cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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io.c (4167B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * Copyright (c) 2016 Trond Myklebust
      4 *
      5 * I/O and data path helper functionality.
      6 */
      7
      8#include <linux/types.h>
      9#include <linux/kernel.h>
     10#include <linux/bitops.h>
     11#include <linux/rwsem.h>
     12#include <linux/fs.h>
     13#include <linux/nfs_fs.h>
     14
     15#include "internal.h"
     16
     17/* Call with exclusively locked inode->i_rwsem */
     18static void nfs_block_o_direct(struct nfs_inode *nfsi, struct inode *inode)
     19{
     20	if (test_bit(NFS_INO_ODIRECT, &nfsi->flags)) {
     21		clear_bit(NFS_INO_ODIRECT, &nfsi->flags);
     22		inode_dio_wait(inode);
     23	}
     24}
     25
     26/**
     27 * nfs_start_io_read - declare the file is being used for buffered reads
     28 * @inode: file inode
     29 *
     30 * Declare that a buffered read operation is about to start, and ensure
     31 * that we block all direct I/O.
     32 * On exit, the function ensures that the NFS_INO_ODIRECT flag is unset,
     33 * and holds a shared lock on inode->i_rwsem to ensure that the flag
     34 * cannot be changed.
     35 * In practice, this means that buffered read operations are allowed to
     36 * execute in parallel, thanks to the shared lock, whereas direct I/O
     37 * operations need to wait to grab an exclusive lock in order to set
     38 * NFS_INO_ODIRECT.
     39 * Note that buffered writes and truncates both take a write lock on
     40 * inode->i_rwsem, meaning that those are serialised w.r.t. the reads.
     41 */
     42void
     43nfs_start_io_read(struct inode *inode)
     44{
     45	struct nfs_inode *nfsi = NFS_I(inode);
     46	/* Be an optimist! */
     47	down_read(&inode->i_rwsem);
     48	if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) == 0)
     49		return;
     50	up_read(&inode->i_rwsem);
     51	/* Slow path.... */
     52	down_write(&inode->i_rwsem);
     53	nfs_block_o_direct(nfsi, inode);
     54	downgrade_write(&inode->i_rwsem);
     55}
     56
     57/**
     58 * nfs_end_io_read - declare that the buffered read operation is done
     59 * @inode: file inode
     60 *
     61 * Declare that a buffered read operation is done, and release the shared
     62 * lock on inode->i_rwsem.
     63 */
     64void
     65nfs_end_io_read(struct inode *inode)
     66{
     67	up_read(&inode->i_rwsem);
     68}
     69
     70/**
     71 * nfs_start_io_write - declare the file is being used for buffered writes
     72 * @inode: file inode
     73 *
     74 * Declare that a buffered read operation is about to start, and ensure
     75 * that we block all direct I/O.
     76 */
     77void
     78nfs_start_io_write(struct inode *inode)
     79{
     80	down_write(&inode->i_rwsem);
     81	nfs_block_o_direct(NFS_I(inode), inode);
     82}
     83
     84/**
     85 * nfs_end_io_write - declare that the buffered write operation is done
     86 * @inode: file inode
     87 *
     88 * Declare that a buffered write operation is done, and release the
     89 * lock on inode->i_rwsem.
     90 */
     91void
     92nfs_end_io_write(struct inode *inode)
     93{
     94	up_write(&inode->i_rwsem);
     95}
     96
     97/* Call with exclusively locked inode->i_rwsem */
     98static void nfs_block_buffered(struct nfs_inode *nfsi, struct inode *inode)
     99{
    100	if (!test_bit(NFS_INO_ODIRECT, &nfsi->flags)) {
    101		set_bit(NFS_INO_ODIRECT, &nfsi->flags);
    102		nfs_sync_mapping(inode->i_mapping);
    103	}
    104}
    105
    106/**
    107 * nfs_start_io_direct - declare the file is being used for direct i/o
    108 * @inode: file inode
    109 *
    110 * Declare that a direct I/O operation is about to start, and ensure
    111 * that we block all buffered I/O.
    112 * On exit, the function ensures that the NFS_INO_ODIRECT flag is set,
    113 * and holds a shared lock on inode->i_rwsem to ensure that the flag
    114 * cannot be changed.
    115 * In practice, this means that direct I/O operations are allowed to
    116 * execute in parallel, thanks to the shared lock, whereas buffered I/O
    117 * operations need to wait to grab an exclusive lock in order to clear
    118 * NFS_INO_ODIRECT.
    119 * Note that buffered writes and truncates both take a write lock on
    120 * inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT.
    121 */
    122void
    123nfs_start_io_direct(struct inode *inode)
    124{
    125	struct nfs_inode *nfsi = NFS_I(inode);
    126	/* Be an optimist! */
    127	down_read(&inode->i_rwsem);
    128	if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) != 0)
    129		return;
    130	up_read(&inode->i_rwsem);
    131	/* Slow path.... */
    132	down_write(&inode->i_rwsem);
    133	nfs_block_buffered(nfsi, inode);
    134	downgrade_write(&inode->i_rwsem);
    135}
    136
    137/**
    138 * nfs_end_io_direct - declare that the direct i/o operation is done
    139 * @inode: file inode
    140 *
    141 * Declare that a direct I/O operation is done, and release the shared
    142 * lock on inode->i_rwsem.
    143 */
    144void
    145nfs_end_io_direct(struct inode *inode)
    146{
    147	up_read(&inode->i_rwsem);
    148}