vfs: Return -ENXIO for negative SEEK_HOLE / SEEK_DATA offsets

In generic_file_llseek_size, return -ENXIO for negative offsets as well
as offsets beyond EOF.  This affects filesystems which don't implement
SEEK_HOLE / SEEK_DATA internally, possibly because they don't support
holes.

Fixes xfstest generic/448.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/read_write.c

@@ -112,7 +112,7 @@ generic_file_llseek_size(struct file *file, loff_t offset, int whence,
 		 * In the generic case the entire file is data, so as long as
 		 * offset isn't at the end of the file then the offset is data.
 		 */
-		if (offset >= eof)
+		if ((unsigned long long)offset >= eof)
 			return -ENXIO;
 		break;
 	case SEEK_HOLE:
@@ -120,7 +120,7 @@ generic_file_llseek_size(struct file *file, loff_t offset, int whence,
 		 * There is a virtual hole at the end of the file, so as long as
 		 * offset isn't i_size or larger, return i_size.
 		 */
-		if (offset >= eof)
+		if ((unsigned long long)offset >= eof)
 			return -ENXIO;
 		offset = eof;
 		break;