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SubjectRe: [rfc] rework aio migrate pages to use aio fs
On Tue, Sep 17, 2013 at 10:18:25AM -0400, Benjamin LaHaise wrote:
> +static int aio_set_page_dirty(struct page *page)
> +{
> + return 0;
> +};
> +
> +static const struct address_space_operations aio_aops = {
> + .set_page_dirty = aio_set_page_dirty,
> +};
> +
> +/*
> + * A single inode exists for each aio_inode file. The inodes are only
> + * used for mapping the event ring buffers in order to make it possible
> + * to provide migration ops to the vm.
> + */
> +static struct inode *aio_inode_mkinode(struct super_block *s)
> +{
> + struct inode *inode = new_inode_pseudo(s);
> +
> + if (!inode)
> + return ERR_PTR(-ENOMEM);
> +
> + inode->i_ino = get_next_ino();
> + inode->i_fop = &aio_ring_fops;
> + inode->i_mapping->a_ops = &aio_aops;
> +
> + /*
> + * Mark the inode dirty from the very beginning,
> + * that way it will never be moved to the dirty
> + * list because mark_inode_dirty() will think
> + * that it already _is_ on the dirty list.
> + */
> + inode->i_state = I_DIRTY;
> + inode->i_mode = S_IRUSR | S_IWUSR;
> + inode->i_uid = current_fsuid();
> + inode->i_gid = current_fsgid();
> + inode->i_flags |= S_PRIVATE;
> + inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
> + return inode;
> +}

FWIW, I would've taken that to fs/libfs.c, sans the assignment of ->i_fop.
BTW, are you sure that you want it to be opened via procfs symlink? Is that
even possible? IOW, what's that ->i_fop for?

> +struct file *aio_inode_getfile_private(const char *name,
> + const struct file_operations *fops,
> + void *priv, int flags)

Why is it not static? And why bother with fops as argument, etc.?

> + if (fops->owner && !try_module_get(fops->owner))
> + return ERR_PTR(-ENOENT);

Also pointless, AFAICS. BTW, you've just open-coded fops_get(fops), not
that it mattered in this case...

> + inode = aio_inode_mkinode(aio_mnt->mnt_sb);
> + if (IS_ERR(inode)) {
> + file = ERR_PTR(-ENOMEM);
> + goto err_module;
> + }
> +
> + /*
> + * Link the inode to a directory entry by creating a unique name
> + * using the inode sequence number.
> + */
> + file = ERR_PTR(-ENOMEM);
> + this.name = name;
> + this.len = strlen(name);
> + this.hash = 0;

Umm... ITYM
struct qstr this = QSTR_INIT("[aio]", 5);
, if not
path.dentry = d_alloc_pseudo(aio_mnt->mnt_sb,
&(struct qstr)QSTR_INIT("[aio]", 5));
> + if (!path.dentry)
> + goto err_module;
> +
> + path.mnt = mntget(aio_mnt);
> +
> + d_instantiate(path.dentry, inode);
> +
> + file = alloc_file(&path, OPEN_FMODE(flags), fops);
> + if (IS_ERR(file))
> + goto err_dput;

> + file->f_mapping = inode->i_mapping;

Pointless, BTW - alloc_file() will have already set it that way.

> + file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
> + file->private_data = priv;
> +
> + return file;
> +
> +err_dput:
> + path_put(&path);
> +err_module:
> + module_put(fops->owner);

And that module_put is pointless as well here.


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