Il Thu, Nov 09, 2006 at 10:35:13PM +0100, Rafael J. Wysocki ha scritto:
> On Thursday, 9 November 2006 22:30, Luca Tettamanti wrote:
> > On 11/9/06, Rafael J. Wysocki <[EMAIL PROTECTED]> wrote:
> > > I think that the swap header need not be continuous. This actually also
> > > follows from the sys_swapon() code which reads one page from the file
> > > using its mapping. It looks like setup_swap_extents() omits the first
> > > continuous PAGE_SIZE "block" just in case it contains the header, but
> > > the swap-handling will work even if it doesn't.
> > >
> > > However, in case this happens, swsusp and s2disk/s2both won't be
> > > able to use the swap file for the suspend, because swap_type_of() will
> > > fail.
> > >
> > > Now if that really is what happens (could you please verify with your
> > > setup?),
> >
> > It seems so. What I see is the following:
> >
> > 0x0000-0x1000: header, not contiguous
> > 0x1000-0x2000: nothing, this page is left empty
> > 0x2000-EOF: swap data
> >
> > > it would be nice if your program detected such situations and informed the
> > > user that the swap file could not be used.
> >
> > Basically:
> > - find the first block of the swapfile
> > - check that there's a contiguous PAGE_SIZE cluster
> > - check signature
>
> ... and print the number if everything fits.
Yeah :)
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <linux/fs.h>
#include <errno.h>
#define SWAP_SIG "SWAPSPACE2"
int main(int argc, char **argv) {
int block, last_block, first_block, blocks_per_page;
int size, blk_size;
int fd;
int i;
struct stat stat;
unsigned char buf[10];
int err = 0;
int const page_size = getpagesize();
if (argc < 2)
return EINVAL;
fd = open(argv[1], O_RDONLY);
if (fd < 0) {
perror("open()");
return ENOENT;
}
/* Check swap signature */
if (lseek(fd, page_size - 10, SEEK_SET) == (off_t)-1) {
err = errno;
perror("lseek()");
goto out;
}
i = read(fd, buf, 10);
if (i == -1) {
err = errno;
perror("read()");
goto out;
} else if (i < 10) {
fprintf(stderr, "Failed to read swap signature: file is too
short.\n");
err = EINVAL;
goto out;
}
if (memcmp(buf, SWAP_SIG, 10)) {
fprintf(stderr, "Swap signature not found.\n");
err = EINVAL;
goto out;
}
if (fstat(fd, &stat)) {
err = errno;
perror("fstat()");
goto out;
}
if (ioctl(fd, FIGETBSZ, &blk_size)) {
err = errno;
perror("ioctl(FIGETBSZ) failed");
goto out;
}
blocks_per_page = page_size / blk_size;
/* Check that the header is contiguous */
last_block = 0;
first_block = 0;
size = 0;
for (i = 0; i < blocks_per_page; i++) {
block = i;
if (ioctl(fd, FIBMAP, &block)) {
err = errno;
perror("ioctl(FIBMAP) failed");
goto out;
}
if (last_block && block != last_block + 1)
break;
if (!first_block)
first_block = block;
size += blk_size;
last_block = block;
}
if (size < page_size) {
fprintf(stderr, "Swapfile header is not contiguous and cannot
be used"
"for suspension.\n");
err = EINVAL;
} else
printf("resume offset = %d\n", first_block * blk_size /
page_size);
out:
close(fd);
return err;
}
Luca
--
"Perch� � cos� che ti frega, la vita. Ti piglia quando hai ancora l'anima
addormentata e ti semina dentro un'immagine, o un odore, o un suono che
poi non te lo togli pi�. E quella l� era la felicit�."
-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________
Suspend-devel mailing list
Suspend-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/suspend-devel
