Re: [PATCH v6 7/8] ipc: Allow boot time extension of IPCMNI from 32k to 2M

[kbuild test robot]

Hi Waiman,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v4.17-rc2 next-20180426]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]

url:
https://github.com/0day-ci/linux/commits/Waiman-Long/ipc-Clamp-mni-to-the-real-IPCMNI-limit-increase-that-limit/20180429-175431
config: m68k-stmark2_defconfig (attached as .config)
compiler: m68k-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
wget 
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O 
~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=m68k 

All errors (new ones prefixed by >>):

   ipc/util.o: In function `sysvipc_find_ipc':
>> util.c:(.text+0x2ca): undefined reference to `ipc_mni'
   ipc/util.o: In function `ipc_addid':
   util.c:(.text+0x448): undefined reference to `ipc_mni'
>> util.c:(.text+0x6d6): undefined reference to `ipc_mni_shift'
   ipc/util.o: In function `ipc_rmid':
   util.c:(.text+0x712): undefined reference to `ipc_mni_shift'
   ipc/util.o: In function `ipc_obtain_object_idr':
   util.c:(.text+0x97c): undefined reference to `ipc_mni_shift'
   ipc/util.o: In function `ipc_obtain_object_check':
   util.c:(.text+0x9f0): undefined reference to `ipc_mni_shift'
   ipc/msg.o: In function `ksys_msgctl':
>> msg.c:(.text+0x4da): undefined reference to `ipc_mni'
   ipc/sem.o: In function `semctl_info.isra.3':
>> sem.c:(.text+0x91c): undefined reference to `ipc_mni'
   ipc/shm.o: In function `ksys_shmctl':
>> shm.c:(.text+0xa36): undefined reference to `ipc_mni'
   shm.c:(.text+0xb0a): undefined reference to `ipc_mni'

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation


.config.gz
Description: application/gzip

[PATCH v6 7/8] ipc: Allow boot time extension of IPCMNI from 32k to 2M

[Waiman Long]

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. To satisfy
the need of those users, a new boot time kernel option "ipcmni_extend"
is added to extend the IPCMNI value to 2M. This is a 64X increase which
hopefully is big enough for them.

This new option does have the side effect of reducing the maximum
number of unique sequence numbers from 64k down to 1k. So it is
a trade-off.

Signed-off-by: Waiman Long 
---
 Documentation/admin-guide/kernel-parameters.txt |  3 +++
 ipc/ipc_sysctl.c| 12 +-
 ipc/util.c  | 12 +-
 ipc/util.h  | 30 ++---
 4 files changed, 42 insertions(+), 15 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt 
b/Documentation/admin-guide/kernel-parameters.txt
index 11fc28e..00bc0cb 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1735,6 +1735,9 @@
ip= [IP_PNP]
See Documentation/filesystems/nfs/nfsroot.txt.
 
+   ipcmni_extend   [KNL] Extend the maximum number of unique System V
+   IPC identifiers from 32768 to 2097152.
+
irqaffinity=[SMP] Set the default irq affinity mask
The argument is a cpu list, as described above.
 
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index 478e634..4e2cb6d 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -109,7 +109,8 @@ static int proc_ipc_sem_dointvec(struct ctl_table *table, 
int write,
 static int zero;
 static int one = 1;
 static int int_max = INT_MAX;
-static int ipc_mni = IPCMNI;
+int ipc_mni __read_mostly = IPCMNI;
+int ipc_mni_shift __read_mostly = IPCMNI_SHIFT;
 
 static struct ctl_table ipc_kern_table[] = {
{
@@ -237,3 +238,12 @@ 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);
diff --git a/ipc/util.c b/ipc/util.c
index 4e81182..782a8d0 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -113,7 +113,7 @@ static int __init ipc_init(void)
  * @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.
  */
 int ipc_init_ids(struct ipc_ids *ids)
 {
@@ -214,7 +214,7 @@ static inline int ipc_buildid(int id, struct ipc_ids *ids,
ids->next_id = -1;
}
 
-   return SEQ_MULTIPLIER * new->seq + id;
+   return (new->seq << SEQ_SHIFT) + id;
 }
 
 #else
@@ -228,7 +228,7 @@ static inline int ipc_buildid(int id, struct ipc_ids *ids,
if (ids->seq > IPCID_SEQ_MAX)
ids->seq = 0;
 
-   return SEQ_MULTIPLIER * new->seq + id;
+   return (new->seq << SEQ_SHIFT) + id;
 }
 
 #endif /* CONFIG_CHECKPOINT_RESTORE */
@@ -252,8 +252,8 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm 
*new, int limit)
kgid_t egid;
int id, err;
 
-   if (limit > IPCMNI)
-   limit = IPCMNI;
+   if (limit > ipc_mni)
+   limit = ipc_mni;
 
if (!ids->tables_initialized || ids->in_use >= limit)
return -ENOSPC;
@@ -777,7 +777,7 @@ static struct kern_ipc_perm *sysvipc_find_ipc(struct 
ipc_ids *ids, loff_t pos,
if (total >= ids->in_use)
return NULL;
 
-   for (; pos < IPCMNI; pos++) {
+   for (; pos < ipc_mni; pos++) {
ipc = idr_find(>ipcs_idr, pos);
if (ipc != NULL) {
*new_pos = pos + 1;
diff --git a/ipc/util.h b/ipc/util.h
index 7c20871..e4d14b6 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -15,8 +15,22 @@
 #include 
 #include 
 
-#define IPCMNI 32768  /* <= MAX_INT limit for ipc arrays (including sysctl 
changes) */
-#define SEQ_MULTIPLIER (IPCMNI)
+/*
+ * By default, the ipc arrays can have up to 32k (15 bits) entries.
+ * When IPCMNI extension mode is turned on, the ipc arrays can have up
+ * to 2M (21 bits) entries. However, the space for sequence number will
+ * be shrunk from 16 bits to 10 bits.
+ */
+#define IPCMNI_SHIFT   15
+#define IPCMNI_EXTEND_SHIFT21
+#define IPCMNI (1 << IPCMNI_SHIFT)
+#define IPCMNI_EXTEND  (1 << IPCMNI_EXTEND_SHIFT)
+
+extern int ipc_mni;
+extern int ipc_mni_shift;
+
+#define SEQ_SHIFT  ipc_mni_shift
+#define SEQ_MASK   ((1 << ipc_mni_shift) - 1)
 
 int sem_init(void);
 int msg_init(void);
@@ -96,9 +110,9 @@ void __init ipc_init_proc_interface(const