Dave Hansen [dave@xxxxxxxxxxxxxxxxxx] wrote:
|
| We have set up sane defaults for how filesystems should
| be checkpointed. However, as usual in the VFS, there
| are specialized places that will always need an ability
| to override these defaults.
|
| 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 /dev/null patch in a second, all
| that we have to do to make something like /dev/null
| supported is add a single "generic" f_op entry.
|
| Signed-off-by: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
| ---
|
| linux-2.6.git-dave/checkpoint/ckpt_file.c | 77 ++++++++++++++++----------
| linux-2.6.git-dave/include/linux/checkpoint.h | 6 ++
| linux-2.6.git-dave/include/linux/fs.h | 4 +
| 3 files changed, 60 insertions(+), 27 deletions(-)
|
| diff -puN checkpoint/ckpt_file.c~f_op-for-checkpointability checkpoint/ckpt_file.c
| --- linux-2.6.git/checkpoint/ckpt_file.c~f_op-for-checkpointability 2009-02-27 12:07:39.000000000 -0800
| +++ linux-2.6.git-dave/checkpoint/ckpt_file.c 2009-02-27 12:07:39.000000000 -0800
| @@ -104,56 +104,79 @@ int cr_explain_file(struct file *file, c
| return 0;
| }
|
| -int cr_file_supported(struct file *file)
| +typedef int (do_checkpoint_t)(struct file *, struct cr_ctx *,
| + struct cr_hdr_fd *);
| +
| +int generic_file_checkpoint(struct file *file, struct cr_ctx *ctx,
| + struct cr_hdr_fd *hh)
| +{
| + /*
| + * A NULL hh means to make a trial run not
| + * actually writing data. Just determine
| + * if the file is checkpointable.
| + */
| + if (!hh)
| + return 0;
| +
| + hh->f_flags = file->f_flags;
| + hh->f_mode = file->f_mode;
| + hh->f_pos = file->f_pos;
| + hh->f_version = file->f_version;
| + /* FIX: need also file->uid, file->gid, file->f_owner, etc */
| +
| + return 0;
| +}
| +
| +do_checkpoint_t *cr_file_get_func(struct file *file)
| {
Do we really need this helper ? IOW do callers need this function pointer
itself ? Or can we have a more generic helper that callers can use both
check if checkpoint is possible (pass NULL in ctx and hh) and to actually
checkpoint. Something like:
int cr_file_checkpoint(file, ctx, hh)
{
int rc = -1;
if (!cr_fs_checkpointable(fstype))
return rc;
if (!cr_file_checkpointable(file))
return rc;
if (special_file(file))
return rc;
op = file->f_op->checkpoint;
if (!op)
op = generic_file_checkpoint;
return (*op)(file, ctx, hh);
}
| struct inode *inode = file->f_dentry->d_inode;
| struct file_system_type *fs_type = inode->i_sb->s_type;
|
| - if (fs_is_cr_able(fs_type))
| - return 0;
| + if (file->f_op->checkpoint)
| + return file->f_op->checkpoint;
| +
| + if (!fs_is_cr_able(fs_type))
| + return NULL;
|
| if (special_file(inode->i_mode))
| - return 0;
| + return NULL;
|
| - return 1;
| + return generic_file_checkpoint;
| +}
| +
| +int cr_file_supported(struct file *file)
| +{
| + do_checkpoint_t *func = cr_file_get_func(file);
| +
| + if (func)
| + return !func(file, NULL, NULL);
| +
| + return 0;
| }
|
| /* 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)
| {
| + do_checkpoint_t *ckpt_func;
| struct cr_hdr h;
| struct cr_hdr_fd *hh = cr_hbuf_get(ctx, sizeof(*hh));
| - struct dentry *dent = file->f_dentry;
| - struct inode *inode = dent->d_inode;
| - enum fd_type fd_type;
| int ret;
|
| h.type = CR_HDR_FD_DATA;
| h.len = sizeof(*hh);
| h.parent = parent;
|
| - hh->f_flags = file->f_flags;
| - hh->f_mode = file->f_mode;
| - hh->f_pos = file->f_pos;
| - hh->f_version = file->f_version;
| - /* FIX: need also file->uid, file->gid, file->f_owner, etc */
| -
| - switch (inode->i_mode & S_IFMT) {
| - case S_IFREG:
| - fd_type = CR_FD_FILE;
| - break;
| - case S_IFDIR:
| - fd_type = CR_FD_DIR;
| - break;
| - default:
| - cr_hbuf_put(ctx, sizeof(*hh));
| - return -EBADF;
| - }
| + ckpt_func = cr_file_get_func(file);
| + ret = -EBADF;
| + if (!ckpt_func)
| + goto out;
|
| - /* FIX: check if the file/dir/link is unlinked */
| - hh->fd_type = fd_type;
| + ret = ckpt_func(file, ctx, hh);
| + if (ret)
| + goto out;
So we can combine these two steps into just one ?
ret = -EBADF;
hh->fd_type = fd_type;
if (cr_file_checkpoint(file, ctx, hh))
goto out;
|
| ret = cr_write_obj(ctx, &h, hh);
| +out:
| cr_hbuf_put(ctx, sizeof(*hh));
| if (ret < 0)
| return ret;
Sukadev
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