Now we can do "external" checkpoint, i.e. act on another task. sys_checkpoint() now looks up the target pid (in our namespace) and checkpoints that corresponding task. That task should be the root of a container, unless CHECKPOINT_SUBTREE flag is given.
sys_restart() remains the same, as the restart is always done in the context of the restarting task. Changelog[v16]: - Use CHECKPOINT_SUBTREE to allow subtree (partial container) Changelog[v14]: - Refuse non-self checkpoint if target task isn't frozen Changelog[v12]: - Replace obsolete ckpt_debug() with pr_debug() Changelog[v11]: - Copy contents of 'init->fs->root' instead of pointing to them Changelog[v10]: - Grab vfs root of container init, rather than current process Signed-off-by: Oren Laadan <[email protected]> --- checkpoint/checkpoint.c | 79 +++++++++++++++++++++++++++++++++++++- checkpoint/restart.c | 4 +- checkpoint/sys.c | 6 +++ include/linux/checkpoint_types.h | 2 + 4 files changed, 87 insertions(+), 4 deletions(-) diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c index a346b7e..086f2d9 100644 --- a/checkpoint/checkpoint.c +++ b/checkpoint/checkpoint.c @@ -12,6 +12,9 @@ #define CKPT_DFLAG CKPT_DSYS #include <linux/version.h> +#include <linux/sched.h> +#include <linux/freezer.h> +#include <linux/ptrace.h> #include <linux/time.h> #include <linux/fs.h> #include <linux/file.h> @@ -245,23 +248,95 @@ static int checkpoint_write_tail(struct ckpt_ctx *ctx) return ret; } +static int may_checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t) +{ + if (t->state == TASK_DEAD) { + pr_warning("c/r: task %d is TASK_DEAD\n", task_pid_vnr(t)); + return -EAGAIN; + } + + if (!ptrace_may_access(t, PTRACE_MODE_READ)) { + __ckpt_write_err(ctx, "access to task %d (%s) denied", + task_pid_vnr(t), t->comm); + return -EPERM; + } + + /* verify that the task is frozen (unless self) */ + if (t != current && !frozen(t)) { + __ckpt_write_err(ctx, "task %d (%s) is not frozen", + task_pid_vnr(t), t->comm); + return -EBUSY; + } + + /* FIX: add support for ptraced tasks */ + if (task_ptrace(t)) { + __ckpt_write_err(ctx, "task %d (%s) is ptraced", + task_pid_vnr(t), t->comm); + return -EBUSY; + } + + return 0; +} + +static int get_container(struct ckpt_ctx *ctx, pid_t pid) +{ + struct task_struct *task = NULL; + struct nsproxy *nsproxy = NULL; + int ret; + + ctx->root_pid = pid; + + read_lock(&tasklist_lock); + task = find_task_by_vpid(pid); + if (task) + get_task_struct(task); + read_unlock(&tasklist_lock); + + if (!task) + return -ESRCH; + + ret = may_checkpoint_task(ctx, task); + if (ret) { + ckpt_write_err(ctx, NULL); + put_task_struct(task); + return ret; + } + + rcu_read_lock(); + nsproxy = task_nsproxy(task); + get_nsproxy(nsproxy); + rcu_read_unlock(); + + ctx->root_task = task; + ctx->root_nsproxy = nsproxy; + + return 0; +} + /* setup checkpoint-specific parts of ctx */ static int init_checkpoint_ctx(struct ckpt_ctx *ctx, pid_t pid) { struct fs_struct *fs; + int ret; ctx->root_pid = pid; + ret = get_container(ctx, pid); + if (ret < 0) + return ret; + /* * assume checkpointer is in container's root vfs * FIXME: this works for now, but will change with real containers */ - fs = current->fs; + task_lock(ctx->root_task); + fs = ctx->root_task->fs; read_lock(&fs->lock); ctx->fs_mnt = fs->root; path_get(&ctx->fs_mnt); read_unlock(&fs->lock); + task_unlock(ctx->root_task); return 0; } @@ -276,7 +351,7 @@ int do_checkpoint(struct ckpt_ctx *ctx, pid_t pid) ret = checkpoint_write_header(ctx); if (ret < 0) goto out; - ret = checkpoint_task(ctx, current); + ret = checkpoint_task(ctx, ctx->root_task); if (ret < 0) goto out; ret = checkpoint_write_tail(ctx); diff --git a/checkpoint/restart.c b/checkpoint/restart.c index d3d6c5e..ca33539 100644 --- a/checkpoint/restart.c +++ b/checkpoint/restart.c @@ -352,7 +352,7 @@ static int restore_read_tail(struct ckpt_ctx *ctx) } /* setup restart-specific parts of ctx */ -static int init_restart_ctx(struct ckpt_ctx *ctx) +static int init_restart_ctx(struct ckpt_ctx *ctx, pid_t pid) { return 0; } @@ -361,7 +361,7 @@ int do_restart(struct ckpt_ctx *ctx, pid_t pid) { int ret; - ret = init_restart_ctx(ctx); + ret = init_restart_ctx(ctx, pid); if (ret < 0) return ret; ret = restore_read_header(ctx); diff --git a/checkpoint/sys.c b/checkpoint/sys.c index 7bf70e4..c809120 100644 --- a/checkpoint/sys.c +++ b/checkpoint/sys.c @@ -12,6 +12,7 @@ #define CKPT_DFLAG CKPT_DSYS #include <linux/sched.h> +#include <linux/nsproxy.h> #include <linux/kernel.h> #include <linux/syscalls.h> #include <linux/fs.h> @@ -173,6 +174,11 @@ static void ckpt_ctx_free(struct ckpt_ctx *ctx) path_put(&ctx->fs_mnt); ckpt_pgarr_free(ctx); + if (ctx->root_nsproxy) + put_nsproxy(ctx->root_nsproxy); + if (ctx->root_task) + put_task_struct(ctx->root_task); + kfree(ctx); } diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h index a0ea5f6..4369f90 100644 --- a/include/linux/checkpoint_types.h +++ b/include/linux/checkpoint_types.h @@ -28,6 +28,8 @@ struct ckpt_ctx { int crid; /* unique checkpoint id */ pid_t root_pid; /* container identifier */ + struct task_struct *root_task; /* container root task */ + struct nsproxy *root_nsproxy; /* container root nsproxy */ unsigned long kflags; /* kerenl flags */ unsigned long uflags; /* user flags */ -- 1.6.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
