Re: [Xen-devel] [PATCH v3 1/1] tools/hotplug: Scan xenstore once when attaching shared images files

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Mike Latimer writes ("[PATCH v3 1/1] tools/hotplug: Scan xenstore once when 
attaching shared images files"):
> During the attachment of a loopback mounted image file, the mode of all
> curent instances of this device already attached to other domains must be
> checked. This requires finding all loopback devices pointing to the inode
> of the shared image file, and then comparing the major and minor number of
> these devices to the major and minor number of every vbd device found in the
> xenstore database.
> 
> Prior to this patch, the entire xenstore database is walked for every instance
> of every loopback device pointing to the same shared image file. This process
> causes the block attachment process to becomes exponentially slower with every
> additional attachment of a shared image.
> 
> Rather than scanning all of xenstore for every instance of a shared loopback
> device, this patch creates a list of the major and minor numbers from all
> matching loopback devices. After generating this list, Xenstore is walked
> once, and major and minor numbers from every vbd are checked against the list.
> If a match is found, the mode of that vbd is checked for compatibility with
> the mode of the device being attached.

Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

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