v4.19.13 snapshot.
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
new file mode 100644
index 0000000..42bbe68
--- /dev/null
+++ b/fs/eventpoll.c
@@ -0,0 +1,2338 @@
+/*
+ * fs/eventpoll.c (Efficient event retrieval implementation)
+ * Copyright (C) 2001,...,2009 Davide Libenzi
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Davide Libenzi <davidel@xmailserver.org>
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/sched/signal.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/signal.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/string.h>
+#include <linux/list.h>
+#include <linux/hash.h>
+#include <linux/spinlock.h>
+#include <linux/syscalls.h>
+#include <linux/rbtree.h>
+#include <linux/wait.h>
+#include <linux/eventpoll.h>
+#include <linux/mount.h>
+#include <linux/bitops.h>
+#include <linux/mutex.h>
+#include <linux/anon_inodes.h>
+#include <linux/device.h>
+#include <linux/uaccess.h>
+#include <asm/io.h>
+#include <asm/mman.h>
+#include <linux/atomic.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/compat.h>
+#include <linux/rculist.h>
+#include <net/busy_poll.h>
+
+/*
+ * LOCKING:
+ * There are three level of locking required by epoll :
+ *
+ * 1) epmutex (mutex)
+ * 2) ep->mtx (mutex)
+ * 3) ep->wq.lock (spinlock)
+ *
+ * The acquire order is the one listed above, from 1 to 3.
+ * We need a spinlock (ep->wq.lock) because we manipulate objects
+ * from inside the poll callback, that might be triggered from
+ * a wake_up() that in turn might be called from IRQ context.
+ * So we can't sleep inside the poll callback and hence we need
+ * a spinlock. During the event transfer loop (from kernel to
+ * user space) we could end up sleeping due a copy_to_user(), so
+ * we need a lock that will allow us to sleep. This lock is a
+ * mutex (ep->mtx). It is acquired during the event transfer loop,
+ * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file().
+ * Then we also need a global mutex to serialize eventpoll_release_file()
+ * and ep_free().
+ * This mutex is acquired by ep_free() during the epoll file
+ * cleanup path and it is also acquired by eventpoll_release_file()
+ * if a file has been pushed inside an epoll set and it is then
+ * close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL).
+ * It is also acquired when inserting an epoll fd onto another epoll
+ * fd. We do this so that we walk the epoll tree and ensure that this
+ * insertion does not create a cycle of epoll file descriptors, which
+ * could lead to deadlock. We need a global mutex to prevent two
+ * simultaneous inserts (A into B and B into A) from racing and
+ * constructing a cycle without either insert observing that it is
+ * going to.
+ * It is necessary to acquire multiple "ep->mtx"es at once in the
+ * case when one epoll fd is added to another. In this case, we
+ * always acquire the locks in the order of nesting (i.e. after
+ * epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired
+ * before e2->mtx). Since we disallow cycles of epoll file
+ * descriptors, this ensures that the mutexes are well-ordered. In
+ * order to communicate this nesting to lockdep, when walking a tree
+ * of epoll file descriptors, we use the current recursion depth as
+ * the lockdep subkey.
+ * It is possible to drop the "ep->mtx" and to use the global
+ * mutex "epmutex" (together with "ep->wq.lock") to have it working,
+ * but having "ep->mtx" will make the interface more scalable.
+ * Events that require holding "epmutex" are very rare, while for
+ * normal operations the epoll private "ep->mtx" will guarantee
+ * a better scalability.
+ */
+
+/* Epoll private bits inside the event mask */
+#define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET | EPOLLEXCLUSIVE)
+
+#define EPOLLINOUT_BITS (EPOLLIN | EPOLLOUT)
+
+#define EPOLLEXCLUSIVE_OK_BITS (EPOLLINOUT_BITS | EPOLLERR | EPOLLHUP | \
+ EPOLLWAKEUP | EPOLLET | EPOLLEXCLUSIVE)
+
+/* Maximum number of nesting allowed inside epoll sets */
+#define EP_MAX_NESTS 4
+
+#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
+
+#define EP_UNACTIVE_PTR ((void *) -1L)
+
+#define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry))
+
+struct epoll_filefd {
+ struct file *file;
+ int fd;
+} __packed;
+
+/*
+ * Structure used to track possible nested calls, for too deep recursions
+ * and loop cycles.
+ */
+struct nested_call_node {
+ struct list_head llink;
+ void *cookie;
+ void *ctx;
+};
+
+/*
+ * This structure is used as collector for nested calls, to check for
+ * maximum recursion dept and loop cycles.
+ */
+struct nested_calls {
+ struct list_head tasks_call_list;
+ spinlock_t lock;
+};
+
+/*
+ * Each file descriptor added to the eventpoll interface will
+ * have an entry of this type linked to the "rbr" RB tree.
+ * Avoid increasing the size of this struct, there can be many thousands
+ * of these on a server and we do not want this to take another cache line.
+ */
+struct epitem {
+ union {
+ /* RB tree node links this structure to the eventpoll RB tree */
+ struct rb_node rbn;
+ /* Used to free the struct epitem */
+ struct rcu_head rcu;
+ };
+
+ /* List header used to link this structure to the eventpoll ready list */
+ struct list_head rdllink;
+
+ /*
+ * Works together "struct eventpoll"->ovflist in keeping the
+ * single linked chain of items.
+ */
+ struct epitem *next;
+
+ /* The file descriptor information this item refers to */
+ struct epoll_filefd ffd;
+
+ /* Number of active wait queue attached to poll operations */
+ int nwait;
+
+ /* List containing poll wait queues */
+ struct list_head pwqlist;
+
+ /* The "container" of this item */
+ struct eventpoll *ep;
+
+ /* List header used to link this item to the "struct file" items list */
+ struct list_head fllink;
+
+ /* wakeup_source used when EPOLLWAKEUP is set */
+ struct wakeup_source __rcu *ws;
+
+ /* The structure that describe the interested events and the source fd */
+ struct epoll_event event;
+};
+
+/*
+ * This structure is stored inside the "private_data" member of the file
+ * structure and represents the main data structure for the eventpoll
+ * interface.
+ *
+ * Access to it is protected by the lock inside wq.
+ */
+struct eventpoll {
+ /*
+ * This mutex is used to ensure that files are not removed
+ * while epoll is using them. This is held during the event
+ * collection loop, the file cleanup path, the epoll file exit
+ * code and the ctl operations.
+ */
+ struct mutex mtx;
+
+ /* Wait queue used by sys_epoll_wait() */
+ wait_queue_head_t wq;
+
+ /* Wait queue used by file->poll() */
+ wait_queue_head_t poll_wait;
+
+ /* List of ready file descriptors */
+ struct list_head rdllist;
+
+ /* RB tree root used to store monitored fd structs */
+ struct rb_root_cached rbr;
+
+ /*
+ * This is a single linked list that chains all the "struct epitem" that
+ * happened while transferring ready events to userspace w/out
+ * holding ->wq.lock.
+ */
+ struct epitem *ovflist;
+
+ /* wakeup_source used when ep_scan_ready_list is running */
+ struct wakeup_source *ws;
+
+ /* The user that created the eventpoll descriptor */
+ struct user_struct *user;
+
+ struct file *file;
+
+ /* used to optimize loop detection check */
+ int visited;
+ struct list_head visited_list_link;
+
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ /* used to track busy poll napi_id */
+ unsigned int napi_id;
+#endif
+};
+
+/* Wait structure used by the poll hooks */
+struct eppoll_entry {
+ /* List header used to link this structure to the "struct epitem" */
+ struct list_head llink;
+
+ /* The "base" pointer is set to the container "struct epitem" */
+ struct epitem *base;
+
+ /*
+ * Wait queue item that will be linked to the target file wait
+ * queue head.
+ */
+ wait_queue_entry_t wait;
+
+ /* The wait queue head that linked the "wait" wait queue item */
+ wait_queue_head_t *whead;
+};
+
+/* Wrapper struct used by poll queueing */
+struct ep_pqueue {
+ poll_table pt;
+ struct epitem *epi;
+};
+
+/* Used by the ep_send_events() function as callback private data */
+struct ep_send_events_data {
+ int maxevents;
+ struct epoll_event __user *events;
+ int res;
+};
+
+/*
+ * Configuration options available inside /proc/sys/fs/epoll/
+ */
+/* Maximum number of epoll watched descriptors, per user */
+static long max_user_watches __read_mostly;
+
+/*
+ * This mutex is used to serialize ep_free() and eventpoll_release_file().
+ */
+static DEFINE_MUTEX(epmutex);
+
+/* Used to check for epoll file descriptor inclusion loops */
+static struct nested_calls poll_loop_ncalls;
+
+/* Slab cache used to allocate "struct epitem" */
+static struct kmem_cache *epi_cache __read_mostly;
+
+/* Slab cache used to allocate "struct eppoll_entry" */
+static struct kmem_cache *pwq_cache __read_mostly;
+
+/* Visited nodes during ep_loop_check(), so we can unset them when we finish */
+static LIST_HEAD(visited_list);
+
+/*
+ * List of files with newly added links, where we may need to limit the number
+ * of emanating paths. Protected by the epmutex.
+ */
+static LIST_HEAD(tfile_check_list);
+
+#ifdef CONFIG_SYSCTL
+
+#include <linux/sysctl.h>
+
+static long zero;
+static long long_max = LONG_MAX;
+
+struct ctl_table epoll_table[] = {
+ {
+ .procname = "max_user_watches",
+ .data = &max_user_watches,
+ .maxlen = sizeof(max_user_watches),
+ .mode = 0644,
+ .proc_handler = proc_doulongvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &long_max,
+ },
+ { }
+};
+#endif /* CONFIG_SYSCTL */
+
+static const struct file_operations eventpoll_fops;
+
+static inline int is_file_epoll(struct file *f)
+{
+ return f->f_op == &eventpoll_fops;
+}
+
+/* Setup the structure that is used as key for the RB tree */
+static inline void ep_set_ffd(struct epoll_filefd *ffd,
+ struct file *file, int fd)
+{
+ ffd->file = file;
+ ffd->fd = fd;
+}
+
+/* Compare RB tree keys */
+static inline int ep_cmp_ffd(struct epoll_filefd *p1,
+ struct epoll_filefd *p2)
+{
+ return (p1->file > p2->file ? +1:
+ (p1->file < p2->file ? -1 : p1->fd - p2->fd));
+}
+
+/* Tells us if the item is currently linked */
+static inline int ep_is_linked(struct epitem *epi)
+{
+ return !list_empty(&epi->rdllink);
+}
+
+static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_entry_t *p)
+{
+ return container_of(p, struct eppoll_entry, wait);
+}
+
+/* Get the "struct epitem" from a wait queue pointer */
+static inline struct epitem *ep_item_from_wait(wait_queue_entry_t *p)
+{
+ return container_of(p, struct eppoll_entry, wait)->base;
+}
+
+/* Get the "struct epitem" from an epoll queue wrapper */
+static inline struct epitem *ep_item_from_epqueue(poll_table *p)
+{
+ 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 */
+static void ep_nested_calls_init(struct nested_calls *ncalls)
+{
+ INIT_LIST_HEAD(&ncalls->tasks_call_list);
+ spin_lock_init(&ncalls->lock);
+}
+
+/**
+ * ep_events_available - Checks if ready events might be available.
+ *
+ * @ep: Pointer to the eventpoll context.
+ *
+ * Returns: Returns a value different than zero if ready events are available,
+ * or zero otherwise.
+ */
+static inline int ep_events_available(struct eventpoll *ep)
+{
+ return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR;
+}
+
+#ifdef CONFIG_NET_RX_BUSY_POLL
+static bool ep_busy_loop_end(void *p, unsigned long start_time)
+{
+ struct eventpoll *ep = p;
+
+ return ep_events_available(ep) || busy_loop_timeout(start_time);
+}
+
+/*
+ * Busy poll if globally on and supporting sockets found && no events,
+ * busy loop will return if need_resched or ep_events_available.
+ *
+ * we must do our busy polling with irqs enabled
+ */
+static void ep_busy_loop(struct eventpoll *ep, int nonblock)
+{
+ unsigned int napi_id = READ_ONCE(ep->napi_id);
+
+ if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on())
+ napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep);
+}
+
+static inline void ep_reset_busy_poll_napi_id(struct eventpoll *ep)
+{
+ if (ep->napi_id)
+ ep->napi_id = 0;
+}
+
+/*
+ * Set epoll busy poll NAPI ID from sk.
+ */
+static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
+{
+ struct eventpoll *ep;
+ unsigned int napi_id;
+ struct socket *sock;
+ struct sock *sk;
+ int err;
+
+ if (!net_busy_loop_on())
+ return;
+
+ sock = sock_from_file(epi->ffd.file, &err);
+ if (!sock)
+ return;
+
+ sk = sock->sk;
+ if (!sk)
+ return;
+
+ napi_id = READ_ONCE(sk->sk_napi_id);
+ ep = epi->ep;
+
+ /* Non-NAPI IDs can be rejected
+ * or
+ * Nothing to do if we already have this ID
+ */
+ if (napi_id < MIN_NAPI_ID || napi_id == ep->napi_id)
+ return;
+
+ /* record NAPI ID for use in next busy poll */
+ ep->napi_id = napi_id;
+}
+
+#else
+
+static inline void ep_busy_loop(struct eventpoll *ep, int nonblock)
+{
+}
+
+static inline void ep_reset_busy_poll_napi_id(struct eventpoll *ep)
+{
+}
+
+static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
+{
+}
+
+#endif /* CONFIG_NET_RX_BUSY_POLL */
+
+/**
+ * ep_call_nested - Perform a bound (possibly) nested call, by checking
+ * that the recursion limit is not exceeded, and that
+ * the same nested call (by the meaning of same cookie) is
+ * no re-entered.
+ *
+ * @ncalls: Pointer to the nested_calls structure to be used for this call.
+ * @max_nests: Maximum number of allowed nesting calls.
+ * @nproc: Nested call core function pointer.
+ * @priv: Opaque data to be passed to the @nproc callback.
+ * @cookie: Cookie to be used to identify this nested call.
+ * @ctx: This instance context.
+ *
+ * Returns: Returns the code returned by the @nproc callback, or -1 if
+ * the maximum recursion limit has been exceeded.
+ */
+static int ep_call_nested(struct nested_calls *ncalls, int max_nests,
+ int (*nproc)(void *, void *, int), void *priv,
+ void *cookie, void *ctx)
+{
+ int error, call_nests = 0;
+ unsigned long flags;
+ struct list_head *lsthead = &ncalls->tasks_call_list;
+ struct nested_call_node *tncur;
+ struct nested_call_node tnode;
+
+ spin_lock_irqsave(&ncalls->lock, flags);
+
+ /*
+ * Try to see if the current task is already inside this wakeup call.
+ * We use a list here, since the population inside this set is always
+ * very much limited.
+ */
+ list_for_each_entry(tncur, lsthead, llink) {
+ if (tncur->ctx == ctx &&
+ (tncur->cookie == cookie || ++call_nests > max_nests)) {
+ /*
+ * Ops ... loop detected or maximum nest level reached.
+ * We abort this wake by breaking the cycle itself.
+ */
+ error = -1;
+ goto out_unlock;
+ }
+ }
+
+ /* Add the current task and cookie to the list */
+ tnode.ctx = ctx;
+ tnode.cookie = cookie;
+ list_add(&tnode.llink, lsthead);
+
+ spin_unlock_irqrestore(&ncalls->lock, flags);
+
+ /* Call the nested function */
+ error = (*nproc)(priv, cookie, call_nests);
+
+ /* Remove the current task from the list */
+ spin_lock_irqsave(&ncalls->lock, flags);
+ list_del(&tnode.llink);
+out_unlock:
+ spin_unlock_irqrestore(&ncalls->lock, flags);
+
+ return error;
+}
+
+/*
+ * As described in commit 0ccf831cb lockdep: annotate epoll
+ * the use of wait queues used by epoll is done in a very controlled
+ * manner. Wake ups can nest inside each other, but are never done
+ * with the same locking. For example:
+ *
+ * dfd = socket(...);
+ * efd1 = epoll_create();
+ * efd2 = epoll_create();
+ * epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...);
+ * epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
+ *
+ * When a packet arrives to the device underneath "dfd", the net code will
+ * issue a wake_up() on its poll wake list. Epoll (efd1) has installed a
+ * callback wakeup entry on that queue, and the wake_up() performed by the
+ * "dfd" net code will end up in ep_poll_callback(). At this point epoll
+ * (efd1) notices that it may have some event ready, so it needs to wake up
+ * the waiters on its poll wait list (efd2). So it calls ep_poll_safewake()
+ * that ends up in another wake_up(), after having checked about the
+ * recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to
+ * avoid stack blasting.
+ *
+ * When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle
+ * this special case of epoll.
+ */
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+static struct nested_calls poll_safewake_ncalls;
+
+static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests)
+{
+ unsigned long flags;
+ wait_queue_head_t *wqueue = (wait_queue_head_t *)cookie;
+
+ spin_lock_irqsave_nested(&wqueue->lock, flags, call_nests + 1);
+ wake_up_locked_poll(wqueue, EPOLLIN);
+ spin_unlock_irqrestore(&wqueue->lock, flags);
+
+ return 0;
+}
+
+static void ep_poll_safewake(wait_queue_head_t *wq)
+{
+ int this_cpu = get_cpu();
+
+ ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS,
+ ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu);
+
+ put_cpu();
+}
+
+#else
+
+static void ep_poll_safewake(wait_queue_head_t *wq)
+{
+ wake_up_poll(wq, EPOLLIN);
+}
+
+#endif
+
+static void ep_remove_wait_queue(struct eppoll_entry *pwq)
+{
+ wait_queue_head_t *whead;
+
+ rcu_read_lock();
+ /*
+ * If it is cleared by POLLFREE, it should be rcu-safe.
+ * If we read NULL we need a barrier paired with
+ * smp_store_release() in ep_poll_callback(), otherwise
+ * we rely on whead->lock.
+ */
+ whead = smp_load_acquire(&pwq->whead);
+ if (whead)
+ remove_wait_queue(whead, &pwq->wait);
+ rcu_read_unlock();
+}
+
+/*
+ * This function unregisters poll callbacks from the associated file
+ * descriptor. Must be called with "mtx" held (or "epmutex" if called from
+ * ep_free).
+ */
+static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
+{
+ struct list_head *lsthead = &epi->pwqlist;
+ struct eppoll_entry *pwq;
+
+ while (!list_empty(lsthead)) {
+ pwq = list_first_entry(lsthead, struct eppoll_entry, llink);
+
+ list_del(&pwq->llink);
+ ep_remove_wait_queue(pwq);
+ kmem_cache_free(pwq_cache, pwq);
+ }
+}
+
+/* call only when ep->mtx is held */
+static inline struct wakeup_source *ep_wakeup_source(struct epitem *epi)
+{
+ return rcu_dereference_check(epi->ws, lockdep_is_held(&epi->ep->mtx));
+}
+
+/* call only when ep->mtx is held */
+static inline void ep_pm_stay_awake(struct epitem *epi)
+{
+ struct wakeup_source *ws = ep_wakeup_source(epi);
+
+ if (ws)
+ __pm_stay_awake(ws);
+}
+
+static inline bool ep_has_wakeup_source(struct epitem *epi)
+{
+ return rcu_access_pointer(epi->ws) ? true : false;
+}
+
+/* call when ep->mtx cannot be held (ep_poll_callback) */
+static inline void ep_pm_stay_awake_rcu(struct epitem *epi)
+{
+ struct wakeup_source *ws;
+
+ rcu_read_lock();
+ ws = rcu_dereference(epi->ws);
+ if (ws)
+ __pm_stay_awake(ws);
+ rcu_read_unlock();
+}
+
+/**
+ * ep_scan_ready_list - Scans the ready list in a way that makes possible for
+ * the scan code, to call f_op->poll(). Also allows for
+ * O(NumReady) performance.
+ *
+ * @ep: Pointer to the epoll private data structure.
+ * @sproc: Pointer to the scan callback.
+ * @priv: Private opaque data passed to the @sproc callback.
+ * @depth: The current depth of recursive f_op->poll calls.
+ * @ep_locked: caller already holds ep->mtx
+ *
+ * Returns: The same integer error code returned by the @sproc callback.
+ */
+static __poll_t ep_scan_ready_list(struct eventpoll *ep,
+ __poll_t (*sproc)(struct eventpoll *,
+ struct list_head *, void *),
+ void *priv, int depth, bool ep_locked)
+{
+ __poll_t res;
+ int pwake = 0;
+ struct epitem *epi, *nepi;
+ LIST_HEAD(txlist);
+
+ lockdep_assert_irqs_enabled();
+
+ /*
+ * We need to lock this because we could be hit by
+ * eventpoll_release_file() and epoll_ctl().
+ */
+
+ if (!ep_locked)
+ mutex_lock_nested(&ep->mtx, depth);
+
+ /*
+ * Steal the ready list, and re-init the original one to the
+ * empty list. Also, set ep->ovflist to NULL so that events
+ * happening while looping w/out locks, are not lost. We cannot
+ * have the poll callback to queue directly on ep->rdllist,
+ * because we want the "sproc" callback to be able to do it
+ * in a lockless way.
+ */
+ spin_lock_irq(&ep->wq.lock);
+ list_splice_init(&ep->rdllist, &txlist);
+ ep->ovflist = NULL;
+ spin_unlock_irq(&ep->wq.lock);
+
+ /*
+ * Now call the callback function.
+ */
+ res = (*sproc)(ep, &txlist, priv);
+
+ spin_lock_irq(&ep->wq.lock);
+ /*
+ * During the time we spent inside the "sproc" callback, some
+ * other events might have been queued by the poll callback.
+ * We re-insert them inside the main ready-list here.
+ */
+ for (nepi = ep->ovflist; (epi = nepi) != NULL;
+ nepi = epi->next, epi->next = EP_UNACTIVE_PTR) {
+ /*
+ * We need to check if the item is already in the list.
+ * During the "sproc" callback execution time, items are
+ * queued into ->ovflist but the "txlist" might already
+ * contain them, and the list_splice() below takes care of them.
+ */
+ if (!ep_is_linked(epi)) {
+ list_add_tail(&epi->rdllink, &ep->rdllist);
+ ep_pm_stay_awake(epi);
+ }
+ }
+ /*
+ * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after
+ * releasing the lock, events will be queued in the normal way inside
+ * ep->rdllist.
+ */
+ ep->ovflist = EP_UNACTIVE_PTR;
+
+ /*
+ * Quickly re-inject items left on "txlist".
+ */
+ list_splice(&txlist, &ep->rdllist);
+ __pm_relax(ep->ws);
+
+ if (!list_empty(&ep->rdllist)) {
+ /*
+ * Wake up (if active) both the eventpoll wait list and
+ * the ->poll() wait list (delayed after we release the lock).
+ */
+ if (waitqueue_active(&ep->wq))
+ wake_up_locked(&ep->wq);
+ if (waitqueue_active(&ep->poll_wait))
+ pwake++;
+ }
+ spin_unlock_irq(&ep->wq.lock);
+
+ if (!ep_locked)
+ mutex_unlock(&ep->mtx);
+
+ /* We have to call this outside the lock */
+ if (pwake)
+ ep_poll_safewake(&ep->poll_wait);
+
+ return res;
+}
+
+static void epi_rcu_free(struct rcu_head *head)
+{
+ struct epitem *epi = container_of(head, struct epitem, rcu);
+ kmem_cache_free(epi_cache, epi);
+}
+
+/*
+ * Removes a "struct epitem" from the eventpoll RB tree and deallocates
+ * all the associated resources. Must be called with "mtx" held.
+ */
+static int ep_remove(struct eventpoll *ep, struct epitem *epi)
+{
+ struct file *file = epi->ffd.file;
+
+ lockdep_assert_irqs_enabled();
+
+ /*
+ * Removes poll wait queue hooks.
+ */
+ ep_unregister_pollwait(ep, epi);
+
+ /* Remove the current item from the list of epoll hooks */
+ spin_lock(&file->f_lock);
+ list_del_rcu(&epi->fllink);
+ spin_unlock(&file->f_lock);
+
+ rb_erase_cached(&epi->rbn, &ep->rbr);
+
+ spin_lock_irq(&ep->wq.lock);
+ if (ep_is_linked(epi))
+ list_del_init(&epi->rdllink);
+ spin_unlock_irq(&ep->wq.lock);
+
+ wakeup_source_unregister(ep_wakeup_source(epi));
+ /*
+ * At this point it is safe to free the eventpoll item. Use the union
+ * field epi->rcu, since we are trying to minimize the size of
+ * 'struct epitem'. The 'rbn' field is no longer in use. Protected by
+ * ep->mtx. The rcu read side, reverse_path_check_proc(), does not make
+ * use of the rbn field.
+ */
+ call_rcu(&epi->rcu, epi_rcu_free);
+
+ atomic_long_dec(&ep->user->epoll_watches);
+
+ return 0;
+}
+
+static void ep_free(struct eventpoll *ep)
+{
+ struct rb_node *rbp;
+ struct epitem *epi;
+
+ /* We need to release all tasks waiting for these file */
+ if (waitqueue_active(&ep->poll_wait))
+ ep_poll_safewake(&ep->poll_wait);
+
+ /*
+ * We need to lock this because we could be hit by
+ * eventpoll_release_file() while we're freeing the "struct eventpoll".
+ * We do not need to hold "ep->mtx" here because the epoll file
+ * is on the way to be removed and no one has references to it
+ * anymore. The only hit might come from eventpoll_release_file() but
+ * holding "epmutex" is sufficient here.
+ */
+ mutex_lock(&epmutex);
+
+ /*
+ * Walks through the whole tree by unregistering poll callbacks.
+ */
+ for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
+ epi = rb_entry(rbp, struct epitem, rbn);
+
+ ep_unregister_pollwait(ep, epi);
+ cond_resched();
+ }
+
+ /*
+ * Walks through the whole tree by freeing each "struct epitem". At this
+ * point we are sure no poll callbacks will be lingering around, and also by
+ * holding "epmutex" we can be sure that no file cleanup code will hit
+ * us during this operation. So we can avoid the lock on "ep->wq.lock".
+ * We do not need to lock ep->mtx, either, we only do it to prevent
+ * a lockdep warning.
+ */
+ mutex_lock(&ep->mtx);
+ while ((rbp = rb_first_cached(&ep->rbr)) != NULL) {
+ epi = rb_entry(rbp, struct epitem, rbn);
+ ep_remove(ep, epi);
+ cond_resched();
+ }
+ mutex_unlock(&ep->mtx);
+
+ mutex_unlock(&epmutex);
+ mutex_destroy(&ep->mtx);
+ free_uid(ep->user);
+ wakeup_source_unregister(ep->ws);
+ kfree(ep);
+}
+
+static int ep_eventpoll_release(struct inode *inode, struct file *file)
+{
+ struct eventpoll *ep = file->private_data;
+
+ if (ep)
+ ep_free(ep);
+
+ return 0;
+}
+
+static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
+ void *priv);
+static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
+ poll_table *pt);
+
+/*
+ * 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()
+ * is correctly annotated.
+ */
+static __poll_t ep_item_poll(const struct epitem *epi, poll_table *pt,
+ int depth)
+{
+ struct eventpoll *ep;
+ bool locked;
+
+ 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);
+ locked = pt && (pt->_qproc == ep_ptable_queue_proc);
+
+ return ep_scan_ready_list(epi->ffd.file->private_data,
+ ep_read_events_proc, &depth, depth,
+ locked) & epi->event.events;
+}
+
+static __poll_t ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
+ void *priv)
+{
+ struct epitem *epi, *tmp;
+ poll_table pt;
+ int depth = *(int *)priv;
+
+ init_poll_funcptr(&pt, NULL);
+ depth++;
+
+ list_for_each_entry_safe(epi, tmp, head, rdllink) {
+ if (ep_item_poll(epi, &pt, depth)) {
+ return EPOLLIN | EPOLLRDNORM;
+ } else {
+ /*
+ * Item has been dropped into the ready list by the poll
+ * callback, but it's not actually ready, as far as
+ * caller requested events goes. We can remove it here.
+ */
+ __pm_relax(ep_wakeup_source(epi));
+ list_del_init(&epi->rdllink);
+ }
+ }
+
+ return 0;
+}
+
+static __poll_t ep_eventpoll_poll(struct file *file, poll_table *wait)
+{
+ struct eventpoll *ep = file->private_data;
+ int depth = 0;
+
+ /* 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.
+ */
+ return ep_scan_ready_list(ep, ep_read_events_proc,
+ &depth, depth, false);
+}
+
+#ifdef CONFIG_PROC_FS
+static void ep_show_fdinfo(struct seq_file *m, struct file *f)
+{
+ struct eventpoll *ep = f->private_data;
+ struct rb_node *rbp;
+
+ mutex_lock(&ep->mtx);
+ for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
+ struct epitem *epi = rb_entry(rbp, struct epitem, rbn);
+ struct inode *inode = file_inode(epi->ffd.file);
+
+ seq_printf(m, "tfd: %8d events: %8x data: %16llx "
+ " pos:%lli ino:%lx sdev:%x\n",
+ epi->ffd.fd, epi->event.events,
+ (long long)epi->event.data,
+ (long long)epi->ffd.file->f_pos,
+ inode->i_ino, inode->i_sb->s_dev);
+ if (seq_has_overflowed(m))
+ break;
+ }
+ mutex_unlock(&ep->mtx);
+}
+#endif
+
+/* File callbacks that implement the eventpoll file behaviour */
+static const struct file_operations eventpoll_fops = {
+#ifdef CONFIG_PROC_FS
+ .show_fdinfo = ep_show_fdinfo,
+#endif
+ .release = ep_eventpoll_release,
+ .poll = ep_eventpoll_poll,
+ .llseek = noop_llseek,
+};
+
+/*
+ * This is called from eventpoll_release() to unlink files from the eventpoll
+ * interface. We need to have this facility to cleanup correctly files that are
+ * closed without being removed from the eventpoll interface.
+ */
+void eventpoll_release_file(struct file *file)
+{
+ struct eventpoll *ep;
+ struct epitem *epi, *next;
+
+ /*
+ * We don't want to get "file->f_lock" because it is not
+ * necessary. It is not necessary because we're in the "struct file"
+ * cleanup path, and this means that no one is using this file anymore.
+ * So, for example, epoll_ctl() cannot hit here since if we reach this
+ * point, the file counter already went to zero and fget() would fail.
+ * The only hit might come from ep_free() but by holding the mutex
+ * will correctly serialize the operation. We do need to acquire
+ * "ep->mtx" after "epmutex" because ep_remove() requires it when called
+ * from anywhere but ep_free().
+ *
+ * Besides, ep_remove() acquires the lock, so we can't hold it here.
+ */
+ mutex_lock(&epmutex);
+ list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) {
+ ep = epi->ep;
+ mutex_lock_nested(&ep->mtx, 0);
+ ep_remove(ep, epi);
+ mutex_unlock(&ep->mtx);
+ }
+ mutex_unlock(&epmutex);
+}
+
+static int ep_alloc(struct eventpoll **pep)
+{
+ int error;
+ struct user_struct *user;
+ struct eventpoll *ep;
+
+ user = get_current_user();
+ error = -ENOMEM;
+ ep = kzalloc(sizeof(*ep), GFP_KERNEL);
+ if (unlikely(!ep))
+ goto free_uid;
+
+ mutex_init(&ep->mtx);
+ init_waitqueue_head(&ep->wq);
+ init_waitqueue_head(&ep->poll_wait);
+ INIT_LIST_HEAD(&ep->rdllist);
+ ep->rbr = RB_ROOT_CACHED;
+ ep->ovflist = EP_UNACTIVE_PTR;
+ ep->user = user;
+
+ *pep = ep;
+
+ return 0;
+
+free_uid:
+ free_uid(user);
+ return error;
+}
+
+/*
+ * Search the file inside the eventpoll tree. The RB tree operations
+ * are protected by the "mtx" mutex, and ep_find() must be called with
+ * "mtx" held.
+ */
+static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
+{
+ int kcmp;
+ struct rb_node *rbp;
+ struct epitem *epi, *epir = NULL;
+ struct epoll_filefd ffd;
+
+ ep_set_ffd(&ffd, file, fd);
+ for (rbp = ep->rbr.rb_root.rb_node; rbp; ) {
+ epi = rb_entry(rbp, struct epitem, rbn);
+ kcmp = ep_cmp_ffd(&ffd, &epi->ffd);
+ if (kcmp > 0)
+ rbp = rbp->rb_right;
+ else if (kcmp < 0)
+ rbp = rbp->rb_left;
+ else {
+ epir = epi;
+ break;
+ }
+ }
+
+ return epir;
+}
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff)
+{
+ struct rb_node *rbp;
+ struct epitem *epi;
+
+ for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
+ epi = rb_entry(rbp, struct epitem, rbn);
+ if (epi->ffd.fd == tfd) {
+ if (toff == 0)
+ return epi;
+ else
+ toff--;
+ }
+ cond_resched();
+ }
+
+ return NULL;
+}
+
+struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd,
+ unsigned long toff)
+{
+ struct file *file_raw;
+ struct eventpoll *ep;
+ struct epitem *epi;
+
+ if (!is_file_epoll(file))
+ return ERR_PTR(-EINVAL);
+
+ ep = file->private_data;
+
+ mutex_lock(&ep->mtx);
+ epi = ep_find_tfd(ep, tfd, toff);
+ if (epi)
+ file_raw = epi->ffd.file;
+ else
+ file_raw = ERR_PTR(-ENOENT);
+ mutex_unlock(&ep->mtx);
+
+ return file_raw;
+}
+#endif /* CONFIG_CHECKPOINT_RESTORE */
+
+/*
+ * This is the callback that is passed to the wait queue wakeup
+ * mechanism. It is called by the stored file descriptors when they
+ * have events to report.
+ */
+static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
+{
+ int pwake = 0;
+ unsigned long flags;
+ struct epitem *epi = ep_item_from_wait(wait);
+ struct eventpoll *ep = epi->ep;
+ __poll_t pollflags = key_to_poll(key);
+ int ewake = 0;
+
+ spin_lock_irqsave(&ep->wq.lock, flags);
+
+ ep_set_busy_poll_napi_id(epi);
+
+ /*
+ * If the event mask does not contain any poll(2) event, we consider the
+ * descriptor to be disabled. This condition is likely the effect of the
+ * EPOLLONESHOT bit that disables the descriptor when an event is received,
+ * until the next EPOLL_CTL_MOD will be issued.
+ */
+ if (!(epi->event.events & ~EP_PRIVATE_BITS))
+ goto out_unlock;
+
+ /*
+ * Check the events coming with the callback. At this stage, not
+ * every device reports the events in the "key" parameter of the
+ * callback. We need to be able to handle both cases here, hence the
+ * test for "key" != NULL before the event match test.
+ */
+ if (pollflags && !(pollflags & epi->event.events))
+ goto out_unlock;
+
+ /*
+ * If we are transferring events to userspace, we can hold no locks
+ * (because we're accessing user memory, and because of linux f_op->poll()
+ * semantics). All the events that happen during that period of time are
+ * chained in ep->ovflist and requeued later on.
+ */
+ if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) {
+ if (epi->next == EP_UNACTIVE_PTR) {
+ epi->next = ep->ovflist;
+ ep->ovflist = epi;
+ if (epi->ws) {
+ /*
+ * Activate ep->ws since epi->ws may get
+ * deactivated at any time.
+ */
+ __pm_stay_awake(ep->ws);
+ }
+
+ }
+ goto out_unlock;
+ }
+
+ /* If this file is already in the ready list we exit soon */
+ if (!ep_is_linked(epi)) {
+ list_add_tail(&epi->rdllink, &ep->rdllist);
+ ep_pm_stay_awake_rcu(epi);
+ }
+
+ /*
+ * Wake up ( if active ) both the eventpoll wait list and the ->poll()
+ * wait list.
+ */
+ if (waitqueue_active(&ep->wq)) {
+ if ((epi->event.events & EPOLLEXCLUSIVE) &&
+ !(pollflags & POLLFREE)) {
+ switch (pollflags & EPOLLINOUT_BITS) {
+ case EPOLLIN:
+ if (epi->event.events & EPOLLIN)
+ ewake = 1;
+ break;
+ case EPOLLOUT:
+ if (epi->event.events & EPOLLOUT)
+ ewake = 1;
+ break;
+ case 0:
+ ewake = 1;
+ break;
+ }
+ }
+ wake_up_locked(&ep->wq);
+ }
+ if (waitqueue_active(&ep->poll_wait))
+ pwake++;
+
+out_unlock:
+ spin_unlock_irqrestore(&ep->wq.lock, flags);
+
+ /* We have to call this outside the lock */
+ if (pwake)
+ ep_poll_safewake(&ep->poll_wait);
+
+ if (!(epi->event.events & EPOLLEXCLUSIVE))
+ ewake = 1;
+
+ if (pollflags & POLLFREE) {
+ /*
+ * If we race with ep_remove_wait_queue() it can miss
+ * ->whead = NULL and do another remove_wait_queue() after
+ * us, so we can't use __remove_wait_queue().
+ */
+ list_del_init(&wait->entry);
+ /*
+ * ->whead != NULL protects us from the race with ep_free()
+ * or ep_remove(), ep_remove_wait_queue() takes whead->lock
+ * held by the caller. Once we nullify it, nothing protects
+ * ep/epi or even wait.
+ */
+ smp_store_release(&ep_pwq_from_wait(wait)->whead, NULL);
+ }
+
+ return ewake;
+}
+
+/*
+ * This is the callback that is used to add our wait queue to the
+ * target file wakeup lists.
+ */
+static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
+ poll_table *pt)
+{
+ struct epitem *epi = ep_item_from_epqueue(pt);
+ struct eppoll_entry *pwq;
+
+ if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) {
+ init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
+ pwq->whead = whead;
+ pwq->base = epi;
+ if (epi->event.events & EPOLLEXCLUSIVE)
+ add_wait_queue_exclusive(whead, &pwq->wait);
+ else
+ add_wait_queue(whead, &pwq->wait);
+ list_add_tail(&pwq->llink, &epi->pwqlist);
+ epi->nwait++;
+ } else {
+ /* We have to signal that an error occurred */
+ epi->nwait = -1;
+ }
+}
+
+static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
+{
+ int kcmp;
+ struct rb_node **p = &ep->rbr.rb_root.rb_node, *parent = NULL;
+ struct epitem *epic;
+ bool leftmost = true;
+
+ while (*p) {
+ parent = *p;
+ epic = rb_entry(parent, struct epitem, rbn);
+ kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd);
+ if (kcmp > 0) {
+ p = &parent->rb_right;
+ leftmost = false;
+ } else
+ p = &parent->rb_left;
+ }
+ rb_link_node(&epi->rbn, parent, p);
+ rb_insert_color_cached(&epi->rbn, &ep->rbr, leftmost);
+}
+
+
+
+#define PATH_ARR_SIZE 5
+/*
+ * These are the number paths of length 1 to 5, that we are allowing to emanate
+ * from a single file of interest. For example, we allow 1000 paths of length
+ * 1, to emanate from each file of interest. This essentially represents the
+ * potential wakeup paths, which need to be limited in order to avoid massive
+ * uncontrolled wakeup storms. The common use case should be a single ep which
+ * is connected to n file sources. In this case each file source has 1 path
+ * of length 1. Thus, the numbers below should be more than sufficient. These
+ * path limits are enforced during an EPOLL_CTL_ADD operation, since a modify
+ * and delete can't add additional paths. Protected by the epmutex.
+ */
+static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 };
+static int path_count[PATH_ARR_SIZE];
+
+static int path_count_inc(int nests)
+{
+ /* Allow an arbitrary number of depth 1 paths */
+ if (nests == 0)
+ return 0;
+
+ if (++path_count[nests] > path_limits[nests])
+ return -1;
+ return 0;
+}
+
+static void path_count_init(void)
+{
+ int i;
+
+ for (i = 0; i < PATH_ARR_SIZE; i++)
+ path_count[i] = 0;
+}
+
+static int reverse_path_check_proc(void *priv, void *cookie, int call_nests)
+{
+ int error = 0;
+ struct file *file = priv;
+ struct file *child_file;
+ struct epitem *epi;
+
+ /* CTL_DEL can remove links here, but that can't increase our count */
+ rcu_read_lock();
+ list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) {
+ child_file = epi->ep->file;
+ if (is_file_epoll(child_file)) {
+ if (list_empty(&child_file->f_ep_links)) {
+ if (path_count_inc(call_nests)) {
+ error = -1;
+ break;
+ }
+ } else {
+ error = ep_call_nested(&poll_loop_ncalls,
+ EP_MAX_NESTS,
+ reverse_path_check_proc,
+ child_file, child_file,
+ current);
+ }
+ if (error != 0)
+ break;
+ } else {
+ printk(KERN_ERR "reverse_path_check_proc: "
+ "file is not an ep!\n");
+ }
+ }
+ rcu_read_unlock();
+ return error;
+}
+
+/**
+ * reverse_path_check - The tfile_check_list is list of file *, which have
+ * links that are proposed to be newly added. We need to
+ * make sure that those added links don't add too many
+ * paths such that we will spend all our time waking up
+ * eventpoll objects.
+ *
+ * Returns: Returns zero if the proposed links don't create too many paths,
+ * -1 otherwise.
+ */
+static int reverse_path_check(void)
+{
+ int error = 0;
+ struct file *current_file;
+
+ /* let's call this for all tfiles */
+ list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) {
+ path_count_init();
+ error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
+ reverse_path_check_proc, current_file,
+ current_file, current);
+ if (error)
+ break;
+ }
+ return error;
+}
+
+static int ep_create_wakeup_source(struct epitem *epi)
+{
+ const char *name;
+ struct wakeup_source *ws;
+
+ if (!epi->ep->ws) {
+ epi->ep->ws = wakeup_source_register("eventpoll");
+ if (!epi->ep->ws)
+ return -ENOMEM;
+ }
+
+ name = epi->ffd.file->f_path.dentry->d_name.name;
+ ws = wakeup_source_register(name);
+
+ if (!ws)
+ return -ENOMEM;
+ rcu_assign_pointer(epi->ws, ws);
+
+ return 0;
+}
+
+/* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */
+static noinline void ep_destroy_wakeup_source(struct epitem *epi)
+{
+ struct wakeup_source *ws = ep_wakeup_source(epi);
+
+ RCU_INIT_POINTER(epi->ws, NULL);
+
+ /*
+ * wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is
+ * used internally by wakeup_source_remove, too (called by
+ * wakeup_source_unregister), so we cannot use call_rcu
+ */
+ synchronize_rcu();
+ wakeup_source_unregister(ws);
+}
+
+/*
+ * Must be called with "mtx" held.
+ */
+static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
+ struct file *tfile, int fd, int full_check)
+{
+ int error, pwake = 0;
+ __poll_t revents;
+ long user_watches;
+ struct epitem *epi;
+ struct ep_pqueue epq;
+
+ lockdep_assert_irqs_enabled();
+
+ user_watches = atomic_long_read(&ep->user->epoll_watches);
+ if (unlikely(user_watches >= max_user_watches))
+ return -ENOSPC;
+ if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL)))
+ return -ENOMEM;
+
+ /* Item initialization follow here ... */
+ INIT_LIST_HEAD(&epi->rdllink);
+ INIT_LIST_HEAD(&epi->fllink);
+ INIT_LIST_HEAD(&epi->pwqlist);
+ epi->ep = ep;
+ ep_set_ffd(&epi->ffd, tfile, fd);
+ epi->event = *event;
+ epi->nwait = 0;
+ epi->next = EP_UNACTIVE_PTR;
+ if (epi->event.events & EPOLLWAKEUP) {
+ error = ep_create_wakeup_source(epi);
+ if (error)
+ goto error_create_wakeup_source;
+ } else {
+ RCU_INIT_POINTER(epi->ws, NULL);
+ }
+
+ /* Initialize the poll table using the queue callback */
+ epq.epi = epi;
+ init_poll_funcptr(&epq.pt, ep_ptable_queue_proc);
+
+ /*
+ * Attach the item to the poll hooks and get current event bits.
+ * We can safely use the file* here because its usage count has
+ * been increased by the caller of this function. Note that after
+ * this operation completes, the poll callback can start hitting
+ * the new item.
+ */
+ revents = ep_item_poll(epi, &epq.pt, 1);
+
+ /*
+ * We have to check if something went wrong during the poll wait queue
+ * install process. Namely an allocation for a wait queue failed due
+ * high memory pressure.
+ */
+ error = -ENOMEM;
+ if (epi->nwait < 0)
+ goto error_unregister;
+
+ /* Add the current item to the list of active epoll hook for this file */
+ spin_lock(&tfile->f_lock);
+ list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links);
+ spin_unlock(&tfile->f_lock);
+
+ /*
+ * Add the current item to the RB tree. All RB tree operations are
+ * protected by "mtx", and ep_insert() is called with "mtx" held.
+ */
+ ep_rbtree_insert(ep, epi);
+
+ /* now check if we've created too many backpaths */
+ error = -EINVAL;
+ if (full_check && reverse_path_check())
+ goto error_remove_epi;
+
+ /* We have to drop the new item inside our item list to keep track of it */
+ spin_lock_irq(&ep->wq.lock);
+
+ /* record NAPI ID of new item if present */
+ ep_set_busy_poll_napi_id(epi);
+
+ /* If the file is already "ready" we drop it inside the ready list */
+ if (revents && !ep_is_linked(epi)) {
+ list_add_tail(&epi->rdllink, &ep->rdllist);
+ ep_pm_stay_awake(epi);
+
+ /* Notify waiting tasks that events are available */
+ if (waitqueue_active(&ep->wq))
+ wake_up_locked(&ep->wq);
+ if (waitqueue_active(&ep->poll_wait))
+ pwake++;
+ }
+
+ spin_unlock_irq(&ep->wq.lock);
+
+ atomic_long_inc(&ep->user->epoll_watches);
+
+ /* We have to call this outside the lock */
+ if (pwake)
+ ep_poll_safewake(&ep->poll_wait);
+
+ return 0;
+
+error_remove_epi:
+ spin_lock(&tfile->f_lock);
+ list_del_rcu(&epi->fllink);
+ spin_unlock(&tfile->f_lock);
+
+ rb_erase_cached(&epi->rbn, &ep->rbr);
+
+error_unregister:
+ ep_unregister_pollwait(ep, epi);
+
+ /*
+ * We need to do this because an event could have been arrived on some
+ * allocated wait queue. Note that we don't care about the ep->ovflist
+ * list, since that is used/cleaned only inside a section bound by "mtx".
+ * And ep_insert() is called with "mtx" held.
+ */
+ spin_lock_irq(&ep->wq.lock);
+ if (ep_is_linked(epi))
+ list_del_init(&epi->rdllink);
+ spin_unlock_irq(&ep->wq.lock);
+
+ wakeup_source_unregister(ep_wakeup_source(epi));
+
+error_create_wakeup_source:
+ kmem_cache_free(epi_cache, epi);
+
+ return error;
+}
+
+/*
+ * Modify the interest event mask by dropping an event if the new mask
+ * has a match in the current file status. Must be called with "mtx" held.
+ */
+static int ep_modify(struct eventpoll *ep, struct epitem *epi,
+ const struct epoll_event *event)
+{
+ int pwake = 0;
+ poll_table pt;
+
+ lockdep_assert_irqs_enabled();
+
+ init_poll_funcptr(&pt, NULL);
+
+ /*
+ * Set the new event interest mask before calling f_op->poll();
+ * otherwise we might miss an event that happens between the
+ * f_op->poll() call and the new event set registering.
+ */
+ epi->event.events = event->events; /* need barrier below */
+ epi->event.data = event->data; /* protected by mtx */
+ if (epi->event.events & EPOLLWAKEUP) {
+ if (!ep_has_wakeup_source(epi))
+ ep_create_wakeup_source(epi);
+ } else if (ep_has_wakeup_source(epi)) {
+ ep_destroy_wakeup_source(epi);
+ }
+
+ /*
+ * The following barrier has two effects:
+ *
+ * 1) Flush epi changes above to other CPUs. This ensures
+ * we do not miss events from ep_poll_callback if an
+ * event occurs immediately after we call f_op->poll().
+ * We need this because we did not take ep->wq.lock while
+ * changing epi above (but ep_poll_callback does take
+ * ep->wq.lock).
+ *
+ * 2) We also need to ensure we do not miss _past_ events
+ * when calling f_op->poll(). This barrier also
+ * pairs with the barrier in wq_has_sleeper (see
+ * comments for wq_has_sleeper).
+ *
+ * This barrier will now guarantee ep_poll_callback or f_op->poll
+ * (or both) will notice the readiness of an item.
+ */
+ smp_mb();
+
+ /*
+ * Get current event bits. We can safely use the file* here because
+ * its usage count has been increased by the caller of this function.
+ * If the item is "hot" and it is not registered inside the ready
+ * list, push it inside.
+ */
+ if (ep_item_poll(epi, &pt, 1)) {
+ spin_lock_irq(&ep->wq.lock);
+ if (!ep_is_linked(epi)) {
+ list_add_tail(&epi->rdllink, &ep->rdllist);
+ ep_pm_stay_awake(epi);
+
+ /* Notify waiting tasks that events are available */
+ if (waitqueue_active(&ep->wq))
+ wake_up_locked(&ep->wq);
+ if (waitqueue_active(&ep->poll_wait))
+ pwake++;
+ }
+ spin_unlock_irq(&ep->wq.lock);
+ }
+
+ /* We have to call this outside the lock */
+ if (pwake)
+ ep_poll_safewake(&ep->poll_wait);
+
+ return 0;
+}
+
+static __poll_t ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
+ void *priv)
+{
+ struct ep_send_events_data *esed = priv;
+ __poll_t revents;
+ struct epitem *epi;
+ struct epoll_event __user *uevent;
+ struct wakeup_source *ws;
+ poll_table pt;
+
+ init_poll_funcptr(&pt, NULL);
+
+ /*
+ * We can loop without lock because we are passed a task private list.
+ * Items cannot vanish during the loop because ep_scan_ready_list() is
+ * holding "mtx" during this call.
+ */
+ for (esed->res = 0, uevent = esed->events;
+ !list_empty(head) && esed->res < esed->maxevents;) {
+ epi = list_first_entry(head, struct epitem, rdllink);
+
+ /*
+ * Activate ep->ws before deactivating epi->ws to prevent
+ * triggering auto-suspend here (in case we reactive epi->ws
+ * below).
+ *
+ * This could be rearranged to delay the deactivation of epi->ws
+ * instead, but then epi->ws would temporarily be out of sync
+ * with ep_is_linked().
+ */
+ ws = ep_wakeup_source(epi);
+ if (ws) {
+ if (ws->active)
+ __pm_stay_awake(ep->ws);
+ __pm_relax(ws);
+ }
+
+ list_del_init(&epi->rdllink);
+
+ revents = ep_item_poll(epi, &pt, 1);
+
+ /*
+ * If the event mask intersect the caller-requested one,
+ * deliver the event to userspace. Again, ep_scan_ready_list()
+ * is holding "mtx", so no operations coming from userspace
+ * can change the item.
+ */
+ if (revents) {
+ if (__put_user(revents, &uevent->events) ||
+ __put_user(epi->event.data, &uevent->data)) {
+ list_add(&epi->rdllink, head);
+ ep_pm_stay_awake(epi);
+ if (!esed->res)
+ esed->res = -EFAULT;
+ return 0;
+ }
+ esed->res++;
+ uevent++;
+ if (epi->event.events & EPOLLONESHOT)
+ epi->event.events &= EP_PRIVATE_BITS;
+ else if (!(epi->event.events & EPOLLET)) {
+ /*
+ * If this file has been added with Level
+ * Trigger mode, we need to insert back inside
+ * the ready list, so that the next call to
+ * epoll_wait() will check again the events
+ * availability. At this point, no one can insert
+ * into ep->rdllist besides us. The epoll_ctl()
+ * callers are locked out by
+ * ep_scan_ready_list() holding "mtx" and the
+ * poll callback will queue them in ep->ovflist.
+ */
+ list_add_tail(&epi->rdllink, &ep->rdllist);
+ ep_pm_stay_awake(epi);
+ }
+ }
+ }
+
+ return 0;
+}
+
+static int ep_send_events(struct eventpoll *ep,
+ struct epoll_event __user *events, int maxevents)
+{
+ struct ep_send_events_data esed;
+
+ esed.maxevents = maxevents;
+ esed.events = events;
+
+ ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0, false);
+ return esed.res;
+}
+
+static inline struct timespec64 ep_set_mstimeout(long ms)
+{
+ struct timespec64 now, ts = {
+ .tv_sec = ms / MSEC_PER_SEC,
+ .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC),
+ };
+
+ ktime_get_ts64(&now);
+ return timespec64_add_safe(now, ts);
+}
+
+/**
+ * ep_poll - Retrieves ready events, and delivers them to the caller supplied
+ * event buffer.
+ *
+ * @ep: Pointer to the eventpoll context.
+ * @events: Pointer to the userspace buffer where the ready events should be
+ * stored.
+ * @maxevents: Size (in terms of number of events) of the caller event buffer.
+ * @timeout: Maximum timeout for the ready events fetch operation, in
+ * milliseconds. If the @timeout is zero, the function will not block,
+ * while if the @timeout is less than zero, the function will block
+ * until at least one event has been retrieved (or an error
+ * occurred).
+ *
+ * Returns: Returns the number of ready events which have been fetched, or an
+ * error code, in case of error.
+ */
+static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
+ int maxevents, long timeout)
+{
+ int res = 0, eavail, timed_out = 0;
+ u64 slack = 0;
+ wait_queue_entry_t wait;
+ ktime_t expires, *to = NULL;
+
+ lockdep_assert_irqs_enabled();
+
+ if (timeout > 0) {
+ struct timespec64 end_time = ep_set_mstimeout(timeout);
+
+ slack = select_estimate_accuracy(&end_time);
+ to = &expires;
+ *to = timespec64_to_ktime(end_time);
+ } else if (timeout == 0) {
+ /*
+ * Avoid the unnecessary trip to the wait queue loop, if the
+ * caller specified a non blocking operation.
+ */
+ timed_out = 1;
+ spin_lock_irq(&ep->wq.lock);
+ goto check_events;
+ }
+
+fetch_events:
+
+ if (!ep_events_available(ep))
+ ep_busy_loop(ep, timed_out);
+
+ spin_lock_irq(&ep->wq.lock);
+
+ if (!ep_events_available(ep)) {
+ /*
+ * Busy poll timed out. Drop NAPI ID for now, we can add
+ * it back in when we have moved a socket with a valid NAPI
+ * ID onto the ready list.
+ */
+ ep_reset_busy_poll_napi_id(ep);
+
+ /*
+ * We don't have any available event to return to the caller.
+ * We need to sleep here, and we will be wake up by
+ * ep_poll_callback() when events will become available.
+ */
+ init_waitqueue_entry(&wait, current);
+ __add_wait_queue_exclusive(&ep->wq, &wait);
+
+ for (;;) {
+ /*
+ * We don't want to sleep if the ep_poll_callback() sends us
+ * a wakeup in between. That's why we set the task state
+ * to TASK_INTERRUPTIBLE before doing the checks.
+ */
+ set_current_state(TASK_INTERRUPTIBLE);
+ /*
+ * Always short-circuit for fatal signals to allow
+ * threads to make a timely exit without the chance of
+ * finding more events available and fetching
+ * repeatedly.
+ */
+ if (fatal_signal_pending(current)) {
+ res = -EINTR;
+ break;
+ }
+ if (ep_events_available(ep) || timed_out)
+ break;
+ if (signal_pending(current)) {
+ res = -EINTR;
+ break;
+ }
+
+ spin_unlock_irq(&ep->wq.lock);
+ if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
+ timed_out = 1;
+
+ spin_lock_irq(&ep->wq.lock);
+ }
+
+ __remove_wait_queue(&ep->wq, &wait);
+ __set_current_state(TASK_RUNNING);
+ }
+check_events:
+ /* Is it worth to try to dig for events ? */
+ eavail = ep_events_available(ep);
+
+ spin_unlock_irq(&ep->wq.lock);
+
+ /*
+ * Try to transfer events to user space. In case we get 0 events and
+ * there's still timeout left over, we go trying again in search of
+ * more luck.
+ */
+ if (!res && eavail &&
+ !(res = ep_send_events(ep, events, maxevents)) && !timed_out)
+ goto fetch_events;
+
+ return res;
+}
+
+/**
+ * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested()
+ * API, to verify that adding an epoll file inside another
+ * epoll structure, does not violate the constraints, in
+ * terms of closed loops, or too deep chains (which can
+ * result in excessive stack usage).
+ *
+ * @priv: Pointer to the epoll file to be currently checked.
+ * @cookie: Original cookie for this call. This is the top-of-the-chain epoll
+ * data structure pointer.
+ * @call_nests: Current dept of the @ep_call_nested() call stack.
+ *
+ * Returns: Returns zero if adding the epoll @file inside current epoll
+ * structure @ep does not violate the constraints, or -1 otherwise.
+ */
+static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
+{
+ int error = 0;
+ struct file *file = priv;
+ struct eventpoll *ep = file->private_data;
+ struct eventpoll *ep_tovisit;
+ struct rb_node *rbp;
+ struct epitem *epi;
+
+ mutex_lock_nested(&ep->mtx, call_nests + 1);
+ ep->visited = 1;
+ list_add(&ep->visited_list_link, &visited_list);
+ for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
+ epi = rb_entry(rbp, struct epitem, rbn);
+ if (unlikely(is_file_epoll(epi->ffd.file))) {
+ ep_tovisit = epi->ffd.file->private_data;
+ if (ep_tovisit->visited)
+ continue;
+ error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
+ ep_loop_check_proc, epi->ffd.file,
+ ep_tovisit, current);
+ if (error != 0)
+ break;
+ } else {
+ /*
+ * If we've reached a file that is not associated with
+ * an ep, then we need to check if the newly added
+ * links are going to add too many wakeup paths. We do
+ * this by adding it to the tfile_check_list, if it's
+ * not already there, and calling reverse_path_check()
+ * during ep_insert().
+ */
+ if (list_empty(&epi->ffd.file->f_tfile_llink))
+ list_add(&epi->ffd.file->f_tfile_llink,
+ &tfile_check_list);
+ }
+ }
+ mutex_unlock(&ep->mtx);
+
+ return error;
+}
+
+/**
+ * ep_loop_check - Performs a check to verify that adding an epoll file (@file)
+ * another epoll file (represented by @ep) does not create
+ * closed loops or too deep chains.
+ *
+ * @ep: Pointer to the epoll private data structure.
+ * @file: Pointer to the epoll file to be checked.
+ *
+ * Returns: Returns zero if adding the epoll @file inside current epoll
+ * structure @ep does not violate the constraints, or -1 otherwise.
+ */
+static int ep_loop_check(struct eventpoll *ep, struct file *file)
+{
+ int ret;
+ struct eventpoll *ep_cur, *ep_next;
+
+ ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
+ ep_loop_check_proc, file, ep, current);
+ /* clear visited list */
+ list_for_each_entry_safe(ep_cur, ep_next, &visited_list,
+ visited_list_link) {
+ ep_cur->visited = 0;
+ list_del(&ep_cur->visited_list_link);
+ }
+ return ret;
+}
+
+static void clear_tfile_check_list(void)
+{
+ struct file *file;
+
+ /* first clear the tfile_check_list */
+ while (!list_empty(&tfile_check_list)) {
+ file = list_first_entry(&tfile_check_list, struct file,
+ f_tfile_llink);
+ list_del_init(&file->f_tfile_llink);
+ }
+ INIT_LIST_HEAD(&tfile_check_list);
+}
+
+/*
+ * Open an eventpoll file descriptor.
+ */
+static int do_epoll_create(int flags)
+{
+ int error, fd;
+ struct eventpoll *ep = NULL;
+ struct file *file;
+
+ /* Check the EPOLL_* constant for consistency. */
+ BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC);
+
+ if (flags & ~EPOLL_CLOEXEC)
+ return -EINVAL;
+ /*
+ * Create the internal data structure ("struct eventpoll").
+ */
+ error = ep_alloc(&ep);
+ if (error < 0)
+ return error;
+ /*
+ * Creates all the items needed to setup an eventpoll file. That is,
+ * a file structure and a free file descriptor.
+ */
+ fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC));
+ if (fd < 0) {
+ error = fd;
+ goto out_free_ep;
+ }
+ file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep,
+ O_RDWR | (flags & O_CLOEXEC));
+ if (IS_ERR(file)) {
+ error = PTR_ERR(file);
+ goto out_free_fd;
+ }
+ ep->file = file;
+ fd_install(fd, file);
+ return fd;
+
+out_free_fd:
+ put_unused_fd(fd);
+out_free_ep:
+ ep_free(ep);
+ return error;
+}
+
+SYSCALL_DEFINE1(epoll_create1, int, flags)
+{
+ return do_epoll_create(flags);
+}
+
+SYSCALL_DEFINE1(epoll_create, int, size)
+{
+ if (size <= 0)
+ return -EINVAL;
+
+ return do_epoll_create(0);
+}
+
+/*
+ * The following function implements the controller interface for
+ * the eventpoll file that enables the insertion/removal/change of
+ * file descriptors inside the interest set.
+ */
+SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
+ struct epoll_event __user *, event)
+{
+ int error;
+ int full_check = 0;
+ struct fd f, tf;
+ struct eventpoll *ep;
+ struct epitem *epi;
+ struct epoll_event epds;
+ struct eventpoll *tep = NULL;
+
+ error = -EFAULT;
+ if (ep_op_has_event(op) &&
+ copy_from_user(&epds, event, sizeof(struct epoll_event)))
+ goto error_return;
+
+ error = -EBADF;
+ f = fdget(epfd);
+ if (!f.file)
+ goto error_return;
+
+ /* Get the "struct file *" for the target file */
+ tf = fdget(fd);
+ if (!tf.file)
+ goto error_fput;
+
+ /* The target file descriptor must support poll */
+ error = -EPERM;
+ if (!file_can_poll(tf.file))
+ goto error_tgt_fput;
+
+ /* Check if EPOLLWAKEUP is allowed */
+ if (ep_op_has_event(op))
+ ep_take_care_of_epollwakeup(&epds);
+
+ /*
+ * We have to check that the file structure underneath the file descriptor
+ * the user passed to us _is_ an eventpoll file. And also we do not permit
+ * adding an epoll file descriptor inside itself.
+ */
+ error = -EINVAL;
+ if (f.file == tf.file || !is_file_epoll(f.file))
+ goto error_tgt_fput;
+
+ /*
+ * epoll adds to the wakeup queue at EPOLL_CTL_ADD time only,
+ * so EPOLLEXCLUSIVE is not allowed for a EPOLL_CTL_MOD operation.
+ * Also, we do not currently supported nested exclusive wakeups.
+ */
+ if (ep_op_has_event(op) && (epds.events & EPOLLEXCLUSIVE)) {
+ if (op == EPOLL_CTL_MOD)
+ goto error_tgt_fput;
+ if (op == EPOLL_CTL_ADD && (is_file_epoll(tf.file) ||
+ (epds.events & ~EPOLLEXCLUSIVE_OK_BITS)))
+ goto error_tgt_fput;
+ }
+
+ /*
+ * At this point it is safe to assume that the "private_data" contains
+ * our own data structure.
+ */
+ ep = f.file->private_data;
+
+ /*
+ * When we insert an epoll file descriptor, inside another epoll file
+ * descriptor, there is the change of creating closed loops, which are
+ * better be handled here, than in more critical paths. While we are
+ * checking for loops we also determine the list of files reachable
+ * and hang them on the tfile_check_list, so we can check that we
+ * haven't created too many possible wakeup paths.
+ *
+ * We do not need to take the global 'epumutex' on EPOLL_CTL_ADD when
+ * the epoll file descriptor is attaching directly to a wakeup source,
+ * unless the epoll file descriptor is nested. The purpose of taking the
+ * 'epmutex' on add is to prevent complex toplogies such as loops and
+ * deep wakeup paths from forming in parallel through multiple
+ * EPOLL_CTL_ADD operations.
+ */
+ mutex_lock_nested(&ep->mtx, 0);
+ if (op == EPOLL_CTL_ADD) {
+ if (!list_empty(&f.file->f_ep_links) ||
+ is_file_epoll(tf.file)) {
+ full_check = 1;
+ mutex_unlock(&ep->mtx);
+ mutex_lock(&epmutex);
+ if (is_file_epoll(tf.file)) {
+ error = -ELOOP;
+ if (ep_loop_check(ep, tf.file) != 0) {
+ clear_tfile_check_list();
+ goto error_tgt_fput;
+ }
+ } else
+ list_add(&tf.file->f_tfile_llink,
+ &tfile_check_list);
+ mutex_lock_nested(&ep->mtx, 0);
+ if (is_file_epoll(tf.file)) {
+ tep = tf.file->private_data;
+ mutex_lock_nested(&tep->mtx, 1);
+ }
+ }
+ }
+
+ /*
+ * Try to lookup the file inside our RB tree, Since we grabbed "mtx"
+ * above, we can be sure to be able to use the item looked up by
+ * ep_find() till we release the mutex.
+ */
+ epi = ep_find(ep, tf.file, fd);
+
+ error = -EINVAL;
+ switch (op) {
+ case EPOLL_CTL_ADD:
+ if (!epi) {
+ epds.events |= EPOLLERR | EPOLLHUP;
+ error = ep_insert(ep, &epds, tf.file, fd, full_check);
+ } else
+ error = -EEXIST;
+ if (full_check)
+ clear_tfile_check_list();
+ break;
+ case EPOLL_CTL_DEL:
+ if (epi)
+ error = ep_remove(ep, epi);
+ else
+ error = -ENOENT;
+ break;
+ case EPOLL_CTL_MOD:
+ if (epi) {
+ if (!(epi->event.events & EPOLLEXCLUSIVE)) {
+ epds.events |= EPOLLERR | EPOLLHUP;
+ error = ep_modify(ep, epi, &epds);
+ }
+ } else
+ error = -ENOENT;
+ break;
+ }
+ if (tep != NULL)
+ mutex_unlock(&tep->mtx);
+ mutex_unlock(&ep->mtx);
+
+error_tgt_fput:
+ if (full_check)
+ mutex_unlock(&epmutex);
+
+ fdput(tf);
+error_fput:
+ fdput(f);
+error_return:
+
+ return error;
+}
+
+/*
+ * Implement the event wait interface for the eventpoll file. It is the kernel
+ * part of the user space epoll_wait(2).
+ */
+static int do_epoll_wait(int epfd, struct epoll_event __user *events,
+ int maxevents, int timeout)
+{
+ int error;
+ struct fd f;
+ struct eventpoll *ep;
+
+ /* The maximum number of event must be greater than zero */
+ if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)
+ return -EINVAL;
+
+ /* Verify that the area passed by the user is writeable */
+ if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event)))
+ return -EFAULT;
+
+ /* Get the "struct file *" for the eventpoll file */
+ f = fdget(epfd);
+ if (!f.file)
+ return -EBADF;
+
+ /*
+ * We have to check that the file structure underneath the fd
+ * the user passed to us _is_ an eventpoll file.
+ */
+ error = -EINVAL;
+ if (!is_file_epoll(f.file))
+ goto error_fput;
+
+ /*
+ * At this point it is safe to assume that the "private_data" contains
+ * our own data structure.
+ */
+ ep = f.file->private_data;
+
+ /* Time to fish for events ... */
+ error = ep_poll(ep, events, maxevents, timeout);
+
+error_fput:
+ fdput(f);
+ return error;
+}
+
+SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
+ int, maxevents, int, timeout)
+{
+ return do_epoll_wait(epfd, events, maxevents, timeout);
+}
+
+/*
+ * Implement the event wait interface for the eventpoll file. It is the kernel
+ * part of the user space epoll_pwait(2).
+ */
+SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
+ int, maxevents, int, timeout, const sigset_t __user *, sigmask,
+ size_t, sigsetsize)
+{
+ int error;
+ sigset_t ksigmask, sigsaved;
+
+ /*
+ * If the caller wants a certain signal mask to be set during the wait,
+ * we apply it here.
+ */
+ if (sigmask) {
+ if (sigsetsize != sizeof(sigset_t))
+ return -EINVAL;
+ if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
+ return -EFAULT;
+ sigsaved = current->blocked;
+ set_current_blocked(&ksigmask);
+ }
+
+ error = do_epoll_wait(epfd, events, maxevents, timeout);
+
+ /*
+ * If we changed the signal mask, we need to restore the original one.
+ * In case we've got a signal while waiting, we do not restore the
+ * signal mask yet, and we allow do_signal() to deliver the signal on
+ * the way back to userspace, before the signal mask is restored.
+ */
+ if (sigmask) {
+ if (error == -EINTR) {
+ memcpy(¤t->saved_sigmask, &sigsaved,
+ sizeof(sigsaved));
+ set_restore_sigmask();
+ } else
+ set_current_blocked(&sigsaved);
+ }
+
+ return error;
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd,
+ struct epoll_event __user *, events,
+ int, maxevents, int, timeout,
+ const compat_sigset_t __user *, sigmask,
+ compat_size_t, sigsetsize)
+{
+ long err;
+ sigset_t ksigmask, sigsaved;
+
+ /*
+ * If the caller wants a certain signal mask to be set during the wait,
+ * we apply it here.
+ */
+ if (sigmask) {
+ if (sigsetsize != sizeof(compat_sigset_t))
+ return -EINVAL;
+ if (get_compat_sigset(&ksigmask, sigmask))
+ return -EFAULT;
+ sigsaved = current->blocked;
+ set_current_blocked(&ksigmask);
+ }
+
+ err = do_epoll_wait(epfd, events, maxevents, timeout);
+
+ /*
+ * If we changed the signal mask, we need to restore the original one.
+ * In case we've got a signal while waiting, we do not restore the
+ * signal mask yet, and we allow do_signal() to deliver the signal on
+ * the way back to userspace, before the signal mask is restored.
+ */
+ if (sigmask) {
+ if (err == -EINTR) {
+ memcpy(¤t->saved_sigmask, &sigsaved,
+ sizeof(sigsaved));
+ set_restore_sigmask();
+ } else
+ set_current_blocked(&sigsaved);
+ }
+
+ return err;
+}
+#endif
+
+static int __init eventpoll_init(void)
+{
+ struct sysinfo si;
+
+ si_meminfo(&si);
+ /*
+ * Allows top 4% of lomem to be allocated for epoll watches (per user).
+ */
+ max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) /
+ EP_ITEM_COST;
+ BUG_ON(max_user_watches < 0);
+
+ /*
+ * Initialize the structure used to perform epoll file descriptor
+ * inclusion loops checks.
+ */
+ ep_nested_calls_init(&poll_loop_ncalls);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ /* Initialize the structure used to perform safe poll wait head wake ups */
+ ep_nested_calls_init(&poll_safewake_ncalls);
+#endif
+
+ /*
+ * We can have many thousands of epitems, so prevent this from
+ * using an extra cache line on 64-bit (and smaller) CPUs
+ */
+ BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128);
+
+ /* Allocates slab cache used to allocate "struct epitem" items */
+ epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
+ 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
+
+ /* Allocates slab cache used to allocate "struct eppoll_entry" */
+ pwq_cache = kmem_cache_create("eventpoll_pwq",
+ sizeof(struct eppoll_entry), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL);
+
+ return 0;
+}
+fs_initcall(eventpoll_init);