Re: [PATCH 1/3] use_hostname_for_mounts shouldn't prevent selection among replicas

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On 29/01/18 15:19, NeilBrown wrote:
> If several replicas have been specified for a mount point,
> and use_hostname_for_mount is set to "yes", the selection
> between these replicas is currently disabled and the last in
> the list is always chosen.
> 
> There is little point selecting between different addresses
> for the one host in this case, but it is still worth
> selecting between different hosts, particularly if different
> weights have been specified.
> 
> This patch restores the "prune_host_list()" functionality
> when use_hostname_for_mount is set, and modifies it slightly
> so that only on IP address for any host:/path entry in the
> config file is willl be successfully probed.  After a
> success, further addresses from the same entry are skipped.
> This is achieved by tracking an entry number ("ent_num") for
> each 'struct host'.

Got it now.
Thanks Neil.

> 
> Signed-off-by: NeilBrown <neilb@xxxxxxxx>
> ---
>  include/replicated.h |    3 ++-
>  modules/mount_nfs.c  |    2 +-
>  modules/replicated.c |   35 ++++++++++++++++++++---------------
>  3 files changed, 23 insertions(+), 17 deletions(-)
> 
> diff --git a/include/replicated.h b/include/replicated.h
> index 69ab7800d96b..0f482d210066 100644
> --- a/include/replicated.h
> +++ b/include/replicated.h
> @@ -57,6 +57,7 @@
>  
>  struct host {
>  	char *name;
> +	int ent_num;
>  	struct sockaddr *addr;
>  	size_t addr_len;
>  	unsigned int rr;
> @@ -70,7 +71,7 @@ struct host {
>  };
>  
>  void seed_random(void);
> -struct host *new_host(const char *, struct sockaddr *, size_t,
> +struct host *new_host(const char *, int, struct sockaddr *, size_t,
>  		      unsigned int, unsigned int, unsigned int);
>  void free_host_list(struct host **);
>  int parse_location(unsigned, struct host **, const char *, unsigned int);
> diff --git a/modules/mount_nfs.c b/modules/mount_nfs.c
> index bf712a9374ca..304bef29eec7 100644
> --- a/modules/mount_nfs.c
> +++ b/modules/mount_nfs.c
> @@ -236,7 +236,7 @@ int mount_mount(struct autofs_point *ap, const char *root, const char *name, int
>  	    (vers & NFS4_VERS_MASK) != 0 &&
>  	    !(vers & UDP6_REQUESTED)) {
>  		unsigned int v4_probe_ok = 0;
> -		struct host *tmp = new_host(hosts->name,
> +		struct host *tmp = new_host(hosts->name, 0,
>  					    hosts->addr, hosts->addr_len,
>  					    hosts->proximity,
>  					    hosts->weight, hosts->options);
> diff --git a/modules/replicated.c b/modules/replicated.c
> index 3ac4c70f4062..c10efcd91deb 100644
> --- a/modules/replicated.c
> +++ b/modules/replicated.c
> @@ -83,7 +83,7 @@ void seed_random(void)
>  	return;
>  }
>  
> -struct host *new_host(const char *name,
> +struct host *new_host(const char *name, int ent_num,
>  		      struct sockaddr *addr, size_t addr_len,
>  		      unsigned int proximity, unsigned int weight,
>  		      unsigned int options)
> @@ -116,6 +116,7 @@ struct host *new_host(const char *name,
>  	memset(new, 0, sizeof(struct host));
>  
>  	new->name = tmp1;
> +	new->ent_num = ent_num;
>  	new->addr_len = addr_len;
>  	new->addr = tmp2;
>  	new->proximity = proximity;
> @@ -714,7 +715,7 @@ done:
>  int prune_host_list(unsigned logopt, struct host **list,
>  		    unsigned int vers, int port)
>  {
> -	struct host *this, *last, *first;
> +	struct host *this, *last, *first, *prev;
>  	struct host *new = NULL;
>  	unsigned int proximity, selected_version = 0;
>  	unsigned int v2_tcp_count, v3_tcp_count, v4_tcp_count;
> @@ -726,12 +727,6 @@ int prune_host_list(unsigned logopt, struct host **list,
>  	if (!*list)
>  		return 0;
>  
> -	/* If we're using the host name then there's no point probing
> -	 * avialability and respose time.
> -	 */
> -	if (defaults_use_hostname_for_mounts())
> -		return 1;
> -
>  	/* Use closest hosts to choose NFS version */
>  
>  	first = *list;
> @@ -877,11 +872,18 @@ int prune_host_list(unsigned logopt, struct host **list,
>  
>  	first = last;
>  	this = first;
> +	prev = NULL;
>  	while (this) {
>  		struct host *next = this->next;
>  		if (!this->name) {
>  			remove_host(list, this);
>  			add_host(&new, this);
> +		} else if (defaults_use_hostname_for_mounts() && prev &&
> +			   prev->ent_num == this->ent_num) {
> +			/* When we use the hostname to mount, there is no
> +			 * point in probing every address it has, just one is
> +			 * enough.  Skip the rest.
> +			 */
>  		} else {
>  			status = get_supported_ver_and_cost(logopt, this,
>  						selected_version, port);
> @@ -889,6 +891,7 @@ int prune_host_list(unsigned logopt, struct host **list,
>  				this->version = selected_version;
>  				remove_host(list, this);
>  				add_host(&new, this);
> +				prev = this;
>  			}
>  		}
>  		this = next;
> @@ -901,7 +904,7 @@ int prune_host_list(unsigned logopt, struct host **list,
>  }
>  
>  static int add_new_host(struct host **list,
> -			const char *host, unsigned int weight,
> +			const char *host, int ent_num, unsigned int weight,
>  			struct addrinfo *host_addr,
>  			unsigned int rr, unsigned int options)
>  {
> @@ -940,7 +943,7 @@ static int add_new_host(struct host **list,
>  	else
>  		return 0;
>  
> -	new = new_host(host, host_addr->ai_addr, addr_len, prx, weight, options);
> +	new = new_host(host, ent_num, host_addr->ai_addr, addr_len, prx, weight, options);
>  	if (!new)
>  		return 0;
>  
> @@ -953,7 +956,7 @@ static int add_new_host(struct host **list,
>  	return 1;
>  }
>  
> -static int add_host_addrs(struct host **list, const char *host,
> +static int add_host_addrs(struct host **list, const char *host, int ent_num,
>  			  unsigned int weight, unsigned int options)
>  {
>  	struct addrinfo hints, *ni, *this;
> @@ -988,7 +991,7 @@ static int add_host_addrs(struct host **list, const char *host,
>  
>  	this = ni;
>  	while (this) {
> -		ret = add_new_host(list, host, weight, this, 0, options);
> +		ret = add_new_host(list, host, ent_num, weight, this, 0, options);
>  		if (!ret)
>  			break;
>  		this = this->ai_next;
> @@ -1027,7 +1030,7 @@ try_name:
>  		rr++;
>  	this = ni;
>  	while (this) {
> -		ret = add_new_host(list, host, weight, this, rr, options);
> +		ret = add_new_host(list, host, ent_num, weight, this, rr, options);
>  		if (!ret)
>  			break;
>  		this = this->ai_next;
> @@ -1120,6 +1123,7 @@ int parse_location(unsigned logopt, struct host **hosts,
>  {
>  	char *str, *p, *delim;
>  	unsigned int empty = 1;
> +	int ent_num = 1;
>  
>  	if (!list)
>  		return 0;
> @@ -1177,7 +1181,7 @@ int parse_location(unsigned logopt, struct host **hosts,
>  				}
>  
>  				if (p != delim) {
> -					if (!add_host_addrs(hosts, p, weight, options)) {
> +					if (!add_host_addrs(hosts, p, ent_num, weight, options)) {
>  						if (empty) {
>  							p = next;
>  							continue;
> @@ -1199,7 +1203,7 @@ int parse_location(unsigned logopt, struct host **hosts,
>  				*delim = '\0';
>  				next = delim + 1;
>  
> -				if (!add_host_addrs(hosts, p, weight, options)) {
> +				if (!add_host_addrs(hosts, p, ent_num, weight, options)) {
>  					p = next;
>  					continue;
>  				}
> @@ -1213,6 +1217,7 @@ int parse_location(unsigned logopt, struct host **hosts,
>  			return 0;
>  		}
>  
> +		ent_num ++;
>  		p = next;
>  	}
>  
> 
> 

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