Il Thu, Nov 09, 2006 at 12:38:51AM +0100, Rafael J. Wysocki ha scritto:
> On Thursday, 9 November 2006 00:32, Luca Tettamanti wrote:
> > On 11/8/06, Rafael J. Wysocki <[EMAIL PROTECTED]> wrote:
> > > Hi,
> > >
> > > On Wednesday, 8 November 2006 18:58, Luca wrote:
> > > > I've been working on a small program to find the first valid block of a
> > > > swapfile. If I understand it correctly we need the first contiguos
> > > > cluster
> > > > of blocks (not counting the header) which is at least PAGE_SIZE big and
> > > > the starting block must be page aligned.
> > > > The block number must then be converted in an offset from the start of
> > > > the device and the number must be expressed in multiple of PAGE_SIZE.
> > > >
> > > > This is what I've come up with ;)
> > >
> > > It doesn't look bad, but you shouldn't skip the header, actually. The
> > > header
> > > is what we need. ;-)
> >
> > Oh, right.. you print the offset of page_no == 0. Hum, I think I don't
> > understand the layout of a swapfile then; reading swapfile.c I see
> > that even the header should be a PAGE_SIZE continuous block, but I
> > have test cases where the header is not contiguous on disk (ext2,
> > 1024b per block, with artificial fragmentation) - which is why I
> > thought that first-page-after-header was needed.
>
> Ouch, that's bad. The swsusp (and ours) swap-writing code will corrupt
> the filesystem in such a case, because it assumes the header to be
> continuous.
>
> I think we have to understand your test cases at this point. Can you please
> post some numbers?
Ok, ext2 FS, created with 'mke2fs -I 1024', mounted with loop device.
I've created a fragmented swapfile like this:
dd if=/dev/zero of=swapfile bs=1k count=1
dd if=/dev/zero of=frag bs=1k count=2
dd if=/dev/zero of=swapfile oflag=append conv=notrunc bs=1M count=10
debugfs: stat /swapfile
Inode: 12 Type: regular Mode: 0644 Flags: 0x0 Generation:
1271405748
User: 0 Group: 0 Size: 10485760
File ACL: 0 Directory ACL: 0
Links: 1 Blockcount: 20562
Fragment: Address: 0 Number: 0 Size: 0
ctime: 0x45535207 -- Thu Nov 9 17:06:31 2006
atime: 0x45535217 -- Thu Nov 9 17:06:47 2006
mtime: 0x45535207 -- Thu Nov 9 17:06:31 2006
BLOCKS:
(0):1998, (1-11):2001-2011, (IND):2012, (12-267):2013-2268, (DIND):2269,
(IND):2270, (268-523):2271-2526, (IND):2527...etc
The signature should in the first page (at PAGE_SIZE - 10), but in my
case I see the signature exactly at offset (4096 - 10)
0000ff0: 0000 0000 0000 5357 4150 5350 4143 4532 ......SWAPSPACE2
even if the first 4 blocks are not contiguous (block 1998 is not even
aligned to PAGE_SIZE!).
The loop device may be have a bad influence on the test case, I don't
have a FS with blocksize < 4096.
Luca
--
"It is more complicated than you think"
-- The Eighth Networking Truth from RFC 1925
-------------------------------------------------------------------------
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
