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This patch fixes a potential for I/O to hang and LVM commands

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to block when a mirror under a snapshot suffers a failure.

The problem has to do with label scanning.  When a mirror suffers
a failure, the kernel blocks I/O to prevent corruption.  When
LVM attempts to repair the mirror, it scans the devices on the
system for LVM labels.  While mirrors are skipped during this
scanning process, snapshot-origins are not.  When the origin is
scanned, it kicks up I/O to the mirror (which is blocked)
underneath - causing the label scan (an thus the repair operation)
to hang.

This patch simply bypasses snapshot-origin devices when doing
labels scans (while ignore_suspended_devices() is set).  This
fixes the issue.
This commit is contained in:
Jonathan Earl Brassow 2010-08-26 14:21:50 +00:00
parent fc86426b56
commit a71d6051ed
2 changed files with 16 additions and 0 deletions
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1
WHATS_NEW
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@ -1,5 +1,6 @@
Version 2.02.74 -
==================================
Like mirrors, don't scan origins if ignore_suspended_devices() is set.
Fix return type qualifier to avoid compiler warning. (2.02.69)
Automatically generate LSB Requires-Start for clvmd init script.
Fix return code of pvmove --abort PV.

15
lib/activate/dev_manager.c
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@ -175,6 +175,21 @@ int device_is_usable(struct device *dev)
log_debug("%s: Mirror device %s not usable.", dev_name(dev), name);
goto out;
}
/*
* Snapshot origin could be sitting on top of a mirror which
* could be blocking I/O. Skip snapshot origins entirely for
* now.
*
* FIXME: rather than skipping origin, check if mirror is
* underneath and if the mirror is blocking I/O.
*/
if (target_type && !strcmp(target_type, "snapshot-origin") &&
ignore_suspended_devices()) {
log_debug("%s: Snapshot-origin device %s not usable.",
dev_name(dev), name);
goto out;
}
} while (next);
/* FIXME Also check dependencies? */