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Use copy_file_range on Linux #15

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Use copy_file_range on Linux #15

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56 changes: 56 additions & 0 deletions src/bsp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -647,6 +647,12 @@ static void scratch_open(int mode) {
fchmod(scratch_fd, mode);
}

#if defined(__linux__) && defined(__GLIBC__)
# if __GLIBC__ == 2 && __GLIBC_MINOR >= 27
# define HAVE_COPY_FILE_RANGE 1
# endif
#endif

static void scratch_clone(void) {
int fd_orig = open(source_fname, O_RDONLY);
if (fd_orig == -1) {
Expand Down Expand Up @@ -690,8 +696,58 @@ static void scratch_clone(void) {
}
#endif

#if defined(HAVE_COPY_FILE_RANGE)
bool use_copy_file_range = true;
#endif

while (wanted != 0) {
ssize_t got;

#if defined(HAVE_COPY_FILE_RANGE)
if (use_copy_file_range) {
if (wanted == -1) {
off_t cur = lseek(fd_orig, 0, SEEK_CUR);
if (cur == -1) {
fprintf(stderr, "%s: lseek(%s): %s\n", argv0, source_fname, strerror(errno));
exit(-1);
}

off_t end = lseek(fd_orig, 0, SEEK_END);
if (end == -1) {
fprintf(stderr, "%s: lseek(%s): %s\n", argv0, source_fname, strerror(errno));
exit(-1);
}

wanted = end - cur;
if (wanted == 0)
goto done;
}

got = copy_file_range(fd_orig, NULL, scratch_fd, NULL, wanted, 0);

if (got == 0)
goto done;

if (got == -1) {
switch (errno) {
case EXDEV:
use_copy_file_range = false;
continue;
default:
fprintf(stderr, "%s: copy_file_range(%s, %s): %s\n", argv0, source_fname, scratch_fname ? scratch_fname : "[ephemeral]", strerror(errno));
exit(-1);
}
}

target_length += got;
if (wanted != -1) {
wanted -= got;
}

continue;
}
#endif

char buffer[2048];

got = read(fd_orig, buffer,
Expand Down