[linux.git] / fs / nfs / io.c

// SPDX-License-Identifier: GPL-2.0
/*
 * 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);
}
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
a5864c99 TM	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 */
	18	static 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	*/
	42	void
	43	nfs_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	*/
	64	void
	65	nfs_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	*/
77	void
78	nfs_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	*/
91	void
92	nfs_end_io_write(struct inode *inode)
93	{
94	up_write(&inode->i_rwsem);
95	}
96
97	/* Call with exclusively locked inode->i_rwsem */
98	static 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_wb_all(inode);
103	}
104	}
105
106	/**
107	* nfs_end_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	*/
122	void
123	nfs_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	*/
144	void
145	nfs_end_io_direct(struct inode *inode)
146	{
147	up_read(&inode->i_rwsem);
148	}