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Revision 35991652baa12ff3d0e420c0d0cb2ad9f7076e5b authored by Mikulas Patocka on 02 June 2012, 23:29:58 UTC, committed by Alasdair G Kergon on 02 June 2012, 23:29:58 UTC 
dm mpath: allow ioctls to trigger pg init
 
After the failure of a group of paths, any alternative paths that
need initialising do not become available until further I/O is sent to
the device.  Until this has happened, ioctls return -EAGAIN.

With this patch, new paths are made available in response to an ioctl
too.  The processing of the ioctl gets delayed until this has happened.

Instead of returning an error, we submit a work item to kmultipathd
(that will potentially activate the new path) and retry in ten
milliseconds.

Note that the patch doesn't retry an ioctl if the ioctl itself fails due
to a path failure.  Such retries should be handled intelligently by the
code that generated the ioctl in the first place, noting that some SCSI
commands should not be retried because they are not idempotent (XOR write
commands).  For commands that could be retried, there is a danger that
if the device rejected the SCSI command, the path could be errorneously
marked as failed, and the request would be retried on another path which
might fail too.  It can be determined if the failure happens on the
device or on the SCSI controller, but there is no guarantee that all
SCSI drivers set these flags correctly.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
1 parent f220fd4
Raw File
sysctl_net.c 
/* -*- linux-c -*-
 * sysctl_net.c: sysctl interface to net subsystem.
 *
 * Begun April 1, 1996, Mike Shaver.
 * Added /proc/sys/net directories for each protocol family. [MS]
 *
 * Revision 1.2  1996/05/08  20:24:40  shaver
 * Added bits for NET_BRIDGE and the NET_IPV4_ARP stuff and
 * NET_IPV4_IP_FORWARD.
 *
 *
 */

#include <linux/mm.h>
#include <linux/export.h>
#include <linux/sysctl.h>
#include <linux/nsproxy.h>

#include <net/sock.h>

#ifdef CONFIG_INET
#include <net/ip.h>
#endif

#ifdef CONFIG_NET
#include <linux/if_ether.h>
#endif

#ifdef CONFIG_TR
#include <linux/if_tr.h>
#endif

static struct ctl_table_set *
net_ctl_header_lookup(struct ctl_table_root *root, struct nsproxy *namespaces)
{
	return &namespaces->net_ns->sysctls;
}

static int is_seen(struct ctl_table_set *set)
{
	return &current->nsproxy->net_ns->sysctls == set;
}

/* Return standard mode bits for table entry. */
static int net_ctl_permissions(struct ctl_table_root *root,
			       struct nsproxy *nsproxy,
			       struct ctl_table *table)
{
	/* Allow network administrator to have same access as root. */
	if (capable(CAP_NET_ADMIN)) {
		int mode = (table->mode >> 6) & 7;
		return (mode << 6) | (mode << 3) | mode;
	}
	return table->mode;
}

static struct ctl_table_root net_sysctl_root = {
	.lookup = net_ctl_header_lookup,
	.permissions = net_ctl_permissions,
};

static int net_ctl_ro_header_perms(struct ctl_table_root *root,
		struct nsproxy *namespaces, struct ctl_table *table)
{
	if (net_eq(namespaces->net_ns, &init_net))
		return table->mode;
	else
		return table->mode & ~0222;
}

static struct ctl_table_root net_sysctl_ro_root = {
	.permissions = net_ctl_ro_header_perms,
};

static int __net_init sysctl_net_init(struct net *net)
{
	setup_sysctl_set(&net->sysctls, &net_sysctl_root, is_seen);
	return 0;
}

static void __net_exit sysctl_net_exit(struct net *net)
{
	retire_sysctl_set(&net->sysctls);
}

static struct pernet_operations sysctl_pernet_ops = {
	.init = sysctl_net_init,
	.exit = sysctl_net_exit,
};

static __init int net_sysctl_init(void)
{
	int ret;
	ret = register_pernet_subsys(&sysctl_pernet_ops);
	if (ret)
		goto out;
	setup_sysctl_set(&net_sysctl_ro_root.default_set, &net_sysctl_ro_root, NULL);
	register_sysctl_root(&net_sysctl_ro_root);
	register_sysctl_root(&net_sysctl_root);
out:
	return ret;
}
subsys_initcall(net_sysctl_init);

struct ctl_table_header *register_net_sysctl_table(struct net *net,
	const struct ctl_path *path, struct ctl_table *table)
{
	return __register_sysctl_paths(&net->sysctls, path, table);
}
EXPORT_SYMBOL_GPL(register_net_sysctl_table);

struct ctl_table_header *register_net_sysctl_rotable(const
		struct ctl_path *path, struct ctl_table *table)
{
	return __register_sysctl_paths(&net_sysctl_ro_root.default_set,
					path, table);
}
EXPORT_SYMBOL_GPL(register_net_sysctl_rotable);

void unregister_net_sysctl_table(struct ctl_table_header *header)
{
	unregister_sysctl_table(header);
}
EXPORT_SYMBOL_GPL(unregister_net_sysctl_table);
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