The patch titled
Subject: ipc: message queue copy feature introduced
has been added to the -mm tree. Its filename is
ipc-message-queue-copy-feature-introduced.patch
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From: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
Subject: ipc: message queue copy feature introduced
This patch is required for checkpoint/restore in userspace.
c/r requires some way to get all pending IPC messages without deleting
them from the queue (checkpoint can fail and in this case tasks will be
resumed, so queue have to be valid).
To achive this, new operation flag MSG_COPY for sys_msgrcv() system call
was introduced. If this flag was specified, then mtype is interpreted as
number of the message to copy.
If MSG_COPY is set, then kernel will allocate dummy message with passed
size, and then use new copy_msg() helper function to copy desired message
(instead of unlinking it from the queue).
Notes:
1) Return -ENOSYS if MSG_COPY is specified, but
CONFIG_CHECKPOINT_RESTORE is not set.
Signed-off-by: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
Cc: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/uapi/linux/msg.h | 1
ipc/msg.c | 50 +++++++++++++++++++++++++++++++++++--
ipc/msgutil.c | 38 ++++++++++++++++++++++++++++
ipc/util.h | 1
4 files changed, 88 insertions(+), 2 deletions(-)
diff -puN include/uapi/linux/msg.h~ipc-message-queue-copy-feature-introduced include/uapi/linux/msg.h
--- a/include/uapi/linux/msg.h~ipc-message-queue-copy-feature-introduced
+++ a/include/uapi/linux/msg.h
@@ -10,6 +10,7 @@
/* msgrcv options */
#define MSG_NOERROR 010000 /* no error if message is too big */
#define MSG_EXCEPT 020000 /* recv any msg except of specified type.*/
+#define MSG_COPY 040000 /* copy (not remove) all queue messages */
/* Obsolete, used only for backwards compatibility and libc5 compiles */
struct msqid_ds {
diff -puN ipc/msg.c~ipc-message-queue-copy-feature-introduced ipc/msg.c
--- a/ipc/msg.c~ipc-message-queue-copy-feature-introduced
+++ a/ipc/msg.c
@@ -777,19 +777,48 @@ long do_msgrcv(int msqid, void __user *b
struct msg_msg *msg;
int mode;
struct ipc_namespace *ns;
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ struct msg_msg *copy = NULL;
+ unsigned long copy_number = 0;
+#endif
if (msqid < 0 || (long) bufsz < 0)
return -EINVAL;
+ if (msgflg & MSG_COPY) {
+#ifdef CONFIG_CHECKPOINT_RESTORE
+
+ if (msgflg & MSG_COPY) {
+ copy_number = msgtyp;
+ msgtyp = 0;
+ }
+
+ /*
+ * Create dummy message to copy real message to.
+ */
+ copy = load_msg(buf, bufsz);
+ if (IS_ERR(copy))
+ return PTR_ERR(copy);
+ copy->m_ts = bufsz;
+#else
+ return -ENOSYS;
+#endif
+ }
mode = convert_mode(&msgtyp, msgflg);
ns = current->nsproxy->ipc_ns;
msq = msg_lock_check(ns, msqid);
- if (IS_ERR(msq))
+ if (IS_ERR(msq)) {
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ if (msgflg & MSG_COPY)
+ free_msg(copy);
+#endif
return PTR_ERR(msq);
+ }
for (;;) {
struct msg_receiver msr_d;
struct list_head *tmp;
+ long msg_counter = 0;
msg = ERR_PTR(-EACCES);
if (ipcperms(ns, &msq->q_perm, S_IRUGO))
@@ -809,8 +838,16 @@ long do_msgrcv(int msqid, void __user *b
if (mode == SEARCH_LESSEQUAL &&
walk_msg->m_type != 1) {
msgtyp = walk_msg->m_type - 1;
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ } else if (msgflg & MSG_COPY) {
+ if (copy_number == msg_counter) {
+ msg = copy_msg(walk_msg, copy);
+ break;
+ }
+#endif
} else
break;
+ msg_counter++;
}
tmp = tmp->next;
}
@@ -823,6 +860,10 @@ long do_msgrcv(int msqid, void __user *b
msg = ERR_PTR(-E2BIG);
goto out_unlock;
}
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ if (msgflg & MSG_COPY)
+ goto out_unlock;
+#endif
list_del(&msg->m_list);
msq->q_qnum--;
msq->q_rtime = get_seconds();
@@ -906,8 +947,13 @@ out_unlock:
break;
}
}
- if (IS_ERR(msg))
+ if (IS_ERR(msg)) {
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ if (msgflg & MSG_COPY)
+ free_msg(copy);
+#endif
return PTR_ERR(msg);
+ }
bufsz = msg_handler(buf, msg, bufsz);
free_msg(msg);
diff -puN ipc/msgutil.c~ipc-message-queue-copy-feature-introduced ipc/msgutil.c
--- a/ipc/msgutil.c~ipc-message-queue-copy-feature-introduced
+++ a/ipc/msgutil.c
@@ -100,7 +100,45 @@ out_err:
free_msg(msg);
return ERR_PTR(err);
}
+#ifdef CONFIG_CHECKPOINT_RESTORE
+struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst)
+{
+ struct msg_msgseg *dst_pseg, *src_pseg;
+ int len = src->m_ts;
+ int alen;
+
+ BUG_ON(dst == NULL);
+ if (src->m_ts > dst->m_ts)
+ return ERR_PTR(-EINVAL);
+
+ alen = len;
+ if (alen > DATALEN_MSG)
+ alen = DATALEN_MSG;
+
+ dst->next = NULL;
+ dst->security = NULL;
+ memcpy(dst + 1, src + 1, alen);
+
+ len -= alen;
+ dst_pseg = dst->next;
+ src_pseg = src->next;
+ while (len > 0) {
+ alen = len;
+ if (alen > DATALEN_SEG)
+ alen = DATALEN_SEG;
+ memcpy(dst_pseg + 1, src_pseg + 1, alen);
+ dst_pseg = dst_pseg->next;
+ len -= alen;
+ src_pseg = src_pseg->next;
+ }
+
+ dst->m_type = src->m_type;
+ dst->m_ts = src->m_ts;
+
+ return dst;
+}
+#endif
int store_msg(void __user *dest, struct msg_msg *msg, int len)
{
int alen;
diff -puN ipc/util.h~ipc-message-queue-copy-feature-introduced ipc/util.h
--- a/ipc/util.h~ipc-message-queue-copy-feature-introduced
+++ a/ipc/util.h
@@ -140,6 +140,7 @@ int ipc_parse_version (int *cmd);
extern void free_msg(struct msg_msg *msg);
extern struct msg_msg *load_msg(const void __user *src, int len);
+extern struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst);
extern int store_msg(void __user *dest, struct msg_msg *msg, int len);
extern void recompute_msgmni(struct ipc_namespace *);
_
Patches currently in -mm which might be from skinsbursky@xxxxxxxxxxxxx are
origin.patch
proc-check-vma-vm_file-before-dereferencing.patch
ipc-remove-forced-assignment-of-selected-message.patch
ipc-add-sysctl-to-specify-desired-next-object-id.patch
ipc-add-sysctl-to-specify-desired-next-object-id-checkpatch-fixes.patch
ipc-message-queue-receive-cleanup.patch
ipc-message-queue-receive-cleanup-checkpatch-fixes.patch
ipc-message-queue-copy-feature-introduced.patch
selftests-ipc-message-queue-copy-feature-test.patch
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