One way to provide some meaningful information about the reason for which a checkpoint failed, is to write the information as a regular record to the output stream.
Specifically, if an error is detected, then we write a special 'struct ckpt_hdr_error' record to the output file, followed by a string that describes the details of why the checkpoint failed. Signed-off-by: Oren Laadan <[email protected]> --- checkpoint/checkpoint.c | 55 ++++++++++++++++++++++++++++++++++++++- include/linux/checkpoint_hdr.h | 10 ++++++- 2 files changed, 62 insertions(+), 3 deletions(-) diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c index 32a0a8e..7f5c18c 100644 --- a/checkpoint/checkpoint.c +++ b/checkpoint/checkpoint.c @@ -95,6 +95,50 @@ int ckpt_write_string(struct ckpt_ctx *ctx, char *str, int len) return ckpt_write_obj_type(ctx, str, len, CKPT_HDR_STRING); } +/** + * ckpt_write_err - write an object describing an error + * @ctx: checkpoint context + * @fmt: error string format + * @...: error string arguments + */ +int ckpt_write_err(struct ckpt_ctx *ctx, char *fmt, ...) +{ + va_list args; + char str[128]; + char *ptr = NULL; + int len, ret; + + ret = ckpt_write_obj_type(ctx, NULL, sizeof(struct ckpt_hdr), + CKPT_HDR_ERROR); + if (ret < 0) + return ret; + + va_start(args, fmt); + len = vsnprintf(str, 128, fmt, args) + 1; + va_end(args); + + if (len > 128) { + /* doesn't fit on stack, allocate memory */ + ptr = kmalloc(len + 1, GFP_KERNEL); + /* if malloc failed, fallback to truncated string */ + if (ptr) { + va_start(args, fmt); + len = vsnprintf(ptr, len, fmt, args) + 1; + va_end(args); + } else { + len = 128; + printk(KERN_NOTICE "c/r: error message truncated\n"); + } + } + + ckpt_debug("c/r: checkpoint error: %s\n", ptr ? : str); + ret = ckpt_write_string(ctx, ptr ? : str, len); + + kfree(ptr); + return ret; +} + + /*********************************************************************** * Checkpoint */ @@ -198,8 +242,11 @@ static int may_checkpoint_task(struct task_struct *t, struct ckpt_ctx *ctx) return -EPERM; /* verify that the task is frozen (unless self) */ - if (t != current && !frozen(t)) + if (t != current && !frozen(t)) { + ckpt_write_err(ctx, "task %d(%s) not frozen\n", + task_pid_vnr(t), t->comm); return -EBUSY; + } /* FIX: add support for ptraced tasks */ if (task_ptrace(t)) @@ -436,8 +483,11 @@ static int get_container(struct ckpt_ctx *ctx, pid_t pid) ctx->root_init = is_container_init(task); /* FIX: does this error code makes sense here ? */ - if (!(ctx->flags & CHECKPOINT_SUBTREE) && !ctx->root_init) + if (!(ctx->flags & CHECKPOINT_SUBTREE) && !ctx->root_init) { + ckpt_write_err(ctx, "task %d(%s) not container init\n", + task_pid_vnr(task), task->comm); return -EBUSY; + } return 0; @@ -501,6 +551,7 @@ int do_checkpoint(struct ckpt_ctx *ctx, pid_t pid) if (!(ctx->flags & CHECKPOINT_SUBTREE)) { /* verify that all objects are contained (no leaks) */ if (!ckpt_obj_contained(ctx)) { + ckpt_write_err(ctx, "container is not isolated\n"); ret = -EBUSY; goto out; } diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h index 0e15f3f..058412c 100644 --- a/include/linux/checkpoint_hdr.h +++ b/include/linux/checkpoint_hdr.h @@ -73,9 +73,17 @@ enum { CKPT_HDR_IPC_MSG_MSG, CKPT_HDR_IPC_SEM, - CKPT_HDR_TAIL = 5001 + CKPT_HDR_TAIL = 5001, + + CKPT_HDR_ERROR = 9999 }; +/* error report */ +struct ckpt_hdr_error { + struct ckpt_hdr h; + /* followed by the error string */ +} __attribute__((aligned(8))); + /* shared objrects (objref) */ struct ckpt_hdr_objref { struct ckpt_hdr h; -- 1.5.4.3 _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
