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 0BF2B2727FA; Wed, 3 Dec 2025 19:44:18 +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=1764791059; cv=none; b=pouqAHHV98UCOUfu8m8Mqt2UHDK/BaMLoHkihkz3IvZcXtFfb4gmMhYSoChKM8Ouu8n2Akejd7gffOiuCLtI/RQjxX8GRYxPslkQmJshzDWzT3LxBTy8L1GXIOt7NyEcWT2hNJICIPgOnGv1btKoRJc/AvS/M3hpkXlu+J0vbeo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764791059; c=relaxed/simple; bh=/SPXWYmqqIt+3J1y1r3JwQXuOAOSjdiHYJVmFwPhB5E=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=bkEEgq7dYrka+HXuQQZ4V1f8HZqau9/Fp5wFij25zsZ8ZZH3D5sbJooPo1okaEUP87N6Yj5QAKT8pwD8+XsU2/+LudC4W78itxQfaTcp47EVfr6jGtD2hpctzHYal5/xWozOski0K7mF3ikI0DDC1hLSH0/umOrnM9+7CQz5rbQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EJtdjDe+; 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="EJtdjDe+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0E0D7C4CEF5; Wed, 3 Dec 2025 19:44:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764791058; bh=/SPXWYmqqIt+3J1y1r3JwQXuOAOSjdiHYJVmFwPhB5E=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=EJtdjDe+gZflefhc/DRS3AJfbNGy6wGTCIKW2GTtN4ab9xhBewYv2aTSFRF67JtXK 8tiA0tTuR0Hks5+vX74tQwfzZ5jrgeAXPZIrZicvrAplXf4zFlEUc9KkOVAWTLU9xx C+wI08LzSzFy13fKRDEFb+L+8cCVt2QKjcgMasOC/m8puN2iF3Lxb7D3xmVHTI8tYC jcbNaKZIJXH3F1M+wKbBTO7DPrk+7bnM0fmzb/SFEqsn3DWXDfmEYSlqd0O8zjz18p fIL3xPNKypOnfWJbZ+1+b27RjFDlrawEJmwyG3pmKZO1qIOVThEVet3pKOep9RZGp5 kfouQV/tDR38A== Message-ID: <82320f68300e0cbcbc0545944191a832b946cf80.camel@kernel.org> Subject: Re: [PATCH 2/2] filelock: allow lease_managers to dictate what qualifies as a conflict From: Jeff Layton To: Chuck Lever , Alexander Viro , Christian Brauner , Jan Kara , Chuck Lever , Alexander Aring , "Matthew Wilcox (Oracle)" , Jonathan Corbet , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-nfs@vger.kernel.org Date: Wed, 03 Dec 2025 14:44:15 -0500 In-Reply-To: References: <20251201-dir-deleg-ro-v1-0-2e32cf2df9b7@kernel.org> <20251201-dir-deleg-ro-v1-2-2e32cf2df9b7@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw 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Evolution 3.58.2 (3.58.2-1.fc43) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2025-12-03 at 14:00 -0500, Chuck Lever wrote: >=20 > On Mon, Dec 1, 2025, at 10:08 AM, Jeff Layton wrote: > > Requesting a delegation on a file from the userland fcntl() interface > > currently succeeds when there are conflicting opens present. > >=20 > > This is because the lease handling code ignores conflicting opens for > > FL_LAYOUT and FL_DELEG leases. This was a hack put in place long ago, > > because nfsd already checks for conflicts in its own way. The kernel > > needs to perform this check for userland delegations the same way it is > > done for leases, however. > >=20 > > Make this dependent on the lease_manager by adding a new > > ->lm_open_conflict() lease_manager operation and have > > generic_add_lease() call that instead of check_conflicting_open(). > > Morph check_conflicting_open() into a ->lm_open_conflict() op that is > > only called for userland leases/delegations. Set the > > ->lm_open_conflict() operations for nfsd to trivial functions that > > always return 0. > >=20 > > Signed-off-by: Jeff Layton > > --- > > Documentation/filesystems/locking.rst | 1 + > > fs/locks.c | 90 ++++++++++++++++-----------= -------- > > fs/nfsd/nfs4layouts.c | 11 ++++- > > fs/nfsd/nfs4state.c | 7 +++ > > include/linux/filelock.h | 1 + > > 5 files changed, 60 insertions(+), 50 deletions(-) > >=20 > > diff --git a/Documentation/filesystems/locking.rst=20 > > b/Documentation/filesystems/locking.rst > > index=20 > > 77704fde98457423beae7ff00525a7383e37132b..29d453a2201bcafa03b26b706e4c6= 8eaf5683829=20 > > 100644 > > --- a/Documentation/filesystems/locking.rst > > +++ b/Documentation/filesystems/locking.rst > > @@ -416,6 +416,7 @@ lm_change yes no no > > lm_breaker_owns_lease: yes no no > > lm_lock_expirable yes no no > > lm_expire_lock no no yes > > +lm_open_conflict yes no no > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D > >=20 > > buffer_head > > diff --git a/fs/locks.c b/fs/locks.c > > index=20 > > e974f8e180fe48682a271af4f143e6bc8e9c4d3b..a58c51c2cdd0cc4496538ed54d063= cd523264128=20 > > 100644 > > --- a/fs/locks.c > > +++ b/fs/locks.c > > @@ -585,10 +585,50 @@ lease_setup(struct file_lease *fl, void **priv) > > __f_setown(filp, task_pid(current), PIDTYPE_TGID, 0); > > } > >=20 > > +/** > > + * lease_open_conflict - see if the given file points to an inode that= has > > + * an existing open that would conflict with the > > + * desired lease. > > + * @filp: file to check > > + * @arg: type of lease that we're trying to acquire > > + * > > + * Check to see if there's an existing open fd on this file that would > > + * conflict with the lease we're trying to set. > > + */ > > +static int > > +lease_open_conflict(struct file *filp, const int arg) > > +{ > > + struct inode *inode =3D file_inode(filp); > > + int self_wcount =3D 0, self_rcount =3D 0; > > + > > + if (arg =3D=3D F_RDLCK) > > + return inode_is_open_for_write(inode) ? -EAGAIN : 0; > > + else if (arg !=3D F_WRLCK) > > + return 0; > > + > > + /* > > + * Make sure that only read/write count is from lease requestor. > > + * Note that this will result in denying write leases when i_writecou= nt > > + * is negative, which is what we want. (We shouldn't grant write lea= ses > > + * on files open for execution.) > > + */ > > + if (filp->f_mode & FMODE_WRITE) > > + self_wcount =3D 1; > > + else if (filp->f_mode & FMODE_READ) > > + self_rcount =3D 1; > > + > > + if (atomic_read(&inode->i_writecount) !=3D self_wcount || > > + atomic_read(&inode->i_readcount) !=3D self_rcount) > > + return -EAGAIN; > > + > > + return 0; > > +} > > + > > static const struct lease_manager_operations lease_manager_ops =3D { > > .lm_break =3D lease_break_callback, > > .lm_change =3D lease_modify, > > .lm_setup =3D lease_setup, > > + .lm_open_conflict =3D lease_open_conflict, > > }; > >=20 > > /* > > @@ -1753,52 +1793,6 @@ int fcntl_getdeleg(struct file *filp, struct=20 > > delegation *deleg) > > return 0; > > } > >=20 > > -/** > > - * check_conflicting_open - see if the given file points to an inode= =20 > > that has > > - * an existing open that would conflict with the > > - * desired lease. > > - * @filp: file to check > > - * @arg: type of lease that we're trying to acquire > > - * @flags: current lock flags > > - * > > - * Check to see if there's an existing open fd on this file that would > > - * conflict with the lease we're trying to set. > > - */ > > -static int > > -check_conflicting_open(struct file *filp, const int arg, int flags) > > -{ > > - struct inode *inode =3D file_inode(filp); > > - int self_wcount =3D 0, self_rcount =3D 0; > > - > > - if (flags & FL_LAYOUT) > > - return 0; > > - if (flags & FL_DELEG) > > - /* We leave these checks to the caller */ > > - return 0; > > - > > - if (arg =3D=3D F_RDLCK) > > - return inode_is_open_for_write(inode) ? -EAGAIN : 0; > > - else if (arg !=3D F_WRLCK) > > - return 0; > > - > > - /* > > - * Make sure that only read/write count is from lease requestor. > > - * Note that this will result in denying write leases when=20 > > i_writecount > > - * is negative, which is what we want. (We shouldn't grant write=20 > > leases > > - * on files open for execution.) > > - */ > > - if (filp->f_mode & FMODE_WRITE) > > - self_wcount =3D 1; > > - else if (filp->f_mode & FMODE_READ) > > - self_rcount =3D 1; > > - > > - if (atomic_read(&inode->i_writecount) !=3D self_wcount || > > - atomic_read(&inode->i_readcount) !=3D self_rcount) > > - return -EAGAIN; > > - > > - return 0; > > -} > > - > > static int > > generic_add_lease(struct file *filp, int arg, struct file_lease **flp,= =20 > > void **priv) > > { > > @@ -1835,7 +1829,7 @@ generic_add_lease(struct file *filp, int arg,=20 > > struct file_lease **flp, void **pr > > percpu_down_read(&file_rwsem); > > spin_lock(&ctx->flc_lock); > > time_out_leases(inode, &dispose); > > - error =3D check_conflicting_open(filp, arg, lease->c.flc_flags); > > + error =3D lease->fl_lmops->lm_open_conflict(filp, arg); > > if (error) > > goto out; > >=20 > > @@ -1892,7 +1886,7 @@ generic_add_lease(struct file *filp, int arg,=20 > > struct file_lease **flp, void **pr > > * precedes these checks. > > */ > > smp_mb(); > > - error =3D check_conflicting_open(filp, arg, lease->c.flc_flags); > > + error =3D lease->fl_lmops->lm_open_conflict(filp, arg); > > if (error) { > > locks_unlink_lock_ctx(&lease->c); > > goto out; > > diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c > > index=20 > > 683bd1130afe298f9df774684192c89f68102b72..ca7ec7a022bd5c12fad60ff9e5114= 5d9cca55527=20 > > 100644 > > --- a/fs/nfsd/nfs4layouts.c > > +++ b/fs/nfsd/nfs4layouts.c > > @@ -764,9 +764,16 @@ nfsd4_layout_lm_change(struct file_lease *onlist,= =20 > > int arg, > > return lease_modify(onlist, arg, dispose); > > } > >=20 > > +static int > > +nfsd4_layout_lm_open_conflict(struct file *filp, int arg) > > +{ > > + return 0; > > +} > > + >=20 > The usual idiom for no-op callbacks is to make them optional. > Then generic_add_lease would check if the ->lm_open_conflict > callback is defined first and skip the call if it's not. >=20 That is what we usually do, but there are only a few lease managers and they all need to define this op, so it saves us a trivial pointer check to not do that. I can switch to doing it that way if you have a preference. > If that doesn't make sense to do, and these NFSD-specific > functions need to remain, then our usual practice is to add > a kdoc comment for both of the new functions that looks like > the one you added above for lease_open_conflict(). >=20 Even for one that just returns 0? Ok >=20 > Otherwise, I'm comfortable that this change fits in with the > deadlock prevention patches we are considering for NFSD. >=20 > Reviewed-by: Chuck Lever >=20 > For both 1/2 and 2/2. >=20 Thanks! >=20 > > static const struct lease_manager_operations nfsd4_layouts_lm_ops =3D = { > > - .lm_break =3D nfsd4_layout_lm_break, > > - .lm_change =3D nfsd4_layout_lm_change, > > + .lm_break =3D nfsd4_layout_lm_break, > > + .lm_change =3D nfsd4_layout_lm_change, > > + .lm_open_conflict =3D nfsd4_layout_lm_open_conflict, > > }; > >=20 > > int > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > > index=20 > > 8f8c9385101e15b64883eabec71775f26b14f890..669fabb095407e61525e5b71268cf= 1f06fc09877=20 > > 100644 > > --- a/fs/nfsd/nfs4state.c > > +++ b/fs/nfsd/nfs4state.c > > @@ -5543,10 +5543,17 @@ nfsd_change_deleg_cb(struct file_lease *onlist,= =20 > > int arg, > > return -EAGAIN; > > } > >=20 > > +static int > > +nfsd4_deleg_lm_open_conflict(struct file *filp, int arg) > > +{ > > + return 0; > > +} > > + > > static const struct lease_manager_operations nfsd_lease_mng_ops =3D { > > .lm_breaker_owns_lease =3D nfsd_breaker_owns_lease, > > .lm_break =3D nfsd_break_deleg_cb, > > .lm_change =3D nfsd_change_deleg_cb, > > + .lm_open_conflict =3D nfsd4_deleg_lm_open_conflict, > > }; > >=20 > > static __be32 nfsd4_check_seqid(struct nfsd4_compound_state *cstate,= =20 > > struct nfs4_stateowner *so, u32 seqid) > > diff --git a/include/linux/filelock.h b/include/linux/filelock.h > > index=20 > > 54b824c05299261e6bd6acc4175cb277ea35b35d..2f5e5588ee0733c200103801d0d2b= a19bebbf9af=20 > > 100644 > > --- a/include/linux/filelock.h > > +++ b/include/linux/filelock.h > > @@ -49,6 +49,7 @@ struct lease_manager_operations { > > int (*lm_change)(struct file_lease *, int, struct list_head *); > > void (*lm_setup)(struct file_lease *, void **); > > bool (*lm_breaker_owns_lease)(struct file_lease *); > > + int (*lm_open_conflict)(struct file *, int); > > }; > >=20 > > struct lock_manager { > >=20 > > --=20 > > 2.52.0 --=20 Jeff Layton