On Fri, 29 Sep 2006 00:13:38 +0200
"Rafael J. Wysocki" <[email protected]> wrote:
> To be able to use swap files as suspend storage from the userland suspend
> tools we need an additional ioctl() that will allow us to provide the kernel
> with both the swap header's offset and the identification of the resume
> partition.
>
> The new ioctl() should be regarded as a replacement for the
> SNAPSHOT_SET_SWAP_FILE ioctl() that from now on will be considered as
> obsolete, but has to stay for backwards compatibility of the interface.
>
> +
> +/*
> + * This structure is used to pass the values needed for the identification
> + * of the resume swap area from a user space to the kernel via the
> + * SNAPSHOT_SET_SWAP_AREA ioctl
> + */
> +struct resume_swap_area {
> + u_int16_t dev;
> + loff_t offset;
> +} __attribute__((packed));
>
hmm. Asking the compiler to pack 16-bit and 64-bit quantities in this
manner is a bit risky. I guess it'll do the right thing, consistently,
across all compiler versions and vendors and 32-bit-on-64-bit-kernel, etc.
But from a defensiveness/paranoia POV it'd be better to use a u32 here, I
suspect. (Will access to that loff_t cause an alignment trap on ia64? Any
other CPUs? Dunno).
> #define PMOPS_PREPARE 1
> #define PMOPS_ENTER 2
> Index: linux-2.6.18-mm1/kernel/power/user.c
> ===================================================================
> --- linux-2.6.18-mm1.orig/kernel/power/user.c
> +++ linux-2.6.18-mm1/kernel/power/user.c
> @@ -343,6 +343,37 @@ OutS3:
> }
> break;
>
> + case SNAPSHOT_SET_SWAP_AREA:
> + if (data->bitmap) {
> + error = -EPERM;
> + } else {
> + struct resume_swap_area swap_area;
> + dev_t swdev;
> +
> + error = copy_from_user(&swap_area, (void __user *)arg,
> + sizeof(struct resume_swap_area));
> + if (error) {
> + error = -EFAULT;
> + break;
> + }
> +
> + /*
> + * User space encodes device types as two-byte values,
> + * so we need to recode them
> + */
Really? stat() uses unsigned long and stat64() uses unsigned long long dev_t.
> + swdev = old_decode_dev(swap_area.dev);
> + if (swdev) {
> + offset = swap_area.offset;
> + data->swap = swap_type_of(swdev, offset);
> + if (data->swap < 0)
> + error = -ENODEV;
> + } else {
> + data->swap = -1;
> + error = -EINVAL;
> + }
> + }
> + break;
> +
> default:
> error = -ENOTTY;
But I wonder if we need to pass the device identified into this ioctl at
all. What device is the ioctl() against? ie: what do `filp' and `inode'
point at? If it's /dev/hda1 then everything we need is right there, is it
not?
ohshit, it's a miscdevice. I wonder if it would have defined all this
stuff to be operations against the blockdev. Perhaps not.
Well anyway. It might be neater to require that userspace open /dev/hda1
and pass in the fd to this ioctl. But this code will never be neat, so
whatever.
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