erofs: allow readdir() to be interrupted

In a quick slow device, readdir() may loop for long time in large
directory, let's give a chance to allow it to be interrupted by
userspace.

Signed-off-by: Chao Yu <chao@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250710073619.4083422-1-chao@kernel.org
[ Gao Xiang: move cond_resched() to the end of the while loop. ]
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Author: chaseyu

fs/erofs/dir.c

@@ -58,6 +58,11 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
 		struct erofs_dirent *de;
 		unsigned int nameoff, maxsize;
 
+		if (fatal_signal_pending(current)) {
+			err = -ERESTARTSYS;
+			break;
+		}
+
 		de = erofs_bread(&buf, dbstart, true);
 		if (IS_ERR(de)) {
 			erofs_err(sb, "failed to readdir of logical block %llu of nid %llu",
@@ -88,6 +93,7 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
 			break;
 		ctx->pos = dbstart + maxsize;
 		ofs = 0;
+		cond_resched();
 	}
 	erofs_put_metabuf(&buf);
 	if (EROFS_I(dir)->dot_omitted && ctx->pos == dir->i_size) {