The key feature of the pollfs file operations is to internally handle pollable (waitable) resources as files without exporting complex and bug-prone underlying (VFS) implementation details. All resource handlers are required to implement the read, write, poll, release operations and must not block. Signed-off-by: Davi E. M. Arnaut --- Index: linux-2.6/fs/pollfs/file.c =================================================================== --- /dev/null +++ linux-2.6/fs/pollfs/file.c @@ -0,0 +1,238 @@ +/* + * Copyright (C) 2007 Davi E. M. Arnaut + * + * Licensed under the GNU GPL. See the file COPYING for details. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define POLLFS_MAGIC 0x9a6afcd + +MODULE_LICENSE("GPL"); + +/* pollfs vfsmount entry */ +static struct vfsmount *pfs_mnt; + +/* pollfs file operations */ +static const struct file_operations pfs_fops; + +static inline ssize_t +pfs_read_nonblock(const struct pfs_operations *fops, void *data, + void __user *obj, size_t nr) +{ + ssize_t count = 0, res = 0; + + do { + res = fops->read(data, obj); + if (res) + break; + count++; + obj += fops->rsize; + } while (--nr); + + if (count) + return count * fops->rsize; + else if (res) + return res; + else + return -EAGAIN; +} + +static inline ssize_t +pfs_read_block(const struct pfs_operations *fops, void *data, + wait_queue_head_t *wait, void __user *obj, size_t nr) +{ + ssize_t count; + + do { + count = pfs_read_nonblock(fops, data, obj, nr); + if (count != -EAGAIN) + break; + count = wait_event_interruptible((*wait), fops->poll(data)); + } while (!count); + + return count; +} + +static ssize_t pfs_read(struct file *filp, char __user * buf, + size_t count, loff_t * pos) +{ + size_t nevents = count; + struct pfs_file *pfs = filp->private_data; + const struct pfs_operations *fops = pfs->fops; + + if (fops->rsize) + nevents /= fops->rsize; + else + nevents = 1; + + if (!nevents) + return -EINVAL; + + if (filp->f_flags & O_NONBLOCK) + return pfs_read_nonblock(fops, pfs->data, buf, nevents); + else + return pfs_read_block(fops, pfs->data, pfs->wait, buf, nevents); +} + +static ssize_t pfs_write(struct file *filp, const char __user * buf, + size_t count, loff_t * ppos) +{ + ssize_t res = 0; + size_t nevents = count; + struct pfs_file *pfs = filp->private_data; + const struct pfs_operations *fops = pfs->fops; + + if (fops->wsize) + nevents /= fops->wsize; + else + nevents = 1; + + if (!nevents) + return -EINVAL; + + count = 0; + + do { + res = fops->write(pfs->data, buf); + if (res) + break; + count++; + buf += fops->wsize; + } while (--nevents); + + if (count) + return count * fops->wsize; + else if (res) + return res; + else + return 0; +} + +static unsigned int pfs_poll(struct file *filp, struct poll_table_struct *wait) +{ + int ret = 0; + struct pfs_file *pfs = filp->private_data; + + poll_wait(filp, pfs->wait, wait); + + if (pfs->fops->poll) + ret = pfs->fops->poll(pfs->data); + else + ret = POLLIN; + + return ret; +} + +static int pfs_mmap(struct file *filp, struct vm_area_struct *vma) +{ + struct pfs_file *pfs = filp->private_data; + + return (pfs->fops->mmap) ? pfs->fops->mmap(pfs->data, vma) : -ENODEV; +} + +static int pfs_release(struct inode *inode, struct file *filp) +{ + struct pfs_file *pfs = filp->private_data; + + return pfs->fops->release(pfs->data); +} + +static const struct file_operations pfs_fops = { + .poll = pfs_poll, + .mmap = pfs_mmap, + .read = pfs_read, + .write = pfs_write, + .release = pfs_release +}; + +long pfs_open(struct pfs_file *pfs) +{ + int fd; + struct file *filp; + const struct pfs_operations *fops = pfs->fops; + + if (IS_ERR(pfs_mnt)) + return -ENOSYS; + + if (!fops->poll || (!fops->read || !fops->write)) + return -EINVAL; + + fd = get_unused_fd(); + if (fd < 0) + return -ENFILE; + + filp = get_empty_filp(); + if (!filp) { + put_unused_fd(fd); + return -ENFILE; + } + + filp->f_op = &pfs_fops; + filp->f_path.mnt = mntget(pfs_mnt); + filp->f_path.dentry = dget(pfs_mnt->mnt_root); + filp->f_mapping = filp->f_path.dentry->d_inode->i_mapping; + filp->f_mode = 0; + filp->f_flags = 0; + filp->private_data = pfs; + + if (fops->read) { + filp->f_flags = O_RDONLY; + filp->f_mode |= FMODE_READ; + } + + if (fops->write) { + filp->f_flags = O_WRONLY; + filp->f_mode |= FMODE_WRITE; + } + + if (fops->write && fops->read) + filp->f_flags = O_RDWR; + + fd_install(fd, filp); + + return fd; +} + +EXPORT_SYMBOL(pfs_open); + +static int pfs_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, "pollfs", NULL, POLLFS_MAGIC, mnt); +} + +static struct file_system_type pollfs_type = { + .name = "pollfs", + .get_sb = pfs_get_sb, + .kill_sb = kill_anon_super +}; + +static int __init pollfs_init(void) +{ + int ret; + + ret = register_filesystem(&pollfs_type); + if (ret) + return ret; + + pfs_mnt = kern_mount(&pollfs_type); + if (IS_ERR(pfs_mnt)) { + ret = PTR_ERR(pfs_mnt); + unregister_filesystem(&pollfs_type); + } + + return ret; +} + +__initcall(pollfs_init); Index: linux-2.6/init/Kconfig =================================================================== --- linux-2.6.orig/init/Kconfig +++ linux-2.6/init/Kconfig @@ -463,6 +463,12 @@ config EPOLL Disabling this option will cause the kernel to be built without support for epoll family of system calls. +config POLLFS + bool "Enable pollfs support" if EMBEDDED + default y + help + Pollfs support + config SHMEM bool "Use full shmem filesystem" if EMBEDDED default y Index: linux-2.6/fs/Makefile =================================================================== --- linux-2.6.orig/fs/Makefile +++ linux-2.6/fs/Makefile @@ -114,3 +114,4 @@ obj-$(CONFIG_HPPFS) += hppfs/ obj-$(CONFIG_DEBUG_FS) += debugfs/ obj-$(CONFIG_OCFS2_FS) += ocfs2/ obj-$(CONFIG_GFS2_FS) += gfs2/ +obj-$(CONFIG_POLLFS) += pollfs/ Index: linux-2.6/fs/pollfs/Makefile =================================================================== --- /dev/null +++ linux-2.6/fs/pollfs/Makefile @@ -0,0 +1,2 @@ +obj-$(CONFIG_POLLFS) += pollfs.o +pollfs-y := file.o -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/