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From 1ae3c3fa35e9801b69be59205fa1bf00913c391c Mon Sep 17 00:00:00 2001
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Message-Id: <1ae3c3fa35e9801b69be59205fa1bf00913c391c.1391001809.git.jdenemar@redhat.com>
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From: Osier Yang <jyang@redhat.com>
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Date: Mon, 27 Jan 2014 20:39:30 +0800
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Subject: [PATCH] storage: Add document for possible problem on volume
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 detection
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https://bugzilla.redhat.com/show_bug.cgi?id=726797
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For pool which relies on remote resources, such as a "iscsi" type
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pool, since how long it takes to export the corresponding devices
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to host's sysfs is really depended, it could depend on the network
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connection, it also could depend on the host's udev procedures. So
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it's likely that the volumes are not able to be detected during pool
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starting process, polling the sysfs doesn't work, since we don't
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know how much time is best for the polling, and even worse, the
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volumes could still be not detected or partly not detected even after
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the polling.  So we end up with a documentation to prompt the fact,
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in virsh manual.
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And as a small improvement, let's explicitly say no LUNs found in
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the debug log in that case.
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(cherry picked from commit 6b29eb848f741742a0f393df40bbcc176520bf27)
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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---
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 src/storage/storage_backend_scsi.c | 5 +++++
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 tools/virsh.pod                    | 9 +++++++++
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 2 files changed, 14 insertions(+)
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diff --git a/src/storage/storage_backend_scsi.c b/src/storage/storage_backend_scsi.c
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index 64b7843..7437488 100644
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--- a/src/storage/storage_backend_scsi.c
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+++ b/src/storage/storage_backend_scsi.c
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@@ -492,6 +492,7 @@ virStorageBackendSCSIFindLUs(virStoragePoolObjPtr pool,
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     DIR *devicedir = NULL;
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     struct dirent *lun_dirent = NULL;
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     char devicepattern[64];
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+    bool found = false;
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     VIR_DEBUG("Discovering LUs on host %u", scanhost);
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@@ -513,11 +514,15 @@ virStorageBackendSCSIFindLUs(virStoragePoolObjPtr pool,
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             continue;
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         }
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+        found = true;
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         VIR_DEBUG("Found LU '%s'", lun_dirent->d_name);
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         processLU(pool, scanhost, bus, target, lun);
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     }
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+    if (!found)
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+        VIR_DEBUG("No LU found for pool %s", pool->def->name);
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+
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     closedir(devicedir);
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     return retval;
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diff --git a/tools/virsh.pod b/tools/virsh.pod
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index 6b25e99..e866217 100644
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--- a/tools/virsh.pod
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+++ b/tools/virsh.pod
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@@ -2606,6 +2606,15 @@ Refresh the list of volumes contained in I<pool>.
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 Start the storage I<pool>, which is previously defined but inactive.
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+B<Note>: A storage pool that relies on remote resources such as an
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+"iscsi" or a (v)HBA backed "scsi" pool may need to be refreshed multiple
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+times in order to have all the volumes detected (see B<pool-refresh>).
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+This is because the corresponding volume devices may not be present in
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+the host's filesystem during the initial pool startup or the current
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+refresh attempt. The number of refresh retries is dependant upon the
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+network connection and the time the host takes to export the
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+corresponding devices.
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+
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 =item B<pool-undefine> I<pool-or-uuid>
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 Undefine the configuration for an inactive I<pool>.
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-- 
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1.8.5.3
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