Add --readonly option
[fio.git] / syslet.h
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1#ifndef _LINUX_SYSLET_H
2#define _LINUX_SYSLET_H
3/*
4 * The syslet subsystem - asynchronous syscall execution support.
5 *
6 * Started by Ingo Molnar:
7 *
8 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
9 *
10 * User-space API/ABI definitions:
11 */
12
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13#ifndef __user
14# define __user
15#endif
16
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17/*
18 * This is the 'Syslet Atom' - the basic unit of execution
19 * within the syslet framework. A syslet always represents
20 * a single system-call plus its arguments, plus has conditions
21 * attached to it that allows the construction of larger
22 * programs from these atoms. User-space variables can be used
23 * (for example a loop index) via the special sys_umem*() syscalls.
24 *
25 * Arguments are implemented via pointers to arguments. This not
26 * only increases the flexibility of syslet atoms (multiple syslets
27 * can share the same variable for example), but is also an
28 * optimization: copy_uatom() will only fetch syscall parameters
29 * up until the point it meets the first NULL pointer. 50% of all
30 * syscalls have 2 or less parameters (and 90% of all syscalls have
31 * 4 or less parameters).
32 *
33 * [ Note: since the argument array is at the end of the atom, and the
34 * kernel will not touch any argument beyond the final NULL one, atoms
35 * might be packed more tightly. (the only special case exception to
36 * this rule would be SKIP_TO_NEXT_ON_STOP atoms, where the kernel will
37 * jump a full syslet_uatom number of bytes.) ]
38 */
39struct syslet_uatom {
40 unsigned long flags;
41 unsigned long nr;
42 long __user *ret_ptr;
43 struct syslet_uatom __user *next;
44 unsigned long __user *arg_ptr[6];
45 /*
46 * User-space can put anything in here, kernel will not
47 * touch it:
48 */
49 void __user *private;
50};
51
52/*
53 * Flags to modify/control syslet atom behavior:
54 */
55
56/*
57 * Immediately queue this syslet asynchronously - do not even
58 * attempt to execute it synchronously in the user context:
59 */
60#define SYSLET_ASYNC 0x00000001
61
62/*
63 * Never queue this syslet asynchronously - even if synchronous
64 * execution causes a context-switching:
65 */
66#define SYSLET_SYNC 0x00000002
67
68/*
69 * Do not queue the syslet in the completion ring when done.
70 *
71 * ( the default is that the final atom of a syslet is queued
72 * in the completion ring. )
73 *
74 * Some syscalls generate implicit completion events of their
75 * own.
76 */
77#define SYSLET_NO_COMPLETE 0x00000004
78
79/*
80 * Execution control: conditions upon the return code
bf0dc8fa 81 * of the just executed syslet atom. 'Stop' means syslet
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82 * execution is stopped and the atom is put into the
83 * completion ring:
84 */
85#define SYSLET_STOP_ON_NONZERO 0x00000008
86#define SYSLET_STOP_ON_ZERO 0x00000010
87#define SYSLET_STOP_ON_NEGATIVE 0x00000020
88#define SYSLET_STOP_ON_NON_POSITIVE 0x00000040
89
90#define SYSLET_STOP_MASK \
91 ( SYSLET_STOP_ON_NONZERO | \
92 SYSLET_STOP_ON_ZERO | \
93 SYSLET_STOP_ON_NEGATIVE | \
94 SYSLET_STOP_ON_NON_POSITIVE )
95
96/*
97 * Special modifier to 'stop' handling: instead of stopping the
98 * execution of the syslet, the linearly next syslet is executed.
99 * (Normal execution flows along atom->next, and execution stops
100 * if atom->next is NULL or a stop condition becomes true.)
101 *
102 * This is what allows true branches of execution within syslets.
103 */
104#define SYSLET_SKIP_TO_NEXT_ON_STOP 0x00000080
105
106/*
107 * This is the (per-user-context) descriptor of the async completion
bf0dc8fa 108 * ring. This gets passed in to sys_async_exec():
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109 */
110struct async_head_user {
111 /*
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112 * Current completion ring index - managed by the kernel:
113 */
114 unsigned long kernel_ring_idx;
115 /*
116 * User-side ring index:
117 */
118 unsigned long user_ring_idx;
119
120 /*
121 * Ring of pointers to completed async syslets (i.e. syslets that
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122 * generated a cachemiss and went async, returning -EASYNCSYSLET
123 * to the user context by sys_async_exec()) are queued here.
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124 * Syslets that were executed synchronously (cached) are not
125 * queued here.
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126 *
127 * Note: the final atom that generated the exit condition is
128 * queued here. Normally this would be the last atom of a syslet.
129 */
130 struct syslet_uatom __user **completion_ring;
bf0dc8fa 131
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132 /*
133 * Ring size in bytes:
134 */
135 unsigned long ring_size_bytes;
136
137 /*
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138 * The head task can become a cachemiss thread later on
139 * too, if it blocks - so it needs its separate thread
140 * stack and start address too:
141 */
142 unsigned long head_stack;
143 unsigned long head_eip;
144
145 /*
146 * Newly started async kernel threads will take their
147 * user stack and user start address from here. User-space
148 * code has to check for new_thread_stack going to NULL
149 * and has to refill it with a new stack if that happens.
a4f4fdd7 150 */
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151 unsigned long new_thread_stack;
152 unsigned long new_thread_eip;
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153};
154
155#endif