From: Neeraj Singh <neerajsi@xxxxxxxxxxxxx>
This commit adds a win32 implementation for fsync_no_flush that is
called git_fsync. The 'NtFlushBuffersFileEx' function being called is
available since Windows 8. If the function is not available, we
return -1 and Git falls back to doing a full fsync.
The operating system is told to flush data only without a hardware
flush primitive. A later full fsync will cause the metadata log
to be flushed and then the disk cache to be flushed on NTFS and
ReFS. Other filesystems will treat this as a full flush operation.
I added a new file here for this system call so as not to conflict with
downstream changes in the git-for-windows repository related to fscache.
Signed-off-by: Neeraj Singh <neerajsi@xxxxxxxxxxxxx>
---
compat/mingw.h | 3 +++
compat/win32/flush.c | 29 +++++++++++++++++++++++++++++
config.mak.uname | 2 ++
contrib/buildsystems/CMakeLists.txt | 3 ++-
wrapper.c | 4 ++++
5 files changed, 40 insertions(+), 1 deletion(-)
create mode 100644 compat/win32/flush.c
diff --git a/compat/mingw.h b/compat/mingw.h
index 87944dfec72..b5c950f1e30 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -329,6 +329,9 @@ int mingw_getpagesize(void);
#define getpagesize mingw_getpagesize
#endif
+int win32_fsync_no_flush(int fd);
+#define fsync_no_flush win32_fsync_no_flush
+
struct rlimit {
unsigned int rlim_cur;
};
diff --git a/compat/win32/flush.c b/compat/win32/flush.c
new file mode 100644
index 00000000000..c013920ce37
--- /dev/null
+++ b/compat/win32/flush.c
@@ -0,0 +1,29 @@
+#include "../../git-compat-util.h"
+#include <winternl.h>
+#include "lazyload.h"
+
+int win32_fsync_no_flush(int fd)
+{
+ IO_STATUS_BLOCK io_status;
+
+#define FLUSH_FLAGS_FILE_DATA_ONLY 1
+
+ DECLARE_PROC_ADDR(ntdll.dll, NTSTATUS, NtFlushBuffersFileEx,
+ HANDLE FileHandle, ULONG Flags, PVOID Parameters, ULONG ParameterSize,
+ PIO_STATUS_BLOCK IoStatusBlock);
+
+ if (!INIT_PROC_ADDR(NtFlushBuffersFileEx)) {
+ errno = ENOSYS;
+ return -1;
+ }
+
+ /* See https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/ntifs/nf-ntifs-ntflushbuffersfileex */
+ memset(&io_status, 0, sizeof(io_status));
+ if (NtFlushBuffersFileEx((HANDLE)_get_osfhandle(fd), FLUSH_FLAGS_FILE_DATA_ONLY,
+ NULL, 0, &io_status)) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ return 0;
+}
diff --git a/config.mak.uname b/config.mak.uname
index 8c07f2265a8..ef1fd109b74 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -450,6 +450,7 @@ endif
CFLAGS =
BASIC_CFLAGS = -nologo -I. -Icompat/vcbuild/include -DWIN32 -D_CONSOLE -DHAVE_STRING_H -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_DEPRECATE
COMPAT_OBJS = compat/msvc.o compat/winansi.o \
+ compat/win32/flush.o \
compat/win32/path-utils.o \
compat/win32/pthread.o compat/win32/syslog.o \
compat/win32/trace2_win32_process_info.o \
@@ -624,6 +625,7 @@ ifneq (,$(findstring MINGW,$(uname_S)))
COMPAT_CFLAGS += -DSTRIP_EXTENSION=\".exe\"
COMPAT_OBJS += compat/mingw.o compat/winansi.o \
compat/win32/trace2_win32_process_info.o \
+ compat/win32/flush.o \
compat/win32/path-utils.o \
compat/win32/pthread.o compat/win32/syslog.o \
compat/win32/dirent.o
diff --git a/contrib/buildsystems/CMakeLists.txt b/contrib/buildsystems/CMakeLists.txt
index 171b4124afe..b573a5ee122 100644
--- a/contrib/buildsystems/CMakeLists.txt
+++ b/contrib/buildsystems/CMakeLists.txt
@@ -261,7 +261,8 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
NOGDI OBJECT_CREATION_MODE=1 __USE_MINGW_ANSI_STDIO=0
USE_NED_ALLOCATOR OVERRIDE_STRDUP MMAP_PREVENTS_DELETE USE_WIN32_MMAP
UNICODE _UNICODE HAVE_WPGMPTR ENSURE_MSYSTEM_IS_SET)
- list(APPEND compat_SOURCES compat/mingw.c compat/winansi.c compat/win32/path-utils.c
+ list(APPEND compat_SOURCES compat/mingw.c compat/winansi.c
+ compat/win32/flush.c compat/win32/path-utils.c
compat/win32/pthread.c compat/win32mmap.c compat/win32/syslog.c
compat/win32/trace2_win32_process_info.c compat/win32/dirent.c
compat/nedmalloc/nedmalloc.c compat/strdup.c)
diff --git a/wrapper.c b/wrapper.c
index 37a8b61a7df..d951306b33e 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -563,6 +563,10 @@ int git_fsync(int fd, enum fsync_action action)
SYNC_FILE_RANGE_WAIT_AFTER);
#endif
+#ifdef fsync_no_flush
+ return fsync_no_flush(fd);
+#endif
+
errno = ENOSYS;
return -1;
}
--
gitgitgadget
