[PATCH] selftests/mount: Close 'fd' when write fails

[PATCH] selftests/mount: Close 'fd' when write fails

[ritvikfoss]

From: Ritvik Gupta <ritvikfoss@gmail.com>

1. Close the file descriptor when write fails.
2. Introduce 'close_or_die' helper function to
reduce repetition.

Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>
---
 .../selftests/mount/unprivileged-remount-test.c     | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/mount/unprivileged-remount-test.c b/tools/testing/selftests/mount/unprivileged-remount-test.c
index d2917054fe3a..3dd9df58725b 100644
--- a/tools/testing/selftests/mount/unprivileged-remount-test.c
+++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
@@ -54,6 +54,13 @@ static void die(char *fmt, ...)
 	exit(EXIT_FAILURE);
 }
 
+static void close_or_die(char *filename, int fd) {
+	if (close(fd) != 0) {
+		die("close of %s failed: %s\n",
+		filename, strerror(errno));
+	}
+}
+
 static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
 {
 	char buf[4096];
@@ -79,6 +86,7 @@ static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list
 	}
 	written = write(fd, buf, buf_len);
 	if (written != buf_len) {
+		close_or_die(filename, fd);
 		if (written >= 0) {
 			die("short write to %s\n", filename);
 		} else {
@@ -86,10 +94,7 @@ static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list
 				filename, strerror(errno));
 		}
 	}
-	if (close(fd) != 0) {
-		die("close of %s failed: %s\n",
-			filename, strerror(errno));
-	}
+	close_or_die(filename, fd);
 }
 
 static void maybe_write_file(char *filename, char *fmt, ...)
-- 
2.48.1

[PATCH v2] selftests/mount: Close 'fd' when write fails

[ritvikfoss]

From: Ritvik Gupta <ritvikfoss@gmail.com>

1. Close the file descriptor when write fails.
2. Introduce 'close_or_die' helper function to
reduce repetition.

Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>
---
Changes in v2:
    - Fixed formatting

 .../selftests/mount/unprivileged-remount-test.c    | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/mount/unprivileged-remount-test.c b/tools/testing/selftests/mount/unprivileged-remount-test.c
index d2917054fe3a..41d7547c781d 100644
--- a/tools/testing/selftests/mount/unprivileged-remount-test.c
+++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
@@ -54,6 +54,14 @@ static void die(char *fmt, ...)
 	exit(EXIT_FAILURE);
 }
 
+static void close_or_die(char *filename, int fd)
+{
+	if (close(fd) != 0) {
+		die("close of %s failed: %s\n",
+		filename, strerror(errno));
+	}
+}
+
 static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
 {
 	char buf[4096];
@@ -79,6 +87,7 @@ static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list
 	}
 	written = write(fd, buf, buf_len);
 	if (written != buf_len) {
+		close_or_die(filename, fd);
 		if (written >= 0) {
 			die("short write to %s\n", filename);
 		} else {
@@ -86,10 +95,7 @@ static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list
 				filename, strerror(errno));
 		}
 	}
-	if (close(fd) != 0) {
-		die("close of %s failed: %s\n",
-			filename, strerror(errno));
-	}
+	close_or_die(filename, fd);
 }
 
 static void maybe_write_file(char *filename, char *fmt, ...)
-- 
2.48.1

Re: [PATCH v2] selftests/mount: Close 'fd' when write fails

[Seyediman Seyedarab]

On 25/02/22 05:42PM, ritvikfoss@gmail.com wrote:
> From: Ritvik Gupta <ritvikfoss@gmail.com>
> 
> 1. Close the file descriptor when write fails.
> 2. Introduce 'close_or_die' helper function to
> reduce repetition.
> 
> Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>
> ---
> Changes in v2:
>     - Fixed formatting
> 
>  .../selftests/mount/unprivileged-remount-test.c    | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/mount/unprivileged-remount-test.c b/tools/testing/selftests/mount/unprivileged-remount-test.c
> index d2917054fe3a..41d7547c781d 100644
> --- a/tools/testing/selftests/mount/unprivileged-remount-test.c
> +++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
> @@ -54,6 +54,14 @@ static void die(char *fmt, ...)
>  	exit(EXIT_FAILURE);
>  }
>  
> +static void close_or_die(char *filename, int fd)
> +{
> +	if (close(fd) != 0) {
> +		die("close of %s failed: %s\n",
> +		filename, strerror(errno));
> +	}
> +}
> +
>  static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
>  {
>  	char buf[4096];
> @@ -79,6 +87,7 @@ static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list
>  	}
>  	written = write(fd, buf, buf_len);
>  	if (written != buf_len) {
> +		close_or_die(filename, fd);
>  		if (written >= 0) {
>  			die("short write to %s\n", filename);
>  		} else {
> @@ -86,10 +95,7 @@ static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list
>  				filename, strerror(errno));
>  		}
>  	}
> -	if (close(fd) != 0) {
> -		die("close of %s failed: %s\n",
> -			filename, strerror(errno));
> -	}
> +	close_or_die(filename, fd);
>  }
>  
>  static void maybe_write_file(char *filename, char *fmt, ...)
> -- 
> 2.48.1
> 
> 

Closing a file right before a process exits is redundant,
since the kernel will clean it up automatically anyway.
That said, whether doing this as a best practice is arguable.

Cheers,
Seyediman

Re: [PATCH v2] selftests/mount: Close 'fd' when write fails

[Ritvik Gupta]

Yes, the kernel will handle the 'fd' cleanup automatically, but
the existing implementation already closes it before exiting.
However, in case where write fails, its unhandled.
This patch addresses that gap :)

Nevertheless it's subjective indeed.
Thanks for reviewing!

Regards
Ritvik

Re: [PATCH v2] selftests/mount: Close 'fd' when write fails

[Seyediman Seyedarab]

On 25/02/23 09:51AM, Ritvik Gupta wrote:
> Yes, the kernel will handle the 'fd' cleanup automatically, but
> the existing implementation already closes it before exiting.
> However, in case where write fails, its unhandled.
> This patch addresses that gap :)
> 
> Nevertheless it's subjective indeed.
> Thanks for reviewing!
> 
> Regards
> Ritvik

The current implementation doesn't close the fd before calling
the die() function. It only closes fd before returning because
vmaybe_write_file() doesn't necessarily exit the process. It
only exits in failure cases, including failures when closing
the file itself. I think the close() failure path might have
caused some confusion.

Cheers,
Seyediman

Re: [PATCH v2] selftests/mount: Close 'fd' when write fails

[Ritvik Gupta]

> Yes, the kernel will handle the 'fd' cleanup automatically, but
> the existing implementation already closes it before exiting.
                                                       ^^^^^^^
Whoops! I meant 'returning' there.
Wording issue on my part :P

We're referring to the same thing!
Thanks for detailed response :)

Regards
Ritvik