DragonFly bugs List (threaded) for 2010-11
Re: Constant crashes on x86_64 with UFS
:On the VM that I provide for Justin to make bulk builds I am getting
:constant panics after I enabled swapcache.
:#15 0xffffffff804fec9c in ffs_realloccg (ip=0xffffffe00096e698,
:lbprev=<value optimized out>, bpref=8, osize=4096, nsize=5120,
: cred=0xffffffe000886900, bpp=0xffffffe02e4157f0) at
:DragonFly df64pkgbuilder.lan.net 2.9-DEVELOPMENT DragonFly
:v126.96.36.199.ge61a8-DEVELOPMENT #0: Fri Nov 5 06:38:41 CET 2010
:Anyone seen this before?
Hmm. I haven't seen it before but I can see how it can happen.
b_bio2 is being used by the vn_cache_strategy code (swapcache).
UFS/FFS is assuming that *ALL* file bread()s ultimately dive into the
UFS/FFS stategy code and properly populate b_bio2 for the drill-down
to the disk device, but if it gets bypassed by the swapcache that will
not happen. Instead, b_bio2 is populated by the swapcache and the
value will have nothing to do with the underlying disk device.
The bug is actually in swapcache. The solution is for swapcache to
set bio_offset to NOOFFSET, but it is a bit of a hack to make it do
The reason this problem doesn't occur with HAMMER is due to a fluke.
HAMMER does a test for HAMMER_ZONE_LARGE_DATA before believing a
cached bio_offset and, of course, that is one huge 64-bit offset and
swapcache is never able to set an offset that large.
Please try this patch: