cephfs: add support for cephfs file block diff api

This commit adds support for cephfs file block diff
APIs which gives a list of changed blocks with in a
file between two snapshots.

Signed-off-by: Rakshith R <[email protected]>
(cherry picked from commit 03e146b)

Co-authored-by: Praveen M <[email protected]>

Author: Rakshith-R

cephfs/block_diff.go

@@ -0,0 +1,303 @@
+//go:build ceph_preview
+
+package cephfs
+
+/*
+#cgo LDFLAGS: -lcephfs
+#cgo CPPFLAGS: -D_FILE_OFFSET_BITS=64
+#include <stdlib.h>
+#include <dirent.h>
+#include <cephfs/libcephfs.h>
+
+// Types and constants are copied from libcephfs.h with added "_" as prefix. This
+// prevents redefinition of the types on libcephfs versions that have them
+// already.
+
+struct _ceph_file_blockdiff_result;
+
+typedef struct
+{
+  struct ceph_mount_info* cmount;
+  struct _ceph_file_blockdiff_result* blockp;
+} _ceph_file_blockdiff_info;
+
+typedef struct
+{
+  uint64_t offset;
+  uint64_t len;
+} _cblock;
+
+typedef struct
+{
+  uint64_t num_blocks;
+  struct _cblock *b;
+} _ceph_file_blockdiff_changedblocks;
+
+// ceph_file_blockdiff_init_fn matches the ceph_file_blockdiff_init function signature.
+typedef int(*ceph_file_blockdiff_init_fn)(struct ceph_mount_info* cmount,
+                                  const char* root_path,
+                                  const char* rel_path,
+                                  const char* snap1,
+                                  const char* snap2,
+                                  _ceph_file_blockdiff_info* out_info);
+
+// ceph_file_blockdiff_init_dlsym take *fn as ceph_file_blockdiff_init and calls the dynamically loaded
+// ceph_file_blockdiff_init function passed as 1st argument.
+static inline int ceph_file_blockdiff_init_dlsym(void *fn,
+                                  struct ceph_mount_info* cmount,
+                                  const char* root_path,
+                                  const char* rel_path,
+                                  const char* snap1,
+                                  const char* snap2,
+                                  _ceph_file_blockdiff_info* out_info) {
+	// cast function pointer fn to ceph_file_blockdiff_init and call the function
+	return ((ceph_file_blockdiff_init_fn) fn)(cmount, root_path, rel_path, snap1, snap2, out_info);
+}
+
+// ceph_file_blockdiff_fn matches the ceph_file_blockdiff function signature.
+typedef int(*ceph_file_blockdiff_fn)(_ceph_file_blockdiff_info* info,
+                                  _ceph_file_blockdiff_changedblocks* blocks);
+
+// ceph_file_blockdiff_dlsym take *fn as ceph_file_blockdiff and calls the dynamically loaded
+// ceph_file_blockdiff function passed as 1st argument.
+static inline int ceph_file_blockdiff_dlsym(void *fn,
+                                  _ceph_file_blockdiff_info* info,
+                                  _ceph_file_blockdiff_changedblocks* blocks) {
+	// cast function pointer fn to ceph_file_blockdiff and call the function
+	return ((ceph_file_blockdiff_fn) fn)(info, blocks);
+}
+
+// ceph_free_file_blockdiff_buffer_fn matches the ceph_free_file_blockdiff_buffer function signature.
+typedef void(*ceph_free_file_blockdiff_buffer_fn)(_ceph_file_blockdiff_changedblocks* blocks);
+
+// ceph_free_file_blockdiff_buffer_dlsym take *fn as ceph_free_file_blockdiff_buffer and calls the dynamically loaded
+// ceph_free_file_blockdiff_buffer function passed as 1st argument.
+static inline void ceph_free_file_blockdiff_buffer_dlsym(void *fn,
+                                  _ceph_file_blockdiff_changedblocks* blocks) {
+	// cast function pointer fn to ceph_free_file_blockdiff_buffer and call the function
+	((ceph_free_file_blockdiff_buffer_fn) fn)(blocks);
+}
+
+// ceph_file_blockdiff_finish_fn matches the ceph_file_blockdiff_finish function signature.
+typedef int(*ceph_file_blockdiff_finish_fn)(_ceph_file_blockdiff_info* info);
+
+// ceph_file_blockdiff_finish_dlsym take *fn as ceph_file_blockdiff_finish and calls the dynamically loaded
+// ceph_file_blockdiff_finish function passed as 1st argument.
+static inline int ceph_file_blockdiff_finish_dlsym(void *fn,
+                                  _ceph_file_blockdiff_info* info) {
+	// cast function pointer fn to ceph_file_blockdiff_finish and call the function
+	return ((ceph_file_blockdiff_finish_fn) fn)(info);
+}
+*/
+import "C"
+
+import (
+	"fmt"
+	"sync"
+	"unsafe"
+
+	"github.com/ceph/go-ceph/internal/dlsym"
+)
+
+var (
+	cephFileBlockDiffInitOnce       sync.Once
+	cephFileBlockDiffOnce           sync.Once
+	cephFreeFileBlockDiffBufferOnce sync.Once
+	cephFileBlockDiffFinishOnce     sync.Once
+
+	cephFileBlockDiffInitErr       error
+	cephFileBlockDiffErr           error
+	cephFreeFileBlockDiffBufferErr error
+	cephFileBlockDiffFinishErr     error
+
+	cephFileBlockDiffInit       unsafe.Pointer
+	cephFileBlockDiff           unsafe.Pointer
+	cephFreeFileBlockDiffBuffer unsafe.Pointer
+	cephFileBlockDiffFinish     unsafe.Pointer
+)
+
+// FileBlockDiffInfo is a struct that holds the block diff stream handle.
+type FileBlockDiffInfo struct {
+	more                  bool
+	cephFileBlockDiffInfo *C._ceph_file_blockdiff_info
+}
+
+// ChangedBlock is a struct that holds the offset and length of a block.
+type ChangedBlock struct {
+	Offset uint64
+	Len    uint64
+}
+
+// FileBlockDiffChangedBlocks is a struct that holds the number of blocks
+// and list of Changed Blocks.
+type FileBlockDiffChangedBlocks struct {
+	NumBlocks     uint64
+	ChangedBlocks []ChangedBlock
+}
+
+// FileBlockDiffInit initializes the block diff stream to get file block deltas.
+// It takes the mount handle, root path, relative path, snapshot names and returns
+// a FileBlockDiffInfo struct that contains the block diff stream handle.
+//
+// Implements:
+//
+//	int ceph_file_blockdiff_init(struct ceph_mount_info* cmount,
+//								const char* root_path,
+//								const char* rel_path,
+//								const char* snap1,
+//								const char* snap2,
+//								struct ceph_file_blockdiff_info* out_info);
+func FileBlockDiffInit(mount *MountInfo, rootPath, relPath, snap1, snap2 string) (*FileBlockDiffInfo, error) {
+	if mount == nil || rootPath == "" || relPath == "" ||
+		snap1 == "" || snap2 == "" {
+		return nil, errInvalid
+	}
+	cRootPath := C.CString(rootPath)
+	cRelPath := C.CString(relPath)
+	cSnap1 := C.CString(snap1)
+	cSnap2 := C.CString(snap2)
+
+	// Load the ceph_file_blockdiff_init function from the shared library.
+	cephFileBlockDiffInitOnce.Do(func() {
+		cephFileBlockDiffInit, cephFileBlockDiffInitErr = dlsym.LookupSymbol("ceph_file_blockdiff_init")
+	})
+	if cephFileBlockDiffInitErr != nil {
+		return nil, fmt.Errorf("%w: %w", ErrNotImplemented, cephFileBlockDiffInitErr)
+	}
+
+	rawCephBlockDiffInfo := &C._ceph_file_blockdiff_info{}
+
+	// Call the ceph_file_blockdiff_init function with the provided arguments.
+	ret := C.ceph_file_blockdiff_init_dlsym(cephFileBlockDiffInit,
+		mount.mount,
+		cRootPath,
+		cRelPath,
+		cSnap1,
+		cSnap2,
+		rawCephBlockDiffInfo,
+	)
+	if ret != 0 {
+		return nil, getError(ret)
+	}
+
+	cephFileBlockDiffInfo := &FileBlockDiffInfo{
+		cephFileBlockDiffInfo: rawCephBlockDiffInfo,
+		more:                  true,
+	}
+
+	return cephFileBlockDiffInfo, nil
+}
+
+// validate checks if the FileBlockDiffInfo struct is valid.
+func (info *FileBlockDiffInfo) validate() error {
+	if info.cephFileBlockDiffInfo == nil {
+		return errInvalid
+	}
+
+	return nil
+}
+
+// Read retrieves the next set of changed blocks for a file.
+//
+// Implements:
+//
+//	int ceph_file_blockdiff(struct ceph_file_blockdiff_info* info,
+//							struct ceph_file_blockdiff_changedblocks* blocks);
+func (info *FileBlockDiffInfo) Read() (*FileBlockDiffChangedBlocks, error) {
+	err := info.validate()
+	if err != nil {
+		return nil, err
+	}
+
+	// Load the ceph_file_blockdiff function from the shared library.
+	cephFileBlockDiffOnce.Do(func() {
+		cephFileBlockDiff, cephFileBlockDiffErr = dlsym.LookupSymbol("ceph_file_blockdiff")
+	})
+	if cephFileBlockDiffErr != nil {
+		return nil, fmt.Errorf("%w: %w", ErrNotImplemented, cephFileBlockDiffErr)
+	}
+	cephFreeFileBlockDiffBufferOnce.Do(func() {
+		cephFreeFileBlockDiffBuffer, cephFreeFileBlockDiffBufferErr = dlsym.LookupSymbol("ceph_free_file_blockdiff_buffer")
+	})
+	if cephFreeFileBlockDiffBufferErr != nil {
+		return nil, fmt.Errorf("%w: %w", ErrNotImplemented, cephFreeFileBlockDiffBufferErr)
+	}
+
+	rawCephBlockDiffChangedBlocks := &C._ceph_file_blockdiff_changedblocks{}
+
+	// Call the ceph_file_blockdiff function with the provided arguments.
+	ret := C.ceph_file_blockdiff_dlsym(cephFileBlockDiff,
+		info.cephFileBlockDiffInfo,
+		rawCephBlockDiffChangedBlocks,
+	)
+	if ret < 0 {
+		return nil, getError(ret)
+	}
+	// if ret > 0 indicates there is no more entries after this call.
+	info.more = (ret > 0)
+
+	// Free the memory allocated for the blocks by ceph_file_blockdiff.
+	defer C.ceph_free_file_blockdiff_buffer_dlsym(cephFreeFileBlockDiffBuffer,
+		rawCephBlockDiffChangedBlocks)
+
+	cNumBlocks := uint64(rawCephBlockDiffChangedBlocks.num_blocks)
+
+	// Convert the C struct to Go struct.
+	cBlocks := make([]ChangedBlock, int(cNumBlocks))
+	if cNumBlocks == 0 {
+		return &FileBlockDiffChangedBlocks{
+			NumBlocks:     0,
+			ChangedBlocks: cBlocks,
+		}, nil
+	}
+
+	currentCBlock := (*C._cblock)(unsafe.Pointer(rawCephBlockDiffChangedBlocks.b))
+	for i := uint64(0); i < cNumBlocks; i++ {
+		cBlocks[i] = ChangedBlock{
+			Offset: uint64(currentCBlock.offset),
+			Len:    uint64(currentCBlock.len),
+		}
+		currentCBlock = (*C._cblock)(unsafe.Pointer(uintptr(unsafe.Pointer(currentCBlock)) + unsafe.Sizeof(C._cblock{})))
+	}
+
+	return &FileBlockDiffChangedBlocks{
+		NumBlocks:     cNumBlocks,
+		ChangedBlocks: cBlocks,
+	}, nil
+}
+
+// More returns true if there are more entries to read in the block diff stream.
+func (info *FileBlockDiffInfo) More() bool {
+	return info.more
+}
+
+// Close closes the block diff stream.
+//
+// Implements:
+//
+//	int ceph_file_blockdiff_finish(struct ceph_file_blockdiff_info* info);
+func (info *FileBlockDiffInfo) Close() error {
+	err := info.validate()
+	if err != nil {
+		return err
+	}
+
+	// Load the ceph_file_blockdiff_finish function from the shared library.
+	cephFileBlockDiffFinishOnce.Do(func() {
+		cephFileBlockDiffFinish, cephFileBlockDiffFinishErr = dlsym.LookupSymbol("ceph_file_blockdiff_finish")
+	})
+	if cephFileBlockDiffFinishErr != nil {
+		return fmt.Errorf("%w: %w", ErrNotImplemented, cephFileBlockDiffFinishErr)
+	}
+
+	// Call the ceph_file_blockdiff_finish function with the provided arguments.
+	ret := C.ceph_file_blockdiff_finish_dlsym(
+		cephFileBlockDiffFinish,
+		info.cephFileBlockDiffInfo,
+	)
+	if ret != 0 {
+		return getError(ret)
+	}
+
+	return nil
+}