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[2605:2700:0:2:a800:ff:fee1:602f]) by smtp.gmail.com with ESMTPSA id j11sm146826pfe.26.2020.12.02.06.59.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Dec 2020 06:59:03 -0800 (PST) From: Fox Chen To: gregkh@linuxfoundation.org, tj@kernel.org Cc: Fox Chen , linux-kernel@vger.kernel.org Subject: [PATCH 1/2] kernfs: replace the mutex in kernfs_iop_permission with a rwlock Date: Wed, 2 Dec 2020 22:58:36 +0800 Message-Id: <20201202145837.48040-2-foxhlchen@gmail.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201202145837.48040-1-foxhlchen@gmail.com> References: <20201202145837.48040-1-foxhlchen@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A big global mutex in kernfs_iop_permission will significanly drag system performance when processes concurrently open files on kernfs in Big machines(with >= 16 cpu cores). This patch replace the big mutex with a rwlock specifically for protecting kernfs_node->iattribute. So that kernfs_iop_permission can perform concurrently. Signed-off-by: Fox Chen --- fs/kernfs/inode.c | 16 ++++++++-------- include/linux/kernfs.h | 1 + 2 files changed, 9 insertions(+), 8 deletions(-) diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index fc2469a20fed..c8c2ea669e6d 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -106,9 +106,9 @@ int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr) { int ret; - mutex_lock(&kernfs_mutex); + write_lock(&kn->iattr_rwlock); ret = __kernfs_setattr(kn, iattr); - mutex_unlock(&kernfs_mutex); + write_unlock(&kn->iattr_rwlock); return ret; } @@ -121,7 +121,7 @@ int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr) if (!kn) return -EINVAL; - mutex_lock(&kernfs_mutex); + write_lock(&kn->iattr_rwlock); error = setattr_prepare(dentry, iattr); if (error) goto out; @@ -134,7 +134,7 @@ int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr) setattr_copy(inode, iattr); out: - mutex_unlock(&kernfs_mutex); + write_unlock(&kn->iattr_rwlock); return error; } @@ -189,9 +189,9 @@ int kernfs_iop_getattr(const struct path *path, struct kstat *stat, struct inode *inode = d_inode(path->dentry); struct kernfs_node *kn = inode->i_private; - mutex_lock(&kernfs_mutex); + read_lock(&kn->iattr_rwlock); kernfs_refresh_inode(kn, inode); - mutex_unlock(&kernfs_mutex); + read_unlock(&kn->iattr_rwlock); generic_fillattr(inode, stat); return 0; @@ -281,9 +281,9 @@ int kernfs_iop_permission(struct inode *inode, int mask) kn = inode->i_private; - mutex_lock(&kernfs_mutex); + read_lock(&kn->iattr_rwlock); kernfs_refresh_inode(kn, inode); - mutex_unlock(&kernfs_mutex); + read_unlock(&kn->iattr_rwlock); return generic_permission(inode, mask); } diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 89f6a4214a70..545cdb39b34b 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -156,6 +156,7 @@ struct kernfs_node { unsigned short flags; umode_t mode; struct kernfs_iattrs *iattr; + rwlock_t iattr_rwlock; }; /* -- 2.29.2