[PATCH 02/04]

This patch proposes the procfs facilities needed to feed the id(s) for the
next task to be forked.

say n is the number of pids to be provided through procfs:

if an
echo "LONG<n> X0 X1 ... X<n-1>" > /proc/self/next_pids
is issued, the next task to be forked will have its upid nrs set as follows
(say it is forked in a pid ns of level L):

level         upid nr
L ----------> X0
..
L - i ------> Xi
..
L - n + 1 --> X<n-1>

Then, for levels L-n down to level 0, the pids will be left to the kernel
choice.

Signed-off-by: Nadia Derbey <[EMAIL PROTECTED]>

---
 include/linux/sysids.h |   27 ++++++++
 kernel/nextid.c        |  150 ++++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 155 insertions(+), 22 deletions(-)

Index: linux-2.6.25-rc8-mm1/include/linux/sysids.h
===================================================================
--- linux-2.6.25-rc8-mm1.orig/include/linux/sysids.h    2008-04-04 
13:53:04.000000000 +0200
+++ linux-2.6.25-rc8-mm1/include/linux/sysids.h 2008-04-04 14:18:04.000000000 
+0200
@@ -8,8 +8,33 @@
 #ifndef _LINUX_SYSIDS_H
 #define _LINUX_SYSIDS_H
 
+
+#define NIDS_SMALL       32
+#define NIDS_PER_BLOCK   ((unsigned int)(PAGE_SIZE / sizeof(long)))
+
+/* access the ids "array" with this macro */
+#define ID_AT(pi, i)   \
+       ((pi)->blocks[(i) / NIDS_PER_BLOCK][(i) % NIDS_PER_BLOCK])
+
+
+/*
+ * List of ids for the next object to be created. This presently applies to
+ * next process to be created.
+ * The next process to be created is associated to a set of upid nrs: one for
+ * each pid namespace level that process belongs to.
+ * upid nrs from level 0 up to level <npids - 1> will be automatically
+ * allocated.
+ * upid nr for level nids will be set to blocks[0][0]
+ * upid nr for level <nids + i> will be set to ID_AT(ids, i);
+ *
+ * If a single id is needed, nids is set to 1 and small_block[0] is set to
+ * that id.
+ */
 struct sys_id {
-       long id;
+       int nids;
+       long small_block[NIDS_SMALL];
+       int nblocks;
+       long *blocks[0];
 };
 
 extern ssize_t get_nextid(struct task_struct *, char *, size_t);
Index: linux-2.6.25-rc8-mm1/kernel/nextid.c
===================================================================
--- linux-2.6.25-rc8-mm1.orig/kernel/nextid.c   2008-04-04 13:59:59.000000000 
+0200
+++ linux-2.6.25-rc8-mm1/kernel/nextid.c        2008-04-04 14:28:13.000000000 
+0200
@@ -13,38 +13,138 @@
 
 
 
+static struct sys_id *id_blocks_alloc(int nids)
+{
+       struct sys_id *ids;
+       int nblocks;
+       int i;
+
+       nblocks = (nids + NIDS_PER_BLOCK - 1) / NIDS_PER_BLOCK;
+       BUG_ON(nblocks < 1);
+
+       ids = kmalloc(sizeof(*ids) + nblocks * sizeof(long *), GFP_KERNEL);
+       if (!ids)
+               return NULL;
+       ids->nids = nids;
+       ids->nblocks = nblocks;
+
+       if (nids <= NIDS_SMALL)
+               ids->blocks[0] = ids->small_block;
+       else {
+               for (i = 0; i < nblocks; i++) {
+                       long *b;
+                       b = (void *)__get_free_page(GFP_KERNEL);
+                       if (!b)
+                               goto out_undo_partial_alloc;
+                       ids->blocks[i] = b;
+               }
+       }
+       return ids;
+
+out_undo_partial_alloc:
+       while (--i >= 0)
+               free_page((unsigned long)ids->blocks[i]);
+
+       kfree(ids);
+       return NULL;
+}
+
+static void id_blocks_free(struct sys_id *ids)
+{
+       if (ids == NULL)
+               return;
+
+       if (ids->blocks[0] != ids->small_block) {
+               int i;
+               for (i = 0; i < ids->nblocks; i++)
+                       free_page((unsigned long)ids->blocks[i]);
+       }
+       kfree(ids);
+       return;
+}
+
 ssize_t get_nextid(struct task_struct *task, char *buffer, size_t size)
 {
+       ssize_t count = 0;
        struct sys_id *sid;
+       char *bufptr = buffer;
+       int i;
 
        sid = task->next_id;
-       if (!sid)
+       if (!sid || !sid->nids)
                return snprintf(buffer, size, "UNSET\n");
 
-       return snprintf(buffer, size, "LONG %ld\n", sid->id);
+       count = sprintf(bufptr, "LONGS (%d) ", sid->nids);
+
+       for (i = 0; i < sid->nids - 1; i++)
+               count += sprintf(&bufptr[count], "%ld ", ID_AT(sid, i));
+
+       count += sprintf(&bufptr[count], "%ld\n", ID_AT(sid, i));
+
+       return count;
 }
 
-static int set_single_id(struct task_struct *task, char *buffer)
+static int fill_nextid_list(struct task_struct *task, int nids, char *buffer)
 {
-       struct sys_id *sid;
-       long next_id;
+       char *token, *buff = buffer;
        char *end;
+       struct sys_id *sid;
+       struct sys_id *old_list = task->next_id;
+       int i;
 
-       next_id = simple_strtol(buffer, &end, 0);
-       if (end == buffer || (end && !isspace(*end)))
-               return -EINVAL;
+       sid = id_blocks_alloc(nids);
+       if (!sid)
+               return -ENOMEM;
 
-       sid = task->next_id;
-       if (!sid) {
-               sid = kzalloc(sizeof(*sid), GFP_KERNEL);
-               if (!sid)
-                       return -ENOMEM;
-               task->next_id = sid;
+       i = 0;
+       while ((token = strsep(&buff, " ")) != NULL && i < nids) {
+               long id;
+
+               if (!*token)
+                       goto out_free;
+               id = simple_strtol(token, &end, 0);
+               if (end == token || (*end && !isspace(*end)))
+                       goto out_free;
+               ID_AT(sid, i) = id;
+               i++;
        }
 
-       sid->id = next_id;
+       if (i != nids)
+               /* Not enough pids compared to npids */
+               goto out_free;
+
+       if (old_list)
+               id_blocks_free(old_list);
 
+       task->next_id = sid;
        return 0;
+
+out_free:
+       id_blocks_free(sid);
+       return -EINVAL;
+}
+
+/*
+ * Parses a line with the following format:
+ * <x> <id0> ... <idx-1>
+ * and sets <id0> to <idx-1> as the sequence of ids to be used for the next
+ * object to be created by the task.
+ * This applies to processes that need 1 id per namespace level.
+ * Any trailing character on the line is skipped.
+ */
+static int set_multiple_ids(struct task_struct *task, char *nb, char *buffer)
+{
+       int nids;
+       char *end;
+
+       nids = simple_strtol(nb, &end, 0);
+       if (*end)
+               return -EINVAL;
+
+       if (nids <= 0)
+               return -EINVAL;
+
+       return fill_nextid_list(task, nids, buffer);
 }
 
 int reset_nextid(struct task_struct *task)
@@ -55,8 +155,8 @@ int reset_nextid(struct task_struct *tas
        if (!sid)
                return 0;
 
+       id_blocks_free(sid);
        task->next_id = NULL;
-       kfree(sid);
        return 0;
 }
 
@@ -65,12 +165,14 @@ int reset_nextid(struct task_struct *tas
 
 /*
  * Parses a line written to /proc/self/next_id.
- * this line has the following format:
+ * this line has one of the following formats:
  * LONG id              --> a single id is specified
+ * LONG<x> id0 ... id<x-1> --> a sequence of ids is specified
  */
 int set_nextid(struct task_struct *task, char *buffer)
 {
        char *token, *out = buffer;
+       size_t sz;
 
        if (!out)
                return -EINVAL;
@@ -78,9 +180,15 @@ int set_nextid(struct task_struct *task,
        token = strsep(&out, " ");
 
        if (!strcmp(token, LONG_STR))
-               return set_single_id(task, out);
-       else if (!strncmp(token, RESET_STR, strlen(RESET_STR)))
+               return fill_nextid_list(task, 1, out);
+
+       sz = strlen(LONG_STR);
+
+       if (!strncmp(token, LONG_STR, sz))
+               return set_multiple_ids(task, token + sz, out);
+
+       if (!strncmp(token, RESET_STR, strlen(RESET_STR)))
                return reset_nextid(task);
-       else
-               return -EINVAL;
+
+       return -EINVAL;
 }

--
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