mirror of
https://github.com/ceph/go-ceph
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c8f26a841b
Although it seems to be stable with the current Go versions, unsafe.Pointers that are created by applying arithmetic on nil pointers are explicitly not allowed[1], and could potentially lead to panics by the garbage collector. To be on the safe side, this change goes back to minimal inline wrappers for the callback registrations, which should be zero-cost. For the callbacks themselves fortunately no wrappers are required, because CGo happily converts void* to uintptr arguments. The potentially problematic VoidPtr helper is removed again. [1] https://golang.org/pkg/unsafe/#Pointer Signed-off-by: Sven Anderson <sven@redhat.com>
131 lines
4.1 KiB
Go
131 lines
4.1 KiB
Go
package rbd
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/*
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#cgo LDFLAGS: -lrbd
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#undef _GNU_SOURCE
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#include <errno.h>
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#include <stdlib.h>
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#include <rbd/librbd.h>
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extern int diffIterateCallback(uint64_t, size_t, int, uintptr_t);
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// inline wrapper to cast uintptr_t to void*
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static inline int wrap_rbd_diff_iterate2(rbd_image_t image,
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const char *fromsnapname, uint64_t ofs, uint64_t len, uint8_t include_parent,
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uint8_t whole_object, uintptr_t arg) {
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return rbd_diff_iterate2(image, fromsnapname, ofs, len, include_parent,
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whole_object, (void*)diffIterateCallback, (void*)arg);
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};
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*/
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import "C"
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import (
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"unsafe"
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"github.com/ceph/go-ceph/internal/callbacks"
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)
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var diffIterateCallbacks = callbacks.New()
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// DiffIncludeParent values control if the difference should include the parent
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// image.
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type DiffIncludeParent uint8
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// DiffWholeObject values control if the diff extents should cover the whole
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// object.
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type DiffWholeObject uint8
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// DiffIterateCallback defines the function signature needed for the
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// DiffIterate callback.
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//
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// The function will be called with the arguments: offset, length, exists, and
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// data. The offset and length correspond to the changed region of the image.
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// The exists value is set to zero if the region is known to be zeros,
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// otherwise it is set to 1. The data value is the extra data parameter that
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// was set on the DiffIterateConfig and is meant to be used for passing
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// arbitrary user-defined items to the callback function.
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//
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// The callback can trigger the iteration to terminate early by returning
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// a non-zero error code.
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type DiffIterateCallback func(uint64, uint64, int, interface{}) int
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// DiffIterateConfig is used to define the parameters of a DiffIterate call.
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// Callback, Offset, and Length should always be specified when passed to
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// DiffIterate. The other values are optional.
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type DiffIterateConfig struct {
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SnapName string
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Offset uint64
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Length uint64
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IncludeParent DiffIncludeParent
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WholeObject DiffWholeObject
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Callback DiffIterateCallback
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Data interface{}
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}
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const (
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// ExcludeParent will exclude the parent from the diff.
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ExcludeParent = DiffIncludeParent(0)
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// IncludeParent will include the parent in the diff.
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IncludeParent = DiffIncludeParent(1)
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// DisableWholeObject will not use the whole object in the diff.
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DisableWholeObject = DiffWholeObject(0)
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// EnableWholeObject will use the whole object in the diff.
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EnableWholeObject = DiffWholeObject(1)
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)
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// DiffIterate calls a callback on changed extents of an image.
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//
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// Calling DiffIterate will cause the callback specified in the
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// DiffIterateConfig to be called as many times as there are changed
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// regions in the image (controlled by the parameters as passed to librbd).
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//
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// See the documentation of DiffIterateCallback for a description of the
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// arguments to the callback and the return behavior.
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//
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// Implements:
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// int rbd_diff_iterate2(rbd_image_t image,
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// const char *fromsnapname,
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// uint64_t ofs, uint64_t len,
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// uint8_t include_parent, uint8_t whole_object,
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// int (*cb)(uint64_t, size_t, int, void *),
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// void *arg);
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func (image *Image) DiffIterate(config DiffIterateConfig) error {
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if err := image.validate(imageIsOpen); err != nil {
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return err
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}
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if config.Callback == nil {
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return rbdError(C.EINVAL)
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}
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var cSnapName *C.char
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if config.SnapName != NoSnapshot {
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cSnapName = C.CString(config.SnapName)
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defer C.free(unsafe.Pointer(cSnapName))
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}
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cbIndex := diffIterateCallbacks.Add(config)
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defer diffIterateCallbacks.Remove(cbIndex)
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ret := C.wrap_rbd_diff_iterate2(
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image.image,
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cSnapName,
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C.uint64_t(config.Offset),
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C.uint64_t(config.Length),
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C.uint8_t(config.IncludeParent),
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C.uint8_t(config.WholeObject),
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C.uintptr_t(cbIndex))
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return getError(ret)
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}
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//export diffIterateCallback
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func diffIterateCallback(
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offset C.uint64_t, length C.size_t, exists C.int, index uintptr) C.int {
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v := diffIterateCallbacks.Lookup(index)
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config := v.(DiffIterateConfig)
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return C.int(config.Callback(
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uint64(offset), uint64(length), int(exists), config.Data))
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}
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