Messages in this thread | | | Subject | Re: [PATCH 1/3] dcache: add a new enum type for 'dentry_d_lock_class' | From | "yukuai (C)" <> | Date | Fri, 15 Nov 2019 18:08:23 +0800 |
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On 2019/11/15 15:20, Greg KH wrote: > On Fri, Nov 15, 2019 at 04:12:43AM +0000, Al Viro wrote: >> On Fri, Nov 15, 2019 at 11:27:59AM +0800, Greg KH wrote: >>> On Fri, Nov 15, 2019 at 11:27:50AM +0800, yu kuai wrote: >>>> 'dentry_d_lock_class' can be used for spin_lock_nested in case lockdep >>>> confused about two different dentry take the 'd_lock'. >>>> >>>> However, a single 'DENTRY_D_LOCK_NESTED' may not be enough if more than >>>> two dentry are involed. So, and in 'DENTRY_D_LOCK_NESTED_2' >>>> >>>> Signed-off-by: yu kuai <yukuai3@huawei.com> >>>> --- >>>> include/linux/dcache.h | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/include/linux/dcache.h b/include/linux/dcache.h >>>> index 10090f1..8eb84ef 100644 >>>> --- a/include/linux/dcache.h >>>> +++ b/include/linux/dcache.h >>>> @@ -129,7 +129,8 @@ struct dentry { >>>> enum dentry_d_lock_class >>>> { >>>> DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */ >>>> - DENTRY_D_LOCK_NESTED >>>> + DENTRY_D_LOCK_NESTED, >>>> + DENTRY_D_LOCK_NESTED_2 >>> >>> You should document this, as "_2" does not make much sense to anyone >>> only looking at the code :( >>> >>> Or rename it better. >> >> FWIW, I'm not sure it's a good solution. What are the rules for callers >> of that thing, anyway? If it can be called when somebody is creating >> more files in that subtree, we almost certainly will have massive >> problems with the lifetimes of underlying objects... >> >> Could somebody familiar with debugfs explain how is that thing actually >> used and what is required from/promised to its callers? I can try and >> grep through the tree and guess what the rules are, but I've way too >> much on my platter right now and I don't want to get sidetracked into yet >> another tree-wide search and analysis session ;-/ > > Yu wants to use simple_empty() in debugfs_remove_recursive() instead of > manually checking: > if (!list_empty(&child->d_subdirs)) { > > See patch 3 of this series for that change and why they feel it is > needed: > https://lore.kernel.org/lkml/1573788472-87426-4-git-send-email-yukuai3@huawei.com/ > > As to if patch 3 really is needed, I'll leave that up to Yu given that I > thought we had resolved these types of issues already a year or so ago. > > thanks, > > greg k-h > > . > The main purpose of this patchset is to fix the infinite loop in debugfs_remove_recursive. Steven point out that simple replace list_empty with simple_empty will cause a splat with lockdep enabled. We try to fix it with the first two patch, do you think it's appropriate?
Thanks, Yu Kuai
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