diff options
| -rw-r--r-- | Documentation/filesystems/relayfs.txt | 362 | ||||
| -rw-r--r-- | fs/Kconfig | 12 | ||||
| -rw-r--r-- | fs/Makefile | 1 | ||||
| -rw-r--r-- | fs/relayfs/Makefile | 4 | ||||
| -rw-r--r-- | fs/relayfs/buffers.c | 189 | ||||
| -rw-r--r-- | fs/relayfs/buffers.h | 12 | ||||
| -rw-r--r-- | fs/relayfs/inode.c | 609 | ||||
| -rw-r--r-- | fs/relayfs/relay.c | 431 | ||||
| -rw-r--r-- | fs/relayfs/relay.h | 12 | ||||
| -rw-r--r-- | include/linux/relayfs_fs.h | 255 |
10 files changed, 1887 insertions, 0 deletions
diff --git a/Documentation/filesystems/relayfs.txt b/Documentation/filesystems/relayfs.txt new file mode 100644 index 00000000000..d24e1b0d4f3 --- /dev/null +++ b/Documentation/filesystems/relayfs.txt @@ -0,0 +1,362 @@ + +relayfs - a high-speed data relay filesystem +============================================ + +relayfs is a filesystem designed to provide an efficient mechanism for +tools and facilities to relay large and potentially sustained streams +of data from kernel space to user space. + +The main abstraction of relayfs is the 'channel'. A channel consists +of a set of per-cpu kernel buffers each represented by a file in the +relayfs filesystem. Kernel clients write into a channel using +efficient write functions which automatically log to the current cpu's +channel buffer. User space applications mmap() the per-cpu files and +retrieve the data as it becomes available. + +The format of the data logged into the channel buffers is completely +up to the relayfs client; relayfs does however provide hooks which +allow clients to impose some stucture on the buffer data. Nor does +relayfs implement any form of data filtering - this also is left to +the client. The purpose is to keep relayfs as simple as possible. + +This document provides an overview of the relayfs API. The details of +the function parameters are documented along with the functions in the +filesystem code - please see that for details. + +Semantics +========= + +Each relayfs channel has one buffer per CPU, each buffer has one or +more sub-buffers. Messages are written to the first sub-buffer until +it is too full to contain a new message, in which case it it is +written to the next (if available). Messages are never split across +sub-buffers. At this point, userspace can be notified so it empties +the first sub-buffer, while the kernel continues writing to the next. + +When notified that a sub-buffer is full, the kernel knows how many +bytes of it are padding i.e. unused. Userspace can use this knowledge +to copy only valid data. + +After copying it, userspace can notify the kernel that a sub-buffer +has been consumed. + +relayfs can operate in a mode where it will overwrite data not yet +collected by userspace, and not wait for it to consume it. + +relayfs itself does not provide for communication of such data between +userspace and kernel, allowing the kernel side to remain simple and not +impose a single interface on userspace. It does provide a separate +helper though, described below. + +klog, relay-app & librelay +========================== + +relayfs itself is ready to use, but to make things easier, two +additional systems are provided. klog is a simple wrapper to make +writing formatted text or raw data to a channel simpler, regardless of +whether a channel to write into exists or not, or whether relayfs is +compiled into the kernel or is configured as a module. relay-app is +the kernel counterpart of userspace librelay.c, combined these two +files provide glue to easily stream data to disk, without having to +bother with housekeeping. klog and relay-app can be used together, +with klog providing high-level logging functions to the kernel and +relay-app taking care of kernel-user control and disk-logging chores. + +It is possible to use relayfs without relay-app & librelay, but you'll +have to implement communication between userspace and kernel, allowing +both to convey the state of buffers (full, empty, amount of padding). + +klog, relay-app and librelay can be found in the relay-apps tarball on +http://relayfs.sourceforge.net + +The relayfs user space API +========================== + +relayfs implements basic file operations for user space access to +relayfs channel buffer data. Here are the file operations that are +available and some comments regarding their behavior: + +open() enables user to open an _existing_ buffer. + +mmap() results in channel buffer being mapped into the caller's + memory space. Note that you can't do a partial mmap - you must + map the entire file, which is NRBUF * SUBBUFSIZE. + +read() read the contents of a channel buffer. The bytes read are + 'consumed' by the reader i.e. they won't be available again + to subsequent reads. If the channel is being used in + no-overwrite mode (the default), it can be read at any time + even if there's an active kernel writer. If the channel is + being used in overwrite mode and there are active channel + writers, results may be unpredictable - users should make + sure that all logging to the channel has ended before using + read() with overwrite mode. + +poll() POLLIN/POLLRDNORM/POLLERR supported. User applications are + notified when sub-buffer boundaries are crossed. + +close() decrements the channel buffer's refcount. When the refcount + reaches 0 i.e. when no process or kernel client has the buffer + open, the channel buffer is freed. + + +In order for a user application to make use of relayfs files, the +relayfs filesystem must be mounted. For example, + + mount -t relayfs relayfs /mnt/relay + +NOTE: relayfs doesn't need to be mounted for kernel clients to create + or use channels - it only needs to be mounted when user space + applications need access to the buffer data. + + +The relayfs kernel API +====================== + +Here's a summary of the API relayfs provides to in-kernel clients: + + + channel management functions: + + relay_open(base_filename, parent, subbuf_size, n_subbufs, + callbacks) + relay_close(chan) + relay_flush(chan) + relay_reset(chan) + relayfs_create_dir(name, parent) + relayfs_remove_dir(dentry) + + channel management typically called on instigation of userspace: + + relay_subbufs_consumed(chan, cpu, subbufs_consumed) + + write functions: + + relay_write(chan, data, length) + __relay_write(chan, data, length) + relay_reserve(chan, length) + + callbacks: + + subbuf_start(buf, subbuf, prev_subbuf, prev_padding) + buf_mapped(buf, filp) + buf_unmapped(buf, filp) + + helper functions: + + relay_buf_full(buf) + subbuf_start_reserve(buf, length) + + +Creating a channel +------------------ + +relay_open() is used to create a channel, along with its per-cpu +channel buffers. Each channel buffer will have an associated file +created for it in the relayfs filesystem, which can be opened and +mmapped from user space if desired. The files are named +basename0...basenameN-1 where N is the number of online cpus, and by +default will be created in the root of the filesystem. If you want a +directory structure to contain your relayfs files, you can create it +with relayfs_create_dir() and pass the parent directory to +relay_open(). Clients are responsible for cleaning up any directory +structure they create when the channel is closed - use +relayfs_remove_dir() for that. + +The total size of each per-cpu buffer is calculated by multiplying the +number of sub-buffers by the sub-buffer size passed into relay_open(). +The idea behind sub-buffers is that they're basically an extension of +double-buffering to N buffers, and they also allow applications to +easily implement random-access-on-buffer-boundary schemes, which can +be important for some high-volume applications. The number and size +of sub-buffers is completely dependent on the application and even for +the same application, different conditions will warrant different +values for these parameters at different times. Typically, the right +values to use are best decided after some experimentation; in general, +though, it's safe to assume that having only 1 sub-buffer is a bad +idea - you're guaranteed to either overwrite data or lose events +depending on the channel mode being used. + +Channel 'modes' +--------------- + +relayfs channels can be used in either of two modes - 'overwrite' or +'no-overwrite'. The mode is entirely determined by the implementation +of the subbuf_start() callback, as described below. In 'overwrite' +mode, also known as 'flight recorder' mode, writes continuously cycle +around the buffer and will never fail, but will unconditionally +overwrite old data regardless of whether it's actually been consumed. +In no-overwrite mode, writes will fail i.e. data will be lost, if the +number of unconsumed sub-buffers equals the total number of +sub-buffers in the channel. It should be clear that if there is no +consumer or if the consumer can't consume sub-buffers fast enought, +data will be lost in either case; the only difference is whether data +is lost from the beginning or the end of a buffer. + +As explained above, a relayfs channel is made of up one or more +per-cpu channel buffers, each implemented as a circular buffer +subdivided into one or more sub-buffers. Messages are written into +the current sub-buffer of the channel's current per-cpu buffer via the +write functions described below. Whenever a message can't fit into +the current sub-buffer, because there's no room left for it, the +client is notified via the subbuf_start() callback that a switch to a +new sub-buffer is about to occur. The client uses this callback to 1) +initialize the next sub-buffer if appropriate 2) finalize the previous +sub-buffer if appropriate and 3) return a boolean value indicating +whether or not to actually go ahead with the sub-buffer switch. + +To implement 'no-overwrite' mode, the userspace client would provide +an implementation of the subbuf_start() callback something like the +following: + +static int subbuf_start(struct rchan_buf *buf, + void *subbuf, + void *prev_subbuf, + unsigned int prev_padding) +{ + if (prev_subbuf) + *((unsigned *)prev_subbuf) = prev_padding; + + if (relay_buf_full(buf)) + return 0; + + subbuf_start_reserve(buf, sizeof(unsigned int)); + + return 1; +} + +If the current buffer is full i.e. all sub-buffers remain unconsumed, +the callback returns 0 to indicate that the buffer switch should not +occur yet i.e. until the consumer has had a chance to read the current +set of ready sub-buffers. For the relay_buf_full() function to make +sense, the consumer is reponsible for notifying relayfs when +sub-buffers have been consumed via relay_subbufs_consumed(). Any +subsequent attempts to write into the buffer will again invoke the +subbuf_start() callback with the same parameters; only when the +consumer has consumed one or more of the ready sub-buffers will +relay_buf_full() return 0, in which case the buffer switch can +continue. + +The implementation of the subbuf_start() callback for 'overwrite' mode +would be very similar: + +static int subbuf_start(struct rchan_buf *buf, + void *subbuf, + void *prev_subbuf, + unsigned int prev_padding) +{ + if (prev_subbuf) + *((unsigned *)prev_subbuf) = prev_padding; + + subbuf_start_reserve(buf, sizeof(unsigned int)); + + return 1; +} + +In this case, the relay_buf_full() check is meaningless and the +callback always returns 1, causing the buffer switch to occur +unconditionally. It's also meaningless for the client to use the +relay_subbufs_consumed() function in this mode, as it's never +consulted. + +The default subbuf_start() implementation, used if the client doesn't +define any callbacks, or doesn't define the subbuf_start() callback, +implements the simplest possible 'no-overwrite' mode i.e. it does +nothing but return 0. + +Header information can be reserved at the beginning of each sub-buffer +by calling the subbuf_start_reserve() helper function from within the +subbuf_start() callback. This reserved area can be used to store +whatever information the client wants. In the example above, room is +reserved in each sub-buffer to store the padding count for that +sub-buffer. This is filled in for the previous sub-buffer in the +subbuf_start() implementation; the padding value for the previous +sub-buffer is passed into the subbuf_start() callback along with a +pointer to the previous sub-buffer, since the padding value isn't +known until a sub-buffer is filled. The subbuf_start() callback is +also called for the first sub-buffer when the channel is opened, to +give the client a chance to reserve space in it. In this case the +previous sub-buffer pointer passed into the callback will be NULL, so +the client should check the value of the prev_subbuf pointer before +writing into the previous sub-buffer. + +Writing to a channel +-------------------- + +kernel clients write data into the current cpu's channel buffer using +relay_write() or __relay_write(). relay_write() is the main logging +function - it uses local_irqsave() to protect the buffer and should be +used if you might be logging from interrupt context. If you know +you'll never be logging from interrupt context, you can use +__relay_write(), which only disables preemption. These functions +don't return a value, so you can't determine whether or not they +failed - the assumption is that you wouldn't want to check a return +value in the fast logging path anyway, and that they'll always succeed +unless the buffer is full and no-overwrite mode is being used, in +which case you can detect a failed write in the subbuf_start() +callback by calling the relay_buf_full() helper function. + +relay_reserve() is used to reserve a slot in a channel buffer which +can be written to later. This would typically be used in applications +that need to write directly into a channel buffer without having to +stage data in a temporary buffer beforehand. Because the actual write +may not happen immediately after the slot is reserved, applications +using relay_reserve() can keep a count of the number of bytes actually +written, either in space reserved in the sub-buffers themselves or as +a separate array. See the 'reserve' example in the relay-apps tarball +at http://relayfs.sourceforge.net for an example of how this can be +done. Because the write is under control of the client and is +separated from the reserve, relay_reserve() doesn't protect the buffer +at all - it's up to the client to provide the appropriate +synchronization when using relay_reserve(). + +Closing a channel +----------------- + +The client calls relay_close() when it's finished using the channel. +The channel and its associated buffers are destroyed when there are no +longer any references to any of the channel buffers. relay_flush() +forces a sub-buffer switch on all the channel buffers, and can be used +to finalize and process the last sub-buffers before the channel is +closed. + +Misc +---- + +Some applications may want to keep a channel around and re-use it +rather than open and close a new channel for each use. relay_reset() +can be used for this purpose - it resets a channel to its initial +state without reallocating channel buffer memory or destroying +existing mappings. It should however only be called when it's safe to +do so i.e. when the channel isn't currently being written to. + +Finally, there are a couple of utility callbacks that can be used for +different purposes. buf_mapped() is called whenever a channel buffer +is mmapped from user space and buf_unmapped() is called when it's +unmapped. The client can use this notification to trigger actions +within the kernel application, such as enabling/disabling logging to +the channel. + + +Resources +========= + +For news, example code, mailing list, etc. see the relayfs homepage: + + http://relayfs.sourceforge.net + + +Credits +======= + +The ideas and specs for relayfs came about as a result of discussions +on tracing involving the following: + +Michel Dagenais <michel.dagenais@polymtl.ca> +Richard Moore <richardj_moore@uk.ibm.com> +Bob Wisniewski <bob@watson.ibm.com> +Karim Yaghmour <karim@opersys.com> +Tom Zanussi <zanussi@us.ibm.com> + +Also thanks to Hubertus Franke for a lot of useful suggestions and bug +reports. diff --git a/fs/Kconfig b/fs/Kconfig index ed78d24ee42..740d6ff0367 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -816,6 +816,18 @@ config RAMFS To compile this as a module, choose M here: the module will be called ramfs. +config RELAYFS_FS + tristate "Relayfs file system support" + ---help--- + Relayfs is a high-speed data relay filesystem designed to provide + an efficient mechanism for tools and facilities to relay large + amounts of data from kernel space to user space. + + To compile this code as a module, choose M here: the module will be + called relayfs. + + If unsure, say N. + endmenu menu "Miscellaneous filesystems" diff --git a/fs/Makefile b/fs/Makefile index cf95eb894fd..15158309dee 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -90,6 +90,7 @@ obj-$(CONFIG_AUTOFS_FS) += autofs/ obj-$(CONFIG_AUTOFS4_FS) += autofs4/ obj-$(CONFIG_ADFS_FS) += adfs/ obj-$(CONFIG_UDF_FS) += udf/ +obj-$(CONFIG_RELAYFS_FS) += relayfs/ obj-$(CONFIG_SUN_OPENPROMFS) += openpromfs/ obj-$(CONFIG_JFS_FS) += jfs/ obj-$(CONFIG_XFS_FS) += xfs/ diff --git a/fs/relayfs/Makefile b/fs/relayfs/Makefile new file mode 100644 index 00000000000..e76e182cdb3 --- /dev/null +++ b/fs/relayfs/Makefile @@ -0,0 +1,4 @@ +obj-$(CONFIG_RELAYFS_FS) += relayfs.o + +relayfs-y := relay.o inode.o buffers.o + diff --git a/fs/relayfs/buffers.c b/fs/relayfs/buffers.c new file mode 100644 index 00000000000..2aa8e271999 --- /dev/null +++ b/fs/relayfs/buffers.c @@ -0,0 +1,189 @@ +/* + * RelayFS buffer management code. + * + * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp + * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com) + * + * This file is released under the GPL. + */ + +#include <linux/module.h> +#include <linux/vmalloc.h> +#include <linux/mm.h> +#include <linux/relayfs_fs.h> +#include "relay.h" +#include "buffers.h" + +/* + * close() vm_op implementation for relayfs file mapping. + */ +static void relay_file_mmap_close(struct vm_area_struct *vma) +{ + struct rchan_buf *buf = vma->vm_private_data; + buf->chan->cb->buf_unmapped(buf, vma->vm_file); +} + +/* + * nopage() vm_op implementation for relayfs file mapping. + */ +static struct page *relay_buf_nopage(struct vm_area_struct *vma, + unsigned long address, + int *type) +{ + struct page *page; + struct rchan_buf *buf = vma->vm_private_data; + unsigned long offset = address - vma->vm_start; + + if (address > vma->vm_end) + return NOPAGE_SIGBUS; /* Disallow mremap */ + if (!buf) + return NOPAGE_OOM; + + page = vmalloc_to_page(buf->start + offset); + if (!page) + return NOPAGE_OOM; + get_page(page); + + if (type) + *type = VM_FAULT_MINOR; + + return page; +} + +/* + * vm_ops for relay file mappings. + */ +static struct vm_operations_struct relay_file_mmap_ops = { + .nopage = relay_buf_nopage, + .close = relay_file_mmap_close, +}; + +/** + * relay_mmap_buf: - mmap channel buffer to process address space + * @buf: relay channel buffer + * @vma: vm_area_struct describing memory to be mapped + * + * Returns 0 if ok, negative on error + * + * Caller should already have grabbed mmap_sem. + */ +int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma) +{ + unsigned long length = vma->vm_end - vma->vm_start; + struct file *filp = vma->vm_file; + + if (!buf) + return -EBADF; + + if (length != (unsigned long)buf->chan->alloc_size) + return -EINVAL; + + vma->vm_ops = &relay_file_mmap_ops; + vma->vm_private_data = buf; + buf->chan->cb->buf_mapped(buf, filp); + + return 0; +} + +/** + * relay_alloc_buf - allocate a channel buffer + * @buf: the buffer struct + * @size: total size of the buffer + * + * Returns a pointer to the resulting buffer, NULL if unsuccessful + */ +static void *relay_alloc_buf(struct rchan_buf *buf, unsigned long size) +{ + void *mem; + unsigned int i, j, n_pages; + + size = PAGE_ALIGN(size); + n_pages = size >> PAGE_SHIFT; + + buf->page_array = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL); + if (!buf->page_array) + return NULL; + + for (i = 0; i < n_pages; i++) { + buf->page_array[i] = alloc_page(GFP_KERNEL); + if (unlikely(!buf->page_array[i])) + goto depopulate; + } + mem = vmap(buf->page_array, n_pages, GFP_KERNEL, PAGE_KERNEL); + if (!mem) + goto depopulate; + + memset(mem, 0, size); + buf->page_count = n_pages; + return mem; + +depopulate: + for (j = 0; j < i; j++) + __free_page(buf->page_array[j]); + kfree(buf->page_array); + return NULL; +} + +/** + * relay_create_buf - allocate and initialize a channel buffer + * @alloc_size: size of the buffer to allocate + * @n_subbufs: number of sub-buffers in the channel + * + * Returns channel buffer if successful, NULL otherwise + */ +struct rchan_buf *relay_create_buf(struct rchan *chan) +{ + struct rchan_buf *buf = kcalloc(1, sizeof(struct rchan_buf), GFP_KERNEL); + if (!buf) + return NULL; + + buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL); + if (!buf->padding) + goto free_buf; + + buf->start = relay_alloc_buf(buf, chan->alloc_size); + if (!buf->start) + goto free_buf; + + buf->chan = chan; + kref_get(&buf->chan->kref); + return buf; + +free_buf: + kfree(buf->padding); + kfree(buf); + return NULL; +} + +/** + * relay_destroy_buf - destroy an rchan_buf struct and associated buffer + * @buf: the buffer struct + */ +void relay_destroy_buf(struct rchan_buf *buf) +{ + struct rchan *chan = buf->chan; + unsigned int i; + + if (likely(buf->start)) { + vunmap(buf->start); + for (i = 0; i < buf->page_count; i++) + __free_page(buf->page_array[i]); + kfree(buf->page_array); + } + kfree(buf->padding); + kfree(buf); + kref_put(&chan->kref, relay_destroy_channel); +} + +/** + * relay_remove_buf - remove a channel buffer + * + * Removes the file from the relayfs fileystem, which also frees the + * rchan_buf_struct and the channel buffer. Should only be called from + * kref_put(). + */ +void relay_remove_buf(struct kref *kref) +{ + struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref); + relayfs_remove(buf->dentry); +} diff --git a/fs/relayfs/buffers.h b/fs/relayfs/buffers.h new file mode 100644 index 00000000000..37a12493f64 --- /dev/null +++ b/fs/relayfs/buffers.h @@ -0,0 +1,12 @@ +#ifndef _BUFFERS_H +#define _BUFFERS_H + +/* This inspired by rtai/shmem */ +#define FIX_SIZE(x) (((x) - 1) & PAGE_MASK) + PAGE_SIZE + +extern int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma); +extern struct rchan_buf *relay_create_buf(struct rchan *chan); +extern void relay_destroy_buf(struct rchan_buf *buf); +extern void relay_remove_buf(struct kref *kref); + +#endif/* _BUFFERS_H */ diff --git a/fs/relayfs/inode.c b/fs/relayfs/inode.c new file mode 100644 index 00000000000..0f7f88d067a --- /dev/null +++ b/fs/relayfs/inode.c @@ -0,0 +1,609 @@ +/* + * VFS-related code for RelayFS, a high-speed data relay filesystem. + * + * Copyright (C) 2003-2005 - Tom Zanussi <zanussi@us.ibm.com>, IBM Corp + * Copyright (C) 2003-2005 - Karim Yaghmour <karim@opersys.com> + * + * Based on ramfs, Copyright (C) 2002 - Linus Torvalds + * + * This file is released under the GPL. + */ + +#include <linux/module.h> +#include <linux/fs.h> +#include <linux/mount.h> +#include <linux/pagemap.h> +#include <linux/init.h> +#include <linux/string.h> +#include <linux/backing-dev.h> +#include <linux/namei.h> +#include <linux/poll.h> +#include <linux/relayfs_fs.h> +#include "relay.h" +#include "buffers.h" + +#define RELAYFS_MAGIC 0xF0B4A981 + +static struct vfsmount * relayfs_mount; +static int relayfs_mount_count; +static kmem_cache_t * relayfs_inode_cachep; + +static struct backing_dev_info relayfs_backing_dev_info = { + .ra_pages = 0, /* No readahead */ + .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK, +}; + +static struct inode *relayfs_get_inode(struct super_block *sb, int mode, + struct rchan *chan) +{ + struct rchan_buf *buf = NULL; + struct inode *inode; + + if (S_ISREG(mode)) { + BUG_ON(!chan); + buf = relay_create_buf(chan); + if (!buf) + return NULL; + } + + inode = new_inode(sb); + if (!inode) { + relay_destroy_buf(buf); + return NULL; + } + + inode->i_mode = mode; + inode->i_uid = 0; + inode->i_gid = 0; + inode->i_blksize = PAGE_CACHE_SIZE; + inode->i_blocks = 0; + inode->i_mapping->backing_dev_info = &relayfs_backing_dev_info; + inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; + switch (mode & S_IFMT) { + case S_IFREG: + inode->i_fop = &relayfs_file_operations; + RELAYFS_I(inode)->buf = buf; + break; + case S_IFDIR: + inode->i_op = &simple_dir_inode_operations; + inode->i_fop = &simple_dir_operations; + + /* directory inodes start off with i_nlink == 2 (for "." entry) */ + inode->i_nlink++; + break; + default: + break; + } + + return inode; +} + +/** + * relayfs_create_entry - create a relayfs directory or file + * @name: the name of the file to create + * @parent: parent directory + * @mode: mode + * @chan: relay channel associated with the file + * + * Returns the new dentry, NULL on failure + * + * Creates a file or directory with the specifed permissions. + */ +static struct dentry *relayfs_create_entry(const char *name, + struct dentry *parent, + int mode, + struct rchan *chan) +{ + struct dentry *d; + struct inode *inode; + int error = 0; + + BUG_ON(!name || !(S_ISREG(mode) || S_ISDIR(mode))); + + error = simple_pin_fs("relayfs", &relayfs_mount, &relayfs_mount_count); + if (error) { + printk(KERN_ERR "Couldn't mount relayfs: errcode %d\n", error); + return NULL; + } + + if (!parent && relayfs_mount && relayfs_mount->mnt_sb) + parent = relayfs_mount->mnt_sb->s_root; + + if (!parent) { + simple_release_fs(&relayfs_mount, &relayfs_mount_count); + return NULL; + } + + parent = dget(parent); + down(&parent->d_inode->i_sem); + d = lookup_one_len(name, parent, strlen(name)); + if (IS_ERR(d)) { + d = NULL; + goto release_mount; + } + + if (d->d_inode) { + d = NULL; + goto release_mount; + } + + inode = relayfs_get_inode(parent->d_inode->i_sb, mode, chan); + if (!inode) { + d = NULL; + goto release_mount; + } + + d_instantiate(d, inode); + dget(d); /* Extra count - pin the dentry in core */ + + if (S_ISDIR(mode)) + parent->d_inode->i_nlink++; + + goto exit; + +release_mount: + simple_release_fs(&relayfs_mount, &relayfs_mount_count); + +exit: + up(&parent->d_inode->i_sem); + dput(parent); + return d; +} + +/** + * relayfs_create_file - create a file in the relay filesystem + * @name: the name of the file to create + * @parent: parent directory + * @mode: mode, if not specied the default perms are used + * @chan: channel associated with the file + * + * Returns file dentry if successful, NULL otherwise. + * + * The file will be created user r on behalf of current user. + */ +struct dentry *relayfs_create_file(const char *name, struct dentry *parent, + int mode, struct rchan *chan) +{ + if (!mode) + mode = S_IRUSR; + mode = (mode & S_IALLUGO) | S_IFREG; + + return relayfs_create_entry(name, parent, mode, chan); +} + +/** + * relayfs_create_dir - create a directory in the relay filesystem + * @name: the name of the directory to create + * @parent: parent directory, NULL if parent should be fs root + * + * Returns directory dentry if successful, NULL otherwise. + * + * The directory will be created world rwx on behalf of current user. + */ +struct dentry *relayfs_create_dir(const char *name, struct dentry *parent) +{ + int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO; + return relayfs_create_entry(name, parent, mode, NULL); +} + +/** + * relayfs_remove - remove a file or directory in the relay filesystem + * @dentry: file or directory dentry + * + * Returns 0 if successful, negative otherwise. + */ +int relayfs_remove(struct dentry *dentry) +{ + struct dentry *parent; + int error = 0; + + if (!dentry) + return -EINVAL; + parent = dentry->d_parent; + if (!parent) + return -EINVAL; + + parent = dget(parent); + down(&parent->d_inode->i_sem); + if (dentry->d_inode) { + if (S_ISDIR(dentry->d_inode->i_mode)) + error = simple_rmdir(parent->d_inode, dentry); + else + error = simple_unlink(parent->d_inode, dentry); + if (!error) + d_delete(dentry); + } + if (!error) + dput(dentry); + up(&parent->d_inode->i_sem); + dput(parent); + + if (!error) + simple_release_fs(&relayfs_mount, &relayfs_mount_count); + + return error; +} + +/** + * relayfs_remove_dir - remove a directory in the relay filesystem + * @dentry: directory dentry + * + * Returns 0 if successful, negative otherwise. + */ +int relayfs_remove_dir(struct dentry *dentry) +{ + return relayfs_remove(dentry); +} + +/** + * relayfs_open - open file op for relayfs files + * @inode: the inode + * @filp: the file + * + * Increments the channel buffer refcount. + */ +static int relayfs_open(struct inode *inode, struct file *filp) +{ + struct rchan_buf *buf = RELAYFS_I(inode)->buf; + kref_get(&buf->kref); + + return 0; +} + +/** + * relayfs_mmap - mmap file op for relayfs files + * @filp: the file + * @vma: the vma describing what to map + * + * Calls upon relay_mmap_buf to map the file into user space. + */ +static int relayfs_mmap(struct file *filp, struct vm_area_struct *vma) +{ + struct inode *inode = filp->f_dentry->d_inode; + return relay_mmap_buf(RELAYFS_I(inode)->buf, vma); +} + +/** + * relayfs_poll - poll file op for relayfs files + * @filp: the file + * @wait: poll table + * + * Poll implemention. + */ +static unsigned int relayfs_poll(struct file *filp, poll_table *wait) +{ + unsigned int mask = 0; + struct inode *inode = filp->f_dentry->d_inode; + struct rchan_buf *buf = RELAYFS_I(inode)->buf; + + if (buf->finalized) + return POLLERR; + + if (filp->f_mode & FMODE_READ) { + poll_wait(filp, &buf->read_wait, wait); + if (!relay_buf_empty(buf)) + mask |= POLLIN | POLLRDNORM; + } + + return mask; +} + +/** + * relayfs_release - release file op for relayfs files + * @inode: the inode + * @filp: the file + * + * Decrements the channel refcount, as the filesystem is + * no longer using it. + */ +static int relayfs_release(struct inode *inode, struct file *filp) +{ + struct rchan_buf *buf = RELAYFS_I(inode)->buf; + kref_put(&buf->kref, relay_remove_buf); + + return 0; +} + +/** + * relayfs_read_consume - update the consumed count for the buffer + */ +static void relayfs_read_consume(struct rchan_buf *buf, + size_t read_pos, + size_t bytes_consumed) +{ + size_t subbuf_size = buf->chan->subbuf_size; + size_t n_subbufs = buf->chan->n_subbufs; + size_t read_subbuf; + + if (buf->bytes_consumed + bytes_consumed > subbuf_size) { + relay_subbufs_consumed(buf->chan, buf->cpu, 1); + buf->bytes_consumed = 0; + } + + buf->bytes_consumed += bytes_consumed; + read_subbuf = read_pos / buf->chan->subbuf_size; + if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) { + if ((read_subbuf == buf->subbufs_produced % n_subbufs) && + (buf->offset == subbuf_size)) + return; + relay_subbufs_consumed(buf->chan, buf->cpu, 1); + buf->bytes_consumed = 0; + } +} + +/** + * relayfs_read_avail - boolean, are there unconsumed bytes available? + */ +static int relayfs_read_avail(struct rchan_buf *buf, size_t read_pos) +{ + size_t bytes_produced, bytes_consumed, write_offset; + size_t subbuf_size = buf->chan->subbuf_size; + size_t n_subbufs = buf->chan->n_subbufs; + size_t produced = buf->subbufs_produced % n_subbufs; + size_t consumed = buf->subbufs_consumed % n_subbufs; + + write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset; + + if (consumed > produced) { + if ((produced > n_subbufs) && + (produced + n_subbufs - consumed <= n_subbufs)) + produced += n_subbufs; + } else if (consumed == produced) { + if (buf->offset > subbuf_size) { + produced += n_subbufs; + if (buf->subbufs_produced == buf->subbufs_consumed) + consumed += n_subbufs; + } + } + + if (buf->offset > subbuf_size) + bytes_produced = (produced - 1) * subbuf_size + write_offset; + else + bytes_produced = produced * subbuf_size + write_offset; + bytes_consumed = consumed * subbuf_size + buf->bytes_consumed; + + if (bytes_produced == bytes_consumed) + return 0; + + relayfs_read_consume(buf, read_pos, 0); + + return 1; +} + +/** + * relayfs_read_subbuf_avail - return bytes available in sub-buffer + */ +static size_t relayfs_read_subbuf_avail(size_t read_pos, + struct rchan_buf *buf) +{ + size_t padding, avail = 0; + size_t read_subbuf, read_offset, write_subbuf, write_offset; + size_t subbuf_size = buf->chan->subbuf_size; + + write_subbuf = (buf->data - buf->start) / subbuf_size; + write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset; + read_subbuf = read_pos / subbuf_size; + read_offset = read_pos % subbuf_size; + padding = buf->padding[read_subbuf]; + + if (read_subbuf == write_subbuf) { + if (read_offset + padding < write_offset) + avail = write_offset - (read_offset + padding); + } else + avail = (subbuf_size - padding) - read_offset; + + return avail; +} + +/** + * relayfs_read_start_pos - find the first available byte to read + * + * If the read_pos is in the middle of padding, return the + * position of the first actually available byte, otherwise + * return the original value. + */ +static size_t relayfs_read_start_pos(size_t read_pos, + struct rchan_buf *buf) +{ + size_t read_subbuf, padding, padding_start, padding_end; + size_ |