Am 22.04.2016 um 16:31 schrieb Johannes Schindelin:
Often we are mmap()ing read-only. In those cases, it is wasteful to map in
copy-on-write mode. Even worse: it can cause errors where we run out of
space in the page file.
So let's be extra careful to map files in read-only mode whenever
possible.
Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
---
compat/win32mmap.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/compat/win32mmap.c b/compat/win32mmap.c
index 3a39f0f..b836169 100644
--- a/compat/win32mmap.c
+++ b/compat/win32mmap.c
@@ -22,14 +22,15 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of
die("Invalid usage of mmap when built with USE_WIN32_MMAP");
hmap = CreateFileMapping((HANDLE)_get_osfhandle(fd), NULL,
- PAGE_WRITECOPY, 0, 0, NULL);
+ prot == PROT_READ ? PAGE_READONLY : PAGE_WRITECOPY, 0, 0, NULL);
As long as we use this implementation with MAP_PRIVATE, PAGE_WRITECOPY
is the right setting. Should we insert a check for MAP_PRIVATE to catch
unexpected use-cases (think of the index-helper daemon effort)?
if (!hmap) {
errno = EINVAL;
return MAP_FAILED;
}
- temp = MapViewOfFileEx(hmap, FILE_MAP_COPY, h, l, length, start);
+ temp = MapViewOfFileEx(hmap, prot == PROT_READ ?
+ FILE_MAP_READ : FILE_MAP_COPY, h, l, length, start);
Same here: FILE_MAP_COPY is the right choice for MAP_SHARED mmaps.
if (!CloseHandle(hmap))
warning("unable to close file mapping handle");
Except for these mental notes, I've no comments on this series. Looks good.
-- Hannes
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