![Theodore Ts'o](/assets/img/avatar_default.png)
This eliminates the i_blksize field from struct inode. Filesystems that want to provide a per-inode st_blksize can do so by providing their own getattr routine instead of using the generic_fillattr() function. Note that some filesystems were providing pretty much random (and incorrect) values for i_blksize. [bunk@stusta.de: cleanup] [akpm@osdl.org: generic_fillattr() fix] Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
1664 lines
44 KiB
C
1664 lines
44 KiB
C
/*
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* fs/eventpoll.c ( Efficent event polling implementation )
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* Copyright (C) 2001,...,2006 Davide Libenzi
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* Davide Libenzi <davidel@xmailserver.org>
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*
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/signal.h>
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#include <linux/errno.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/poll.h>
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#include <linux/smp_lock.h>
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#include <linux/string.h>
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#include <linux/list.h>
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#include <linux/hash.h>
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#include <linux/spinlock.h>
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#include <linux/syscalls.h>
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#include <linux/rwsem.h>
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#include <linux/rbtree.h>
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#include <linux/wait.h>
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#include <linux/eventpoll.h>
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#include <linux/mount.h>
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#include <linux/bitops.h>
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#include <linux/mutex.h>
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#include <asm/uaccess.h>
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#include <asm/system.h>
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#include <asm/io.h>
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#include <asm/mman.h>
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#include <asm/atomic.h>
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#include <asm/semaphore.h>
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/*
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* LOCKING:
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* There are three level of locking required by epoll :
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*
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* 1) epmutex (mutex)
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* 2) ep->sem (rw_semaphore)
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* 3) ep->lock (rw_lock)
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*
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* The acquire order is the one listed above, from 1 to 3.
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* We need a spinlock (ep->lock) because we manipulate objects
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* from inside the poll callback, that might be triggered from
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* a wake_up() that in turn might be called from IRQ context.
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* So we can't sleep inside the poll callback and hence we need
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* a spinlock. During the event transfer loop (from kernel to
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* user space) we could end up sleeping due a copy_to_user(), so
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* we need a lock that will allow us to sleep. This lock is a
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* read-write semaphore (ep->sem). It is acquired on read during
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* the event transfer loop and in write during epoll_ctl(EPOLL_CTL_DEL)
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* and during eventpoll_release_file(). Then we also need a global
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* semaphore to serialize eventpoll_release_file() and ep_free().
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* This semaphore is acquired by ep_free() during the epoll file
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* cleanup path and it is also acquired by eventpoll_release_file()
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* if a file has been pushed inside an epoll set and it is then
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* close()d without a previous call toepoll_ctl(EPOLL_CTL_DEL).
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* It is possible to drop the "ep->sem" and to use the global
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* semaphore "epmutex" (together with "ep->lock") to have it working,
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* but having "ep->sem" will make the interface more scalable.
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* Events that require holding "epmutex" are very rare, while for
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* normal operations the epoll private "ep->sem" will guarantee
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* a greater scalability.
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*/
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#define EVENTPOLLFS_MAGIC 0x03111965 /* My birthday should work for this :) */
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#define DEBUG_EPOLL 0
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#if DEBUG_EPOLL > 0
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#define DPRINTK(x) printk x
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#define DNPRINTK(n, x) do { if ((n) <= DEBUG_EPOLL) printk x; } while (0)
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#else /* #if DEBUG_EPOLL > 0 */
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#define DPRINTK(x) (void) 0
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#define DNPRINTK(n, x) (void) 0
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#endif /* #if DEBUG_EPOLL > 0 */
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#define DEBUG_EPI 0
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#if DEBUG_EPI != 0
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#define EPI_SLAB_DEBUG (SLAB_DEBUG_FREE | SLAB_RED_ZONE /* | SLAB_POISON */)
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#else /* #if DEBUG_EPI != 0 */
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#define EPI_SLAB_DEBUG 0
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#endif /* #if DEBUG_EPI != 0 */
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/* Epoll private bits inside the event mask */
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#define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET)
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/* Maximum number of poll wake up nests we are allowing */
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#define EP_MAX_POLLWAKE_NESTS 4
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/* Maximum msec timeout value storeable in a long int */
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#define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ)
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struct epoll_filefd {
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struct file *file;
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int fd;
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};
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/*
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* Node that is linked into the "wake_task_list" member of the "struct poll_safewake".
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* It is used to keep track on all tasks that are currently inside the wake_up() code
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* to 1) short-circuit the one coming from the same task and same wait queue head
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* ( loop ) 2) allow a maximum number of epoll descriptors inclusion nesting
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* 3) let go the ones coming from other tasks.
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*/
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struct wake_task_node {
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struct list_head llink;
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struct task_struct *task;
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wait_queue_head_t *wq;
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};
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/*
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* This is used to implement the safe poll wake up avoiding to reenter
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* the poll callback from inside wake_up().
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*/
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struct poll_safewake {
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struct list_head wake_task_list;
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spinlock_t lock;
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};
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/*
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* This structure is stored inside the "private_data" member of the file
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* structure and rapresent the main data sructure for the eventpoll
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* interface.
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*/
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struct eventpoll {
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/* Protect the this structure access */
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rwlock_t lock;
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/*
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* This semaphore is used to ensure that files are not removed
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* while epoll is using them. This is read-held during the event
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* collection loop and it is write-held during the file cleanup
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* path, the epoll file exit code and the ctl operations.
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*/
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struct rw_semaphore sem;
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/* Wait queue used by sys_epoll_wait() */
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wait_queue_head_t wq;
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/* Wait queue used by file->poll() */
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wait_queue_head_t poll_wait;
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/* List of ready file descriptors */
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struct list_head rdllist;
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/* RB-Tree root used to store monitored fd structs */
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struct rb_root rbr;
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};
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/* Wait structure used by the poll hooks */
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struct eppoll_entry {
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/* List header used to link this structure to the "struct epitem" */
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struct list_head llink;
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/* The "base" pointer is set to the container "struct epitem" */
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void *base;
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/*
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* Wait queue item that will be linked to the target file wait
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* queue head.
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*/
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wait_queue_t wait;
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/* The wait queue head that linked the "wait" wait queue item */
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wait_queue_head_t *whead;
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};
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/*
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* Each file descriptor added to the eventpoll interface will
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* have an entry of this type linked to the hash.
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*/
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struct epitem {
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/* RB-Tree node used to link this structure to the eventpoll rb-tree */
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struct rb_node rbn;
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/* List header used to link this structure to the eventpoll ready list */
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struct list_head rdllink;
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/* The file descriptor information this item refers to */
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struct epoll_filefd ffd;
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/* Number of active wait queue attached to poll operations */
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int nwait;
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/* List containing poll wait queues */
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struct list_head pwqlist;
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/* The "container" of this item */
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struct eventpoll *ep;
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/* The structure that describe the interested events and the source fd */
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struct epoll_event event;
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/*
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* Used to keep track of the usage count of the structure. This avoids
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* that the structure will desappear from underneath our processing.
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*/
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atomic_t usecnt;
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/* List header used to link this item to the "struct file" items list */
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struct list_head fllink;
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/* List header used to link the item to the transfer list */
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struct list_head txlink;
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/*
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* This is used during the collection/transfer of events to userspace
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* to pin items empty events set.
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*/
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unsigned int revents;
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};
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/* Wrapper struct used by poll queueing */
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struct ep_pqueue {
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poll_table pt;
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struct epitem *epi;
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};
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static void ep_poll_safewake_init(struct poll_safewake *psw);
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static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq);
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static int ep_getfd(int *efd, struct inode **einode, struct file **efile,
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struct eventpoll *ep);
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static int ep_alloc(struct eventpoll **pep);
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static void ep_free(struct eventpoll *ep);
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static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd);
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static void ep_use_epitem(struct epitem *epi);
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static void ep_release_epitem(struct epitem *epi);
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static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
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poll_table *pt);
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static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi);
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static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
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struct file *tfile, int fd);
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static int ep_modify(struct eventpoll *ep, struct epitem *epi,
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struct epoll_event *event);
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static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi);
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static int ep_unlink(struct eventpoll *ep, struct epitem *epi);
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static int ep_remove(struct eventpoll *ep, struct epitem *epi);
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static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key);
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static int ep_eventpoll_close(struct inode *inode, struct file *file);
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static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait);
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static int ep_collect_ready_items(struct eventpoll *ep,
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struct list_head *txlist, int maxevents);
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static int ep_send_events(struct eventpoll *ep, struct list_head *txlist,
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struct epoll_event __user *events);
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static void ep_reinject_items(struct eventpoll *ep, struct list_head *txlist);
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static int ep_events_transfer(struct eventpoll *ep,
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struct epoll_event __user *events,
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int maxevents);
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static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
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int maxevents, long timeout);
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static int eventpollfs_delete_dentry(struct dentry *dentry);
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static struct inode *ep_eventpoll_inode(void);
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static int eventpollfs_get_sb(struct file_system_type *fs_type,
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int flags, const char *dev_name,
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void *data, struct vfsmount *mnt);
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/*
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* This semaphore is used to serialize ep_free() and eventpoll_release_file().
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*/
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static struct mutex epmutex;
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/* Safe wake up implementation */
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static struct poll_safewake psw;
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/* Slab cache used to allocate "struct epitem" */
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static kmem_cache_t *epi_cache __read_mostly;
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/* Slab cache used to allocate "struct eppoll_entry" */
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static kmem_cache_t *pwq_cache __read_mostly;
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/* Virtual fs used to allocate inodes for eventpoll files */
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static struct vfsmount *eventpoll_mnt __read_mostly;
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/* File callbacks that implement the eventpoll file behaviour */
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static const struct file_operations eventpoll_fops = {
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.release = ep_eventpoll_close,
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.poll = ep_eventpoll_poll
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};
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/*
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* This is used to register the virtual file system from where
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* eventpoll inodes are allocated.
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*/
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static struct file_system_type eventpoll_fs_type = {
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.name = "eventpollfs",
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.get_sb = eventpollfs_get_sb,
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.kill_sb = kill_anon_super,
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};
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/* Very basic directory entry operations for the eventpoll virtual file system */
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static struct dentry_operations eventpollfs_dentry_operations = {
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.d_delete = eventpollfs_delete_dentry,
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};
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/* Fast test to see if the file is an evenpoll file */
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static inline int is_file_epoll(struct file *f)
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{
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return f->f_op == &eventpoll_fops;
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}
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/* Setup the structure that is used as key for the rb-tree */
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static inline void ep_set_ffd(struct epoll_filefd *ffd,
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struct file *file, int fd)
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{
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ffd->file = file;
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ffd->fd = fd;
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}
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/* Compare rb-tree keys */
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static inline int ep_cmp_ffd(struct epoll_filefd *p1,
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struct epoll_filefd *p2)
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{
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return (p1->file > p2->file ? +1:
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(p1->file < p2->file ? -1 : p1->fd - p2->fd));
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}
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/* Special initialization for the rb-tree node to detect linkage */
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static inline void ep_rb_initnode(struct rb_node *n)
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{
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rb_set_parent(n, n);
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}
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/* Removes a node from the rb-tree and marks it for a fast is-linked check */
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static inline void ep_rb_erase(struct rb_node *n, struct rb_root *r)
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{
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rb_erase(n, r);
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rb_set_parent(n, n);
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}
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/* Fast check to verify that the item is linked to the main rb-tree */
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static inline int ep_rb_linked(struct rb_node *n)
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{
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return rb_parent(n) != n;
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}
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/*
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* Remove the item from the list and perform its initialization.
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* This is useful for us because we can test if the item is linked
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* using "ep_is_linked(p)".
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*/
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static inline void ep_list_del(struct list_head *p)
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{
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list_del(p);
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INIT_LIST_HEAD(p);
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}
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/* Tells us if the item is currently linked */
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static inline int ep_is_linked(struct list_head *p)
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{
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return !list_empty(p);
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}
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/* Get the "struct epitem" from a wait queue pointer */
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static inline struct epitem * ep_item_from_wait(wait_queue_t *p)
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{
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return container_of(p, struct eppoll_entry, wait)->base;
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}
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/* Get the "struct epitem" from an epoll queue wrapper */
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static inline struct epitem * ep_item_from_epqueue(poll_table *p)
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{
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return container_of(p, struct ep_pqueue, pt)->epi;
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}
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/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
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static inline int ep_op_hash_event(int op)
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{
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return op != EPOLL_CTL_DEL;
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}
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/* Initialize the poll safe wake up structure */
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static void ep_poll_safewake_init(struct poll_safewake *psw)
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{
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INIT_LIST_HEAD(&psw->wake_task_list);
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spin_lock_init(&psw->lock);
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}
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/*
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* Perform a safe wake up of the poll wait list. The problem is that
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* with the new callback'd wake up system, it is possible that the
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* poll callback is reentered from inside the call to wake_up() done
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* on the poll wait queue head. The rule is that we cannot reenter the
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* wake up code from the same task more than EP_MAX_POLLWAKE_NESTS times,
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* and we cannot reenter the same wait queue head at all. This will
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* enable to have a hierarchy of epoll file descriptor of no more than
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* EP_MAX_POLLWAKE_NESTS deep. We need the irq version of the spin lock
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* because this one gets called by the poll callback, that in turn is called
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* from inside a wake_up(), that might be called from irq context.
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*/
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static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq)
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{
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int wake_nests = 0;
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unsigned long flags;
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struct task_struct *this_task = current;
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struct list_head *lsthead = &psw->wake_task_list, *lnk;
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struct wake_task_node *tncur;
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struct wake_task_node tnode;
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spin_lock_irqsave(&psw->lock, flags);
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/* Try to see if the current task is already inside this wakeup call */
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list_for_each(lnk, lsthead) {
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tncur = list_entry(lnk, struct wake_task_node, llink);
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if (tncur->wq == wq ||
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(tncur->task == this_task && ++wake_nests > EP_MAX_POLLWAKE_NESTS)) {
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/*
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* Ops ... loop detected or maximum nest level reached.
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* We abort this wake by breaking the cycle itself.
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*/
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spin_unlock_irqrestore(&psw->lock, flags);
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return;
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}
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}
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/* Add the current task to the list */
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tnode.task = this_task;
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tnode.wq = wq;
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list_add(&tnode.llink, lsthead);
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spin_unlock_irqrestore(&psw->lock, flags);
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/* Do really wake up now */
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wake_up(wq);
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/* Remove the current task from the list */
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spin_lock_irqsave(&psw->lock, flags);
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list_del(&tnode.llink);
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spin_unlock_irqrestore(&psw->lock, flags);
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}
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/*
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* This is called from eventpoll_release() to unlink files from the eventpoll
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* interface. We need to have this facility to cleanup correctly files that are
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* closed without being removed from the eventpoll interface.
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*/
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void eventpoll_release_file(struct file *file)
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{
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struct list_head *lsthead = &file->f_ep_links;
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struct eventpoll *ep;
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struct epitem *epi;
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/*
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* We don't want to get "file->f_ep_lock" because it is not
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* necessary. It is not necessary because we're in the "struct file"
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* cleanup path, and this means that noone is using this file anymore.
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* The only hit might come from ep_free() but by holding the semaphore
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* will correctly serialize the operation. We do need to acquire
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* "ep->sem" after "epmutex" because ep_remove() requires it when called
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* from anywhere but ep_free().
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*/
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mutex_lock(&epmutex);
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while (!list_empty(lsthead)) {
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epi = list_entry(lsthead->next, struct epitem, fllink);
|
|
|
|
ep = epi->ep;
|
|
ep_list_del(&epi->fllink);
|
|
down_write(&ep->sem);
|
|
ep_remove(ep, epi);
|
|
up_write(&ep->sem);
|
|
}
|
|
|
|
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).
|
|
*/
|
|
asmlinkage long sys_epoll_create(int size)
|
|
{
|
|
int error, fd;
|
|
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;
|
|
|
|
/*
|
|
* Creates all the items needed to setup an eventpoll file. That is,
|
|
* a file structure, and inode and a free file descriptor.
|
|
*/
|
|
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_hash_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;
|
|
|
|
/*
|
|
* 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 eexit_3;
|
|
|
|
/*
|
|
* 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);
|
|
|
|
/* Try to lookup the file inside our hash table */
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* The function ep_find() increments the usage count of the structure
|
|
* so, if this is not NULL, we need to release it.
|
|
*/
|
|
if (epi)
|
|
ep_release_epitem(epi);
|
|
|
|
up_write(&ep->sem);
|
|
|
|
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));
|
|
|
|
return error;
|
|
}
|
|
|
|
#define MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
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 > 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;
|
|
}
|
|
|
|
|
|
/*
|
|
* Creates the file descriptor to be used by the epoll interface.
|
|
*/
|
|
static int ep_getfd(int *efd, struct inode **einode, struct file **efile,
|
|
struct eventpoll *ep)
|
|
{
|
|
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();
|
|
error = PTR_ERR(inode);
|
|
if (IS_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;
|
|
|
|
/*
|
|
* Link the inode to a directory entry by creating a unique name
|
|
* using the inode number.
|
|
*/
|
|
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_vfsmnt = mntget(eventpoll_mnt);
|
|
file->f_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;
|
|
|
|
eexit_4:
|
|
put_unused_fd(fd);
|
|
eexit_3:
|
|
iput(inode);
|
|
eexit_2:
|
|
put_filp(file);
|
|
eexit_1:
|
|
return error;
|
|
}
|
|
|
|
|
|
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;
|
|
}
|
|
|
|
|
|
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(&psw, &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->sem" 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 sufficent here.
|
|
*/
|
|
mutex_lock(&epmutex);
|
|
|
|
/*
|
|
* Walks through the whole tree by unregistering poll callbacks.
|
|
*/
|
|
for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
|
|
|
ep_unregister_pollwait(ep, epi);
|
|
}
|
|
|
|
/*
|
|
* Walks through the whole hash by freeing each "struct epitem". At this
|
|
* point we are sure no poll callbacks will be lingering around, and also by
|
|
* write-holding "sem" we can be sure that no file cleanup code will hit
|
|
* us during this operation. So we can avoid the lock on "ep->lock".
|
|
*/
|
|
while ((rbp = rb_first(&ep->rbr)) != 0) {
|
|
epi = rb_entry(rbp, struct epitem, rbn);
|
|
ep_remove(ep, epi);
|
|
}
|
|
|
|
mutex_unlock(&epmutex);
|
|
}
|
|
|
|
|
|
/*
|
|
* Search the file inside the eventpoll hash. It add usage count to
|
|
* the returned item, so the caller must call ep_release_epitem()
|
|
* after finished using the "struct epitem".
|
|
*/
|
|
static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
|
|
{
|
|
int kcmp;
|
|
unsigned long flags;
|
|
struct rb_node *rbp;
|
|
struct epitem *epi, *epir = NULL;
|
|
struct epoll_filefd ffd;
|
|
|
|
ep_set_ffd(&ffd, file, fd);
|
|
read_lock_irqsave(&ep->lock, flags);
|
|
for (rbp = ep->rbr.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 {
|
|
ep_use_epitem(epi);
|
|
epir = epi;
|
|
break;
|
|
}
|
|
}
|
|
read_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n",
|
|
current, file, epir));
|
|
|
|
return epir;
|
|
}
|
|
|
|
|
|
/*
|
|
* Increment the usage count of the "struct epitem" making it sure
|
|
* that the user will have a valid pointer to reference.
|
|
*/
|
|
static void ep_use_epitem(struct epitem *epi)
|
|
{
|
|
|
|
atomic_inc(&epi->usecnt);
|
|
}
|
|
|
|
|
|
/*
|
|
* 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 (atomic_dec_and_test(&epi->usecnt))
|
|
kmem_cache_free(epi_cache, epi);
|
|
}
|
|
|
|
|
|
/*
|
|
* 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, SLAB_KERNEL))) {
|
|
init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
|
|
pwq->whead = whead;
|
|
pwq->base = epi;
|
|
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_node, *parent = NULL;
|
|
struct epitem *epic;
|
|
|
|
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;
|
|
else
|
|
p = &parent->rb_left;
|
|
}
|
|
rb_link_node(&epi->rbn, parent, p);
|
|
rb_insert_color(&epi->rbn, &ep->rbr);
|
|
}
|
|
|
|
|
|
static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
|
|
struct file *tfile, int fd)
|
|
{
|
|
int error, revents, pwake = 0;
|
|
unsigned long flags;
|
|
struct epitem *epi;
|
|
struct ep_pqueue epq;
|
|
|
|
error = -ENOMEM;
|
|
if (!(epi = kmem_cache_alloc(epi_cache, SLAB_KERNEL)))
|
|
goto eexit_1;
|
|
|
|
/* Item initialization follow here ... */
|
|
ep_rb_initnode(&epi->rbn);
|
|
INIT_LIST_HEAD(&epi->rdllink);
|
|
INIT_LIST_HEAD(&epi->fllink);
|
|
INIT_LIST_HEAD(&epi->txlink);
|
|
INIT_LIST_HEAD(&epi->pwqlist);
|
|
epi->ep = ep;
|
|
ep_set_ffd(&epi->ffd, tfile, fd);
|
|
epi->event = *event;
|
|
atomic_set(&epi->usecnt, 1);
|
|
epi->nwait = 0;
|
|
|
|
/* 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.
|
|
*/
|
|
revents = tfile->f_op->poll(tfile, &epq.pt);
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (epi->nwait < 0)
|
|
goto eexit_2;
|
|
|
|
/* Add the current item to the list of active epoll hook for this file */
|
|
spin_lock(&tfile->f_ep_lock);
|
|
list_add_tail(&epi->fllink, &tfile->f_ep_links);
|
|
spin_unlock(&tfile->f_ep_lock);
|
|
|
|
/* We have to drop the new item inside our item list to keep track of it */
|
|
write_lock_irqsave(&ep->lock, flags);
|
|
|
|
/* Add the current item to the rb-tree */
|
|
ep_rbtree_insert(ep, epi);
|
|
|
|
/* If the file is already "ready" we drop it inside the ready list */
|
|
if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
|
|
/* Notify waiting tasks that events are available */
|
|
if (waitqueue_active(&ep->wq))
|
|
__wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE);
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
pwake++;
|
|
}
|
|
|
|
write_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
/* We have to call this outside the lock */
|
|
if (pwake)
|
|
ep_poll_safewake(&psw, &ep->poll_wait);
|
|
|
|
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_insert(%p, %p, %d)\n",
|
|
current, ep, tfile, fd));
|
|
|
|
return 0;
|
|
|
|
eexit_2:
|
|
ep_unregister_pollwait(ep, epi);
|
|
|
|
/*
|
|
* We need to do this because an event could have been arrived on some
|
|
* allocated wait queue.
|
|
*/
|
|
write_lock_irqsave(&ep->lock, flags);
|
|
if (ep_is_linked(&epi->rdllink))
|
|
ep_list_del(&epi->rdllink);
|
|
write_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
kmem_cache_free(epi_cache, epi);
|
|
eexit_1:
|
|
return error;
|
|
}
|
|
|
|
|
|
/*
|
|
* Modify the interest event mask by dropping an event if the new mask
|
|
* has a match in the current file status.
|
|
*/
|
|
static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event)
|
|
{
|
|
int pwake = 0;
|
|
unsigned int revents;
|
|
unsigned long flags;
|
|
|
|
/*
|
|
* Set the new event interest mask before calling f_op->poll(), otherwise
|
|
* a potential race might occur. In fact if we do this operation inside
|
|
* the lock, an event might happen between the f_op->poll() call and the
|
|
* new event set registering.
|
|
*/
|
|
epi->event.events = event->events;
|
|
|
|
/*
|
|
* Get current event bits. We can safely use the file* here because
|
|
* its usage count has been increased by the caller of this function.
|
|
*/
|
|
revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
|
|
|
|
write_lock_irqsave(&ep->lock, flags);
|
|
|
|
/* Copy the data member from inside the lock */
|
|
epi->event.data = event->data;
|
|
|
|
/*
|
|
* If the item is not linked to the hash it means that it's on its
|
|
* way toward the removal. Do nothing in this case.
|
|
*/
|
|
if (ep_rb_linked(&epi->rbn)) {
|
|
/*
|
|
* If the item is "hot" and it is not registered inside the ready
|
|
* list, push it inside. If the item is not "hot" and it is currently
|
|
* registered inside the ready list, unlink it.
|
|
*/
|
|
if (revents & event->events) {
|
|
if (!ep_is_linked(&epi->rdllink)) {
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
|
|
/* Notify waiting tasks that events are available */
|
|
if (waitqueue_active(&ep->wq))
|
|
__wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
|
|
TASK_INTERRUPTIBLE);
|
|
if (waitqueue_active(&ep->poll_wait))
|
|
pwake++;
|
|
}
|
|
}
|
|
}
|
|
|
|
write_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
/* We have to call this outside the lock */
|
|
if (pwake)
|
|
ep_poll_safewake(&psw, &ep->poll_wait);
|
|
|
|
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_entry(lsthead->next, struct eppoll_entry, llink);
|
|
|
|
ep_list_del(&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))
|
|
ep_list_del(&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 hash 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))
|
|
ep_list_del(&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 hash */
|
|
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;
|
|
}
|
|
|
|
|
|
/*
|
|
* Since we have to release the lock during the __copy_to_user() operation and
|
|
* during the f_op->poll() call, we try to collect the maximum number of items
|
|
* by reducing the irqlock/irqunlock switching rate.
|
|
*/
|
|
static int ep_collect_ready_items(struct eventpoll *ep, struct list_head *txlist, int maxevents)
|
|
{
|
|
int nepi;
|
|
unsigned long flags;
|
|
struct list_head *lsthead = &ep->rdllist, *lnk;
|
|
struct epitem *epi;
|
|
|
|
write_lock_irqsave(&ep->lock, flags);
|
|
|
|
for (nepi = 0, lnk = lsthead->next; lnk != lsthead && nepi < maxevents;) {
|
|
epi = list_entry(lnk, struct epitem, rdllink);
|
|
|
|
lnk = lnk->next;
|
|
|
|
/* If this file is already in the ready list we exit soon */
|
|
if (!ep_is_linked(&epi->txlink)) {
|
|
/*
|
|
* This is initialized in this way so that the default
|
|
* behaviour of the reinjecting code will be to push back
|
|
* the item inside the ready list.
|
|
*/
|
|
epi->revents = epi->event.events;
|
|
|
|
/* Link the ready item into the transfer list */
|
|
list_add(&epi->txlink, txlist);
|
|
nepi++;
|
|
|
|
/*
|
|
* Unlink the item from the ready list.
|
|
*/
|
|
ep_list_del(&epi->rdllink);
|
|
}
|
|
}
|
|
|
|
write_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
return nepi;
|
|
}
|
|
|
|
|
|
/*
|
|
* 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
|
|
* because of the way poll() is traditionally implemented in Linux.
|
|
*/
|
|
static int ep_send_events(struct eventpoll *ep, struct list_head *txlist,
|
|
struct epoll_event __user *events)
|
|
{
|
|
int eventcnt = 0;
|
|
unsigned int revents;
|
|
struct list_head *lnk;
|
|
struct epitem *epi;
|
|
|
|
/*
|
|
* We can loop without lock because this is a task private list.
|
|
* The test done during the collection loop will guarantee us that
|
|
* another task will not try to collect this file. Also, items
|
|
* cannot vanish during the loop because we are holding "sem".
|
|
*/
|
|
list_for_each(lnk, txlist) {
|
|
epi = list_entry(lnk, struct epitem, txlink);
|
|
|
|
/*
|
|
* Get the ready file event set. We can safely use the file
|
|
* because we are holding the "sem" in read and this will
|
|
* guarantee that both the file and the item will not vanish.
|
|
*/
|
|
revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
|
|
|
|
/*
|
|
* Set the return event set for the current file descriptor.
|
|
* Note that only the task task was successfully able to link
|
|
* the item to its "txlist" will write this field.
|
|
*/
|
|
epi->revents = revents & epi->event.events;
|
|
|
|
if (epi->revents) {
|
|
if (__put_user(epi->revents,
|
|
&events[eventcnt].events) ||
|
|
__put_user(epi->event.data,
|
|
&events[eventcnt].data))
|
|
return -EFAULT;
|
|
if (epi->event.events & EPOLLONESHOT)
|
|
epi->event.events &= EP_PRIVATE_BITS;
|
|
eventcnt++;
|
|
}
|
|
}
|
|
return eventcnt;
|
|
}
|
|
|
|
|
|
/*
|
|
* Walk through the transfer list we collected with ep_collect_ready_items()
|
|
* and, if 1) the item is still "alive" 2) its event set is not empty 3) it's
|
|
* not already linked, links it to the ready list. Same as above, we are holding
|
|
* "sem" so items cannot vanish underneath our nose.
|
|
*/
|
|
static void ep_reinject_items(struct eventpoll *ep, struct list_head *txlist)
|
|
{
|
|
int ricnt = 0, pwake = 0;
|
|
unsigned long flags;
|
|
struct epitem *epi;
|
|
|
|
write_lock_irqsave(&ep->lock, flags);
|
|
|
|
while (!list_empty(txlist)) {
|
|
epi = list_entry(txlist->next, struct epitem, txlink);
|
|
|
|
/* Unlink the current item from the transfer list */
|
|
ep_list_del(&epi->txlink);
|
|
|
|
/*
|
|
* If the item is no more linked to the interest set, we don't
|
|
* have to push it inside the ready list because the following
|
|
* ep_release_epitem() is going to drop it. Also, if the current
|
|
* item is set to have an Edge Triggered behaviour, we don't have
|
|
* to push it back either.
|
|
*/
|
|
if (ep_rb_linked(&epi->rbn) && !(epi->event.events & EPOLLET) &&
|
|
(epi->revents & epi->event.events) && !ep_is_linked(&epi->rdllink)) {
|
|
list_add_tail(&epi->rdllink, &ep->rdllist);
|
|
ricnt++;
|
|
}
|
|
}
|
|
|
|
if (ricnt) {
|
|
/*
|
|
* 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++;
|
|
}
|
|
|
|
write_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
/* We have to call this outside the lock */
|
|
if (pwake)
|
|
ep_poll_safewake(&psw, &ep->poll_wait);
|
|
}
|
|
|
|
|
|
/*
|
|
* Perform the transfer of events to user space.
|
|
*/
|
|
static int ep_events_transfer(struct eventpoll *ep,
|
|
struct epoll_event __user *events, int maxevents)
|
|
{
|
|
int eventcnt = 0;
|
|
struct list_head txlist;
|
|
|
|
INIT_LIST_HEAD(&txlist);
|
|
|
|
/*
|
|
* We need to lock this because we could be hit by
|
|
* eventpoll_release_file() and epoll_ctl(EPOLL_CTL_DEL).
|
|
*/
|
|
down_read(&ep->sem);
|
|
|
|
/* Collect/extract ready items */
|
|
if (ep_collect_ready_items(ep, &txlist, maxevents) > 0) {
|
|
/* Build result set in userspace */
|
|
eventcnt = ep_send_events(ep, &txlist, events);
|
|
|
|
/* Reinject ready items into the ready list */
|
|
ep_reinject_items(ep, &txlist);
|
|
}
|
|
|
|
up_read(&ep->sem);
|
|
|
|
return eventcnt;
|
|
}
|
|
|
|
|
|
static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
|
|
int maxevents, long timeout)
|
|
{
|
|
int res, eavail;
|
|
unsigned long flags;
|
|
long jtimeout;
|
|
wait_queue_t wait;
|
|
|
|
/*
|
|
* Calculate the timeout by checking for the "infinite" value ( -1 )
|
|
* and the overflow condition. The passed timeout is in milliseconds,
|
|
* that why (t * HZ) / 1000.
|
|
*/
|
|
jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ?
|
|
MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000;
|
|
|
|
retry:
|
|
write_lock_irqsave(&ep->lock, flags);
|
|
|
|
res = 0;
|
|
if (list_empty(&ep->rdllist)) {
|
|
/*
|
|
* 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(&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);
|
|
if (!list_empty(&ep->rdllist) || !jtimeout)
|
|
break;
|
|
if (signal_pending(current)) {
|
|
res = -EINTR;
|
|
break;
|
|
}
|
|
|
|
write_unlock_irqrestore(&ep->lock, flags);
|
|
jtimeout = schedule_timeout(jtimeout);
|
|
write_lock_irqsave(&ep->lock, flags);
|
|
}
|
|
__remove_wait_queue(&ep->wq, &wait);
|
|
|
|
set_current_state(TASK_RUNNING);
|
|
}
|
|
|
|
/* Is it worth to try to dig for events ? */
|
|
eavail = !list_empty(&ep->rdllist);
|
|
|
|
write_unlock_irqrestore(&ep->lock, flags);
|
|
|
|
/*
|
|
* 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_events_transfer(ep, events, maxevents)) && jtimeout)
|
|
goto retry;
|
|
|
|
return res;
|
|
}
|
|
|
|
|
|
static int eventpollfs_delete_dentry(struct dentry *dentry)
|
|
{
|
|
|
|
return 1;
|
|
}
|
|
|
|
|
|
static struct inode *ep_eventpoll_inode(void)
|
|
{
|
|
int error = -ENOMEM;
|
|
struct inode *inode = new_inode(eventpoll_mnt->mnt_sb);
|
|
|
|
if (!inode)
|
|
goto eexit_1;
|
|
|
|
inode->i_fop = &eventpoll_fops;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
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);
|
|
}
|
|
|
|
|
|
static int
|
|
eventpollfs_get_sb(struct file_system_type *fs_type, int flags,
|
|
const char *dev_name, void *data, struct vfsmount *mnt)
|
|
{
|
|
return get_sb_pseudo(fs_type, "eventpoll:", NULL, EVENTPOLLFS_MAGIC,
|
|
mnt);
|
|
}
|
|
|
|
|
|
static int __init eventpoll_init(void)
|
|
{
|
|
int error;
|
|
|
|
mutex_init(&epmutex);
|
|
|
|
/* Initialize the structure used to perform safe poll wait head wake ups */
|
|
ep_poll_safewake_init(&psw);
|
|
|
|
/* Allocates slab cache used to allocate "struct epitem" items */
|
|
epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
|
|
0, SLAB_HWCACHE_ALIGN|EPI_SLAB_DEBUG|SLAB_PANIC,
|
|
NULL, NULL);
|
|
|
|
/* Allocates slab cache used to allocate "struct eppoll_entry" */
|
|
pwq_cache = kmem_cache_create("eventpoll_pwq",
|
|
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");
|
|
}
|
|
|
|
|
|
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");
|