On 08/01/2018 06:10 AM, Richard W.M. Jones wrote:
This can truncate, extend, or round up/down to a multiple. --- common-rules.mk | 3 +- configure.ac | 1 + filters/offset/nbdkit-offset-filter.pod | 7 +- filters/partition/nbdkit-partition-filter.pod | 1 + filters/truncate/Makefile.am | 61 ++++ filters/truncate/nbdkit-truncate-filter.pod | 88 +++++ filters/truncate/truncate.c | 301 ++++++++++++++++++ 7 files changed, 459 insertions(+), 3 deletions(-)
+ +=item * + +Round the size of the plugin up or down to the next multiple of C<N>. +Use either C<round-up=N> or C<round-down=N>.
Worth mentioning that N must be a power of 2.
+ +#define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL + +/* These are the parameters. */ +static int64_t truncate = -1; +static unsigned round_up = 0, round_down = 0; + +/* The real size of the underlying plugin. */ +static uint64_t real_size; + +/* The calculated size after applying the parameters. */ +static uint64_t size; + +/* This lock protects the real_size and size fields. */ +static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
Do we need the lock, or can we rely on the fact that .prepare will get called before anything else, and treat these as always initialized after that point?
+ /* The truncate, round-up and round-down parameters are treated as + * separate operations. It's possible to specify more than one, + * although perhaps not very useful. + */ + if (truncate >= 0) + size = truncate; + if (round_up > 0) + size = (size + round_up - 1) & ~(round_up-1);
Inconsistent spacing between the two instances of 'round_up - 1'; I think we favor the spaces everywhere...
+ if (round_down > 0) + size &= ~(round_down-1);
...in which case the spacing here is also suspect.
+ if (count > 0) { + /* The caller must be writing zeroes, else it's an error. */ + if (!is_zero (buf, count)) { + nbdkit_error ("truncate: write beyond end of underlying device"); + *err = EIO;
Would ENOSPC be better here? -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org