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Code Releases Activity

devmapper: ensure that UdevWait is called after calls to setCookie

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Recent changes to devmapper broke the implicit requirement that UdevWait be
called after every call to task.setCookie.  Failure to do so results in leaks of
semaphores in the LVM code, eventually leading to semaphore exhaustion.
Previously this was handled by calling UdevWait in a ubiquitous defer function.
While there was initially some concern with deferring the UdevWait function
would cause some amount of race possibiliy, the fact that we never return the
cookie value or any value used to find it, makes that possibility seem unlikely,
so lets go back to that method

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
This commit is contained in:
Neil Horman 2017-06-19 12:11:48 -04:00
parent 630b9a45d2
commit 23dcfec140
1 changed files with 15 additions and 9 deletions
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24
pkg/devicemapper/devmapper.go
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@ -333,6 +333,7 @@ func RemoveDevice(name string) error {
if err := task.setCookie(cookie, 0); err != nil {
return fmt.Errorf("devicemapper: Can not set cookie: %s", err)
}
defer UdevWait(cookie)
dmSawBusy = false // reset before the task is run
if err = task.run(); err != nil {
@ -342,7 +343,7 @@ func RemoveDevice(name string) error {
return fmt.Errorf("devicemapper: Error running RemoveDevice %s", err)
}
return UdevWait(cookie)
return nil
}
// RemoveDeviceDeferred is a useful helper for cleaning up a device, but deferred.
@ -368,10 +369,6 @@ func RemoveDeviceDeferred(name string) error {
return fmt.Errorf("devicemapper: Can not set cookie: %s", err)
}
if err = task.run(); err != nil {
return fmt.Errorf("devicemapper: Error running RemoveDeviceDeferred %s", err)
}
// libdevmapper and udev relies on System V semaphore for synchronization,
// semaphores created in `task.setCookie` will be cleaned up in `UdevWait`.
// So these two function call must come in pairs, otherwise semaphores will
@ -381,8 +378,13 @@ func RemoveDeviceDeferred(name string) error {
// this call will not wait for the deferred removal's final executing, since no
// udev event will be generated, and the semaphore's value will not be incremented
// by udev, what UdevWait is just cleaning up the semaphore.
defer UdevWait(cookie)
return UdevWait(cookie)
if err = task.run(); err != nil {
return fmt.Errorf("devicemapper: Error running RemoveDeviceDeferred %s", err)
}
return nil
}
// CancelDeferredRemove cancels a deferred remove for a device.
@ -476,12 +478,13 @@ func CreatePool(poolName string, dataFile, metadataFile *os.File, poolBlockSize
if err := task.setCookie(cookie, flags); err != nil {
return fmt.Errorf("devicemapper: Can't set cookie %s", err)
}
defer UdevWait(cookie)
if err := task.run(); err != nil {
return fmt.Errorf("devicemapper: Error running deviceCreate (CreatePool) %s", err)
}
return UdevWait(cookie)
return nil
}
// ReloadPool is the programmatic example of "dmsetup reload".
@ -661,12 +664,13 @@ func ResumeDevice(name string) error {
if err := task.setCookie(cookie, 0); err != nil {
return fmt.Errorf("devicemapper: Can't set cookie %s", err)
}
defer UdevWait(cookie)
if err := task.run(); err != nil {
return fmt.Errorf("devicemapper: Error running deviceResume %s", err)
}
return UdevWait(cookie)
return nil
}
// CreateDevice creates a device with the specified poolName with the specified device id.
@ -759,11 +763,13 @@ func activateDevice(poolName string, name string, deviceID int, size uint64, ext
return fmt.Errorf("devicemapper: Can't set cookie %s", err)
}
defer UdevWait(cookie)
if err := task.run(); err != nil {
return fmt.Errorf("devicemapper: Error running deviceCreate (ActivateDevice) %s", err)
}
return UdevWait(cookie)
return nil
}
// CreateSnapDeviceRaw creates a snapshot device. Caller needs to suspend and resume the origin device if it is active.