[Devel] [RFC][PATCH 2/4] Provide a new procfs interface to set next upid nr(s)
Nadia.Derbey at bull.net
Nadia.Derbey at bull.net
Fri Apr 4 07:51:31 PDT 2008
[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 <Nadia.Derbey at bull.net>
---
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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