diff options
author | David Herrmann <dh.herrmann@gmail.com> | 2014-08-09 01:25:34 +0400 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-08-09 02:57:31 +0400 |
commit | 87b2d44026e0e315a7401551e95b189ac4b28217 (patch) | |
tree | ae066f8f409be64b9d9ca192d470c0c505b520a9 /tools/testing/selftests/memfd/fuse_mnt.c | |
parent | 4f5ce5e8d7e2da3c714df8a7fa42edb9f992fc52 (diff) | |
download | linux-87b2d44026e0e315a7401551e95b189ac4b28217.tar.xz |
selftests: add memfd/sealing page-pinning tests
Setting SEAL_WRITE is not possible if there're pending GUP users. This
commit adds selftests for memfd+sealing that use FUSE to create pending
page-references. FUSE is very helpful here in that it allows us to delay
direct-IO operations for an arbitrary amount of time. This way, we can
force the kernel to pin pages and then run our normal selftests.
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Ryan Lortie <desrt@desrt.ca>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Daniel Mack <zonque@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'tools/testing/selftests/memfd/fuse_mnt.c')
-rw-r--r-- | tools/testing/selftests/memfd/fuse_mnt.c | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/tools/testing/selftests/memfd/fuse_mnt.c b/tools/testing/selftests/memfd/fuse_mnt.c new file mode 100644 index 000000000000..feacf1280fcd --- /dev/null +++ b/tools/testing/selftests/memfd/fuse_mnt.c @@ -0,0 +1,110 @@ +/* + * 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); +} |