In the event of a fiemap ioctl failing (when the file is on a tmpfs,
for instance), we would free() serve->allocation_map, but it would
remain not NULL, leading to segfaults in client.c when responding to
write requests.
Keeping the free() behaviour is more hassle than it's worth, as there
are synchronization problems with setting serve->allocation_map to
NULL, so we just omit the free() instead to avoid the segfault. This
is safe because we never consult the map until allocation_map_built is
set to true, and we never do that when the builder thread fails.
server startup (sparse write avoidance doesn't happen until it is finished).
Added mutex to bitset functions, which were already being called from
multiple threads. Rewrote allocation map builder to request file
information in multiple chunks, to avoid uninterruptible wait and dynamic
memory allocation.
If the client cuts off part-way through the write, it should cause an
error, not a fatal. Previously this happened if the open file had a
fiemap, but not if there was no allocation map. This patch fixes that,
along with an associated valgrind error.
O_DIRECT causes problems on (at least) a wheezy VM, and there are mixed
reports about its performance impact. This patch makes it a
compile-time choice which should remain until it's been benchmarked.
