[PATCH 2/3] libfile: open_and_lseek: enlarge small files enough to make lseek possible

[Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>]

This makes the following do the expected thing:

	barebox@barebox sandbox:/ ls -l lala
	-rwxrwxrwx              4 lala
	barebox@barebox sandbox:/ mw -d lala 72 0

Without this patch mw dies with

	lseek: Invalid argument

memset, memcpy and probably others benefit in the same way.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
---
 lib/libfile.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/lib/libfile.c b/lib/libfile.c
index 83c6399a5b39..01c59cdb80fe 100644
--- a/lib/libfile.c
+++ b/lib/libfile.c
@@ -510,6 +510,24 @@ int open_and_lseek(const char *filename, int mode, loff_t pos)
 	if (!pos)
 		return fd;
 
+	if (mode & (O_WRONLY | O_RDWR)) {
+		struct stat s;
+
+		ret = fstat(fd, &s);
+		if (ret) {
+			perror("ftruncate");
+			return ret;
+		}
+
+		if (s.st_size < pos) {
+			ret = ftruncate(fd, pos);
+			if (ret) {
+				perror("ftruncate");
+				return ret;
+			}
+		}
+	}
+
 	ret = lseek(fd, pos, SEEK_SET);
 	if (ret == -1) {
 		perror("lseek");
-- 
2.18.0


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