[RFC cr-pipe-v13][PATCH 2/3] Checkpoint open pipes
Oren Laadan
orenl at cs.columbia.edu
Tue Jan 27 13:23:14 PST 2009
A pipe is essentially a double-headed inode with a buffer attached to
it. We checkpoint the pipe buffer only once, as soon as we hit one
side of the pipe, regardless whether it is read- or write- end.
To checkpoint a file descriptor that refers to a pipe (either end), we
first lookup the inode in the hash table:
If not found, it is the first encounter of this pipe. Besides the file
descriptor, we also (a) save the pipe data, and (b) register the pipe
inode in the hash. We save the 'objref' of the inode 'in ->fd_objref'
of the file descriptor. The file descriptor type becomes CR_FD_PIPE.
If found, it is the second encounter of this pipe, namely, as we hit
the other end of the same pipe. In this case we need only record the
reference ('objref') to the inode that we had saved before, and the
file descriptor type is changed to CR_FD_OBJREF.
The type CR_FD_PIPE will indicate to the kernel to create a new pipe;
since both ends are created at the same time, one end will be used,
and the other end will be deposited in the hash table for later use.
The type CR_FD_OBJREF will indicate that the corresponding file
descriptor is already setup and registered in the hash using the
'->fd_objref' that it had been assigned.
The format of the pipe data is as follows:
struct cr_hdr_fd_pipe {
__u32 nr_bufs;
}
cr_hdr + cr_hdr_fd_ent
cr_hdr + cr_hdr_fd_data
cr_hdr + cr_hdr_fd_pipe -> # buffers
cr_hdr + cr_hdr_buffer -> 1st buffer
cr_hdr + cr_hdr_buffer -> 2nd buffer
cr_hdr + cr_hdr_buffer -> 3rd buffer
...
Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>
---
checkpoint/ckpt_file.c | 108 +++++++++++++++++++++++++++++++++++++++-
include/linux/checkpoint_hdr.h | 7 +++
2 files changed, 114 insertions(+), 1 deletions(-)
diff --git a/checkpoint/ckpt_file.c b/checkpoint/ckpt_file.c
index f5263f2..9ff401a 100644
--- a/checkpoint/ckpt_file.c
+++ b/checkpoint/ckpt_file.c
@@ -12,6 +12,7 @@
#include <linux/sched.h>
#include <linux/file.h>
#include <linux/fdtable.h>
+#include <linux/pipe_fs_i.h>
#include <linux/checkpoint.h>
#include <linux/checkpoint_hdr.h>
@@ -72,6 +73,81 @@ int cr_scan_fds(struct files_struct *files, int **fdtable)
return n;
}
+/* cr_write_pipebuf - dump contents of a pipe/fifo (assume i_mutex taken) */
+static int cr_write_pipebuf(struct cr_ctx *ctx, struct pipe_inode_info *pipe)
+{
+ struct cr_hdr h;
+ void *kbuf, *addr;
+ int i, ret = 0;
+
+ kbuf = (void *) __get_free_page(GFP_KERNEL);
+ if (!kbuf)
+ return -ENOMEM;
+
+ /* this is a simplified fs/pipe.c:read_pipe() */
+
+ for (i = 0; i < pipe->nrbufs; i++) {
+ int nn = (pipe->curbuf + i) & (PIPE_BUFFERS-1);
+ struct pipe_buffer *pbuf = pipe->bufs + nn;
+ const struct pipe_buf_operations *ops = pbuf->ops;
+
+ ret = ops->confirm(pipe, pbuf);
+ if (ret < 0)
+ break;
+
+ addr = ops->map(pipe, pbuf, 1);
+ memcpy(kbuf, addr + pbuf->offset, pbuf->len);
+ ops->unmap(pipe, pbuf, addr);
+
+ h.type = CR_HDR_BUFFER;
+ h.len = pbuf->len;
+ h.parent = 0;
+
+ ret = cr_write_obj(ctx, &h, kbuf);
+ if (ret < 0)
+ break;
+ }
+
+ free_page((unsigned long) kbuf);
+ return ret;
+}
+
+/* cr_write_pipe - dump pipe (assume i_mutex taken) */
+static int cr_write_pipe(struct cr_ctx *ctx, struct inode *inode, int parent)
+{
+ struct cr_hdr h;
+ struct cr_hdr_fd_pipe *hh;
+ struct pipe_inode_info *pipe = inode->i_pipe;
+ int ret;
+
+ h.type = CR_HDR_FD_PIPE;
+ h.len = sizeof(*hh);
+ h.parent = parent;
+
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ hh->nr_bufs = pipe->nrbufs;
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ return ret;
+
+ return cr_write_pipebuf(ctx, pipe);
+}
+
+/* cr_write_fd_fifo - for pipe */
+static int cr_write_fd_pipe(struct cr_ctx *ctx, struct file *file, int parent)
+{
+ struct inode *inode = file->f_dentry->d_inode;
+ int ret;
+
+ mutex_lock(&inode->i_mutex);
+ ret = cr_write_pipe(ctx, inode, parent);
+ mutex_unlock(&inode->i_mutex);
+
+ return ret;
+}
+
/* cr_write_fd_file - for regular files, directories, symbolic links */
static int cr_write_fd_file(struct cr_ctx *ctx, struct file *file, int parent)
{
@@ -86,11 +162,33 @@ static inline enum fd_type cr_inode_to_fdtype(struct inode *inode)
return CR_FD_FILE;
case S_IFDIR:
return CR_FD_DIR;
+ case S_IFIFO:
+ if (inode->i_sb->s_magic == PIPEFS_MAGIC)
+ return CR_FD_PIPE; /* pipe */
}
/* file type unsupported */
return -EBADF;
}
+/* cr_inode_to_objref: */
+static int
+cr_inode_to_objref(struct cr_ctx *ctx, struct inode *inode, int type, int *new)
+{
+ int objref = 0;
+ int newobj = 1;
+
+ if (type == CR_FD_PIPE) {
+ newobj = cr_obj_add_ptr(ctx, inode, &objref, CR_OBJ_INODE, 0);
+ pr_debug("objref %d inode %p new %d\n", objref, inode, newobj);
+ }
+
+ if (newobj < 0)
+ return newobj;
+
+ *new = newobj;
+ return objref;
+}
+
/* cr_write_fd_data - dump the state of a given file pointer */
static int cr_write_fd_data(struct cr_ctx *ctx, struct file *file, int parent)
{
@@ -98,6 +196,7 @@ static int cr_write_fd_data(struct cr_ctx *ctx, struct file *file, int parent)
struct cr_hdr_fd_data *hh = cr_hbuf_get(ctx, sizeof(*hh));
struct inode *inode = file->f_dentry->d_inode;
enum fd_type fd_type;
+ int new = 0; /* pacify gcc */
int ret;
h.type = CR_HDR_FD_DATA;
@@ -116,8 +215,12 @@ static int cr_write_fd_data(struct cr_ctx *ctx, struct file *file, int parent)
return fd_type;
}
+ hh->fd_objref = cr_inode_to_objref(ctx, inode, hh->fd_type, &new);
+ pr_debug("type %d objref %d (%d)\n", hh->fd_type, hh->fd_objref, new);
+ if (!new)
+ fd_type = CR_FD_OBJREF;
+
hh->fd_type = fd_type;
- hh->fd_objref = 0;
/* FIX: check if the inode is unlinked */
@@ -130,6 +233,9 @@ static int cr_write_fd_data(struct cr_ctx *ctx, struct file *file, int parent)
case CR_FD_OBJREF:
/* nothing to do */
break;
+ case CR_FD_PIPE:
+ ret = cr_write_fd_pipe(ctx, file, parent);
+ break;
case CR_FD_FILE:
case CR_FD_DIR:
ret = cr_write_fd_file(ctx, file, parent);
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index aba99f4..0cb1963 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -58,6 +58,7 @@ enum {
CR_HDR_FILES = 301,
CR_HDR_FD_ENT,
CR_HDR_FD_DATA,
+ CR_HDR_FD_PIPE,
CR_HDR_TAIL = 5001
};
@@ -147,6 +148,7 @@ enum fd_type {
CR_FD_OBJREF = 1,
CR_FD_FILE,
CR_FD_DIR,
+ CR_FD_PIPE,
};
struct cr_hdr_fd_data {
@@ -159,4 +161,9 @@ struct cr_hdr_fd_data {
__u64 f_version;
} __attribute__((aligned(8)));
+struct cr_hdr_fd_pipe {
+ __u32 nr_bufs;
+} __attribute__((aligned(8)));
+
+
#endif /* _CHECKPOINT_CKPT_HDR_H_ */
--
1.5.4.3
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