OpenVZ Forum


Home » Mailing lists » Devel » [PATCH v8 2/5] ipc: add sysctl to specify desired next object id
[PATCH v8 2/5] ipc: add sysctl to specify desired next object id [message #48598] Wed, 24 October 2012 15:35 Go to next message
Stanislav Kinsbursky is currently offline  Stanislav Kinsbursky
Messages: 683
Registered: October 2011
Senior Member
From: *parallels.com
This patch adds 3 new variables and sysctls to tune them (by one "next_id"
variable for messages, semaphores and shared memory respectively).
This variable can be used to set desired id for next allocated IPC object.
By default it's equal to -1 and old behaviour is preserved.
If this variable is non-negative, then desired idr will be extracted from it
and used as a start value to search for free IDR slot.

Notes:
1) this patch doesn't garantee, that new object will have desired id. So it's
up to user space how to handle new object with wrong id.
2) After sucessfull id allocation attempt, "next_id" will be set back to -1
(if it was non-negative).

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
include/linux/ipc_namespace.h | 1 +
ipc/ipc_sysctl.c | 28 ++++++++++++++++++++++++++++
ipc/util.c | 16 ++++++++++++----
ipc/util.h | 1 +
4 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 5499c92..8704e40 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -24,6 +24,7 @@ struct ipc_ids {
unsigned short seq_max;
struct rw_semaphore rw_mutex;
struct idr ipcs_idr;
+ int next_id;
};

struct ipc_namespace {
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index 00fba2b..d06d77a 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -158,6 +158,7 @@ static int proc_ipcauto_dointvec_minmax(ctl_table *table, int write,

static int zero;
static int one = 1;
+static int int_max = INT_MAX;

static struct ctl_table ipc_kern_table[] = {
{
@@ -227,6 +228,33 @@ static struct ctl_table ipc_kern_table[] = {
.extra1 = &zero,
.extra2 = &one,
},
+ {
+ .procname = "sem_next_id",
+ .data = &init_ipc_ns.ids[IPC_SEM_IDS].next_id,
+ .maxlen = sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id),
+ .mode = 0644,
+ .proc_handler = proc_ipc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &int_max,
+ },
+ {
+ .procname = "msg_next_id",
+ .data = &init_ipc_ns.ids[IPC_MSG_IDS].next_id,
+ .maxlen = sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id),
+ .mode = 0644,
+ .proc_handler = proc_ipc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &int_max,
+ },
+ {
+ .procname = "shm_next_id",
+ .data = &init_ipc_ns.ids[IPC_SHM_IDS].next_id,
+ .maxlen = sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id),
+ .mode = 0644,
+ .proc_handler = proc_ipc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &int_max,
+ },
{}
};

diff --git a/ipc/util.c b/ipc/util.c
index 72fd078..a961e46 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -122,6 +122,7 @@ void ipc_init_ids(struct ipc_ids *ids)

ids->in_use = 0;
ids->seq = 0;
+ ids->next_id = -1;
{
int seq_limit = INT_MAX/SEQ_MULTIPLIER;
if (seq_limit > USHRT_MAX)
@@ -252,6 +253,7 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
kuid_t euid;
kgid_t egid;
int id, err;
+ int next_id = ids->next_id;

if (size > IPCMNI)
size = IPCMNI;
@@ -264,7 +266,8 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
rcu_read_lock();
spin_lock(&new->lock);

- err = idr_get_new(&ids->ipcs_idr, new, &id);
+ err = idr_get_new_above(&ids->ipcs_idr, new,
+ (next_id < 0) ? 0 : ipcid_to_idx(next_id), &id);
if (err) {
spin_unlock(&new->lock);
rcu_read_unlock();
@@ -277,9 +280,14 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
new->cuid = new->uid = euid;
new->gid = new->cgid = egid;

- new->seq = ids->seq++;
- if(ids->seq > ids->seq_max)
- ids->seq = 0;
+ if (next_id < 0) {
+ new->seq = ids->seq++;
+ if(ids->seq > ids->seq_max)
+ ids->seq = 0;
+ } else {
+ new->seq = ipcid_to_seqx(next_id);
+ ids->next_id = -1;
+ }

new->id = ipc_buildid(id, new->seq);
return id;
diff --git a/ipc/util.h b/ipc/util.h
index c8fe2f7..a61e0ca 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -92,6 +92,7 @@ void __init ipc_init_proc_interface(const char *path, const char *header,
#define IPC_SHM_IDS 2

#define ipcid_to_idx(id) ((id) % SEQ_MULTIPLIER)
+#define ipcid_to_seqx(id) ((id) / SEQ_MULTIPLIER)

/* must be called with ids->rw_mutex acquired for writing */
int ipc_addid(struct ipc_ids *, struct kern_ipc_perm *, int);
Re: [PATCH v8 2/5] ipc: add sysctl to specify desired next object id [message #48609 is a reply to message #48598] Wed, 24 October 2012 21:41 Go to previous messageGo to next message
akpm is currently offline  akpm
Messages: 224
Registered: March 2007
Senior Member
From: *parallels.com
On Wed, 24 Oct 2012 19:35:09 +0400
Stanislav Kinsbursky <skinsbursky@parallels.com> wrote:

> This patch adds 3 new variables and sysctls to tune them (by one "next_id"
> variable for messages, semaphores and shared memory respectively).
> This variable can be used to set desired id for next allocated IPC object.
> By default it's equal to -1 and old behaviour is preserved.
> If this variable is non-negative, then desired idr will be extracted from it
> and used as a start value to search for free IDR slot.
>
> Notes:
> 1) this patch doesn't garantee, that new object will have desired id. So it's
> up to user space how to handle new object with wrong id.
> 2) After sucessfull id allocation attempt, "next_id" will be set back to -1
> (if it was non-negative).
>
> --- a/ipc/ipc_sysctl.c
> +++ b/ipc/ipc_sysctl.c
> @@ -158,6 +158,7 @@ static int proc_ipcauto_dointvec_minmax(ctl_table *table, int write,
>
> static int zero;
> static int one = 1;
> +static int int_max = INT_MAX;
>
> static struct ctl_table ipc_kern_table[] = {
> {
> @@ -227,6 +228,33 @@ static struct ctl_table ipc_kern_table[] = {
> .extra1 = &zero,
> .extra2 = &one,
> },
> + {
> + .procname = "sem_next_id",
> + .data = &init_ipc_ns.ids[IPC_SEM_IDS].next_id,
> + .maxlen = sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id),
> + .mode = 0644,
> + .proc_handler = proc_ipc_dointvec_minmax,
> + .extra1 = &zero,
> + .extra2 = &int_max,
> + },
> + {
> + .procname = "msg_next_id",
> + .data = &init_ipc_ns.ids[IPC_MSG_IDS].next_id,
> + .maxlen = sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id),
> + .mode = 0644,
> + .proc_handler = proc_ipc_dointvec_minmax,
> + .extra1 = &zero,
> + .extra2 = &int_max,
> + },
> + {
> + .procname = "shm_next_id",
> + .data = &init_ipc_ns.ids[IPC_SHM_IDS].next_id,
> + .maxlen = sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id),
> + .mode = 0644,
> + .proc_handler = proc_ipc_dointvec_minmax,
> + .extra1 = &zero,
> + .extra2 = &int_max,
> + },
> {}
> };

ipc_kern_table[] is (badly) documented in
Documentation/sysctl/kernel.txt. Can we at least mention these
controls in there? Better, create a new way of properly documenting
each control and document these three in that manner? Better still,
document all the other ones as well ;)

The patch adds these controls to CONFIG_CHECKPOINT_RESTORE=n kernels.
Why is this?
Re: [PATCH v8 2/5] ipc: add sysctl to specify desired next object id [message #48613 is a reply to message #48609] Thu, 25 October 2012 07:53 Go to previous message
Stanislav Kinsbursky is currently offline  Stanislav Kinsbursky
Messages: 683
Registered: October 2011
Senior Member
From: *parallels.com
25.10.2012 01:41, Andrew Morton пишет:
> On Wed, 24 Oct 2012 19:35:09 +0400
> Stanislav Kinsbursky <skinsbursky@parallels.com> wrote:
>
>> This patch adds 3 new variables and sysctls to tune them (by one "next_id"
>> variable for messages, semaphores and shared memory respectively).
>> This variable can be used to set desired id for next allocated IPC object.
>> By default it's equal to -1 and old behaviour is preserved.
>> If this variable is non-negative, then desired idr will be extracted from it
>> and used as a start value to search for free IDR slot.
>>
>> Notes:
>> 1) this patch doesn't garantee, that new object will have desired id. So it's
>> up to user space how to handle new object with wrong id.
>> 2) After sucessfull id allocation attempt, "next_id" will be set back to -1
>> (if it was non-negative).
>>
>> --- a/ipc/ipc_sysctl.c
>> +++ b/ipc/ipc_sysctl.c
>> @@ -158,6 +158,7 @@ static int proc_ipcauto_dointvec_minmax(ctl_table *table, int write,
>>
>> static int zero;
>> static int one = 1;
>> +static int int_max = INT_MAX;
>>
>> static struct ctl_table ipc_kern_table[] = {
>> {
>> @@ -227,6 +228,33 @@ static struct ctl_table ipc_kern_table[] = {
>> .extra1 = &zero,
>> .extra2 = &one,
>> },
>> + {
>> + .procname = "sem_next_id",
>> + .data = &init_ipc_ns.ids[IPC_SEM_IDS].next_id,
>> + .maxlen = sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id),
>> + .mode = 0644,
>> + .proc_handler = proc_ipc_dointvec_minmax,
>> + .extra1 = &zero,
>> + .extra2 = &int_max,
>> + },
>> + {
>> + .procname = "msg_next_id",
>> + .data = &init_ipc_ns.ids[IPC_MSG_IDS].next_id,
>> + .maxlen = sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id),
>> + .mode = 0644,
>> + .proc_handler = proc_ipc_dointvec_minmax,
>> + .extra1 = &zero,
>> + .extra2 = &int_max,
>> + },
>> + {
>> + .procname = "shm_next_id",
>> + .data = &init_ipc_ns.ids[IPC_SHM_IDS].next_id,
>> + .maxlen = sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id),
>> + .mode = 0644,
>> + .proc_handler = proc_ipc_dointvec_minmax,
>> + .extra1 = &zero,
>> + .extra2 = &int_max,
>> + },
>> {}
>> };
>
> ipc_kern_table[] is (badly) documented in
> Documentation/sysctl/kernel.txt. Can we at least mention these
> controls in there? Better, create a new way of properly documenting
> each control and document these three in that manner? Better still,
> document all the other ones as well ;)
>

Yes, sure. I'll do my best.

> The patch adds these controls to CONFIG_CHECKPOINT_RESTORE=n kernels.
> Why is this?
>

I'll fix this.

--
Best regards,
Stanislav Kinsbursky
Previous Topic: [RFC PATCH v8 0/5] IPC: checkpoint/restore in userspace enhancements
Next Topic: [PATCH v2 00/11] fuse: optimize scatter-gather direct IO
Goto Forum:
  


Current Time: Wed Oct 18 22:06:24 GMT 2017