On Fri, Feb 07, 2014 at 04:16:44PM -0500, J. Bruce Fields wrote:
>
> Nit: I find the conditionals here a little complicated.
>
> Would something like this be clearer? (Untested):
>
> if (inode1 > inode2)
> swap(inode1, inode2);
>
> if (inode1 && !S_ISDIR(inode1->i_mode))
> mutex_lock(&inode1->i_mutex);
>
> if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
> mutex_lock_nested(&inode2->i_mutex, I_MUTEX_NONDIR2);
Yes, much better. And it becomes nicely symmetric with the unlock function.
Thanks,
Miklos
>
> --b.
>
> diff --git a/fs/inode.c b/fs/inode.c
> index 4bcdad3..94e41c8 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -944,24 +944,23 @@ EXPORT_SYMBOL(unlock_new_inode);
>
> /**
> * lock_two_nondirectories - take two i_mutexes on non-directory objects
> + *
> + * Lock any non-NULL argument that is not a directory.
> + * Zero, one or two objects may be locked by this function.
> + *
> * @inode1: first inode to lock
> * @inode2: second inode to lock
> */
> void lock_two_nondirectories(struct inode *inode1, struct inode *inode2)
> {
> - WARN_ON_ONCE(S_ISDIR(inode1->i_mode));
> - if (inode1 == inode2 || !inode2) {
> - mutex_lock(&inode1->i_mutex);
> - return;
> - }
> - WARN_ON_ONCE(S_ISDIR(inode2->i_mode));
> - if (inode1 < inode2) {
> + if (inode1 > inode2)
> + swap(inode1, inode2);
> +
> + if (inode1 && !S_ISDIR(inode1->i_mode))
> mutex_lock(&inode1->i_mutex);
> +
> + if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
> mutex_lock_nested(&inode2->i_mutex, I_MUTEX_NONDIR2);
> - } else {
> - mutex_lock(&inode2->i_mutex);
> - mutex_lock_nested(&inode1->i_mutex, I_MUTEX_NONDIR2);
> - }
> }
> EXPORT_SYMBOL(lock_two_nondirectories);
>
> @@ -972,8 +971,9 @@ EXPORT_SYMBOL(lock_two_nondirectories);
> */
> void unlock_two_nondirectories(struct inode *inode1, struct inode *inode2)
> {
> - mutex_unlock(&inode1->i_mutex);
> - if (inode2 && inode2 != inode1)
> + if (inode1 && !S_ISDIR(inode1->i_mode))
> + mutex_unlock(&inode1->i_mutex);
> + if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
> mutex_unlock(&inode2->i_mutex);
> }
> EXPORT_SYMBOL(unlock_two_nondirectories);
--
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