zx_pager_query_vmo_stats

NAME

Query pager related statistics on a pager owned VMO.

SYNOPSIS

#include <zircon/syscalls.h>

zx_status_t zx_pager_query_vmo_stats(zx_handle_t pager,
                                     zx_handle_t pager_vmo,
                                     uint32_t options,
                                     void* buffer,
                                     size_t buffer_size);

Description

Queries pager_vmo for any pager related statistics, e.g. whether pager_vmo has been modified. The pager_vmo must have previously been created from the pager by zx_pager_create_vmo().

options can be ZX_PAGER_RESET_VMO_STATS if the caller also wishes to reset the queried stats. An options value of 0 does not reset any state, and performs a pure query.

buffer should be a pointer to a zx_pager_vmo_stats_t struct that will hold the result of the query, and buffer_size should be large enough to accommodate the struct.

typedef struct zx_pager_vmo_stats {
  // Will be set to ZX_PAGER_VMO_STATS_MODIFIED if the VMO was modified, or 0 otherwise.
  // Note that this can be set to 0 if a previous zx_pager_query_vmo_stats() call specified the
  // ZX_PAGER_RESET_VMO_STATS option, which resets the modified state.
  uint32_t modified;
} zx_pager_vmo_stats_t;

Note that this call can have an effect on future zx_pager_query_vmo_stats() calls by consuming queryable state if the ZX_PAGER_RESET_VMO_STATS option is specified. For example, if a zx_vmo_write() is followed by two consecutive zx_pager_query_vmo_stats() with the ZX_PAGER_RESET_VMO_STATS option, only the first of those will see modified set to ZX_PAGER_VMO_STATS_MODIFIED. Since no further modifications took place after the first zx_pager_query_vmo_stats(), the second zx_pager_query_vmo_stats() will return modified as 0.

Rights

pager must be of type ZX_OBJ_TYPE_PAGER and have ZX_RIGHT_MANAGE_VMO.

pager_vmo must be of type ZX_OBJ_TYPE_VMO and have ZX_RIGHT_READ.

Return value

zx_pager_query_vmo_stats() returns ZX_OK on success. In the event of failure, a negative error value is returned.

Errors

ZX_ERR_BAD_HANDLE pager or pager_vmo is not a valid handle.

ZX_ERR_WRONG_TYPE pager is not a pager handle, or pager_vmo is not a VMO handle.

ZX_ERR_ACCESS_DENIED pager does not have ZX_RIGHT_MANAGE_VMO or pager_vmo does not have ZX_RIGHT_READ.

ZX_ERR_INVALID_ARGS pager_vmo is not a VMO created from pager, or options is neither 0 or ZX_PAGER_RESET_VMO_STATS, or buffer is an invalid pointer.

ZX_ERR_BUFFER_TOO_SMALL buffer_size is not large enough to accommodate zx_pager_vmo_stats_t.