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Mike Latimer
d76add5b4b
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. Signed-off-by: Mike Latimer <mlatimer@suse.com> Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>