drm/i915: set O_LARGEFILE in __create_shmem()

Without O_LARGEFILE, file->f_op->write_iter calls
generic_write_check_limits(), which enforces a 2GB (MAX_NON_LFS) limit,
causing -EFBIG on large writes.

In shmem_pwrite(), this error is later masked as -EIO due to the error
handling order, leading to igt failures like gen9_exec_parse(bb-large).

Set O_LARGEFILE in __create_shmem() to prevent -EFBIG on large writes.

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202508081029.343192ec-lkp@intel.com
Fixes: 048832a ("drm/i915: Refactor shmem_pwrite() to use kiocb and write_iter")
Signed-off-by: Taotao Chen <chentaotao@didiglobal.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://lore.kernel.org/r/20250822030651.28099-1-chentaotao@didiglobal.com
(cherry picked from commit e296a22)
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>

Author: Taotao Chen

drivers/gpu/drm/i915/gem/i915_gem_shmem.c

@@ -514,6 +514,13 @@ static int __create_shmem(struct drm_i915_private *i915,
 	if (IS_ERR(filp))
 		return PTR_ERR(filp);
 
+	/*
+	 * Prevent -EFBIG by allowing large writes beyond MAX_NON_LFS on shmem
+	 * objects by setting O_LARGEFILE.
+	 */
+	if (force_o_largefile())
+		filp->f_flags |= O_LARGEFILE;
+
 	obj->filp = filp;
 	return 0;
 }