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Subject[RFC v16][PATCH 10/43] c/r: restore open file descriptors
Date
For each fd read 'struct ckpt_hdr_file_desc' and lookup objref in the
hash table; If not found in the hash table, (first occurence), read in
'struct ckpt_hdr_file', create a new file and register in the hash.
Otherwise attach the file pointer from the hash as an FD.

Changelog[v16]:
- Reorder patch (move earlier in series)
- Handle shared files_struct objects

Changelog[v14]:
- Introduce a per file-type restore() callback
- Revert change to pr_debug(), back to ckpt_debug()
- Rename: restore_files() => restore_fd_table()
- Rename: ckpt_read_fd_data() => restore_file()
- Check whether calls to ckpt_hbuf_get() fail
- Discard field 'hh->parent'

Changelog[v12]:
- Replace obsolete ckpt_debug() with pr_debug()

Changelog[v6]:
- Balance all calls to ckpt_hbuf_get() with matching ckpt_hbuf_put()
(even though it's not really needed)

Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
---
checkpoint/files.c | 285 ++++++++++++++++++++++++++++++++++++++++++++
checkpoint/objhash.c | 2 +
checkpoint/process.c | 20 +++
checkpoint/restart.c | 9 ++
include/linux/checkpoint.h | 5 +
5 files changed, 321 insertions(+), 0 deletions(-)
diff --git a/checkpoint/files.c b/checkpoint/files.c
index d10dfb6..d7583d3 100644
--- a/checkpoint/files.c
+++ b/checkpoint/files.c
@@ -16,6 +16,8 @@
#include <linux/sched.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>

@@ -309,3 +311,286 @@ int checkpoint_obj_file_table(struct ckpt_ctx *ctx, struct task_struct *t)

return objref;
}
+
+/**************************************************************************
+ * Restart
+ */
+
+/**
+ * read_open_fname - read a file name and open a file
+ * @ctx: checkpoint context
+ * @flags: file flags
+ * @mode: file mode
+ */
+static struct file *read_open_fname(struct ckpt_ctx *ctx, int flags, int mode)
+{
+ struct ckpt_hdr *h;
+ struct file *file;
+ char *fname;
+
+ h = ckpt_read_buf_type(ctx, PATH_MAX, CKPT_HDR_FILE_NAME);
+ if (IS_ERR(h))
+ return (struct file *) h;
+ fname = (char *) (h + 1);
+ ckpt_debug("fname '%s' flags %#x mode %#x\n", fname, flags, mode);
+
+ file = filp_open(fname, flags, mode);
+ ckpt_hdr_put(ctx, h);
+ return file;
+}
+
+static int close_all_fds(struct files_struct *files)
+{
+ int *fdtable;
+ int nfds;
+
+ nfds = scan_fds(files, &fdtable);
+ if (nfds < 0)
+ return nfds;
+ while (nfds--)
+ sys_close(fdtable[nfds]);
+ kfree(fdtable);
+ return 0;
+}
+
+/**
+ * attach_file - attach a lonely file ptr to a file descriptor
+ * @file: lonely file pointer
+ */
+static int attach_file(struct file *file)
+{
+ int fd = get_unused_fd_flags(0);
+
+ if (fd >= 0) {
+ get_file(file);
+ fsnotify_open(file->f_path.dentry);
+ fd_install(fd, file);
+ }
+ return fd;
+}
+
+#define CKPT_SETFL_MASK \
+ (O_APPEND | O_NONBLOCK | O_NDELAY | FASYNC | O_DIRECT | O_NOATIME)
+
+int restore_file_common(struct ckpt_ctx *ctx, struct file *file,
+ struct ckpt_hdr_file *h)
+{
+ int ret;
+
+ /* FIX: need to restore uid, gid, owner etc */
+
+ /* safe to set 1st arg (fd) to 0, as command is F_SETFL */
+ ret = vfs_fcntl(0, F_SETFL, h->f_flags & CKPT_SETFL_MASK, file);
+ if (ret < 0)
+ goto out;
+
+ ret = vfs_llseek(file, h->f_pos, SEEK_SET);
+ if (ret == -ESPIPE) /* ignore error on non-seekable files */
+ ret = 0;
+ out:
+ return ret;
+}
+
+static struct file *generic_file_restore(struct ckpt_ctx *ctx,
+ struct ckpt_hdr_file *ptr)
+{
+ struct file *file;
+ int ret;
+
+ if (ptr->h.type != CKPT_HDR_FILE ||
+ ptr->h.len != sizeof(*ptr) || ptr->f_type != CKPT_FILE_GENERIC)
+ return ERR_PTR(-EINVAL);
+
+ file = read_open_fname(ctx, ptr->f_flags, ptr->f_mode);
+ if (IS_ERR(file))
+ return file;
+
+ ret = restore_file_common(ctx, file, ptr);
+ if (ret < 0) {
+ fput(file);
+ file = ERR_PTR(ret);
+ }
+ return file;
+}
+
+struct restore_file_ops {
+ char *file_name;
+ enum file_type file_type;
+ struct file * (*restore) (struct ckpt_ctx *ctx,
+ struct ckpt_hdr_file *ptr);
+};
+
+static struct restore_file_ops restore_file_ops[] = {
+ /* ignored file */
+ {
+ .file_name = "IGNORE",
+ .file_type = CKPT_FILE_IGNORE,
+ .restore = NULL,
+ },
+ /* regular file/directory */
+ {
+ .file_name = "GENERIC",
+ .file_type = CKPT_FILE_GENERIC,
+ .restore = generic_file_restore,
+ },
+};
+
+static struct file *do_restore_file(struct ckpt_ctx *ctx)
+{
+ struct restore_file_ops *ops;
+ struct ckpt_hdr_file *h;
+ struct file *file = ERR_PTR(-EINVAL);
+
+ /*
+ * All 'struct ckpt_hdr_file_...' begin with ckpt_hdr_file,
+ * but the actual object depends on the file type. The length
+ * should never be more than page.
+ */
+ h = ckpt_read_buf_type(ctx, PAGE_SIZE, CKPT_HDR_FILE);
+ if (IS_ERR(h))
+ return (struct file *) h;
+ ckpt_debug("flags %#x mode %#x type %d\n",
+ h->f_flags, h->f_mode, h->f_type);
+
+ if (h->f_type >= CKPT_FILE_MAX)
+ goto out;
+
+ ops = &restore_file_ops[h->f_type];
+ BUG_ON(ops->file_type != h->f_type);
+
+ if (ops->restore)
+ file = ops->restore(ctx, h);
+ out:
+ ckpt_hdr_put(ctx, h);
+ return file;
+}
+
+/* restore callback for file pointer */
+void *restore_file(struct ckpt_ctx *ctx)
+{
+ return (void *) do_restore_file(ctx);
+}
+
+/**
+ * ckpt_read_file_desc - 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 restore_file to restore the file too.
+ */
+static int restore_file_desc(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_file_desc *h;
+ struct file *file;
+ int newfd, ret;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_FILE_DESC);
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+ ckpt_debug("ref %d fd %d c.o.e %d\n",
+ h->fd_objref, h->fd_descriptor, h->fd_close_on_exec);
+
+ ret = -EINVAL;
+ if (h->fd_objref <= 0 || h->fd_descriptor < 0)
+ goto out;
+
+ file = ckpt_obj_fetch(ctx, h->fd_objref, CKPT_OBJ_FILE);
+ if (IS_ERR(file)) {
+ ret = PTR_ERR(file);
+ goto out;
+ }
+
+ newfd = attach_file(file);
+ if (newfd < 0) {
+ ret = newfd;
+ goto out;
+ }
+
+ ckpt_debug("newfd got %d wanted %d\n", newfd, h->fd_descriptor);
+
+ /* reposition if newfd isn't desired fd */
+ if (newfd != h->fd_descriptor) {
+ ret = sys_dup2(newfd, h->fd_descriptor);
+ if (ret < 0)
+ goto out;
+ sys_close(newfd);
+ }
+
+ if (h->fd_close_on_exec)
+ set_close_on_exec(h->fd_descriptor, 1);
+
+ ret = 0;
+ out:
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
+/* restore callback for file table */
+static struct files_struct *do_restore_file_table(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_file_table *h;
+ struct files_struct *files;
+ int i, ret;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_FILE_TABLE);
+ if (IS_ERR(h))
+ return (struct files_struct *) h;
+
+ ckpt_debug("nfds %d\n", h->fdt_nfds);
+
+ ret = -EMFILE;
+ if (h->fdt_nfds < 0 || h->fdt_nfds > sysctl_nr_open)
+ goto out;
+
+ /*
+ * We assume that restarting tasks, as created in user-space,
+ * have distinct files_struct objects each. If not, we need to
+ * call dup_fd() to make sure we don't overwrite an already
+ * restored one.
+ */
+
+ /* point of no return -- close all file descriptors */
+ ret = close_all_fds(current->files);
+ if (ret < 0)
+ goto out;
+
+ for (i = 0; i < h->fdt_nfds; i++) {
+ ret = restore_file_desc(ctx);
+ if (ret < 0)
+ break;
+ }
+ out:
+ ckpt_hdr_put(ctx, h);
+ if (!ret) {
+ files = current->files;
+ atomic_inc(&files->count);
+ } else {
+ files = ERR_PTR(ret);
+ }
+ return files;
+}
+
+void *restore_file_table(struct ckpt_ctx *ctx)
+{
+ return (void *) do_restore_file_table(ctx);
+}
+
+int restore_obj_file_table(struct ckpt_ctx *ctx, int files_objref)
+{
+ struct files_struct *files;
+
+ files = ckpt_obj_fetch(ctx, files_objref, CKPT_OBJ_FILE_TABLE);
+ if (IS_ERR(files))
+ return PTR_ERR(files);
+
+ if (files != current->files) {
+ task_lock(current);
+ put_files_struct(current->files);
+ current->files = files;
+ task_unlock(current);
+ atomic_inc(&files->count);
+ }
+
+ return 0;
+}
diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
index ea15958..f5c9f7c 100644
--- a/checkpoint/objhash.c
+++ b/checkpoint/objhash.c
@@ -92,6 +92,7 @@ static struct ckpt_obj_ops ckpt_obj_ops[] = {
.ref_drop = obj_file_table_drop,
.ref_grab = obj_file_table_grab,
.checkpoint = checkpoint_file_table,
+ .restore = restore_file_table,
},
/* file object */
{
@@ -100,6 +101,7 @@ static struct ckpt_obj_ops ckpt_obj_ops[] = {
.ref_drop = obj_file_drop,
.ref_grab = obj_file_grab,
.checkpoint = checkpoint_file,
+ .restore = restore_file,
},
};

diff --git a/checkpoint/process.c b/checkpoint/process.c
index 4c922b6..5fd1573 100644
--- a/checkpoint/process.c
+++ b/checkpoint/process.c
@@ -121,6 +121,22 @@ static int restore_task_struct(struct ckpt_ctx *ctx)
return ret;
}

+static int restore_task_objs(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_task_objs *h;
+ int ret;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_TASK_OBJS);
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+
+ ret = restore_obj_file_table(ctx, h->files_objref);
+ ckpt_debug("file_table: ret %d (%p)\n", ret, current->files);
+
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
/* read the entire state of the current task */
int restore_task(struct ckpt_ctx *ctx)
{
@@ -130,6 +146,10 @@ int restore_task(struct ckpt_ctx *ctx)
ckpt_debug("task %d\n", ret);
if (ret < 0)
goto out;
+ ret = restore_task_objs(ctx);
+ ckpt_debug("shared %d\n", ret);
+ if (ret < 0)
+ goto out;
ret = restore_thread(ctx);
ckpt_debug("thread %d\n", ret);
if (ret < 0)
diff --git a/checkpoint/restart.c b/checkpoint/restart.c
index ce52e30..d3d6c5e 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -351,10 +351,19 @@ static int restore_read_tail(struct ckpt_ctx *ctx)
return ret;
}

+/* setup restart-specific parts of ctx */
+static int init_restart_ctx(struct ckpt_ctx *ctx)
+{
+ return 0;
+}
+
int do_restart(struct ckpt_ctx *ctx, pid_t pid)
{
int ret;

+ ret = init_restart_ctx(ctx);
+ if (ret < 0)
+ return ret;
ret = restore_read_header(ctx);
if (ret < 0)
return ret;
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index d170988..bb14a66 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -70,13 +70,18 @@ extern int restore_cpu(struct ckpt_ctx *ctx);
/* file table */
extern int checkpoint_obj_file_table(struct ckpt_ctx *ctx,
struct task_struct *t);
+extern int restore_obj_file_table(struct ckpt_ctx *ctx, int files_objref);
extern int checkpoint_file_table(struct ckpt_ctx *ctx, void *ptr);
+extern void *restore_file_table(struct ckpt_ctx *ctx);

/* files */
extern int checkpoint_file(struct ckpt_ctx *ctx, void *ptr);
+extern void *restore_file(struct ckpt_ctx *ctx);

extern int checkpoint_file_common(struct ckpt_ctx *ctx, struct file *file,
struct ckpt_hdr_file *h);
+extern int restore_file_common(struct ckpt_ctx *ctx, struct file *file,
+ struct ckpt_hdr_file *h);


/* debugging flags */
--
1.6.0.4


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