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Wed, 13 Dec 2023 15:24:40 +0000 (UTC) From: David Howells To: Jeff Layton , Steve French Cc: David Howells , Matthew Wilcox , Marc Dionne , Paulo Alcantara , Shyam Prasad N , Tom Talpey , Dominique Martinet , Eric Van Hensbergen , Ilya Dryomov , Christian Brauner , linux-cachefs@redhat.com, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 11/39] netfs: Implement unbuffered/DIO vs buffered I/O locking Date: Wed, 13 Dec 2023 15:23:21 +0000 Message-ID: <20231213152350.431591-12-dhowells@redhat.com> In-Reply-To: <20231213152350.431591-1-dhowells@redhat.com> References: <20231213152350.431591-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 X-Rspamd-Queue-Id: C5801140006 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 5naramcbebr36yd3c6hjzk4wwt1ou1ab X-HE-Tag: 1702481090-977439 X-HE-Meta: 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 y+g/WBfp gMXfJM0CVdsNfv742Nvvp6PnknZ4qTqsm+TX2n6g7gow4Dm5G3T/dzZxcDZjQY8IaiLfG5IoTxfbsmbUGPPk5PTATv+z9EN83TK3SHvhVfDkXCN8PFPVpNA5Ic3M17ogtx1gdZ2IbFVh0pQ6rOJGY4J97L77fZyST0S293i1lfXUV0xlNKQu3gPdAYTh42i4XZ640zXNnqGcNqMDKvTo2GR8tI/bCtBYpomiEt8FA1fT+vjc6JRROyHiDjf9KuLFjouPFDrYQmWh022jsm2nCtTtEm0qzlhkFW9fgJ9SlCP+o5mU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Borrow NFS's direct-vs-buffered I/O locking into netfslib. Similar code is also used in ceph. Modify it to have the correct checker annotations for i_rwsem lock acquisition/release and to return -ERESTARTSYS if waits are interrupted. Signed-off-by: David Howells cc: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- fs/netfs/Makefile | 1 + fs/netfs/locking.c | 215 ++++++++++++++++++++++++++++++++++++++++++ include/linux/netfs.h | 10 ++ 3 files changed, 226 insertions(+) create mode 100644 fs/netfs/locking.c diff --git a/fs/netfs/Makefile b/fs/netfs/Makefile index a84fe9bbd3c4..cf3fc847b8ac 100644 --- a/fs/netfs/Makefile +++ b/fs/netfs/Makefile @@ -4,6 +4,7 @@ netfs-y := \ buffered_read.o \ io.o \ iterator.o \ + locking.o \ main.o \ misc.o \ objects.o diff --git a/fs/netfs/locking.c b/fs/netfs/locking.c new file mode 100644 index 000000000000..58e0f48394c5 --- /dev/null +++ b/fs/netfs/locking.c @@ -0,0 +1,215 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * I/O and data path helper functionality. + * + * Borrowed from NFS Copyright (c) 2016 Trond Myklebust + */ + +#include +#include + +/* + * inode_dio_wait_interruptible - wait for outstanding DIO requests to finish + * @inode: inode to wait for + * + * Waits for all pending direct I/O requests to finish so that we can + * proceed with a truncate or equivalent operation. + * + * Must be called under a lock that serializes taking new references + * to i_dio_count, usually by inode->i_mutex. + */ +static int inode_dio_wait_interruptible(struct inode *inode) +{ + if (!atomic_read(&inode->i_dio_count)) + return 0; + + wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_DIO_WAKEUP); + DEFINE_WAIT_BIT(q, &inode->i_state, __I_DIO_WAKEUP); + + for (;;) { + prepare_to_wait(wq, &q.wq_entry, TASK_INTERRUPTIBLE); + if (!atomic_read(&inode->i_dio_count)) + break; + if (signal_pending(current)) + break; + schedule(); + } + finish_wait(wq, &q.wq_entry); + + return atomic_read(&inode->i_dio_count) ? -ERESTARTSYS : 0; +} + +/* Call with exclusively locked inode->i_rwsem */ +static int netfs_block_o_direct(struct netfs_inode *ictx) +{ + if (!test_bit(NETFS_ICTX_ODIRECT, &ictx->flags)) + return 0; + clear_bit(NETFS_ICTX_ODIRECT, &ictx->flags); + return inode_dio_wait_interruptible(&ictx->inode); +} + +/** + * netfs_start_io_read - declare the file is being used for buffered reads + * @inode: file inode + * + * Declare that a buffered read operation is about to start, and ensure + * that we block all direct I/O. + * On exit, the function ensures that the NETFS_ICTX_ODIRECT flag is unset, + * and holds a shared lock on inode->i_rwsem to ensure that the flag + * cannot be changed. + * In practice, this means that buffered read operations are allowed to + * execute in parallel, thanks to the shared lock, whereas direct I/O + * operations need to wait to grab an exclusive lock in order to set + * NETFS_ICTX_ODIRECT. + * Note that buffered writes and truncates both take a write lock on + * inode->i_rwsem, meaning that those are serialised w.r.t. the reads. + */ +int netfs_start_io_read(struct inode *inode) + __acquires(inode->i_rwsem) +{ + struct netfs_inode *ictx = netfs_inode(inode); + + /* Be an optimist! */ + if (down_read_interruptible(&inode->i_rwsem) < 0) + return -ERESTARTSYS; + if (test_bit(NETFS_ICTX_ODIRECT, &ictx->flags) == 0) + return 0; + up_read(&inode->i_rwsem); + + /* Slow path.... */ + if (down_write_killable(&inode->i_rwsem) < 0) + return -ERESTARTSYS; + if (netfs_block_o_direct(ictx) < 0) { + up_write(&inode->i_rwsem); + return -ERESTARTSYS; + } + downgrade_write(&inode->i_rwsem); + return 0; +} +EXPORT_SYMBOL(netfs_start_io_read); + +/** + * netfs_end_io_read - declare that the buffered read operation is done + * @inode: file inode + * + * Declare that a buffered read operation is done, and release the shared + * lock on inode->i_rwsem. + */ +void netfs_end_io_read(struct inode *inode) + __releases(inode->i_rwsem) +{ + up_read(&inode->i_rwsem); +} +EXPORT_SYMBOL(netfs_end_io_read); + +/** + * netfs_start_io_write - declare the file is being used for buffered writes + * @inode: file inode + * + * Declare that a buffered read operation is about to start, and ensure + * that we block all direct I/O. + */ +int netfs_start_io_write(struct inode *inode) + __acquires(inode->i_rwsem) +{ + struct netfs_inode *ictx = netfs_inode(inode); + + if (down_write_killable(&inode->i_rwsem) < 0) + return -ERESTARTSYS; + if (netfs_block_o_direct(ictx) < 0) { + up_write(&inode->i_rwsem); + return -ERESTARTSYS; + } + return 0; +} +EXPORT_SYMBOL(netfs_start_io_write); + +/** + * netfs_end_io_write - declare that the buffered write operation is done + * @inode: file inode + * + * Declare that a buffered write operation is done, and release the + * lock on inode->i_rwsem. + */ +void netfs_end_io_write(struct inode *inode) + __releases(inode->i_rwsem) +{ + up_write(&inode->i_rwsem); +} +EXPORT_SYMBOL(netfs_end_io_write); + +/* Call with exclusively locked inode->i_rwsem */ +static int netfs_block_buffered(struct inode *inode) +{ + struct netfs_inode *ictx = netfs_inode(inode); + int ret; + + if (!test_bit(NETFS_ICTX_ODIRECT, &ictx->flags)) { + set_bit(NETFS_ICTX_ODIRECT, &ictx->flags); + if (inode->i_mapping->nrpages != 0) { + unmap_mapping_range(inode->i_mapping, 0, 0, 0); + ret = filemap_fdatawait(inode->i_mapping); + if (ret < 0) { + clear_bit(NETFS_ICTX_ODIRECT, &ictx->flags); + return ret; + } + } + } + return 0; +} + +/** + * netfs_start_io_direct - declare the file is being used for direct i/o + * @inode: file inode + * + * Declare that a direct I/O operation is about to start, and ensure + * that we block all buffered I/O. + * On exit, the function ensures that the NETFS_ICTX_ODIRECT flag is set, + * and holds a shared lock on inode->i_rwsem to ensure that the flag + * cannot be changed. + * In practice, this means that direct I/O operations are allowed to + * execute in parallel, thanks to the shared lock, whereas buffered I/O + * operations need to wait to grab an exclusive lock in order to clear + * NETFS_ICTX_ODIRECT. + * Note that buffered writes and truncates both take a write lock on + * inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT. + */ +int netfs_start_io_direct(struct inode *inode) + __acquires(inode->i_rwsem) +{ + struct netfs_inode *ictx = netfs_inode(inode); + int ret; + + /* Be an optimist! */ + if (down_read_interruptible(&inode->i_rwsem) < 0) + return -ERESTARTSYS; + if (test_bit(NETFS_ICTX_ODIRECT, &ictx->flags) != 0) + return 0; + up_read(&inode->i_rwsem); + + /* Slow path.... */ + if (down_write_killable(&inode->i_rwsem) < 0) + return -ERESTARTSYS; + ret = netfs_block_buffered(inode); + if (ret < 0) { + up_write(&inode->i_rwsem); + return ret; + } + downgrade_write(&inode->i_rwsem); + return 0; +} +EXPORT_SYMBOL(netfs_start_io_direct); + +/** + * netfs_end_io_direct - declare that the direct i/o operation is done + * @inode: file inode + * + * Declare that a direct I/O operation is done, and release the shared + * lock on inode->i_rwsem. + */ +void netfs_end_io_direct(struct inode *inode) + __releases(inode->i_rwsem) +{ + up_read(&inode->i_rwsem); +} +EXPORT_SYMBOL(netfs_end_io_direct); diff --git a/include/linux/netfs.h b/include/linux/netfs.h index 8efbfd3b2820..fc6d9756a029 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -129,6 +129,8 @@ struct netfs_inode { struct fscache_cookie *cache; #endif loff_t remote_i_size; /* Size of the remote file */ + unsigned long flags; +#define NETFS_ICTX_ODIRECT 0 /* The file has DIO in progress */ }; /* @@ -310,6 +312,13 @@ ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len, struct iov_iter *new, iov_iter_extraction_t extraction_flags); +int netfs_start_io_read(struct inode *inode); +void netfs_end_io_read(struct inode *inode); +int netfs_start_io_write(struct inode *inode); +void netfs_end_io_write(struct inode *inode); +int netfs_start_io_direct(struct inode *inode); +void netfs_end_io_direct(struct inode *inode); + /** * netfs_inode - Get the netfs inode context from the inode * @inode: The inode to query @@ -335,6 +344,7 @@ static inline void netfs_inode_init(struct netfs_inode *ctx, { ctx->ops = ops; ctx->remote_i_size = i_size_read(&ctx->inode); + ctx->flags = 0; #if IS_ENABLED(CONFIG_FSCACHE) ctx->cache = NULL; #endif