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Message-ID: <20061007082705.GA7294@infradead.org>
Date: Sat, 7 Oct 2006 09:27:05 +0100
From: Christoph Hellwig <hch@...radead.org>
To: Dave Hansen <haveblue@...ibm.com>
Cc: linux-kernel@...r.kernel.org, hch@...radead.org
Subject: Re: [RFC][PATCH] filesystem helpers for custom 'struct file's
On Wed, Sep 20, 2006 at 08:36:38AM -0700, Dave Hansen wrote:
> Some filesystems forego the vfs and may_open() and create their
> own 'struct file's.
>
> This patch creates a couple of helper functions which can be
> used by these filesystems, and will provide a unified place
> which the r/o bind mount code may patch.
>
> Signed-off-by: Dave Hansen <haveblue@...ibm.com>
> ---
>
> lxc-dave/include/linux/file.h | 8 ++++++++
> lxc-dave/fs/file_table.c | 30 ++++++++++++++++++++++++++++++
> lxc-dave/fs/hugetlbfs/inode.c | 22 +++++++++-------------
> lxc-dave/mm/shmem.c | 7 ++-----
> lxc-dave/mm/tiny-shmem.c | 24 +++++++++---------------
> lxc-dave/net/socket.c | 17 ++++++++---------
> 6 files changed, 66 insertions(+), 42 deletions(-)
>
> diff -puN include/linux/file.h~B0-helpers-for-custom-struct_files include/linux/file.h
> --- lxc/include/linux/file.h~B0-helpers-for-custom-struct_files 2006-09-19 10:36:47.000000000 -0700
> +++ lxc-dave/include/linux/file.h 2006-09-19 10:36:57.000000000 -0700
> @@ -67,6 +67,14 @@ struct files_struct {
> extern void FASTCALL(__fput(struct file *));
> extern void FASTCALL(fput(struct file *));
>
> +struct file_operations;
> +struct vfsmount;
> +struct dentry;
> +extern int f_init(struct file *, struct vfsmount *, struct dentry *dentry,
> + mode_t mode, const struct file_operations *fop);
> +extern struct file *f_alloc(struct vfsmount *, struct dentry *dentry,
> + mode_t mode, const struct file_operations *fop);
> +
To be honest I really hate this names. init_file and alloc_file sound
a lot better.
> +int f_init(struct file *file, struct vfsmount *mnt,
> + struct dentry *dentry, mode_t mode,
> + const struct file_operations *fop)
> +{
> + int error = 0;
> + file->f_vfsmnt = mntget(mnt);
> + file->f_dentry = dentry;
> + file->f_mapping = dentry->d_inode->i_mapping;
> + file->f_mode = mode;
> + file->f_op = fop;
> + return error;
> +}
> +
> +EXPORT_SYMBOL(f_init);
Do we really need this one? I think we should only need the
alloc version.
> diff -puN mm/shmem.c~B0-helpers-for-custom-struct_files mm/shmem.c
> --- lxc/mm/shmem.c~B0-helpers-for-custom-struct_files 2006-09-19 10:36:47.000000000 -0700
> +++ lxc-dave/mm/shmem.c 2006-09-19 10:36:57.000000000 -0700
> @@ -2411,11 +2411,8 @@ struct file *shmem_file_setup(char *name
> d_instantiate(dentry, inode);
> inode->i_size = size;
> inode->i_nlink = 0; /* It is unlinked */
> - file->f_vfsmnt = mntget(shm_mnt);
> - file->f_dentry = dentry;
> - file->f_mapping = inode->i_mapping;
> - file->f_op = &shmem_file_operations;
> - file->f_mode = FMODE_WRITE | FMODE_READ;
> + f_init(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
> + &shmem_file_operations);
> return file;
>
This should be able to use the alloc variant by moving the file allocation
after the inode allocation. Which makes a lot of sense anyway as
shmem_get_inode can fail for accounting reasons.
> {
> + struct dentry *dentry;
> struct qstr this;
> char name[32];
>
> @@ -356,18 +357,16 @@ static int sock_attach_fd(struct socket
> this.name = name;
> this.hash = SOCK_INODE(sock)->i_ino;
>
> - file->f_dentry = d_alloc(sock_mnt->mnt_sb->s_root, &this);
> - if (unlikely(!file->f_dentry))
> + dentry = d_alloc(sock_mnt->mnt_sb->s_root, &this);
> + if (unlikely(!dentry))
> return -ENOMEM;
>
> - file->f_dentry->d_op = &sockfs_dentry_operations;
> - d_add(file->f_dentry, SOCK_INODE(sock));
> - file->f_vfsmnt = mntget(sock_mnt);
> - file->f_mapping = file->f_dentry->d_inode->i_mapping;
> -
> + dentry->d_op = &sockfs_dentry_operations;
> + d_add(dentry, SOCK_INODE(sock));
> + f_init(file, sock_mnt, dentry, FMODE_READ | FMODE_WRITE,
> + &socket_file_ops);
> + SOCK_INODE(sock)->i_fop = &socket_file_ops;
> sock->file = file;
> - file->f_op = SOCK_INODE(sock)->i_fop = &socket_file_ops;
> - file->f_mode = FMODE_READ | FMODE_WRITE;
> file->f_flags = O_RDWR;
> file->f_pos = 0;
> file->private_data = sock;
Similarly the socket code wants a rework. The current split into sock_alloc_fd
and sock_attach_fd is highly confusing and the allocation of the file struct
before the inode doesn't make a lot of sense.
-
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