10:10 p.m.
POSIX allows but does not require ENOTSUP and EOPNOTSUPP to map to the
same errno value. This patch has no impact on Linux, but does affect
other systems: we want to be permissive in what we accept (either
spelling, since the two are commonly confused), while strict in what
we generate (we documented EOPNOTSUPP as the trigger to fall back to
.write, so stick to that internally where it makes sense). An
upcoming NBD protocol extension is proposing the exposure of an
NBD_ENOTSUP error, and so we'll need to make sure that both errno
values (when they are distinct) feed into that single wire value.
Signed-off-by: Eric Blake <eblake(a)redhat.com>
---
docs/nbdkit-filter.pod | 11 ++++++-----
docs/nbdkit-plugin.pod | 12 +++++++-----
plugins/file/file.c | 16 +++++++++++-----
plugins/perl/perl.c | 2 +-
plugins/python/python.c | 2 +-
plugins/ruby/ruby.c | 2 +-
server/plugins.c | 2 +-
7 files changed, 28 insertions(+), 19 deletions(-)
diff --git a/docs/nbdkit-filter.pod b/docs/nbdkit-filter.pod
index 02f15c13..6e2bea61 100644
--- a/docs/nbdkit-filter.pod
+++ b/docs/nbdkit-filter.pod
@@ -524,15 +524,16 @@ C<next_ops-E<gt>zero> if
C<next_ops-E<gt>can_fua> returned a positive
value.
Note that unlike the plugin C<.zero> which is permitted to fail with
-C<EOPNOTSUPP> to force a fallback to C<.pwrite>, the function
-C<next_ops-E<gt>zero> will never fail with C<err> set to
C<EOPNOTSUPP>
-because the fallback has already taken place.
+C<ENOTSUP> or C<EOPNOTSUPP> to force a fallback to C<.pwrite>, the
+function C<next_ops-E<gt>zero> will never fail with C<err> set to
+C<ENOTSUP> or C<EOPNOTSUPP> because the fallback has already taken
+place.
If there is an error, C<.zero> should call C<nbdkit_error> with an
error message B<and> return -1 with C<err> set to the positive errno
value to return to the client. The filter should never fail with
-C<EOPNOTSUPP> (while plugins have automatic fallback to C<.pwrite>,
-filters do not).
+C<ENOTSUP> or C<EOPNOTSUPP> (while plugins have automatic fallback to
+C<.pwrite>, filters do not).
=head2 C<.extents>
diff --git a/docs/nbdkit-plugin.pod b/docs/nbdkit-plugin.pod
index 03269e88..423cccdb 100644
--- a/docs/nbdkit-plugin.pod
+++ b/docs/nbdkit-plugin.pod
@@ -612,15 +612,16 @@ plugin wants the C<.zero> callback to be utilized. Support
for
writing zeroes is still advertised to the client (unless the nbdkit
filter nozero is also used), so returning false merely serves as a way
to avoid complicating the C<.zero> callback to have to fail with
-C<EOPNOTSUPP> on the connections where it will never be more efficient
-than using C<.pwrite> up front.
+C<ENOTSUP> or C<EOPNOTSUPP> on the connections where it will never be
+more efficient than using C<.pwrite> up front.
If there is an error, C<.can_zero> should call C<nbdkit_error> with an
error message and return C<-1>.
This callback is not required. If omitted, then nbdkit always tries
C<.zero> first if it is present, and gracefully falls back to
-C<.pwrite> if C<.zero> was absent or failed with C<EOPNOTSUPP>.
+C<.pwrite> if C<.zero> was absent or failed with C<ENOTSUP> or
+C<EOPNOTSUPP>.
=head2 C<.can_extents>
@@ -809,8 +810,9 @@ C<.can_fua>.
If C<NBDKIT_FLAG_MAY_TRIM> is requested, the operation can punch a
hole instead of writing actual zero bytes, but only if subsequent
reads from the hole read as zeroes. If this callback is omitted, or
-if it fails with C<EOPNOTSUPP> (whether by C<nbdkit_set_error> or
-C<errno>), then C<.pwrite> will be used instead.
+if it fails with C<ENOTSUP> or C<EOPNOTSUPP> (whether by
+C<nbdkit_set_error> or C<errno>), then C<.pwrite> will be used
+instead.
The callback must write the whole C<count> bytes if it can. The NBD
protocol doesn't allow partial writes (instead, these would be
diff --git a/plugins/file/file.c b/plugins/file/file.c
index 9df5001d..a9d6491a 100644
--- a/plugins/file/file.c
+++ b/plugins/file/file.c
@@ -73,6 +73,12 @@ static pthread_mutex_t lseek_lock = PTHREAD_MUTEX_INITIALIZER;
/* to enable: -D file.zero=1 */
int file_debug_zero;
+static bool
+file_is_enotsup (int err)
+{
+ return err == ENOTSUP || err == EOPNOTSUPP;
+}
+
static void
file_unload (void)
{
@@ -399,7 +405,7 @@ file_zero (void *handle, uint32_t count, uint64_t offset, uint32_t
flags)
goto out;
}
- if (errno != EOPNOTSUPP) {
+ if (!file_is_enotsup (errno)) {
nbdkit_error ("zero: %m");
return -1;
}
@@ -418,7 +424,7 @@ file_zero (void *handle, uint32_t count, uint64_t offset, uint32_t
flags)
goto out;
}
- if (errno != EOPNOTSUPP) {
+ if (!file_is_enotsup (errno)) {
nbdkit_error ("zero: %m");
return -1;
}
@@ -443,14 +449,14 @@ file_zero (void *handle, uint32_t count, uint64_t offset, uint32_t
flags)
goto out;
}
- if (errno != EOPNOTSUPP) {
+ if (!file_is_enotsup (errno)) {
nbdkit_error ("zero: %m");
return -1;
}
h->can_fallocate = false;
} else {
- if (errno != EOPNOTSUPP) {
+ if (!file_is_enotsup (errno)) {
nbdkit_error ("zero: %m");
return -1;
}
@@ -513,7 +519,7 @@ file_trim (void *handle, uint32_t count, uint64_t offset, uint32_t
flags)
return -1;
}
- if (errno == EOPNOTSUPP)
+ if (file_is_enotsup (EOPNOTSUPP))
h->can_punch_hole = false;
nbdkit_debug ("ignoring failed fallocate during trim: %m");
diff --git a/plugins/perl/perl.c b/plugins/perl/perl.c
index e8395dd2..59b26788 100644
--- a/plugins/perl/perl.c
+++ b/plugins/perl/perl.c
@@ -505,7 +505,7 @@ perl_zero (void *handle, uint32_t count, uint64_t offset, int
may_trim)
FREETMPS;
LEAVE;
- if (last_error == EOPNOTSUPP) {
+ if (last_error == EOPNOTSUPP || last_error == ENOTSUP) {
/* When user requests this particular error, we want to
gracefully fall back, and to accomodate both a normal return
and an exception. */
diff --git a/plugins/python/python.c b/plugins/python/python.c
index 71a982a3..20232f4f 100644
--- a/plugins/python/python.c
+++ b/plugins/python/python.c
@@ -603,7 +603,7 @@ py_zero (void *handle, uint32_t count, uint64_t offset, int may_trim)
r = PyObject_CallObject (fn, args);
Py_DECREF (fn);
Py_DECREF (args);
- if (last_error == EOPNOTSUPP) {
+ if (last_error == EOPNOTSUPP || last_error == ENOTSUP) {
/* When user requests this particular error, we want to
gracefully fall back, and to accomodate both a normal return
and an exception. */
diff --git a/plugins/ruby/ruby.c b/plugins/ruby/ruby.c
index b31f6a4e..ff7932c4 100644
--- a/plugins/ruby/ruby.c
+++ b/plugins/ruby/ruby.c
@@ -420,7 +420,7 @@ plugin_rb_zero (void *handle, uint32_t count, uint64_t offset, int
may_trim)
argv[3] = may_trim ? Qtrue : Qfalse;
last_error = 0;
(void) funcall2 (Qnil, rb_intern ("zero"), 4, argv,
&exception_happened);
- if (last_error == EOPNOTSUPP ||
+ if (last_error == EOPNOTSUPP || last_error == ENOTSUP ||
exception_happened == EXCEPTION_NO_METHOD_ERROR) {
nbdkit_debug ("zero falling back to pwrite");
nbdkit_set_error (EOPNOTSUPP);
diff --git a/server/plugins.c b/server/plugins.c
index 88a41044..1497c8b1 100644
--- a/server/plugins.c
+++ b/server/plugins.c
@@ -679,7 +679,7 @@ plugin_zero (struct backend *b, struct connection *conn,
emulate = true;
if (r == -1)
*err = emulate ? EOPNOTSUPP : get_error (p);
- if (r == 0 || *err != EOPNOTSUPP)
+ if (r == 0 || (*err != EOPNOTSUPP && *err != ENOTSUP))
goto done;
}
--
2.20.1