4:40 p.m.
On 12/14/18 4:16 PM, Richard W.M. Jones wrote:
This allows us to add the following callbacks:
- can_zero returns boolean
- can_fua should print "none", "emulate" or
"native"
Furthermore the following callbacks are modified in a backwards
compatible manner:
- pwrite adding flags parameter
- trim adding flags parameter
This change is not backwards compatible:
- zero may_trim parameter replaced by flags parameter
---
plugins/sh/nbdkit-sh-plugin.pod | 41 +++++++++++---
plugins/sh/sh.c | 99 +++++++++++++++++++++++++++------
2 files changed, 115 insertions(+), 25 deletions(-)
+=item C<can_fua>
+
+ /path/to/script can_fua <handle>
+
+This controls Forced Unit Access (FUA) behaviour of the core server.
+Unlike the other C<can_*> callbacks, this one is I<not> a boolean. It
+must print either "none", "emulate" or "native". The
meaning of these
Worth adding 'to stdout'?
+is described in L<nbdkit-plugin(3)>.
+
=item C<pread>
/path/to/script pread <handle> <count> <offset>
@@ -227,10 +240,13 @@ This method is required.
=item C<pwrite>
- /path/to/script pwrite <handle> <count> <offset>
+ /path/to/script pwrite <handle> <count> <offset> <flags>
The script should read the binary data to be written from stdin.
+The C<flags> parameter can be an empty string or C<"fua">. In
future
s/In future/In the future,/
+a comma-separated list of flags may be present.
Is the empty string "" always provided as an argument, or will the
argument be omitted in that case?
+
Unlike in other languages, if you provide a C<pwrite> method you
B<must> also provide a C<can_write> method which exits with code
C<0>
(true).
@@ -245,16 +261,23 @@ B<must> also provide a C<can_flush> method which exits
with code C<0>
=item C<trim>
- /path/to/script trim <handle> <count> <offset>
+ /path/to/script trim <handle> <count> <offset> <flags>
+
+The C<flags> parameter can be an empty string or C<"fua">. In
future
Copy-and-paste "In future"
+a comma-separated list of flags may be present.
>
> Unlike in other languages, if you provide a C<trim> method you B<must>
> also provide a C<can_trim> method which exits with code C<0> (true).
>
> =item C<zero>
>
> - /path/to/script zero <handle> <count> <offset> <may_trim>
> + /path/to/script zero <handle> <count> <offset> <flags>
>
> -C<may_trim> will be either C<true> or C<false>.
> +The C<flags> parameter can be an empty string or C<"fua">. In
future
+a comma-separated list of flags may be present.
This one is wrong, since you have both fua and may_trim now.
+
+ case RET_FALSE:
+ free (s);
+ nbdkit_error ("%s: %s method returned unexpected code (3/false)",
+ script, "can_fua");
Could we be nice and treat this as "none"?
@@ -538,12 +602,13 @@ sh_trim (void *handle, uint32_t count, uint64_t
offset)
}
static int
-sh_zero (void *handle, uint32_t count, uint64_t offset, int may_trim)
+sh_zero (void *handle, uint32_t count, uint64_t offset, uint32_t flags)
{
char *h = handle;
char cbuf[32], obuf[32];
- const char *args[] = { script, "zero", h, cbuf, obuf,
- may_trim ? "true" : "false", NULL };
+ /* In future, comma-separated list of flags. */
While I commented about 'in future' being too terse in the .pod, I don't
mind it being compressed in the .c file. On the other hand, the
comment here is wrong, as sh_zero needs to handle both fua and may_trim
flags.
+ const char *sflags = flags & NBDKIT_FLAG_FUA ? "fua"
: "";
and thus this computation for sflags is incomplete.
Otherwise, looking good.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org