The patch titled
Subject: ipc: allow boot time extension of IPCMNI from 32k to 16M
has been added to the -mm tree. Its filename is
ipc-allow-boot-time-extension-of-ipcmni-from-32k-to-16m.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ipc-allow-boot-time-extension-of-ipcmni-from-32k-to-16m.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ipc-allow-boot-time-extension-of-ipcmni-from-32k-to-16m.patch
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------------------------------------------------------
From: Waiman Long <longman@xxxxxxxxxx>
Subject: ipc: allow boot time extension of IPCMNI from 32k to 16M
Patch series "ipc: Increase IPCMNI limit", v12.
There are users out there requesting increase in the IPCMNI value to more
than 32k. This patchset does that by using a boot kernel parameter
"ipcmni_extend" to increase the IPCMNI limit from 32k to 16M when that
boot command line option is specified.
Patch 1 adds a "ipcmni_extend" boot command line parameter to extend the
IPCMNI limit from 32k to 16M.
Patch 2 changes how the sequence number within an id is being generated by
incrementing it only when the generated id is not greater than the
previous one. That reduces the chance of id reuse whether "ipcmni_extend"
is set or not.
Patch 3 makes identifier allocation go cyclical through the entire 24-bit
id space with "ipcmni_extend" only to further reduce the chance of id
reuse, but probably with a slight memory and performance overhead.
The cyclical id allocation isn't done for non-ipcmni_extend mode as the
potential memory and performance overhead may be problematic on system
with slow CPU and little memory. Systems that run applications which need
more than 32k IPC identifiers can certainly afford the extra overhead.
This patch (of 3):
The maximum number of unique System V IPC identifiers was limited to 32k.
That limit should be big enough for most use cases.
However, there are some users out there requesting for more, especially
those that are migrating from Solaris which uses 24 bits for unique
identifiers. To satisfy the need of those users, a new boot time kernel
option "ipcmni_extend" is added to extend the IPCMNI value to 16M. This
is a 512X increase which should be big enough for users out there that
need a large number of unique IPC identifier.
The use of this new option will change the pattern of the IPC identifiers
returned by functions like shmget(2). An application that depends on such
pattern may not work properly. So it should only be used if the users
really need more than 32k of unique IPC numbers.
This new option does have the side effect of reducing the maximum number
of unique sequence numbers from 64k down to 128. So it is a trade-off.
The computation of a new IPC id is not done in the performance critical
path. So a little bit of additional overhead shouldn't have any real
performance impact.
Link: http://lkml.kernel.org/r/1551379645-819-2-git-send-email-longman@xxxxxxxxxx
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Acked-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Cc: "Luis R. Rodriguez" <mcgrof@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Takashi Iwai <tiwai@xxxxxxx>
Cc: Davidlohr Bueso <dbueso@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 3
ipc/ipc_sysctl.c | 12 +++
ipc/util.c | 10 +--
ipc/util.h | 44 +++++++++++---
4 files changed, 54 insertions(+), 15 deletions(-)
--- a/Documentation/admin-guide/kernel-parameters.txt~ipc-allow-boot-time-extension-of-ipcmni-from-32k-to-16m
+++ a/Documentation/admin-guide/kernel-parameters.txt
@@ -1812,6 +1812,9 @@
ip= [IP_PNP]
See Documentation/filesystems/nfs/nfsroot.txt.
+ ipcmni_extend [KNL] Extend the maximum number of unique System V
+ IPC identifiers from 32,768 to 16,777,216.
+
irqaffinity= [SMP] Set the default irq affinity mask
The argument is a cpu list, as described above.
--- a/ipc/ipc_sysctl.c~ipc-allow-boot-time-extension-of-ipcmni-from-32k-to-16m
+++ a/ipc/ipc_sysctl.c
@@ -120,7 +120,8 @@ static int proc_ipc_sem_dointvec(struct
static int zero;
static int one = 1;
static int int_max = INT_MAX;
-static int ipc_mni = IPCMNI;
+int ipc_mni = IPCMNI;
+int ipc_mni_shift = IPCMNI_SHIFT;
static struct ctl_table ipc_kern_table[] = {
{
@@ -246,3 +247,12 @@ static int __init ipc_sysctl_init(void)
}
device_initcall(ipc_sysctl_init);
+
+static int __init ipc_mni_extend(char *str)
+{
+ ipc_mni = IPCMNI_EXTEND;
+ ipc_mni_shift = IPCMNI_EXTEND_SHIFT;
+ pr_info("IPCMNI extended to %d.\n", ipc_mni);
+ return 0;
+}
+early_param("ipcmni_extend", ipc_mni_extend);
--- a/ipc/util.c~ipc-allow-boot-time-extension-of-ipcmni-from-32k-to-16m
+++ a/ipc/util.c
@@ -110,7 +110,7 @@ static const struct rhashtable_params ip
* @ids: ipc identifier set
*
* Set up the sequence range to use for the ipc identifier range (limited
- * below IPCMNI) then initialise the keys hashtable and ids idr.
+ * below ipc_mni) then initialise the keys hashtable and ids idr.
*/
void ipc_init_ids(struct ipc_ids *ids)
{
@@ -226,7 +226,7 @@ static inline int ipc_idr_alloc(struct i
0, GFP_NOWAIT);
}
if (idx >= 0)
- new->id = SEQ_MULTIPLIER * new->seq + idx;
+ new->id = (new->seq << IPCMNI_SEQ_SHIFT) + idx;
return idx;
}
@@ -254,8 +254,8 @@ int ipc_addid(struct ipc_ids *ids, struc
/* 1) Initialize the refcount so that ipc_rcu_putref works */
refcount_set(&new->refcount, 1);
- if (limit > IPCMNI)
- limit = IPCMNI;
+ if (limit > ipc_mni)
+ limit = ipc_mni;
if (ids->in_use >= limit)
return -ENOSPC;
@@ -738,7 +738,7 @@ static struct kern_ipc_perm *sysvipc_fin
if (total >= ids->in_use)
return NULL;
- for (; pos < IPCMNI; pos++) {
+ for (; pos < ipc_mni; pos++) {
ipc = idr_find(&ids->ipcs_idr, pos);
if (ipc != NULL) {
*new_pos = pos + 1;
--- a/ipc/util.h~ipc-allow-boot-time-extension-of-ipcmni-from-32k-to-16m
+++ a/ipc/util.h
@@ -15,8 +15,34 @@
#include <linux/err.h>
#include <linux/ipc_namespace.h>
-#define IPCMNI 32768 /* <= MAX_INT limit for ipc arrays (including sysctl changes) */
-#define SEQ_MULTIPLIER (IPCMNI)
+/*
+ * The IPC ID contains 2 separate numbers - index and sequence number.
+ * By default,
+ * bits 0-14: index (32k, 15 bits)
+ * bits 15-30: sequence number (64k, 16 bits)
+ *
+ * When IPCMNI extension mode is turned on, the composition changes:
+ * bits 0-23: index (16M, 24 bits)
+ * bits 24-30: sequence number (128, 7 bits)
+ */
+#define IPCMNI_SHIFT 15
+#define IPCMNI_EXTEND_SHIFT 24
+#define IPCMNI (1 << IPCMNI_SHIFT)
+#define IPCMNI_EXTEND (1 << IPCMNI_EXTEND_SHIFT)
+
+#ifdef CONFIG_SYSVIPC_SYSCTL
+extern int ipc_mni;
+extern int ipc_mni_shift;
+
+#define IPCMNI_SEQ_SHIFT ipc_mni_shift
+#define IPCMNI_IDX_MASK ((1 << ipc_mni_shift) - 1)
+
+#else /* CONFIG_SYSVIPC_SYSCTL */
+
+#define ipc_mni IPCMNI
+#define IPCMNI_SEQ_SHIFT IPCMNI_SHIFT
+#define IPCMNI_IDX_MASK ((1 << IPCMNI_SHIFT) - 1)
+#endif /* CONFIG_SYSVIPC_SYSCTL */
void sem_init(void);
void msg_init(void);
@@ -96,9 +122,9 @@ struct pid_namespace *ipc_seq_pid_ns(str
#define IPC_MSG_IDS 1
#define IPC_SHM_IDS 2
-#define ipcid_to_idx(id) ((id) % SEQ_MULTIPLIER)
-#define ipcid_to_seqx(id) ((id) / SEQ_MULTIPLIER)
-#define IPCID_SEQ_MAX min_t(int, INT_MAX/SEQ_MULTIPLIER, USHRT_MAX)
+#define ipcid_to_idx(id) ((id) & IPCMNI_IDX_MASK)
+#define ipcid_to_seqx(id) ((id) >> IPCMNI_SEQ_SHIFT)
+#define IPCID_SEQ_MAX (INT_MAX >> IPCMNI_SEQ_SHIFT)
/* must be called with ids->rwsem acquired for writing */
int ipc_addid(struct ipc_ids *, struct kern_ipc_perm *, int);
@@ -123,8 +149,8 @@ static inline int ipc_get_maxidx(struct
if (ids->in_use == 0)
return -1;
- if (ids->in_use == IPCMNI)
- return IPCMNI - 1;
+ if (ids->in_use == ipc_mni)
+ return ipc_mni - 1;
return ids->max_idx;
}
@@ -219,10 +245,10 @@ void free_ipcs(struct ipc_namespace *ns,
static inline int sem_check_semmni(struct ipc_namespace *ns) {
/*
- * Check semmni range [0, IPCMNI]
+ * Check semmni range [0, ipc_mni]
* semmni is the last element of sem_ctls[4] array
*/
- return ((ns->sem_ctls[3] < 0) || (ns->sem_ctls[3] > IPCMNI))
+ return ((ns->sem_ctls[3] < 0) || (ns->sem_ctls[3] > ipc_mni))
? -ERANGE : 0;
}
_
Patches currently in -mm which might be from longman@xxxxxxxxxx are
debugobjects-move-printk-out-of-db-lock-critical-sections.patch
include-linux-nodemaskh-use-nr_node_ids-not-max_numnodes-in-__nodemask_pr_numnodes.patch
ipc-allow-boot-time-extension-of-ipcmni-from-32k-to-16m.patch
ipc-conserve-sequence-numbers-in-ipcmni_extend-mode.patch
ipc-do-cyclic-id-allocation-with-ipcmni_extend-mode.patch
