Re: [LTP] [PATCH] Fix tst_find_backing_dev when no initramfs

[Richard Palethorpe <rpalethorpe@suse.de>]

Hello,

Alessandro Carminati <alessandro.carminati@gmail.com> writes:

> mount_root() is the kernel function responsible for mounting the primary
> rootfs.
> A dynamic there, prevents the /dev/root device node in the not yet mounted
> files system. For this reason, in the embedded system that starts without
> an initramfs, or however a proper initscript, the /dev/root device appears
> into the mount table in the / line.
> The test tries to open this /dev/root and fails with a warning.
> This patch aims to fix this situation.

Thanks I probably would have hit this issue sooner or later.

>
> Signed-off-by: Alessandro Carminati <alessandro.carminati@gmail.com>
>
> typo fixes
> ---
>  lib/tst_device.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/lib/tst_device.c b/lib/tst_device.c
> index 8419b80c3..c3427eb31 100644
> --- a/lib/tst_device.c
> +++ b/lib/tst_device.c
> @@ -526,6 +526,8 @@ void tst_find_backing_dev(const char *path, char *dev)
>  	unsigned int dev_major, dev_minor, line_mjr, line_mnr;
>  	unsigned int len, best_match_len = 1;
>  	char mnt_point[PATH_MAX];
> +	char tmpbuf1[PATH_MAX];
> +	char tmpbuf2[PATH_MAX];

It would be more readable to use three buffers and give them meaningful names.

>  
>  	if (stat(path, &buf) < 0)
>  		tst_brkm(TWARN | TERRNO, NULL, "stat() failed");
> @@ -562,6 +564,24 @@ void tst_find_backing_dev(const char *path, char *dev)
>  	if (!*dev)
>  		tst_brkm(TBROK, NULL, "Cannot find block device for %s", path);
>  
> +	if (stat(dev, &buf) < 0) {

As there is no harm in calling stat twice; could just do

if (stat(dev, &buf) < 0) && strcmp("/dev/root", dev) == 0) {

Or even replace with strcmp with errno == ENOENT and use this as a
general fallback.

> +		if (strcmp("/dev/root", dev) != 0) {
> +			tst_brkm(TWARN | TERRNO, NULL, "stat(%s) failed", dev);
> +		} else {

Then remove this if statement

> +			sprintf(tmpbuf1, "/sys/dev/block/%d:%d/uevent",
> dev_major, dev_minor);
> +			file = SAFE_FOPEN(NULL, tmpbuf1, "r");
> +			while (fgets(line, sizeof(line), file)) {
> +				if (sscanf(line, "%[^=]=%s", tmpbuf1, tmpbuf2) != 2)
> +					continue;
> +				if (strcmp("DEVNAME", tmpbuf1) == 0) {
> +					sprintf(dev, "/dev/%s", tmpbuf2);
> +					break;
> +				}
> +			}
> +			SAFE_FCLOSE(NULL, file);
> +		}
> +	}
> +
>  	if (stat(dev, &buf) < 0)
>  		tst_brkm(TWARN | TERRNO, NULL, "stat(%s) failed", dev);
>  
> -- 
> 2.34.1


-- 
Thank you,
Richard.

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