[Devel] Re: [BUG][cryo] Create file on restart ?

[Serge E. Hallyn]

Quoting sukadev at us.ibm.com (sukadev at us.ibm.com):
> 
> cryo does not (cannot ?) recreate files if the application created

I think that's for the best.

Don't you?

The most we should do is make sure cryo has a clear enough error
message.

-serge

> a file before checkpoint and the file does not exist at the time
> of restart.
> 
> Note that the 'flags' field in '/proc/$pid/fdinfo/$fd' will not
> have the O_CREAT (or O_TRUNC, O_EXCL, O_NOCTTY) flags. These
> are cleared in __dentry_open()).
> 
> At the time of restart, is there a way for cryo to know that the
> file must be created ?
> 
> To reproduce:
> 	- run following program, 
> 	- checkpoint after the first printf
> 	- rm /tmp/foo1
> 	- restart	# fails to open file during restart
> 
> ---
> #include <stdio.h>
> #include <unistd.h>
> #include <errno.h>
> #include <sys/fcntl.h>
> 
> main()
> {
> 	int fd;
> 	int i;
> 	char *buf = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
> 
> 	fd = open("/tmp/foo1", O_RDWR|O_CREAT|O_TRUNC, 0666);
> 
> 	if (fd < 0) {
> 		perror("open");
> 		exit(1);
> 	}
> 	printf("%d: Opened '/tmp/foo1', fd %d\n", getpid(), fd);
> 	
> 	for (i = 0; i < strlen(buf); i++) {
> 		if (write(fd, &buf[i], 1) < 0) {
> 			printf("Error %d writing %c to file, i %d\n",
> 					errno, buf[i], i);
> 			exit(1);
> 		}
> 		printf("%d: i %d, wrote %c\n", getpid(), i, buf[i]);
> 		sleep(2);
> 	}
> }
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