between write i/os in a disk-based filesystem vs. the disk block being
freed by a truncation, allocated to a new file, and written again with
different data. if the disk driver reorders the requests and does
the second i/o first, the old data will clobber the new, corrupting
the new file.
pending i/os to complete before returning even if PGO_CLEANIT is not
specified. this fixes two races:
(1) NFS write rpcs vs. setattr operations which truncate the file.
if the truncate doesn't wait for pending writes to complete then
a later write rpc completion can undo the effect of the truncate.
this problem has been reported by several people.
(2) write i/os in disk-based filesystem vs. the disk block being
freed by a truncation, allocated to a new file, and written
again with different data. if the disk driver reorders the requests
and does the second i/o first, the old data will clobber the new,
corrupting the new file. I haven't heard of anyone experiencing
this problem yet, but it's fixed now anyway.
already. So, don't fail if there appears to be a corrupt label or
no 'fake' label; get the 'default' label (which is generated
from DIOCGDEFLABEL) instead.
the number of partitions is > OLDMAXPARTITIONS. This is better
than silently truncating the label (don't want to silently throw
away partitions when using an old disklabel binary on a label with
> 8 partitions). From Enami Tsugutomo.
doesn't have the exec bit set, we need to have PROT_EXEC set
in order for some expected mmap/mprotect behavior to work, so
do the last bit slightly differently: if udv_attach() fails, and
the protection (NOT maxprot) doens't include PROT_EXEC, then clear
PROT_EXEC from maxprot and try udv_attach() again.
Sigh, mmap really needs to be rototilled.
Rumors say there are archs without ISA busses, so avoid including
(uneccesarily) isa bus headers in MI files.
XXX this is the minimal solution, layer interface calls will have
XXX to be revisited later
other __HAVE_* defines are). Conditionalize definition of old
disklabel struct and ODIOC* definitions on it, allowing other ports
to bump the number of partitions in the label if they want to
(see comment in sys/disklabel.h).
chs