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eventpoll: support non-blocking do_epoll_ctl() calls

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Also make it available outside of epoll, along with the helper that
decides if we need to copy the passed in epoll_event.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2020-01-08 15:05:37 -07:00
parent 58e41a44c4
commit 39220e8d4a
2 changed files with 42 additions and 13 deletions
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46
fs/eventpoll.c
View file

@ -354,12 +354,6 @@ static inline struct epitem *ep_item_from_epqueue(poll_table *p)
return container_of(p, struct ep_pqueue, pt)->epi; return container_of(p, struct ep_pqueue, pt)->epi;
} }
/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
static inline int ep_op_has_event(int op)
{
return op != EPOLL_CTL_DEL;
}
/* Initialize the poll safe wake up structure */ /* Initialize the poll safe wake up structure */
static void ep_nested_calls_init(struct nested_calls *ncalls) static void ep_nested_calls_init(struct nested_calls *ncalls)
{ {
@ -2074,7 +2068,20 @@ SYSCALL_DEFINE1(epoll_create, int, size)
return do_epoll_create(0); return do_epoll_create(0);
} }
static int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds) static inline int epoll_mutex_lock(struct mutex *mutex, int depth,
bool nonblock)
{
if (!nonblock) {
mutex_lock_nested(mutex, depth);
return 0;
}
if (mutex_trylock(mutex))
return 0;
return -EAGAIN;
}
int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds,
bool nonblock)
{ {
int error; int error;
int full_check = 0; int full_check = 0;
@ -2145,13 +2152,17 @@ static int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds)
* deep wakeup paths from forming in parallel through multiple * deep wakeup paths from forming in parallel through multiple
* EPOLL_CTL_ADD operations. * EPOLL_CTL_ADD operations.
*/ */
mutex_lock_nested(&ep->mtx, 0); error = epoll_mutex_lock(&ep->mtx, 0, nonblock);
if (error)
goto error_tgt_fput;
if (op == EPOLL_CTL_ADD) { if (op == EPOLL_CTL_ADD) {
if (!list_empty(&f.file->f_ep_links) || if (!list_empty(&f.file->f_ep_links) ||
is_file_epoll(tf.file)) { is_file_epoll(tf.file)) {
full_check = 1;
mutex_unlock(&ep->mtx); mutex_unlock(&ep->mtx);
mutex_lock(&epmutex); error = epoll_mutex_lock(&epmutex, 0, nonblock);
if (error)
goto error_tgt_fput;
full_check = 1;
if (is_file_epoll(tf.file)) { if (is_file_epoll(tf.file)) {
error = -ELOOP; error = -ELOOP;
if (ep_loop_check(ep, tf.file) != 0) { if (ep_loop_check(ep, tf.file) != 0) {
@ -2161,10 +2172,19 @@ static int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds)
} else } else
list_add(&tf.file->f_tfile_llink, list_add(&tf.file->f_tfile_llink,
&tfile_check_list); &tfile_check_list);
mutex_lock_nested(&ep->mtx, 0); error = epoll_mutex_lock(&ep->mtx, 0, nonblock);
if (error) {
out_del:
list_del(&tf.file->f_tfile_llink);
goto error_tgt_fput;
}
if (is_file_epoll(tf.file)) { if (is_file_epoll(tf.file)) {
tep = tf.file->private_data; tep = tf.file->private_data;
mutex_lock_nested(&tep->mtx, 1); error = epoll_mutex_lock(&tep->mtx, 1, nonblock);
if (error) {
mutex_unlock(&ep->mtx);
goto out_del;
}
} }
} }
} }
@ -2233,7 +2253,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
copy_from_user(&epds, event, sizeof(struct epoll_event))) copy_from_user(&epds, event, sizeof(struct epoll_event)))
return -EFAULT; return -EFAULT;
return do_epoll_ctl(epfd, op, fd, &epds); return do_epoll_ctl(epfd, op, fd, &epds, false);
} }
/* /*

9
include/linux/eventpoll.h
View file

@ -61,6 +61,15 @@ static inline void eventpoll_release(struct file *file)
eventpoll_release_file(file); eventpoll_release_file(file);
} }
int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds,
bool nonblock);
/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
static inline int ep_op_has_event(int op)
{
return op != EPOLL_CTL_DEL;
}
#else #else
static inline void eventpoll_init_file(struct file *file) {} static inline void eventpoll_init_file(struct file *file) {}