/* * Copyright (c) 2016 Trond Myklebust * * I/O and data path helper functionality. */ #include <linux/types.h> #include <linux/kernel.h> #include <linux/bitops.h> #include <linux/rwsem.h> #include <linux/fs.h> #include <linux/nfs_fs.h> #include "internal.h" /* Call with exclusively locked inode->i_rwsem */ static void nfs_block_o_direct(struct nfs_inode *nfsi, struct inode *inode) { if (test_bit(NFS_INO_ODIRECT, &nfsi->flags)) { clear_bit(NFS_INO_ODIRECT, &nfsi->flags); inode_dio_wait(inode); } } /** * nfs_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 NFS_INO_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 * NFS_INO_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. */ void nfs_start_io_read(struct inode *inode) { struct nfs_inode *nfsi = NFS_I(inode); /* Be an optimist! */ down_read(&inode->i_rwsem); if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) == 0) return; up_read(&inode->i_rwsem); /* Slow path.... */ down_write(&inode->i_rwsem); nfs_block_o_direct(nfsi, inode); downgrade_write(&inode->i_rwsem); } /** * nfs_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 nfs_end_io_read(struct inode *inode) { up_read(&inode->i_rwsem); } /** * nfs_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. */ void nfs_start_io_write(struct inode *inode) { down_write(&inode->i_rwsem); nfs_block_o_direct(NFS_I(inode), inode); } /** * nfs_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 nfs_end_io_write(struct inode *inode) { up_write(&inode->i_rwsem); } /* Call with exclusively locked inode->i_rwsem */ static void nfs_block_buffered(struct nfs_inode *nfsi, struct inode *inode) { if (!test_bit(NFS_INO_ODIRECT, &nfsi->flags)) { set_bit(NFS_INO_ODIRECT, &nfsi->flags); nfs_wb_all(inode); } } /** * nfs_end_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 NFS_INO_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 * NFS_INO_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. */ void nfs_start_io_direct(struct inode *inode) { struct nfs_inode *nfsi = NFS_I(inode); /* Be an optimist! */ down_read(&inode->i_rwsem); if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) != 0) return; up_read(&inode->i_rwsem); /* Slow path.... */ down_write(&inode->i_rwsem); nfs_block_buffered(nfsi, inode); downgrade_write(&inode->i_rwsem); } /** * nfs_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 nfs_end_io_direct(struct inode *inode) { up_read(&inode->i_rwsem); }