From: Al Viro <viro@ftp.linux.org.uk>
To: Dave Hansen <haveblue@us.ibm.com>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
herbert@13thfloor.at
Subject: Re: [RFC][PATCH 03/20] Add vfsmount writer count
Date: Sun, 18 Jun 2006 19:33:20 +0100 [thread overview]
Message-ID: <20060618183320.GZ27946@ftp.linux.org.uk> (raw)
In-Reply-To: <20060616231215.09D54036@localhost.localdomain>
On Fri, Jun 16, 2006 at 04:12:15PM -0700, Dave Hansen wrote:
> +/*
> + * Must be called under write lock on mnt->mnt_sb->s_umount,
> + * this prevents concurrent decrements which could make the
> + * value -1, and test in mnt_want_write() wrongly succeed
> + */
> +static inline int mnt_make_readonly(struct vfsmount *mnt)
> +{
> + if (!atomic_dec_and_test(&mnt->mnt_writers)) {
> + atomic_inc(&mnt->mnt_writers);
> + return -EBUSY;
> + }
> + return 0;
> +}
Check in faccessat() could get screwed by that, if you just lose the
race with final writer going away. Then mnt_make_readonly() will
fail (as it should) and access(2) give -EROFS.
next prev parent reply other threads:[~2006-06-18 18:33 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-06-16 23:12 [RFC][PATCH 00/20] Mount writer count and read-only bind mounts (v2) Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 01/20] prepare for write access checks: collapse if() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 02/20] r/o bind mount prepwork: move open_namei()'s vfs_create() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 03/20] Add vfsmount writer count Dave Hansen
2006-06-18 18:33 ` Al Viro [this message]
2006-06-19 17:02 ` Dave Hansen
2006-06-20 21:20 ` Al Viro
2006-06-22 17:01 ` Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 04/20] elevate mnt writers for callers of vfs_mkdir() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 05/20] elevate write count during entire ncp_ioctl() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 06/20] sys_symlinkat() elevate write count around vfs_symlink() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 07/20] elevate mount count for extended attributes Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 08/20] sys_linkat(): elevate write count around vfs_link() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 09/20] mount_is_safe(): add comment Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 11/20] elevate write count over calls to vfs_rename() Dave Hansen
2006-06-18 18:23 ` Al Viro
2006-06-19 17:18 ` Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 10/20] unix_find_other() elevate write count for touch_atime() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 12/20] tricky: elevate write count files are open()ed Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 13/20] elevate writer count for do_sys_truncate() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 14/20] elevate write count for do_utimes() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 15/20] elevate write count for do_sys_utime() and touch_atime() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 16/20] sys_mknodat(): elevate write count for vfs_mknod/create() Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 17/20] elevate mnt writers for vfs_unlink() callers Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 19/20] elevate writer count for custom 'struct file' Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 18/20] do_rmdir(): elevate write count Dave Hansen
2006-06-16 23:12 ` [RFC][PATCH 20/20] honor r/w changes at do_remount() time Dave Hansen
2006-06-18 18:36 ` Al Viro
2006-06-19 16:45 ` Dave Hansen
2006-06-16 23:29 ` [RFC][PATCH 00/20] Mount writer count and read-only bind mounts (v2) Grzegorz Kulewski
2006-06-16 23:41 ` Dave Hansen
2006-06-17 0:10 ` Grzegorz Kulewski
2006-06-17 3:35 ` Herbert Poetzl
2006-06-17 9:36 ` Jan Engelhardt
2006-06-17 13:29 ` Herbert Poetzl
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