From: Jan Kara <jack@suse.cz>
To: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Jan Kara <jack@suse.cz>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Amir Goldstein <amir73il@gmail.com>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v3 0/3] fsnotify: fix softlockups iterating over d_subdirs
Date: Tue, 1 Nov 2022 18:51:44 +0100 [thread overview]
Message-ID: <20221101175144.yu3l5qo5gfwfpatt@quack3> (raw)
In-Reply-To: <20221028001016.332663-1-stephen.s.brennan@oracle.com>
Hi Stephen!
On Thu 27-10-22 17:10:13, Stephen Brennan wrote:
> Here is v3 of the patch series. I've taken all of the feedback,
> thanks Amir, Christian, Hilf, et al. Differences are noted in each
> patch.
>
> I caught an obvious and silly dentry reference leak: d_find_any_alias()
> returns a reference, which I never called dput() on. With that change, I
> no longer see the rpc_pipefs issue, but I do think I need more testing
> and thinking through the third patch. Al, I'd love your feedback on that
> one especially.
>
> Thanks,
> Stephen
>
> Stephen Brennan (3):
> fsnotify: Use d_find_any_alias to get dentry associated with inode
> fsnotify: Protect i_fsnotify_mask and child flags with inode rwsem
> fsnotify: allow sleepable child flag update
Thanks for the patches Stephen and I'm sorry for replying somewhat late.
The first patch is a nobrainer. The other two patches ... complicate things
somewhat more complicated than I'd like. I guess I can live with them if we
don't find a better solution but I'd like to discuss a bit more about
alternatives.
So what would happen if we just clear DCACHE_FSNOTIFY_PARENT_WATCHED in
__fsnotify_parent() for the dentry which triggered the event and does not
have watched parent anymore and never bother with full children walk? I
suppose your contention problems will be gone, we'll just pay the price of
dget_parent() + fsnotify_inode_watches_children() for each child that
falsely triggers instead of for only one. Maybe that's not too bad? After
all any event upto this moment triggered this overhead as well...
Am I missing something? AFAIU this would allow us to avoid the games with
the new connector flag etc... We would probably still need to avoid
softlockups when setting the flag DCACHE_FSNOTIFY_PARENT_WATCHED but that
should be much simpler (we could use i_rwsem trick like you do).
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2022-11-01 17:51 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-13 22:27 [RFC] fsnotify: allow sleepable child dentry flag update Stephen Brennan
2022-10-13 23:51 ` Al Viro
2022-11-01 21:47 ` Stephen Brennan
2022-10-14 8:01 ` Amir Goldstein
2022-10-17 7:59 ` Stephen Brennan
2022-10-17 11:44 ` Amir Goldstein
2022-10-17 16:59 ` Stephen Brennan
2022-10-17 17:42 ` Amir Goldstein
2022-10-17 9:09 ` Jan Kara
2022-10-18 4:12 ` [PATCH 0/2] fsnotify: fix softlockups iterating over d_subdirs Stephen Brennan
2022-10-18 4:12 ` [PATCH 1/2] fsnotify: Protect i_fsnotify_mask and child flags with inode rwsem Stephen Brennan
2022-10-18 7:39 ` Amir Goldstein
2022-10-21 0:33 ` Stephen Brennan
2022-10-21 7:22 ` Amir Goldstein
2022-10-18 4:12 ` [PATCH 2/2] fsnotify: allow sleepable child flag update Stephen Brennan
2022-10-18 5:36 ` Amir Goldstein
2022-10-27 7:50 ` kernel test robot
2022-10-27 8:44 ` Yujie Liu
2022-10-27 22:12 ` Stephen Brennan
2022-10-18 8:07 ` [PATCH 0/2] fsnotify: fix softlockups iterating over d_subdirs Amir Goldstein
2022-10-18 23:52 ` Stephen Brennan
2022-10-19 5:33 ` Amir Goldstein
2022-10-27 22:06 ` Stephen Brennan
2022-10-28 8:58 ` Amir Goldstein
2022-10-21 1:03 ` [PATCH v2 0/3] " Stephen Brennan
2022-10-21 1:03 ` [PATCH v2 1/3] fsnotify: Use d_find_any_alias to get dentry associated with inode Stephen Brennan
2022-10-21 9:25 ` Amir Goldstein
2022-10-21 1:03 ` [PATCH v2 2/3] fsnotify: Protect i_fsnotify_mask and child flags with inode rwsem Stephen Brennan
2022-10-21 4:01 ` kernel test robot
2022-10-21 8:22 ` Amir Goldstein
2022-10-21 9:18 ` Amir Goldstein
2022-10-25 18:02 ` Stephen Brennan
2022-10-26 5:41 ` Amir Goldstein
2022-10-21 9:17 ` Christian Brauner
2022-10-21 9:21 ` Amir Goldstein
2022-10-21 1:03 ` [PATCH v2 3/3] fsnotify: allow sleepable child flag update Stephen Brennan
2022-10-28 0:10 ` [PATCH v3 0/3] fsnotify: fix softlockups iterating over d_subdirs Stephen Brennan
2022-10-28 0:10 ` [PATCH v3 1/3] fsnotify: Use d_find_any_alias to get dentry associated with inode Stephen Brennan
2022-11-10 1:12 ` Stephen Brennan
2022-10-28 0:10 ` [PATCH v3 2/3] fsnotify: Protect i_fsnotify_mask and child flags with inode rwsem Stephen Brennan
2022-10-28 9:11 ` Amir Goldstein
2022-11-10 0:03 ` kernel test robot
2022-11-10 1:06 ` Stephen Brennan
2022-10-28 0:10 ` [PATCH v3 3/3] fsnotify: allow sleepable child flag update Stephen Brennan
2022-10-28 9:32 ` Amir Goldstein
2022-11-01 21:25 ` Stephen Brennan
2022-11-01 17:51 ` Jan Kara [this message]
2022-11-01 20:48 ` [PATCH v3 0/3] fsnotify: fix softlockups iterating over d_subdirs Stephen Brennan
2022-11-02 8:55 ` Amir Goldstein
2022-11-10 20:04 ` Stephen Brennan
2022-11-02 17:52 ` Jan Kara
2022-11-04 23:33 ` Stephen Brennan
2022-11-07 11:56 ` Jan Kara
2022-11-11 22:06 ` [PATCH v4 0/5] " Stephen Brennan
2022-11-11 22:06 ` [PATCH v4 1/5] fsnotify: clear PARENT_WATCHED flags lazily Stephen Brennan
2022-11-11 22:06 ` [PATCH v4 2/5] fsnotify: Use d_find_any_alias to get dentry associated with inode Stephen Brennan
2022-11-12 8:53 ` Amir Goldstein
2022-11-11 22:06 ` [PATCH v4 3/5] dnotify: move fsnotify_recalc_mask() outside spinlock Stephen Brennan
2022-11-12 9:06 ` Amir Goldstein
2022-11-11 22:06 ` [PATCH v4 4/5] fsnotify: allow sleepable child flag update Stephen Brennan
2022-11-12 10:00 ` Amir Goldstein
2022-11-15 7:10 ` kernel test robot
2022-11-11 22:06 ` [PATCH v4 5/5] fsnotify: require inode lock held during " Stephen Brennan
2022-11-12 9:42 ` Amir Goldstein
2022-11-11 22:08 ` [PATCH v4 0/5] fsnotify: fix softlockups iterating over d_subdirs Stephen Brennan
2022-11-22 11:50 ` Jan Kara
2022-11-22 14:03 ` Amir Goldstein
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