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Subject[PATCH v18 35/80] 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[v18]:
- Invoke set_close_on_exec() unconditionally on restart
Changelog[v17]:
- Validate f_mode after restore against saved f_mode
- Fail if f_flags have O_CREAT|O_EXCL|O_NOCTTY|O_TRUN
- 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 | 313 ++++++++++++++++++++++++++++++++++++++++++++
checkpoint/objhash.c | 2 +
checkpoint/process.c | 20 +++
include/linux/checkpoint.h | 7 +
4 files changed, 342 insertions(+), 0 deletions(-)

diff --git a/checkpoint/files.c b/checkpoint/files.c
index a554cbc..3cdfdb3 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/deferqueue.h>
#include <linux/checkpoint.h>
#include <linux/checkpoint_hdr.h>
@@ -415,3 +417,314 @@ int ckpt_collect_file_table(struct ckpt_ctx *ctx, struct task_struct *t)

return ret;
}
+
+/**************************************************************************
+ * Restart
+ */
+
+/**
+ * restore_open_fname - read a file name and open a file
+ * @ctx: checkpoint context
+ * @flags: file flags
+ */
+struct file *restore_open_fname(struct ckpt_ctx *ctx, int flags)
+{
+ struct ckpt_hdr *h;
+ struct file *file;
+ char *fname;
+
+ /* prevent bad input from doing bad things */
+ if (flags & (O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC))
+ return ERR_PTR(-EINVAL);
+
+ 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\n", fname, flags);
+
+ file = filp_open(fname, flags, 0);
+ 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)
+{
+ fmode_t new_mode = file->f_mode;
+ fmode_t saved_mode = (__force fmode_t) h->f_mode;
+ 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)
+ return ret;
+
+ /*
+ * Normally f_mode is set by open, and modified only via
+ * fcntl(), so its value now should match that at checkpoint.
+ * However, a file may be downgraded from (read-)write to
+ * read-only, e.g:
+ * - mark_files_ro() unsets FMODE_WRITE
+ * - nfs4_file_downgrade() too, and also sert FMODE_READ
+ * Validate the new f_mode against saved f_mode, allowing:
+ * - new with FMODE_WRITE, saved without FMODE_WRITE
+ * - new without FMODE_READ, saved with FMODE_READ
+ */
+ if ((new_mode & FMODE_WRITE) && !(saved_mode & FMODE_WRITE)) {
+ new_mode &= ~FMODE_WRITE;
+ if (!(new_mode & FMODE_READ) && (saved_mode & FMODE_READ))
+ new_mode |= FMODE_READ;
+ }
+ /* finally, at this point new mode should match saved mode */
+ if (new_mode ^ saved_mode)
+ return -EINVAL;
+
+ if (file->f_mode & FMODE_LSEEK)
+ ret = vfs_llseek(file, h->f_pos, SEEK_SET);
+
+ 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 = restore_open_fname(ctx, ptr->f_flags);
+ 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);
+ }
+
+ set_close_on_exec(h->fd_descriptor, h->fd_close_on_exec);
+ 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)
+ goto out;
+ }
+
+ ret = deferqueue_run(ctx->files_deferq);
+ ckpt_debug("files_deferq ran %d entries\n", ret);
+ if (ret > 0)
+ ret = 0;
+ 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 cefbab6..b7c8fdb 100644
--- a/checkpoint/objhash.c
+++ b/checkpoint/objhash.c
@@ -112,6 +112,7 @@ static struct ckpt_obj_ops ckpt_obj_ops[] = {
.ref_grab = obj_file_table_grab,
.ref_users = obj_file_table_users,
.checkpoint = checkpoint_file_table,
+ .restore = restore_file_table,
},
/* file object */
{
@@ -121,6 +122,7 @@ static struct ckpt_obj_ops ckpt_obj_ops[] = {
.ref_grab = obj_file_grab,
.ref_users = obj_file_users,
.checkpoint = checkpoint_file,
+ .restore = restore_file,
},
};

diff --git a/checkpoint/process.c b/checkpoint/process.c
index 042dc45..6ad9c01 100644
--- a/checkpoint/process.c
+++ b/checkpoint/process.c
@@ -349,6 +349,22 @@ 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;
+}
+
int restore_restart_block(struct ckpt_ctx *ctx)
{
struct ckpt_hdr_restart_block *h;
@@ -468,6 +484,10 @@ int restore_task(struct ckpt_ctx *ctx)
if (ret)
goto out;

+ ret = restore_task_objs(ctx);
+ ckpt_debug("objs %d\n", ret);
+ if (ret < 0)
+ goto out;
ret = restore_thread(ctx);
ckpt_debug("thread %d\n", ret);
if (ret < 0)
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 6fa5035..026d058 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -144,16 +144,23 @@ extern int restore_restart_block(struct ckpt_ctx *ctx);
extern int ckpt_collect_file_table(struct ckpt_ctx *ctx, struct task_struct *t);
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_fname(struct ckpt_ctx *ctx,
struct path *path, struct path *root);
+extern struct file *restore_open_fname(struct ckpt_ctx *ctx, int flags);
+
extern int ckpt_collect_file(struct ckpt_ctx *ctx, struct file *file);
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);

static inline int ckpt_validate_errno(int errno)
{
--
1.6.0.4


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