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authorStanislav Kinsbursky <skinsbursky@parallels.com>2013-01-04 15:34:50 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-01-04 16:11:45 -0800
commit03f595668017f1a1fb971c02fc37140bc6e7bb1c (patch)
tree3aa5c4b32b5fd396f0d74679548de8c09ca195a1 /ipc
parent9afdacda0252fc1ddb7907728e878518edbcdfce (diff)
downloadlinux-03f595668017f1a1fb971c02fc37140bc6e7bb1c.tar.gz
ipc: add sysctl to specify desired next object id
Add 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 guarantee that the new object will have desired id. So it's up to user space how to handle new object with wrong id. 2) After a sucessful id allocation attempt, "next_id" will be set back to -1 (if it was non-negative). [akpm@linux-foundation.org: checkpatch fixes] Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com> Cc: Serge Hallyn <serge.hallyn@canonical.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
-rw-r--r--ipc/ipc_sysctl.c32
-rw-r--r--ipc/util.c16
-rw-r--r--ipc/util.h1
3 files changed, 45 insertions, 4 deletions
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index 00fba2bab87..130dfece27a 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -158,6 +158,9 @@ static int proc_ipcauto_dointvec_minmax(ctl_table *table, int write,
static int zero;
static int one = 1;
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static int int_max = INT_MAX;
+#endif
static struct ctl_table ipc_kern_table[] = {
{
@@ -227,6 +230,35 @@ static struct ctl_table ipc_kern_table[] = {
.extra1 = &zero,
.extra2 = &one,
},
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ {
+ .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,
+ },
+#endif
{}
};
diff --git a/ipc/util.c b/ipc/util.c
index 72fd0785ac9..74e1d9c7a98 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 c8fe2f7631e..a61e0ca2bff 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);