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 */ |
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, addr: &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(sem: &inode->i_rwsem); |
48 | if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) == 0) |
49 | return; |
50 | up_read(sem: &inode->i_rwsem); |
51 | /* Slow path.... */ |
52 | down_write(sem: &inode->i_rwsem); |
53 | nfs_block_o_direct(nfsi, inode); |
54 | downgrade_write(sem: &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(sem: &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(sem: &inode->i_rwsem); |
81 | nfs_block_o_direct(nfsi: 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(sem: &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, addr: &nfsi->flags); |
102 | nfs_sync_mapping(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 | */ |
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(sem: &inode->i_rwsem); |
128 | if (test_bit(NFS_INO_ODIRECT, &nfsi->flags) != 0) |
129 | return; |
130 | up_read(sem: &inode->i_rwsem); |
131 | /* Slow path.... */ |
132 | down_write(sem: &inode->i_rwsem); |
133 | nfs_block_buffered(nfsi, inode); |
134 | downgrade_write(sem: &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(sem: &inode->i_rwsem); |
148 | } |
149 | |