From patchwork Thu Dec 16 17:20:13 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "J. Bruce Fields" X-Patchwork-Id: 12682257 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43070C433F5 for ; Thu, 16 Dec 2021 17:20:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235896AbhLPRUO (ORCPT ); Thu, 16 Dec 2021 12:20:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232003AbhLPRUO (ORCPT ); Thu, 16 Dec 2021 12:20:14 -0500 Received: from fieldses.org (fieldses.org [IPv6:2600:3c00:e000:2f7::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F819C061574 for ; Thu, 16 Dec 2021 09:20:14 -0800 (PST) Received: by fieldses.org (Postfix, from userid 2815) id 5546D6CDC; Thu, 16 Dec 2021 12:20:13 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.11.0 fieldses.org 5546D6CDC DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fieldses.org; s=default; t=1639675213; bh=YpTeEzxHCHZobKO5Pt4GJ4WQ8La4TjjrObY3ucHLLlQ=; h=Date:To:Cc:Subject:From:From; b=rFpyf+YsZtGtbxnpF29n7DlGrys0fdjDZlWU9UXYZGVXvjfYBXKLfFS8t7ha+Td1n QwOo9KBlew0bheOhVrlszFdds0rNrNOdPSmiD27BauMsQI2MNSLYl8lD1XGRp6vSg+ 2ihgnNAN4ss2zEE0+KOxgJ2mKIfV6PzIZmSdgTn0= Date: Thu, 16 Dec 2021 12:20:13 -0500 To: Chuck Lever Cc: linux-nfs@vger.kernel.org, Vasily Averin , Jeff Layton , "Denis V. Lunev" , Cyrill Gorcunov , Konstantin Khorenko Subject: [PATCH] nfs: block notification on fs with its own ->lock Message-ID: <20211216172013.GA13418@fieldses.org> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) From: bfields@fieldses.org (J. Bruce Fields) Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org From: "J. Bruce Fields" NFSv4.1 supports an optional lock notification feature which notifies the client when a lock comes available. (Normally NFSv4 clients just poll for locks if necessary.) To make that work, we need to request a blocking lock from the filesystem. We turned that off for NFS in f657f8eef3ff "nfs: don't atempt blocking locks on nfs reexports" because it actually blocks the nfsd thread while waiting for the lock. Thanks to Vasily Averin for pointing out that NFS isn't the only filesystem with that problem. Any filesystem that leaves ->lock NULL will use posix_lock_file(), which does the right thing. Simplest is just to assume that any filesystem that defines its own ->lock is not safe to request a blocking lock from. So, this patch mostly reverts f657f8eef3ff and b840be2f00c0, and instead uses a check of ->lock (Vasily's suggestion) to decide whether to support blocking lock notifications on a given filesystem. Also add a little documentation. Perhaps someday we could add back an export flag later to allow filesystems with "good" ->lock methods to support blocking lock notifications. Reported-by: Vasily Averin Signed-off-by: J. Bruce Fields Reviewed-by: Vasily Averin --- fs/lockd/svclock.c | 2 +- fs/nfs/export.c | 2 +- fs/nfsd/nfs4state.c | 18 ++++++++++++------ include/linux/exportfs.h | 2 -- include/linux/lockd/lockd.h | 9 +++++++-- 5 files changed, 21 insertions(+), 12 deletions(-) diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c index e9b85d8fd5fe..98e2f9b32e21 100644 --- a/fs/lockd/svclock.c +++ b/fs/lockd/svclock.c @@ -484,7 +484,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file, (long long)lock->fl.fl_end, wait); - if (inode->i_sb->s_export_op->flags & EXPORT_OP_SYNC_LOCKS) { + if (nlmsvc_file_file(file)->f_op->lock) { async_block = wait; wait = 0; } diff --git a/fs/nfs/export.c b/fs/nfs/export.c index 171c424cb6d5..01596f2d0a1e 100644 --- a/fs/nfs/export.c +++ b/fs/nfs/export.c @@ -158,5 +158,5 @@ const struct export_operations nfs_export_ops = { .fetch_iversion = nfs_fetch_iversion, .flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK| EXPORT_OP_CLOSE_BEFORE_UNLINK|EXPORT_OP_REMOTE_FS| - EXPORT_OP_NOATOMIC_ATTR|EXPORT_OP_SYNC_LOCKS, + EXPORT_OP_NOATOMIC_ATTR, }; diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 1956d377d1a6..3317493d2750 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -6836,7 +6836,6 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, struct nfsd4_blocked_lock *nbl = NULL; struct file_lock *file_lock = NULL; struct file_lock *conflock = NULL; - struct super_block *sb; __be32 status = 0; int lkflg; int err; @@ -6858,7 +6857,6 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, dprintk("NFSD: nfsd4_lock: permission denied!\n"); return status; } - sb = cstate->current_fh.fh_dentry->d_sb; if (lock->lk_is_new) { if (nfsd4_has_session(cstate)) @@ -6910,8 +6908,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, fp = lock_stp->st_stid.sc_file; switch (lock->lk_type) { case NFS4_READW_LT: - if (nfsd4_has_session(cstate) && - !(sb->s_export_op->flags & EXPORT_OP_SYNC_LOCKS)) + if (nfsd4_has_session(cstate)) fl_flags |= FL_SLEEP; fallthrough; case NFS4_READ_LT: @@ -6923,8 +6920,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, fl_type = F_RDLCK; break; case NFS4_WRITEW_LT: - if (nfsd4_has_session(cstate) && - !(sb->s_export_op->flags & EXPORT_OP_SYNC_LOCKS)) + if (nfsd4_has_session(cstate)) fl_flags |= FL_SLEEP; fallthrough; case NFS4_WRITE_LT: @@ -6940,6 +6936,16 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, goto out; } + /* + * Most filesystems with their own ->lock operations will block + * the nfsd thread waiting to acquire the lock. That leads to + * deadlocks (we don't want every nfsd thread tied up waiting + * for file locks), so don't attempt blocking lock notifications + * on those filesystems: + */ + if (nf->nf_file->f_op->lock) + fl_flags &= ~FL_SLEEP; + if (!nf) { status = nfserr_openmode; goto out; diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h index 3260fe714846..fe848901fcc3 100644 --- a/include/linux/exportfs.h +++ b/include/linux/exportfs.h @@ -221,8 +221,6 @@ struct export_operations { #define EXPORT_OP_NOATOMIC_ATTR (0x10) /* Filesystem cannot supply atomic attribute updates */ -#define EXPORT_OP_SYNC_LOCKS (0x20) /* Filesystem can't do - asychronous blocking locks */ unsigned long flags; }; diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h index c4ae6506b8b3..fcef192e5e45 100644 --- a/include/linux/lockd/lockd.h +++ b/include/linux/lockd/lockd.h @@ -303,10 +303,15 @@ void nlmsvc_invalidate_all(void); int nlmsvc_unlock_all_by_sb(struct super_block *sb); int nlmsvc_unlock_all_by_ip(struct sockaddr *server_addr); +static inline struct file *nlmsvc_file_file(struct nlm_file *file) +{ + return file->f_file[O_RDONLY] ? + file->f_file[O_RDONLY] : file->f_file[O_WRONLY]; +} + static inline struct inode *nlmsvc_file_inode(struct nlm_file *file) { - return locks_inode(file->f_file[O_RDONLY] ? - file->f_file[O_RDONLY] : file->f_file[O_WRONLY]); + return locks_inode(nlmsvc_file_file(file)); } static inline int __nlm_privileged_request4(const struct sockaddr *sap)