X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=fs%2Feventfd.c;h=8b47e4200e65e00a64be1bb60a80091b6940ddb2;hb=0031462b5b392f90d17f1d75abb795883c44e969;hp=2a701d593d35f36d2511c25df916a5d61098b019;hpb=395108880efff4a4ffa1ffa554477f7f5ba6a031;p=safe%2Fjmp%2Flinux-2.6 diff --git a/fs/eventfd.c b/fs/eventfd.c index 2a701d5..8b47e42 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -14,34 +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) @@ -56,10 +66,52 @@ int eventfd_signal(struct file *file, int n) 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; } @@ -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; @@ -197,10 +259,67 @@ struct file *eventfd_fget(int fd) return file; } +EXPORT_SYMBOL_GPL(eventfd_fget); -SYSCALL_DEFINE2(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) +{ + struct file *file; + struct eventfd_ctx *ctx; + + 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) { - int fd; + 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. */ @@ -208,25 +327,48 @@ SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags) BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK); if (flags & ~EFD_FLAGS_SET) - return -EINVAL; + 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; - /* - * 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 & EFD_SHARED_FCNTL_FLAGS); - if (fd < 0) - kfree(ctx); + 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); + return fd; + +err_put_unused_fd: + put_unused_fd(fd); + + return error; } SYSCALL_DEFINE1(eventfd, unsigned int, count)