Quoting Dan Smith ([email protected]):
> This patch adds a "phase" of checkpoint that saves out information about any
> namespaces the task(s) may have. Do this by tracking the namespace objects
> of the tasks and making sure that tasks with the same namespace that follow
> get properly referenced in the checkpoint stream.
>
> I tested this with single and multiple task restore, on top of Oren's
> v13 tree.
>
> Changes:
> - Remove the kernel restore path
> - Punt on nested namespaces
> - Use __NEW_UTS_LEN in nodename and domainname buffers
> - Add a note to Documentation/checkpoint/internals.txt to indicate where
> in the save/restore process the UTS information is kept
> - Store (and track) the objref of the namespace itself instead of the
> nsproxy (based on comments from Dave on IRC)
> - Remove explicit check for non-root nsproxy
> - Store the nodename and domainname lengths and use cr_write_string()
> to store the actual name strings
> - Catch failure of cr_obj_add_ptr() in cr_write_namespaces()
> - Remove "types" bitfield and use the "is this new" flag to determine
> whether or not we should write out a new ns descriptor
> - Replace kernel restore path
> - Move the namespace information to be directly after the task
> information record
> - Update Documentation to reflect new location of namespace info
> - Support checkpoint and restart of nested UTS namespaces
>
> Cc: [email protected]
> Signed-off-by: Dan Smith <[email protected]>
> ---
> Documentation/checkpoint/internals.txt | 1 +
> checkpoint/Makefile | 1 +
> checkpoint/checkpoint.c | 66 ++++++++++++++++++++-
> checkpoint/objhash.c | 7 ++
> checkpoint/restart.c | 101
> ++++++++++++++++++++++++++++++++
> include/linux/checkpoint.h | 1 +
> include/linux/checkpoint_hdr.h | 11 ++++
> 7 files changed, 185 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/checkpoint/internals.txt
> b/Documentation/checkpoint/internals.txt
> index c741b6c..bdd202c 100644
> --- a/Documentation/checkpoint/internals.txt
> +++ b/Documentation/checkpoint/internals.txt
> @@ -17,6 +17,7 @@ The order of operations, both save and restore, is as
> follows:
> -> thread state: elements of thread_struct and thread_info
> -> CPU state: registers etc, including FPU
> -> memory state: memory address space layout and contents
> + -> namespace information
> -> filesystem state: [TBD] filesystem namespace state, chroot, cwd, etc
> -> files state: open file descriptors and their state
> -> signals state: [TBD] pending signals and signal handling state
> diff --git a/checkpoint/Makefile b/checkpoint/Makefile
> index 607d864..55c5c3d 100644
> --- a/checkpoint/Makefile
> +++ b/checkpoint/Makefile
> @@ -4,3 +4,4 @@
>
> obj-$(CONFIG_CHECKPOINT) += sys.o checkpoint.o restart.o objhash.o \
> ckpt_mem.o rstr_mem.o ckpt_file.o rstr_file.o
> +EXTRA_CFLAGS += -DDEBUG
> diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
> index c2f0e16..5f83e83 100644
> --- a/checkpoint/checkpoint.c
> +++ b/checkpoint/checkpoint.c
> @@ -213,6 +213,65 @@ static int cr_write_tail(struct cr_ctx *ctx)
> return ret;
> }
>
> +static int cr_write_utsns(struct cr_ctx *ctx, struct new_utsname *name)
> +{
> + struct cr_hdr h;
> + struct cr_hdr_utsns *hh = cr_hbuf_get(ctx, sizeof(*hh));
> + int ret;
> +
> + h.type = CR_HDR_UTSNS;
> + h.len = sizeof(*hh);
> +
> + hh->nodename_len = strlen(name->nodename) + 1;
> + hh->domainname_len = strlen(name->domainname) + 1;
> +
> + ret = cr_write_obj(ctx, &h, hh);
> + if (ret < 0)
> + goto out;
> +
> + ret = cr_write_string(ctx, name->nodename, hh->nodename_len);
> + if (ret < 0)
> + goto out;
> +
> + ret = cr_write_string(ctx, name->domainname, hh->domainname_len);
> + out:
> + cr_hbuf_put(ctx, sizeof(*hh));
> +
> + return ret;
> +}
> +
> +static int cr_write_namespaces(struct cr_ctx *ctx, struct task_struct *t)
> +{
> + struct cr_hdr h;
> + struct cr_hdr_namespaces *hh = cr_hbuf_get(ctx, sizeof(*hh));
> + struct nsproxy *nsp = t->nsproxy;
> + int ret;
> + int uts;
> +
> + h.type = CR_HDR_NS;
> + h.len = sizeof(*hh);
> +
> + uts = cr_obj_add_ptr(ctx, nsp->uts_ns, &hh->uts_ref, CR_OBJ_UTSNS, 0);
> + if (uts < 0)
> + goto out;
> +
> + ret = cr_write_obj(ctx, &h, hh);
> + if (ret)
> + goto out;
> +
> + if (uts) {
> + ret = cr_write_utsns(ctx, &nsp->uts_ns->name);
> + if (ret < 0)
> + goto out;
> + }
> +
> + /* FIXME: Write other namespaces here */
> + out:
> + cr_hbuf_put(ctx, sizeof(*hh));
> +
> + return ret;
> +}
> +
> /* dump the task_struct of a given task */
> static int cr_write_task_struct(struct cr_ctx *ctx, struct task_struct *t)
> {
> @@ -267,6 +326,10 @@ static int cr_write_task(struct cr_ctx *ctx, struct
> task_struct *t)
> goto out;
> ret = cr_write_cpu(ctx, t);
> cr_debug("cpu: ret %d\n", ret);
> + if (ret < 0)
> + goto out;
> + ret = cr_write_namespaces(ctx, t);
> + cr_debug("ns: ret %d\n", ret);
> out:
> return ret;
> }
> @@ -302,9 +365,6 @@ static int cr_may_checkpoint_task(struct task_struct *t,
> struct cr_ctx *ctx)
> if (t != current && !frozen(t))
> return -EBUSY;
>
> - if (task_nsproxy(t)->uts_ns != ctx->root_nsproxy->uts_ns)
> - return -EPERM;
> -
> if (task_nsproxy(t)->ipc_ns != ctx->root_nsproxy->ipc_ns)
> return -EPERM;
>
> diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
> index 25916c1..c6ae7c1 100644
> --- a/checkpoint/objhash.c
> +++ b/checkpoint/objhash.c
> @@ -12,6 +12,7 @@
> #include <linux/file.h>
> #include <linux/hash.h>
> #include <linux/checkpoint.h>
> +#include <linux/utsname.h>
>
> struct cr_objref {
> int objref;
> @@ -38,6 +39,9 @@ static void cr_obj_ref_drop(struct cr_objref *obj)
> case CR_OBJ_INODE:
> iput((struct inode *) obj->ptr);
> break;
> + case CR_OBJ_UTSNS:
> + put_uts_ns((struct uts_namespace *) obj->ptr);
> + break;
> default:
> BUG();
> }
> @@ -55,6 +59,9 @@ static int cr_obj_ref_grab(struct cr_objref *obj)
> if (!igrab((struct inode *) obj->ptr))
> ret = -EBADF;
> break;
> + case CR_OBJ_UTSNS:
> + get_uts_ns((struct uts_namespace *) obj->ptr);
> + break;
> default:
> BUG();
> }
> diff --git a/checkpoint/restart.c b/checkpoint/restart.c
> index d9e01ce..f42d549 100644
> --- a/checkpoint/restart.c
> +++ b/checkpoint/restart.c
> @@ -15,6 +15,8 @@
> #include <linux/magic.h>
> #include <linux/checkpoint.h>
> #include <linux/checkpoint_hdr.h>
> +#include <linux/utsname.h>
> +#include <linux/syscalls.h>
>
> #include "checkpoint_arch.h"
>
> @@ -237,6 +239,101 @@ static int cr_read_tail(struct cr_ctx *ctx)
> return ret;
> }
>
> +static int cr_read_utsns(struct cr_ctx *ctx, struct task_struct *t)
> +{
> + struct cr_hdr_utsns hh;
> + struct uts_namespace *ns;
> + int ret;
> + char *nn = NULL;
> + char *dn = NULL;
> +
> + ret = cr_read_obj_type(ctx, &hh, sizeof(hh), CR_HDR_UTSNS);
> + if (ret < 0)
> + return ret;
> +
> + nn = kmalloc(hh.nodename_len, GFP_KERNEL);
> + if (!nn) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + dn = kmalloc(hh.domainname_len, GFP_KERNEL);
> + if (!dn) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + ret = cr_read_string(ctx, nn, hh.nodename_len);
> + if (ret < 0)
> + goto out;
> +
> + ret = cr_read_string(ctx, dn, hh.domainname_len);
> + if (ret < 0)
> + goto out;
> +
> + ret = sys_unshare(CLONE_NEWUTS);
One thing to note is that this will drive the ns cgroup
bananas. It might still be worthwhile collecting the
flags for all the to-be-unshared namespaces, and then
doing all of the unsharing at once.
Futhermore, you do sys_unshare here, then further down you
do another copy_namespaces(CLONE_NEWUTS)?
Finally, it seems to me every task will unshare(CLONE_NEWUTS),
no? Where is the check done (and stored) for whether this
task has a different utsns from its parent?
I could be misunderstanding your code...
But it seems to me a simpler algorith would be:
Save identifiers for all of the namespaces at the top of the
checkpoint image; have restart create a set of dummy tasks,
enough to contain all of the new namespaces; have each unshare
their namespaces; then, as each real new task is restarted,
manually create a new nsproxy and link it to all of the
required new namespaces.
OR you can stick to trying to use clone(), but I don't think
this patch is doing that right.
> + if (ret)
> + goto out;
> +
> + ns = t->nsproxy->uts_ns;
> + memcpy(ns->name.nodename, nn, hh.nodename_len);
> + memcpy(ns->name.domainname, dn, hh.domainname_len);
> +
> + out:
> + kfree(nn);
> + kfree(dn);
> +
> + return ret;
> +}
> +
> +static int cr_restore_utsns(struct cr_ctx *ctx, int ref)
> +{
> + struct uts_namespace *uts;
> + int ret;
> +
> + uts = cr_obj_get_by_ref(ctx, ref, CR_OBJ_UTSNS);
> + if (uts == NULL) {
> + ret = cr_read_utsns(ctx, current);
> + if (ret < 0)
> + return ret;
> +
> + return cr_obj_add_ref(ctx, current->nsproxy->uts_ns,
> + ref, CR_OBJ_UTSNS, 0);
> + } else if (IS_ERR(uts)) {
> + cr_debug("Failed to get UTS ns from objhash");
> + return PTR_ERR(uts);
> + }
> +
> + ret = copy_namespaces(CLONE_NEWUTS, current);
> + if (ret < 0)
> + return ret;
> +
> + put_uts_ns(current->nsproxy->uts_ns);
> + get_uts_ns(uts);
> + current->nsproxy->uts_ns = uts;
> +
> + return 0;
> +}
> +
> +static int cr_read_namespaces(struct cr_ctx *ctx)
> +{
> + struct cr_hdr_namespaces hh;
> + int ret;
> +
> + ret = cr_read_obj_type(ctx, &hh, sizeof(hh), CR_HDR_NS);
> + if (ret < 0)
> + return ret;
> +
> + ret = cr_restore_utsns(ctx, hh.uts_ref);
> + cr_debug("uts ns: %d\n", ret);
> + if (ret < 0)
> + return ret;
> +
> + /* FIXME: Add more namespaces here */
> +
> + return 0;
> +}
> +
> /* read the task_struct into the current task */
> static int cr_read_task_struct(struct cr_ctx *ctx)
> {
> @@ -298,6 +395,10 @@ static int cr_read_task(struct cr_ctx *ctx)
> goto out;
> ret = cr_read_cpu(ctx);
> cr_debug("cpu: ret %d\n", ret);
> + if (ret < 0)
> + goto out;
> + ret = cr_read_namespaces(ctx);
> + cr_debug("ns: ret %d\n", ret);
>
> out:
> return ret;
> diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
> index 2e99c74..cb62716 100644
> --- a/include/linux/checkpoint.h
> +++ b/include/linux/checkpoint.h
> @@ -75,6 +75,7 @@ extern void cr_ctx_put(struct cr_ctx *ctx);
> enum {
> CR_OBJ_FILE = 1,
> CR_OBJ_INODE,
> + CR_OBJ_UTSNS,
> CR_OBJ_MAX
> };
>
> diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
> index 3addb48..6f29a72 100644
> --- a/include/linux/checkpoint_hdr.h
> +++ b/include/linux/checkpoint_hdr.h
> @@ -48,6 +48,8 @@ enum {
> CR_HDR_TASK,
> CR_HDR_THREAD,
> CR_HDR_CPU,
> + CR_HDR_NS,
> + CR_HDR_UTSNS,
>
> CR_HDR_MM = 201,
> CR_HDR_VMA,
> @@ -177,4 +179,13 @@ struct cr_hdr_fd_pipe {
> __s32 nr_bufs;
> } __attribute__((aligned(8)));
>
> +struct cr_hdr_namespaces {
> + __u32 uts_ref;
> +};
> +
> +struct cr_hdr_utsns {
> + __u32 nodename_len;
> + __u32 domainname_len;
> +};
> +
> #endif /* _CHECKPOINT_CKPT_HDR_H_ */
> --
> 1.5.6.3
>
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