Messages in this thread | | | From | Michael Buesch <> | Subject | sys_swapoff() symlink bug | Date | Mon, 15 Mar 2004 19:52:05 +0100 |
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Hi,
The following script demonstrates a bug in the swapon/swapoff syscalls in the latest 2.6 kernel (I did not check 2.4).
#/bin/sh # 3:12 is hda12, which is a swap partition on my system. SWAP_MAJOR=3 SWAP_MINOR=12 echo "running swaps:" cat /proc/swaps echo "--" mkdir /testdev mknod /testdev/testnode b $SWAP_MAJOR $SWAP_MINOR ln -s /testdev/testnode /testdev/testlink swapon /testdev/testlink echo "swapon returned $?" echo "running swaps:" cat /proc/swaps echo "--" swapoff /testdev/testdev echo "swapoff returned $?" echo "running swaps:" cat /proc/swaps echo "--" rm -Rf /testdev
The output of this script on my system is:
running swaps: - -- swapon returned 0 running swaps: Filename Type Size Used Priority /testdev/testnode partition 976712 0 -32 - -- swapoff returned 255 running swaps: Filename Type Size Used Priority /testdev/testnode partition 976712 0 -32 - --
As you can see the swapoff fails, because it is called on the node instead of the symlink that was used for swapon. I think this should not fail.
The code that fails to detect, that the symlink _is_ actually the same swapspace as the node itself, is mm/swapfile.c:1038
for (type = swap_list.head; type >= 0; type = swap_info[type].next) { p = swap_info + type; if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
/* I'm not really sure about what we should check here, instead * of f_mapping to detect it. */ if (p->swap_file->f_mapping == mapping) break; } prev = type; }
- -- Regards Michael Buesch [ http://www.tuxsoft.de.vu ]
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