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take the common part of ep_eventpoll_poll() and ep_item_poll() into helper

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The only reason why ep_item_poll() can't simply call ep_eventpoll_poll()
(or, better yet, call vfs_poll() in all cases) is that we need to tell
lockdep how deep into the hierarchy of ->mtx we are.  So let's add
a variant of ep_eventpoll_poll() that would take depth explicitly
and turn ep_eventpoll_poll() into wrapper for that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-09-26 18:32:48 -04:00
parent 85353e919f
commit ad9366b136
1 changed files with 27 additions and 30 deletions
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57
fs/eventpoll.c
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@ -732,6 +732,27 @@ static int ep_eventpoll_release(struct inode *inode, struct file *file)
static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
int depth);
static __poll_t __ep_eventpoll_poll(struct file *file, poll_table *wait, int depth)
{
struct eventpoll *ep = file->private_data;
LIST_HEAD(txlist);
__poll_t res;
/* Insert inside our poll wait queue */
poll_wait(file, &ep->poll_wait, wait);
/*
* Proceed to find out if wanted events are really available inside
* the ready list.
*/
mutex_lock_nested(&ep->mtx, depth);
ep_start_scan(ep, &txlist);
res = ep_read_events_proc(ep, &txlist, depth + 1);
ep_done_scan(ep, &txlist);
mutex_unlock(&ep->mtx);
return res;
}
/*
* Differs from ep_eventpoll_poll() in that internal callers already have
* the ep->mtx so we need to start from depth=1, such that mutex_lock_nested()
@ -740,22 +761,14 @@ static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head *head
static __poll_t ep_item_poll(const struct epitem *epi, poll_table *pt,
int depth)
{
struct eventpoll *ep;
LIST_HEAD(txlist);
struct file *file = epi->ffd.file;
__poll_t res;
pt->_key = epi->event.events;
if (!is_file_epoll(epi->ffd.file))
return vfs_poll(epi->ffd.file, pt) & epi->event.events;
ep = epi->ffd.file->private_data;
poll_wait(epi->ffd.file, &ep->poll_wait, pt);
mutex_lock_nested(&ep->mtx, depth);
ep_start_scan(ep, &txlist);
res = ep_read_events_proc(ep, &txlist, depth + 1);
ep_done_scan(ep, &txlist);
mutex_unlock(&ep->mtx);
if (!is_file_epoll(file))
res = vfs_poll(file, pt);
else
res = __ep_eventpoll_poll(file, pt, depth);
return res & epi->event.events;
}
@ -786,23 +799,7 @@ static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head *head
static __poll_t ep_eventpoll_poll(struct file *file, poll_table *wait)
{
struct eventpoll *ep = file->private_data;
LIST_HEAD(txlist);
__poll_t res;
/* Insert inside our poll wait queue */
poll_wait(file, &ep->poll_wait, wait);
/*
* Proceed to find out if wanted events are really available inside
* the ready list.
*/
mutex_lock(&ep->mtx);
ep_start_scan(ep, &txlist);
res = ep_read_events_proc(ep, &txlist, 1);
ep_done_scan(ep, &txlist);
mutex_unlock(&ep->mtx);
return res;
return __ep_eventpoll_poll(file, wait, 0);
}
#ifdef CONFIG_PROC_FS