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    Subject[RFC v5][PATCH 9/9] Restore open file descriprtors
    Date
    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));
    + 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));
    + 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));
    + 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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