Subject: Re: [PATCH 2/2] fix up new filp allocators
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Dave Hansen <haveblue@us.ibm.com>
Cc: ezk@cs.sunysb.edu, akpm@osdl.org, linux-kernel@vger.kernel.org,
       hch@infradead.org
In-Reply-To: <20071109210440.497630FB@kernel>
References: <20071109210439.122065A3@kernel>
	 <20071109210440.497630FB@kernel>
Content-Type: text/plain
Date: Fri, 09 Nov 2007 16:26:11 -0500
Message-Id: <1194643571.7459.107.camel@heimdal.trondhjem.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Fri, 2007-11-09 at 13:04 -0800, Dave Hansen wrote:
> Some new uses of get_empty_filp() have crept in, and are
> not properly taking mnt_want_write()s.  This fixes them
> up.
> 
> We really need to kill get_empty_filp().
> 
> Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
> ---
> 
>  linux-2.6.git-dave/fs/anon_inodes.c    |   16 ++++++----------
>  linux-2.6.git-dave/fs/file_table.c     |    6 ++++++
>  linux-2.6.git-dave/fs/nfsd/nfs4state.c |    3 ++-
>  linux-2.6.git-dave/fs/pipe.c           |   17 +++++++----------
>  4 files changed, 21 insertions(+), 21 deletions(-)
> 
> diff -puN fs/anon_inodes.c~fix-idmapd-bug fs/anon_inodes.c
> --- linux-2.6.git/fs/anon_inodes.c~fix-idmapd-bug	2007-11-09 12:13:15.000000000 -0800
> +++ linux-2.6.git-dave/fs/anon_inodes.c	2007-11-09 12:13:15.000000000 -0800
> @@ -81,13 +81,10 @@ int anon_inode_getfd(int *pfd, struct in
>  
>  	if (IS_ERR(anon_inode_inode))
>  		return -ENODEV;
> -	file = get_empty_filp();
> -	if (!file)
> -		return -ENFILE;
>  
>  	error = get_unused_fd();
>  	if (error < 0)
> -		goto err_put_filp;
> +		return error;
>  	fd = error;
>  
>  	/*
> @@ -114,14 +111,15 @@ int anon_inode_getfd(int *pfd, struct in
>  	dentry->d_flags &= ~DCACHE_UNHASHED;
>  	d_instantiate(dentry, anon_inode_inode);
>  
> -	file->f_path.mnt = mntget(anon_inode_mnt);
> -	file->f_path.dentry = dentry;
> +	error = -ENFILE;
> +	file = alloc_file(anon_inode_mnt, dentry,
> +			  FMODE_READ | FMODE_WRITE, fops);
> +	if (!file)
> +		goto err_put_unused_fd;
>  	file->f_mapping = anon_inode_inode->i_mapping;
>  
>  	file->f_pos = 0;
>  	file->f_flags = O_RDWR;
> -	file->f_op = fops;
> -	file->f_mode = FMODE_READ | FMODE_WRITE;
>  	file->f_version = 0;
>  	file->private_data = priv;
>  
> @@ -134,8 +132,6 @@ int anon_inode_getfd(int *pfd, struct in
>  
>  err_put_unused_fd:
>  	put_unused_fd(fd);
> -err_put_filp:
> -	put_filp(file);
>  	return error;
>  }
>  EXPORT_SYMBOL_GPL(anon_inode_getfd);
> diff -puN fs/file_table.c~fix-idmapd-bug fs/file_table.c
> --- linux-2.6.git/fs/file_table.c~fix-idmapd-bug	2007-11-09 12:13:15.000000000 -0800
> +++ linux-2.6.git-dave/fs/file_table.c	2007-11-09 12:13:15.000000000 -0800
> @@ -89,6 +89,12 @@ int proc_nr_files(ctl_table *table, int 
>  /* Find an unused file structure and return a pointer to it.
>   * Returns NULL, if there are no more free file structures or
>   * we run out of memory.
> + *
> + * Be very careful using this.  You are responsible for
> + * getting write access to any mount that you might assign
> + * to this filp, if it is opened for write.  If this is not
> + * done, you will imbalance int the mount's writer count
> + * and a warning at __fput() time.
>   */
>  struct file *get_empty_filp(void)
>  {
> diff -puN fs/nfsd/nfs4state.c~fix-idmapd-bug fs/nfsd/nfs4state.c
> --- linux-2.6.git/fs/nfsd/nfs4state.c~fix-idmapd-bug	2007-11-09 12:13:15.000000000 -0800
> +++ linux-2.6.git-dave/fs/nfsd/nfs4state.c	2007-11-09 12:13:15.000000000 -0800
> @@ -41,6 +41,7 @@
>  #include <linux/sunrpc/svc.h>
>  #include <linux/nfsd/nfsd.h>
>  #include <linux/nfsd/cache.h>
> +#include <linux/file.h>
>  #include <linux/mount.h>
>  #include <linux/workqueue.h>
>  #include <linux/smp_lock.h>
> @@ -1303,7 +1304,7 @@ static inline void
>  nfs4_file_downgrade(struct file *filp, unsigned int share_access)
>  {
>  	if (share_access & NFS4_SHARE_ACCESS_WRITE) {
> -		put_write_access(filp->f_path.dentry->d_inode);
> +		drop_file_write_access(filp);
>  		filp->f_mode = (filp->f_mode | FMODE_READ) & ~FMODE_WRITE;
>  	}
>  }


Hmm... The NFS server may also try to 'upgrade' an open file request to
a read/write request whenever the client issues a new OPEN request for
WRITE using the same open_owner.

> diff -puN fs/pipe.c~fix-idmapd-bug fs/pipe.c
> --- linux-2.6.git/fs/pipe.c~fix-idmapd-bug	2007-11-09 12:13:15.000000000 -0800
> +++ linux-2.6.git-dave/fs/pipe.c	2007-11-09 12:13:15.000000000 -0800
> @@ -959,13 +959,10 @@ struct file *create_write_pipe(void)
>  	struct dentry *dentry;
>  	struct qstr name = { .name = "" };
>  
> -	f = get_empty_filp();
> -	if (!f)
> -		return ERR_PTR(-ENFILE);
>  	err = -ENFILE;
>  	inode = get_pipe_inode();
>  	if (!inode)
> -		goto err_file;
> +		goto err;
>  
>  	err = -ENOMEM;
>  	dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
> @@ -980,13 +977,14 @@ struct file *create_write_pipe(void)
>  	 */
>  	dentry->d_flags &= ~DCACHE_UNHASHED;
>  	d_instantiate(dentry, inode);
> -	f->f_path.mnt = mntget(pipe_mnt);
> -	f->f_path.dentry = dentry;
> +
> +	f = alloc_file(pipe_mnt, dentry, FMODE_WRITE, &write_pipe_fops);
> +	err = -ENFILE;
> +	if (!f)
> +		goto err_inode;
>  	f->f_mapping = inode->i_mapping;
>  
>  	f->f_flags = O_WRONLY;
> -	f->f_op = &write_pipe_fops;
> -	f->f_mode = FMODE_WRITE;
>  	f->f_version = 0;
>  
>  	return f;
> @@ -994,8 +992,7 @@ struct file *create_write_pipe(void)
>   err_inode:
>  	free_pipe_info(inode);
>  	iput(inode);
> - err_file:
> -	put_filp(f);
> + err:
>  	return ERR_PTR(err);
>  }

Does RPC idmapd open a regular pipe too? I thought it only used
rpc_pipefs?

Trond

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