[PATCH v18 47/80] c/r: checkpoint and restore FIFOs

Oren Laadan
2009-09-24T00:32:29Z

FIFOs are almost like pipes.

Checkpoints adds the FIFO pathname. The first time the FIFO is found
it also assigns an @objref and dumps the contents in the buffers.

To restore, use the @objref only to determine whether a particular
FIFO has already been restored earlier. Note that it ignores the file
pointer that matches that @objref (unlike with pipes, where that file
corresponds to the other end of the pipe). Instead, it creates a new
FIFO using the saved pathname.

Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
---
checkpoint/files.c | 6 +++
fs/pipe.c | 82 +++++++++++++++++++++++++++++++++++++++-
include/linux/checkpoint_hdr.h | 1 +
include/linux/pipe_fs_i.h | 2 +
4 files changed, 89 insertions(+), 2 deletions(-)

diff --git a/checkpoint/files.c b/checkpoint/files.c
index 042f620..190c95b 100644
--- a/checkpoint/files.c
+++ b/checkpoint/files.c
@@ -571,6 +571,12 @@ static struct restore_file_ops restore_file_ops[] = {
.file_type = CKPT_FILE_PIPE,
.restore = pipe_file_restore,
},
+ /* fifo */
+ {
+ .file_name = "FIFO",
+ .file_type = CKPT_FILE_FIFO,
+ .restore = fifo_file_restore,
+ },
};

static struct file *do_restore_file(struct ckpt_ctx *ctx)
diff --git a/fs/pipe.c b/fs/pipe.c
index 30b34a2..65ad44e 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -811,6 +811,8 @@ pipe_rdwr_open(struct inode *inode, struct file *filp)
return 0;
}

+static struct vfsmount *pipe_mnt __read_mostly;
+
#ifdef CONFIG_CHECKPOINT
static int checkpoint_pipe(struct ckpt_ctx *ctx, struct inode *inode)
{
@@ -858,7 +860,11 @@ static int pipe_file_checkpoint(struct ckpt_ctx *ctx, struct file *file)
if (!h)
return -ENOMEM;

- h->common.f_type = CKPT_FILE_PIPE;
+ /* fifo and pipe are similar at checkpoint, differ on restore */
+ if (inode->i_sb == pipe_mnt->mnt_sb)
+ h->common.f_type = CKPT_FILE_PIPE;
+ else
+ h->common.f_type = CKPT_FILE_FIFO;
h->pipe_objref = objref;

ret = checkpoint_file_common(ctx, file, &h->common);
@@ -868,6 +874,13 @@ static int pipe_file_checkpoint(struct ckpt_ctx *ctx, struct file *file)
if (ret < 0)
goto out;

+ /* FIFO also needs a file name */
+ if (h->common.f_type == CKPT_FILE_FIFO) {
+ ret = checkpoint_fname(ctx, &file->f_path, &ctx->fs_mnt);
+ if (ret < 0)
+ goto out;
+ }
+
if (first)
ret = checkpoint_pipe(ctx, inode);
out:
@@ -959,8 +972,74 @@ struct file *pipe_file_restore(struct ckpt_ctx *ctx, struct ckpt_hdr_file *ptr)

return file;
}
+
+struct file *fifo_file_restore(struct ckpt_ctx *ctx, struct ckpt_hdr_file *ptr)
+{
+ struct ckpt_hdr_file_pipe *h = (struct ckpt_hdr_file_pipe *) ptr;
+ struct file *file;
+ int first, ret;
+
+ if (ptr->h.type != CKPT_HDR_FILE ||
+ ptr->h.len != sizeof(*h) || ptr->f_type != CKPT_FILE_FIFO)
+ return ERR_PTR(-EINVAL);
+
+ if (h->pipe_objref <= 0)
+ return ERR_PTR(-EINVAL);
+
+ /*
+ * If ckpt_obj_fetch() returned ERR_PTR(-EINVAL), this is the
+ * first time for this fifo.
+ */
+ file = ckpt_obj_fetch(ctx, h->pipe_objref, CKPT_OBJ_FILE);
+ if (!IS_ERR(file))
+ first = 0;
+ else if (PTR_ERR(file) == -EINVAL)
+ first = 1;
+ else
+ return file;
+
+ /*
+ * To avoid blocking, always open the fifo with O_RDWR;
+ * then fix flags below.
+ */
+ file = restore_open_fname(ctx, (ptr->f_flags & ~O_ACCMODE) | O_RDWR);
+ if (IS_ERR(file))
+ return file;
+
+ if ((ptr->f_flags & O_ACCMODE) == O_RDONLY) {
+ file->f_flags = (file->f_flags & ~O_ACCMODE) | O_RDONLY;
+ file->f_mode &= ~FMODE_WRITE;
+ } else if ((ptr->f_flags & O_ACCMODE) == O_WRONLY) {
+ file->f_flags = (file->f_flags & ~O_ACCMODE) | O_WRONLY;
+ file->f_mode &= ~FMODE_READ;
+ } else if ((ptr->f_flags & O_ACCMODE) != O_RDWR) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ /* first time: add to objhash and restore fifo's contents */
+ if (first) {
+ ret = ckpt_obj_insert(ctx, file, h->pipe_objref, CKPT_OBJ_FILE);
+ if (ret < 0)
+ goto out;
+
+ ret = restore_pipe(ctx, file);
+ if (ret < 0)
+ goto out;
+ }
+
+ ret = restore_file_common(ctx, file, ptr);
+ out:
+ if (ret < 0) {
+ fput(file);
+ file = ERR_PTR(ret);
+ }
+
+ return file;
+}
#else
#define pipe_file_checkpoint NULL
+#define fifo_file_checkpoint NULL
#endif /* CONFIG_CHECKPOINT */

/*
@@ -1043,7 +1122,6 @@ void free_pipe_info(struct inode *inode)
inode->i_pipe = NULL;
}

-static struct vfsmount *pipe_mnt __read_mostly;
static int pipefs_delete_dentry(struct dentry *dentry)
{
/*
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 68f64ae..7e64b77 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -222,6 +222,7 @@ enum file_type {
CKPT_FILE_IGNORE = 0,
CKPT_FILE_GENERIC,
CKPT_FILE_PIPE,
+ CKPT_FILE_FIFO,
CKPT_FILE_MAX
};

diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index e526a12..596403e 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -160,6 +160,8 @@ struct ckpt_ctx;
struct ckpt_hdr_file;
extern struct file *pipe_file_restore(struct ckpt_ctx *ctx,
struct ckpt_hdr_file *ptr);
+extern struct file *fifo_file_restore(struct ckpt_ctx *ctx,
+ struct ckpt_hdr_file *ptr);
#endif

#endif
--
1.6.0.4