linux-ext4 - [PATCH] logsave : Avoid unnecessary backgrounding of logsave in case of failures

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Message-ID: <ea11fea30810071044l6d8887e0udb52342f82412e4a@mail.gmail.com>
Date:	Tue, 7 Oct 2008 23:14:11 +0530
From:	"Manish Katiyar" <mkatiyar@...il.com>
To:	ext4 <linux-ext4@...r.kernel.org>, "Theodore Tso" <tytso@....edu>
Cc:	mkatiyar@...il.com
Subject: [PATCH] logsave : Avoid unnecessary backgrounding of logsave in case of failures

Hi Ted,

I am not sure why we wan't to background the logsave and keep retrying
opening the fd in case of failures. But there may be situations when
we
will never be able to succeed and thus create unnecessary process. For
example invoking it

/home/mkatiyar/sbin> ./logsave /testfile ls

as a normal user will never succeed. Below patch adds some of the
error conditions where we can just avoid it.

Signed-off-by : Manish Katiyar <mkatiyar@...il.com>

---
 misc/logsave.c |   19 +++++++++++++++++--
 1 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/misc/logsave.c b/misc/logsave.c
index f0011f8..77a0a16 100644
--- a/misc/logsave.c
+++ b/misc/logsave.c
@@ -203,6 +203,17 @@ static int copy_from_stdin(void)
 	return 0;
 }

+static void should_background(int err, int *nobackground) {
+	switch (err) {
+		case EPERM:
+		case EACCES:
+			*nobackground = err;
+			break;
+		default :
+			*nobackground = 0;
+	}
+	return ;
+}


 int main(int argc, char **argv)
@@ -211,7 +222,7 @@ int main(int argc, char **argv)
 	char	*outfn, **cpp;
 	int	openflags = O_CREAT|O_WRONLY|O_TRUNC;
 	int	send_flag = SEND_LOG;
-	int	do_stdin;
+	int	do_stdin, nobackground = 0;
 	time_t	t;

 	while ((c = getopt(argc, argv, "+asv")) != EOF) {
@@ -237,6 +248,8 @@ int main(int argc, char **argv)
 	argc -= optind;

 	outfd = open(outfn, openflags, 0644);
+	if (outfd < 0)
+		should_background(errno, &nobackground);
 	do_stdin = !strcmp(argv[0], "-");

 	send_output("Log of ", 0, send_flag);
@@ -263,7 +276,7 @@ int main(int argc, char **argv)
 	send_output(ctime(&t), 0, send_flag);
 	send_output("----------------\n", 0, send_flag);

-	if (outbuf) {
+	if (!nobackground) {
 		pid = fork();
 		if (pid < 0) {
 			perror("fork");
@@ -282,6 +295,8 @@ int main(int argc, char **argv)
 		}
 		write(outfd, outbuf, outbufsize);
 		free(outbuf);
+	} else {
+		printf("Unable to save log to %s : %s\n", outfn, strerror(nobackground));
 	}
 	close(outfd);

-- 
1.5.4.3


Thanks -
Manish
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