X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=fs%2Feventfd.c;h=8b47e4200e65e00a64be1bb60a80091b6940ddb2;hb=80f506918fdaaca6b574ba931536a58ce015c7be;hp=3ed4466177a74929b2fac1cde0b38af8ef0e9f06;hpb=e7d476dfdf0bcfed478a207aecfdc84f81efecaf;p=safe%2Fjmp%2Flinux-2.6 diff --git a/fs/eventfd.c b/fs/eventfd.c index 3ed4466..8b47e42 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -14,33 +14,44 @@ #include #include #include -#include #include +#include +#include +#include struct eventfd_ctx { + struct kref kref; wait_queue_head_t wqh; /* * Every time that a write(2) is performed on an eventfd, the * value of the __u64 being written is added to "count" and a * wakeup is performed on "wqh". A read(2) will return the "count" * value to userspace, and will reset "count" to zero. The kernel - * size eventfd_signal() also, adds to the "count" counter and + * side eventfd_signal() also, adds to the "count" counter and * issue a wakeup. */ __u64 count; + unsigned int flags; }; -/* - * Adds "n" to the eventfd counter "count". Returns "n" in case of - * success, or a value lower then "n" in case of coutner overflow. - * This function is supposed to be called by the kernel in paths - * that do not allow sleeping. In this function we allow the counter - * to reach the ULLONG_MAX value, and we signal this as overflow - * condition by returining a POLLERR to poll(2). +/** + * eventfd_signal - Adds @n to the eventfd counter. + * @ctx: [in] Pointer to the eventfd context. + * @n: [in] Value of the counter to be added to the eventfd internal counter. + * The value cannot be negative. + * + * This function is supposed to be called by the kernel in paths that do not + * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX + * value, and we signal this as overflow condition by returining a POLLERR + * to poll(2). + * + * Returns @n in case of success, a non-negative number lower than @n in case + * of overflow, or the following error codes: + * + * -EINVAL : The value of @n is negative. */ -int eventfd_signal(struct file *file, int n) +int eventfd_signal(struct eventfd_ctx *ctx, int n) { - struct eventfd_ctx *ctx = file->private_data; unsigned long flags; if (n < 0) @@ -50,15 +61,57 @@ int eventfd_signal(struct file *file, int n) n = (int) (ULLONG_MAX - ctx->count); ctx->count += n; if (waitqueue_active(&ctx->wqh)) - wake_up_locked(&ctx->wqh); + wake_up_locked_poll(&ctx->wqh, POLLIN); spin_unlock_irqrestore(&ctx->wqh.lock, flags); return n; } +EXPORT_SYMBOL_GPL(eventfd_signal); + +static void eventfd_free_ctx(struct eventfd_ctx *ctx) +{ + kfree(ctx); +} + +static void eventfd_free(struct kref *kref) +{ + struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref); + + eventfd_free_ctx(ctx); +} + +/** + * eventfd_ctx_get - Acquires a reference to the internal eventfd context. + * @ctx: [in] Pointer to the eventfd context. + * + * Returns: In case of success, returns a pointer to the eventfd context. + */ +struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx) +{ + kref_get(&ctx->kref); + return ctx; +} +EXPORT_SYMBOL_GPL(eventfd_ctx_get); + +/** + * eventfd_ctx_put - Releases a reference to the internal eventfd context. + * @ctx: [in] Pointer to eventfd context. + * + * The eventfd context reference must have been previously acquired either + * with eventfd_ctx_get() or eventfd_ctx_fdget()). + */ +void eventfd_ctx_put(struct eventfd_ctx *ctx) +{ + kref_put(&ctx->kref, eventfd_free); +} +EXPORT_SYMBOL_GPL(eventfd_ctx_put); static int eventfd_release(struct inode *inode, struct file *file) { - kfree(file->private_data); + struct eventfd_ctx *ctx = file->private_data; + + wake_up_poll(&ctx->wqh, POLLHUP); + eventfd_ctx_put(ctx); return 0; } @@ -87,22 +140,20 @@ static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count, { struct eventfd_ctx *ctx = file->private_data; ssize_t res; - __u64 ucnt; + __u64 ucnt = 0; DECLARE_WAITQUEUE(wait, current); if (count < sizeof(ucnt)) return -EINVAL; spin_lock_irq(&ctx->wqh.lock); res = -EAGAIN; - ucnt = ctx->count; - if (ucnt > 0) + if (ctx->count > 0) res = sizeof(ucnt); else if (!(file->f_flags & O_NONBLOCK)) { __add_wait_queue(&ctx->wqh, &wait); for (res = 0;;) { set_current_state(TASK_INTERRUPTIBLE); if (ctx->count > 0) { - ucnt = ctx->count; res = sizeof(ucnt); break; } @@ -117,10 +168,11 @@ static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count, __remove_wait_queue(&ctx->wqh, &wait); __set_current_state(TASK_RUNNING); } - if (res > 0) { - ctx->count = 0; + if (likely(res > 0)) { + ucnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count; + ctx->count -= ucnt; if (waitqueue_active(&ctx->wqh)) - wake_up_locked(&ctx->wqh); + wake_up_locked_poll(&ctx->wqh, POLLOUT); } spin_unlock_irq(&ctx->wqh.lock); if (res > 0 && put_user(ucnt, (__u64 __user *) buf)) @@ -166,10 +218,10 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c __remove_wait_queue(&ctx->wqh, &wait); __set_current_state(TASK_RUNNING); } - if (res > 0) { + if (likely(res > 0)) { ctx->count += ucnt; if (waitqueue_active(&ctx->wqh)) - wake_up_locked(&ctx->wqh); + wake_up_locked_poll(&ctx->wqh, POLLIN); } spin_unlock_irq(&ctx->wqh.lock); @@ -183,6 +235,16 @@ static const struct file_operations eventfd_fops = { .write = eventfd_write, }; +/** + * eventfd_fget - Acquire a reference of an eventfd file descriptor. + * @fd: [in] Eventfd file descriptor. + * + * Returns a pointer to the eventfd file structure in case of success, or the + * following error pointer: + * + * -EBADF : Invalid @fd file descriptor. + * -EINVAL : The @fd file descriptor is not an eventfd file. + */ struct file *eventfd_fget(int fd) { struct file *file; @@ -197,34 +259,119 @@ struct file *eventfd_fget(int fd) return file; } +EXPORT_SYMBOL_GPL(eventfd_fget); -asmlinkage long sys_eventfd2(unsigned int count, int flags) +/** + * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context. + * @fd: [in] Eventfd file descriptor. + * + * Returns a pointer to the internal eventfd context, otherwise the error + * pointers returned by the following functions: + * + * eventfd_fget + */ +struct eventfd_ctx *eventfd_ctx_fdget(int fd) { - int fd; + struct file *file; struct eventfd_ctx *ctx; - if (flags & ~(EFD_CLOEXEC | EFD_NONBLOCK)) - return -EINVAL; + file = eventfd_fget(fd); + if (IS_ERR(file)) + return (struct eventfd_ctx *) file; + ctx = eventfd_ctx_get(file->private_data); + fput(file); + + return ctx; +} +EXPORT_SYMBOL_GPL(eventfd_ctx_fdget); + +/** + * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context. + * @file: [in] Eventfd file pointer. + * + * Returns a pointer to the internal eventfd context, otherwise the error + * pointer: + * + * -EINVAL : The @fd file descriptor is not an eventfd file. + */ +struct eventfd_ctx *eventfd_ctx_fileget(struct file *file) +{ + if (file->f_op != &eventfd_fops) + return ERR_PTR(-EINVAL); + + return eventfd_ctx_get(file->private_data); +} +EXPORT_SYMBOL_GPL(eventfd_ctx_fileget); + +/** + * eventfd_file_create - Creates an eventfd file pointer. + * @count: Initial eventfd counter value. + * @flags: Flags for the eventfd file. + * + * This function creates an eventfd file pointer, w/out installing it into + * the fd table. This is useful when the eventfd file is used during the + * initialization of data structures that require extra setup after the eventfd + * creation. So the eventfd creation is split into the file pointer creation + * phase, and the file descriptor installation phase. + * In this way races with userspace closing the newly installed file descriptor + * can be avoided. + * Returns an eventfd file pointer, or a proper error pointer. + */ +struct file *eventfd_file_create(unsigned int count, int flags) +{ + struct file *file; + struct eventfd_ctx *ctx; + + /* Check the EFD_* constants for consistency. */ + BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC); + BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK); + + if (flags & ~EFD_FLAGS_SET) + return ERR_PTR(-EINVAL); ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); if (!ctx) - return -ENOMEM; + return ERR_PTR(-ENOMEM); + kref_init(&ctx->kref); init_waitqueue_head(&ctx->wqh); ctx->count = count; + ctx->flags = flags; + + file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx, + flags & EFD_SHARED_FCNTL_FLAGS); + if (IS_ERR(file)) + eventfd_free_ctx(ctx); + + return file; +} + +SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags) +{ + int fd, error; + struct file *file; + + error = get_unused_fd_flags(flags & EFD_SHARED_FCNTL_FLAGS); + if (error < 0) + return error; + fd = error; + + file = eventfd_file_create(count, flags); + if (IS_ERR(file)) { + error = PTR_ERR(file); + goto err_put_unused_fd; + } + fd_install(fd, file); - /* - * When we call this, the initialization must be complete, since - * anon_inode_getfd() will install the fd. - */ - fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx, - flags & (O_CLOEXEC | O_NONBLOCK)); - if (fd < 0) - kfree(ctx); return fd; + +err_put_unused_fd: + put_unused_fd(fd); + + return error; } -asmlinkage long sys_eventfd(unsigned int count) +SYSCALL_DEFINE1(eventfd, unsigned int, count) { return sys_eventfd2(count, 0); }