[libvirt] [PATCH] qemu: Fix reporting of physical capacity for block devices

[Peter Krempa]

Qemu reports physical size 0 for block devices. As 15fa84acbb55ebfee6a4
changed the behavior of qemuDomainGetBlockInfo to just query the monitor
this created a regression since we didn't report the size correctly any
more.

This patch adds code to refresh the physical size of a block device by
opening it and seeking to the end and uses it both in
qemuDomainGetBlockInfo and also in qemuDomainGetStatsOneBlock that was
broken since it was introduced in this respect.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1250982
---
 src/libvirt_private.syms  |  1 +
 src/qemu/qemu_driver.c    | 18 ++++++++++++++++--
 src/util/virstoragefile.c | 39 +++++++++++++++++++++++++++++++++++++++
 src/util/virstoragefile.h |  2 ++
 4 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 0517c24..5d320b7 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2156,6 +2156,7 @@ virStorageSourceParseRBDColonString;
 virStorageSourcePoolDefFree;
 virStorageSourcePoolModeTypeFromString;
 virStorageSourcePoolModeTypeToString;
+virStorageSourceUpdateBlockPhysicalSize;
 virStorageTypeFromString;
 virStorageTypeToString;

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 7a984a8..6998e12 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -11827,8 +11827,16 @@ qemuDomainGetBlockInfo(virDomainPtr dom,
         info->allocation = entry->wr_highest_offset;
     }

+    if (entry->physical) {
+        info->physical = entry->physical;
+    } else {
+        if (virStorageSourceUpdateBlockPhysicalSize(disk->src, true) < 0)
+            goto endjob;
+
+        info->physical = disk->src->physical;
+    }
+
     info->capacity = entry->capacity;
-    info->physical = entry->physical;

     ret = 0;

@@ -19274,9 +19282,15 @@ qemuDomainGetStatsOneBlock(virQEMUDriverPtr driver,
     if (entry->capacity)
         QEMU_ADD_BLOCK_PARAM_ULL(record, maxparams, block_idx,
                                  "capacity", entry->capacity);
-    if (entry->physical)
+    if (entry->physical) {
         QEMU_ADD_BLOCK_PARAM_ULL(record, maxparams, block_idx,
                                  "physical", entry->physical);
+    } else {
+        if (virStorageSourceUpdateBlockPhysicalSize(src, false) == 0) {
+            QEMU_ADD_BLOCK_PARAM_ULL(record, maxparams, block_idx,
+                                     "physical", src->physical);
+        }
+    }

     ret = 0;
  cleanup:
diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index 6c3017c..2aa1d90 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -2587,6 +2587,45 @@ virStorageSourceNewFromBacking(virStorageSourcePtr parent)
 }


+/**
+ * @src: disk source definiton structure
+ * @report: report libvirt errors if set to true
+ *
+ * Updates src->physical for block devices since qemu doesn't report the current
+ * size correctly for them. Returns 0 on success, -1 on error.
+ */
+int
+virStorageSourceUpdateBlockPhysicalSize(virStorageSourcePtr src,
+                                        bool report)
+{
+    int fd = -1;
+    off_t end;
+    int ret = -1;
+
+    if (virStorageSourceGetActualType(src) != VIR_STORAGE_TYPE_BLOCK)
+        return 0;
+
+    if ((fd = open(src->path, O_RDONLY)) < 0) {
+        if (report)
+            virReportSystemError(errno, _("failed to open block device '%s'"),
+                                 src->path);
+        return -1;
+    }
+
+    if ((end = lseek(fd, 0, SEEK_END)) == (off_t) -1) {
+        if (report)
+            virReportSystemError(errno,
+                                 _("failed to seek to end of '%s'"), src->path);
+    } else {
+        src->physical = end;
+        ret = 0;
+    }
+
+    VIR_FORCE_CLOSE(fd);
+    return ret;
+}
+
+
 static char *
 virStorageFileCanonicalizeFormatPath(char **components,
                                      size_t ncomponents,
diff --git a/src/util/virstoragefile.h b/src/util/virstoragefile.h
index aa17a00..b98fe25 100644
--- a/src/util/virstoragefile.h
+++ b/src/util/virstoragefile.h
@@ -362,6 +362,8 @@ bool virStorageSourceIsLocalStorage(virStorageSourcePtr src);
 bool virStorageSourceIsEmpty(virStorageSourcePtr src);
 void virStorageSourceFree(virStorageSourcePtr def);
 void virStorageSourceBackingStoreClear(virStorageSourcePtr def);
+int virStorageSourceUpdateBlockPhysicalSize(virStorageSourcePtr src,
+                                            bool report);
 virStorageSourcePtr virStorageSourceNewFromBacking(virStorageSourcePtr parent);
 virStorageSourcePtr virStorageSourceCopy(const virStorageSource *src,
                                          bool backingChain)
-- 
2.4.5