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[libvirt] [PATCH 2/5] blockjob: add API for async virDomainBlockJobAbort



From: Adam Litke <agl us ibm com>

Block job cancellation can take a while.  Now that upstream qemu 1.1
has asynchronous block cancellation, we want to expose that to the user.
Therefore, the following updates are made to the virDomainBlockJob API:

A new block job event type VIR_DOMAIN_BLOCK_JOB_CANCELED is managed by
libvirt.  Regardless of the flags used with virDomainBlockJobAbort, this
event will be raised: 1. when using synchronous block_job_cancel (the
event will be synthesized by libvirt), and 2. whenever it is received
from qemu (via asynchronous block-job-cancel).  Note that the event
may be detected by libvirt even before the virDomainBlockJobAbort
completes (always true when it is synthesized, but also possible if
cancellation was fast).

A new extension flag VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC is added to the
virDomainBlockJobAbort API.  When enabled, this function will allow
(but not require) asynchronous operation (ie, it returns as soon as
possible, which might be before the job has actually been canceled).
When the API is used in this mode, it is the responsibility of the
caller to wait for a VIR_DOMAIN_BLOCK_JOB_CANCELED event or poll via
the virDomainGetBlockJobInfo API to check the cancellation status.

This patch also exposes the new flag through virsh, and makes virsh
slightly easier to use (--async implies --abort, and lack of any options
implies --info), although it leaves the qemu implementation for later
patches.

Signed-off-by: Adam Litke <agl us ibm com>
Cc: Stefan Hajnoczi <stefanha gmail com>
Signed-off-by: Eric Blake <eblake redhat com>
---
 include/libvirt/libvirt.h.in |   10 ++++++++
 src/libvirt.c                |   13 ++++++++++-
 tools/virsh.c                |   51 ++++++++++++++++++++++++++---------------
 tools/virsh.pod              |   35 ++++++++++++++++++++--------
 4 files changed, 79 insertions(+), 30 deletions(-)

diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
index 499dcd4..97ad99d 100644
--- a/include/libvirt/libvirt.h.in
+++ b/include/libvirt/libvirt.h.in
@@ -1946,6 +1946,15 @@ typedef enum {
 #endif
 } virDomainBlockJobType;

+/**
+ * virDomainBlockJobAbortFlags:
+ *
+ * VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC: Request only, do not wait for completion
+ */
+typedef enum {
+    VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC = 1 << 0,
+} virDomainBlockJobAbortFlags;
+
 /* An iterator for monitoring block job operations */
 typedef unsigned long long virDomainBlockJobCursor;

@@ -3617,6 +3626,7 @@ typedef void (*virConnectDomainEventGraphicsCallback)(virConnectPtr conn,
 typedef enum {
     VIR_DOMAIN_BLOCK_JOB_COMPLETED = 0,
     VIR_DOMAIN_BLOCK_JOB_FAILED = 1,
+    VIR_DOMAIN_BLOCK_JOB_CANCELED = 2,

 #ifdef VIR_ENUM_SENTINELS
     VIR_DOMAIN_BLOCK_JOB_LAST
diff --git a/src/libvirt.c b/src/libvirt.c
index 16d1fd5..93ec817 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -17902,7 +17902,7 @@ error:
  * virDomainBlockJobAbort:
  * @dom: pointer to domain object
  * @disk: path to the block device, or device shorthand
- * @flags: extra flags; not used yet, so callers should always pass 0
+ * @flags: bitwise-OR of virDomainBlockJobAbortFlags
  *
  * Cancel the active block job on the given disk.
  *
@@ -17913,6 +17913,17 @@ error:
  * can be found by calling virDomainGetXMLDesc() and inspecting
  * elements within //domain/devices/disk.
  *
+ * By default, this function performs a synchronous operation and the caller
+ * may assume that the operation has completed when 0 is returned.  However,
+ * BlockJob operations may take a long time to cancel, and during this time
+ * further domain interactions may be unresponsive.  To avoid this problem,
+ * pass VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC in the @flags argument to enable
+ * asynchronous behavior, returning as soon as possible.  When the job has
+ * been canceled, a BlockJob event will be emitted, with status
+ * VIR_DOMAIN_BLOCK_JOB_CANCELED (even if the ABORT_ASYNC flag was not
+ * used); it is also possible to poll virDomainBlockJobInfo() to see if
+ * the job cancellation is still pending.
+ *
  * Returns -1 in case of failure, 0 when successful.
  */
 int virDomainBlockJobAbort(virDomainPtr dom, const char *disk,
diff --git a/tools/virsh.c b/tools/virsh.c
index 44514c4..8ef57e0 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -7525,6 +7525,7 @@ blockJobImpl(vshControl *ctl, const vshCmd *cmd,
     const char *name, *path;
     unsigned long bandwidth = 0;
     int ret = -1;
+    unsigned int flags = 0;

     if (!vshConnectionUsability(ctl, ctl->conn))
         goto cleanup;
@@ -7541,7 +7542,9 @@ blockJobImpl(vshControl *ctl, const vshCmd *cmd,
     }

     if (mode == VSH_CMD_BLOCK_JOB_ABORT) {
-        ret = virDomainBlockJobAbort(dom, path, 0);
+        if (vshCommandOptBool(cmd, "async"))
+            flags |= VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC;
+        ret = virDomainBlockJobAbort(dom, path, flags);
     } else if (mode == VSH_CMD_BLOCK_JOB_INFO) {
         ret = virDomainGetBlockJobInfo(dom, path, info, 0);
     } else if (mode == VSH_CMD_BLOCK_JOB_SPEED) {
@@ -7589,20 +7592,25 @@ cmdBlockPull(vshControl *ctl, const vshCmd *cmd)
 }

 /*
- * "blockjobinfo" command
+ * "blockjob" command
  */
 static const vshCmdInfo info_block_job[] = {
-    {"help", N_("Manage active block operations.")},
-    {"desc", N_("Manage active block operations.")},
+    {"help", N_("Manage active block operations")},
+    {"desc", N_("Query, adjust speed, or cancel active block operations.")},
     {NULL, NULL}
 };

 static const vshCmdOptDef opts_block_job[] = {
     {"domain", VSH_OT_DATA, VSH_OFLAG_REQ, N_("domain name, id or uuid")},
     {"path", VSH_OT_DATA, VSH_OFLAG_REQ, N_("Fully-qualified path of disk")},
-    {"abort", VSH_OT_BOOL, VSH_OFLAG_NONE, N_("Abort the active job on the specified disk")},
-    {"info", VSH_OT_BOOL, VSH_OFLAG_NONE, N_("Get active job information for the specified disk")},
-    {"bandwidth", VSH_OT_DATA, VSH_OFLAG_NONE, N_("Set the Bandwidth limit in MB/s")},
+    {"abort", VSH_OT_BOOL, VSH_OFLAG_NONE,
+     N_("Abort the active job on the specified disk")},
+    {"async", VSH_OT_BOOL, VSH_OFLAG_NONE,
+     N_("don't wait for --abort to complete")},
+    {"info", VSH_OT_BOOL, VSH_OFLAG_NONE,
+     N_("Get active job information for the specified disk")},
+    {"bandwidth", VSH_OT_DATA, VSH_OFLAG_NONE,
+     N_("Set the Bandwidth limit in MB/s")},
     {NULL, 0, 0, NULL}
 };

@@ -7613,19 +7621,24 @@ cmdBlockJob(vshControl *ctl, const vshCmd *cmd)
     virDomainBlockJobInfo info;
     const char *type;
     int ret;
+    bool abortMode = (vshCommandOptBool(cmd, "abort") ||
+                      vshCommandOptBool(cmd, "async"));
+    bool infoMode = vshCommandOptBool(cmd, "info");
+    bool bandwidth = vshCommandOptBool(cmd, "bandwidth");

-    if (vshCommandOptBool (cmd, "abort")) {
-        mode = VSH_CMD_BLOCK_JOB_ABORT;
-    } else if (vshCommandOptBool (cmd, "info")) {
-        mode = VSH_CMD_BLOCK_JOB_INFO;
-    } else if (vshCommandOptBool (cmd, "bandwidth")) {
-        mode = VSH_CMD_BLOCK_JOB_SPEED;
-    } else {
+    if (abortMode + infoMode + bandwidth > 1) {
         vshError(ctl, "%s",
-                 _("One of --abort, --info, or --bandwidth is required"));
+                 _("conflict between --abort, --info, and --bandwidth modes"));
         return false;
     }

+    if (abortMode)
+        mode = VSH_CMD_BLOCK_JOB_ABORT;
+    else if (bandwidth)
+        mode = VSH_CMD_BLOCK_JOB_SPEED;
+    else
+        mode = VSH_CMD_BLOCK_JOB_INFO;
+
     ret = blockJobImpl(ctl, cmd, &info, mode);
     if (ret < 0)
         return false;
@@ -7634,13 +7647,13 @@ cmdBlockJob(vshControl *ctl, const vshCmd *cmd)
         return true;

     if (info.type == VIR_DOMAIN_BLOCK_JOB_TYPE_PULL)
-        type = "Block Pull";
+        type = _("Block Pull");
     else
-        type = "Unknown job";
+        type = _("Unknown job");

     print_job_progress(type, info.end - info.cur, info.end);
     if (info.bandwidth != 0)
-        vshPrint(ctl, "    Bandwidth limit: %lu MB/s\n", info.bandwidth);
+        vshPrint(ctl, _("    Bandwidth limit: %lu MB/s\n"), info.bandwidth);
     return true;
 }

@@ -17115,8 +17128,8 @@ static const vshCmdDef domManagementCmds[] = {
     {"autostart", cmdAutostart, opts_autostart, info_autostart, 0},
     {"blkdeviotune", cmdBlkdeviotune, opts_blkdeviotune, info_blkdeviotune, 0},
     {"blkiotune", cmdBlkiotune, opts_blkiotune, info_blkiotune, 0},
-    {"blockpull", cmdBlockPull, opts_block_pull, info_block_pull, 0},
     {"blockjob", cmdBlockJob, opts_block_job, info_block_job, 0},
+    {"blockpull", cmdBlockPull, opts_block_pull, info_block_pull, 0},
     {"blockresize", cmdBlockResize, opts_block_resize, info_block_resize, 0},
     {"change-media", cmdChangeMedia, opts_change_media, info_change_media, 0},
 #ifndef WIN32
diff --git a/tools/virsh.pod b/tools/virsh.pod
index c6e0ff3..5f3d9b1 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -650,7 +650,10 @@ pulled, the disk no longer depends on that portion of the backing chain.
 It pulls data for the entire disk in the background, the process of the
 operation can be checked with B<blockjob>.

-I<path> specifies fully-qualified path of the disk.
+I<path> specifies fully-qualified path of the disk; it corresponds
+to a unique target name (<target dev='name'/>) or source file (<source
+file='name'/>) for one of the disk devices attached to I<domain> (see
+also B<domblklist> for listing these names).
 I<bandwidth> specifies copying bandwidth limit in Mbps.

 =item B<blkdeviotune> I<domain> I<device>
@@ -687,13 +690,21 @@ Both I<--live> and I<--current> flags may be given, but I<--current> is
 exclusive. If no flag is specified, behavior is different depending
 on hypervisor.

-=item B<blockjob> I<domain> I<path> [I<--abort>] [I<--info>] [I<bandwidth>]
+=item B<blockjob> I<domain> I<path> { [I<--abort>] [I<--async>] |
+[I<--info>] | [I<bandwidth>] }

-Manage active block operations.
+Manage active block operations.  There are three modes: I<--info>,
+I<bandwidth>, and I<--abort>; I<--info> is default except that I<--async>
+implies I<--abort>.
+
+I<path> specifies fully-qualified path of the disk; it corresponds
+to a unique target name (<target dev='name'/>) or source file (<source
+file='name'/>) for one of the disk devices attached to I<domain> (see
+also B<domblklist> for listing these names).

-I<path> specifies fully-qualified path of the disk.
 If I<--abort> is specified, the active job on the specified disk will
-be aborted.
+be aborted.  If I<--async> is also specified, this command will return
+immediately, rather than waiting for the cancelation to complete.
 If I<--info> is specified, the active job information on the specified
 disk will be printed.
 I<bandwidth> can be used to set bandwidth limit for the active job.
@@ -701,11 +712,15 @@ I<bandwidth> can be used to set bandwidth limit for the active job.
 =item B<blockresize> I<domain> I<path> I<size>

 Resize a block device of domain while the domain is running, I<path>
-specifies the absolute path of the block device, I<size> is a scaled
-integer (see B<NOTES> above) which defaults to KiB (blocks of 1024 bytes)
-if there is no suffix.  You must use a suffix of "B" to get bytes (note
-that for historical reasons, this differs from B<vol-resize> which
-defaults to bytes without a suffix).
+specifies the absolute path of the block device; it corresponds
+to a unique target name (<target dev='name'/>) or source file (<source
+file='name'/>) for one of the disk devices attached to I<domain> (see
+also B<domblklist> for listing these names).
+
+I<size> is a scaled integer (see B<NOTES> above) which defaults to KiB
+(blocks of 1024 bytes) if there is no suffix.  You must use a suffix of
+"B" to get bytes (note that for historical reasons, this differs from
+B<vol-resize> which defaults to bytes without a suffix).

 =item B<dominfo> I<domain-id>

-- 
1.7.7.6


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