Chris:
I can consistently reproduce I/O stalls when running fstress (as found
in Autotest) against a six volume btrfs filesystem mounted without
options. The volumes are independent disks from RAID controllers, and
the test systems are eight core Intel and AMD machines running current
btrfs-unstable.
The stalls occur at variable times into the runs. The affected system
ceases to do I/O while the kernel continues to report some percentage of
iowait, and negligible utilization otherwise. fstress does not complete.
On one occasion, I also caught a warning early in the run which did not
appear to affect the progress fstress made, as I/O continued for some
minutes until the system stalled once more. This behavior appears to be
rare (1 in 6 trials).
Please note that the fstress test passes for single device btrfs
filesystems (many trials).
Particulars follow for both cases, including huge web-accessible
backtraces - please let me know if you'd like more information, etc.
Thanks,
Eric
commit: 755efdc3c4d3b42d5ffcef0f4d6e5b37ecd3bf21
uname -a: Linux bl465cb.lnx.usa.hp.com 2.6.28-btrfs-unstable #1 SMP Thu
Jan 8 14:34:46 EST 2009 x86_64 GNU/Linux
mounted as: /dev/cciss/c1d5 on /mnt type btrfs (rw)
btrfs-show:
Label: none uuid: 6c4ea7e8-1e68-4fb6-aa99-254a67ea81f2
Total devices 6 FS bytes used 4.09GB
devid 4 size 68.33GB used 3.00GB path /dev/cciss/c1d3
devid 1 size 68.33GB used 2.02GB path /dev/cciss/c1d0
devid 5 size 68.33GB used 2.01GB path /dev/cciss/c1d4
devid 2 size 68.33GB used 2.00GB path /dev/cciss/c1d1
devid 6 size 68.33GB used 2.01GB path /dev/cciss/c1d5
devid 3 size 68.33GB used 3.00GB path /dev/cciss/c1d2
Btrfs v0.16-37-gb8271dc
sysrq-w backtraces:
http://free.linux.hp.com/~enw/fstress-multi-iohang-010809/sysrq-w-backtraces
http://free.linux.hp.com/~enw/fstress-multi-iohang-010809/warn-and-sysrq-w-backtraces
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