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We have a reproduceable failure of device-mapper when running on the 2.4.29 kernel with XFS. With the XFS logical volume mounted read only, we run a script to continually read a one gigabyte file from the filesystem.
We run a second script that creates 3 snapshots (10 seconds between them), and then waits 30 seconds, and throws them away.
trying to execute lvcreate -sns3 -L5G /dev/H99/v ~ device-mapper ioctl cmd 9 failed: Cannot allocate memory ~ Couldn't load device 'H99-s3'. ~ Problem reactivating origin v
~ device-mapper: Unable to allocate hash table space ~ device-mapper: error adding target to table ~ __alloc_pages: 0-order allocation failed (gfp=0x20/0)
At this point, anything reading from /mnt/H99 (the read only mount point) is deadlocked.
If we run dmsetup resume H99-v, it begins to work again. However, when we tried to unmount it (at least one time), it caused a kernel BUG() in dm-snapshot.c:1064. The output of that kernel oops is in dmesg-dm-0204c.out.
We're running further tests to try and track down exactly what is happening, doing the dd directly from /dev/H99/v seems to work. It looks like the snapshot allocation is failing, and then failing to resume the source volume.
The failure occurs on our system while running ~ repeat-mk-NO-s3.sh and while-dd-from-abcd (see test139scripts-0204c.tgz)
In an environment with minimal services (excluding cron to avoid any of our custom cron actions)and with the xfs fs mounted read-only! (same problem occurs if rw)
our kernel 2429-db0 is built with the following patches ~ xfs-2.4.24-pre1-split-acl.bz2 ~ linux-2.4.28-pre4-devmapper-ioctl.patch ~ linux-2.4.22-VFS-lock.patch
The dmsetup on the test box reports ~ dmsetup --version ~ Library version: 1.00.21-ioctl (2005-01-07) ~ Driver version: 4.1.1 and lvm reports: ~ lvm version ~ LVM version: 2.00.33 (2005-01-07) ~ Library version: 1.00.21-ioctl (2005-01-07) ~ Driver version: 4.1.1 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
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