[RFC][PATCH 09/11] check files for checkpointability

Dave Hansen
2009-03-05T16:40:52Z

Introduce a files_struct counter to indicate whether a particular
file_struct has ever contained a file which can not be
checkpointed. This flag is a one-way trip; once it is set, it may
not be unset.

We assume at allocation that a new files_struct is clean and may
be checkpointed. However, as soon as it has had its files filled
from its parent's, we check it for real in __scan_files_for_cr().
At that point, we mark it if it contained any uncheckpointable
files.

We also check each 'struct file' when it is installed in a fd
slot. This way, if anyone open()s or managed to dup() an
unsuppored file, we can catch it.

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
---

linux-2.6.git-dave/fs/file.c | 19 +++++++++++++++++++
linux-2.6.git-dave/fs/open.c | 5 +++++
linux-2.6.git-dave/include/linux/checkpoint.h | 13 +++++++++++++
linux-2.6.git-dave/include/linux/fdtable.h | 3 +++
4 files changed, 40 insertions(+)

diff -puN fs/file.c~242c7afafb1a81c0d9a41085536f2197d81146e7 fs/file.c
--- linux-2.6.git/fs/file.c~242c7afafb1a81c0d9a41085536f2197d81146e7 2009-03-05 08:37:04.000000000 -0800
+++ linux-2.6.git-dave/fs/file.c 2009-03-05 08:37:04.000000000 -0800
@@ -15,6 +15,7 @@
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/bitops.h>
+#include <linux/checkpoint.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
@@ -285,6 +286,20 @@ static int count_open_files(struct fdtab
return i;
}

+static void __scan_files_for_cr(struct files_struct *files)
+{
+ int i;
+
+ for (i = 0; i < files->fdtab.max_fds; i++) {
+ struct file *f = fcheck_files(files, i);
+ if (!f)
+ continue;
+ if (cr_file_supported(f))
+ continue;
+ files_deny_checkpointing(files);
+ }
+}
+
/*
* Allocate a new files structure and copy contents from the
* passed in files structure.
@@ -303,6 +318,9 @@ struct files_struct *dup_fd(struct files
goto out;

atomic_set(&newf->count, 1);
+#ifdef CONFIG_CHECKPOINT_RESTART
+ newf->may_checkpoint = 1;
+#endif

spin_lock_init(&newf->file_lock);
newf->next_fd = 0;
@@ -396,6 +414,7 @@ struct files_struct *dup_fd(struct files

rcu_assign_pointer(newf->fdt, new_fdt);

+ __scan_files_for_cr(newf);
return newf;

out_release:
diff -puN fs/open.c~242c7afafb1a81c0d9a41085536f2197d81146e7 fs/open.c
--- linux-2.6.git/fs/open.c~242c7afafb1a81c0d9a41085536f2197d81146e7 2009-03-05 08:37:04.000000000 -0800
+++ linux-2.6.git-dave/fs/open.c 2009-03-05 08:37:04.000000000 -0800
@@ -29,6 +29,7 @@
#include <linux/rcupdate.h>
#include <linux/audit.h>
#include <linux/falloc.h>
+#include <linux/checkpoint.h>

int vfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
@@ -1015,6 +1016,10 @@ void fd_install(unsigned int fd, struct
{
struct files_struct *files = current->files;
struct fdtable *fdt;
+
+ if (!cr_file_supported(file))
+ files_deny_checkpointing(files);
+
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
BUG_ON(fdt->fd[fd] != NULL);
diff -puN include/linux/checkpoint.h~242c7afafb1a81c0d9a41085536f2197d81146e7 include/linux/checkpoint.h
--- linux-2.6.git/include/linux/checkpoint.h~242c7afafb1a81c0d9a41085536f2197d81146e7 2009-03-05 08:37:04.000000000 -0800
+++ linux-2.6.git-dave/include/linux/checkpoint.h 2009-03-05 08:37:04.000000000 -0800
@@ -12,6 +12,7 @@

#include <linux/path.h>
#include <linux/fs.h>
+#include <linux/fdtable.h>

#ifdef CONFIG_CHECKPOINT_RESTART

@@ -101,11 +102,23 @@ extern int cr_read_files(struct cr_ctx *

#define pr_fmt(fmt) "[%d:c/r:%s] " fmt, task_pid_vnr(current), __func__

+static inline void __files_deny_checkpointing(struct files_struct *files,
+ char *file, int line)
+{
+ if (!test_and_clear_bit(0, &files->may_checkpoint))
+ return;
+ printk(KERN_INFO "process performed an action that can not be "
+ "checkpointed at: %s:%d\n", file, line);
+}
+#define files_deny_checkpointing(f) \
+ __files_deny_checkpointing(f, __FILE__, __LINE__)
+
int cr_explain_file(struct file *file, char *explain, int left);
int cr_file_supported(struct file *file);

#else /* !CONFIG_CHECKPOINT_RESTART */

+static inline void files_deny_checkpointing(struct files_struct *files) {}
static inline int cr_explain_file(struct file *file, char *explain, int left)
{
return 0;
diff -puN include/linux/fdtable.h~242c7afafb1a81c0d9a41085536f2197d81146e7 include/linux/fdtable.h
--- linux-2.6.git/include/linux/fdtable.h~242c7afafb1a81c0d9a41085536f2197d81146e7 2009-03-05 08:37:04.000000000 -0800
+++ linux-2.6.git-dave/include/linux/fdtable.h 2009-03-05 08:37:04.000000000 -0800
@@ -45,6 +45,9 @@ struct files_struct {
atomic_t count;
struct fdtable *fdt;
struct fdtable fdtab;
+#ifdef CONFIG_CHECKPOINT_RESTART
+ unsigned long may_checkpoint;
+#endif
/*
* written part on a separate cache line in SMP
*/
_