[v2,07/51] netfs: Implement unbuffered/DIO vs buffered I/O locking

Message ID	20231117211544.1740466-8-dhowells@redhat.com (mailing list archive)
State	New, archived
Headers	show Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WW4831WX" From: David Howells <dhowells@redhat.com> To: Jeff Layton <jlayton@kernel.org>, Steve French <smfrench@gmail.com> Cc: David Howells <dhowells@redhat.com>, Matthew Wilcox <willy@infradead.org>, Marc Dionne <marc.dionne@auristor.com>, Paulo Alcantara <pc@manguebit.com>, Shyam Prasad N <sprasad@microsoft.com>, Tom Talpey <tom@talpey.com>, Dominique Martinet <asmadeus@codewreck.org>, Ilya Dryomov <idryomov@gmail.com>, Christian Brauner <christian@brauner.io>, 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 v2 07/51] netfs: Implement unbuffered/DIO vs buffered I/O locking Date: Fri, 17 Nov 2023 21:14:59 +0000 Message-ID: <20231117211544.1740466-8-dhowells@redhat.com> In-Reply-To: <20231117211544.1740466-1-dhowells@redhat.com> References: <20231117211544.1740466-1-dhowells@redhat.com> Precedence: bulk MIME-Version: 1.0 Content-Transfer-Encoding: 8bit
Series	netfs, afs, cifs: Delegate high-level I/O to netfslib \| expand [v2,00/51] netfs, afs, cifs: Delegate high-level I/O to netfslib [v2,01/51] netfs: Add a procfile to list in-progress requests [v2,02/51] netfs: Track the fpos above which the server has no data [v2,03/51] netfs: Allow the netfs to make the io (sub)request alloc larger [v2,04/51] netfs: Add a ->free_subrequest() op [v2,05/51] afs: Don't use folio->private to record partial modification [v2,06/51] netfs: Provide invalidate_folio and release_folio calls [v2,07/51] netfs: Implement unbuffered/DIO vs buffered I/O locking [v2,08/51] netfs: Add iov_iters to (sub)requests to describe various buffers [v2,09/51] netfs: Add support for DIO buffering [v2,10/51] netfs: Provide tools to create a buffer in an xarray [v2,11/51] netfs: Add bounce buffering support [v2,12/51] netfs: Add func to calculate pagecount/size-limited span of an iterator [v2,13/51] netfs: Limit subrequest by size or number of segments [v2,14/51] netfs: Export netfs_put_subrequest() and some tracepoints [v2,15/51] netfs: Extend the netfs_io_*request structs to handle writes [v2,16/51] netfs: Add a hook to allow tell the netfs to update its i_size [v2,17/51] netfs: Make netfs_put_request() handle a NULL pointer [v2,18/51] fscache: Add a function to begin an cache op from a netfslib request [v2,19/51] netfs: Make the refcounting of netfs_begin_read() easier to use [v2,20/51] netfs: Prep to use folio->private for write grouping and streaming write [v2,21/51] netfs: Dispatch write requests to process a writeback slice [v2,22/51] netfs: Provide func to copy data to pagecache for buffered write [v2,23/51] netfs: Make netfs_read_folio() handle streaming-write pages [v2,24/51] netfs: Allocate multipage folios in the writepath [v2,25/51] netfs: Implement support for unbuffered/DIO read [v2,26/51] netfs: Implement unbuffered/DIO write support [v2,27/51] netfs: Implement buffered write API [v2,28/51] netfs: Allow buffered shared-writeable mmap through netfs_page_mkwrite() [v2,29/51] netfs: Provide netfs_file_read_iter() [v2,30/51] netfs: Provide a writepages implementation [v2,31/51] netfs: Provide minimum blocksize parameter [v2,32/51] netfs: Make netfs_skip_folio_read() take account of blocksize [v2,33/51] netfs: Perform content encryption [v2,34/51] netfs: Decrypt encrypted content [v2,35/51] netfs: Support decryption on ubuffered/DIO read [v2,36/51] netfs: Support encryption on Unbuffered/DIO write [v2,37/51] netfs: Provide a launder_folio implementation [v2,38/51] netfs: Implement a write-through caching option [v2,39/51] netfs: Rearrange netfs_io_subrequest to put request pointer first [v2,40/51] afs: Use the netfs write helpers [v2,41/51] cifs: Replace cifs_readdata with a wrapper around netfs_io_subrequest [v2,42/51] cifs: Share server EOF pos with netfslib [v2,43/51] cifs: Replace cifs_writedata with a wrapper around netfs_io_subrequest [v2,44/51] cifs: Use more fields from netfs_io_subrequest [v2,45/51] cifs: Make wait_mtu_credits take size_t args [v2,46/51] cifs: Implement netfslib hooks [v2,47/51] cifs: Move cifs_loose_read_iter() and cifs_file_write_iter() to file.c [v2,48/51] cifs: Cut over to using netfslib [v2,49/51] cifs: Remove some code that's no longer used, part 1 [v2,50/51] cifs: Remove some code that's no longer used, part 2 [v2,51/51] cifs: Remove some code that's no longer used, part 3

diff --git a/fs/netfs/Makefile b/fs/netfs/Makefile index cd22554d9048..647ce1935674 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 <linux/kernel.h> +#include <linux/netfs.h> + +/* + * 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 6e662832c3ae..18e3d8b53646 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -131,6 +131,8 @@ struct netfs_inode { loff_t remote_i_size; /* Size of the remote file */ loff_t zero_point; /* Size after which we assume there's no data * on the server */ + unsigned long flags; +#define NETFS_ICTX_ODIRECT 0 /* The file has DIO in progress */ }; /* @@ -312,6 +314,13 @@ 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 @@ -338,6 +347,7 @@ static inline void netfs_inode_init(struct netfs_inode *ctx, ctx->ops = ops; ctx->remote_i_size = i_size_read(&ctx->inode); ctx->zero_point = ctx->remote_i_size; + ctx->flags = 0; #if IS_ENABLED(CONFIG_FSCACHE) ctx->cache = NULL; #endif

[v2,07/51] netfs: Implement unbuffered/DIO vs buffered I/O locking

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