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pager_detach_vmo.md

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zx_pager_detach_vmo

SUMMARY

Detaches a vmo from a pager.

DECLARATION

#include <zircon/syscalls.h>

zx_status_t zx_pager_detach_vmo(zx_handle_t pager, zx_handle_t vmo);

DESCRIPTION

Detaching vmo from pager causes the kernel to stop queuing page requests for the vmo. Subsequent accesses that would have generated page requests will instead fail.

No new ZX_PAGER_VMO_READ and ZX_PAGER_VMO_DIRTY requests will be generated after detaching, but some requests may still be in flight. The pager service is free to ignore these requests, as the kernel will resume and fault the threads that generated these requests. The final request the pager service will receive is a ZX_PAGER_VMO_COMPLETE request.

The kernel is free to evict clean pages from detached vmos, but will retain any dirty pages. Upon receiving the ZX_PAGER_VMO_COMPLETE request, the pager service is expected to query these ranges with zx_pager_query_dirty_ranges() and write them back with zx_pager_op_range() ZX_PAGER_OP_WRITEBACK_BEGIN and ZX_PAGER_OP_WRITEBACK_END. Once they have been written back, these pages will become clean again, so the kernel is free to evict them.

RIGHTS

pager must be of type ZX_OBJ_TYPE_PAGER.

vmo must be of type ZX_OBJ_TYPE_VMO.

RETURN VALUE

zx_pager_detach_vmo() returns ZX_OK on success, or one of the following error codes on failure.

ERRORS

ZX_ERR_BAD_HANDLE pager or vmo is not a valid handle.

ZX_ERR_WRONG_TYPE pager is not a pager handle or vmo is not a vmo handle.

ZX_ERR_INVALID_ARGS vmo is not a vmo created from pager.

SEE ALSO