[Devel] [RFC v14-rc2][PATCH 12/29] Restore open file descriptors
Oren Laadan
orenl at cs.columbia.edu
Mon Mar 30 22:28:52 PDT 2009
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.
Changelog[v14]:
- Revert change to pr_debug(), back to cr_debug()
- Rename: cr_read_files() => cr_read_fd_table()
- Rename: cr_read_fd_data() => cr_read_file()
- Discard field 'hh->parent'
- Check whether calls to cr_hbuf_get() fail
Changelog[v12]:
- Replace obsolete cr_debug() with pr_debug()
Changelog[v6]:
- Balance all calls to cr_hbuf_get() with matching cr_hbuf_put()
(even though it's not really needed)
Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>
Acked-by: Serge Hallyn <serue at us.ibm.com>
Signed-off-by: Dave Hansen <dave at linux.vnet.ibm.com>
---
checkpoint/Makefile | 2 +-
checkpoint/restart.c | 4 +
checkpoint/rstr_file.c | 236 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/checkpoint.h | 1 +
4 files changed, 242 insertions(+), 1 deletions(-)
create mode 100644 checkpoint/rstr_file.c
diff --git a/checkpoint/Makefile b/checkpoint/Makefile
index 1d92ed2..607d864 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile
@@ -3,4 +3,4 @@
#
obj-$(CONFIG_CHECKPOINT) += 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 665894f..da239fd 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -286,6 +286,10 @@ static int cr_read_task(struct cr_ctx *ctx)
cr_debug("memory: ret %d\n", ret);
if (ret < 0)
goto out;
+ ret = cr_read_fd_table(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..1031915
--- /dev/null
+++ b/checkpoint/rstr_file.c
@@ -0,0 +1,236 @@
+/*
+ * Checkpoint file descriptors
+ *
+ * Copyright (C) 2008-2009 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;
+}
+
+/**
+ * cr_attach_get_file - attach (and get) lonely file ptr to a file descriptor
+ * @file: lonely file pointer
+ */
+static int cr_attach_get_file(struct file *file)
+{
+ int fd = get_unused_fd_flags(0);
+
+ if (fd >= 0) {
+ fsnotify_open(file->f_path.dentry);
+ get_file(file);
+ fd_install(fd, file);
+ }
+ return fd;
+}
+
+#define CR_SETFL_MASK (O_APPEND|O_NONBLOCK|O_NDELAY|FASYNC|O_DIRECT|O_NOATIME)
+
+/* cr_read_file - restore the state of a given file pointer */
+static int cr_read_file(struct cr_ctx *ctx, int objref)
+{
+ struct cr_hdr_file *hh;
+ struct file *file;
+ int fd = 0; /* pacify gcc warning */
+ int ret;
+
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ if (!hh)
+ return -ENOMEM;
+
+ ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_FILE);
+ cr_debug("flags %#x mode %#x how %d\n",
+ hh->f_flags, hh->f_mode, hh->fd_type);
+ if (ret < 0)
+ goto out;
+
+ ret = -EINVAL;
+
+ /* FIX: more sanity checks on f_flags, f_mode etc */
+
+ switch (hh->fd_type) {
+ case CR_FD_GENERIC:
+ file = cr_read_open_fname(ctx, hh->f_flags, hh->f_mode);
+ break;
+ default:
+ goto out;
+ }
+
+ if (IS_ERR(file)) {
+ ret = PTR_ERR(file);
+ goto out;
+ }
+
+ /* FIX: need to restore uid, gid, owner etc */
+
+ /* adding <objref,file> to the hash will keep a reference to it */
+ ret = cr_obj_add_ref(ctx, file, objref, CR_OBJ_FILE, 0);
+ if (ret < 0) {
+ filp_close(file, NULL);
+ goto out;
+ }
+
+ fd = cr_attach_file(file); /* no need to cleanup 'file' below */
+ if (fd < 0) {
+ ret = fd;
+ filp_close(file, NULL);
+ 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;
+
+ 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
+ *
+ * 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_file to restore the file too.
+ */
+static int cr_read_fd_ent(struct cr_ctx *ctx)
+{
+ struct cr_hdr_fd_ent *hh;
+ struct file *file;
+ int newfd, ret;
+
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ if (!hh)
+ return -ENOMEM;
+
+ ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_FD_ENT);
+ if (ret < 0)
+ goto out;
+
+ cr_debug("ref %d fd %d c.o.e %d\n",
+ hh->objref, hh->fd, hh->close_on_exec);
+
+ ret = -EINVAL;
+ if (hh->objref <= 0 || hh->fd < 0)
+ goto out;
+
+ file = cr_obj_get_by_ref(ctx, hh->objref, CR_OBJ_FILE);
+ if (IS_ERR(file)) {
+ ret = PTR_ERR(file);
+ goto out;
+ }
+
+ if (file) {
+ /* reuse file descriptor found in the hash table */
+ newfd = cr_attach_get_file(file);
+ } else {
+ /* create new file pointer (and register in hash table) */
+ newfd = cr_read_file(ctx, hh->objref);
+ }
+
+ if (newfd < 0) {
+ ret = newfd;
+ goto out;
+ }
+
+ cr_debug("newfd got %d wanted %d\n", newfd, hh->fd);
+
+ /* if newfd isn't desired fd then reposition it */
+ if (newfd != hh->fd) {
+ ret = sys_dup2(newfd, hh->fd);
+ if (ret < 0)
+ goto out;
+ sys_close(newfd);
+ }
+
+ if (hh->close_on_exec)
+ set_close_on_exec(hh->fd, 1);
+
+ ret = 0;
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
+
+int cr_read_fd_table(struct cr_ctx *ctx)
+{
+ struct cr_hdr_fd_table *hh;
+ int i, ret;
+
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ if (!hh)
+ return -ENOMEM;
+
+ ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_FD_TABLE);
+ if (ret < 0)
+ goto out;
+
+ cr_debug("objref %d nfds %d\n", hh->objref, hh->nfds);
+
+ if (hh->nfds < 0 || hh->nfds > sysctl_nr_open) {
+ ret = -EMFILE;
+ goto out;
+ }
+
+ /* point of no return -- close all file descriptors */
+ ret = cr_close_all_fds(current->files);
+ if (ret < 0)
+ goto out;
+
+ for (i = 0; i < hh->nfds; i++) {
+ ret = cr_read_fd_ent(ctx);
+ if (ret < 0)
+ break;
+ }
+
+ ret = 0;
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 9489ea5..ad4322d 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -89,6 +89,7 @@ extern int cr_write_fd_table(struct cr_ctx *ctx, struct task_struct *t);
extern int do_restart(struct cr_ctx *ctx, pid_t pid);
extern int cr_read_mm(struct cr_ctx *ctx);
+extern int cr_read_fd_table(struct cr_ctx *ctx);
#define cr_debug(fmt, args...) \
pr_debug("[%d:c/r:%s] " fmt, task_pid_vnr(current), __func__, ## args)
--
1.5.4.3
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