From 80285b75c683484db4daf02c41009e4424738dd3 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 2 Sep 2020 11:45:57 -0400 Subject: [PATCH] epoll: switch epitem->pwqlist to single-linked list We only traverse it once to destroy all associated eppoll_entry at epitem destruction time. The order of traversal is irrelevant there. Signed-off-by: Al Viro --- fs/eventpoll.c | 51 +++++++++++++++++++++++++-------------------------- 1 file changed, 25 insertions(+), 26 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 4df6112..ae41868 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -128,6 +128,24 @@ struct nested_calls { spinlock_t lock; }; +/* Wait structure used by the poll hooks */ +struct eppoll_entry { + /* List header used to link this structure to the "struct epitem" */ + struct eppoll_entry *next; + + /* 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; +}; + /* * Each file descriptor added to the eventpoll interface will * have an entry of this type linked to the "rbr" RB tree. @@ -158,7 +176,7 @@ struct epitem { int nwait; /* List containing poll wait queues */ - struct list_head pwqlist; + struct eppoll_entry *pwqlist; /* The "container" of this item */ struct eventpoll *ep; @@ -231,24 +249,6 @@ struct eventpoll { #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; @@ -617,13 +617,11 @@ static void ep_remove_wait_queue(struct eppoll_entry *pwq) */ static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) { - struct list_head *lsthead = &epi->pwqlist; + struct eppoll_entry **p = &epi->pwqlist; struct eppoll_entry *pwq; - while (!list_empty(lsthead)) { - pwq = list_first_entry(lsthead, struct eppoll_entry, llink); - - list_del(&pwq->llink); + while ((pwq = *p) != NULL) { + *p = pwq->next; ep_remove_wait_queue(pwq); kmem_cache_free(pwq_cache, pwq); } @@ -1320,7 +1318,8 @@ static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, add_wait_queue_exclusive(whead, &pwq->wait); else add_wait_queue(whead, &pwq->wait); - list_add_tail(&pwq->llink, &epi->pwqlist); + pwq->next = epi->pwqlist; + epi->pwqlist = pwq; epi->nwait++; } else { /* We have to signal that an error occurred */ @@ -1507,7 +1506,7 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event, /* Item initialization follow here ... */ INIT_LIST_HEAD(&epi->rdllink); INIT_LIST_HEAD(&epi->fllink); - INIT_LIST_HEAD(&epi->pwqlist); + epi->pwqlist = NULL; epi->ep = ep; ep_set_ffd(&epi->ffd, tfile, fd); epi->event = *event; -- 2.7.4