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148 lines
4.1 KiB
148 lines
4.1 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Copyright (c) 2016 Trond Myklebust |
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* |
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* I/O and data path helper functionality. |
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*/ |
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#include <linux/types.h> |
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#include <linux/kernel.h> |
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#include <linux/bitops.h> |
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#include <linux/rwsem.h> |
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#include <linux/fs.h> |
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#include <linux/nfs_fs.h> |
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#include "internal.h" |
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/* Call with exclusively locked inode->i_rwsem */ |
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static void nfs_block_o_direct(struct nfs_inode *nfsi, struct inode *inode) |
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{ |
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if (test_bit(NFS_INO_ODIRECT, &nfsi->flags)) { |
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clear_bit(NFS_INO_ODIRECT, &nfsi->flags); |
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inode_dio_wait(inode); |
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} |
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} |
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/** |
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* nfs_start_io_read - declare the file is being used for buffered reads |
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* @inode: file inode |
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* |
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* Declare that a buffered read operation is about to start, and ensure |
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* that we block all direct I/O. |
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* On exit, the function ensures that the NFS_INO_ODIRECT flag is unset, |
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* and holds a shared lock on inode->i_rwsem to ensure that the flag |
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* cannot be changed. |
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* In practice, this means that buffered read operations are allowed to |
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* execute in parallel, thanks to the shared lock, whereas direct I/O |
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* operations need to wait to grab an exclusive lock in order to set |
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* NFS_INO_ODIRECT. |
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* Note that buffered writes and truncates both take a write lock on |
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* inode->i_rwsem, meaning that those are serialised w.r.t. the reads. |
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*/ |
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void |
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nfs_start_io_read(struct inode *inode) |
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{ |
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struct nfs_inode *nfsi = NFS_I(inode); |
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/* Be an optimist! */ |
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down_read(&inode->i_rwsem); |
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if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) == 0) |
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return; |
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up_read(&inode->i_rwsem); |
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/* Slow path.... */ |
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down_write(&inode->i_rwsem); |
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nfs_block_o_direct(nfsi, inode); |
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downgrade_write(&inode->i_rwsem); |
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} |
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/** |
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* nfs_end_io_read - declare that the buffered read operation is done |
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* @inode: file inode |
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* |
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* Declare that a buffered read operation is done, and release the shared |
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* lock on inode->i_rwsem. |
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*/ |
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void |
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nfs_end_io_read(struct inode *inode) |
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{ |
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up_read(&inode->i_rwsem); |
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} |
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/** |
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* nfs_start_io_write - declare the file is being used for buffered writes |
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* @inode: file inode |
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* |
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* Declare that a buffered read operation is about to start, and ensure |
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* that we block all direct I/O. |
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*/ |
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void |
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nfs_start_io_write(struct inode *inode) |
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{ |
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down_write(&inode->i_rwsem); |
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nfs_block_o_direct(NFS_I(inode), inode); |
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} |
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/** |
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* nfs_end_io_write - declare that the buffered write operation is done |
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* @inode: file inode |
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* |
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* Declare that a buffered write operation is done, and release the |
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* lock on inode->i_rwsem. |
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*/ |
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void |
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nfs_end_io_write(struct inode *inode) |
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{ |
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up_write(&inode->i_rwsem); |
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} |
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/* Call with exclusively locked inode->i_rwsem */ |
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static void nfs_block_buffered(struct nfs_inode *nfsi, struct inode *inode) |
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{ |
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if (!test_bit(NFS_INO_ODIRECT, &nfsi->flags)) { |
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set_bit(NFS_INO_ODIRECT, &nfsi->flags); |
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nfs_sync_mapping(inode->i_mapping); |
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} |
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} |
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/** |
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* nfs_start_io_direct - declare the file is being used for direct i/o |
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* @inode: file inode |
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* |
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* Declare that a direct I/O operation is about to start, and ensure |
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* that we block all buffered I/O. |
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* On exit, the function ensures that the NFS_INO_ODIRECT flag is set, |
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* and holds a shared lock on inode->i_rwsem to ensure that the flag |
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* cannot be changed. |
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* In practice, this means that direct I/O operations are allowed to |
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* execute in parallel, thanks to the shared lock, whereas buffered I/O |
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* operations need to wait to grab an exclusive lock in order to clear |
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* NFS_INO_ODIRECT. |
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* Note that buffered writes and truncates both take a write lock on |
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* inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT. |
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*/ |
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void |
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nfs_start_io_direct(struct inode *inode) |
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{ |
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struct nfs_inode *nfsi = NFS_I(inode); |
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/* Be an optimist! */ |
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down_read(&inode->i_rwsem); |
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if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) != 0) |
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return; |
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up_read(&inode->i_rwsem); |
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/* Slow path.... */ |
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down_write(&inode->i_rwsem); |
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nfs_block_buffered(nfsi, inode); |
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downgrade_write(&inode->i_rwsem); |
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} |
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/** |
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* nfs_end_io_direct - declare that the direct i/o operation is done |
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* @inode: file inode |
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* |
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* Declare that a direct I/O operation is done, and release the shared |
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* lock on inode->i_rwsem. |
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*/ |
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void |
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nfs_end_io_direct(struct inode *inode) |
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{ |
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up_read(&inode->i_rwsem); |
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}
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