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-rw-r--r--libxl.add-option-to-disable-disk-cache-flushes-in-qdisk.patch215
1 files changed, 215 insertions, 0 deletions
diff --git a/libxl.add-option-to-disable-disk-cache-flushes-in-qdisk.patch b/libxl.add-option-to-disable-disk-cache-flushes-in-qdisk.patch
new file mode 100644
index 0000000..bdd553d
--- /dev/null
+++ b/libxl.add-option-to-disable-disk-cache-flushes-in-qdisk.patch
@@ -0,0 +1,215 @@
+https://bugzilla.novell.com/show_bug.cgi?id=879425
+---
+ tools/libxl/libxl.c | 2 ++
+ tools/libxl/libxl.h | 12 ++++++++++++
+ tools/libxl/libxlu_disk.c | 2 ++
+ tools/libxl/libxlu_disk_i.h | 2 +-
+ tools/libxl/libxlu_disk_l.l | 1 +
+ 5 files changed, 18 insertions(+), 1 deletion(-)
+
+Index: xen-4.13.0-testing/docs/man/xl-disk-configuration.5.pod
+===================================================================
+--- xen-4.13.0-testing.orig/docs/man/xl-disk-configuration.5.pod
++++ xen-4.13.0-testing/docs/man/xl-disk-configuration.5.pod
+@@ -344,6 +344,32 @@ can be used to disable "hole punching" f
+ were intentionally created non-sparse to avoid fragmentation of the
+ file.
+
++=item B<suse-diskcache-disable-flush>
++
++=over 4
++
++=item Description
++
++Request that the qemu block driver does not automatically flush written data to the backend storage.
++
++=item Supported values
++
++absent, present
++
++=item Mandatory
++
++No
++
++=item Default value
++
++absent
++
++=back
++
++This enables the '-disk cache=unsafe' mode inside qemu.
++In this mode writes to the underlying blockdevice are delayed.
++While using this option in production is dangerous, it improves performance during installation of a domU.
++
+ =back
+
+
+Index: xen-4.13.0-testing/tools/libxl/libxl.h
+===================================================================
+--- xen-4.13.0-testing.orig/tools/libxl/libxl.h
++++ xen-4.13.0-testing/tools/libxl/libxl.h
+@@ -439,6 +439,21 @@
+ #define LIBXL_HAVE_CREATEINFO_PASSTHROUGH 1
+
+ /*
++ * The libxl_device_disk has no way to indicate that cache=unsafe is
++ * supposed to be used. Provide this knob without breaking the ABI.
++ * This is done by overloading struct libxl_device_disk->readwrite:
++ * readwrite == 0: disk is readonly, cache= does not matter
++ * readwrite == 1: disk is readwrite, backend driver may tweak cache=
++ * readwrite == MAGIC: disk is readwrite, backend driver should ignore
++ * flush requests from the frontend driver.
++ * Note: the macro with MAGIC is used by libvirt to decide if this patch is applied
++ */
++#define LIBXL_HAVE_LIBXL_DEVICE_DISK_DISABLE_FLUSH_MAGIC 0x00006000U
++#define LIBXL_HAVE_LIBXL_DEVICE_DISK_DISABLE_FLUSH_MASK 0xffff0fffU
++#define LIBXL_SUSE_IS_CACHE_UNSAFE(rw) (((rw) & ~LIBXL_HAVE_LIBXL_DEVICE_DISK_DISABLE_FLUSH_MASK) == LIBXL_HAVE_LIBXL_DEVICE_DISK_DISABLE_FLUSH_MAGIC)
++#define LIBXL_SUSE_SET_CACHE_UNSAFE(rw) (((rw) & LIBXL_HAVE_LIBXL_DEVICE_DISK_DISABLE_FLUSH_MASK) | LIBXL_HAVE_LIBXL_DEVICE_DISK_DISABLE_FLUSH_MAGIC)
++
++/*
+ * libxl ABI compatibility
+ *
+ * The only guarantee which libxl makes regarding ABI compatibility
+Index: xen-4.13.0-testing/tools/libxl/libxl_disk.c
+===================================================================
+--- xen-4.13.0-testing.orig/tools/libxl/libxl_disk.c
++++ xen-4.13.0-testing/tools/libxl/libxl_disk.c
+@@ -386,6 +386,8 @@ static void device_disk_add(libxl__egc *
+ flexarray_append_pair(back, "discard-enable",
+ libxl_defbool_val(disk->discard_enable) ?
+ "1" : "0");
++ if (LIBXL_SUSE_IS_CACHE_UNSAFE(disk->readwrite))
++ flexarray_append_pair(back, "suse-diskcache-disable-flush", "1");
+
+ flexarray_append(front, "backend-id");
+ flexarray_append(front, GCSPRINTF("%d", disk->backend_domid));
+Index: xen-4.13.0-testing/tools/libxl/libxl_dm.c
+===================================================================
+--- xen-4.13.0-testing.orig/tools/libxl/libxl_dm.c
++++ xen-4.13.0-testing/tools/libxl/libxl_dm.c
+@@ -984,14 +984,27 @@ enum {
+ LIBXL__COLO_SECONDARY,
+ };
+
++static const char *qemu_cache_mode(const libxl_device_disk *disk)
++{
++ static const char cache_directsync[] = "directsync";
++ static const char cache_writeback[] = "writeback";
++ static const char cache_unsafe[] = "unsafe";
++
++ if (LIBXL_SUSE_IS_CACHE_UNSAFE(disk->readwrite))
++ return cache_unsafe;
++ if (disk->direct_io_safe)
++ return cache_directsync;
++ return cache_writeback;
++}
++
+ static char *qemu_disk_scsi_drive_string(libxl__gc *gc, const char *target_path,
+ int unit, const char *format,
+ const libxl_device_disk *disk,
+ int colo_mode, const char **id_ptr)
+ {
+ char *drive = NULL;
+- char *common = GCSPRINTF("if=none,readonly=%s,cache=writeback",
+- disk->readwrite ? "off" : "on");
++ char *common = GCSPRINTF("if=none,readonly=%s,cache=%s",
++ disk->readwrite ? "off" : "on", qemu_cache_mode(disk));
+ const char *exportname = disk->colo_export;
+ const char *active_disk = disk->active_disk;
+ const char *hidden_disk = disk->hidden_disk;
+@@ -1050,8 +1063,8 @@ static char *qemu_disk_ide_drive_string(
+ switch (colo_mode) {
+ case LIBXL__COLO_NONE:
+ drive = GCSPRINTF
+- ("file=%s,if=ide,index=%d,media=disk,format=%s,cache=writeback",
+- target_path, unit, format);
++ ("file=%s,if=ide,index=%d,media=disk,format=%s,cache=%s",
++ target_path, unit, format, qemu_cache_mode(disk));
+ break;
+ case LIBXL__COLO_PRIMARY:
+ /*
+@@ -1064,13 +1077,14 @@ static char *qemu_disk_ide_drive_string(
+ * vote-threshold=1
+ */
+ drive = GCSPRINTF(
+- "if=ide,index=%d,media=disk,cache=writeback,driver=quorum,"
++ "if=ide,index=%d,media=disk,cache=%s,driver=quorum,"
+ "id=%s,"
+ "children.0.file.filename=%s,"
+ "children.0.driver=%s,"
+ "read-pattern=fifo,"
+ "vote-threshold=1",
+- unit, exportname, target_path, format);
++ unit, qemu_cache_mode(disk),
++ exportname, target_path, format);
+ break;
+ case LIBXL__COLO_SECONDARY:
+ /*
+@@ -1084,7 +1098,7 @@ static char *qemu_disk_ide_drive_string(
+ * file.backing.backing=exportname,
+ */
+ drive = GCSPRINTF(
+- "if=ide,index=%d,id=top-colo,media=disk,cache=writeback,"
++ "if=ide,index=%d,id=top-colo,media=disk,cache=%s,"
+ "driver=replication,"
+ "mode=secondary,"
+ "top-id=top-colo,"
+@@ -1093,7 +1107,8 @@ static char *qemu_disk_ide_drive_string(
+ "file.backing.driver=qcow2,"
+ "file.backing.file.filename=%s,"
+ "file.backing.backing=%s",
+- unit, active_disk, hidden_disk, exportname);
++ unit, qemu_cache_mode(disk),
++ active_disk, hidden_disk, exportname);
+ break;
+ default:
+ abort();
+@@ -1881,8 +1896,8 @@ static int libxl__build_device_model_arg
+ return ERROR_INVAL;
+ }
+ flexarray_vappend(dm_args, "-drive",
+- GCSPRINTF("file=%s,if=none,id=ahcidisk-%d,format=%s,cache=writeback",
+- target_path, disk, format),
++ GCSPRINTF("file=%s,if=none,id=ahcidisk-%d,format=%s,cache=%s",
++ target_path, disk, format, qemu_cache_mode(&disks[i])),
+ "-device", GCSPRINTF("ide-hd,bus=ahci0.%d,unit=0,drive=ahcidisk-%d",
+ disk, disk), NULL);
+ continue;
+Index: xen-4.13.0-testing/tools/libxl/libxlu_disk.c
+===================================================================
+--- xen-4.13.0-testing.orig/tools/libxl/libxlu_disk.c
++++ xen-4.13.0-testing/tools/libxl/libxlu_disk.c
+@@ -79,6 +79,8 @@ int xlu_disk_parse(XLU_Config *cfg,
+ if (!disk->pdev_path || !strcmp(disk->pdev_path, ""))
+ disk->format = LIBXL_DISK_FORMAT_EMPTY;
+ }
++ if (disk->readwrite && dpc.suse_diskcache_disable_flush)
++ disk->readwrite = LIBXL_SUSE_SET_CACHE_UNSAFE(disk->readwrite);
+
+ if (!disk->vdev) {
+ xlu__disk_err(&dpc,0, "no vdev specified");
+Index: xen-4.13.0-testing/tools/libxl/libxlu_disk_i.h
+===================================================================
+--- xen-4.13.0-testing.orig/tools/libxl/libxlu_disk_i.h
++++ xen-4.13.0-testing/tools/libxl/libxlu_disk_i.h
+@@ -10,7 +10,7 @@ typedef struct {
+ void *scanner;
+ YY_BUFFER_STATE buf;
+ libxl_device_disk *disk;
+- int access_set, had_depr_prefix;
++ int access_set, suse_diskcache_disable_flush, had_depr_prefix;
+ const char *spec;
+ } DiskParseContext;
+
+Index: xen-4.13.0-testing/tools/libxl/libxlu_disk_l.l
+===================================================================
+--- xen-4.13.0-testing.orig/tools/libxl/libxlu_disk_l.l
++++ xen-4.13.0-testing/tools/libxl/libxlu_disk_l.l
+@@ -196,6 +196,7 @@ colo-port=[^,]*,? { STRIP(','); setcolop
+ colo-export=[^,]*,? { STRIP(','); SAVESTRING("colo-export", colo_export, FROMEQUALS); }
+ active-disk=[^,]*,? { STRIP(','); SAVESTRING("active-disk", active_disk, FROMEQUALS); }
+ hidden-disk=[^,]*,? { STRIP(','); SAVESTRING("hidden-disk", hidden_disk, FROMEQUALS); }
++suse-diskcache-disable-flush,? { DPC->suse_diskcache_disable_flush = 1; }
+
+ /* the target magic parameter, eats the rest of the string */
+
generated by cgit v1.2.3 (git 2.25.1) at 2025-12-20 01:04:14 +0000