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

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at 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 at 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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