[RFC v14-rc3][PATCH 10/36] actually use f_op in checkpoint code

[Oren Laadan]

From: Dave Hansen <dave at linux.vnet.ibm.com>

Right now, we assume all normal files and directories
can be checkpointed.  However, as usual in the VFS, there
are specialized places that will always need an ability
to override these defaults.  We could do this completely
in the checkpoint code, but that would bitrot quickly.

This adds a new 'file_operations' function for
checkpointing a file.  I did this under the assumption
that we should have a dirt-simple way to make something
(un)checkpointable that fits in with current code.

As you can see in the ext[234] and /proc patches, all
that we have to do to make something simple be
supported is add a single "generic" f_op entry.

Signed-off-by: Dave Hansen <dave at linux.vnet.ibm.com>
Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>
Acked-by: Serge Hallyn <serue at us.ibm.com>
---
 checkpoint/ckpt_file.c |   31 +++++++++++++++----------------
 include/linux/fs.h     |   11 +++++++++++
 2 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/checkpoint/ckpt_file.c b/checkpoint/ckpt_file.c
index 336c119..f813d02 100644
--- a/checkpoint/ckpt_file.c
+++ b/checkpoint/ckpt_file.c
@@ -91,6 +91,11 @@ static int cr_write_file_generic(struct cr_ctx *ctx, struct file *file,
 
 	hh->fd_type = CR_FD_GENERIC;
 
+	/*
+	 * FIXME: when we'll add support for unlinked files/dirs, we'll
+	 * need to distinguish between unlinked filed and unlinked dirs.
+	 */
+
 	ret = cr_write_obj(ctx, &h, hh);
 	if (ret < 0)
 		return ret;
@@ -98,12 +103,16 @@ static int cr_write_file_generic(struct cr_ctx *ctx, struct file *file,
 	return cr_write_fname(ctx, &file->f_path, &ctx->fs_mnt);
 }
 
+int generic_file_checkpoint(struct cr_ctx *ctx, struct file *file,
+			    struct cr_hdr_file *hh)
+{
+	return cr_write_file_generic(ctx, file, hh);
+}
+
 /* cr_write_file - dump the state of a given file pointer */
 static int cr_write_file(struct cr_ctx *ctx, struct file *file)
 {
 	struct cr_hdr_file *hh;
-	struct dentry *dent = file->f_dentry;
-	struct inode *inode = dent->d_inode;
 	int ret;
 
 	hh = cr_hbuf_get(ctx, sizeof(*hh));
@@ -116,21 +125,11 @@ static int cr_write_file(struct cr_ctx *ctx, struct file *file)
 	hh->f_version = file->f_version;
 	/* FIX: need also file->uid, file->gid, file->f_owner, etc */
 
-	/*
-	 * FIXME: when we'll add support for unlinked files/dirs, we'll
-	 * need to distinguish between unlinked filed and unlinked dirs.
-	 */
-	switch (inode->i_mode & S_IFMT) {
-	case S_IFREG:
-	case S_IFDIR:
-		ret = cr_write_file_generic(ctx, file, hh);
-		break;
-	default:
-		ret = -EBADF;
-		break;
-	}
-	cr_hbuf_put(ctx, sizeof(*hh));
+	ret = -EBADF;
+	if (file->f_op->checkpoint)
+		ret = file->f_op->checkpoint(ctx, file, hh);
 
+	cr_hbuf_put(ctx, sizeof(*hh));
 	return ret;
 }
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3bf5057..1f9925b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1296,6 +1296,14 @@ int generic_osync_inode(struct inode *, struct address_space *, int);
 typedef int (*filldir_t)(void *, const char *, int, loff_t, u64, unsigned);
 struct block_device_operations;
 
+#ifdef CONFIG_CHECKPOINT
+struct cr_ctx;
+struct cr_hdr_file;
+int generic_file_checkpoint(struct cr_ctx *, struct file *, struct cr_hdr_file *);
+#else
+#define generic_file_checkpoint NULL
+#endif
+
 /* These macros are for out of kernel modules to test that
  * the kernel supports the unlocked_ioctl and compat_ioctl
  * fields in struct file_operations. */
@@ -1334,6 +1342,9 @@ struct file_operations {
 	ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
 	ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
 	int (*setlease)(struct file *, long, struct file_lock **);
+#ifdef CONFIG_CHECKPOINT
+	int (*checkpoint)(struct cr_ctx *, struct file *, struct cr_hdr_file *);
+#endif
 };
 
 struct inode_operations {
-- 
1.5.4.3