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Wong" , Carlos Maiolino , Alexander Viro , Jan Kara , Matthew Wilcox , Andrew Morton , Ritesh Harjani , Zhang Yi , Christoph Hellwig , Dave Chinner , Daniel Gomez , Pankaj Raghav , Theodore Tso , linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andres Freund Subject: [RFC PATCH v4 09/12] fs: Introduce RWF_NOSERIAL flag to indicate parallel reads/writes Date: Mon, 28 Sep 2026 17:33:10 +0530 Message-ID: X-Mailer: git-send-email 2.55.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: 50-d__L22Uwuc6rqBDI6ziDGVC7BVx27 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTI4MDA0NiBTYWx0ZWRfX6B6VQhwmoY7z RiCXZRXYFR75ljgYTli6aa3Q6ugu0u5zKb2LsUao3JX/1E5VEwz2OFHVukE+GyqvXKb2p10LyWq RyqVs8k9pSh569qpZ6P5swPcbKTKUSCOBIojkFoHX/XMEmPSkqU7Qez4nJHWEwvOyIBhAxu47wF 8To0VOqj6ySbKW6COMHvJs+W+yFBhVuSsslzrtbJo3NM5bQJyqnhTEn7TL+azbi7ItBoHJebMnO zDKZWiAEjULSNWqXLOOW8I0e9dmHEoyRBlNT9FJ3ElZ3zxuXkxD9YMulXhxUtfaBPAVCWW5aSmd v1ywK8XPBrLJzOh+jo1/Y+0Fb22vktPLsdrPuHT6Jsdz6mMe/byQUTBtTlbiiv7XfJpbpBg1Csz U9OjByHlXEvJLk5/31fUJ+frFaBtpId+pKYW/lBExCtp6JMf0TCcstBqLwqUlvDn9PQcSP0iIq3 MpOtRZp1mSdZ2GUPz8w== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTI4MDA0NiBTYWx0ZWRfX23CG5JwwlRUY w3nGU6aHhWr+ajy7h6Yq0qQNypZ/n2qWJ6BGlj/fRka/x9l7qJgEixlLO0mgOjrLEh7iWrGqug8 8opjFy3yrB2x79cTGdILok2tgEKxRUQ= X-Authority-Analysis: v=2.4 cv=EY5d0/mC c=1 sm=1 tr=0 ts=6aba57be cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=pGLkceISAAAA:8 a=VnNF1IyMAAAA:8 a=PvrWFl4sATcegnk1AMAA:9 X-Proofpoint-GUID: UF5CUcTjUPErWdos58_oxZhQEQt19kSJ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-28_03,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 suspectscore=0 adultscore=0 clxscore=1015 malwarescore=0 impostorscore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609280046 X-Stat-Signature: dcwf9qhp5z4zs6bq4aij67553yqfskek X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 1080218000C X-HE-Tag: 1790597064-501510 X-HE-Meta: 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 wo2ubNAQ So8hwkXtCbXhi9AF2Czxa/G9gj7v2ffeL2AiIj8UN1uPb3TTW+hYGy9TUkwzGkjq5f+M6WZwwylgTe6wY8OHz1dBSPnwpAldK5AjeOVlZ46h3BWRuKDf6a0WEfIC30L0epkcPEpUv3tJdSnfgPu0nxiWP4vdjh27fhFt2c1vMOnO9CYQqQY4H147eIf/G/LRvKrZug2XPFhS4mkgw2xPEelgqaoOKm3eU/ACpVVwPtisViuCJC8XeohR+6AUrsFQm6DuFOpXHQ5koECZo+e0BIQyX2XzfLyf6tSvRGmQi3LSRa7Him1RaMm1qBOaxyvnpc1us0wrx8GncxXHYkVvv3riPGOxp1cieG9Ja Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Introduce RWF_NOSERIAL flag to indicate that the application is okay with its reads and writes going in parallel to other read/writes. This flag will allow writes and read to go in parallel (for eg, under a shared lock) increasing performance at the cost of losing the (loosely implemented) POSIX guarantees wrt to R/W serialization that various filesystems provide. In this patch we just introduce the flag and in upcoming patches we will use it to implement parallel writes to increase performance of RWF_WRITETHROUGH Co-developed-by: Ritesh Harjani (IBM) Signed-off-by: Ritesh Harjani (IBM) Signed-off-by: Ojaswin Mujoo --- include/linux/fs.h | 10 +++++++++- include/uapi/linux/fs.h | 6 +++++- tools/include/uapi/linux/fs.h | 5 ++++- 3 files changed, 18 insertions(+), 3 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index cbaa65e05d9e..6f84bb41f84a 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -345,6 +345,7 @@ struct readahead_control; #define IOCB_DONTCACHE (__force int) RWF_DONTCACHE #define IOCB_NOSIGNAL (__force int) RWF_NOSIGNAL #define IOCB_WRITETHROUGH (__force int) RWF_WRITETHROUGH +#define IOCB_NOSERIAL (__force int) RWF_NOSERIAL /* non-RWF related bits - start at 16 */ #define IOCB_EVENTFD (1 << 16) @@ -375,7 +376,8 @@ struct readahead_control; { IOCB_NOIO, "NOIO" }, \ { IOCB_ALLOC_CACHE, "ALLOC_CACHE" }, \ { IOCB_AIO_RW, "AIO_RW" }, \ - { IOCB_HAS_METADATA, "AIO_HAS_METADATA" } + { IOCB_HAS_METADATA, "AIO_HAS_METADATA" }, \ + { IOCB_NOSERIAL, "IOCB_NOSERIAL" } struct kiocb { struct file *ki_filp; @@ -3499,6 +3501,12 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags, ki->ki_flags &= ~IOCB_APPEND; } + /* + * Currently, only writethrough supports noserial IO. + */ + if ((flags & RWF_NOSERIAL) && !(flags & RWF_WRITETHROUGH)) + return -EOPNOTSUPP; + ki->ki_flags |= kiocb_flags; return 0; } diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 67d8987b343d..b2ad2d8548ac 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -454,10 +454,14 @@ typedef int __bitwise __kernel_rwf_t; /* buffered IO that is asynchronously written through to disk after write */ #define RWF_WRITETHROUGH ((__force __kernel_rwf_t)0x00000200) +/* buffered IO writes that are non sequential because they use a shared lock */ +#define RWF_NOSERIAL ((__force __kernel_rwf_t)0x00000400) + /* mask of flags supported by the kernel */ #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ RWF_APPEND | RWF_NOAPPEND | RWF_ATOMIC |\ - RWF_DONTCACHE | RWF_NOSIGNAL | RWF_WRITETHROUGH) + RWF_DONTCACHE | RWF_NOSIGNAL | RWF_WRITETHROUGH |\ + RWF_NOSERIAL) #define PROCFS_IOCTL_MAGIC 'f' diff --git a/tools/include/uapi/linux/fs.h b/tools/include/uapi/linux/fs.h index 63ef6b126b8b..c7a1a1d238f0 100644 --- a/tools/include/uapi/linux/fs.h +++ b/tools/include/uapi/linux/fs.h @@ -347,10 +347,13 @@ typedef int __bitwise __kernel_rwf_t; /* buffered IO that is asynchronously written through to disk after write */ #define RWF_WRITETHROUGH ((__force __kernel_rwf_t)0x00000200) +/* buffered IO writes that are non sequential because they use a shared lock */ +#define RWF_NOSERIAL ((__force __kernel_rwf_t)0x00000400) + /* mask of flags supported by the kernel */ #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ RWF_APPEND | RWF_NOAPPEND | RWF_ATOMIC |\ - RWF_DONTCACHE | RWF_WRITETHROUGH) + RWF_DONTCACHE | RWF_WRITETHROUGH | RWF_NOSERIAL) #define PROCFS_IOCTL_MAGIC 'f' -- 2.55.0