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 0000000..d24e1b0 --- /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. @@ -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 cf95eb8..1515830 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 0000000..e76e182 --- /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 0000000..2aa8e27 --- /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 0000000..37a1249 --- /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 0000000..0f7f88d --- /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_t subbuf_size = buf->chan->subbuf_size; + size_t n_subbufs = buf->chan->n_subbufs; + + read_subbuf = read_pos / subbuf_size; + padding = buf->padding[read_subbuf]; + padding_start = (read_subbuf + 1) * subbuf_size - padding; + padding_end = (read_subbuf + 1) * subbuf_size; + if (read_pos >= padding_start && read_pos < padding_end) { + read_subbuf = (read_subbuf + 1) % n_subbufs; + read_pos = read_subbuf * subbuf_size; + } + + return read_pos; +} + +/** + * relayfs_read_end_pos - return the new read position + */ +static size_t relayfs_read_end_pos(struct rchan_buf *buf, + size_t read_pos, + size_t count) +{ + size_t read_subbuf, padding, end_pos; + size_t subbuf_size = buf->chan->subbuf_size; + size_t n_subbufs = buf->chan->n_subbufs; + + read_subbuf = read_pos / subbuf_size; + padding = buf->padding[read_subbuf]; + if (read_pos % subbuf_size + count + padding == subbuf_size) + end_pos = (read_subbuf + 1) * subbuf_size; + else + end_pos = read_pos + count; + if (end_pos >= subbuf_size * n_subbufs) + end_pos = 0; + + return end_pos; +} + +/** + * relayfs_read - read file op for relayfs files + * @filp: the file + * @buffer: the userspace buffer + * @count: number of bytes to read + * @ppos: position to read from + * + * Reads count bytes or the number of bytes available in the + * current sub-buffer being read, whichever is smaller. + */ +static ssize_t relayfs_read(struct file *filp, + char __user *buffer, + size_t count, + loff_t *ppos) +{ + struct inode *inode = filp->f_dentry->d_inode; + struct rchan_buf *buf = RELAYFS_I(inode)->buf; + size_t read_start, avail; + ssize_t ret = 0; + void *from; + + down(&inode->i_sem); + if(!relayfs_read_avail(buf, *ppos)) + goto out; + + read_start = relayfs_read_start_pos(*ppos, buf); + avail = relayfs_read_subbuf_avail(read_start, buf); + if (!avail) + goto out; + + from = buf->start + read_start; + ret = count = min(count, avail); + if (copy_to_user(buffer, from, count)) { + ret = -EFAULT; + goto out; + } + relayfs_read_consume(buf, read_start, count); + *ppos = relayfs_read_end_pos(buf, read_start, count); +out: + up(&inode->i_sem); + return ret; +} + +/** + * relayfs alloc_inode() implementation + */ +static struct inode *relayfs_alloc_inode(struct super_block *sb) +{ + struct relayfs_inode_info *p = kmem_cache_alloc(relayfs_inode_cachep, SLAB_KERNEL); + if (!p) + return NULL; + p->buf = NULL; + + return &p->vfs_inode; +} + +/** + * relayfs destroy_inode() implementation + */ +static void relayfs_destroy_inode(struct inode *inode) +{ + if (RELAYFS_I(inode)->buf) + relay_destroy_buf(RELAYFS_I(inode)->buf); + + kmem_cache_free(relayfs_inode_cachep, RELAYFS_I(inode)); +} + +static void init_once(void *p, kmem_cache_t *cachep, unsigned long flags) +{ + struct relayfs_inode_info *i = p; + if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) == SLAB_CTOR_CONSTRUCTOR) + inode_init_once(&i->vfs_inode); +} + +struct file_operations relayfs_file_operations = { + .open = relayfs_open, + .poll = relayfs_poll, + .mmap = relayfs_mmap, + .read = relayfs_read, + .llseek = no_llseek, + .release = relayfs_release, +}; + +static struct super_operations relayfs_ops = { + .statfs = simple_statfs, + .drop_inode = generic_delete_inode, + .alloc_inode = relayfs_alloc_inode, + .destroy_inode = relayfs_destroy_inode, +}; + +static int relayfs_fill_super(struct super_block * sb, void * data, int silent) +{ + struct inode *inode; + struct dentry *root; + int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO; + + sb->s_blocksize = PAGE_CACHE_SIZE; + sb->s_blocksize_bits = PAGE_CACHE_SHIFT; + sb->s_magic = RELAYFS_MAGIC; + sb->s_op = &relayfs_ops; + inode = relayfs_get_inode(sb, mode, NULL); + + if (!inode) + return -ENOMEM; + + root = d_alloc_root(inode); + if (!root) { + iput(inode); + return -ENOMEM; + } + sb->s_root = root; + + return 0; +} + +static struct super_block * relayfs_get_sb(struct file_system_type *fs_type, + int flags, const char *dev_name, + void *data) +{ + return get_sb_single(fs_type, flags, data, relayfs_fill_super); +} + +static struct file_system_type relayfs_fs_type = { + .owner = THIS_MODULE, + .name = "relayfs", + .get_sb = relayfs_get_sb, + .kill_sb = kill_litter_super, +}; + +static int __init init_relayfs_fs(void) +{ + int err; + + relayfs_inode_cachep = kmem_cache_create("relayfs_inode_cache", + sizeof(struct relayfs_inode_info), 0, + 0, init_once, NULL); + if (!relayfs_inode_cachep) + return -ENOMEM; + + err = register_filesystem(&relayfs_fs_type); + if (err) + kmem_cache_destroy(relayfs_inode_cachep); + + return err; +} + +static void __exit exit_relayfs_fs(void) +{ + unregister_filesystem(&relayfs_fs_type); + kmem_cache_destroy(relayfs_inode_cachep); +} + +module_init(init_relayfs_fs) +module_exit(exit_relayfs_fs) + +EXPORT_SYMBOL_GPL(relayfs_file_operations); +EXPORT_SYMBOL_GPL(relayfs_create_dir); +EXPORT_SYMBOL_GPL(relayfs_remove_dir); + +MODULE_AUTHOR("Tom Zanussi <zanussi@us.ibm.com> and Karim Yaghmour <karim@opersys.com>"); +MODULE_DESCRIPTION("Relay Filesystem"); +MODULE_LICENSE("GPL"); + diff --git a/fs/relayfs/relay.c b/fs/relayfs/relay.c new file mode 100644 index 0000000..16446a1 --- /dev/null +++ b/fs/relayfs/relay.c @@ -0,0 +1,431 @@ +/* + * Public API and common code for RelayFS. + * + * See Documentation/filesystems/relayfs.txt for an overview of relayfs. + * + * 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/errno.h> +#include <linux/stddef.h> +#include <linux/slab.h> +#include <linux/module.h> +#include <linux/string.h> +#include <linux/relayfs_fs.h> +#include "relay.h" +#include "buffers.h" + +/** + * relay_buf_empty - boolean, is the channel buffer empty? + * @buf: channel buffer + * + * Returns 1 if the buffer is empty, 0 otherwise. + */ +int relay_buf_empty(struct rchan_buf *buf) +{ + return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1; +} + +/** + * relay_buf_full - boolean, is the channel buffer full? + * @buf: channel buffer + * + * Returns 1 if the buffer is full, 0 otherwise. + */ +int relay_buf_full(struct rchan_buf *buf) +{ + size_t ready = buf->subbufs_produced - buf->subbufs_consumed; + return (ready >= buf->chan->n_subbufs) ? 1 : 0; +} + +/* + * High-level relayfs kernel API and associated functions. + */ + +/* + * rchan_callback implementations defining default channel behavior. Used + * in place of corresponding NULL values in client callback struct. + */ + +/* + * subbuf_start() default callback. Does nothing. + */ +static int subbuf_start_default_callback (struct rchan_buf *buf, + void *subbuf, + void *prev_subbuf, + size_t prev_padding) +{ + if (relay_buf_full(buf)) + return 0; + + return 1; +} + +/* + * buf_mapped() default callback. Does nothing. + */ +static void buf_mapped_default_callback(struct rchan_buf *buf, + struct file *filp) +{ +} + +/* + * buf_unmapped() default callback. Does nothing. + */ +static void buf_unmapped_default_callback(struct rchan_buf *buf, + struct file *filp) +{ +} + +/* relay channel default callbacks */ +static struct rchan_callbacks default_channel_callbacks = { + .subbuf_start = subbuf_start_default_callback, + .buf_mapped = buf_mapped_default_callback, + .buf_unmapped = buf_unmapped_default_callback, +}; + +/** + * wakeup_readers - wake up readers waiting on a channel + * @private: the channel buffer + * + * This is the work function used to defer reader waking. The + * reason waking is deferred is that calling directly from write + * causes problems if you're writing from say the scheduler. + */ +static void wakeup_readers(void *private) +{ + struct rchan_buf *buf = private; + wake_up_interruptible(&buf->read_wait); +} + +/** + * __relay_reset - reset a channel buffer + * @buf: the channel buffer + * @init: 1 if this is a first-time initialization + * + * See relay_reset for description of effect. + */ +static inline void __relay_reset(struct rchan_buf *buf, unsigned int init) +{ + size_t i; + + if (init) { + init_waitqueue_head(&buf->read_wait); + kref_init(&buf->kref); + INIT_WORK(&buf->wake_readers, NULL, NULL); + } else { + cancel_delayed_work(&buf->wake_readers); + flush_scheduled_work(); + } + + buf->subbufs_produced = 0; + buf->subbufs_consumed = 0; + buf->bytes_consumed = 0; + buf->finalized = 0; + buf->data = buf->start; + buf->offset = 0; + + for (i = 0; i < buf->chan->n_subbufs; i++) + buf->padding[i] = 0; + + buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0); +} + +/** + * relay_reset - reset the channel + * @chan: the channel + * + * This has the effect of erasing all data from all channel buffers + * and restarting the channel in its initial state. The buffers + * are not freed, so any mappings are still in effect. + * + * NOTE: Care should be taken that the channel isn't actually + * being used by anything when this call is made. + */ +void relay_reset(struct rchan *chan) +{ + unsigned int i; + + if (!chan) + return; + + for (i = 0; i < NR_CPUS; i++) { + if (!chan->buf[i]) + continue; + __relay_reset(chan->buf[i], 0); + } +} + +/** + * relay_open_buf - create a new channel buffer in relayfs + * + * Internal - used by relay_open(). + */ +static struct rchan_buf *relay_open_buf(struct rchan *chan, + const char *filename, + struct dentry *parent) +{ + struct rchan_buf *buf; + struct dentry *dentry; + + /* Create file in fs */ + dentry = relayfs_create_file(filename, parent, S_IRUSR, chan); + if (!dentry) + return NULL; + + buf = RELAYFS_I(dentry->d_inode)->buf; + buf->dentry = dentry; + __relay_reset(buf, 1); + + return buf; +} + +/** + * relay_close_buf - close a channel buffer + * @buf: channel buffer + * + * Marks the buffer finalized and restores the default callbacks. + * The channel buffer and channel buffer data structure are then freed + * automatically when the last reference is given up. + */ +static inline void relay_close_buf(struct rchan_buf *buf) +{ + buf->finalized = 1; + buf->chan->cb = &default_channel_callbacks; + cancel_delayed_work(&buf->wake_readers); + flush_scheduled_work(); + kref_put(&buf->kref, relay_remove_buf); +} + +static inline void setup_callbacks(struct rchan *chan, + struct rchan_callbacks *cb) +{ + if (!cb) { + chan->cb = &default_channel_callbacks; + return; + } + + if (!cb->subbuf_start) + cb->subbuf_start = subbuf_start_default_callback; + if (!cb->buf_mapped) + cb->buf_mapped = buf_mapped_default_callback; + if (!cb->buf_unmapped) + cb->buf_unmapped = buf_unmapped_default_callback; + chan->cb = cb; +} + +/** + * relay_open - create a new relayfs channel + * @base_filename: base name of files to create + * @parent: dentry of parent directory, NULL for root directory + * @subbuf_size: size of sub-buffers + * @n_subbufs: number of sub-buffers + * @cb: client callback functions + * + * Returns channel pointer if successful, NULL otherwise. + * + * Creates a channel buffer for each cpu using the sizes and + * attributes specified. The created channel buffer files + * will be named base_filename0...base_filenameN-1. File + * permissions will be S_IRUSR. + */ +struct rchan *relay_open(const char *base_filename, + struct dentry *parent, + size_t subbuf_size, + size_t n_subbufs, + struct rchan_callbacks *cb) +{ + unsigned int i; + struct rchan *chan; + char *tmpname; + + if (!base_filename) + return NULL; + + if (!(subbuf_size && n_subbufs)) + return NULL; + + chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL); + if (!chan) + return NULL; + + chan->version = RELAYFS_CHANNEL_VERSION; + chan->n_subbufs = n_subbufs; + chan->subbuf_size = subbuf_size; + chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs); + setup_callbacks(chan, cb); + kref_init(&chan->kref); + + tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL); + if (!tmpname) + goto free_chan; + + for_each_online_cpu(i) { + sprintf(tmpname, "%s%d", base_filename, i); + chan->buf[i] = relay_open_buf(chan, tmpname, parent); + chan->buf[i]->cpu = i; + if (!chan->buf[i]) + goto free_bufs; + } + + kfree(tmpname); + return chan; + +free_bufs: + for (i = 0; i < NR_CPUS; i++) { + if (!chan->buf[i]) + break; + relay_close_buf(chan->buf[i]); + } + kfree(tmpname); + +free_chan: + kref_put(&chan->kref, relay_destroy_channel); + return NULL; +} + +/** + * relay_switch_subbuf - switch to a new sub-buffer + * @buf: channel buffer + * @length: size of current event + * + * Returns either the length passed in or 0 if full. + + * Performs sub-buffer-switch tasks such as invoking callbacks, + * updating padding counts, waking up readers, etc. + */ +size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length) +{ + void *old, *new; + size_t old_subbuf, new_subbuf; + + if (unlikely(length > buf->chan->subbuf_size)) + goto toobig; + + if (buf->offset != buf->chan->subbuf_size + 1) { + buf->prev_padding = buf->chan->subbuf_size - buf->offset; + old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs; + buf->padding[old_subbuf] = buf->prev_padding; + buf->subbufs_produced++; + if (waitqueue_active(&buf->read_wait)) { + PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf); + schedule_delayed_work(&buf->wake_readers, 1); + } + } + + old = buf->data; + new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs; + new = buf->start + new_subbuf * buf->chan->subbuf_size; + buf->offset = 0; + if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) { + buf->offset = buf->chan->subbuf_size + 1; + return 0; + } + buf->data = new; + buf->padding[new_subbuf] = 0; + + if (unlikely(length + buf->offset > buf->chan->subbuf_size)) + goto toobig; + + return length; + +toobig: + printk(KERN_WARNING "relayfs: event too large (%Zd)\n", length); + WARN_ON(1); + return 0; +} + +/** + * relay_subbufs_consumed - update the buffer's sub-buffers-consumed count + * @chan: the channel + * @cpu: the cpu associated with the channel buffer to update + * @subbufs_consumed: number of sub-buffers to add to current buf's count + * + * Adds to the channel buffer's consumed sub-buffer count. + * subbufs_consumed should be the number of sub-buffers newly consumed, + * not the total consumed. + * + * NOTE: kernel clients don't need to call this function if the channel + * mode is 'overwrite'. + */ +void relay_subbufs_consumed(struct rchan *chan, + unsigned int cpu, + size_t subbufs_consumed) +{ + struct rchan_buf *buf; + + if (!chan) + return; + + if (cpu >= NR_CPUS || !chan->buf[cpu]) + return; + + buf = chan->buf[cpu]; + buf->subbufs_consumed += subbufs_consumed; + if (buf->subbufs_consumed > buf->subbufs_produced) + buf->subbufs_consumed = buf->subbufs_produced; +} + +/** + * relay_destroy_channel - free the channel struct + * + * Should only be called from kref_put(). + */ +void relay_destroy_channel(struct kref *kref) +{ + struct rchan *chan = container_of(kref, struct rchan, kref); + kfree(chan); +} + +/** + * relay_close - close the channel + * @chan: the channel + * + * Closes all channel buffers and frees the channel. + */ +void relay_close(struct rchan *chan) +{ + unsigned int i; + + if (!chan) + return; + + for (i = 0; i < NR_CPUS; i++) { + if (!chan->buf[i]) + continue; + relay_close_buf(chan->buf[i]); + } + + kref_put(&chan->kref, relay_destroy_channel); +} + +/** + * relay_flush - close the channel + * @chan: the channel + * + * Flushes all channel buffers i.e. forces buffer switch. + */ +void relay_flush(struct rchan *chan) +{ + unsigned int i; + + if (!chan) + return; + + for (i = 0; i < NR_CPUS; i++) { + if (!chan->buf[i]) + continue; + relay_switch_subbuf(chan->buf[i], 0); + } +} + +EXPORT_SYMBOL_GPL(relay_open); +EXPORT_SYMBOL_GPL(relay_close); +EXPORT_SYMBOL_GPL(relay_flush); +EXPORT_SYMBOL_GPL(relay_reset); +EXPORT_SYMBOL_GPL(relay_subbufs_consumed); +EXPORT_SYMBOL_GPL(relay_switch_subbuf); +EXPORT_SYMBOL_GPL(relay_buf_full); diff --git a/fs/relayfs/relay.h b/fs/relayfs/relay.h new file mode 100644 index 0000000..703503f --- /dev/null +++ b/fs/relayfs/relay.h @@ -0,0 +1,12 @@ +#ifndef _RELAY_H +#define _RELAY_H + +struct dentry *relayfs_create_file(const char *name, + struct dentry *parent, + int mode, + struct rchan *chan); +extern int relayfs_remove(struct dentry *dentry); +extern int relay_buf_empty(struct rchan_buf *buf); +extern void relay_destroy_channel(struct kref *kref); + +#endif /* _RELAY_H */ diff --git a/include/linux/relayfs_fs.h b/include/linux/relayfs_fs.h new file mode 100644 index 0000000..cfafc3e --- /dev/null +++ b/include/linux/relayfs_fs.h @@ -0,0 +1,255 @@ +/* + * linux/include/linux/relayfs_fs.h + * + * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp + * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com) + * + * RelayFS definitions and declarations + */ + +#ifndef _LINUX_RELAYFS_FS_H +#define _LINUX_RELAYFS_FS_H + +#include <linux/config.h> +#include <linux/types.h> +#include <linux/sched.h> +#include <linux/wait.h> +#include <linux/list.h> +#include <linux/fs.h> +#include <linux/poll.h> +#include <linux/kref.h> + +/* + * Tracks changes to rchan_buf struct + */ +#define RELAYFS_CHANNEL_VERSION 5 + +/* + * Per-cpu relay channel buffer + */ +struct rchan_buf +{ + void *start; /* start of channel buffer */ + void *data; /* start of current sub-buffer */ + size_t offset; /* current offset into sub-buffer */ + size_t subbufs_produced; /* count of sub-buffers produced */ + size_t subbufs_consumed; /* count of sub-buffers consumed */ + struct rchan *chan; /* associated channel */ + wait_queue_head_t read_wait; /* reader wait queue */ + struct work_struct wake_readers; /* reader wake-up work struct */ + struct dentry *dentry; /* channel file dentry */ + struct kref kref; /* channel buffer refcount */ + struct page **page_array; /* array of current buffer pages */ + unsigned int page_count; /* number of current buffer pages */ + unsigned int finalized; /* buffer has been finalized */ + size_t *padding; /* padding counts per sub-buffer */ + size_t prev_padding; /* temporary variable */ + size_t bytes_consumed; /* bytes consumed in cur read subbuf */ + unsigned int cpu; /* this buf's cpu */ +} ____cacheline_aligned; + +/* + * Relay channel data structure + */ +struct rchan +{ + u32 version; /* the version of this struct */ + size_t subbuf_size; /* sub-buffer size */ + size_t n_subbufs; /* number of sub-buffers per buffer */ + size_t alloc_size; /* total buffer size allocated */ + struct rchan_callbacks *cb; /* client callbacks */ + struct kref kref; /* channel refcount */ + void *private_data; /* for user-defined data */ + struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */ +}; + +/* + * Relayfs inode + */ +struct relayfs_inode_info +{ + struct inode vfs_inode; + struct rchan_buf *buf; +}; + +static inline struct relayfs_inode_info *RELAYFS_I(struct inode *inode) +{ + return container_of(inode, struct relayfs_inode_info, vfs_inode); +} + +/* + * Relay channel client callbacks + */ +struct rchan_callbacks +{ + /* + * subbuf_start - called on buffer-switch to a new sub-buffer + * @buf: the channel buffer containing the new sub-buffer + * @subbuf: the start of the new sub-buffer + * @prev_subbuf: the start of the previous sub-buffer + * @prev_padding: unused space at the end of previous sub-buffer + * + * The client should return 1 to continue logging, 0 to stop + * logging. + * + * NOTE: subbuf_start will also be invoked when the buffer is + * created, so that the first sub-buffer can be initialized + * if necessary. In this case, prev_subbuf will be NULL. + * + * NOTE: the client can reserve bytes at the beginning of the new + * sub-buffer by calling subbuf_start_reserve() in this callback. + */ + int (*subbuf_start) (struct rchan_buf *buf, + void *subbuf, + void *prev_subbuf, + size_t prev_padding); + + /* + * buf_mapped - relayfs buffer mmap notification + * @buf: the channel buffer + * @filp: relayfs file pointer + * + * Called when a relayfs file is successfully mmapped + */ + void (*buf_mapped)(struct rchan_buf *buf, + struct file *filp); + + /* + * buf_unmapped - relayfs buffer unmap notification + * @buf: the channel buffer + * @filp: relayfs file pointer + * + * Called when a relayfs file is successfully unmapped + */ + void (*buf_unmapped)(struct rchan_buf *buf, + struct file *filp); +}; + +/* + * relayfs kernel API, fs/relayfs/relay.c + */ + +struct rchan *relay_open(const char *base_filename, + struct dentry *parent, + size_t subbuf_size, + size_t n_subbufs, + struct rchan_callbacks *cb); +extern void relay_close(struct rchan *chan); +extern void relay_flush(struct rchan *chan); +extern void relay_subbufs_consumed(struct rchan *chan, + unsigned int cpu, + size_t consumed); +extern void relay_reset(struct rchan *chan); +extern int relay_buf_full(struct rchan_buf *buf); + +extern size_t relay_switch_subbuf(struct rchan_buf *buf, + size_t length); +extern struct dentry *relayfs_create_dir(const char *name, + struct dentry *parent); +extern int relayfs_remove_dir(struct dentry *dentry); + +/** + * relay_write - write data into the channel + * @chan: relay channel + * @data: data to be written + * @length: number of bytes to write + * + * Writes data into the current cpu's channel buffer. + * + * Protects the buffer by disabling interrupts. Use this + * if you might be logging from interrupt context. Try + * __relay_write() if you know you won't be logging from + * interrupt context. + */ +static inline void relay_write(struct rchan *chan, + const void *data, + size_t length) +{ + unsigned long flags; + struct rchan_buf *buf; + + local_irq_save(flags); + buf = chan->buf[smp_processor_id()]; + if (unlikely(buf->offset + length > chan->subbuf_size)) + length = relay_switch_subbuf(buf, length); + memcpy(buf->data + buf->offset, data, length); + buf->offset += length; + local_irq_restore(flags); +} + +/** + * __relay_write - write data into the channel + * @chan: relay channel + * @data: data to be written + * @length: number of bytes to write + * + * Writes data into the current cpu's channel buffer. + * + * Protects the buffer by disabling preemption. Use + * relay_write() if you might be logging from interrupt + * context. + */ +static inline void __relay_write(struct rchan *chan, + const void *data, + size_t length) +{ + struct rchan_buf *buf; + + buf = chan->buf[get_cpu()]; + if (unlikely(buf->offset + length > buf->chan->subbuf_size)) + length = relay_switch_subbuf(buf, length); + memcpy(buf->data + buf->offset, data, length); + buf->offset += length; + put_cpu(); +} + +/** + * relay_reserve - reserve slot in channel buffer + * @chan: relay channel + * @length: number of bytes to reserve + * + * Returns pointer to reserved slot, NULL if full. + * + * Reserves a slot in the current cpu's channel buffer. + * Does not protect the buffer at all - caller must provide + * appropriate synchronization. + */ +static inline void *relay_reserve(struct rchan *chan, size_t length) +{ + void *reserved; + struct rchan_buf *buf = chan->buf[smp_processor_id()]; + + if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { + length = relay_switch_subbuf(buf, length); + if (!length) + return NULL; + } + reserved = buf->data + buf->offset; + buf->offset += length; + + return reserved; +} + +/** + * subbuf_start_reserve - reserve bytes at the start of a sub-buffer + * @buf: relay channel buffer + * @length: number of bytes to reserve + * + * Helper function used to reserve bytes at the beginning of + * a sub-buffer in the subbuf_start() callback. + */ +static inline void subbuf_start_reserve(struct rchan_buf *buf, + size_t length) +{ + BUG_ON(length >= buf->chan->subbuf_size - 1); + buf->offset = length; +} + +/* + * exported relayfs file operations, fs/relayfs/inode.c + */ + +extern struct file_operations relayfs_file_operations; + +#endif /* _LINUX_RELAYFS_FS_H */ + |