The 2.6.30 kernel build systems sets -Wframe-larger-than=2048 which causes
a warning to be generated when an individual stack frame exceeds 2048.
This caught the spa_history_log() and dmu_objset_snapshot() functions
which declared a data structure on the stack which contained a char
array of MAXPATHLEN. This in defined to be 4096 in the linux kernel
and I imagine it is quite large under Solaris as well. Regardless, the
offending data structures were moved to the heap to correctly keep the
stack depth to a minimum. We might consider setting this value even
lower to catch additional offenders because we are expecting deep stacks.
2.6.22 API change
Unused destroy_dirty_buffers arg removed from prototype.
2.6.24 API change
Empty write barriers are now supported and we should use them.
2.6.24 API change
Size argument dropped from bio_endio and bi_end_io, because the
bi_end_io is only called once now when the request is complete.
There is no longer any need for a size argument. This also means
that partial IO's are no longer possibe and the end_io callback
should not check bi->bi_size. Finally, the return type was updated
to void.
2.6.28 API change
open/close_bdev_excl() renamed to open/close_bdev_exclusive().
2.6.29 API change
BIO_RW_SYNC renamed to BIO_RW_SYNCIO.
Modern kernel build systems at least post 2.6.16 will set this properly
so we should not. In fact post 2.6.28 the include headers have moved
under arch so the guess we make here is completely wrong. Letting
the kernel build system set this ensure it will be correct. Also
drop the ulimit from the Makefile which, not surprisingly, turns out
to be very non-portable. If your expecting failures set the ulimit
in your shell before kicking off the test suite.
It's still not clear to me why the default value here is large
enough Solaris. I hit this limit again when setting up 120 SATA
drives configured as 15 raidz2 groups each containing 8 drives.
We expect to go bigger so we may just want to spend a little
time and figure out how to make this all dynamic.
SLES10 ships util-linux-2.12r-35.30 which does not support the -f option
to losetup. To avoid this problem the unused_loop_device() function was
added which attempts to find an unused loop device by checking each
/dev/loop* device with losetup to see if it is configured.
Brian Behlendorf
Ricardo M. Correia