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netconsole: Attach cmdline target to dynamic target

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Enable the attachment of a dynamic target to the target created during
boot time. The boot-time targets are named as "cmdline\d", where "\d" is
a number starting at 0.

If the user creates a dynamic target named "cmdline0", it will attach to
the first target created at boot time (as defined in the
`netconsole=...` command line argument). `cmdline1` will attach to the
second target and so forth.

If there is no netconsole target created at boot time, then, the target
name could be reused.

Relevant design discussion:
https://lore.kernel.org/all/ZRWRal5bW93px4km@gmail.com/

Suggested-by: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20231012111401.333798-4-leitao@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Breno Leitao 2023-10-12 04:14:00 -07:00 committed by Jakub Kicinski
parent 131eeb45b9
commit 5fbd6cdbe3
1 changed files with 28 additions and 0 deletions
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28
drivers/net/netconsole.c
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@ -629,6 +629,23 @@ static const struct config_item_type netconsole_target_type = {
.ct_owner = THIS_MODULE,
};
static struct netconsole_target *find_cmdline_target(const char *name)
{
struct netconsole_target *nt, *ret = NULL;
unsigned long flags;
spin_lock_irqsave(&target_list_lock, flags);
list_for_each_entry(nt, &target_list, list) {
if (!strcmp(nt->item.ci_name, name)) {
ret = nt;
break;
}
}
spin_unlock_irqrestore(&target_list_lock, flags);
return ret;
}
/*
* Group operations and type for netconsole_subsys.
*/
@ -639,6 +656,17 @@ static struct config_item *make_netconsole_target(struct config_group *group,
struct netconsole_target *nt;
unsigned long flags;
/* Checking if a target by this name was created at boot time. If so,
* attach a configfs entry to that target. This enables dynamic
* control.
*/
if (!strncmp(name, NETCONSOLE_PARAM_TARGET_PREFIX,
strlen(NETCONSOLE_PARAM_TARGET_PREFIX))) {
nt = find_cmdline_target(name);
if (nt)
return &nt->item;
}
nt = alloc_and_init();
if (!nt)
return ERR_PTR(-ENOMEM);