[Bug 366397] [NEW] swapon hangs when using file on kernels 2.6.28-13 and 2.6.28-11 but works perfect on kernel 2.6.27.11

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I have tested a lot, changing VFAT (FAT32) umask, uid and gid on /etc/fstab, allways happens the same:
On kernels 2.6.28.13 and 2.6.28.11 swapon /media/SWAP/pagefile.sys hags, so at boot time it stops and Ctrl+Alt+Sup is only way to continue
On kernel 2.6.27-11 swapon /media/SWAP/pagefile.sys works perfectly.

Since i can select what kernel to load thanks to grub i can do the next
test with this results:

-Boot selecting kernel 2.6.28-13 -> swapon hangs the PC at boot time when activating swap area on file.
-Reboot with Ctrl+Alt+Sup
-Boot selecting kernel 2.6.28-13 -> swapon hangs the PC at boot time when activating swap area on file.
-Reboot with Ctrl+Alt+Sup
... so on as i select kernel 2.6.28-13 ...

-Boot selecting kernel 2.6.28-11 -> swapon hangs the PC at boot time when activating swap area on file.
-Reboot with Ctrl+Alt+Sup
-Boot selecting kernel 2.6.28-11 -> swapon hangs the PC at boot time when activating swap area on file.
-Reboot with Ctrl+Alt+Sup
... so on as i select kernel 2.6.28-11 ...

-Boot selecting kernel 2.6.27-11 -> swapon works perfect at boot time and activate swap area on file.
-Shutdown Ubuntu 9.04 normaly

-Boot selecting kernel 2.6.28-11 -> swapon hangs the PC at boot time when activating swap area on file.
-Reboot with Ctrl+Alt+Sup
-Boot selecting kernel 2.6.28-11 -> swapon hangs the PC at boot time when activating swap area on file.
-Reboot with Ctrl+Alt+Sup
... so on as i select kernel 2.6.28-11 ...

-Boot selecting kernel 2.6.28-11 -> swapon hangs the PC at boot time when activating swap area on file.
-Reboot with Ctrl+Alt+Sup
-Boot selecting kernel 2.6.28-11 -> swapon hangs the PC at boot time when activating swap area on file.
-Reboot with Ctrl+Alt+Sup
... so on as i select kernel 2.6.28-11 ...

-Boot selecting kernel 2.6.27-11 -> swapon works perfect at boot time and activate swap area on file.
-Shutdown Ubuntu 9.04 normaly

So i can see it only occurs when kernel 2.6.28-11 is selected and also
when kernel 2.6.28-13 is selected.

Also i have commented swapon line, so i can boot with kernels 2.6.28-11
and 2.6.28-13, then i go to a prompt and type:


[Booting 2.6.28-13]
$uname -s -n -r -m
Linux ubuntu 2.6.28-13-generic i686
$sudo swapon -s
[sudo] password for usuario: 
Filename				Type		Size	Used	Priority
$sudo mkswap /media/SWAP/pagefile.sys
$sudo swapon /media/SWAP/pagefile.sys
<--< It hangs on swapon and console must be terminated, unable to kill swapon process, neither with kill -9

[Booting 2.6.28-11]
$uname -s -n -r -m
Linux ubuntu 2.6.28-11-generic i686
$sudo swapon -s
[sudo] password for usuario: 
Filename				Type		Size	Used	Priority
$sudo mkswap /media/SWAP/pagefile.sys
$sudo swapon /media/SWAP/pagefile.sys
<--< It hangs on swapon and console must be terminated, unable to kill swapon process, neither with kill -9

If i do the same but selecting kernel 2.6.27-11 at boot time i get:
$uname -s -n -r -m
Linux ubuntu 2.6.27-11-generic i686
$sudo swapon -s
[sudo] password for usuario: 
Filename				Type		Size	Used	Priority
$sudo mkswap /media/SWAP/pagefile.sys
$sudo swapon /media/SWAP/pagefile.sys
$sudo swapon -s
Filename				Type		Size	Used	Priority
/media/SWAP/pagefile.sys                file		4186104	0	-1
$

Obviously /media/SWAP is mounted as on both cases as:
/dev/sda1 on /media/SWAP type vfat (rw,utf8,umask=007,uid=0,gid=0)

Also the file pagefile.sys is defragmented.

I have also done the next just to avoid any possible of being the content of the file:
$sudo umount /media/SWAP
$sudo mkfs.vfat -F 32 -n PAGEFILE -v /dev/sda1
$sudo mount /dev/sda1 /media/SWAP
$sudo dd bs=1MB cont=4081 if=/dev/zero of=/media/SWAP/pagefile.sys
$sudo mkswap /media/SWAP/pagefiles.sys
$swapon /media/SWAP/pagefile.sys
If i do this on kernel 2.6.27-11 works perfect but if done in kernels 2.6.28-13 and 2.6.28-11 it hangs on swapon

I think it is a kernel bug.

Also i had tried to put sync command between commands, but same occurs
swapon hangs on kernels 2.6.28-13 and 2.6.28-11 but on kernel 2.6.27-11
works fine.

Hope this info could help to solve such bug.

Thanks.

P.D.: If i had the oportunity i will check exactly the same, but with a
file size exactly of 4GB (4096MB) instead of actual size of 4081MB, it
is supposed not to affect, but who knows!

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

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swapon hangs when using file on kernels 2.6.28-13 and 2.6.28-11 but works perfect on kernel 2.6.27.11
https://bugs.launchpad.net/bugs/366397
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