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server: Add -D nbdkit.backend.controlpath and -D nbdkit.backend.datap… 
…ath.

These can be used to suppress verbose debugging messages from the
backend.

BugLink: https://bugzilla.redhat.com/1782868
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@rwmjones
rwmjones committed Dec 12, 2019
1 parent a895fa8 commit 231717e
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Showing 4 changed files with 167 additions and 34 deletions.
35 changes: 34 additions & 1 deletion docs/nbdkit.pod
View file
Expand Up @@ -182,7 +182,7 @@ value C<N>. See L<nbdkit-plugin(3)/Debug Flags>.
=item B<--debug> nbdkit.FLAG=N

Set the nbdkit server Debug Flag called C<FLAG> to the integer value
C<N>.
C<N>. See L</SERVER DEBUG FLAGS> below.

=item B<--dump-config>

Expand Down Expand Up @@ -536,6 +536,39 @@ languages. The file should be executable. For example:

(see L<nbdkit-perl-plugin(3)> for a full example).

=head1 SERVER DEBUG FLAGS

As well as enabling or disabling debugging in the server using
I<--verbose> you can control extra debugging in the server using the
C<-D nbdkit.*> flags listed in this section. Note these flags are an
internal implementation detail of the server and may be changed or
removed at any time in the future.

=over 4

=item B<-D nbdkit.backend.controlpath=0>

=item B<-D nbdkit.backend.controlpath=1>

=item B<-D nbdkit.backend.datapath=0>

=item B<-D nbdkit.backend.datapath=1>

These flags control the verbosity of nbdkit backend debugging messages
(the ones which show every request processed by the server). The
default for both settings is C<1> (normal debugging) but you can set
them to C<0> to suppress these messages.

C<-D nbdkit.backend.datapath=0> is the more useful setting which lets you
suppress messages about pread, pwrite, zero, trim, etc. commands.
When transferring large amounts of data these messages are numerous
and not usually very interesting.

C<-D nbdkit.backend.controlpath=0> suppresses the non-datapath
commands (config, open, close, can_write, etc.)

=back

=head1 SIGNALS

nbdkit responds to the following signals:
Expand Down
83 changes: 50 additions & 33 deletions server/backend.c
View file
Expand Up @@ -46,6 +46,22 @@

/* Helpers for registering a new backend. */

/* Use:
* -D nbdkit.backend.controlpath=0 to suppress control path debugging.
* -D nbdkit.backend.datapath=0 to suppress data path debugging.
*/
int nbdkit_debug_backend_controlpath = 1;
int nbdkit_debug_backend_datapath = 1;

#define controlpath_debug(fs, ...) \
do { \
if (nbdkit_debug_backend_controlpath) debug ((fs), ##__VA_ARGS__); \
} while (0)
#define datapath_debug(fs, ...) \
do { \
if (nbdkit_debug_backend_datapath) debug ((fs), ##__VA_ARGS__); \
} while (0)

void
backend_init (struct backend *b, struct backend *next, size_t index,
const char *filename, void *dl, const char *type)
Expand Down Expand Up @@ -108,7 +124,7 @@ backend_load (struct backend *b, const char *name, void (*load) (void))
apply_debug_flags (b->dl, name);

/* Call the on-load callback if it exists. */
debug ("%s: load", name);
controlpath_debug ("%s: load", name);
if (load)
load ();
}
Expand All @@ -121,7 +137,7 @@ backend_unload (struct backend *b, void (*unload) (void))
*/
lock_unload ();

debug ("%s: unload %s", b->name, b->type);
controlpath_debug ("%s: unload %s", b->name, b->type);
if (unload)
unload ();

Expand All @@ -139,7 +155,7 @@ backend_open (struct backend *b, struct connection *conn, int readonly)
{
struct b_conn_handle *h = &conn->handles[b->i];

debug ("%s: open readonly=%d", b->name, readonly);
controlpath_debug ("%s: open readonly=%d", b->name, readonly);

assert (h->handle == NULL);
assert ((h->state & HANDLE_OPEN) == 0);
Expand All @@ -151,7 +167,7 @@ backend_open (struct backend *b, struct connection *conn, int readonly)
* inner-to-outer ordering.
*/
h->handle = b->open (b, conn, readonly);
debug ("%s: open returned handle %p", b->name, h->handle);
controlpath_debug ("%s: open returned handle %p", b->name, h->handle);

if (h->handle == NULL) {
if (b->i) /* Do not strand backend if this layer failed */
Expand Down Expand Up @@ -179,7 +195,7 @@ backend_prepare (struct backend *b, struct connection *conn)
if (b->i && backend_prepare (b->next, conn) == -1)
return -1;

debug ("%s: prepare readonly=%d", b->name, h->can_write == 0);
controlpath_debug ("%s: prepare readonly=%d", b->name, h->can_write == 0);

if (b->prepare (b, conn, h->handle, h->can_write == 0) == -1)
return -1;
Expand All @@ -196,7 +212,7 @@ backend_finalize (struct backend *b, struct connection *conn)
* filter furthest away from the plugin, and matching .close order.
*/

debug ("%s: finalize", b->name);
controlpath_debug ("%s: finalize", b->name);

/* Once finalize fails, we can do nothing further on this connection */
if (h->state & HANDLE_FAILED)
Expand All @@ -223,7 +239,7 @@ backend_close (struct backend *b, struct connection *conn)
struct b_conn_handle *h = &conn->handles[b->i];

/* outer-to-inner order, opposite .open */
debug ("%s: close", b->name);
controlpath_debug ("%s: close", b->name);

if (h->handle) {
assert (h->state & HANDLE_OPEN);
Expand Down Expand Up @@ -252,7 +268,7 @@ backend_valid_range (struct backend *b, struct connection *conn,
int
backend_reopen (struct backend *b, struct connection *conn, int readonly)
{
debug ("%s: reopen readonly=%d", b->name, readonly);
controlpath_debug ("%s: reopen readonly=%d", b->name, readonly);

if (backend_finalize (b, conn) == -1)
return -1;
Expand All @@ -274,7 +290,7 @@ backend_get_size (struct backend *b, struct connection *conn)
{
struct b_conn_handle *h = &conn->handles[b->i];

debug ("%s: get_size", b->name);
controlpath_debug ("%s: get_size", b->name);

assert (h->handle && (h->state & HANDLE_CONNECTED));
if (h->exportsize == -1)
Expand All @@ -287,7 +303,7 @@ backend_can_write (struct backend *b, struct connection *conn)
{
struct b_conn_handle *h = &conn->handles[b->i];

debug ("%s: can_write", b->name);
controlpath_debug ("%s: can_write", b->name);

assert (h->handle && (h->state & HANDLE_CONNECTED));
if (h->can_write == -1)
Expand All @@ -300,7 +316,7 @@ backend_can_flush (struct backend *b, struct connection *conn)
{
struct b_conn_handle *h = &conn->handles[b->i];

debug ("%s: can_flush", b->name);
controlpath_debug ("%s: can_flush", b->name);

assert (h->handle && (h->state & HANDLE_CONNECTED));
if (h->can_flush == -1)
Expand All @@ -313,7 +329,7 @@ backend_is_rotational (struct backend *b, struct connection *conn)
{
struct b_conn_handle *h = &conn->handles[b->i];

debug ("%s: is_rotational", b->name);
controlpath_debug ("%s: is_rotational", b->name);

assert (h->handle && (h->state & HANDLE_CONNECTED));
if (h->is_rotational == -1)
Expand All @@ -327,7 +343,7 @@ backend_can_trim (struct backend *b, struct connection *conn)
struct b_conn_handle *h = &conn->handles[b->i];
int r;

debug ("%s: can_trim", b->name);
controlpath_debug ("%s: can_trim", b->name);

assert (h->handle && (h->state & HANDLE_CONNECTED));
if (h->can_trim == -1) {
Expand All @@ -347,7 +363,7 @@ backend_can_zero (struct backend *b, struct connection *conn)
struct b_conn_handle *h = &conn->handles[b->i];
int r;

debug ("%s: can_zero", b->name);
controlpath_debug ("%s: can_zero", b->name);

assert (h->handle && (h->state & HANDLE_CONNECTED));
if (h->can_zero == -1) {
Expand All @@ -367,7 +383,7 @@ backend_can_fast_zero (struct backend *b, struct connection *conn)
struct b_conn_handle *h = &conn->handles[b->i];
int r;

debug ("%s: can_fast_zero", b->name);
controlpath_debug ("%s: can_fast_zero", b->name);

assert (h->handle && (h->state & HANDLE_CONNECTED));
if (h->can_fast_zero == -1) {
Expand All @@ -386,7 +402,7 @@ backend_can_extents (struct backend *b, struct connection *conn)
{
struct b_conn_handle *h = &conn->handles[b->i];

debug ("%s: can_extents", b->name);
controlpath_debug ("%s: can_extents", b->name);

assert (h->handle && (h->state & HANDLE_CONNECTED));
if (h->can_extents == -1)
Expand All @@ -400,7 +416,7 @@ backend_can_fua (struct backend *b, struct connection *conn)
struct b_conn_handle *h = &conn->handles[b->i];
int r;

debug ("%s: can_fua", b->name);
controlpath_debug ("%s: can_fua", b->name);

assert (h->handle && (h->state & HANDLE_CONNECTED));
if (h->can_fua == -1) {
Expand All @@ -420,7 +436,7 @@ backend_can_multi_conn (struct backend *b, struct connection *conn)
struct b_conn_handle *h = &conn->handles[b->i];

assert (h->handle && (h->state & HANDLE_CONNECTED));
debug ("%s: can_multi_conn", b->name);
controlpath_debug ("%s: can_multi_conn", b->name);

if (h->can_multi_conn == -1)
h->can_multi_conn = b->can_multi_conn (b, conn, h->handle);
Expand All @@ -432,7 +448,7 @@ backend_can_cache (struct backend *b, struct connection *conn)
{
struct b_conn_handle *h = &conn->handles[b->i];

debug ("%s: can_cache", b->name);
controlpath_debug ("%s: can_cache", b->name);

assert (h->handle && (h->state & HANDLE_CONNECTED));
if (h->can_cache == -1)
Expand All @@ -451,8 +467,8 @@ backend_pread (struct backend *b, struct connection *conn,
assert (h->handle && (h->state & HANDLE_CONNECTED));
assert (backend_valid_range (b, conn, offset, count));
assert (flags == 0);
debug ("%s: pread count=%" PRIu32 " offset=%" PRIu64,
b->name, count, offset);
datapath_debug ("%s: pread count=%" PRIu32 " offset=%" PRIu64,
b->name, count, offset);

r = b->pread (b, conn, h->handle, buf, count, offset, flags, err);
if (r == -1)
Expand All @@ -475,8 +491,8 @@ backend_pwrite (struct backend *b, struct connection *conn,
assert (!(flags & ~NBDKIT_FLAG_FUA));
if (fua)
assert (h->can_fua > NBDKIT_FUA_NONE);
debug ("%s: pwrite count=%" PRIu32 " offset=%" PRIu64 " fua=%d",
b->name, count, offset, fua);
datapath_debug ("%s: pwrite count=%" PRIu32 " offset=%" PRIu64 " fua=%d",
b->name, count, offset, fua);

r = b->pwrite (b, conn, h->handle, buf, count, offset, flags, err);
if (r == -1)
Expand All @@ -494,7 +510,7 @@ backend_flush (struct backend *b, struct connection *conn,
assert (h->handle && (h->state & HANDLE_CONNECTED));
assert (h->can_flush == 1);
assert (flags == 0);
debug ("%s: flush", b->name);
datapath_debug ("%s: flush", b->name);

r = b->flush (b, conn, h->handle, flags, err);
if (r == -1)
Expand All @@ -518,8 +534,8 @@ backend_trim (struct backend *b, struct connection *conn,
assert (!(flags & ~NBDKIT_FLAG_FUA));
if (fua)
assert (h->can_fua > NBDKIT_FUA_NONE);
debug ("%s: trim count=%" PRIu32 " offset=%" PRIu64 " fua=%d",
b->name, count, offset, fua);
datapath_debug ("%s: trim count=%" PRIu32 " offset=%" PRIu64 " fua=%d",
b->name, count, offset, fua);

r = b->trim (b, conn, h->handle, count, offset, flags, err);
if (r == -1)
Expand Down Expand Up @@ -547,9 +563,10 @@ backend_zero (struct backend *b, struct connection *conn,
assert (h->can_fua > NBDKIT_FUA_NONE);
if (fast)
assert (h->can_fast_zero == 1);
debug ("%s: zero count=%" PRIu32 " offset=%" PRIu64
" may_trim=%d fua=%d fast=%d",
b->name, count, offset, !!(flags & NBDKIT_FLAG_MAY_TRIM), fua, fast);
datapath_debug ("%s: zero count=%" PRIu32 " offset=%" PRIu64
" may_trim=%d fua=%d fast=%d",
b->name, count, offset,
!!(flags & NBDKIT_FLAG_MAY_TRIM), fua, fast);

r = b->zero (b, conn, h->handle, count, offset, flags, err);
if (r == -1) {
Expand All @@ -572,8 +589,8 @@ backend_extents (struct backend *b, struct connection *conn,
assert (h->can_extents >= 0);
assert (backend_valid_range (b, conn, offset, count));
assert (!(flags & ~NBDKIT_FLAG_REQ_ONE));
debug ("%s: extents count=%" PRIu32 " offset=%" PRIu64 " req_one=%d",
b->name, count, offset, !!(flags & NBDKIT_FLAG_REQ_ONE));
datapath_debug ("%s: extents count=%" PRIu32 " offset=%" PRIu64 " req_one=%d",
b->name, count, offset, !!(flags & NBDKIT_FLAG_REQ_ONE));

if (h->can_extents == 0) {
/* By default it is safe assume that everything in the range is
Expand Down Expand Up @@ -602,8 +619,8 @@ backend_cache (struct backend *b, struct connection *conn,
assert (h->can_cache > NBDKIT_CACHE_NONE);
assert (backend_valid_range (b, conn, offset, count));
assert (flags == 0);
debug ("%s: cache count=%" PRIu32 " offset=%" PRIu64,
b->name, count, offset);
datapath_debug ("%s: cache count=%" PRIu32 " offset=%" PRIu64,
b->name, count, offset);

if (h->can_cache == NBDKIT_CACHE_EMULATE) {
static char buf[MAX_REQUEST_SIZE]; /* data sink, never read */
Expand Down
4 changes: 4 additions & 0 deletions tests/Makefile.am
View file
Expand Up @@ -138,6 +138,7 @@ EXTRA_DIST = \
test-nbd-extents.sh \
test-nbd-tls.sh \
test-nbd-tls-psk.sh \
test-nbdkit-backend-debug.sh \
test-nofilter.sh \
test-nozero.sh \
test-null-extents.sh \
Expand Down Expand Up @@ -750,6 +751,9 @@ endif HAVE_VDDK
# zero plugin test.
TESTS += test-zero.sh

# -D nbdkit.backend.* settings.
TESTS += test-nbdkit-backend-debug.sh

#----------------------------------------------------------------------
# Tests of language plugins.

Expand Down

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