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    SubjectRe: [RFC v2][PATCH 1/9] checkpoint-restart: general infrastructure
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    On Wed, 2008-08-20 at 12:25 -0700, Dave Hansen wrote:
    > This patch adds those interfaces, as well as all of the helpers
    > needed to easily manage the file format.
    >
    > The code is roughly broken out as follows:
    >
    > ckpt/sys.c - user/kernel data transfer, as well as setting up of the
    > checkpoint/restart context (a per-checkpoint data
    > structure for housekeeping)
    > ckpt/checkpoint.c - output wrappers and basic checkpoint handling
    > ckpt/restart.c - input wrappers and basic restart handling
    >
    > Patches to add the per-architecture support as well as the actual
    > work to do the memory checkpoint follow in subsequent patches.
    >
    > changes from last version:
    > - Moved over to pr_debug() from CR_PRINTK()
    > - Moved magic number over to linux/magic.h
    >
    > TODO:
    > - Investigate using anon_inodes for the sys_checkpoint() side
    > - Move all the structure declarations to somewhere that we
    > can easily export them to userspace.
    > - Lots of ABI issues to work out.
    >
    > Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
    > ---
    >
    > oren-cr.git-dave/Makefile | 2
    > oren-cr.git-dave/checkpoint/Makefile | 1
    > oren-cr.git-dave/checkpoint/checkpoint.c | 208 +++++++++++++++++++++++++++
    > oren-cr.git-dave/checkpoint/ckpt.h | 71 +++++++++
    > oren-cr.git-dave/checkpoint/ckpt_hdr.h | 69 +++++++++
    > oren-cr.git-dave/checkpoint/restart.c | 190 +++++++++++++++++++++++++
    > oren-cr.git-dave/checkpoint/sys.c | 233 +++++++++++++++++++++++++++++++
    > oren-cr.git-dave/include/linux/magic.h | 2
    > 8 files changed, 775 insertions(+), 1 deletion(-)
    >
    > diff -puN /dev/null checkpoint/checkpoint.c
    > --- /dev/null 2008-04-22 10:49:52.000000000 -0700
    > +++ oren-cr.git-dave/checkpoint/checkpoint.c 2008-08-20 12:12:48.000000000 -0700
    > @@ -0,0 +1,208 @@
    > +/*
    > + * Checkpoint logic and helpers
    > + *
    > + * 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/version.h>
    > +#include <linux/sched.h>
    > +#include <linux/time.h>
    > +#include <linux/fs.h>
    > +#include <linux/file.h>
    > +#include <linux/dcache.h>
    > +#include <linux/magic.h>
    > +#include <linux/mount.h>
    > +#include <asm/ptrace.h>
    > +
    > +#include "ckpt.h"
    > +#include "ckpt_hdr.h"
    > +
    > +/**
    > + * cr_get_fname - return pathname of a given file
    > + * @file: file pointer
    > + * @buf: buffer for pathname
    > + * @n: buffer length (in) and pathname length (out)
    > + *
    > + * if the buffer provivded by the caller is too small, allocate a new
    > + * buffer; caller should call cr_put_pathname() for cleanup
    > + */
    > +char *cr_get_fname(struct path *path, struct path *root, char *buf, int *n)
    > +{
    > + char *fname;
    > +
    > + fname = __d_path(path, root, buf, *n);
    > +
    > + if (IS_ERR(fname) && PTR_ERR(fname) == -ENAMETOOLONG) {
    > + if (!(buf = (char *) __get_free_pages(GFP_KERNEL, 0)))
    > + return ERR_PTR(-ENOMEM);
    > + fname = __d_path(path, root, buf, PAGE_SIZE);
    > + if (IS_ERR(fname))
    > + free_pages((unsigned long) buf, 0);
    > + }
    > + if (!IS_ERR(fname))
    > + *n = (buf + *n - fname);
    > +
    > + return fname;
    > +}
    > +
    > +/**
    > + * cr_put_fname - (possibly) cleanup pathname buffer
    > + * @buf: original buffer that was given to cr_get_pathname()
    > + * @fname: resulting pathname from cr_get_pathname()
    > + * @n: length of original buffer
    > + */
    > +void cr_put_fname(char *buf, char *fname, int n)
    > +{
    > + if (fname && (fname < buf || fname >= buf + n))
    > + free_pages((unsigned long) buf, 0);
    > +}
    > +
    > +/**
    > + * cr_write_obj - write a record described by a cr_hdr
    > + * @ctx: checkpoint context
    > + * @h: record descriptor
    > + * @buf: record buffer
    > + */
    > +int cr_write_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf)
    > +{
    > + int ret;
    > +
    > + if ((ret = cr_kwrite(ctx, h, sizeof(*h))) < 0)
    > + return ret;
    > + return cr_kwrite(ctx, buf, h->len);
    > +}
    > +
    > +/**
    > + * cr_write_str - write a string record
    > + * @ctx: checkpoint context
    > + * @str: string buffer
    > + * @n: string length
    > + */
    > +int cr_write_str(struct cr_ctx *ctx, char *str, int n)
    > +{
    > + struct cr_hdr h;
    > +
    > + h.type = CR_HDR_STR;
    > + h.len = n;
    > + h.id = 0;
    > +
    > + return cr_write_obj(ctx, &h, str);
    > +}
    > +
    > +/* write the checkpoint header */
    > +static int cr_write_hdr(struct cr_ctx *ctx)
    > +{
    > + struct cr_hdr h;
    > + struct cr_hdr_head *hh = ctx->tbuf;
    > + struct timeval ktv;
    > +
    > + h.type = CR_HDR_HEAD;
    > + h.len = sizeof(hh);
    > + h.id = 0;
    > +
    > + do_gettimeofday(&ktv);
    > +
    > + hh->magic = CR_HEADER_MAGIC;
    > + hh->major = (LINUX_VERSION_CODE >> 16) & 0xff;
    > + hh->minor = (LINUX_VERSION_CODE >> 8) & 0xff;
    > + hh->patch = (LINUX_VERSION_CODE) & 0xff;
    > +
    > + hh->version = 1;
    > +
    > + hh->flags = ctx->flags;
    > + hh->time = ktv.tv_sec;
    > +
    > + return cr_write_obj(ctx, &h, hh);
    > +}
    > +
    > +/* write the checkpoint trailer */
    > +static int cr_write_tail(struct cr_ctx *ctx)
    > +{
    > + struct cr_hdr h;
    > + struct cr_hdr_tail *hh = ctx->tbuf;
    > +
    > + h.type = CR_HDR_TAIL;
    > + h.len = sizeof(*hh);
    > + h.id = 0;
    > +
    > + hh->magic = CR_HEADER_MAGIC;
    > + hh->cksum[0] = hh->cksum[1] = 1; /* TBD ... */
    > +
    > + return cr_write_obj(ctx, &h, hh);
    > +}
    > +
    > +/* dump the task_struct of a given task */
    > +static int cr_write_task_struct(struct cr_ctx *ctx, struct task_struct *t)
    > +{
    > + struct cr_hdr h;
    > + struct cr_hdr_task *hh = ctx->tbuf;
    > +
    > + h.type = CR_HDR_TASK;
    > + h.len = sizeof(*hh);
    > + h.id = ctx->pid;
    > +
    > + hh->state = t->state;
    > + hh->exit_state = t->exit_state;
    > + hh->exit_code = t->exit_code;
    > + hh->exit_signal = t->exit_signal;
    > +
    > + hh->pid = t->pid;
    > + hh->tgid = t->tgid;
    > +
    > + hh->utime = t->utime;
    > + hh->stime = t->stime;
    > + hh->utimescaled = t->utimescaled;
    > + hh->stimescaled = t->stimescaled;
    > + hh->gtime = t->gtime;
    > + hh->prev_utime = t->prev_utime;
    > + hh->prev_stime = t->prev_stime;
    > + hh->nvcsw = t->nvcsw;
    > + hh->nivcsw = t->nivcsw;
    > + hh->start_time_sec = t->start_time.tv_sec;
    > + hh->start_time_nsec = t->start_time.tv_nsec;
    > + hh->real_start_time_sec = t->real_start_time.tv_sec;
    > + hh->real_start_time_nsec = t->real_start_time.tv_nsec;
    > + hh->min_flt = t->min_flt;
    > + hh->maj_flt = t->maj_flt;
    > +
    > + hh->task_comm_len = TASK_COMM_LEN;
    > + memcpy(hh->comm, t->comm, TASK_COMM_LEN);
    > +
    > + return cr_write_obj(ctx, &h, hh);
    > +}
    > +
    > +/* dump the entire state of a given task */
    > +static int cr_write_task(struct cr_ctx *ctx, struct task_struct *t)
    > +{
    > + int ret ;
    > +
    > + BUG_ON(t->state == TASK_DEAD);
    > +
    > + ret = cr_write_task_struct(ctx, t);
    > + pr_debug("ret (task_struct) %d\n", ret);
    > +
    > + return ret;
    > +}
    > +
    > +int do_checkpoint(struct cr_ctx *ctx)
    > +{
    > + int ret;
    > +
    > + /* FIX: need to test whether container is checkpointable */
    > +
    > + ret = cr_write_hdr(ctx);
    > + if (!ret)
    > + ret = cr_write_task(ctx, current);
    > + if (!ret)
    > + ret = cr_write_tail(ctx);
    > +
    > + /* on success, return (unique) checkpoint identifier */
    > + if (!ret)
    > + ret = ctx->crid;
    > +
    > + return ret;

    How about conforming to existing kernel style by inverting the ret tests
    and using goto here:

    ret = cr_write_hdr(ctx);
    if (ret)
    goto out;
    ret = cr_write_task(ctx, current);
    if (ret)
    goto out;
    ret = cr_write_tail(ctx);
    if (ret)
    goto out;
    ret = ctx->crid;
    out:
    return ret;

    That means that if we aren't always assigning to ret we won't always
    need to (re)test it. Granted the compiler output is probably the same,
    but I think this is much more readable by reviewers. It may also be
    easier to maintain since you won't have to test ret before adding new
    code here.

    > +}
    > diff -puN /dev/null checkpoint/ckpt.h
    > --- /dev/null 2008-04-22 10:49:52.000000000 -0700
    > +++ oren-cr.git-dave/checkpoint/ckpt.h 2008-08-20 12:12:48.000000000 -0700
    > @@ -0,0 +1,71 @@
    > +#ifndef _CKPT_CKPT_H_
    > +#define _CKPT_CKPT_H_
    > +/*
    > + * Generic container checkpoint-restart
    > + *
    > + * 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/path.h>
    > +#include <linux/fs.h>
    > +
    > +struct cr_pgarr;
    > +
    > +struct cr_ctx {
    > + pid_t pid; /* container identifier */
    > + int crid; /* unique checkpoint id */
    > +
    > + unsigned long flags;
    > + unsigned long oflags; /* restart: old flags */
    > +
    > + struct file *file;
    > + int total; /* total read/written */
    > +
    > + void *tbuf; /* temp: to avoid many alloc/dealloc */
    > + void *hbuf; /* header: to avoid many alloc/dealloc */
    > + int hpos;
    > +
    > + struct cr_pgarr *pgarr;
    > + struct cr_pgarr *pgcur;
    > +
    > + struct path *vfsroot; /* container root */
    > +};
    > +
    > +/* cr_ctx: flags */
    > +#define CR_CTX_CKPT 0x1
    > +#define CR_CTX_RSTR 0x2
    > +
    > +/* allocation defaults */
    > +#define CR_ORDER_TBUF 1
    > +#define CR_ORDER_HBUF 1
    > +
    > +#define CR_TBUF_TOTAL ((PAGE_SIZE << CR_ORDER_TBUF) / sizeof(void *))
    > +#define CR_HBUF_TOTAL ((PAGE_SIZE << CR_ORDER_HBUF) / sizeof(void *))
    > +
    > +extern void cr_put_fname(char *buf, char *fname, int n);
    > +extern char *cr_get_fname(struct path *path, struct path *root, char *buf, int *n);
    > +
    > +extern int cr_uwrite(struct cr_ctx *ctx, void *buf, int count);
    > +extern int cr_kwrite(struct cr_ctx *ctx, void *buf, int count);
    > +extern int cr_uread(struct cr_ctx *ctx, void *buf, int count);
    > +extern int cr_kread(struct cr_ctx *ctx, void *buf, int count);
    > +
    > +struct cr_hdr;
    > +
    > +extern int cr_write_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf);
    > +extern int cr_write_str(struct cr_ctx *ctx, char *str, int n);
    > +extern int cr_write_mm(struct cr_ctx *ctx, struct task_struct *t);
    > +
    > +extern int cr_read_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf, int n);
    > +extern int cr_read_obj_type(struct cr_ctx *ctx, void *buf, int n, int type);
    > +extern int cr_read_str(struct cr_ctx *ctx, void *str, int n);
    > +extern int cr_read_mm(struct cr_ctx *ctx);
    > +
    > +extern int do_checkpoint(struct cr_ctx *ctx);
    > +extern int do_restart(struct cr_ctx *ctx);
    > +
    > +#endif /* _CKPT_CKPT_H_ */
    > diff -puN /dev/null checkpoint/ckpt_hdr.h
    > --- /dev/null 2008-04-22 10:49:52.000000000 -0700
    > +++ oren-cr.git-dave/checkpoint/ckpt_hdr.h 2008-08-20 12:12:48.000000000 -0700
    > @@ -0,0 +1,69 @@
    > +/*
    > + * Generic container checkpoint-restart
    > + *
    > + * 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/types.h>
    > +
    > +struct cr_hdr {
    > + __s16 type;
    > + __s16 len;
    > + __u32 id;
    > +};
    > +
    > +enum {
    > + CR_HDR_HEAD = 1,
    > + CR_HDR_STR,
    > +
    > + CR_HDR_TASK = 101,
    > + CR_HDR_THREAD,
    > + CR_HDR_CPU,
    > +
    > + CR_HDR_MM = 201,
    > + CR_HDR_VMA,
    > + CR_HDR_MM_CONTEXT,
    > +
    > + CR_HDR_TAIL = 5001
    > +};
    > +
    > +struct cr_hdr_head {
    > + __u32 magic;
    > + __u16 major;
    > + __u16 minor;
    > + __u16 patch;
    > + __u16 version;
    > + __u32 flags; /* checkpoint options */
    > + __u64 time; /* when checkpoint taken */
    > +};
    > +
    > +struct cr_hdr_tail {
    > + __u32 magic;
    > + __u32 cksum[2];
    > +};
    > +
    > +struct cr_hdr_task {
    > + __u64 state;
    > + __u32 exit_state;
    > + __u32 exit_code, exit_signal;
    > +
    > + __u16 pid;
    > + __u16 tgid;
    > +
    > + __u64 utime, stime, utimescaled, stimescaled;
    > + __u64 gtime;
    > + __u64 prev_utime, prev_stime;
    > + __u64 nvcsw, nivcsw;
    > + __u64 start_time_sec, start_time_nsec;
    > + __u64 real_start_time_sec, real_start_time_nsec;
    > + __u64 min_flt, maj_flt;
    > +
    > + __s16 task_comm_len;
    > + char comm[TASK_COMM_LEN];
    > +};
    > +
    > +
    > diff -puN /dev/null checkpoint/Makefile
    > --- /dev/null 2008-04-22 10:49:52.000000000 -0700
    > +++ oren-cr.git-dave/checkpoint/Makefile 2008-08-20 12:12:48.000000000 -0700
    > @@ -0,0 +1 @@
    > +obj-y += sys.o checkpoint.o restart.o
    > diff -puN /dev/null checkpoint/restart.c
    > --- /dev/null 2008-04-22 10:49:52.000000000 -0700
    > +++ oren-cr.git-dave/checkpoint/restart.c 2008-08-20 12:12:48.000000000 -0700
    > @@ -0,0 +1,190 @@
    > +/*
    > + * Restart logic and helpers
    > + *
    > + * 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.
    > + */
    > +
    > +/*
    > + * During restart the code reads in data from the chekcpoint image into a
    > + * temporary buffer (ctx->hbuf). Because operations can be nested, one
    > + * should call cr_hbuf_get() to reserve space in the buffer, and then
    > + * cr_hbuf_put() when it no longer needs that space
    > + */
    > +
    > +#include <linux/version.h>
    > +#include <linux/magic.h>
    > +#include <linux/sched.h>
    > +#include <linux/file.h>
    > +
    > +#include "ckpt.h"
    > +#include "ckpt_hdr.h"
    > +
    > +/**
    > + * cr_hbuf_get - reserve space on the hbuf
    > + * @ctx: checkpoint context
    > + * @n: number of bytes to reserve
    > + */
    > +void *cr_hbuf_get(struct cr_ctx *ctx, int n)
    > +{
    > + void *ptr;
    > +
    > + BUG_ON(ctx->hpos + n > CR_HBUF_TOTAL);
    > + ptr = (void *) (((char *) ctx->hbuf) + ctx->hpos);
    > + ctx->hpos += n;
    > + return ptr;
    > +}
    > +
    > +/**
    > + * cr_hbuf_put - unreserve space on the hbuf
    > + * @ctx: checkpoint context
    > + * @n: number of bytes to reserve
    > + */
    > +void cr_hbuf_put(struct cr_ctx *ctx, int n)
    > +{
    > + BUG_ON(ctx->hpos < n);
    > + ctx->hpos -= n;
    > +}
    > +
    > +/**
    > + * cr_read_obj - read a whole record (cr_hdr followed by payload)
    > + * @ctx: checkpoint context
    > + * @h: record descriptor
    > + * @buf: record buffer
    > + * @n: available buffer size
    > + */
    > +int cr_read_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf, int n)
    > +{
    > + int ret;
    > +
    > + ret = cr_kread(ctx, h, sizeof(*h));
    > + if (ret < 0)
    > + return ret;
    > +
    > + pr_debug("type %d len %d id %d (%d)\n", h->type, h->len, h->id, n);
    > + if (h->len < 0 || h->len > n)
    > + return -EINVAL;
    > +
    > + return cr_kread(ctx, buf, h->len);
    > +}
    > +
    > +/**
    > + * cr_read_obj_type - read a whole record of expected type
    > + * @ctx: checkpoint context
    > + * @buf: record buffer
    > + * @n: available buffer size
    > + * @type: expected record type
    > + */
    > +int cr_read_obj_type(struct cr_ctx *ctx, void *buf, int n, int type)
    > +{
    > + struct cr_hdr h;
    > + int ret;
    > +
    > + ret = cr_read_obj(ctx, &h, buf, n);
    > + if (!ret)
    > + ret = (h.type == type ? h.id : -EINVAL);
    > + return ret;
    > +}
    > +
    > +/**
    > + * cr_read_str - read a string record
    > + * @ctx: checkpoint context
    > + * @str: string buffer
    > + * @n: string length
    > + */
    > +int cr_read_str(struct cr_ctx *ctx, void *str, int n)
    > +{
    > + return cr_read_obj_type(ctx, str, n, CR_HDR_STR);
    > +}
    > +
    > +/* read the checkpoint header */
    > +static int cr_read_hdr(struct cr_ctx *ctx)
    > +{
    > + struct cr_hdr_head *hh = cr_hbuf_get(ctx, sizeof(*hh));
    > + int ret;
    > +
    > + ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_HEAD);
    > + if (ret < 0)
    > + return ret;
    > +
    > + if (hh->magic != CR_HEADER_MAGIC || hh->version != 1 ||
    > + hh->major != ((LINUX_VERSION_CODE >> 16) & 0xff) ||
    > + hh->minor != ((LINUX_VERSION_CODE >> 8) & 0xff) ||
    > + hh->patch != ((LINUX_VERSION_CODE) & 0xff))
    > + return -EINVAL;
    > +
    > + if (hh->flags & ~CR_CTX_CKPT)
    > + return -EINVAL;
    > +
    > + ctx->oflags = hh->flags;
    > +
    > + cr_hbuf_put(ctx, sizeof(*hh));
    > + return 0;
    > +}
    > +
    > +/* read the checkpoint trailer */
    > +static int cr_read_tail(struct cr_ctx *ctx)
    > +{
    > + struct cr_hdr_tail *hh = cr_hbuf_get(ctx, sizeof(*hh));
    > + int ret;
    > +
    > + ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_TAIL);
    > + if (ret < 0)
    > + return ret;
    > +
    > + if (hh->magic != CR_HEADER_MAGIC ||
    > + hh->cksum[0] != 1 || hh->cksum[1] != 1)
    > + return -EINVAL;
    > +
    > + cr_hbuf_put(ctx, sizeof(*hh));
    > + return 0;
    > +}
    > +
    > +/* read the task_struct into the current task */
    > +static int cr_read_task_struct(struct cr_ctx *ctx)
    > +{
    > + struct cr_hdr_task *hh = cr_hbuf_get(ctx, sizeof(*hh));
    > + struct task_struct *t = current;
    > + int ret;
    > +
    > + ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_TASK);
    > + if (ret < 0)
    > + return ret;
    > +
    > + /* for now, only restore t->comm */
    > + if (hh->task_comm_len < 0 || hh->task_comm_len > TASK_COMM_LEN)
    > + return -EINVAL;
    > +
    > + memset(t->comm, 0, TASK_COMM_LEN);
    > + memcpy(t->comm, hh->comm, hh->task_comm_len);
    > +
    > + cr_hbuf_put(ctx, sizeof(*hh));
    > + return 0;
    > +}
    > +
    > +/* read the entire state of the current task */
    > +static int cr_read_task(struct cr_ctx *ctx)
    > +{
    > + int ret;
    > +
    > + ret = cr_read_task_struct(ctx);
    > + pr_debug("ret (task_struct) %d\n", ret);
    > +
    > + return ret;
    > +}
    > +
    > +int do_restart(struct cr_ctx *ctx)
    > +{
    > + int ret;
    > +
    > + ret = cr_read_hdr(ctx);
    > + if (!ret)
    > + ret = cr_read_task(ctx);
    > + if (!ret)
    > + ret = cr_read_tail(ctx);
    same comment

    > +
    > + return ret;
    > +}
    > diff -puN /dev/null checkpoint/sys.c
    > --- /dev/null 2008-04-22 10:49:52.000000000 -0700
    > +++ oren-cr.git-dave/checkpoint/sys.c 2008-08-20 12:12:48.000000000 -0700
    > @@ -0,0 +1,233 @@
    > +/*
    > + * Generic container checkpoint-restart
    > + *
    > + * 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/sched.h>
    > +#include <linux/fs.h>
    > +#include <linux/file.h>
    > +#include <linux/uaccess.h>
    > +#include <linux/capability.h>
    > +
    > +#include "ckpt.h"
    > +
    > +/*
    > + * helpers to write/read to/from the image file descriptor
    > + *
    > + * cr_uwrite() - write a user-space buffer to the checkpoint image
    > + * cr_kwrite() - write a kernel-space buffer to the checkpoint image
    > + * cr_uread() - read from the checkpoint image to a user-space buffer
    > + * cr_kread() - read from the checkpoint image to a kernel-space buffer
    > + *
    > + */
    > +
    > +/* (temporarily added file_pos_read() and file_pos_write() because they
    > + * are static in fs/read_write.c... should cleanup and remove later) */
    > +static inline loff_t file_pos_read(struct file *file)
    > +{
    > + return file->f_pos;
    > +}
    > +
    > +static inline void file_pos_write(struct file *file, loff_t pos)
    > +{
    > + file->f_pos = pos;
    > +}
    > +
    > +int cr_uwrite(struct cr_ctx *ctx, void *buf, int count)
    > +{
    > + struct file *file = ctx->file;
    > + ssize_t nwrite;
    > + int nleft;
    > +
    > + for (nleft = count; nleft; nleft -= nwrite) {
    > + loff_t pos = file_pos_read(file);
    > + nwrite = vfs_write(file, (char __user *) buf, nleft, &pos);
    > + file_pos_write(file, pos);
    > + if (unlikely(nwrite <= 0)) /* zero tolerance */
    > + return (nwrite ? : -EIO);
    > + buf += nwrite;
    > + }
    > +
    > + ctx->total += count;
    > + return 0;
    > +}
    > +
    > +int cr_kwrite(struct cr_ctx *ctx, void *buf, int count)
    > +{
    > + mm_segment_t oldfs;
    > + int ret;
    > +
    > + oldfs = get_fs();
    > + set_fs(KERNEL_DS);
    > + ret = cr_uwrite(ctx, buf, count);
    > + set_fs(oldfs);
    > +
    > + return ret;
    > +}
    > +
    > +int cr_uread(struct cr_ctx *ctx, void *buf, int count)
    > +{
    > + struct file *file = ctx->file;
    > + ssize_t nread;
    > + int nleft;
    > +
    > + for (nleft = count; nleft; nleft -= nread) {
    > + loff_t pos = file_pos_read(file);
    > + nread = vfs_read(file, (char __user *) buf, nleft, &pos);
    > + file_pos_write(file, pos);
    > + if (unlikely(nread <= 0)) /* zero tolerance */
    > + return (nread ? : -EIO);
    > + buf += nread;
    > + }
    > +
    > + ctx->total += count;
    > + return 0;
    > +}
    > +
    > +int cr_kread(struct cr_ctx *ctx, void *buf, int count)
    > +{
    > + mm_segment_t oldfs;
    > + int ret;
    > +
    > + oldfs = get_fs();
    > + set_fs(KERNEL_DS);
    > + ret = cr_uread(ctx, buf, count);
    > + set_fs(oldfs);
    > +
    > + return ret;
    > +}
    > +
    > +
    > +/*
    > + * helpers to manage CR contexts: allocated for each checkpoint and/or
    > + * restart operation, and persists until the operation is completed.
    > + */
    > +
    > +static atomic_t cr_ctx_count; /* unique checkpoint identifier */
    > +
    > +void cr_ctx_free(struct cr_ctx *ctx)
    > +{
    > +
    > + if (ctx->file)
    > + fput(ctx->file);
    > + if (ctx->vfsroot)
    > + path_put(ctx->vfsroot);
    > +
    > + free_pages((unsigned long) ctx->tbuf, CR_ORDER_TBUF);
    > + free_pages((unsigned long) ctx->hbuf, CR_ORDER_HBUF);
    > +
    > + kfree(ctx);
    > +}
    > +
    > +struct cr_ctx *cr_ctx_alloc(pid_t pid, struct file *file, unsigned long flags)
    > +{
    > + struct cr_ctx *ctx;
    > +
    > + ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
    > + if (!ctx)
    > + return NULL;
    > +
    > + ctx->tbuf = (void *) __get_free_pages(GFP_KERNEL, CR_ORDER_TBUF);
    > + ctx->hbuf = (void *) __get_free_pages(GFP_KERNEL, CR_ORDER_HBUF);
    > + if (!ctx->tbuf || !ctx->hbuf)
    > + goto nomem;
    > +
    > + ctx->pid = pid;
    > + ctx->flags = flags;
    > +
    > + ctx->file = file;
    > + get_file(file);
    > +
    > + /* assume checkpointer is in container's root vfs */
    > + ctx->vfsroot = &current->fs->root;
    > + path_get(ctx->vfsroot);
    > +
    > + ctx->crid = atomic_inc_return(&cr_ctx_count);
    > +
    > + return ctx;
    > +
    > + nomem:
    > + cr_ctx_free(ctx);
    > + return NULL;
    > +}
    > +
    > +/**
    > + * sys_checkpoint - checkpoint a container
    > + * @pid: pid of the container init(1) process
    > + * @fd: file to which dump the checkpoint image
    > + * @flags: checkpoint operation flags
    > + */
    > +asmlinkage long sys_checkpoint(pid_t pid, int fd, unsigned long flags)
    > +{
    > + struct cr_ctx *ctx;
    > + struct file *file;
    > + int fput_needed;
    > + int ret;
    > +
    > + if (!capable(CAP_SYS_ADMIN))
    > + return -EPERM;
    > +
    > + file = fget_light(fd, &fput_needed);
    > + if (!file)
    > + return -EBADF;
    > +
    > + /* no flags for now */
    > + if (flags)
    > + return -EINVAL;
    > +
    > + ctx = cr_ctx_alloc(pid, file, flags | CR_CTX_CKPT);
    > + if (!ctx) {
    > + fput_light(file, fput_needed);
    > + return -ENOMEM;
    > + }
    > +
    > + ret = do_checkpoint(ctx);
    > +
    > + cr_ctx_free(ctx);
    > + fput_light(file, fput_needed);
    > + pr_debug("ckpt retval = %d\n", ret);
    > + return ret;
    > +}
    > +
    > +/**
    > + * sys_restart - restart a container
    > + * @crid: checkpoint image identifier
    > + * @fd: file from which read the checkpoint image
    > + * @flags: restart operation flags
    > + */
    > +asmlinkage long sys_restart(int crid, int fd, unsigned long flags)
    > +{
    > + struct cr_ctx *ctx;
    > + struct file *file;
    > + int fput_needed;
    > + int ret;
    > +
    > + if (!capable(CAP_SYS_ADMIN))
    > + return -EPERM;
    > +
    > + file = fget_light(fd, &fput_needed);
    > + if (!file)
    > + return -EBADF;
    > +
    > + /* no flags for now */
    > + if (flags)
    > + return -EINVAL;
    > +
    > + ctx = cr_ctx_alloc(crid, file, flags | CR_CTX_RSTR);
    > + if (!ctx) {
    > + fput_light(file, fput_needed);
    > + return -ENOMEM;
    > + }
    > +
    > + ret = do_restart(ctx);
    > +
    > + cr_ctx_free(ctx);
    > + fput_light(file, fput_needed);
    > + pr_debug("restart retval = %d\n", ret);
    > + return ret;
    > +}
    > diff -puN include/linux/magic.h~0001-checkpoint-restart-general-infrastructure include/linux/magic.h
    > --- oren-cr.git/include/linux/magic.h~0001-checkpoint-restart-general-infrastructure 2008-08-20 12:12:48.000000000 -0700
    > +++ oren-cr.git-dave/include/linux/magic.h 2008-08-20 12:12:48.000000000 -0700
    > @@ -42,4 +42,6 @@
    > #define FUTEXFS_SUPER_MAGIC 0xBAD1DEA
    > #define INOTIFYFS_SUPER_MAGIC 0x2BAD1DEA
    >
    > +#define CR_HEADER_MAGIC 0x002d2a00
    > +
    > #endif /* __LINUX_MAGIC_H__ */
    > diff -puN Makefile~0001-checkpoint-restart-general-infrastructure Makefile
    > --- oren-cr.git/Makefile~0001-checkpoint-restart-general-infrastructure 2008-08-20 12:12:48.000000000 -0700
    > +++ oren-cr.git-dave/Makefile 2008-08-20 12:12:48.000000000 -0700
    > @@ -619,7 +619,7 @@ export mod_strip_cmd
    >
    >
    > ifeq ($(KBUILD_EXTMOD),)
    > -core-y += kernel/ mm/ fs/ ipc/ security/ crypto/ block/
    > +core-y += kernel/ mm/ fs/ ipc/ security/ crypto/ block/ checkpoint/
    >
    > vmlinux-dirs := $(patsubst %/,%,$(filter %/, $(init-y) $(init-m) \
    > $(core-y) $(core-m) $(drivers-y) $(drivers-m) \
    > _
    > _______________________________________________
    > Containers mailing list
    > Containers@lists.linux-foundation.org
    > https://lists.linux-foundation.org/mailman/listinfo/containers



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