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Message-ID: <63df45984a1a7fe5998861abd3210b781662d7f9.camel@web.de> Date: Mon, 09 Dec 2024 13:53:57 +0100 From: Bert Karwatzki <spasswolf@....de> To: Jan Kara <jack@...e.cz> Cc: Josef Bacik <josef@...icpanda.com>, linux-kernel@...r.kernel.org, kernel-team@...com, linux-fsdevel@...r.kernel.org, amir73il@...il.com, brauner@...nel.org, torvalds@...ux-foundation.org, viro@...iv.linux.org.uk, linux-xfs@...r.kernel.org, linux-btrfs@...r.kernel.org, linux-mm@...ck.org, linux-ext4@...r.kernel.org, spasswolf@....de Subject: Re: commit 0790303ec869 leads to cpu stall without CONFIG_FANOTIFY_ACCESS_PERMISSIONS=y Am Montag, dem 09.12.2024 um 13:26 +0100 schrieb Jan Kara: > On Mon 09-12-24 13:11:04, Jan Kara wrote: > > > Then I took a closer look at the function called in the problematic code > > > and noticed that fsnotify_file_area_perm(), is a NOOP when > > > CONFIG_FANOTIFY_ACCESS_PERMISSIONS is not set (which was the case in my > > > .config). This also explains why this was not found before, as > > > distributional .config file have this option enabled. Setting the option > > > to y solves the issue, too > > > > Well, I agree with you on all the points but the real question is, how come > > the test FMODE_FSNOTIFY_HSM(file->f_mode) was true on our kernel when you > > clearly don't run HSM software, even more so with > > CONFIG_FANOTIFY_ACCESS_PERMISSIONS disabled. That's the real cause of this > > problem. Something fishy is going on here... checking... > > > > Ah, because I've botched out file_set_fsnotify_mode() in case > > CONFIG_FANOTIFY_ACCESS_PERMISSIONS is disabled. This should fix the > > problem: > > > > index 1a9ef8f6784d..778a88fcfddc 100644 > > --- a/include/linux/fsnotify.h > > +++ b/include/linux/fsnotify.h > > @@ -215,6 +215,7 @@ static inline int fsnotify_open_perm(struct file *file) > > #else > > static inline void file_set_fsnotify_mode(struct file *file) > > { > > + file->f_mode |= FMODE_NONOTIFY_PERM; > > } > > > > I'm going to test this with CONFIG_FANOTIFY_ACCESS_PERMISSIONS disabled and > > push out a fixed version. Thanks again for the report and analysis! > > So this was not enough, What we need is: > index 1a9ef8f6784d..778a88fcfddc 100644 > --- a/include/linux/fsnotify.h > +++ b/include/linux/fsnotify.h > @@ -215,6 +215,10 @@ static inline int fsnotify_open_perm(struct file *file) > #else > static inline void file_set_fsnotify_mode(struct file *file) > { > + /* Is it a file opened by fanotify? */ > + if (FMODE_FSNOTIFY_NONE(file->f_mode)) > + return; > + file->f_mode |= FMODE_NONOTIFY_PERM; > } > > This passes testing for me so I've pushed it out and the next linux-next > build should have this fix. > > Honza I had "mixed success" with your first fix, out of 4 boots I got 2 hangs, but the new version seems to work fine (4 boots, zero hangs). Bert Karwatzki
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