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linux/fs/nfs/direct.c

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/*
* linux/fs/nfs/direct.c
*
* Copyright (C) 2003 by Chuck Lever <cel@netapp.com>
*
* High-performance uncached I/O for the Linux NFS client
*
* There are important applications whose performance or correctness
* depends on uncached access to file data. Database clusters
* (multiple copies of the same instance running on separate hosts)
* implement their own cache coherency protocol that subsumes file
* system cache protocols. Applications that process datasets
* considerably larger than the client's memory do not always benefit
* from a local cache. A streaming video server, for instance, has no
* need to cache the contents of a file.
*
* When an application requests uncached I/O, all read and write requests
* are made directly to the server; data stored or fetched via these
* requests is not cached in the Linux page cache. The client does not
* correct unaligned requests from applications. All requested bytes are
* held on permanent storage before a direct write system call returns to
* an application.
*
* Solaris implements an uncached I/O facility called directio() that
* is used for backups and sequential I/O to very large files. Solaris
* also supports uncaching whole NFS partitions with "-o forcedirectio,"
* an undocumented mount option.
*
* Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust, with
* help from Andrew Morton.
*
* 18 Dec 2001 Initial implementation for 2.4 --cel
* 08 Jul 2002 Version for 2.4.19, with bug fixes --trondmy
* 08 Jun 2003 Port to 2.5 APIs --cel
* 31 Mar 2004 Handle direct I/O without VFS support --cel
* 15 Sep 2004 Parallel async reads --cel
*
*/
#include <linux/config.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/smp_lock.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/kref.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_page.h>
#include <linux/sunrpc/clnt.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/atomic.h>
#include "iostat.h"
#define NFSDBG_FACILITY NFSDBG_VFS
#define MAX_DIRECTIO_SIZE (4096UL << PAGE_SHIFT)
static void nfs_free_user_pages(struct page **pages, int npages, int do_dirty);
static kmem_cache_t *nfs_direct_cachep;
/*
* This represents a set of asynchronous requests that we're waiting on
*/
struct nfs_direct_req {
struct kref kref; /* release manager */
struct list_head list; /* nfs_read_data structs */
struct file * filp; /* file descriptor */
struct kiocb * iocb; /* controlling i/o request */
wait_queue_head_t wait; /* wait for i/o completion */
struct inode * inode; /* target file of I/O */
struct page ** pages; /* pages in our buffer */
unsigned int npages; /* count of pages */
atomic_t complete, /* i/os we're waiting for */
count, /* bytes actually processed */
error; /* any reported error */
};
/**
* nfs_direct_IO - NFS address space operation for direct I/O
* @rw: direction (read or write)
* @iocb: target I/O control block
* @iov: array of vectors that define I/O buffer
* @pos: offset in file to begin the operation
* @nr_segs: size of iovec array
*
* The presence of this routine in the address space ops vector means
* the NFS client supports direct I/O. However, we shunt off direct
* read and write requests before the VFS gets them, so this method
* should never be called.
*/
ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t pos, unsigned long nr_segs)
{
struct dentry *dentry = iocb->ki_filp->f_dentry;
dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
dentry->d_name.name, (long long) pos, nr_segs);
return -EINVAL;
}
static inline int nfs_get_user_pages(int rw, unsigned long user_addr, size_t size, struct page ***pages)
{
int result = -ENOMEM;
unsigned long page_count;
size_t array_size;
/* set an arbitrary limit to prevent type overflow */
/* XXX: this can probably be as large as INT_MAX */
if (size > MAX_DIRECTIO_SIZE) {
*pages = NULL;
return -EFBIG;
}
page_count = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT;
page_count -= user_addr >> PAGE_SHIFT;
array_size = (page_count * sizeof(struct page *));
*pages = kmalloc(array_size, GFP_KERNEL);
if (*pages) {
down_read(&current->mm->mmap_sem);
result = get_user_pages(current, current->mm, user_addr,
page_count, (rw == READ), 0,
*pages, NULL);
up_read(&current->mm->mmap_sem);
/*
* If we got fewer pages than expected from get_user_pages(),
* the user buffer runs off the end of a mapping; return EFAULT.
*/
if (result >= 0 && result < page_count) {
nfs_free_user_pages(*pages, result, 0);
*pages = NULL;
result = -EFAULT;
}
}
return result;
}
static void nfs_free_user_pages(struct page **pages, int npages, int do_dirty)
{
int i;
for (i = 0; i < npages; i++) {
struct page *page = pages[i];
if (do_dirty && !PageCompound(page))
set_page_dirty_lock(page);
page_cache_release(page);
}
kfree(pages);
}
static void nfs_direct_req_release(struct kref *kref)
{
struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
kmem_cache_free(nfs_direct_cachep, dreq);
}
/*
* Note we also set the number of requests we have in the dreq when we are
* done. This prevents races with I/O completion so we will always wait
* until all requests have been dispatched and completed.
*/
static struct nfs_direct_req *nfs_direct_read_alloc(size_t nbytes, size_t rsize)
{
struct list_head *list;
struct nfs_direct_req *dreq;
unsigned int reads = 0;
unsigned int rpages = (rsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
dreq = kmem_cache_alloc(nfs_direct_cachep, SLAB_KERNEL);
if (!dreq)
return NULL;
kref_init(&dreq->kref);
init_waitqueue_head(&dreq->wait);
INIT_LIST_HEAD(&dreq->list);
atomic_set(&dreq->count, 0);
atomic_set(&dreq->error, 0);
list = &dreq->list;
for(;;) {
struct nfs_read_data *data = nfs_readdata_alloc(rpages);
if (unlikely(!data)) {
while (!list_empty(list)) {
data = list_entry(list->next,
struct nfs_read_data, pages);
list_del(&data->pages);
nfs_readdata_free(data);
}
kref_put(&dreq->kref, nfs_direct_req_release);
return NULL;
}
INIT_LIST_HEAD(&data->pages);
list_add(&data->pages, list);
data->req = (struct nfs_page *) dreq;
reads++;
if (nbytes <= rsize)
break;
nbytes -= rsize;
}
kref_get(&dreq->kref);
atomic_set(&dreq->complete, reads);
return dreq;
}
/*
* We must hold a reference to all the pages in this direct read request
* until the RPCs complete. This could be long *after* we are woken up in
* nfs_direct_read_wait (for instance, if someone hits ^C on a slow server).
*/
static void nfs_direct_read_result(struct rpc_task *task, void *calldata)
{
struct nfs_read_data *data = calldata;
struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
if (nfs_readpage_result(task, data) != 0)
return;
if (likely(task->tk_status >= 0))
atomic_add(data->res.count, &dreq->count);
else
atomic_set(&dreq->error, task->tk_status);
if (unlikely(atomic_dec_and_test(&dreq->complete))) {
nfs_free_user_pages(dreq->pages, dreq->npages, 1);
wake_up(&dreq->wait);
kref_put(&dreq->kref, nfs_direct_req_release);
}
}
static const struct rpc_call_ops nfs_read_direct_ops = {
.rpc_call_done = nfs_direct_read_result,
.rpc_release = nfs_readdata_release,
};
/*
* For each nfs_read_data struct that was allocated on the list, dispatch
* an NFS READ operation
*/
static void nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t file_offset)
{
struct file *file = dreq->filp;
struct inode *inode = file->f_mapping->host;
struct nfs_open_context *ctx = (struct nfs_open_context *)
file->private_data;
struct list_head *list = &dreq->list;
struct page **pages = dreq->pages;
size_t rsize = NFS_SERVER(inode)->rsize;
unsigned int curpage, pgbase;
curpage = 0;
pgbase = user_addr & ~PAGE_MASK;
do {
struct nfs_read_data *data;
size_t bytes;
bytes = rsize;
if (count < rsize)
bytes = count;
data = list_entry(list->next, struct nfs_read_data, pages);
list_del_init(&data->pages);
data->inode = inode;
data->cred = ctx->cred;
data->args.fh = NFS_FH(inode);
data->args.context = ctx;
data->args.offset = file_offset;
data->args.pgbase = pgbase;
data->args.pages = &pages[curpage];
data->args.count = bytes;
data->res.fattr = &data->fattr;
data->res.eof = 0;
data->res.count = bytes;
rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
&nfs_read_direct_ops, data);
NFS_PROTO(inode)->read_setup(data);
data->task.tk_cookie = (unsigned long) inode;
lock_kernel();
rpc_execute(&data->task);
unlock_kernel();
dfprintk(VFS, "NFS: %4d initiated direct read call (req %s/%Ld, %u bytes @ offset %Lu)\n",
data->task.tk_pid,
inode->i_sb->s_id,
(long long)NFS_FILEID(inode),
bytes,
(unsigned long long)data->args.offset);
file_offset += bytes;
pgbase += bytes;
curpage += pgbase >> PAGE_SHIFT;
pgbase &= ~PAGE_MASK;
count -= bytes;
} while (count != 0);
}
/*
* Collects and returns the final error value/byte-count.
*/
static ssize_t nfs_direct_read_wait(struct nfs_direct_req *dreq, int intr)
{
int result = 0;
if (intr) {
result = wait_event_interruptible(dreq->wait,
(atomic_read(&dreq->complete) == 0));
} else {
wait_event(dreq->wait, (atomic_read(&dreq->complete) == 0));
}
if (!result)
result = atomic_read(&dreq->error);
if (!result)
result = atomic_read(&dreq->count);
kref_put(&dreq->kref, nfs_direct_req_release);
return (ssize_t) result;
}
static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t file_offset, struct page **pages, unsigned int nr_pages)
{
ssize_t result;
sigset_t oldset;
struct inode *inode = iocb->ki_filp->f_mapping->host;
struct rpc_clnt *clnt = NFS_CLIENT(inode);
struct nfs_direct_req *dreq;
dreq = nfs_direct_read_alloc(count, NFS_SERVER(inode)->rsize);
if (!dreq)
return -ENOMEM;
dreq->pages = pages;
dreq->npages = nr_pages;
dreq->inode = inode;
dreq->filp = iocb->ki_filp;
nfs_add_stats(inode, NFSIOS_DIRECTREADBYTES, count);
rpc_clnt_sigmask(clnt, &oldset);
nfs_direct_read_schedule(dreq, user_addr, count, file_offset);
result = nfs_direct_read_wait(dreq, clnt->cl_intr);
rpc_clnt_sigunmask(clnt, &oldset);
return result;
}
static ssize_t nfs_direct_write_seg(struct inode *inode, struct nfs_open_context *ctx, unsigned long user_addr, size_t count, loff_t file_offset, struct page **pages, int nr_pages)
{
const unsigned int wsize = NFS_SERVER(inode)->wsize;
size_t request;
int curpage, need_commit;
ssize_t result, tot_bytes;
struct nfs_writeverf first_verf;
struct nfs_write_data *wdata;
wdata = nfs_writedata_alloc(NFS_SERVER(inode)->wpages);
if (!wdata)
return -ENOMEM;
wdata->inode = inode;
wdata->cred = ctx->cred;
wdata->args.fh = NFS_FH(inode);
wdata->args.context = ctx;
wdata->args.stable = NFS_UNSTABLE;
if (IS_SYNC(inode) || NFS_PROTO(inode)->version == 2 || count <= wsize)
wdata->args.stable = NFS_FILE_SYNC;
wdata->res.fattr = &wdata->fattr;
wdata->res.verf = &wdata->verf;
nfs_begin_data_update(inode);
retry:
need_commit = 0;
tot_bytes = 0;
curpage = 0;
request = count;
wdata->args.pgbase = user_addr & ~PAGE_MASK;
wdata->args.offset = file_offset;
do {
wdata->args.count = request;
if (wdata->args.count > wsize)
wdata->args.count = wsize;
wdata->args.pages = &pages[curpage];
dprintk("NFS: direct write: c=%u o=%Ld ua=%lu, pb=%u, cp=%u\n",
wdata->args.count, (long long) wdata->args.offset,
user_addr + tot_bytes, wdata->args.pgbase, curpage);
lock_kernel();
result = NFS_PROTO(inode)->write(wdata);
unlock_kernel();
if (result <= 0) {
if (tot_bytes > 0)
break;
goto out;
}
if (tot_bytes == 0)
memcpy(&first_verf.verifier, &wdata->verf.verifier,
sizeof(first_verf.verifier));
if (wdata->verf.committed != NFS_FILE_SYNC) {
need_commit = 1;
if (memcmp(&first_verf.verifier, &wdata->verf.verifier,
sizeof(first_verf.verifier)))
goto sync_retry;
}
tot_bytes += result;
/* in case of a short write: stop now, let the app recover */
if (result < wdata->args.count)
break;
wdata->args.offset += result;
wdata->args.pgbase += result;
curpage += wdata->args.pgbase >> PAGE_SHIFT;
wdata->args.pgbase &= ~PAGE_MASK;
request -= result;
} while (request != 0);
/*
* Commit data written so far, even in the event of an error
*/
if (need_commit) {
wdata->args.count = tot_bytes;
wdata->args.offset = file_offset;
lock_kernel();
result = NFS_PROTO(inode)->commit(wdata);
unlock_kernel();
if (result < 0 || memcmp(&first_verf.verifier,
&wdata->verf.verifier,
sizeof(first_verf.verifier)) != 0)
goto sync_retry;
}
result = tot_bytes;
out:
nfs_end_data_update(inode);
nfs_writedata_free(wdata);
return result;
sync_retry:
wdata->args.stable = NFS_FILE_SYNC;
goto retry;
}
/*
* Upon return, generic_file_direct_IO invalidates any cached pages
* that non-direct readers might access, so they will pick up these
* writes immediately.
*/
static ssize_t nfs_direct_write(struct inode *inode, struct nfs_open_context *ctx, const struct iovec *iov, loff_t file_offset, unsigned long nr_segs)
{
ssize_t tot_bytes = 0;
unsigned long seg = 0;
while ((seg < nr_segs) && (tot_bytes >= 0)) {
ssize_t result;
int page_count;
struct page **pages;
const struct iovec *vec = &iov[seg++];
unsigned long user_addr = (unsigned long) vec->iov_base;
size_t size = vec->iov_len;
page_count = nfs_get_user_pages(WRITE, user_addr, size, &pages);
if (page_count < 0) {
nfs_free_user_pages(pages, 0, 0);
if (tot_bytes > 0)
break;
return page_count;
}
nfs_add_stats(inode, NFSIOS_DIRECTWRITTENBYTES, size);
result = nfs_direct_write_seg(inode, ctx, user_addr, size,
file_offset, pages, page_count);
nfs_free_user_pages(pages, page_count, 0);
if (result <= 0) {
if (tot_bytes > 0)
break;
return result;
}
nfs_add_stats(inode, NFSIOS_SERVERWRITTENBYTES, result);
tot_bytes += result;
file_offset += result;
if (result < size)
break;
}
return tot_bytes;
}
/**
* nfs_file_direct_read - file direct read operation for NFS files
* @iocb: target I/O control block
* @buf: user's buffer into which to read data
* count: number of bytes to read
* pos: byte offset in file where reading starts
*
* We use this function for direct reads instead of calling
* generic_file_aio_read() in order to avoid gfar's check to see if
* the request starts before the end of the file. For that check
* to work, we must generate a GETATTR before each direct read, and
* even then there is a window between the GETATTR and the subsequent
* READ where the file size could change. So our preference is simply
* to do all reads the application wants, and the server will take
* care of managing the end of file boundary.
*
* This function also eliminates unnecessarily updating the file's
* atime locally, as the NFS server sets the file's atime, and this
* client must read the updated atime from the server back into its
* cache.
*/
ssize_t nfs_file_direct_read(struct kiocb *iocb, char __user *buf, size_t count, loff_t pos)
{
ssize_t retval = -EINVAL;
int page_count;
struct page **pages;
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
dprintk("nfs: direct read(%s/%s, %lu@%Ld)\n",
file->f_dentry->d_parent->d_name.name,
file->f_dentry->d_name.name,
(unsigned long) count, (long long) pos);
if (!is_sync_kiocb(iocb))
goto out;
if (count < 0)
goto out;
retval = -EFAULT;
if (!access_ok(VERIFY_WRITE, buf, count))
goto out;
retval = 0;
if (!count)
goto out;
retval = nfs_sync_mapping(mapping);
if (retval)
goto out;
page_count = nfs_get_user_pages(READ, (unsigned long) buf,
count, &pages);
if (page_count < 0) {
nfs_free_user_pages(pages, 0, 0);
retval = page_count;
goto out;
}
retval = nfs_direct_read(iocb, (unsigned long) buf, count, pos,
pages, page_count);
if (retval > 0)
iocb->ki_pos = pos + retval;
out:
return retval;
}
/**
* nfs_file_direct_write - file direct write operation for NFS files
* @iocb: target I/O control block
* @buf: user's buffer from which to write data
* count: number of bytes to write
* pos: byte offset in file where writing starts
*
* We use this function for direct writes instead of calling
* generic_file_aio_write() in order to avoid taking the inode
* semaphore and updating the i_size. The NFS server will set
* the new i_size and this client must read the updated size
* back into its cache. We let the server do generic write
* parameter checking and report problems.
*
* We also avoid an unnecessary invocation of generic_osync_inode(),
* as it is fairly meaningless to sync the metadata of an NFS file.
*
* We eliminate local atime updates, see direct read above.
*
* We avoid unnecessary page cache invalidations for normal cached
* readers of this file.
*
* Note that O_APPEND is not supported for NFS direct writes, as there
* is no atomic O_APPEND write facility in the NFS protocol.
*/
ssize_t nfs_file_direct_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t pos)
{
ssize_t retval;
struct file *file = iocb->ki_filp;
struct nfs_open_context *ctx =
(struct nfs_open_context *) file->private_data;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
struct iovec iov = {
.iov_base = (char __user *)buf,
};
dfprintk(VFS, "nfs: direct write(%s/%s, %lu@%Ld)\n",
file->f_dentry->d_parent->d_name.name,
file->f_dentry->d_name.name,
(unsigned long) count, (long long) pos);
retval = -EINVAL;
if (!is_sync_kiocb(iocb))
goto out;
retval = generic_write_checks(file, &pos, &count, 0);
if (retval)
goto out;
retval = -EINVAL;
if ((ssize_t) count < 0)
goto out;
retval = 0;
if (!count)
goto out;
iov.iov_len = count,
retval = -EFAULT;
if (!access_ok(VERIFY_READ, iov.iov_base, iov.iov_len))
goto out;
retval = nfs_sync_mapping(mapping);
if (retval)
goto out;
retval = nfs_direct_write(inode, ctx, &iov, pos, 1);
if (mapping->nrpages)
invalidate_inode_pages2(mapping);
if (retval > 0)
iocb->ki_pos = pos + retval;
out:
return retval;
}
int nfs_init_directcache(void)
{
nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
sizeof(struct nfs_direct_req),
0, SLAB_RECLAIM_ACCOUNT,
NULL, NULL);
if (nfs_direct_cachep == NULL)
return -ENOMEM;
return 0;
}
void nfs_destroy_directcache(void)
{
if (kmem_cache_destroy(nfs_direct_cachep))
printk(KERN_INFO "nfs_direct_cache: not all structures were freed\n");
}
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