On Wed, Sep 21, 2011 at 10:58:13AM -0400, J. Bruce Fields wrote:
> In setlease, we use i_writecount to decide whether we can give out a
> read lease.
>
> In open, we break leases before incrementing i_writecount.
>
> There is therefore a window between the break lease and the i_writecount
> increment when setlease could add a new read lease.
>
> This would leave us with a simultaneous write open and read lease, which
> shouldn't happen.
And maybe someone that knows the open code better than me could confirm
whether it's reasonable to move the break_lease() call to __dentry_open
like this....
--b.
>
> Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
> ---
> fs/namei.c | 5 +----
> fs/open.c | 4 ++++
> 2 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index 2826db3..6ff59e5 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2044,10 +2044,7 @@ static int may_open(struct path *path, int acc_mode, int flag)
> if (flag & O_NOATIME && !inode_owner_or_capable(inode))
> return -EPERM;
>
> - /*
> - * Ensure there are no outstanding leases on the file.
> - */
> - return break_lease(inode, flag);
> + return 0;
> }
>
> static int handle_truncate(struct file *filp)
> diff --git a/fs/open.c b/fs/open.c
> index f711921..22c41b5 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -685,6 +685,10 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
> if (error)
> goto cleanup_all;
>
> + error = break_lease(inode, f->f_flags);
> + if (error)
> + goto cleanup_all;
> +
> if (!open && f->f_op)
> open = f->f_op->open;
> if (open) {
> --
> 1.7.4.1
>
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