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From: Andrew Morton <akpm@linux-foundation.org>
To: Dave Hansen <hansendc@us.ibm.com>
Cc: linux-kernel@vger.kernel.org, hch@infradead.org
Subject: Re: [PATCH 12/22] elevate write count files are open()ed
Date: Mon, 12 Feb 2007 21:11:48 -0800	[thread overview]
Message-ID: <20070212211148.c9069c97.akpm@linux-foundation.org> (raw)
In-Reply-To: <20070209225337.C8EC7257@localhost.localdomain>

On Fri, 09 Feb 2007 14:53:37 -0800 Dave Hansen <hansendc@us.ibm.com> wrote:

> diff -puN fs/file_table.c~14-24-tricky-elevate-write-count-files-are-open-ed fs/file_table.c
> --- lxc/fs/file_table.c~14-24-tricky-elevate-write-count-files-are-open-ed	2007-02-09 14:26:54.000000000 -0800
> +++ lxc-dave/fs/file_table.c	2007-02-09 14:26:54.000000000 -0800
> @@ -209,8 +209,11 @@ void fastcall __fput(struct file *file)
>  	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
>  		cdev_put(inode->i_cdev);
>  	fops_put(file->f_op);
> -	if (file->f_mode & FMODE_WRITE)
> +	if (file->f_mode & FMODE_WRITE) {
>  		put_write_access(inode);
> +		if(!special_file(inode->i_mode))
> +			mnt_drop_write(mnt);
> +	}
>  	put_pid(file->f_owner.pid);
>  	put_user_ns(file->f_owner.user_ns);
>  	file_kill(file);
> diff -puN fs/namei.c~14-24-tricky-elevate-write-count-files-are-open-ed fs/namei.c
> --- lxc/fs/namei.c~14-24-tricky-elevate-write-count-files-are-open-ed	2007-02-09 14:26:54.000000000 -0800
> +++ lxc-dave/fs/namei.c	2007-02-09 14:26:54.000000000 -0800
> @@ -1548,8 +1548,17 @@ int may_open(struct nameidata *nd, int a
>  			return -EACCES;
>  
>  		flag &= ~O_TRUNC;
> -	} else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
> -		return -EROFS;
> +	} else if (flag & FMODE_WRITE) {
> +		/*
> +		 * effectively: !special_file()
> +		 * balanced by __fput()
> +		 */
> +		error = mnt_want_write(nd->mnt);
> +		if (error)
> +			return error;
> +		if (IS_RDONLY(inode))
> +			return -EROFS;
> +	}

yipes.  A new mount-wide spin_lock/unlock for each for-writing open() and close().
Can we have a microbenchmark on this please?

Are you sure that fget_light() and fput_light() don't accidentally bypass this
new logic?

  reply	other threads:[~2007-02-13  5:13 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-09 22:53 [PATCH 01/22] filesystem helpers for custom 'struct file's Dave Hansen
2007-02-09 22:53 ` [PATCH 02/22] r/o bind mounts: add vfsmount writer counts Dave Hansen
2007-02-09 23:41   ` Eric Dumazet
2007-02-10  0:10     ` Dave Hansen
2007-02-09 22:53 ` [PATCH 03/22] record when sb_writer_count elevated for inode Dave Hansen
2007-02-09 22:53 ` [PATCH 04/22] elevate writer count for chown and friends Dave Hansen
2007-02-09 22:53 ` [PATCH 05/22] elevate mnt writers for callers of vfs_mkdir() Dave Hansen
2007-02-09 22:53 ` [PATCH 06/22] elevate write count during entire ncp_ioctl() Dave Hansen
2007-02-09 22:53 ` [PATCH 07/22] elevate write count for link and symlink calls Dave Hansen
2007-02-09 22:53 ` [PATCH 08/22] elevate mount count for extended attributes Dave Hansen
2007-02-09 22:53 ` [PATCH 09/22] mount_is_safe(): add comment Dave Hansen
2007-02-09 22:53 ` [PATCH 10/22] unix_find_other() elevate write count for touch_atime() Dave Hansen
2007-02-09 22:53 ` [PATCH 12/22] elevate write count files are open()ed Dave Hansen
2007-02-13  5:11   ` Andrew Morton [this message]
2007-02-13 16:58     ` Dave Hansen
2007-02-13 17:58       ` Andrew Morton
2007-02-14  0:17         ` Dave Hansen
2007-02-09 22:53 ` [PATCH 11/22] elevate write count over calls to vfs_rename() Dave Hansen
2007-02-09 22:53 ` [PATCH 13/22] elevate writer count for do_sys_truncate() Dave Hansen
2007-02-09 22:53 ` [PATCH 14/22] elevate write count for do_utimes() Dave Hansen
2007-02-09 22:53 ` [PATCH 15/22] elevate write count for do_sys_utime() and touch_atime() Dave Hansen
2007-02-09 22:53 ` [PATCH 16/22] sys_mknodat(): elevate write count for vfs_mknod/create() Dave Hansen
2007-02-09 22:53 ` [PATCH 17/22] elevate mnt writers for vfs_unlink() callers Dave Hansen
2007-02-09 22:53 ` [PATCH 18/22] do_rmdir(): elevate write count Dave Hansen
2007-02-09 22:53 ` [PATCH 19/22] elevate writer count for custom struct_file Dave Hansen
2007-02-09 22:53 ` [PATCH 20/22] [PATCH] gfs: check nlink count Dave Hansen
2007-02-09 22:53 ` [PATCH 21/22] honor r/w changes at do_remount() time Dave Hansen
2007-02-09 23:22   ` Andrew Morton
2007-02-10  0:00     ` Dave Hansen
2007-02-10  0:29     ` Anton Altaparmakov
2007-02-10  9:54     ` Jan Engelhardt
2007-02-09 22:53 ` [PATCH 22/22] kill open files traverse on remount ro Dave Hansen
2007-02-09 23:18 ` [PATCH 01/22] filesystem helpers for custom 'struct file's Andrew Morton

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