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Subject[PATCH 5/6] kmod: Add new call_usermodehelper_timeout() API

In the blasphemous occasions that the Kernel must call a user-mode program
half of the times it is more robust to not wait forever but limit the wait
for a specified timeout.

So add a new call_usermodehelper_timeout() that implements that.
(Users of this new API will be added once this API is in mainline)

call_usermodehelper_fns() is added an extra timeout parameter which
is then implemented in call_usermodehelper_exec. The few users of
call_usermodehelper_fns() are also changed in this patch.

Also an gfp_t parameter is added, for finer allocation control

The code in call_usermodehelper_exec is simplified by the use of
the all-mighty wait_for_completion_timeout_state() which is able
to wait in all the different modes. See:
completion: Add wait_for_completion_timeout_state()

Should some wait-forever callers today, be converted to this new
schema?

CC: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
---
fs/exec.c | 4 ++--
include/linux/kmod.h | 19 ++++++++++++++-----
kernel/kmod.c | 24 ++++++++++++------------
kernel/sys.c | 2 +-
security/keys/request_key.c | 2 +-
5 files changed, 30 insertions(+), 21 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 23559c2..8789ba8 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -2185,8 +2185,8 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
}

retval = call_usermodehelper_fns(helper_argv[0], helper_argv,
- NULL, UMH_WAIT_EXEC, umh_pipe_setup,
- NULL, &cprm);
+ NULL, UMH_WAIT_EXEC, 0, 0,
+ umh_pipe_setup, NULL, &cprm);
argv_free(helper_argv);
if (retval) {
printk(KERN_INFO "Core dump to %s pipe failed\n",
diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index ae3f9623..4d9f202 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -60,21 +60,30 @@ struct subprocess_info {
char **argv;
char **envp;
int wait;
+ unsigned long timeout;
int retval;
int (*init)(struct subprocess_info *info, struct cred *new);
void (*cleanup)(struct subprocess_info *info);
void *data;
};

-extern int
-call_usermodehelper_fns(char *path, char **argv, char **envp, int wait,
- int (*init)(struct subprocess_info *info, struct cred *new),
- void (*cleanup)(struct subprocess_info *), void *data);
+extern int call_usermodehelper_fns(char *path, char **argv, char **envp,
+ int wait, unsigned long timeout, gfp_t gfp,
+ int (*init)(struct subprocess_info *info, struct cred *new),
+ void (*cleanup)(struct subprocess_info *), void *data);

static inline int
call_usermodehelper(char *path, char **argv, char **envp, int wait)
{
- return call_usermodehelper_fns(path, argv, envp, wait,
+ return call_usermodehelper_fns(path, argv, envp, wait, 0, 0,
+ NULL, NULL, NULL);
+}
+
+static inline int
+call_usermodehelper_timeout(char *path, char **argv, char **envp,
+ int wait, unsigned long timeout, gfp_t gfp)
+{
+ return call_usermodehelper_fns(path, argv, envp, wait, timeout, gfp,
NULL, NULL, NULL);
}

diff --git a/kernel/kmod.c b/kernel/kmod.c
index b404f99..588cb6f 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -90,7 +90,7 @@ static int call_modprobe(char *module_name, int wait)
argv[4] = NULL;

return call_usermodehelper_fns(modprobe_path, argv, envp,
- wait | UMH_KILLABLE, NULL, free_modprobe_argv, NULL);
+ wait | UMH_KILLABLE, 0, 0, NULL, free_modprobe_argv, NULL);
free_argv:
kfree(argv);
out:
@@ -522,6 +522,7 @@ void call_usermodehelper_setfns(struct subprocess_info *info,
int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
{
DECLARE_COMPLETION_ONSTACK(done);
+ int wait_state;
int retval = 0;

helper_lock();
@@ -540,19 +541,15 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
if (wait == UMH_NO_WAIT) /* task has freed sub_info */
goto unlock;

- if (wait & UMH_KILLABLE) {
- retval = wait_for_completion_killable(&done);
- if (!retval)
- goto wait_done;
-
+ wait_state = (wait & UMH_KILLABLE) ? TASK_KILLABLE : 0;
+ retval = wait_for_completion_timeout_state(&done, sub_info->timeout,
+ wait_state);
+ if (unlikely(retval)) {
/* umh_complete() will see NULL and free sub_info */
if (xchg(&sub_info->complete, NULL))
goto unlock;
- /* fallthrough, umh_complete() was already called */
}

- wait_for_completion(&done);
-wait_done:
retval = sub_info->retval;
out:
call_usermodehelper_freeinfo(sub_info);
@@ -561,13 +558,15 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
return retval;
}

-int call_usermodehelper_fns(
- char *path, char **argv, char **envp, int wait,
+int call_usermodehelper_fns(char *path, char **argv, char **envp,
+ int wait, unsigned long timeout, gfp_t gfp_mask,
int (*init)(struct subprocess_info *info, struct cred *new),
void (*cleanup)(struct subprocess_info *), void *data)
{
struct subprocess_info *info;
- gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
+
+ if (!gfp_mask)
+ gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;

info = call_usermodehelper_setup(path, argv, envp, gfp_mask);

@@ -575,6 +574,7 @@ int call_usermodehelper_fns(
return -ENOMEM;

call_usermodehelper_setfns(info, init, cleanup, data);
+ info->timeout = timeout;

return call_usermodehelper_exec(info, wait);
}
diff --git a/kernel/sys.c b/kernel/sys.c
index 37b1971..16d14d1 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2020,7 +2020,7 @@ int orderly_poweroff(bool force)
goto out;
}

- ret = call_usermodehelper_fns(argv[0], argv, envp, UMH_NO_WAIT,
+ ret = call_usermodehelper_fns(argv[0], argv, envp, UMH_NO_WAIT, 0, 0,
NULL, argv_cleanup, NULL);
out:
if (likely(!ret))
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 000e750..aa94dbb 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -93,7 +93,7 @@ static void umh_keys_cleanup(struct subprocess_info *info)
static int call_usermodehelper_keys(char *path, char **argv, char **envp,
struct key *session_keyring, int wait)
{
- return call_usermodehelper_fns(path, argv, envp, wait,
+ return call_usermodehelper_fns(path, argv, envp, wait, 0, 0,
umh_keys_init, umh_keys_cleanup,
key_get(session_keyring));
}
--
1.7.6.5



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