linux-kernel - Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy)

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Date:	Thu, 26 Apr 2007 12:40:52 +0200
From:	Pavel Machek <pavel@....cz>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Con Kolivas <kernel@...ivas.org>,
	suspend2-devel@...ts.suspend2.net, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy)

Hi!

> > The interface isn't even 64/32-bit compatible...
> 
> Which parts?
> 
> ioctl(AVAIL_SWAP,
> 	...hmm, is this the one you are complaining about? It returns
> 	loff_t through a pointer.  Maybe there's another interface
> 	that can return available swap, and we should use that,
>	 instead?

loff_t is 64bit on i386, so I do not see immediate problem here, but
maybe we should just explicitely pass u64?

> ioctl(GET_SWAP_PAGE,
> 	returns sector_t through a pointer. NOt sure if that's good
> 	idea, either.

Ok, that's very bad idea, because sector_t can be 32-bit or 64-bit,
depending on CONFIG_LBD. We need to use u64 here.

> ioctl(SET_SWAP_FILE,
> 	does old_decode_dev(arg). Is that ok?
> 
> ioctl(SET_SWAP_AREA,
> 	shares struct resume_swap_area between user and kernel. I
> 	guess that's bad..?

struct resume_swap_area {
        loff_t offset;
        u_int32_t dev;
} __attribute__((packed));

...I guess we should change loff_t -> u64 and problem is solved?

Old_decode_dev takes u16. That sucks for majors/minors > 256, but
fortunately those are not common.

Does this seem to help?
									Pavel

diff --git a/kernel/power/power.h b/kernel/power/power.h
index eb461b8..dc13af5 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -114,7 +114,7 @@ extern int snapshot_image_loaded(struct 
  * SNAPSHOT_SET_SWAP_AREA ioctl
  */
 struct resume_swap_area {
-	loff_t offset;
+	u_int64_t offset;
 	u_int32_t dev;
 } __attribute__((packed));
 
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 558e18e..d0730c1 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -215,8 +215,7 @@ static int snapshot_ioctl(struct inode *
 {
 	int error = 0;
 	struct snapshot_data *data;
-	loff_t avail;
-	sector_t offset;
+	u64 avail, offset;
 
 	if (_IOC_TYPE(cmd) != SNAPSHOT_IOC_MAGIC)
 		return -ENOTTY;
@@ -286,7 +285,7 @@ static int snapshot_ioctl(struct inode *
 	case SNAPSHOT_AVAIL_SWAP:
 		avail = count_swap_pages(data->swap, 1);
 		avail <<= PAGE_SHIFT;
-		error = put_user(avail, (loff_t __user *)arg);
+		error = put_user(avail, (u64 __user *)arg);
 		break;
 
 	case SNAPSHOT_GET_SWAP_PAGE:
@@ -304,7 +303,7 @@ static int snapshot_ioctl(struct inode *
 		offset = alloc_swapdev_block(data->swap, data->bitmap);
 		if (offset) {
 			offset <<= PAGE_SHIFT;
-			error = put_user(offset, (sector_t __user *)arg);
+			error = put_user(offset, (u64 __user *)arg);
 		} else {
 			error = -ENOSPC;
 		}

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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