diff options
Diffstat (limited to 'fs/eventpoll.c')
| -rw-r--r-- | fs/eventpoll.c | 1178 |
1 files changed, 469 insertions, 709 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index b5c7ca58493..1aad34ea61a 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -11,7 +11,6 @@ * */ -#include <linux/module.h> #include <linux/init.h> #include <linux/kernel.h> #include <linux/sched.h> @@ -34,6 +33,7 @@ #include <linux/mount.h> #include <linux/bitops.h> #include <linux/mutex.h> +#include <linux/anon_inodes.h> #include <asm/uaccess.h> #include <asm/system.h> #include <asm/io.h> @@ -41,7 +41,6 @@ #include <asm/atomic.h> #include <asm/semaphore.h> - /* * LOCKING: * There are three level of locking required by epoll : @@ -74,9 +73,6 @@ * a greater scalability. */ - -#define EVENTPOLLFS_MAGIC 0x03111965 /* My birthday should work for this :) */ - #define DEBUG_EPOLL 0 #if DEBUG_EPOLL > 0 @@ -106,7 +102,6 @@ #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) - struct epoll_filefd { struct file *file; int fd; @@ -224,43 +219,6 @@ struct ep_pqueue { struct epitem *epi; }; - - -static void ep_poll_safewake_init(struct poll_safewake *psw); -static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq); -static int ep_getfd(int *efd, struct inode **einode, struct file **efile, - struct eventpoll *ep); -static int ep_alloc(struct eventpoll **pep); -static void ep_free(struct eventpoll *ep); -static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd); -static void ep_use_epitem(struct epitem *epi); -static void ep_release_epitem(struct epitem *epi); -static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, - poll_table *pt); -static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi); -static int ep_insert(struct eventpoll *ep, struct epoll_event *event, - struct file *tfile, int fd); -static int ep_modify(struct eventpoll *ep, struct epitem *epi, - struct epoll_event *event); -static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi); -static int ep_unlink(struct eventpoll *ep, struct epitem *epi); -static int ep_remove(struct eventpoll *ep, struct epitem *epi); -static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key); -static int ep_eventpoll_close(struct inode *inode, struct file *file); -static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait); -static int ep_send_events(struct eventpoll *ep, struct list_head *txlist, - struct epoll_event __user *events, int maxevents); -static int ep_events_transfer(struct eventpoll *ep, - struct epoll_event __user *events, - int maxevents); -static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, - int maxevents, long timeout); -static int eventpollfs_delete_dentry(struct dentry *dentry); -static struct inode *ep_eventpoll_inode(void); -static int eventpollfs_get_sb(struct file_system_type *fs_type, - int flags, const char *dev_name, - void *data, struct vfsmount *mnt); - /* * This semaphore is used to serialize ep_free() and eventpoll_release_file(). */ @@ -275,37 +233,6 @@ static struct kmem_cache *epi_cache __read_mostly; /* Slab cache used to allocate "struct eppoll_entry" */ static struct kmem_cache *pwq_cache __read_mostly; -/* Virtual fs used to allocate inodes for eventpoll files */ -static struct vfsmount *eventpoll_mnt __read_mostly; - -/* File callbacks that implement the eventpoll file behaviour */ -static const struct file_operations eventpoll_fops = { - .release = ep_eventpoll_close, - .poll = ep_eventpoll_poll -}; - -/* - * This is used to register the virtual file system from where - * eventpoll inodes are allocated. - */ -static struct file_system_type eventpoll_fs_type = { - .name = "eventpollfs", - .get_sb = eventpollfs_get_sb, - .kill_sb = kill_anon_super, -}; - -/* Very basic directory entry operations for the eventpoll virtual file system */ -static struct dentry_operations eventpollfs_dentry_operations = { - .d_delete = eventpollfs_delete_dentry, -}; - - - -/* Fast test to see if the file is an evenpoll file */ -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, @@ -374,7 +301,6 @@ static void ep_poll_safewake_init(struct poll_safewake *psw) spin_lock_init(&psw->lock); } - /* * Perform a safe wake up of the poll wait list. The problem is that * with the new callback'd wake up system, it is possible that the @@ -429,399 +355,144 @@ static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq) spin_unlock_irqrestore(&psw->lock, flags); } - /* - * 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. + * This function unregister poll callbacks from the associated file descriptor. + * Since this must be called without holding "ep->lock" the atomic exchange trick + * will protect us from multiple unregister. */ -void eventpoll_release_file(struct file *file) +static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) { - struct list_head *lsthead = &file->f_ep_links; - struct eventpoll *ep; - struct epitem *epi; + int nwait; + struct list_head *lsthead = &epi->pwqlist; + struct eppoll_entry *pwq; - /* - * We don't want to get "file->f_ep_lock" because it is not - * necessary. It is not necessary because we're in the "struct file" - * cleanup path, and this means that noone is using this file anymore. - * The only hit might come from ep_free() but by holding the semaphore - * will correctly serialize the operation. We do need to acquire - * "ep->sem" after "epmutex" because ep_remove() requires it when called - * from anywhere but ep_free(). - */ - mutex_lock(&epmutex); + /* This is called without locks, so we need the atomic exchange */ + nwait = xchg(&epi->nwait, 0); - while (!list_empty(lsthead)) { - epi = list_first_entry(lsthead, struct epitem, fllink); + if (nwait) { + while (!list_empty(lsthead)) { + pwq = list_first_entry(lsthead, struct eppoll_entry, llink); - ep = epi->ep; - list_del_init(&epi->fllink); - down_write(&ep->sem); - ep_remove(ep, epi); - up_write(&ep->sem); + list_del_init(&pwq->llink); + remove_wait_queue(pwq->whead, &pwq->wait); + kmem_cache_free(pwq_cache, pwq); + } } - - mutex_unlock(&epmutex); } - /* - * It opens an eventpoll file descriptor by suggesting a storage of "size" - * file descriptors. The size parameter is just an hint about how to size - * data structures. It won't prevent the user to store more than "size" - * file descriptors inside the epoll interface. It is the kernel part of - * the userspace epoll_create(2). + * Unlink the "struct epitem" from all places it might have been hooked up. + * This function must be called with write IRQ lock on "ep->lock". */ -asmlinkage long sys_epoll_create(int size) +static int ep_unlink(struct eventpoll *ep, struct epitem *epi) { - int error, fd = -1; - struct eventpoll *ep; - struct inode *inode; - struct file *file; - - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n", - current, size)); - - /* - * Sanity check on the size parameter, and create the internal data - * structure ( "struct eventpoll" ). - */ - error = -EINVAL; - if (size <= 0 || (error = ep_alloc(&ep)) != 0) - goto eexit_1; + int error; /* - * Creates all the items needed to setup an eventpoll file. That is, - * a file structure, and inode and a free file descriptor. + * It can happen that this one is called for an item already unlinked. + * The check protect us from doing a double unlink ( crash ). */ - error = ep_getfd(&fd, &inode, &file, ep); - if (error) - goto eexit_2; - - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", - current, size, fd)); - - return fd; - -eexit_2: - ep_free(ep); - kfree(ep); -eexit_1: - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", - current, size, error)); - return error; -} - - -/* - * The following function implements the controller interface for - * the eventpoll file that enables the insertion/removal/change of - * file descriptors inside the interest set. It represents - * the kernel part of the user space epoll_ctl(2). - */ -asmlinkage long -sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event __user *event) -{ - int error; - struct file *file, *tfile; - struct eventpoll *ep; - struct epitem *epi; - struct epoll_event epds; - - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n", - current, epfd, op, fd, event)); - - error = -EFAULT; - if (ep_op_has_event(op) && - copy_from_user(&epds, event, sizeof(struct epoll_event))) - goto eexit_1; - - /* Get the "struct file *" for the eventpoll file */ - error = -EBADF; - file = fget(epfd); - if (!file) - goto eexit_1; - - /* Get the "struct file *" for the target file */ - tfile = fget(fd); - if (!tfile) - goto eexit_2; - - /* The target file descriptor must support poll */ - error = -EPERM; - if (!tfile->f_op || !tfile->f_op->poll) - goto eexit_3; + error = -ENOENT; + if (!ep_rb_linked(&epi->rbn)) + goto error_return; /* - * 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. + * Clear the event mask for the unlinked item. This will avoid item + * notifications to be sent after the unlink operation from inside + * the kernel->userspace event transfer loop. */ - error = -EINVAL; - if (file == tfile || !is_file_epoll(file)) - goto eexit_3; + epi->event.events = 0; /* - * At this point it is safe to assume that the "private_data" contains - * our own data structure. + * At this point is safe to do the job, unlink the item from our rb-tree. + * This operation togheter with the above check closes the door to + * double unlinks. */ - ep = file->private_data; - - down_write(&ep->sem); - - /* Try to lookup the file inside our RB tree */ - epi = ep_find(ep, tfile, fd); - - error = -EINVAL; - switch (op) { - case EPOLL_CTL_ADD: - if (!epi) { - epds.events |= POLLERR | POLLHUP; - - error = ep_insert(ep, &epds, tfile, fd); - } else - error = -EEXIST; - break; - case EPOLL_CTL_DEL: - if (epi) - error = ep_remove(ep, epi); - else - error = -ENOENT; - break; - case EPOLL_CTL_MOD: - if (epi) { - epds.events |= POLLERR | POLLHUP; - error = ep_modify(ep, epi, &epds); - } else - error = -ENOENT; - break; - } + ep_rb_erase(&epi->rbn, &ep->rbr); /* - * The function ep_find() increments the usage count of the structure - * so, if this is not NULL, we need to release it. + * If the item we are going to remove is inside the ready file descriptors + * we want to remove it from this list to avoid stale events. */ - if (epi) - ep_release_epitem(epi); + if (ep_is_linked(&epi->rdllink)) + list_del_init(&epi->rdllink); - up_write(&ep->sem); + error = 0; +error_return: -eexit_3: - fput(tfile); -eexit_2: - fput(file); -eexit_1: - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n", - current, epfd, op, fd, event, error)); + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n", + current, ep, epi->ffd.file, error)); return error; } - /* - * Implement the event wait interface for the eventpoll file. It is the kernel - * part of the user space epoll_wait(2). + * Increment the usage count of the "struct epitem" making it sure + * that the user will have a valid pointer to reference. */ -asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events, - int maxevents, int timeout) +static void ep_use_epitem(struct epitem *epi) { - int error; - struct file *file; - struct eventpoll *ep; - - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n", - current, epfd, events, maxevents, timeout)); - - /* 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))) { - error = -EFAULT; - goto eexit_1; - } - - /* Get the "struct file *" for the eventpoll file */ - error = -EBADF; - file = fget(epfd); - if (!file) - goto eexit_1; - - /* - * 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(file)) - goto eexit_2; - - /* - * At this point it is safe to assume that the "private_data" contains - * our own data structure. - */ - ep = file->private_data; - - /* Time to fish for events ... */ - error = ep_poll(ep, events, maxevents, timeout); - -eexit_2: - fput(file); -eexit_1: - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n", - current, epfd, events, maxevents, timeout, error)); - - return error; + atomic_inc(&epi->usecnt); } - -#ifdef TIF_RESTORE_SIGMASK - /* - * Implement the event wait interface for the eventpoll file. It is the kernel - * part of the user space epoll_pwait(2). + * Decrement ( release ) the usage count by signaling that the user + * has finished using the structure. It might lead to freeing the + * structure itself if the count goes to zero. */ -asmlinkage long sys_epoll_pwait(int epfd, struct epoll_event __user *events, - int maxevents, int timeout, const sigset_t __user *sigmask, - size_t sigsetsize) +static void ep_release_epitem(struct epitem *epi) { - 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; - sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); - sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); - } - - error = sys_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_thread_flag(TIF_RESTORE_SIGMASK); - } else - sigprocmask(SIG_SETMASK, &sigsaved, NULL); - } - - return error; + if (atomic_dec_and_test(&epi->usecnt)) + kmem_cache_free(epi_cache, epi); } -#endif /* #ifdef TIF_RESTORE_SIGMASK */ - - /* - * Creates the file descriptor to be used by the epoll interface. + * Removes a "struct epitem" from the eventpoll RB tree and deallocates + * all the associated resources. */ -static int ep_getfd(int *efd, struct inode **einode, struct file **efile, - struct eventpoll *ep) +static int ep_remove(struct eventpoll *ep, struct epitem *epi) { - struct qstr this; - char name[32]; - struct dentry *dentry; - struct inode *inode; - struct file *file; - int error, fd; - - /* Get an ready to use file */ - error = -ENFILE; - file = get_empty_filp(); - if (!file) - goto eexit_1; - - /* Allocates an inode from the eventpoll file system */ - inode = ep_eventpoll_inode(); - if (IS_ERR(inode)) { - error = PTR_ERR(inode); - goto eexit_2; - } - - /* Allocates a free descriptor to plug the file onto */ - error = get_unused_fd(); - if (error < 0) - goto eexit_3; - fd = error; + int error; + unsigned long flags; + struct file *file = epi->ffd.file; /* - * Link the inode to a directory entry by creating a unique name - * using the inode number. + * Removes poll wait queue hooks. We _have_ to do this without holding + * the "ep->lock" otherwise a deadlock might occur. This because of the + * sequence of the lock acquisition. Here we do "ep->lock" then the wait + * queue head lock when unregistering the wait queue. The wakeup callback + * will run by holding the wait queue head lock and will call our callback + * that will try to get "ep->lock". */ - error = -ENOMEM; - sprintf(name, "[%lu]", inode->i_ino); - this.name = name; - this.len = strlen(name); - this.hash = inode->i_ino; - dentry = d_alloc(eventpoll_mnt->mnt_sb->s_root, &this); - if (!dentry) - goto eexit_4; - dentry->d_op = &eventpollfs_dentry_operations; - d_add(dentry, inode); - file->f_path.mnt = mntget(eventpoll_mnt); - file->f_path.dentry = dentry; - file->f_mapping = inode->i_mapping; - - file->f_pos = 0; - file->f_flags = O_RDONLY; - file->f_op = &eventpoll_fops; - file->f_mode = FMODE_READ; - file->f_version = 0; - file->private_data = ep; - - /* Install the new setup file into the allocated fd. */ - fd_install(fd, file); - - *efd = fd; - *einode = inode; - *efile = file; - return 0; + ep_unregister_pollwait(ep, epi); -eexit_4: - put_unused_fd(fd); -eexit_3: - iput(inode); -eexit_2: - put_filp(file); -eexit_1: - return error; -} + /* Remove the current item from the list of epoll hooks */ + spin_lock(&file->f_ep_lock); + if (ep_is_linked(&epi->fllink)) + list_del_init(&epi->fllink); + spin_unlock(&file->f_ep_lock); + /* We need to acquire the write IRQ lock before calling ep_unlink() */ + write_lock_irqsave(&ep->lock, flags); -static int ep_alloc(struct eventpoll **pep) -{ - struct eventpoll *ep = kzalloc(sizeof(*ep), GFP_KERNEL); + /* Really unlink the item from the RB tree */ + error = ep_unlink(ep, epi); - if (!ep) - return -ENOMEM; + write_unlock_irqrestore(&ep->lock, flags); - rwlock_init(&ep->lock); - init_rwsem(&ep->sem); - init_waitqueue_head(&ep->wq); - init_waitqueue_head(&ep->poll_wait); - INIT_LIST_HEAD(&ep->rdllist); - ep->rbr = RB_ROOT; + if (error) + goto error_return; - *pep = ep; + /* At this point it is safe to free the eventpoll item */ + ep_release_epitem(epi); - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n", - current, ep)); - return 0; -} + error = 0; +error_return: + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p) = %d\n", + current, ep, file, error)); + return error; +} static void ep_free(struct eventpoll *ep) { @@ -865,6 +536,104 @@ static void ep_free(struct eventpoll *ep) mutex_unlock(&epmutex); } +static int ep_eventpoll_release(struct inode *inode, struct file *file) +{ + struct eventpoll *ep = file->private_data; + + if (ep) { + ep_free(ep); + kfree(ep); + } + + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); + return 0; +} + +static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) +{ + unsigned int pollflags = 0; + unsigned long flags; + struct eventpoll *ep = file->private_data; + + /* Insert inside our poll wait queue */ + poll_wait(file, &ep->poll_wait, wait); + + /* Check our condition */ + read_lock_irqsave(&ep->lock, flags); + if (!list_empty(&ep->rdllist)) + pollflags = POLLIN | POLLRDNORM; + read_unlock_irqrestore(&ep->lock, flags); + + return pollflags; +} + +/* File callbacks that implement the eventpoll file behaviour */ +static const struct file_operations eventpoll_fops = { + .release = ep_eventpoll_release, + .poll = ep_eventpoll_poll +}; + +/* Fast test to see if the file is an evenpoll file */ +static inline int is_file_epoll(struct file *f) +{ + return f->f_op == &eventpoll_fops; +} + +/* + * 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 list_head *lsthead = &file->f_ep_links; + struct eventpoll *ep; + struct epitem *epi; + + /* + * We don't want to get "file->f_ep_lock" because it is not + * necessary. It is not necessary because we're in the "struct file" + * cleanup path, and this means that noone is using this file anymore. + * The only hit might come from ep_free() but by holding the semaphore + * will correctly serialize the operation. We do need to acquire + * "ep->sem" after "epmutex" because ep_remove() requires it when called + * from anywhere but ep_free(). + */ + mutex_lock(&epmutex); + + while (!list_empty(lsthead)) { + epi = list_first_entry(lsthead, struct epitem, fllink); + + ep = epi->ep; + list_del_init(&epi->fllink); + down_write(&ep->sem); + ep_remove(ep, epi); + up_write(&ep->sem); + } + + mutex_unlock(&epmutex); +} + +static int ep_alloc(struct eventpoll **pep) +{ + struct eventpoll *ep = kzalloc(sizeof(*ep), GFP_KERNEL); + + if (!ep) + return -ENOMEM; + + rwlock_init(&ep->lock); + init_rwsem(&ep->sem); + init_waitqueue_head(&ep->wq); + init_waitqueue_head(&ep->poll_wait); + INIT_LIST_HEAD(&ep->rdllist); + ep->rbr = RB_ROOT; + + *pep = ep; + + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n", + current, ep)); + return 0; +} /* * Search the file inside the eventpoll tree. It add usage count to @@ -902,30 +671,58 @@ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) return epir; } - /* - * Increment the usage count of the "struct epitem" making it sure - * that the user will have a valid pointer to reference. + * This is the callback that is passed to the wait queue wakeup + * machanism. It is called by the stored file descriptors when they + * have events to report. */ -static void ep_use_epitem(struct epitem *epi) +static int ep_poll_callback(wait_queue_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; - atomic_inc(&epi->usecnt); -} + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n", + current, epi->ffd.file, epi, ep)); + write_lock_irqsave(&ep->lock, flags); -/* - * Decrement ( release ) the usage count by signaling that the user - * has finished using the structure. It might lead to freeing the - * structure itself if the count goes to zero. - */ -static void ep_release_epitem(struct epitem *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 is_disabled; - if (atomic_dec_and_test(&epi->usecnt)) - kmem_cache_free(epi_cache, epi); -} + /* If this file is already in the ready list we exit soon */ + if (ep_is_linked(&epi->rdllink)) + goto is_linked; + list_add_tail(&epi->rdllink, &ep->rdllist); + +is_linked: + /* + * Wake up ( if active ) both the eventpoll wait list and the ->poll() + * wait list. + */ + if (waitqueue_active(&ep->wq)) + __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | + TASK_INTERRUPTIBLE); + if (waitqueue_active(&ep->poll_wait)) + pwake++; + +is_disabled: + write_unlock_irqrestore(&ep->lock, flags); + + /* We have to call this outside the lock */ + if (pwake) + ep_poll_safewake(&psw, &ep->poll_wait); + + return 1; +} /* * This is the callback that is used to add our wait queue to the @@ -950,7 +747,6 @@ static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, } } - static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) { int kcmp; @@ -970,7 +766,6 @@ static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) rb_insert_color(&epi->rbn, &ep->rbr); } - static int ep_insert(struct eventpoll *ep, struct epoll_event *event, struct file *tfile, int fd) { @@ -981,7 +776,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, error = -ENOMEM; if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) - goto eexit_1; + goto error_return; /* Item initialization follow here ... */ ep_rb_initnode(&epi->rbn); @@ -1011,7 +806,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, * high memory pressure. */ if (epi->nwait < 0) - goto eexit_2; + goto error_unregister; /* Add the current item to the list of active epoll hook for this file */ spin_lock(&tfile->f_ep_lock); @@ -1046,7 +841,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, return 0; -eexit_2: +error_unregister: ep_unregister_pollwait(ep, epi); /* @@ -1059,11 +854,10 @@ eexit_2: write_unlock_irqrestore(&ep->lock, flags); kmem_cache_free(epi_cache, epi); -eexit_1: +error_return: return error; } - /* * Modify the interest event mask by dropping an event if the new mask * has a match in the current file status. @@ -1126,216 +920,6 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even return 0; } - -/* - * This function unregister poll callbacks from the associated file descriptor. - * Since this must be called without holding "ep->lock" the atomic exchange trick - * will protect us from multiple unregister. - */ -static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) -{ - int nwait; - struct list_head *lsthead = &epi->pwqlist; - struct eppoll_entry *pwq; - - /* This is called without locks, so we need the atomic exchange */ - nwait = xchg(&epi->nwait, 0); - - if (nwait) { - while (!list_empty(lsthead)) { - pwq = list_first_entry(lsthead, struct eppoll_entry, llink); - - list_del_init(&pwq->llink); - remove_wait_queue(pwq->whead, &pwq->wait); - kmem_cache_free(pwq_cache, pwq); - } - } -} - - -/* - * Unlink the "struct epitem" from all places it might have been hooked up. - * This function must be called with write IRQ lock on "ep->lock". - */ -static int ep_unlink(struct eventpoll *ep, struct epitem *epi) -{ - int error; - - /* - * It can happen that this one is called for an item already unlinked. - * The check protect us from doing a double unlink ( crash ). - */ - error = -ENOENT; - if (!ep_rb_linked(&epi->rbn)) - goto eexit_1; - - /* - * Clear the event mask for the unlinked item. This will avoid item - * notifications to be sent after the unlink operation from inside - * the kernel->userspace event transfer loop. - */ - epi->event.events = 0; - - /* - * At this point is safe to do the job, unlink the item from our rb-tree. - * This operation togheter with the above check closes the door to - * double unlinks. - */ - ep_rb_erase(&epi->rbn, &ep->rbr); - - /* - * If the item we are going to remove is inside the ready file descriptors - * we want to remove it from this list to avoid stale events. - */ - if (ep_is_linked(&epi->rdllink)) - list_del_init(&epi->rdllink); - - error = 0; -eexit_1: - - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n", - current, ep, epi->ffd.file, error)); - - return error; -} - - -/* - * Removes a "struct epitem" from the eventpoll RB tree and deallocates - * all the associated resources. - */ -static int ep_remove(struct eventpoll *ep, struct epitem *epi) -{ - int error; - unsigned long flags; - struct file *file = epi->ffd.file; - - /* - * Removes poll wait queue hooks. We _have_ to do this without holding - * the "ep->lock" otherwise a deadlock might occur. This because of the - * sequence of the lock acquisition. Here we do "ep->lock" then the wait - * queue head lock when unregistering the wait queue. The wakeup callback - * will run by holding the wait queue head lock and will call our callback - * that will try to get "ep->lock". - */ - ep_unregister_pollwait(ep, epi); - - /* Remove the current item from the list of epoll hooks */ - spin_lock(&file->f_ep_lock); - if (ep_is_linked(&epi->fllink)) - list_del_init(&epi->fllink); - spin_unlock(&file->f_ep_lock); - - /* We need to acquire the write IRQ lock before calling ep_unlink() */ - write_lock_irqsave(&ep->lock, flags); - - /* Really unlink the item from the RB tree */ - error = ep_unlink(ep, epi); - - write_unlock_irqrestore(&ep->lock, flags); - - if (error) - goto eexit_1; - - /* At this point it is safe to free the eventpoll item */ - ep_release_epitem(epi); - - error = 0; -eexit_1: - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p) = %d\n", - current, ep, file, error)); - - return error; -} - - -/* - * This is the callback that is passed to the wait queue wakeup - * machanism. It is called by the stored file descriptors when they - * have events to report. - */ -static int ep_poll_callback(wait_queue_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; - - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n", - current, epi->ffd.file, epi, ep)); - - write_lock_irqsave(&ep->lock, flags); - - /* - * 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 is_disabled; - - /* If this file is already in the ready list we exit soon */ - if (ep_is_linked(&epi->rdllink)) - goto is_linked; - - list_add_tail(&epi->rdllink, &ep->rdllist); - -is_linked: - /* - * Wake up ( if active ) both the eventpoll wait list and the ->poll() - * wait list. - */ - if (waitqueue_active(&ep->wq)) - __wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | - TASK_INTERRUPTIBLE); - if (waitqueue_active(&ep->poll_wait)) - pwake++; - -is_disabled: - write_unlock_irqrestore(&ep->lock, flags); - - /* We have to call this outside the lock */ - if (pwake) - ep_poll_safewake(&psw, &ep->poll_wait); - - return 1; -} - - -static int ep_eventpoll_close(struct inode *inode, struct file *file) -{ - struct eventpoll *ep = file->private_data; - - if (ep) { - ep_free(ep); - kfree(ep); - } - - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: close() ep=%p\n", current, ep)); - return 0; -} - - -static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) -{ - unsigned int pollflags = 0; - unsigned long flags; - struct eventpoll *ep = file->private_data; - - /* Insert inside our poll wait queue */ - poll_wait(file, &ep->poll_wait, wait); - - /* Check our condition */ - read_lock_irqsave(&ep->lock, flags); - if (!list_empty(&ep->rdllist)) - pollflags = POLLIN | POLLRDNORM; - read_unlock_irqrestore(&ep->lock, flags); - - return pollflags; -} - - /* * This function is called without holding the "ep->lock" since the call to * __copy_to_user() might sleep, and also f_op->poll() might reenable the IRQ @@ -1447,7 +1031,6 @@ static int ep_send_events(struct eventpoll *ep, struct list_head *txlist, return eventcnt == 0 ? error: eventcnt; } - /* * Perform the transfer of events to user space. */ @@ -1483,7 +1066,6 @@ static int ep_events_transfer(struct eventpoll *ep, return eventcnt; } - static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, int maxevents, long timeout) { @@ -1553,52 +1135,262 @@ retry: return res; } -static int eventpollfs_delete_dentry(struct dentry *dentry) +/* + * It opens an eventpoll file descriptor by suggesting a storage of "size" + * file descriptors. The size parameter is just an hint about how to size + * data structures. It won't prevent the user to store more than "size" + * file descriptors inside the epoll interface. It is the kernel part of + * the userspace epoll_create(2). + */ +asmlinkage long sys_epoll_create(int size) { + int error, fd = -1; + struct eventpoll *ep; + struct inode *inode; + struct file *file; - return 1; + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n", + current, size)); + + /* + * Sanity check on the size parameter, and create the internal data + * structure ( "struct eventpoll" ). + */ + error = -EINVAL; + if (size <= 0 || (error = ep_alloc(&ep)) != 0) + goto error_return; + + /* + * Creates all the items needed to setup an eventpoll file. That is, + * a file structure, and inode and a free file descriptor. + */ + error = anon_inode_getfd(&fd, &inode, &file, "[eventpoll]", + &eventpoll_fops, ep); + if (error) + goto error_free; + + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", + current, size, fd)); + + return fd; + +error_free: + ep_free(ep); + kfree(ep); +error_return: + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", + current, size, error)); + return error; } -static struct inode *ep_eventpoll_inode(void) +/* + * The following function implements the controller interface for + * the eventpoll file that enables the insertion/removal/change of + * file descriptors inside the interest set. It represents + * the kernel part of the user space epoll_ctl(2). + */ +asmlinkage long sys_epoll_ctl(int epfd, int op, int fd, + struct epoll_event __user *event) { - int error = -ENOMEM; - struct inode *inode = new_inode(eventpoll_mnt->mnt_sb); + int error; + struct file *file, *tfile; + struct eventpoll *ep; + struct epitem *epi; + struct epoll_event epds; + + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n", + current, epfd, op, fd, event)); + + error = -EFAULT; + if (ep_op_has_event(op) && + copy_from_user(&epds, event, sizeof(struct epoll_event))) + goto error_return; + + /* Get the "struct file *" for the eventpoll file */ + error = -EBADF; + file = fget(epfd); + if (!file) + goto error_return; + + /* Get the "struct file *" for the target file */ + tfile = fget(fd); + if (!tfile) + goto error_fput; + + /* The target file descriptor must support poll */ + error = -EPERM; + if (!tfile->f_op || !tfile->f_op->poll) + goto error_tgt_fput; + + /* + * 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 (file == tfile || !is_file_epoll(file)) + goto error_tgt_fput; - if (!inode) - goto eexit_1; + /* + * At this point it is safe to assume that the "private_data" contains + * our own data structure. + */ + ep = file->private_data; + + down_write(&ep->sem); - inode->i_fop = &eventpoll_fops; + /* Try to lookup the file inside our RB tree */ + epi = ep_find(ep, tfile, fd); + + error = -EINVAL; + switch (op) { + case EPOLL_CTL_ADD: + if (!epi) { + epds.events |= POLLERR | POLLHUP; + error = ep_insert(ep, &epds, tfile, fd); + } else + error = -EEXIST; + break; + case EPOLL_CTL_DEL: + if (epi) + error = ep_remove(ep, epi); + else + error = -ENOENT; + break; + case EPOLL_CTL_MOD: + if (epi) { + epds.events |= POLLERR | POLLHUP; + error = ep_modify(ep, epi, &epds); + } else + error = -ENOENT; + break; + } /* - * Mark the inode dirty from the very beginning, - * that way it will never be moved to the dirty - * list because mark_inode_dirty() will think - * that it already _is_ on the dirty list. + * The function ep_find() increments the usage count of the structure + * so, if this is not NULL, we need to release it. */ - inode->i_state = I_DIRTY; - inode->i_mode = S_IRUSR | S_IWUSR; - inode->i_uid = current->fsuid; - inode->i_gid = current->fsgid; - inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; - return inode; - -eexit_1: - return ERR_PTR(error); + if (epi) + ep_release_epitem(epi); + up_write(&ep->sem); + +error_tgt_fput: + fput(tfile); +error_fput: + fput(file); +error_return: + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n", + current, epfd, op, fd, event, error)); + + return error; } -static int -eventpollfs_get_sb(struct file_system_type *fs_type, int flags, - const char *dev_name, void *data, struct vfsmount *mnt) +/* + * Implement the event wait interface for the eventpoll file. It is the kernel + * part of the user space epoll_wait(2). + */ +asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events, + int maxevents, int timeout) { - return get_sb_pseudo(fs_type, "eventpoll:", NULL, EVENTPOLLFS_MAGIC, - mnt); + int error; + struct file *file; + struct eventpoll *ep; + + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d)\n", + current, epfd, events, maxevents, timeout)); + + /* 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))) { + error = -EFAULT; + goto error_return; + } + + /* Get the "struct file *" for the eventpoll file */ + error = -EBADF; + file = fget(epfd); + if (!file) + goto error_return; + + /* + * 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(file)) + goto error_fput; + + /* + * At this point it is safe to assume that the "private_data" contains + * our own data structure. + */ + ep = file->private_data; + + /* Time to fish for events ... */ + error = ep_poll(ep, events, maxevents, timeout); + +error_fput: + fput(file); +error_return: + DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_wait(%d, %p, %d, %d) = %d\n", + current, epfd, events, maxevents, timeout, error)); + + return error; } +#ifdef TIF_RESTORE_SIGMASK -static int __init eventpoll_init(void) +/* + * Implement the event wait interface for the eventpoll file. It is the kernel + * part of the user space epoll_pwait(2). + */ +asmlinkage long sys_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; + sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); + sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); + } + + error = sys_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_thread_flag(TIF_RESTORE_SIGMASK); + } else + sigprocmask(SIG_SETMASK, &sigsaved, NULL); + } + + return error; +} +#endif /* #ifdef TIF_RESTORE_SIGMASK */ + +static int __init eventpoll_init(void) +{ mutex_init(&epmutex); /* Initialize the structure used to perform safe poll wait head wake ups */ @@ -1614,39 +1406,7 @@ static int __init eventpoll_init(void) sizeof(struct eppoll_entry), 0, EPI_SLAB_DEBUG|SLAB_PANIC, NULL, NULL); - /* - * Register the virtual file system that will be the source of inodes - * for the eventpoll files - */ - error = register_filesystem(&eventpoll_fs_type); - if (error) - goto epanic; - - /* Mount the above commented virtual file system */ - eventpoll_mnt = kern_mount(&eventpoll_fs_type); - error = PTR_ERR(eventpoll_mnt); - if (IS_ERR(eventpoll_mnt)) - goto epanic; - - DNPRINTK(3, (KERN_INFO "[%p] eventpoll: successfully initialized.\n", - current)); return 0; - -epanic: - panic("eventpoll_init() failed\n"); } +fs_initcall(eventpoll_init); - -static void __exit eventpoll_exit(void) -{ - /* Undo all operations done inside eventpoll_init() */ - unregister_filesystem(&eventpoll_fs_type); - mntput(eventpoll_mnt); - kmem_cache_destroy(pwq_cache); - kmem_cache_destroy(epi_cache); -} - -module_init(eventpoll_init); -module_exit(eventpoll_exit); - -MODULE_LICENSE("GPL"); |