Re: Back to the future.

Pavel Machek
2007-04-26T22:43:09Z

Hi!

> I'd really suggest _just_ the "full image". Nothing else is probably ever
> worth supporting. Your "snapshot to disk" wouldn't be _quite_ as simple as
> "echo disk > /sys/power/state", but it should not necessarily be much
> worse than
>
> snapshot_kernel | gzip -9 > /dev/snapshot

Yep, we "freeze too much", so we can't just use the shell and pipe
it. Too bad.

218 int write_image(char *resume_dev_name)
219 {
220 static struct swap_map_handle handle;
221 struct swsusp_info *header;
222 unsigned long start;
223 int fd;
224 int error;
225
226 fd = open(resume_dev_name, O_RDWR | O_SYNC);
227 if (fd < 0) {
228 printf("suspend: Could not open resume device\n");
229 return error;
230 }
231 error = read(dev, buffer, PAGE_SIZE);
232 if (error < PAGE_SIZE)
233 return error < 0 ? error : -EFAULT;
234 header = (struct swsusp_info *)buffer;
235 if (!enough_swap(header->pages)) {
236 printf("suspend: Not enough free swap\n");
237 return -ENOSPC;
238 }
239 error = init_swap_writer(&handle, fd);
240 if (!error) {
241 start = handle.cur_swap;
242 error = swap_write_page(&handle, header);
243 }
244 if (!error)
245 error = save_image(&handle, header->pages - 1);
246 if (!error) {
247 flush_swap_writer(&handle);
248 printf( "S" );
249 error = mark_swap(fd, start);
250 printf( "|\n" );
251 }
252 fsync(fd);
253 close(fd);
254 return error;
255 }

This is basically the loop above, made complex by the fact that we do
not want to have separate partition for snapshot; we just want to
reuse free space in swap partition.

I think you've just invented uswsusp.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html