From 95246ee9d7b8bf7f5f173cae211523dd9241ed1f Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bvanassche@acm.org>
Date: Mon, 9 Jul 2012 06:12:47 +0000
Subject: [PATCH] scstadmin: Make _syswrite() translate EBUSY into "writing
 failed"

_syswrite() callers check whether writing into an SCST sysfs attribute
succeeded by checking whether the value returned by this function is
defined(). Return undef (failed) instead of -1 (success) if syswrite()
returned error code EBUSY (found this through source reading). Return
$length instead of length($cmd) if the initial write triggered EAGAIN.
Remove a superfluous $bytes = undef statement. Eliminate the variable
$wait.


git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@4400 d57e44dd-8a1f-0410-8b47-8ef2f437770f
---
 .../scst-0.9.10/lib/SCST/SCST.pm              | 43 +++++++++----------
 1 file changed, 21 insertions(+), 22 deletions(-)

diff --git a/scstadmin/scstadmin.sysfs/scst-0.9.10/lib/SCST/SCST.pm b/scstadmin/scstadmin.sysfs/scst-0.9.10/lib/SCST/SCST.pm
index 5f0ff2e16..8c170b677 100644
--- a/scstadmin/scstadmin.sysfs/scst-0.9.10/lib/SCST/SCST.pm
+++ b/scstadmin/scstadmin.sysfs/scst-0.9.10/lib/SCST/SCST.pm
@@ -4855,6 +4855,8 @@ sub errorString {
 	return $string;
 }
 
+# Write the first $3 bytes of $2 into the SCST sysfs file $1. Return either
+# the number of bytes written or undef if writing failed.
 sub _syswrite {
 	my $io = shift;
 	my $cmd = shift;
@@ -4865,35 +4867,32 @@ sub _syswrite {
 
 	my $bytes = syswrite($io, $cmd, $length);
 
-	if (!defined($bytes) && defined($res_file)) {
-		if ($! == EAGAIN) {
-			my $res = new IO::File $res_file, O_RDONLY;
+	if (!defined($bytes) && defined($res_file) && $! == EAGAIN) {
+		my $res_io = new IO::File $res_file, O_RDONLY;
 
-			if (!$res) {
-				cluck("FATAL: Failed opening $res_file: $!");
-				return undef;
-			}
+		if (!$res_io) {
+			cluck("FATAL: Failed opening $res_file: $!");
+			return undef;
+		}
 
-			my $wait = TRUE;
-			my $result;
+		my $res_val;
 
-			while ($wait && (($now + $TIMEOUT) > time())) {
-				sysread($res, $result, 8);
-				$wait = FALSE if ($! != EAGAIN);
+		while (($now + $TIMEOUT) > time()) {
+			if (!defined(sysread($res_io, $res_val, 8)) &&
+			    $! == EAGAIN) {
 				sleep 1;
-			}
-
-			if ($wait) {
-				my $_cmd = $cmd; chomp $_cmd;
-				cluck("Timeout while waiting for command '$_cmd' to complete");
-				$bytes = undef;
 			} else {
-				$bytes = length($cmd) if ($result == 0);
+				last;
 			}
+		}
 
-			close $res;
-		} elsif ($! == EBUSY) {
-			return -1;
+		close $res_io;
+
+		if (!defined($res_val)) {
+			my $_cmd = $cmd; chomp $_cmd;
+			cluck("Timeout while waiting for command '$_cmd' to complete");
+		} elsif ($res_val == 0) {
+			$bytes = $length;
 		}
 	}