From:   Imran Khan <imran.f.khan@oracle.com>
To:     tj@kernel.org, gregkh@linuxfoundation.org
Cc:     linux-kernel@vger.kernel.org
Subject: [PATCH v3 0/2] kernfs: use hashed mutex and spinlock in place of global ones
Date:   Thu, 13 Jan 2022 21:42:57 +1100
Message-Id: <20220113104259.1584491-1-imran.f.khan@oracle.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?cutr7YL5hyVKZVCzkrUzPsL/Ne1QAIOiq4rIQ1Frq5ZlFOXV74M3AfpLgnba?=
 =?us-ascii?Q?KzKJkCbV2pCuBm7NJoG/Qu0/RHVIzQWjZ6JAVVN6npDVFAglWV8mtR2oILmQ?=
 =?us-ascii?Q?QHyjopiY7rY8aGLjeXYS3CTW0Iehl+02U5pbbI63UFb5HoWhnDizeu3nm7nE?=
 =?us-ascii?Q?g3bysx2lBiHOhkzL0gJ+WABC2M2LTi+FyQd1Tb48lqGuv2tbva+7/ZrqstpE?=
 =?us-ascii?Q?DQhpcZ5sqRKlF1Q336ST8WJ4GI2+LjuNd4GQtl2lqTpC+QUXz+l8ZfQH2klN?=
 =?us-ascii?Q?SfdediaAK8ZpodoecQQ6RP2iR6QNobeAJ0ZSltA3P3aycZJTdAoOvVog5jJD?=
 =?us-ascii?Q?/35QY+p6jSwSgiyYU6NaUDKraAtPwOVpl35eJWfyVGFf4fAxaXFaUW70a8tB?=
 =?us-ascii?Q?OVUbCUg8cGeuFnHyl+wsUWn/WRlkGxfusagqMI/Bb8XyH+O1rZtdXLh0QwjI?=
 =?us-ascii?Q?3pHRfEqhCmCQ6E7oUfDmqT0lIupOecv8/oSVp7qSn5hQ9jYarF1/diQoWqg8?=
 =?us-ascii?Q?ZG1NAzkI7RxigKyLZP4tC9vkioYFP+Vuv4fL0Uoyq9bgq7UKv1xhWb37ioQ8?=
 =?us-ascii?Q?zNPWfoxQhmF7y/FLy4ICmqZI/KGkutE8olS11nszxt/nQaDaVXuBAEffLb/2?=
 =?us-ascii?Q?Y2pLc5HX6M8bh/8SbSEMGWWkb230Ue8u3mftBqi2ZyR8GzgW17VdVDHvx5iL?=
 =?us-ascii?Q?/lrZDzDX3l2AoQ835pMXhZkdjRNuIBNj3VmZHhgcWDZ5MbKUpuV9guHqOTqm?=
 =?us-ascii?Q?QJZWFqGhnFk1sfXt+K58JeweWRCqpYo4B4qLYAolu1qV8o+rux8VvcQxPyXd?=
 =?us-ascii?Q?pfM4j4pN2+NLFT/Ofwds0JjC+quATvgOFTHtwpgUkfGeBAcPZa+9JlTwL9I2?=
 =?us-ascii?Q?nrzcmrlsZYHhV9XOh/Hm94dOzXQmrjxWMyqPspVuv+9a/CRJ4tORdOgDWoNZ?=
 =?us-ascii?Q?xPlfuGdSe26beCHFM+dYr2J++kVAINIeHRJV/gS4Bc0shTxVjE7oEg99jNmo?=
 =?us-ascii?Q?sVCkui8wJ0kE6t/EDAzjtiEKUYFdIahmydGQJJ+K1dOTx6OVLSQnHwQKDVcd?=
 =?us-ascii?Q?xob8U8Yv7bGeuVSCZhxIY9wju5/h4Ua97Uqvq3U1qv3cvcgAl2DDn9rOA8oo?=
 =?us-ascii?Q?1zDFPzDYKlXI9d1aEFeW8Q+BuNcMkEWFHLLZvJStAQ5/ja+L+AQfvYFSaYgc?=
 =?us-ascii?Q?6mN9gZ00p7nwHiZ4IqPNp+KRJ3X1CA16QIQdOQ+Wg/gWVHTMwpSzZL4SSNWh?=
 =?us-ascii?Q?QF7NPwWVKdkBamZzxYCNa57k7KCMoavcCZCfrGYAxnWfLeq9m45RFN42JPy+?=
 =?us-ascii?Q?nDAXMbe8fUq6L4sgWPt8vcn7zhKmOdUe5TFDjaY+Ekxd//7hZsuz9sdWL3AE?=
 =?us-ascii?Q?/O3ri+INuHvl0N31usEw+rs8edLA5Zg7kk3vI5rzSdH6MmZohaUoaVCJro0m?=
 =?us-ascii?Q?/JlngYEiM+MUF/FntLmEDq8GgWWyqM4xWh3R48MboEdStootYCtxjCk3l8g1?=
 =?us-ascii?Q?i/Mr6F37dQxO9dXDiv+UkgsWSSqWFVk7g0opgjP1vOYq6WGoETeJyDOmO+jc?=
 =?us-ascii?Q?xUSE7p1ATqJGlRrE8Z8qNBAMB2XIsnTd/2vPD6Ffk73VgjqrytBQbLcQXbPd?=
 =?us-ascii?Q?kS7G9OqUGTD1W3WshK+PXj8=3D?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: ce1964c7-cf13-4eec-4b65-08d9d6818c2a
X-MS-Exchange-CrossTenant-AuthSource: CO1PR10MB4468.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jan 2022 10:43:34.1894
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: SH2iBQ/FJemeIc+qaTrRcFdC+bbCzjhRAmoYbjrFDFaB7CWnDoobAIyXzIj8eG5qMQCiP1feseVrJ52woWIl/w==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR10MB1751
X-Proofpoint-Virus-Version: vendor=nai engine=6300 definitions=10225 signatures=668683
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 suspectscore=0 spamscore=0
 mlxlogscore=490 adultscore=0 phishscore=0 malwarescore=0 bulkscore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000
 definitions=main-2201130063
X-Proofpoint-GUID: mNs2jiSSQm7BST3XrkYs-b7_00fJmQC3
X-Proofpoint-ORIG-GUID: mNs2jiSSQm7BST3XrkYs-b7_00fJmQC3
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Reduce contention around global locks used in kernfs.

PATCH-1: Make global kernfs_open_file_mutex and kernfs_open_node_lock
	 hashed locks, where address of a kernfs_node acts as hash key.
	 This results in kernfs_node objects, whose address give the
	 different hash value, using different kernfs_open_file_mutex
	 and kernfs_open_node_lock rather than all kernfs_node objects
	 using the same kernfs_open_file_mutex and kernfs_open_node_lock
	 as was the case earlier.

PATCH-2: Use a hashed rw_semaphore to access permissions, so that we can
	 avoid contention around global per-fs rw_semaphore, seen if
	 multiple applications are executing inode_permission and
	 walk_component in parallel when trying to open sysfs file(s).

------------------------------------------------------------------

Changes since v2:
 - Remove RFC tag
 - Use hashed locks rather than using per kernfs_node specific lock
   (Suggested by Tejun Heo <tj@kernel.org>)
   

Imran Khan (2):
  kernfs: use hashed mutex and spinlock in place of global ones.
  kernfs: Reduce contention around global per-fs kernfs_rwsem.

 fs/kernfs/dir.c             |  8 +++++
 fs/kernfs/file.c            | 65 ++++++++++++++++-----------------
 fs/kernfs/inode.c           | 35 ++++++++++++------
 fs/kernfs/kernfs-internal.h | 71 +++++++++++++++++++++++++++++++++++++
 fs/kernfs/mount.c           | 11 ++++++
 5 files changed, 146 insertions(+), 44 deletions(-)


base-commit: a70bf4a85b43cb952bd39dd948b103b1b3eb2cf8
-- 
2.30.2