call fallocate only if necessary

On some files below /sys mmap(2) works but posix_fallocate(3) does not.
(e.g. some but not all of /sys/bus/pci/devices/*/resource* behave like
this.)

So only call posix_fallocate() if the file to write to is too small.

Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/memtool.c b/memtool.c
index 28d886e..b790c8e 100644
--- a/memtool.c
+++ b/memtool.c
@@ -233,7 +233,7 @@ static void *memmap(const char *file, off_t addr, size_t *size, int readonly)
 				/* truncating */
 				*size = s.st_size - addr;
 
-		} else {
+		} else if (s.st_size < addr + *size) {
 			int ret = posix_fallocate(memfd, addr, *size);
 			if (ret) {
 				errno = ret;