Matt Mackall suggested converting epoll's ep_lock to a bitlock as a way of saving space in struct file. This patch makes that change.
Signed-off-by: Jonathan Corbet <[email protected]> --- fs/eventpoll.c | 13 ++++++++----- fs/fcntl.c | 2 +- include/asm-generic/fcntl.h | 4 ++++ include/linux/eventpoll.h | 2 +- include/linux/fs.h | 1 - 5 files changed, 14 insertions(+), 8 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index ba2f9ec..95fae01 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -25,6 +25,7 @@ #include <linux/list.h> #include <linux/hash.h> #include <linux/spinlock.h> +#include <linux/bit_spinlock.h> #include <linux/syscalls.h> #include <linux/rbtree.h> #include <linux/wait.h> @@ -427,10 +428,10 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi) ep_unregister_pollwait(ep, epi); /* Remove the current item from the list of epoll hooks */ - spin_lock(&file->f_ep_lock); + bit_spin_lock(NR_EPOLL_FILE_LOCK, &file->f_flags); if (ep_is_linked(&epi->fllink)) list_del_init(&epi->fllink); - spin_unlock(&file->f_ep_lock); + bit_spin_unlock(NR_EPOLL_FILE_LOCK, &file->f_flags); rb_erase(&epi->rbn, &ep->rbr); @@ -549,7 +550,7 @@ void eventpoll_release_file(struct file *file) struct epitem *epi; /* - * We don't want to get "file->f_ep_lock" because it is not + * We don't want to get EPOLL_FILE_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. * So, for example, epoll_ctl() cannot hit here sicne if we reach this @@ -558,6 +559,8 @@ void eventpoll_release_file(struct file *file) * will correctly serialize the operation. We do need to acquire * "ep->mtx" after "epmutex" because ep_remove() requires it when called * from anywhere but ep_free(). + * + * Besides, ep_remove() takes the lock. */ mutex_lock(&epmutex); @@ -800,9 +803,9 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, goto error_unregister; /* Add the current item to the list of active epoll hook for this file */ - spin_lock(&tfile->f_ep_lock); + bit_spin_lock(NR_EPOLL_FILE_LOCK, &tfile->f_flags); list_add_tail(&epi->fllink, &tfile->f_ep_links); - spin_unlock(&tfile->f_ep_lock); + bit_spin_unlock(NR_EPOLL_FILE_LOCK, &tfile->f_flags); /* * Add the current item to the RB tree. All RB tree operations are diff --git a/fs/fcntl.c b/fs/fcntl.c index 3affd3e..756119e 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -299,7 +299,7 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg, set_close_on_exec(fd, arg & FD_CLOEXEC); break; case F_GETFL: - err = filp->f_flags; + err = filp->f_flags & ~EPOLL_FILE_LOCK; break; case F_SETFL: err = setfl(fd, filp, arg); diff --git a/include/asm-generic/fcntl.h b/include/asm-generic/fcntl.h index 41e9f88..d56a513 100644 --- a/include/asm-generic/fcntl.h +++ b/include/asm-generic/fcntl.h @@ -62,6 +62,10 @@ #define NR_O_NDELAY NR_O_NONBLOCK #endif +/* Use bit 31 for epoll locking */ +#define NR_EPOLL_FILE_LOCK 31 +#define EPOLL_FILE_LOCK (1 << NR_EPOLL_FILE_LOCK) + #define F_DUPFD 0 /* dup */ #define F_GETFD 1 /* get close_on_exec */ #define F_SETFD 2 /* set/clear close_on_exec */ diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h index f1e1d3c..7b5c58a 100644 --- a/include/linux/eventpoll.h +++ b/include/linux/eventpoll.h @@ -61,7 +61,7 @@ struct file; static inline void eventpoll_init_file(struct file *file) { INIT_LIST_HEAD(&file->f_ep_links); - spin_lock_init(&file->f_ep_lock); + clear_bit(NR_EPOLL_FILE_LOCK, &file->f_flags); } diff --git a/include/linux/fs.h b/include/linux/fs.h index 9d7cb0e..ecd9a5b 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -865,7 +865,6 @@ struct file { #ifdef CONFIG_EPOLL /* Used by fs/eventpoll.c to link all the hooks to this file */ struct list_head f_ep_links; - spinlock_t f_ep_lock; #endif /* #ifdef CONFIG_EPOLL */ struct address_space *f_mapping; #ifdef CONFIG_DEBUG_WRITECOUNT -- 1.6.1.1 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
