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-rw-r--r--fs/eventfd.c122
1 files changed, 110 insertions, 12 deletions
diff --git a/fs/eventfd.c b/fs/eventfd.c
index 3f0e1974abdc..31d12de83a2a 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -14,35 +14,44 @@
14#include <linux/list.h> 14#include <linux/list.h>
15#include <linux/spinlock.h> 15#include <linux/spinlock.h>
16#include <linux/anon_inodes.h> 16#include <linux/anon_inodes.h>
17#include <linux/eventfd.h>
18#include <linux/syscalls.h> 17#include <linux/syscalls.h>
19#include <linux/module.h> 18#include <linux/module.h>
19#include <linux/kref.h>
20#include <linux/eventfd.h>
20 21
21struct eventfd_ctx { 22struct eventfd_ctx {
23 struct kref kref;
22 wait_queue_head_t wqh; 24 wait_queue_head_t wqh;
23 /* 25 /*
24 * Every time that a write(2) is performed on an eventfd, the 26 * Every time that a write(2) is performed on an eventfd, the
25 * value of the __u64 being written is added to "count" and a 27 * value of the __u64 being written is added to "count" and a
26 * wakeup is performed on "wqh". A read(2) will return the "count" 28 * wakeup is performed on "wqh". A read(2) will return the "count"
27 * value to userspace, and will reset "count" to zero. The kernel 29 * value to userspace, and will reset "count" to zero. The kernel
28 * size eventfd_signal() also, adds to the "count" counter and 30 * side eventfd_signal() also, adds to the "count" counter and
29 * issue a wakeup. 31 * issue a wakeup.
30 */ 32 */
31 __u64 count; 33 __u64 count;
32 unsigned int flags; 34 unsigned int flags;
33}; 35};
34 36
35/* 37/**
36 * Adds "n" to the eventfd counter "count". Returns "n" in case of 38 * eventfd_signal - Adds @n to the eventfd counter.
37 * success, or a value lower then "n" in case of coutner overflow. 39 * @ctx: [in] Pointer to the eventfd context.
38 * This function is supposed to be called by the kernel in paths 40 * @n: [in] Value of the counter to be added to the eventfd internal counter.
39 * that do not allow sleeping. In this function we allow the counter 41 * The value cannot be negative.
40 * to reach the ULLONG_MAX value, and we signal this as overflow 42 *
41 * condition by returining a POLLERR to poll(2). 43 * This function is supposed to be called by the kernel in paths that do not
44 * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
45 * value, and we signal this as overflow condition by returining a POLLERR
46 * to poll(2).
47 *
48 * Returns @n in case of success, a non-negative number lower than @n in case
49 * of overflow, or the following error codes:
50 *
51 * -EINVAL : The value of @n is negative.
42 */ 52 */
43int eventfd_signal(struct file *file, int n) 53int eventfd_signal(struct eventfd_ctx *ctx, int n)
44{ 54{
45 struct eventfd_ctx *ctx = file->private_data;
46 unsigned long flags; 55 unsigned long flags;
47 56
48 if (n < 0) 57 if (n < 0)
@@ -59,9 +68,45 @@ int eventfd_signal(struct file *file, int n)
59} 68}
60EXPORT_SYMBOL_GPL(eventfd_signal); 69EXPORT_SYMBOL_GPL(eventfd_signal);
61 70
71static void eventfd_free(struct kref *kref)
72{
73 struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
74
75 kfree(ctx);
76}
77
78/**
79 * eventfd_ctx_get - Acquires a reference to the internal eventfd context.
80 * @ctx: [in] Pointer to the eventfd context.
81 *
82 * Returns: In case of success, returns a pointer to the eventfd context.
83 */
84struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx)
85{
86 kref_get(&ctx->kref);
87 return ctx;
88}
89EXPORT_SYMBOL_GPL(eventfd_ctx_get);
90
91/**
92 * eventfd_ctx_put - Releases a reference to the internal eventfd context.
93 * @ctx: [in] Pointer to eventfd context.
94 *
95 * The eventfd context reference must have been previously acquired either
96 * with eventfd_ctx_get() or eventfd_ctx_fdget()).
97 */
98void eventfd_ctx_put(struct eventfd_ctx *ctx)
99{
100 kref_put(&ctx->kref, eventfd_free);
101}
102EXPORT_SYMBOL_GPL(eventfd_ctx_put);
103
62static int eventfd_release(struct inode *inode, struct file *file) 104static int eventfd_release(struct inode *inode, struct file *file)
63{ 105{
64 kfree(file->private_data); 106 struct eventfd_ctx *ctx = file->private_data;
107
108 wake_up_poll(&ctx->wqh, POLLHUP);
109 eventfd_ctx_put(ctx);
65 return 0; 110 return 0;
66} 111}
67 112
@@ -185,6 +230,16 @@ static const struct file_operations eventfd_fops = {
185 .write = eventfd_write, 230 .write = eventfd_write,
186}; 231};
187 232
233/**
234 * eventfd_fget - Acquire a reference of an eventfd file descriptor.
235 * @fd: [in] Eventfd file descriptor.
236 *
237 * Returns a pointer to the eventfd file structure in case of success, or the
238 * following error pointer:
239 *
240 * -EBADF : Invalid @fd file descriptor.
241 * -EINVAL : The @fd file descriptor is not an eventfd file.
242 */
188struct file *eventfd_fget(int fd) 243struct file *eventfd_fget(int fd)
189{ 244{
190 struct file *file; 245 struct file *file;
@@ -201,6 +256,48 @@ struct file *eventfd_fget(int fd)
201} 256}
202EXPORT_SYMBOL_GPL(eventfd_fget); 257EXPORT_SYMBOL_GPL(eventfd_fget);
203 258
259/**
260 * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
261 * @fd: [in] Eventfd file descriptor.
262 *
263 * Returns a pointer to the internal eventfd context, otherwise the error
264 * pointers returned by the following functions:
265 *
266 * eventfd_fget
267 */
268struct eventfd_ctx *eventfd_ctx_fdget(int fd)
269{
270 struct file *file;
271 struct eventfd_ctx *ctx;
272
273 file = eventfd_fget(fd);
274 if (IS_ERR(file))
275 return (struct eventfd_ctx *) file;
276 ctx = eventfd_ctx_get(file->private_data);
277 fput(file);
278
279 return ctx;
280}
281EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);
282
283/**
284 * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
285 * @file: [in] Eventfd file pointer.
286 *
287 * Returns a pointer to the internal eventfd context, otherwise the error
288 * pointer:
289 *
290 * -EINVAL : The @fd file descriptor is not an eventfd file.
291 */
292struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
293{
294 if (file->f_op != &eventfd_fops)
295 return ERR_PTR(-EINVAL);
296
297 return eventfd_ctx_get(file->private_data);
298}
299EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
300
204SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags) 301SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
205{ 302{
206 int fd; 303 int fd;
@@ -217,6 +314,7 @@ SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
217 if (!ctx) 314 if (!ctx)
218 return -ENOMEM; 315 return -ENOMEM;
219 316
317 kref_init(&ctx->kref);
220 init_waitqueue_head(&ctx->wqh); 318 init_waitqueue_head(&ctx->wqh);
221 ctx->count = count; 319 ctx->count = count;
222 ctx->flags = flags; 320 ctx->flags = flags;