linux/fs/nfs/direct.c
2006-06-25 06:27:31 -04:00

917 lines
25 KiB
C

/*
* 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
* 04 May 2005 support O_DIRECT with aio --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
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 */
/* I/O parameters */
struct list_head list, /* nfs_read/write_data structs */
rewrite_list; /* saved nfs_write_data structs */
struct nfs_open_context *ctx; /* file open context info */
struct kiocb * iocb; /* controlling i/o request */
struct inode * inode; /* target file of i/o */
unsigned long user_addr; /* location of user's buffer */
size_t user_count; /* total bytes to move */
loff_t pos; /* starting offset in file */
struct page ** pages; /* pages in our buffer */
unsigned int npages; /* count of pages */
/* completion state */
spinlock_t lock; /* protect completion state */
int outstanding; /* i/os we're waiting for */
ssize_t count, /* bytes actually processed */
error; /* any reported error */
struct completion completion; /* wait for i/o completion */
/* commit state */
struct nfs_write_data * commit_data; /* special write_data for commits */
int flags;
#define NFS_ODIRECT_DO_COMMIT (1) /* an unstable reply was received */
#define NFS_ODIRECT_RESCHED_WRITES (2) /* write verification failed */
struct nfs_writeverf verf; /* unstable write verifier */
};
static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, int sync);
static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode);
/**
* 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)
{
dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
iocb->ki_filp->f_dentry->d_name.name,
(long long) pos, nr_segs);
return -EINVAL;
}
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 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;
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 (result != page_count) {
/*
* 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) {
nfs_free_user_pages(*pages, result, 0);
result = -EFAULT;
} else
kfree(*pages);
*pages = NULL;
}
}
return result;
}
static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
{
struct nfs_direct_req *dreq;
dreq = kmem_cache_alloc(nfs_direct_cachep, SLAB_KERNEL);
if (!dreq)
return NULL;
kref_init(&dreq->kref);
init_completion(&dreq->completion);
INIT_LIST_HEAD(&dreq->list);
INIT_LIST_HEAD(&dreq->rewrite_list);
dreq->iocb = NULL;
dreq->ctx = NULL;
spin_lock_init(&dreq->lock);
dreq->outstanding = 0;
dreq->count = 0;
dreq->error = 0;
dreq->flags = 0;
return dreq;
}
static void nfs_direct_req_release(struct kref *kref)
{
struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
if (dreq->ctx != NULL)
put_nfs_open_context(dreq->ctx);
kmem_cache_free(nfs_direct_cachep, dreq);
}
/*
* Collects and returns the final error value/byte-count.
*/
static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
{
ssize_t result = -EIOCBQUEUED;
/* Async requests don't wait here */
if (dreq->iocb)
goto out;
result = wait_for_completion_interruptible(&dreq->completion);
if (!result)
result = dreq->error;
if (!result)
result = dreq->count;
out:
kref_put(&dreq->kref, nfs_direct_req_release);
return (ssize_t) result;
}
/*
* 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_wait (for instance, if someone hits ^C on a slow server).
*
* In addition, synchronous I/O uses a stack-allocated iocb. Thus we
* can't trust the iocb is still valid here if this is a synchronous
* request. If the waiter is woken prematurely, the iocb is long gone.
*/
static void nfs_direct_complete(struct nfs_direct_req *dreq)
{
nfs_free_user_pages(dreq->pages, dreq->npages, 1);
if (dreq->iocb) {
long res = (long) dreq->error;
if (!res)
res = (long) dreq->count;
aio_complete(dreq->iocb, res, 0);
}
complete_all(&dreq->completion);
kref_put(&dreq->kref, nfs_direct_req_release);
}
/*
* 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 rpages = (rsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
dreq = nfs_direct_req_alloc();
if (!dreq)
return NULL;
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;
dreq->outstanding++;
if (nbytes <= rsize)
break;
nbytes -= rsize;
}
kref_get(&dreq->kref);
return dreq;
}
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;
spin_lock(&dreq->lock);
if (likely(task->tk_status >= 0))
dreq->count += data->res.count;
else
dreq->error = task->tk_status;
if (--dreq->outstanding) {
spin_unlock(&dreq->lock);
return;
}
spin_unlock(&dreq->lock);
nfs_direct_complete(dreq);
}
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)
{
struct nfs_open_context *ctx = dreq->ctx;
struct inode *inode = ctx->dentry->d_inode;
struct list_head *list = &dreq->list;
struct page **pages = dreq->pages;
size_t count = dreq->user_count;
loff_t pos = dreq->pos;
size_t rsize = NFS_SERVER(inode)->rsize;
unsigned int curpage, pgbase;
curpage = 0;
pgbase = dreq->user_addr & ~PAGE_MASK;
do {
struct nfs_read_data *data;
size_t bytes;
bytes = rsize;
if (count < rsize)
bytes = count;
BUG_ON(list_empty(list));
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 = pos;
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: %5u initiated direct read call (req %s/%Ld, %zu 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);
pos += bytes;
pgbase += bytes;
curpage += pgbase >> PAGE_SHIFT;
pgbase &= ~PAGE_MASK;
count -= bytes;
} while (count != 0);
BUG_ON(!list_empty(list));
}
static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos, 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->user_addr = user_addr;
dreq->user_count = count;
dreq->pos = pos;
dreq->pages = pages;
dreq->npages = nr_pages;
dreq->inode = inode;
dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data);
if (!is_sync_kiocb(iocb))
dreq->iocb = iocb;
nfs_add_stats(inode, NFSIOS_DIRECTREADBYTES, count);
rpc_clnt_sigmask(clnt, &oldset);
nfs_direct_read_schedule(dreq);
result = nfs_direct_wait(dreq);
rpc_clnt_sigunmask(clnt, &oldset);
return result;
}
static void nfs_direct_free_writedata(struct nfs_direct_req *dreq)
{
list_splice_init(&dreq->rewrite_list, &dreq->list);
while (!list_empty(&dreq->list)) {
struct nfs_write_data *data = list_entry(dreq->list.next, struct nfs_write_data, pages);
list_del(&data->pages);
nfs_writedata_release(data);
}
}
#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
{
struct list_head *pos;
list_splice_init(&dreq->rewrite_list, &dreq->list);
list_for_each(pos, &dreq->list)
dreq->outstanding++;
dreq->count = 0;
nfs_direct_write_schedule(dreq, FLUSH_STABLE);
}
static void nfs_direct_commit_result(struct rpc_task *task, void *calldata)
{
struct nfs_write_data *data = calldata;
struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
/* Call the NFS version-specific code */
if (NFS_PROTO(data->inode)->commit_done(task, data) != 0)
return;
if (unlikely(task->tk_status < 0)) {
dreq->error = task->tk_status;
dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
}
if (memcmp(&dreq->verf, &data->verf, sizeof(data->verf))) {
dprintk("NFS: %5u commit verify failed\n", task->tk_pid);
dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
}
dprintk("NFS: %5u commit returned %d\n", task->tk_pid, task->tk_status);
nfs_direct_write_complete(dreq, data->inode);
}
static const struct rpc_call_ops nfs_commit_direct_ops = {
.rpc_call_done = nfs_direct_commit_result,
.rpc_release = nfs_commit_release,
};
static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
{
struct nfs_write_data *data = dreq->commit_data;
data->inode = dreq->inode;
data->cred = dreq->ctx->cred;
data->args.fh = NFS_FH(data->inode);
data->args.offset = dreq->pos;
data->args.count = dreq->user_count;
data->res.count = 0;
data->res.fattr = &data->fattr;
data->res.verf = &data->verf;
rpc_init_task(&data->task, NFS_CLIENT(dreq->inode), RPC_TASK_ASYNC,
&nfs_commit_direct_ops, data);
NFS_PROTO(data->inode)->commit_setup(data, 0);
data->task.tk_priority = RPC_PRIORITY_NORMAL;
data->task.tk_cookie = (unsigned long)data->inode;
/* Note: task.tk_ops->rpc_release will free dreq->commit_data */
dreq->commit_data = NULL;
dprintk("NFS: %5u initiated commit call\n", data->task.tk_pid);
lock_kernel();
rpc_execute(&data->task);
unlock_kernel();
}
static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
{
int flags = dreq->flags;
dreq->flags = 0;
switch (flags) {
case NFS_ODIRECT_DO_COMMIT:
nfs_direct_commit_schedule(dreq);
break;
case NFS_ODIRECT_RESCHED_WRITES:
nfs_direct_write_reschedule(dreq);
break;
default:
nfs_end_data_update(inode);
if (dreq->commit_data != NULL)
nfs_commit_free(dreq->commit_data);
nfs_direct_free_writedata(dreq);
nfs_direct_complete(dreq);
}
}
static void nfs_alloc_commit_data(struct nfs_direct_req *dreq)
{
dreq->commit_data = nfs_commit_alloc(0);
if (dreq->commit_data != NULL)
dreq->commit_data->req = (struct nfs_page *) dreq;
}
#else
static inline void nfs_alloc_commit_data(struct nfs_direct_req *dreq)
{
dreq->commit_data = NULL;
}
static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
{
nfs_end_data_update(inode);
nfs_direct_free_writedata(dreq);
nfs_direct_complete(dreq);
}
#endif
static struct nfs_direct_req *nfs_direct_write_alloc(size_t nbytes, size_t wsize)
{
struct list_head *list;
struct nfs_direct_req *dreq;
unsigned int wpages = (wsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
dreq = nfs_direct_req_alloc();
if (!dreq)
return NULL;
list = &dreq->list;
for(;;) {
struct nfs_write_data *data = nfs_writedata_alloc(wpages);
if (unlikely(!data)) {
while (!list_empty(list)) {
data = list_entry(list->next,
struct nfs_write_data, pages);
list_del(&data->pages);
nfs_writedata_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;
dreq->outstanding++;
if (nbytes <= wsize)
break;
nbytes -= wsize;
}
nfs_alloc_commit_data(dreq);
kref_get(&dreq->kref);
return dreq;
}
static void nfs_direct_write_result(struct rpc_task *task, void *calldata)
{
struct nfs_write_data *data = calldata;
struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
int status = task->tk_status;
if (nfs_writeback_done(task, data) != 0)
return;
spin_lock(&dreq->lock);
if (likely(status >= 0))
dreq->count += data->res.count;
else
dreq->error = task->tk_status;
if (data->res.verf->committed != NFS_FILE_SYNC) {
switch (dreq->flags) {
case 0:
memcpy(&dreq->verf, &data->verf, sizeof(dreq->verf));
dreq->flags = NFS_ODIRECT_DO_COMMIT;
break;
case NFS_ODIRECT_DO_COMMIT:
if (memcmp(&dreq->verf, &data->verf, sizeof(dreq->verf))) {
dprintk("NFS: %5u write verify failed\n", task->tk_pid);
dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
}
}
}
/* In case we have to resend */
data->args.stable = NFS_FILE_SYNC;
spin_unlock(&dreq->lock);
}
/*
* NB: Return the value of the first error return code. Subsequent
* errors after the first one are ignored.
*/
static void nfs_direct_write_release(void *calldata)
{
struct nfs_write_data *data = calldata;
struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
spin_lock(&dreq->lock);
if (--dreq->outstanding) {
spin_unlock(&dreq->lock);
return;
}
spin_unlock(&dreq->lock);
nfs_direct_write_complete(dreq, data->inode);
}
static const struct rpc_call_ops nfs_write_direct_ops = {
.rpc_call_done = nfs_direct_write_result,
.rpc_release = nfs_direct_write_release,
};
/*
* For each nfs_write_data struct that was allocated on the list, dispatch
* an NFS WRITE operation
*/
static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, int sync)
{
struct nfs_open_context *ctx = dreq->ctx;
struct inode *inode = ctx->dentry->d_inode;
struct list_head *list = &dreq->list;
struct page **pages = dreq->pages;
size_t count = dreq->user_count;
loff_t pos = dreq->pos;
size_t wsize = NFS_SERVER(inode)->wsize;
unsigned int curpage, pgbase;
curpage = 0;
pgbase = dreq->user_addr & ~PAGE_MASK;
do {
struct nfs_write_data *data;
size_t bytes;
bytes = wsize;
if (count < wsize)
bytes = count;
BUG_ON(list_empty(list));
data = list_entry(list->next, struct nfs_write_data, pages);
list_move_tail(&data->pages, &dreq->rewrite_list);
data->inode = inode;
data->cred = ctx->cred;
data->args.fh = NFS_FH(inode);
data->args.context = ctx;
data->args.offset = pos;
data->args.pgbase = pgbase;
data->args.pages = &pages[curpage];
data->args.count = bytes;
data->res.fattr = &data->fattr;
data->res.count = bytes;
data->res.verf = &data->verf;
rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
&nfs_write_direct_ops, data);
NFS_PROTO(inode)->write_setup(data, sync);
data->task.tk_priority = RPC_PRIORITY_NORMAL;
data->task.tk_cookie = (unsigned long) inode;
lock_kernel();
rpc_execute(&data->task);
unlock_kernel();
dfprintk(VFS, "NFS: %5u initiated direct write call (req %s/%Ld, %zu 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);
pos += bytes;
pgbase += bytes;
curpage += pgbase >> PAGE_SHIFT;
pgbase &= ~PAGE_MASK;
count -= bytes;
} while (count != 0);
BUG_ON(!list_empty(list));
}
static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos, struct page **pages, 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;
size_t wsize = NFS_SERVER(inode)->wsize;
int sync = 0;
dreq = nfs_direct_write_alloc(count, wsize);
if (!dreq)
return -ENOMEM;
if (dreq->commit_data == NULL || count < wsize)
sync = FLUSH_STABLE;
dreq->user_addr = user_addr;
dreq->user_count = count;
dreq->pos = pos;
dreq->pages = pages;
dreq->npages = nr_pages;
dreq->inode = inode;
dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data);
if (!is_sync_kiocb(iocb))
dreq->iocb = iocb;
nfs_add_stats(inode, NFSIOS_DIRECTWRITTENBYTES, count);
nfs_begin_data_update(inode);
rpc_clnt_sigmask(clnt, &oldset);
nfs_direct_write_schedule(dreq, sync);
result = nfs_direct_wait(dreq);
rpc_clnt_sigunmask(clnt, &oldset);
return result;
}
/**
* 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. 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 (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;
retval = nfs_get_user_pages(READ, (unsigned long) buf,
count, &pages);
if (retval < 0)
goto out;
page_count = retval;
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;
int page_count;
struct page **pages;
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
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 = 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;
retval = -EFAULT;
if (!access_ok(VERIFY_READ, buf, count))
goto out;
retval = nfs_sync_mapping(mapping);
if (retval)
goto out;
retval = nfs_get_user_pages(WRITE, (unsigned long) buf,
count, &pages);
if (retval < 0)
goto out;
page_count = retval;
retval = nfs_direct_write(iocb, (unsigned long) buf, count,
pos, pages, page_count);
/*
* XXX: nfs_end_data_update() already ensures this file's
* cached data is subsequently invalidated. Do we really
* need to call invalidate_inode_pages2() again here?
*
* For aio writes, this invalidation will almost certainly
* occur before the writes complete. Kind of racey.
*/
if (mapping->nrpages)
invalidate_inode_pages2(mapping);
if (retval > 0)
iocb->ki_pos = pos + retval;
out:
return retval;
}
/**
* nfs_init_directcache - create a slab cache for nfs_direct_req structures
*
*/
int __init nfs_init_directcache(void)
{
nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
sizeof(struct nfs_direct_req),
0, (SLAB_RECLAIM_ACCOUNT|
SLAB_MEM_SPREAD),
NULL, NULL);
if (nfs_direct_cachep == NULL)
return -ENOMEM;
return 0;
}
/**
* nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
*
*/
void __exit nfs_destroy_directcache(void)
{
if (kmem_cache_destroy(nfs_direct_cachep))
printk(KERN_INFO "nfs_direct_cache: not all structures were freed\n");
}