On Tue, 3 Mar 2009, Karel Zak wrote:
> > On Thu, Jan 22, 2009 at 04:46:57PM +0000, Hugh Dickins wrote:
> > Though your swapon may mkswap for suspend reasons: hmm, wouldn't it
> > do very much better just to rewrite the swap signature, than exec
> > mkswap - maybe nobody ever uses the badpages list, but it really
> > should be respected.
>
> CC: Hugh Dickins <hugh@xxxxxxxxxxx>
> Signed-off-by: Karel Zak <kzak@xxxxxxxxxx>
> ---
Thanks a lot, Karel: this is a great improvement - seeing it
implemented makes me feel all the more strongly that it was needed.
One small point: if the lseek or write in swap_rewrite_signature()
were to fail (neither seems likely), then there's no error message
to the user that it failed.
Hugh
> mount/swapon.c | 44 +++++++++++++++++++++++++++++++++-----------
> 1 files changed, 33 insertions(+), 11 deletions(-)
>
> diff --git a/mount/swapon.c b/mount/swapon.c
> index 1c337c2..d61ff74 100644
> --- a/mount/swapon.c
> +++ b/mount/swapon.c
> @@ -48,6 +48,9 @@ enum {
> SIG_SWSUSPEND
> };
>
> +#define SWAP_SIGNATURE "SWAPSPACE2"
> +#define SWAP_SIGNATURE_SZ (sizeof(SWAP_SIGNATURE) - 1)
> +
> int all;
> int priority = -1; /* non-prioritized swap by default */
>
> @@ -229,6 +232,30 @@ swap_reinitialize(const char *device) {
> }
>
> static int
> +swap_rewrite_signature(const char *devname, unsigned int pagesize)
> +{
> + int fd, rc = -1;
> +
> + fd = open(devname, O_WRONLY);
> + if (fd == -1) {
> + warn(_("%s: open failed"), devname);
> + return -1;
> + }
> +
> + if (lseek(fd, pagesize - SWAP_SIGNATURE_SZ, SEEK_SET) < 0)
> + goto err;
> +
> + if (write(fd, (void *) SWAP_SIGNATURE,
> + SWAP_SIGNATURE_SZ) != SWAP_SIGNATURE_SZ)
> + goto err;
> +
> + rc = 0;
> +err:
> + close(fd);
> + return rc;
> +}
> +
> +static int
> swap_detect_signature(const char *buf, int *sig)
> {
> if (memcmp(buf, "SWAP-SPACE", 10) == 0 ||
> @@ -271,9 +298,9 @@ swap_get_header(int fd, int *sig, unsigned int *pagesize)
> continue;
> /* the smallest swap area is PAGE_SIZE*10, it means
> * 40k, that's less than MAX_PAGESIZE */
> - if (datasz < (page - 10))
> + if (datasz < (page - SWAP_SIGNATURE_SZ))
> break;
> - if (swap_detect_signature(buf + page - 10, sig)) {
> + if (swap_detect_signature(buf + page - SWAP_SIGNATURE_SZ, sig)) {
> *pagesize = page;
> break;
> }
> @@ -318,7 +345,6 @@ swap_get_size(const char *hdr, const char *devname, unsigned int pagesize)
> static int
> swapon_checks(const char *special)
> {
> - int reinitialize = 0;
> struct stat st;
> int fd = -1, sig;
> char *hdr = NULL;
> @@ -384,7 +410,8 @@ swapon_checks(const char *special)
> warn(_("%s: swap format pagesize does not match."
> " Reinitializing the swap."),
> special);
> - reinitialize = 1;
> + if (swap_reinitialize(special) < 0)
> + goto err;
> }
> } else if (sig == SIG_SWSUSPEND) {
> /* We have to reinitialize swap with old (=useless) software suspend
> @@ -392,20 +419,15 @@ swapon_checks(const char *special)
> * corruption the next time an attempt at unsuspending is made.
> */
> warnx(_("%s: software suspend data detected. "
> - "Reinitializing the swap."),
> + "Rewriting the swap signature."),
> special);
> - reinitialize = 1;
> - }
> -
> - if (reinitialize) {
> - if (swap_reinitialize(special) < 0)
> + if (swap_rewrite_signature(special, pagesize) < 0)
> goto err;
> }
>
> free(hdr);
> close(fd);
> return 0;
> -
> err:
> if (fd != -1)
> close(fd);
> --
> 1.6.0.6
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