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Subject[PATCH v21 049/100] c/r: checkpoint and restore FIFOs
Date
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.

Changelog [v21]:
- Put file_ops->checkpoint under CONFIG_CHECKPOINT
Changelog [v19-rc3]:
- Rebase to kernel 2.6.33
Changelog [v19-rc1]:
- Switch to ckpt_obj_try_fetch()
- [Matt Helsley] Add cpp definitions for enums

Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
Acked-by: Serge E. Hallyn <serue@us.ibm.com>
Tested-by: Serge E. Hallyn <serue@us.ibm.com>
---
fs/checkpoint.c | 6 +++
fs/pipe.c | 80 +++++++++++++++++++++++++++++++++++++++-
include/linux/checkpoint_hdr.h | 2 +
include/linux/pipe_fs_i.h | 2 +
4 files changed, 89 insertions(+), 1 deletions(-)
diff --git a/fs/checkpoint.c b/fs/checkpoint.c
index e840d8a..06f1130 100644
--- a/fs/checkpoint.c
+++ b/fs/checkpoint.c
@@ -593,6 +593,12 @@ 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 void *restore_file(struct ckpt_ctx *ctx)
diff --git a/fs/pipe.c b/fs/pipe.c
index 801aad9..7f00e58 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -830,6 +830,8 @@ pipe_rdwr_open(struct inode *inode, struct file *filp)
return ret;
}

+static struct vfsmount *pipe_mnt __read_mostly;
+
#ifdef CONFIG_CHECKPOINT
static int checkpoint_pipe(struct ckpt_ctx *ctx, struct inode *inode)
{
@@ -877,7 +879,11 @@ 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);
@@ -887,6 +893,13 @@ 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->root_fs_path);
+ if (ret < 0)
+ goto out;
+ }
+
if (first)
ret = checkpoint_pipe(ctx, inode);
out:
@@ -978,6 +991,71 @@ 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_try_fetch() returned ERR_PTR(-EINVAL), this is the
+ * first time for this fifo.
+ */
+ file = ckpt_obj_try_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;
+}
#endif /* CONFIG_CHECKPOINT */

/*
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 50ef2b6..fbcbee7 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -286,6 +286,8 @@ enum file_type {
#define CKPT_FILE_GENERIC CKPT_FILE_GENERIC
CKPT_FILE_PIPE,
#define CKPT_FILE_PIPE CKPT_FILE_PIPE
+ CKPT_FILE_FIFO,
+#define CKPT_FILE_FIFO CKPT_FILE_FIFO
CKPT_FILE_MAX
#define CKPT_FILE_MAX 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
--
1.6.3.3


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