Implement sync_file_range()

sync_file_range - sync a file segment with disk

In Linux, sync_file_range() accepts three flags:

       SYNC_FILE_RANGE_WAIT_BEFORE
              Wait  upon  write-out  of  all pages in the specified range that
              have already been submitted to the device driver  for  write-out
              before performing any write.

       SYNC_FILE_RANGE_WRITE
              Initiate  write-out  of  all  dirty pages in the specified range
              which are not presently submitted  write-out.   Note  that  even
              this  may  block if you attempt to write more than request queue
              size.

       SYNC_FILE_RANGE_WAIT_AFTER
              Wait upon write-out of all pages in the range  after  performing
              any write.

In this implementation:

SYNC_FILE_RANGE_WAIT_BEFORE without SYNC_FILE_RANGE_WAIT_AFTER isn't
supported right now.

SYNC_FILE_RANGE_WRITE is skipped. It should initiate write-out of  all
dirty pages, but it doesn't wait, so it should be safe to do nothing
while nobody uses SYNC_FILE_RANGE_WAIT_BEFORE.

SYNC_FILE_RANGE_WAIT_AFTER is equal to fdatasync(). In Linux,
sync_file_range() doesn't writes out the  file's  meta-data, but
fdatasync() does if a file size is changed.

PiperOrigin-RevId: 220730840
Change-Id: Iae5dfb23c2c916967d67cf1a1ad32f25eb3f6286

1 files changed, 7 insertions, 0 deletions

diff --git a/pkg/abi/linux/fs.go b/pkg/abi/linux/fs.go
index 7817bfb52..0b1c9f3db 100644
--- a/pkg/abi/linux/fs.go
+++ b/pkg/abi/linux/fs.go
@@ -73,3 +73,10 @@ type Statfs struct {
 	// Spare is unused.
 	Spare [4]uint64
 }
+
+// Sync_file_range flags, from include/uapi/linux/fs.h
+const (
+	SYNC_FILE_RANGE_WAIT_BEFORE = 1
+	SYNC_FILE_RANGE_WRITE       = 2
+	SYNC_FILE_RANGE_WAIT_AFTER  = 4
+)