| Message ID | 20231013160423.2218093-10-dhowells@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | netfs, afs, cifs: Delegate high-level I/O to netfslib | expand |
On Fri, 2023-10-13 at 17:03 +0100, David Howells wrote: > 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 <dhowells@redhat.com> > cc: Jeff Layton <jlayton@kernel.org> > cc: linux-cachefs@redhat.com > cc: linux-fsdevel@vger.kernel.org > cc: linux-mm@kvack.org > --- > fs/netfs/Makefile | 1 + > fs/netfs/locking.c | 209 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/netfs.h | 10 ++ > 3 files changed, 220 insertions(+) > create mode 100644 fs/netfs/locking.c > > 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..fecca8ea6322 > --- /dev/null > +++ b/fs/netfs/locking.c > @@ -0,0 +1,209 @@ > +// 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; > +} > + > +/** > + * 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); > +} > + > +/** > + * 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; > +} > + > +/** > + * 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); > +} > + > +/* 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; > +} > + > +/** > + * 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); > +} > diff --git a/include/linux/netfs.h b/include/linux/netfs.h > index 02e888c170da..33d4487a91e9 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 */ > }; > > /* > @@ -315,6 +317,13 @@ 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 > @@ -341,6 +350,7 @@ 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 > It's nice to see this go into common code, but why not go ahead and convert ceph (and possibly NFS) to use this? Is there any reason not to?
Jeff Layton <jlayton@kernel.org> wrote: > It's nice to see this go into common code, but why not go ahead and > convert ceph (and possibly NFS) to use this? Is there any reason not to? I'm converting ceph on a follow-on branch and for ceph this will be dealt with there. I could do NFS round about here, I suppose. David
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..fecca8ea6322 --- /dev/null +++ b/fs/netfs/locking.c @@ -0,0 +1,209 @@ +// 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; +} + +/** + * 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); +} + +/** + * 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; +} + +/** + * 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); +} + +/* 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; +} + +/** + * 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); +} diff --git a/include/linux/netfs.h b/include/linux/netfs.h index 02e888c170da..33d4487a91e9 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 */ }; /* @@ -315,6 +317,13 @@ 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 @@ -341,6 +350,7 @@ 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
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 <dhowells@redhat.com> cc: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- fs/netfs/Makefile | 1 + fs/netfs/locking.c | 209 ++++++++++++++++++++++++++++++++++++++++++ include/linux/netfs.h | 10 ++ 3 files changed, 220 insertions(+) create mode 100644 fs/netfs/locking.c