abf38abec2
This commit introduces the `core.fsyncMethod` configuration knob, which can currently be set to `fsync` or `writeout-only`. The new writeout-only mode attempts to tell the operating system to flush its in-memory page cache to the storage hardware without issuing a CACHE_FLUSH command to the storage controller. Writeout-only fsync is significantly faster than a vanilla fsync on common hardware, since data is written to a disk-side cache rather than all the way to a durable medium. Later changes in this patch series will take advantage of this primitive to implement batching of hardware flushes. When git_fsync is called with FSYNC_WRITEOUT_ONLY, it may fail and the caller is expected to do an ordinary fsync as needed. On Apple platforms, the fsync system call does not issue a CACHE_FLUSH directive to the storage controller. This change updates fsync to do fcntl(F_FULLFSYNC) to make fsync actually durable. We maintain parity with existing behavior on Apple platforms by setting the default value of the new core.fsyncMethod option. Signed-off-by: Neeraj Singh <neerajsi@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
29 lines
688 B
C
29 lines
688 B
C
#include "git-compat-util.h"
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#include <winternl.h>
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#include "lazyload.h"
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int win32_fsync_no_flush(int fd)
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{
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IO_STATUS_BLOCK io_status;
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#define FLUSH_FLAGS_FILE_DATA_ONLY 1
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DECLARE_PROC_ADDR(ntdll.dll, NTSTATUS, NTAPI, NtFlushBuffersFileEx,
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HANDLE FileHandle, ULONG Flags, PVOID Parameters, ULONG ParameterSize,
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PIO_STATUS_BLOCK IoStatusBlock);
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if (!INIT_PROC_ADDR(NtFlushBuffersFileEx)) {
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errno = ENOSYS;
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return -1;
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}
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memset(&io_status, 0, sizeof(io_status));
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if (NtFlushBuffersFileEx((HANDLE)_get_osfhandle(fd), FLUSH_FLAGS_FILE_DATA_ONLY,
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NULL, 0, &io_status)) {
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errno = EINVAL;
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return -1;
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}
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return 0;
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}
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