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Mon, 9 Dec 2024 12:11:08 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 8fiVN1zeVmfwUwAAD6G6ig (envelope-from ); Mon, 09 Dec 2024 12:11:08 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 71156A0B0C; Mon, 9 Dec 2024 13:11:04 +0100 (CET) Date: Mon, 9 Dec 2024 13:11:04 +0100 From: Jan Kara To: Bert Karwatzki Cc: Josef Bacik , linux-kernel@vger.kernel.org, Jan Kara , kernel-team@fb.com, linux-fsdevel@vger.kernel.org, amir73il@gmail.com, brauner@kernel.org, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org Subject: Re: commit 0790303ec869 leads to cpu stall without CONFIG_FANOTIFY_ACCESS_PERMISSIONS=y Message-ID: <20241209121104.j6zttbqod3sh3qhr@quack3> References: <20241208152520.3559-1-spasswolf@web.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241208152520.3559-1-spasswolf@web.de> X-Rspamd-Action: no action X-Rspamd-Queue-Id: 26A4B12001C X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: rr13cffscy5zapo7u9hc3r4tbyqg8du7 X-HE-Tag: 1733746241-463287 X-HE-Meta: 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 QYxEKJmv T9/zwPCIib8ytmMksgYZRFMPfLyzXlxSqkUmUcafrhlb0feQXF6FO4SmQGPmLmtEBNNZRNA404nDcE+4zaM/VtucqXl4KJSJbXAY6tPR+S2te6xu/EI9bX1vWemQnJuFwPJzXOmlL/FSc+lIu2tbhBQd3NllAUOKqIPBqg7RbT7FSNYYhYYaNKKq55x+ijvGpsjuqfAcrPCHILZ3MKOu2Xzfz5BYcdnG63fomRF/uRtmVCjTk4FBfJcreGUg9X6vuFfXJ9Ffxhvq7/QaAIPRPQYlvqXADsSUQwkCOG+YwMHArzx9f8t8UDr6MLaozIMQyIxniQokXCeLTWKd6WRm1vSalzNbf7ZorusjsBw77bHAs0jiYh659iJLOGiIDcoO9tModUu3OmtLWic4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello! On Sun 08-12-24 16:25:19, Bert Karwatzki wrote: > Since linux-next-20241206 booting my debian unstable system hangs before starting gdm. > After some time these messages appear in /var/log/kern.log: Thanks for report! > I bisected this between linux-6.13-rc1 and linux-20241206 and found this as > offending commit: > 0790303ec869 ("fsnotify: generate pre-content permission event on page fault") > > I also noticed that only a part of the commit causes the issue, and reverting > that part solves it in linux-next-20241206: > > commit 6207000b72058b45bb03f0975fbbbcd9dae06238 > Author: Bert Karwatzki > Date: Sun Dec 8 01:51:59 2024 +0100 > > mm: filemap: partially revert commit 790303ec869 > > Reverting this part of commit 790303ec869 is enough > to fix the issue. > > Signed-off-by: Bert Karwatzki > > diff --git a/mm/filemap.c b/mm/filemap.c > index 23e001f5cd0f..9bf2fc833f3c 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -3419,37 +3419,6 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) > * or because readahead was otherwise unable to retrieve it. > */ > if (unlikely(!folio_test_uptodate(folio))) { > - /* > - * If this is a precontent file we have can now emit an event to > - * try and populate the folio. > - */ > - if (!(vmf->flags & FAULT_FLAG_TRIED) && > - unlikely(FMODE_FSNOTIFY_HSM(file->f_mode))) { > - loff_t pos = folio_pos(folio); > - size_t count = folio_size(folio); > - > - /* We're NOWAIT, we have to retry. */ > - if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) { > - folio_unlock(folio); > - goto out_retry; > - } > - > - if (mapping_locked) > - filemap_invalidate_unlock_shared(mapping); > - mapping_locked = false; > - > - folio_unlock(folio); > - fpin = maybe_unlock_mmap_for_io(vmf, fpin); > - if (!fpin) > - goto out_retry; > - > - error = fsnotify_file_area_perm(fpin, MAY_ACCESS, &pos, > - count); > - if (error) > - ret = VM_FAULT_SIGBUS; > - goto out_retry; > - } > - > /* > * If the invalidate lock is not held, the folio was in cache > * and uptodate and now it is not. Strange but possible since we > > > 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! Honza -- Jan Kara SUSE Labs, CR