[PATCH master] fs: align truncate return codes with POSIX

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Writing past end of a file results in a cryptic error code:

  barebox@board:/ cp /dev/zero /dev/mmc0.part
  write: Operation not permitted
  cp: Operation not permitted

Because the cdev's truncate is not implemented and as such partition
can't be increased in size. POSIX specifies EPERM as the correct return
code for truncate(2) in such a situation, but for write(2) it is ENOSPC.
Thus most truncate callbacks in barebox instead return ENOSPC, when
according to POSIX, EPERM would have been the correct error code to
propagate.

Switching all truncate drivers is a bit more involved, so for now let's
treat EPERM and ENOSPC instead when truncate fails to enlarge a file.

Reported-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 fs/fs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/fs.c b/fs/fs.c
index 752688b574a0..c463466e1be0 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -441,6 +441,8 @@ static ssize_t __write(FILE *f, const void *buf, size_t count)
 	if (f->size != FILE_SIZE_STREAM && f->pos + count > f->size) {
 		ret = fsdev_truncate(&f->fsdev->dev, f, f->pos + count);
 		if (ret) {
+			if (ret == -EPERM)
+				ret = -ENOSPC;
 			if (ret != -ENOSPC)
 				goto out;
 			count = f->size - f->pos;
-- 
2.30.2