[Libguestfs] [nbdkit PATCH] nozero: Add notrim mode
Eric Blake
eblake at redhat.com
Fri May 10 00:14:52 UTC 2019
It may be useful to test whether the client's use of
NBD_CMD_FLAG_NO_HOLE makes a difference; do this by adding a mode to
--filter=nozero to force a non-trimming zero write.
Signed-off-by: Eric Blake <eblake at redhat.com>
---
filters/nozero/nbdkit-nozero-filter.pod | 19 +++++++----
filters/nozero/nozero.c | 45 ++++++++++++++++++++-----
tests/test-nozero.sh | 27 +++++++++++++--
3 files changed, 74 insertions(+), 17 deletions(-)
diff --git a/filters/nozero/nbdkit-nozero-filter.pod b/filters/nozero/nbdkit-nozero-filter.pod
index 7e06570..8e694bb 100644
--- a/filters/nozero/nbdkit-nozero-filter.pod
+++ b/filters/nozero/nbdkit-nozero-filter.pod
@@ -18,14 +18,19 @@ testing client or server fallbacks.
=over 4
-=item B<zeromode=none|emulate>
+=item B<zeromode=none|emulate|notrim>
Optional, controls which mode the filter will use. Mode B<none>
-(default) means that zero support is not advertised to the client;
-mode B<emulate> means that zero support is emulated by the filter
-using the plugin's C<pwrite> callback, regardless of whether the
-plugin itself implemented the C<zero> callback with a more efficient
-way to write zeroes.
+(default) means that zero support is not advertised to the
+client. Mode B<emulate> means that zero support is emulated by the
+filter using the plugin's C<pwrite> callback, regardless of whether
+the plugin itself implemented the C<zero> callback with a more
+efficient way to write zeros. Since nbdkit E<ge> 1.13.4, mode
+B<notrim> means that zero requests are forwarded on to the plugin,
+except that the plugin will never see the NBDKIT_MAY_TRIM flag, to
+determine if the client permitting trimming during zero operations
+makes a difference (it is an error to request this mode if the plugin
+does not support the C<zero> callback).
=back
@@ -55,4 +60,4 @@ Eric Blake
=head1 COPYRIGHT
-Copyright (C) 2018 Red Hat Inc.
+Copyright (C) 2018-2019 Red Hat Inc.
diff --git a/filters/nozero/nozero.c b/filters/nozero/nozero.c
index 3ec6346..6e0ffa9 100644
--- a/filters/nozero/nozero.c
+++ b/filters/nozero/nozero.c
@@ -47,8 +47,12 @@
#define MAX_WRITE (64 * 1024 * 1024)
-static char buffer[MAX_WRITE];
-static bool emulate;
+static const char buffer[MAX_WRITE];
+static enum ZeroMode {
+ NONE,
+ EMULATE,
+ NOTRIM,
+} zeromode;
static int
nozero_config (nbdkit_next_config *next, void *nxdata,
@@ -56,7 +60,9 @@ nozero_config (nbdkit_next_config *next, void *nxdata,
{
if (strcmp (key, "zeromode") == 0) {
if (strcmp (value, "emulate") == 0)
- emulate = true;
+ zeromode = EMULATE;
+ else if (strcmp (value, "notrim") == 0)
+ zeromode = NOTRIM;
else if (strcmp (value, "none") != 0) {
nbdkit_error ("unknown zeromode '%s'", value);
return -1;
@@ -67,13 +73,31 @@ nozero_config (nbdkit_next_config *next, void *nxdata,
}
#define nozero_config_help \
- "zeromode=<MODE> Either 'none' (default) or 'emulate'.\n" \
+ "zeromode=<MODE> Either 'none' (default), 'emulate', or 'notrim'.\n" \
+
+/* Check that desired mode is supported by plugin. */
+static int
+nozero_prepare (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle)
+{
+ int r;
+
+ if (zeromode == NOTRIM) {
+ r = next_ops->can_zero (nxdata);
+ if (r == -1)
+ return -1;
+ if (!r) {
+ nbdkit_error ("zeromode 'notrim' requires plugin zero support");
+ return -1;
+ }
+ }
+ return 0;
+}
/* Advertise desired WRITE_ZEROES mode. */
static int
nozero_can_zero (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle)
{
- return emulate;
+ return zeromode != NONE;
}
static int
@@ -81,11 +105,15 @@ nozero_zero (struct nbdkit_next_ops *next_ops, void *nxdata,
void *handle, uint32_t count, uint64_t offs, uint32_t flags,
int *err)
{
- assert (emulate);
+ assert (zeromode != NONE);
+ flags &= ~NBDKIT_FLAG_MAY_TRIM;
+
+ if (zeromode == NOTRIM)
+ return next_ops->zero (nxdata, count, offs, flags, err);
+
while (count) {
uint32_t size = MIN (count, MAX_WRITE);
- if (next_ops->pwrite (nxdata, buffer, size, offs,
- flags & ~NBDKIT_FLAG_MAY_TRIM, err) == -1)
+ if (next_ops->pwrite (nxdata, buffer, size, offs, flags, err) == -1)
return -1;
offs += size;
count -= size;
@@ -99,6 +127,7 @@ static struct nbdkit_filter filter = {
.version = PACKAGE_VERSION,
.config = nozero_config,
.config_help = nozero_config_help,
+ .prepare = nozero_prepare,
.can_zero = nozero_can_zero,
.zero = nozero_zero,
};
diff --git a/tests/test-nozero.sh b/tests/test-nozero.sh
index 1282586..fc22420 100755
--- a/tests/test-nozero.sh
+++ b/tests/test-nozero.sh
@@ -39,12 +39,14 @@ sock3=`mktemp -u`
sock4=`mktemp -u`
sock5a=`mktemp -u`
sock5b=`mktemp -u`
+sock6=`mktemp -u`
files="nozero1.img nozero1.log $sock1 nozero1.pid
nozero2.img nozero2.log $sock2 nozero2.pid
nozero3.img nozero3.log $sock3 nozero3.pid
nozero4.img nozero4.log $sock4 nozero4.pid
nozero5.img nozero5a.log nozero5b.log $sock5a $sock5b
- nozero5a.pid nozero5b.pid"
+ nozero5a.pid nozero5b.pid
+ nozero6.img nozero6.log $sock6 nozero6.pid"
rm -f $files
# Prep images, and check that qemu-io understands the actions we plan on
@@ -54,6 +56,7 @@ cp nozero1.img nozero2.img
cp nozero1.img nozero3.img
cp nozero1.img nozero4.img
cp nozero1.img nozero5.img
+cp nozero1.img nozero6.img
if ! qemu-io -f raw -d unmap -c 'w -z -u 0 1M' nozero1.img; then
echo "$0: missing or broken qemu-io"
rm nozero?.img
@@ -82,17 +85,20 @@ cleanup ()
cat nozero5a.log || :
echo "Log 5b file contents:"
cat nozero5b.log || :
+ echo "Log 6 file contents:"
+ cat nozero6.log || :
rm -f $files
}
cleanup_fn cleanup
-# Run four parallel nbdkit; to compare the logs and see what changes.
+# Run several parallel nbdkit; to compare the logs and see what changes.
# 1: unfiltered, to check that qemu-io sends ZERO request and plugin trims
# 2: log before filter with zeromode=none (default), to ensure no ZERO request
# 3: log before filter with zeromode=emulate, to ensure ZERO from client
# 4: log after filter with zeromode=emulate, to ensure no ZERO to plugin
# 5a/b: both sides of nbd plugin: even though server side does not advertise
# ZERO, the client side still exposes it, and just skips calling nbd's .zero
+# 6: log after filter with zeromode=notrim, to ensure plugin does not trim
start_nbdkit -P nozero1.pid -U $sock1 --filter=log \
file logfile=nozero1.log nozero1.img
start_nbdkit -P nozero2.pid -U $sock2 --filter=log --filter=nozero \
@@ -105,6 +111,8 @@ start_nbdkit -P nozero5a.pid -U $sock5a --filter=log --filter=nozero \
file logfile=nozero5a.log nozero5.img
start_nbdkit -P nozero5b.pid -U $sock5b --filter=log \
nbd logfile=nozero5b.log socket=$sock5a
+start_nbdkit -P nozero6.pid -U $sock6 --filter=nozero --filter=log \
+ file logfile=nozero6.log nozero6.img zeromode=notrim
# Perform the zero write.
qemu-io -f raw -c 'w -z -u 0 1M' "nbd+unix://?socket=$sock1"
@@ -112,6 +120,7 @@ qemu-io -f raw -c 'w -z -u 0 1M' "nbd+unix://?socket=$sock2"
qemu-io -f raw -c 'w -z -u 0 1M' "nbd+unix://?socket=$sock3"
qemu-io -f raw -c 'w -z -u 0 1M' "nbd+unix://?socket=$sock4"
qemu-io -f raw -c 'w -z -u 0 1M' "nbd+unix://?socket=$sock5b"
+qemu-io -f raw -c 'w -z -u 0 1M' "nbd+unix://?socket=$sock6"
# Check for expected ZERO vs. WRITE results
grep 'connection=1 Zero' nozero1.log
@@ -129,9 +138,23 @@ if grep 'connection=1 Zero' nozero5a.log; then
echo "nbdkit should have converted zero into write before nbd plugin"
exit 1
fi
+grep 'connection=1 Zero' nozero6.log
# Sanity check on contents - all 5 files should read identically
cmp nozero1.img nozero2.img
cmp nozero2.img nozero3.img
cmp nozero3.img nozero4.img
cmp nozero4.img nozero5.img
+cmp nozero5.img nozero6.img
+
+# Sanity check on sparseness; only image 1 should be sparse
+if test "$(stat -c %b nozero1.img)" = "$(stat -c %b nozero2.img)"; then
+ echo "nozero1.img was not trimmed"
+ exit 1
+fi
+for i in 3 4 5 6; do
+ if test "$(stat -c %b nozero2.img)" != "$(stat -c %b nozero$i.img)"; then
+ echo "nozero$i.img was trimmed by mistake"
+ exit 1
+ fi
+done
--
2.20.1
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