From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E658720B808; Mon, 3 Feb 2025 17:42:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738604557; cv=none; b=lZM81uPd72XH6qHzTMYHI1e+ZT8U/ZOY9jHQedtMFwVDXWcVlp/BuOrrWSBoH3Ftib1bmyyG9VdcBaXyhJD6VPBOsa+mwyUiMZ6sD/KFmvyKgW+ao4USgOmeDZ6qfBcnNNucMWMWYW/yFrVU/kcrbfBvalfpoBbDHYULDHp02s4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738604557; c=relaxed/simple; bh=w8+HSJk4xltd50d3lEfUpCcmRQ0282WxjoW1Xh2epvc=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=QqKjZPI8T2ds4flqcz/m/bZ1nBVSMqqe3adwE5xX+jLrarnqUSkf+YZFaNhs3WrSnJBLkis6sSeyYVjhShZt/hvkZ6OUM8jebTKr3KBw5mwFqsbVUxXOvNr38QGi+lXRsME9ymJZ22RIEh7Q9CaLb4B6Kbl/nX0mugvHeosNjIw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z6Or4dK5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Z6Or4dK5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E1779C4CED2; Mon, 3 Feb 2025 17:42:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738604556; bh=w8+HSJk4xltd50d3lEfUpCcmRQ0282WxjoW1Xh2epvc=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Z6Or4dK5+lTYqhvb5utVEOAIhB/pz1jAoJrGAFBvuQS8REQ1EH5Yq6lKjapycTVD7 GyTkfPWWHx+bN8zeCHHiJM+1QyvzvaSMe8CnyYioTEaeZZsJlVfygMuAS2/kfDBn35 su+Loic4LT7mQj9VvNQvRyItWqe0K+OhrrbeMHrrZ3sQQzl8Rhxa8cdnxxmTtf9QMI kn8Zn7QJZTbw7oWMNNW75D0abDGDmyJTHrebc4wFT8J4q3O8Bog6UgM3v7lOBqmcQ5 ZKQpQie0t3REzuk3rm7F/G6HLyBwtBfwjzMwUnFuRHPLR2aY9BTEC7slLZAP4+QSuI EilmUSZzIZCXQ== Message-ID: <115733465f444bd127c5a0a1db1215980b4607c9.camel@kernel.org> Subject: Re: [PATCH] fuse: add a new "connections" file to show longest waiting reqeust From: Jeff Layton To: Joanne Koong Cc: Miklos Szeredi , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 03 Feb 2025 12:42:34 -0500 In-Reply-To: References: <20250203-fuse-sysfs-v1-1-36faa01f2338@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV 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uxp4CHBDVzAslUi2idy+xpsp47DWPxYFIRP3M8QG/aNW052LaPc0cedYxp8+9eiVUNpxF4SiU4i9J DfX/sn9XcfoVZIxMpCRE750zvJvcCUz9HojsrMQ1NFc7MFT1z3MOW2/RlzPcog7xvR5ENPH19ojRD CHqumUHRry+RF0lH00clzX/W8OrQJZtoBPXv9ahka/Vp7kEulcBJr1cH5Wz/WprhsIM7U9pse1f1g Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2025-02-03 at 09:31 -0800, Joanne Koong wrote: > On Mon, Feb 3, 2025 at 8:37=E2=80=AFAM Jeff Layton w= rote: > >=20 > > Add a new file to the "connections" directory that shows how long (in > > seconds) the oldest fuse_req in the processing hash or pending queue ha= s > > been waiting. > >=20 > > Signed-off-by: Jeff Layton > > --- > > This is based on top of Joanne's work, as it requires the "create_time" > > field in fuse_req. We have some internal detection of hung fuse server > > processes that relies on seeing elevated values in the "waiting" sysfs > > file. The problem with that method is that it can't detect when highly > > serialized workloads on a FUSE mount are hung. This adds another metric > > that we can use to detect when fuse mounts are hung. > > --- > > fs/fuse/control.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++= ++++++++ > > fs/fuse/fuse_i.h | 2 +- > > 2 files changed, 57 insertions(+), 1 deletion(-) > >=20 > > diff --git a/fs/fuse/control.c b/fs/fuse/control.c > > index 2a730d88cc3bdb50ea1f8a3185faad5f05fc6e74..b213db11a2d7d85c4403baa= 61f9f7850fed150a8 100644 > > --- a/fs/fuse/control.c > > +++ b/fs/fuse/control.c > > @@ -180,6 +180,55 @@ static ssize_t fuse_conn_congestion_threshold_writ= e(struct file *file, > > return ret; > > } > >=20 > > +/* Show how long (in s) the oldest request has been waiting */ > > +static ssize_t fuse_conn_oldest_read(struct file *file, char __user *b= uf, > > + size_t len, loff_t *ppos) > > +{ > > + char tmp[32]; > > + size_t size; > > + unsigned long oldest =3D jiffies; > > + > > + if (!*ppos) { > > + struct fuse_conn *fc =3D fuse_ctl_file_conn_get(file); > > + struct fuse_iqueue *fiq =3D &fc->iq; > > + struct fuse_dev *fud; > > + struct fuse_req *req; > > + > > + if (!fc) > > + return 0; > > + > > + spin_lock(&fc->lock); > > + list_for_each_entry(fud, &fc->devices, entry) { > > + struct fuse_pqueue *fpq =3D &fud->pq; > > + int i; > > + > > + spin_lock(&fpq->lock); > > + for (i =3D 0; i < FUSE_PQ_HASH_SIZE; i++) { > > + if (list_empty(&fpq->processing[i])) > > + continue; > > + /* > > + * Only check the first request in the = queue. The > > + * assumption is that the one at the he= ad of the list > > + * will always be the oldest. > > + */ > > + req =3D list_first_entry(&fpq->processi= ng[i], struct fuse_req, list); >=20 > This probably doesn't matter in actuality, but maybe > list_first_entry_or_null() on fpq->processing[i] would be more optimal > here than "list_empty()" and "list_first_entry()" since that'll > minimize the number of READ_ONCE() calls we'd need to do. >=20 I don't think the above will do more than one READ_ONCE, but I agree that list_first_entry_or_null() is more idiomatic. I'll switch to that. > > + if (req->create_time < oldest) > > + oldest =3D req->create_time; > > + } > > + spin_unlock(&fpq->lock); > > + } > > + if (!list_empty(&fiq->pending)) { >=20 > I think we'll need to grab the fiq->lock here first before checking fiq->= pending >=20 Doh! Will fix. > > + req =3D list_first_entry(&fiq->pending, struct = fuse_req, list); > > + if (req->create_time < oldest) > > + oldest =3D req->create_time; > > + } > > + spin_unlock(&fc->lock); > > + fuse_conn_put(fc); > > + } > > + size =3D sprintf(tmp, "%ld\n", (jiffies - oldest)/HZ); >=20 > If there are no requests, I think this will still return a non-zero > value since jiffies is a bit more than what the last "oldest =3D > jiffies" was, which might be confusing. Maybe we should just return 0 > in this case? >=20 >=20 You should only see a non-zero value in that case if it takes more than a second to walk the hash. Possible, but pretty unlikely. > > + return simple_read_from_buffer(buf, len, ppos, tmp, size); > > +} > > + > > static const struct file_operations fuse_ctl_abort_ops =3D { > > .open =3D nonseekable_open, > > .write =3D fuse_conn_abort_write, > > @@ -202,6 +251,11 @@ static const struct file_operations fuse_conn_cong= estion_threshold_ops =3D { > > .write =3D fuse_conn_congestion_threshold_write, > > }; > >=20 > > +static const struct file_operations fuse_ctl_oldest_ops =3D { > > + .open =3D nonseekable_open, > > + .read =3D fuse_conn_oldest_read, > > +}; > > + > > static struct dentry *fuse_ctl_add_dentry(struct dentry *parent, > > struct fuse_conn *fc, > > const char *name, > > @@ -264,6 +318,8 @@ int fuse_ctl_add_conn(struct fuse_conn *fc) > >=20 > > if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400,= 1, > > NULL, &fuse_ctl_waiting_ops) || > > + !fuse_ctl_add_dentry(parent, fc, "oldest", S_IFREG | 0400, = 1, > > + NULL, &fuse_ctl_oldest_ops) || > > !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1= , > > NULL, &fuse_ctl_abort_ops) || > > !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG = | 0600, > > diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h > > index dcc1c327a0574b1fd1adda4b7ca047aa353b6a0a..b46c26bc977ad2d75d10fb3= 06d3ecc4caf2c53bd 100644 > > --- a/fs/fuse/fuse_i.h > > +++ b/fs/fuse/fuse_i.h > > @@ -42,7 +42,7 @@ > > #define FUSE_NAME_MAX 1024 > >=20 > > /** Number of dentries for each connection in the control filesystem *= / > > -#define FUSE_CTL_NUM_DENTRIES 5 > > +#define FUSE_CTL_NUM_DENTRIES 6 > >=20 > > /* Frequency (in seconds) of request timeout checks, if opted into */ > > #define FUSE_TIMEOUT_TIMER_FREQ 15 > >=20 > > --- > > base-commit: 9afd7336f3acbe5678cca3b3bc5baefb51ce9564 > > change-id: 20250203-fuse-sysfs-ce351d105cf0 > >=20 > > Best regards, > > -- > > Jeff Layton > >=20 > >=20 Thanks for the review! --=20 Jeff Layton