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NAME

pmem2_vm_reservation_new(), pmem2_vm_reservation_delete() - creates or deletes an instance of virtual memory reservation

SYNOPSIS

    #include <libpmem2.h>

    struct pmem2_vm_reservation;
    int pmem2_vm_reservation_new(struct pmem2_vm_reservation **rsv_ptr,
            void *addr, size_t size);
    int pmem2_vm_reservation_delete(struct pmem2_vm_reservation **rsv_ptr);

DESCRIPTION

The pmem2_vm_reservation_new() function creates a new blank mapping in the virtual address space of the calling process. Reservation serves as a placeholder of a given size on which sources can be mapped.

For the function to succeed, the addr must be either aligned to an appropriate allocation granularity or NULL, the size always has to be aligned to an appropriate OS allocation granularity.

libpmem2(7) library chooses the largest page alignment for the reservation based on size. If the chosen alignment is different than the OS allocation granularity, then the underlying size of the reservation can be bigger than the value presented to the user. Largest page alignment functionality is limited to POSIX systems.

If the pmem2_vm_reservation_new() succeeds in creating a reservation, it instantiates a new struct pmem2_vm_reservation object describing the reservation. The pointer to this object is stored in the user-provided variable via the rsv_ptr pointer. If the function fails, an appropriate error value will be returned. For a list of possible return values please see RETURN VALUE

After instantiating an object via the pmem2_vm_reservation_new() function, it may be disposed of using the pmem2_vm_reservation_delete() function.

The pmem2_vm_reservation_delete() function destroys the object describing the reservation and unmaps virtual memory region the *struct pmem2_vm_reservation** had assigned during the initialization. For the delete function to succeed, it is required that the reservation passed via the rsv_ptr pointer does not contain any mappings.

RETURN VALUE

The pmem2_vm_reservation_new() and pmem2_vm_reservation_delete() functions return 0 on success or a negative error code on failure.

The function returns 0 on success or a negative error code on failure.

ERRORS

The pmem2_vm_reservation_new() function can fail with the following errors:

•   PMEM2_E_ADDRESS_UNALIGNED - argument addr is not aligned to the appropriate allocation granularity.

•   PMEM2_E_MAPPING_EXISTS - mapping already exists in the range (addr, addr + size).

It can also return -EAGAIN, -ENOMEM from the underlying mmap(2) function and -ENOMEM in case of insufficient memory to allocate an instance of struct pmem2_vm_reservation.

The pmem2_vm_reservation_delete() function can fail with the following errors:

•   PMEM2_E_RESERVATION_NOT_EMPTY - reservation contains mappings.

It can also return errors from the underlying munmap(2) function.

SEE ALSO

pmem2_config_set_vm_reservation(3), libpmem2(7) and <https://pmem.io>