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// SPDX-License-Identifier: GPL-2.0
/*
* memfd test file-system
* This file uses FUSE to create a dummy file-system with only one file /memfd.
* This file is read-only and takes 1s per read.
*
* This file-system is used by the memfd test-cases to force the kernel to pin
* pages during reads(). Due to the 1s delay of this file-system, this is a
* nice way to test race-conditions against get_user_pages() in the kernel.
*
* We use direct_io==1 to force the kernel to use direct-IO for this
* file-system.
*/
#define FUSE_USE_VERSION 26
#include <fuse.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
static const char memfd_content[] = "memfd-example-content";
static const char memfd_path[] = "/memfd";
static int memfd_getattr(const char *path, struct stat *st)
{
memset(st, 0, sizeof(*st));
if (!strcmp(path, "/")) {
st->st_mode = S_IFDIR | 0755;
st->st_nlink = 2;
} else if (!strcmp(path, memfd_path)) {
st->st_mode = S_IFREG | 0444;
st->st_nlink = 1;
st->st_size = strlen(memfd_content);
} else {
return -ENOENT;
}
return 0;
}
static int memfd_readdir(const char *path,
void *buf,
fuse_fill_dir_t filler,
off_t offset,
struct fuse_file_info *fi)
{
if (strcmp(path, "/"))
return -ENOENT;
filler(buf, ".", NULL, 0);
filler(buf, "..", NULL, 0);
filler(buf, memfd_path + 1, NULL, 0);
return 0;
}
static int memfd_open(const char *path, struct fuse_file_info *fi)
{
if (strcmp(path, memfd_path))
return -ENOENT;
if ((fi->flags & 3) != O_RDONLY)
return -EACCES;
/* force direct-IO */
fi->direct_io = 1;
return 0;
}
static int memfd_read(const char *path,
char *buf,
size_t size,
off_t offset,
struct fuse_file_info *fi)
{
size_t len;
if (strcmp(path, memfd_path) != 0)
return -ENOENT;
sleep(1);
len = strlen(memfd_content);
if (offset < len) {
if (offset + size > len)
size = len - offset;
memcpy(buf, memfd_content + offset, size);
} else {
size = 0;
}
return size;
}
static struct fuse_operations memfd_ops = {
.getattr = memfd_getattr,
.readdir = memfd_readdir,
.open = memfd_open,
.read = memfd_read,
};
int main(int argc, char *argv[])
{
return fuse_main(argc, argv, &memfd_ops, NULL);
}
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