diff options
| -rw-r--r-- | fs/eventpoll.c | 168 | ||||
| -rw-r--r-- | fs/file_table.c | 1 | ||||
| -rw-r--r-- | include/linux/eventpoll.h | 11 | ||||
| -rw-r--r-- | include/linux/fs.h | 5 |
4 files changed, 129 insertions, 56 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 8f68095c5ce9..d89aead356df 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -215,6 +215,7 @@ struct eventpoll { /* used to optimize loop detection check */ u64 gen; + struct hlist_head refs; #ifdef CONFIG_NET_RX_BUSY_POLL /* used to track busy poll napi_id */ @@ -259,7 +260,45 @@ static struct kmem_cache *pwq_cache __read_mostly; * 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); +struct epitems_head { + struct hlist_head epitems; + struct epitems_head *next; +}; +static struct epitems_head *tfile_check_list = EP_UNACTIVE_PTR; + +static struct kmem_cache *ephead_cache __read_mostly; + +static inline void free_ephead(struct epitems_head *head) +{ + if (head) + kmem_cache_free(ephead_cache, head); +} + +static void list_file(struct file *file) +{ + struct epitems_head *head; + + head = container_of(file->f_ep, struct epitems_head, epitems); + if (!head->next) { + head->next = tfile_check_list; + tfile_check_list = head; + } +} + +static void unlist_file(struct epitems_head *head) +{ + struct epitems_head *to_free = head; + struct hlist_node *p = rcu_dereference(hlist_first_rcu(&head->epitems)); + if (p) { + struct epitem *epi= container_of(p, struct epitem, fllink); + spin_lock(&epi->ffd.file->f_lock); + if (!hlist_empty(&head->epitems)) + to_free = NULL; + head->next = NULL; + spin_unlock(&epi->ffd.file->f_lock); + } + free_ephead(to_free); +} #ifdef CONFIG_SYSCTL @@ -632,6 +671,8 @@ static void epi_rcu_free(struct rcu_head *head) static int ep_remove(struct eventpoll *ep, struct epitem *epi) { struct file *file = epi->ffd.file; + struct epitems_head *to_free; + struct hlist_head *head; lockdep_assert_irqs_enabled(); @@ -642,8 +683,20 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi) /* Remove the current item from the list of epoll hooks */ spin_lock(&file->f_lock); + to_free = NULL; + head = file->f_ep; + if (head->first == &epi->fllink && !epi->fllink.next) { + file->f_ep = NULL; + if (!is_file_epoll(file)) { + struct epitems_head *v; + v = container_of(head, struct epitems_head, epitems); + if (!smp_load_acquire(&v->next)) + to_free = v; + } + } hlist_del_rcu(&epi->fllink); spin_unlock(&file->f_lock); + free_ephead(to_free); rb_erase_cached(&epi->rbn, &ep->rbr); @@ -852,7 +905,11 @@ void eventpoll_release_file(struct file *file) * Besides, ep_remove() acquires the lock, so we can't hold it here. */ mutex_lock(&epmutex); - hlist_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) { + if (unlikely(!file->f_ep)) { + mutex_unlock(&epmutex); + return; + } + hlist_for_each_entry_safe(epi, next, file->f_ep, fllink) { ep = epi->ep; mutex_lock_nested(&ep->mtx, 0); ep_remove(ep, epi); @@ -1248,7 +1305,7 @@ static void path_count_init(void) path_count[i] = 0; } -static int reverse_path_check_proc(struct file *file, int depth) +static int reverse_path_check_proc(struct hlist_head *refs, int depth) { int error = 0; struct epitem *epi; @@ -1257,14 +1314,12 @@ static int reverse_path_check_proc(struct file *file, int depth) return -1; /* CTL_DEL can remove links here, but that can't increase our count */ - hlist_for_each_entry_rcu(epi, &file->f_ep_links, fllink) { - struct file *recepient = epi->ep->file; - if (WARN_ON(!is_file_epoll(recepient))) - continue; - if (hlist_empty(&recepient->f_ep_links)) + hlist_for_each_entry_rcu(epi, refs, fllink) { + struct hlist_head *refs = &epi->ep->refs; + if (hlist_empty(refs)) error = path_count_inc(depth); else - error = reverse_path_check_proc(recepient, depth + 1); + error = reverse_path_check_proc(refs, depth + 1); if (error != 0) break; } @@ -1272,7 +1327,7 @@ static int reverse_path_check_proc(struct file *file, int depth) } /** - * reverse_path_check - The tfile_check_list is list of file *, which have + * reverse_path_check - The tfile_check_list is list of epitem_head, 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 @@ -1283,19 +1338,18 @@ static int reverse_path_check_proc(struct file *file, int depth) */ static int reverse_path_check(void) { - int error = 0; - struct file *current_file; + struct epitems_head *p; - /* let's call this for all tfiles */ - list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) { + for (p = tfile_check_list; p != EP_UNACTIVE_PTR; p = p->next) { + int error; path_count_init(); rcu_read_lock(); - error = reverse_path_check_proc(current_file, 0); + error = reverse_path_check_proc(&p->epitems, 0); rcu_read_unlock(); if (error) - break; + return error; } - return error; + return 0; } static int ep_create_wakeup_source(struct epitem *epi) @@ -1336,6 +1390,39 @@ static noinline void ep_destroy_wakeup_source(struct epitem *epi) wakeup_source_unregister(ws); } +static int attach_epitem(struct file *file, struct epitem *epi) +{ + struct epitems_head *to_free = NULL; + struct hlist_head *head = NULL; + struct eventpoll *ep = NULL; + + if (is_file_epoll(file)) + ep = file->private_data; + + if (ep) { + head = &ep->refs; + } else if (!READ_ONCE(file->f_ep)) { +allocate: + to_free = kmem_cache_zalloc(ephead_cache, GFP_KERNEL); + if (!to_free) + return -ENOMEM; + head = &to_free->epitems; + } + spin_lock(&file->f_lock); + if (!file->f_ep) { + if (unlikely(!head)) { + spin_unlock(&file->f_lock); + goto allocate; + } + file->f_ep = head; + to_free = NULL; + } + hlist_add_head_rcu(&epi->fllink, file->f_ep); + spin_unlock(&file->f_lock); + free_ephead(to_free); + return 0; +} + /* * Must be called with "mtx" held. */ @@ -1367,19 +1454,21 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event, epi->event = *event; epi->next = EP_UNACTIVE_PTR; - atomic_long_inc(&ep->user->epoll_watches); - if (tep) mutex_lock_nested(&tep->mtx, 1); /* Add the current item to the list of active epoll hook for this file */ - spin_lock(&tfile->f_lock); - hlist_add_head_rcu(&epi->fllink, &tfile->f_ep_links); - spin_unlock(&tfile->f_lock); - if (full_check && !tep) { - get_file(tfile); - list_add(&tfile->f_tfile_llink, &tfile_check_list); + if (unlikely(attach_epitem(tfile, epi) < 0)) { + kmem_cache_free(epi_cache, epi); + if (tep) + mutex_unlock(&tep->mtx); + return -ENOMEM; } + if (full_check && !tep) + list_file(tfile); + + atomic_long_inc(&ep->user->epoll_watches); + /* * Add the current item to the RB tree. All RB tree operations are * protected by "mtx", and ep_insert() is called with "mtx" held. @@ -1813,11 +1902,7 @@ static int ep_loop_check_proc(struct eventpoll *ep, int depth) * not already there, and calling reverse_path_check() * during ep_insert(). */ - if (list_empty(&epi->ffd.file->f_tfile_llink)) { - if (get_file_rcu(epi->ffd.file)) - list_add(&epi->ffd.file->f_tfile_llink, - &tfile_check_list); - } + list_file(epi->ffd.file); } } mutex_unlock(&ep->mtx); @@ -1844,16 +1929,13 @@ static int ep_loop_check(struct eventpoll *ep, struct eventpoll *to) 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); - fput(file); + rcu_read_lock(); + while (tfile_check_list != EP_UNACTIVE_PTR) { + struct epitems_head *head = tfile_check_list; + tfile_check_list = head->next; + unlist_file(head); } - INIT_LIST_HEAD(&tfile_check_list); + rcu_read_unlock(); } /* @@ -2003,9 +2085,8 @@ int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds, if (error) goto error_tgt_fput; if (op == EPOLL_CTL_ADD) { - if (!hlist_empty(&f.file->f_ep_links) || - ep->gen == loop_check_gen || - is_file_epoll(tf.file)) { + if (READ_ONCE(f.file->f_ep) || ep->gen == loop_check_gen || + is_file_epoll(tf.file)) { mutex_unlock(&ep->mtx); error = epoll_mutex_lock(&epmutex, 0, nonblock); if (error) @@ -2216,6 +2297,9 @@ static int __init eventpoll_init(void) pwq_cache = kmem_cache_create("eventpoll_pwq", sizeof(struct eppoll_entry), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL); + ephead_cache = kmem_cache_create("ep_head", + sizeof(struct epitems_head), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL); + return 0; } fs_initcall(eventpoll_init); diff --git a/fs/file_table.c b/fs/file_table.c index 709ada3151da..45437f8e1003 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -113,7 +113,6 @@ static struct file *__alloc_file(int flags, const struct cred *cred) rwlock_init(&f->f_owner.lock); spin_lock_init(&f->f_lock); mutex_init(&f->f_pos_lock); - eventpoll_init_file(f); f->f_flags = flags; f->f_mode = OPEN_FMODE(flags); /* f->f_version: 0 */ diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h index 4e215ccfa792..0350393465d4 100644 --- a/include/linux/eventpoll.h +++ b/include/linux/eventpoll.h @@ -22,14 +22,6 @@ struct file; struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff); #endif -/* Used to initialize the epoll bits inside the "struct file" */ -static inline void eventpoll_init_file(struct file *file) -{ - INIT_HLIST_HEAD(&file->f_ep_links); - INIT_LIST_HEAD(&file->f_tfile_llink); -} - - /* Used to release the epoll bits inside the "struct file" */ void eventpoll_release_file(struct file *file); @@ -50,7 +42,7 @@ static inline void eventpoll_release(struct file *file) * because the file in on the way to be removed and nobody ( but * eventpoll ) has still a reference to this file. */ - if (likely(hlist_empty(&file->f_ep_links))) + if (likely(!file->f_ep)) return; /* @@ -72,7 +64,6 @@ static inline int ep_op_has_event(int op) #else -static inline void eventpoll_init_file(struct file *file) {} static inline void eventpoll_release(struct file *file) {} #endif diff --git a/include/linux/fs.h b/include/linux/fs.h index b484ba0e474a..993c540e3b77 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -923,7 +923,7 @@ struct file { const struct file_operations *f_op; /* - * Protects f_ep_links, f_flags. + * Protects f_ep, f_flags. * Must not be taken from IRQ context. */ spinlock_t f_lock; @@ -946,8 +946,7 @@ struct file { #ifdef CONFIG_EPOLL /* Used by fs/eventpoll.c to link all the hooks to this file */ - struct hlist_head f_ep_links; - struct list_head f_tfile_llink; + struct hlist_head *f_ep; #endif /* #ifdef CONFIG_EPOLL */ struct address_space *f_mapping; errseq_t f_wb_err; |