bcachefs: Fix copy_to_user() usage in flush_buf()

copy_to_user() returns the number of bytes successfully copied - not an
errcode.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/debug.c b/fs/bcachefs/debug.c
index 404148b..75a3dc7 100644 (file)
--- a/fs/bcachefs/debug.c
+++ b/fs/bcachefs/debug.c
@@ -319,16 +319,16 @@ static ssize_t flush_buf(struct dump_iter *i)
 {
        if (i->buf.pos) {
                size_t bytes = min_t(size_t, i->buf.pos, i->size);
-               int err = copy_to_user(i->ubuf, i->buf.buf, bytes);
+               int copied = bytes - copy_to_user(i->ubuf, i->buf.buf, bytes);
 
-               if (err)
-                       return err;
+               i->ret   += copied;
+               i->ubuf  += copied;
+               i->size  -= copied;
+               i->buf.pos -= copied;
+               memmove(i->buf.buf, i->buf.buf + copied, i->buf.pos);
 
-               i->ret   += bytes;
-               i->ubuf  += bytes;
-               i->size  -= bytes;
-               i->buf.pos -= bytes;
-               memmove(i->buf.buf, i->buf.buf + bytes, i->buf.pos);
+               if (copied != bytes)
+                       return -EFAULT;
        }
 
        return i->size ? 0 : i->ret;