Re: [RFC v5][PATCH 9/9] Restore open file descriprtors

Serge E. Hallyn
2008-09-16T23:09:03Z

Quoting Oren Laadan (orenl@cs.columbia.edu):
> Restore open file descriptors: for each FD read 'struct cr_hdr_fd_ent'
> and lookup objref in the hash table; if not found (first occurence), read
> in 'struct cr_hdr_fd_data', create a new FD and register in the hash.
> Otherwise attach the file pointer from the hash as an FD.
>
> This patch only handles basic FDs - regular files, directories and also
> symbolic links.
>
> Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
> ---
> checkpoint/Makefile | 2 +-
> checkpoint/restart.c | 4 +
> checkpoint/rstr_file.c | 202 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/checkpoint.h | 1 +
> 4 files changed, 208 insertions(+), 1 deletions(-)
> create mode 100644 checkpoint/rstr_file.c
>
> diff --git a/checkpoint/Makefile b/checkpoint/Makefile
> index 7496695..88bbc10 100644
> --- a/checkpoint/Makefile
> +++ b/checkpoint/Makefile
> @@ -3,4 +3,4 @@
> #
>
> obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o objhash.o \
> - ckpt_mem.o rstr_mem.o ckpt_file.o
> + ckpt_mem.o rstr_mem.o ckpt_file.o rstr_file.o
> diff --git a/checkpoint/restart.c b/checkpoint/restart.c
> index a0d5e60..956e274 100644
> --- a/checkpoint/restart.c
> +++ b/checkpoint/restart.c
> @@ -212,6 +212,10 @@ static int cr_read_task(struct cr_ctx *ctx)
> cr_debug("memory: ret %d\n", ret);
> if (ret < 0)
> goto out;
> + ret = cr_read_files(ctx);
> + cr_debug("files: ret %d\n", ret);
> + if (ret < 0)
> + goto out;
> ret = cr_read_thread(ctx);
> cr_debug("thread: ret %d\n", ret);
> if (ret < 0)
> diff --git a/checkpoint/rstr_file.c b/checkpoint/rstr_file.c
> new file mode 100644
> index 0000000..780c0fc
> --- /dev/null
> +++ b/checkpoint/rstr_file.c
> @@ -0,0 +1,202 @@
> +/*
> + * Checkpoint file descriptors
> + *
> + * Copyright (C) 2008 Oren Laadan
> + *
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License. See the file COPYING in the main directory of the Linux
> + * distribution for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/sched.h>
> +#include <linux/fs.h>
> +#include <linux/file.h>
> +#include <linux/fdtable.h>
> +#include <linux/fsnotify.h>
> +#include <linux/syscalls.h>
> +#include <linux/checkpoint.h>
> +#include <linux/checkpoint_hdr.h>
> +
> +#include "checkpoint_file.h"
> +
> +static int cr_close_all_fds(struct files_struct *files)
> +{
> + int *fdtable;
> + int nfds;
> +
> + nfds = cr_scan_fds(files, &fdtable);
> + if (nfds < 0)
> + return nfds;
> + while (nfds--)
> + sys_close(fdtable[nfds]);
> + kfree(fdtable);
> + return 0;
> +}
> +
> +/**
> + * cr_attach_file - attach a lonely file ptr to a file descriptor
> + * @file: lonely file pointer
> + */
> +static int cr_attach_file(struct file *file)
> +{
> + int fd = get_unused_fd_flags(0);
> +
> + if (fd >= 0) {
> + fsnotify_open(file->f_path.dentry);
> + fd_install(fd, file);
> + }
> + return fd;
> +}
> +
> +#define CR_SETFL_MASK (O_APPEND|O_NONBLOCK|O_NDELAY|FASYNC|O_DIRECT|O_NOATIME)
> +
> +/* cr_read_fd_data - restore the state of a given file pointer */
> +static int
> +cr_read_fd_data(struct cr_ctx *ctx, struct files_struct *files, int parent)
> +{
> + struct cr_hdr_fd_data *hh = cr_hbuf_get(ctx, sizeof(*hh));

You're leaking hh in a whole slew of error paths.

> + struct file *file;
> + int fd, rparent, ret;
> +
> + rparent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_FD_DATA);
> + cr_debug("rparent %d parent %d flags %#x mode %#x how %d\n",
> + rparent, parent, hh->f_flags, hh->f_mode, hh->fd_type);
> + if (rparent < 0)
> + return rparent;
> + if (rparent != parent)
> + return -EINVAL;
> + /* FIX: more sanity checks on f_flags, f_mode etc */
> +
> + switch (hh->fd_type) {
> + case CR_FD_FILE:
> + case CR_FD_DIR:
> + case CR_FD_LINK:
> + file = cr_read_open_fname(ctx, hh->f_flags, hh->f_mode);
> + break;
> + default:
> + file = ERR_PTR(-EINVAL);
> + break;
> + }
> +
> + if (IS_ERR(file))
> + return PTR_ERR(file);
> +
> + /* FIX: need to restore uid, gid, owner etc */
> +
> + fd = cr_attach_file(file); /* no need to cleanup 'file' below */
> + if (fd < 0) {
> + filp_close(file, NULL);
> + return fd;
> + }
> +
> + /* register new <objref, file> tuple in hash table */
> + ret = cr_obj_add_ref(ctx, (void *) file, parent, CR_OBJ_FILE, 0);
> + if (ret < 0)
> + goto out;
> + ret = sys_fcntl(fd, F_SETFL, hh->f_flags & CR_SETFL_MASK);
> + if (ret < 0)
> + goto out;
> + ret = vfs_llseek(file, hh->f_pos, SEEK_SET);
> + if (ret == -ESPIPE) /* ignore error on non-seekable files */
> + ret = 0;
> +
> + out:
> + cr_hbuf_put(ctx, sizeof(*hh));
> + return ret < 0 ? ret : fd;
> +}
> +
> +/**
> + * cr_read_fd_ent - restore the state of a given file descriptor
> + * @ctx: checkpoint context
> + * @files: files_struct pointer
> + * @parent: parent objref
> + *
> + * Restores the state of a file descriptor; looks up the objref (in the
> + * header) in the hash table, and if found picks the matching file and
> + * use it; otherwise calls cr_read_fd_data to restore the file too.
> + */
> +static int
> +cr_read_fd_ent(struct cr_ctx *ctx, struct files_struct *files, int parent)
> +{
> + struct cr_hdr_fd_ent *hh = cr_hbuf_get(ctx, sizeof(*hh));

Again.

> + struct file *file;
> + int newfd, rparent;
> +
> + rparent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_FD_ENT);
> + cr_debug("rparent %d parent %d ref %d\n", rparent, parent, hh->objref);
> + if (rparent < 0)
> + return rparent;
> + if (rparent != parent)
> + return -EINVAL;
> + cr_debug("fd %d coe %d\n", hh->fd, hh->close_on_exec);
> + if (hh->objref <= 0)
> + return -EINVAL;
> +
> + file = cr_obj_get_by_ref(ctx, hh->objref, CR_OBJ_FILE);
> + if (IS_ERR(file))
> + return PTR_ERR(file);
> +
> + if (file) {
> + newfd = cr_attach_file(file);
> + if (newfd < 0)
> + return newfd;
> + get_file(file);
> + } else {
> + /* create new file pointer (and register in hash table) */
> + newfd = cr_read_fd_data(ctx, files, hh->objref);
> + if (newfd < 0)
> + return newfd;
> + }
> +
> + cr_debug("newfd got %d wanted %d\n", newfd, hh->fd);
> +
> + /* if newfd isn't desired fd then reposition it */
> + if (newfd != hh->fd) {
> + int ret = sys_dup2(newfd, hh->fd);
> + if (ret < 0)
> + return ret;
> + sys_close(newfd);
> + }
> +
> + if (hh->close_on_exec)
> + set_close_on_exec(hh->fd, 1);
> +
> + cr_hbuf_put(ctx, sizeof(*hh));
> + return 0;
> +}
> +
> +int cr_read_files(struct cr_ctx *ctx)
> +{
> + struct cr_hdr_files *hh = cr_hbuf_get(ctx, sizeof(*hh));

Again...

> + struct files_struct *files = current->files;
> + int i, parent, ret;
> +
> + parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_FILES);
> + if (parent < 0)
> + return parent;
> +#if 0 /* activate when containers are used */
> + if (parent != task_pid_vnr(current))
> + return -EINVAL;
> +#endif
> + cr_debug("objref %d nfds %d\n", hh->objref, hh->nfds);
> + if (hh->objref < 0 || hh->nfds < 0)
> + return -EINVAL;
> +
> + if (hh->nfds > sysctl_nr_open)
> + return -EMFILE;
> +
> + /* point of no return -- close all file descriptors */
> + ret = cr_close_all_fds(files);
> + if (ret < 0)
> + return ret;
> +
> + for (i = 0; i < hh->nfds; i++) {
> + ret = cr_read_fd_ent(ctx, files, hh->objref);
> + if (ret < 0)
> + break;
> + }
> +
> + cr_hbuf_put(ctx, sizeof(*hh));
> + return ret;
> +}
> diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
> index a202c54..fd3baac 100644
> --- a/include/linux/checkpoint.h
> +++ b/include/linux/checkpoint.h
> @@ -89,6 +89,7 @@ extern int cr_write_files(struct cr_ctx *ctx, struct task_struct *t);
>
> extern int do_restart(struct cr_ctx *ctx);
> extern int cr_read_mm(struct cr_ctx *ctx);
> +extern int cr_read_files(struct cr_ctx *ctx);
>
> #define cr_debug(fmt, args...) \
> pr_debug("[CR:%s] " fmt, __func__, ## args)
> --
> 1.5.4.3
>
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