Date: Thu, 16 Feb 2012 12:09:00 -0600
From: Malahal Naineni <malahal@us.ibm.com>
To: linux-nfs@vger.kernel.org
Subject: Re: [PATCH] Get normalized paths for comparing NFS export paths
Message-ID: <20120216180900.GA30224@us.ibm.com>
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 <20120203142945.GA31805@us.ibm.com>
 <4F2E620F.5090100@panasas.com>
 <20120207204401.GA31752@us.ibm.com>
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Any comments on the patch below?

Regards, Malahal.

Malahal Naineni [malahal@us.ibm.com] wrote:
> NFSv4 gladly accepts and mounts "hostname:path" instead of
> "hostname:/path". NFS also accepts other forms for pathname, but it
> doesn't use the exact pathname string used for generating /proc/mounts.
> This causes mount entry mistmatch between /etc/mtab and /proc/mounts
> files. The former will have the exact given pathname string but the
> latter will have a modified path name.
> 
> Signed-off-by: Malahal Naineni <malahal@us.ibm.com>
> ---
>  utils/mount/nfsumount.c |   94 +++++++++++++++++++++++++++++++++++++++++-----
>  1 files changed, 83 insertions(+), 11 deletions(-)
> 
> diff --git a/utils/mount/nfsumount.c b/utils/mount/nfsumount.c
> index 3538d88..54542a5 100644
> --- a/utils/mount/nfsumount.c
> +++ b/utils/mount/nfsumount.c
> @@ -139,6 +139,88 @@ static int del_mtab(const char *spec, const char *node)
>  	return EX_FILEIO;
>  }
> 
> +/* 
> + * Return normalized path.
> + *
> + * Resolve "." and ".." components. Replace multiple slashes with one
> + * slash. realpath is close but doesn't work for us as the path won't
> + * exist on the client.
> + *
> + * The return string must be freed by the caller.
> + */
> +static char *normpath(const char *path)
> +{
> +	const char *ptr, *next, *end;
> +	char *norm; /* result */
> +
> +	if (!path)
> +		return NULL;
> +
> +	norm = malloc(strlen(path)+1);
> +	if (!norm)
> +		return NULL;
> +		
> +	end = path+strlen(path);
> +	*norm = '\0'; /* Make it a NULL string */
> +	for (ptr = path; ptr < end; ptr = next+1) {
> +		next = strchr(ptr, '/');
> +		if (!next)
> +			next = end;
> +		int pclen = next - ptr; /* path component length */
> +		if (strncmp(ptr, ".", pclen) == 0)
> +			continue;
> +		if (strncmp(ptr, "..", pclen) == 0) {
> +			char *tmp = strrchr(norm, '/');
> +			if (tmp)
> +				*tmp = '\0';
> +			continue;
> +		}
> +
> +		/* Add the new component */
> +		strncat(norm, "/", 1);
> +		strncat(norm, ptr, pclen);
> +	}
> +
> +	/*
> +	 * If there was no component to copy, norm would be null.
> +	 * Return "/" in that case
> +	 */
> +	if (*norm == '\0')
> +		strcpy(norm, "/");
> +
> +	return norm;
> +}
> +
> +/*
> + * Detect if the given two entries refer to the same mount entry.
> + * Usually one entry is from /etc/mtab and the other is from
> + * /proc/mounts.
> + */
> +static int nfs_same_mount_entry(const struct mntentchn *mc1,
> +				const struct mntentchn *mc2)
> +{
> +	char *host1, *host2;
> +	char *path1, *path2;
> +	char *norm1, *norm2;
> +	int retval;
> +
> +	nfs_parse_devname(mc1->m.mnt_fsname, &host1, &path1);
> +	nfs_parse_devname(mc2->m.mnt_fsname, &host2, &path2);
> +	norm1 = normpath(path1);
> +	norm2 = normpath(path2);
> +
> +	retval = strcmp(host1, host2) == 0 && strcmp(norm1, norm2) == 0;
> +
> +	free(host1);
> +	free(host2);
> +	free(path1);
> +	free(path2);
> +	free(norm1);
> +	free(norm2);
> +
> +	return retval;
> +}
> +
>  /*
>   * Detect NFSv4 mounts.
>   *
> @@ -161,17 +243,7 @@ static int nfs_umount_is_vers4(const struct mntentchn *mc)
>  		goto not_found;
> 
>  	do {
> -		size_t nlen = strlen(pmc->m.mnt_fsname);
> -
> -		/*
> -		 * It's possible the mount location string in /proc/mounts
> -		 * ends with a '/'. In this case, if the entry came from
> -		 * /etc/mtab, it won't have the trailing '/' so deal with
> -		 * it.
> -		 */
> -		while (pmc->m.mnt_fsname[nlen - 1] == '/')
> -			nlen--;
> -		if (strncmp(pmc->m.mnt_fsname, mc->m.mnt_fsname, nlen) != 0)
> +		if (!nfs_same_mount_entry(pmc, mc))
>  			continue;
> 
>  		if (strcmp(pmc->m.mnt_type, "nfs4") == 0)
> -- 
> 1.7.8.3
> 
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