
Reviewed-by: Sami Kerola <kerolasa@iki.fi>
Signed-off-by: Egor Chelak <egor.chelak@gmail.com>
---

diff --git a/include/all-io.h b/include/all-io.h
index 8ffa9cfb11..98745802c9 100644
--- a/include/all-io.h
+++ b/include/all-io.h
@@ -12,6 +12,10 @@
 #include <string.h>
 #include <unistd.h>
 #include <errno.h>
+#include <sys/types.h>
+#ifdef HAVE_SENDFILE
+#include <sys/sendfile.h>
+#endif
 
 #include "c.h"
 
@@ -78,4 +82,32 @@ static inline ssize_t read_all(int fd, char *buf, size_t count)
 	return c;
 }
 
+static inline ssize_t sendfile_all(int out, int in, off_t *off, size_t count)
+{
+#ifdef HAVE_SENDFILE
+	ssize_t ret;
+	ssize_t c = 0;
+	int tries = 0;
+	while (count) {
+		ret = sendfile(out, in, off, count);
+		if (ret < 0) {
+			if ((errno == EAGAIN || errno == EINTR) && (tries++ < 5)) {
+				xusleep(250000);
+				continue;
+			}
+			return c ? c : -1;
+		}
+		if (ret == 0)
+			return c;
+		tries = 0;
+		count -= ret;
+		c += ret;
+	}
+	return c;
+#else
+	errno = ENOSYS;
+	return -1;
+#endif
+}
+
 #endif /* UTIL_LINUX_ALL_IO_H */
diff --git a/lib/fileutils.c b/lib/fileutils.c
index 61304c77ea..a9c0e61c0f 100644
--- a/lib/fileutils.c
+++ b/lib/fileutils.c
@@ -11,9 +11,6 @@
 #include <unistd.h>
 #include <sys/time.h>
 #include <sys/resource.h>
-#ifdef HAVE_SENDFILE
-#include <sys/sendfile.h>
-#endif
 #include <string.h>
 
 #include "c.h"
@@ -275,21 +272,15 @@ int ul_copy_file(int from, int to)
 #ifdef HAVE_SENDFILE
 	struct stat st;
 	ssize_t nw;
-	off_t left;
 
 	if (fstat(from, &st) == -1)
 		return -1;
 	if (!S_ISREG(st.st_mode))
 		return copy_file_simple(from, to);
-	for (left = st.st_size; left != 0; left -= nw) {
-		if ((nw = sendfile(to, from, NULL, left)) < 0)
-			return copy_file_simple(from, to);
-		if (!nw)
-			return 0;
-	}
-	/* For extra robustness, treat st_size as advisory and ensure that we
-	 * actually get EOF. */
-	while ((nw = sendfile(to, from, NULL, 1024*1024)) != 0)
+	if (sendfile_all(to, from, NULL, st.st_size) < 0)
+		return copy_file_simple(from, to);
+	/* ensure we either get an EOF or an error */
+	while ((nw = sendfile_all(to, from, NULL, 16*1024*1024)) != 0)
 		if (nw < 0)
 			return copy_file_simple(from, to);
 	return 0;