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[146.199.243.234]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45ef354cd7csm13443784f8f.18.2026.05.30.15.20.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 30 May 2026 15:20:06 -0700 (PDT) From: Dylan Yudaken To: trondmy@kernel.org, anna@kernel.org, linux-nfs@vger.kernel.org Cc: axboe@kernel.dk, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Dylan Yudaken Subject: [PATCH 1/2] nfs: add nowait version of nfs_start_io_direct Date: Sat, 30 May 2026 23:19:46 +0100 Message-ID: <20260530221947.49518-2-dyudaken@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260530221947.49518-1-dyudaken@gmail.com> References: <20260530221947.49518-1-dyudaken@gmail.com> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit nfs_start_io_direct might block on existing operations to the same inode. In order to support NOWAIT O_DIRECT reads, add a non-blocking version of this nfs_start_io_direct that just returns -EAGAIN if locks could not be taken. Signed-off-by: Dylan Yudaken --- fs/nfs/internal.h | 1 + fs/nfs/io.c | 38 ++++++++++++++++++++++++++++++++++++-- 2 files changed, 37 insertions(+), 2 deletions(-) diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h index 18d46b0e71dd..0c9aca624353 100644 --- a/fs/nfs/internal.h +++ b/fs/nfs/internal.h @@ -532,6 +532,7 @@ extern void nfs_end_io_read(struct inode *inode); extern __must_check int nfs_start_io_write(struct inode *inode); extern void nfs_end_io_write(struct inode *inode); extern __must_check int nfs_start_io_direct(struct inode *inode); +extern __must_check int nfs_start_io_direct_nowait(struct inode *inode); extern void nfs_end_io_direct(struct inode *inode); static inline bool nfs_file_io_is_buffered(struct nfs_inode *nfsi) diff --git a/fs/nfs/io.c b/fs/nfs/io.c index 8337f0ae852d..f359a19f7879 100644 --- a/fs/nfs/io.c +++ b/fs/nfs/io.c @@ -101,12 +101,15 @@ nfs_end_io_write(struct inode *inode) EXPORT_SYMBOL_GPL(nfs_end_io_write); /* Call with exclusively locked inode->i_rwsem */ -static void nfs_block_buffered(struct nfs_inode *nfsi, struct inode *inode) +static int nfs_block_buffered(struct nfs_inode *nfsi, struct inode *inode, bool nowait) { if (!test_bit(NFS_INO_ODIRECT, &nfsi->flags)) { + if (nowait && !mapping_empty(inode->i_mapping)) + return 1; set_bit(NFS_INO_ODIRECT, &nfsi->flags); nfs_sync_mapping(inode->i_mapping); } + return 0; } /** @@ -143,12 +146,43 @@ nfs_start_io_direct(struct inode *inode) err = down_write_killable(&inode->i_rwsem); if (err) return err; - nfs_block_buffered(nfsi, inode); + nfs_block_buffered(nfsi, inode, false); downgrade_write(&inode->i_rwsem); return 0; } +/** + * nfs_start_io_direct_nowait - non-blocking variant of nfs_start_io_direct() + * @inode: file inode + * + * Try to declare that a direct I/O operation is about to start without + * blocking. + * Ensure all buffered I/O is blocked. + * If this could not be done without blocking then returns -EAGAIN. + */ +int +nfs_start_io_direct_nowait(struct inode *inode) +{ + struct nfs_inode *nfsi = NFS_I(inode); + + if (!down_read_trylock(&inode->i_rwsem)) + return -EAGAIN; + if (test_bit(NFS_INO_ODIRECT, &nfsi->flags)) + return 0; + up_read(&inode->i_rwsem); + + /* Slow path: try to flip NFS_INO_ODIRECT without blocking. */ + if (!down_write_trylock(&inode->i_rwsem)) + return -EAGAIN; + if (nfs_block_buffered(nfsi, inode, true)) { + up_write(&inode->i_rwsem); + return -EAGAIN; + } + downgrade_write(&inode->i_rwsem); + return 0; +} + /** * nfs_end_io_direct - declare that the direct i/o operation is done * @inode: file inode -- 2.50.1