Re: [axboe-block:for-6.5/block] [block] 1ccf164ec8: WARNING:at_mm/gup.c:#try_get_folio

[David Howells <dhowells@xxxxxxxxxx>]

The attached test reproduces the problem on a loop-back mounted file
containing a UDF filesystem.  The key appears to be the consecutive DIOs to
the same page.

David
---
#define __USE_GNU
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <err.h>
# define O_DIRECT      040000

static char buf[256 * 1024] __attribute__((aligned(512)));
static char *filename;

static void cleanup(void)
{
	if (unlink(filename) == -1)
		err(1, "unlink");
}

int main(int argc, char **argv)
{
	size_t page = 4096;
	int fd;

	if (argc != 2) {
		fprintf(stderr, "Format: %s <file>\n", argv[1]);
		exit(2);
	}

	filename = argv[1];

	fd = open(filename, O_RDWR | O_CREAT | O_EXCL | O_DIRECT, 0666);
	if (fd == -1)
		err(1, "%s", filename);

	atexit(cleanup);

	if (pwrite(fd, buf, page, 0) != page)
		err(1, "pwrite/1");

	if (pwrite(fd, buf, page, page) != page)
		err(1, "pwrite/2");

	if (close(fd) == -1)
		err(1, "close");

	return 0;
}