1. An apparatus for multipath I/O (‘input/output’), the apparatus comprising a computer processor, a computer memory, a plurality of I/O adapters, and a memory controller, the memory controller configured to carry out: receiving asynchronously, for a single I/O operation from the plurality of I/O adapters, a request to access a memory page, where each request to access the memory page includes an adapter-specific tag; and for each request received by the memory controller: determining whether an adapter-specific tag has been assigned to the memory page; if an adapter-specific tag has not been assigned to the memory page: assigning, by the memory controller, the received adapter-specific tag to the memory page; and allowing, by the memory controller, access to the memory page; and if an adapter-specific tag has been assigned to the memory page, granting access to the memory page only when the received adapter-specific tag is the adapter-specific tag assigned to the memory page.