direct.c
// SPDX-License-Identifier: GPL-2.0-only
/*
* 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/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/kref.h>
#include <linux/slab.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/module.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_page.h>
#include <linux/sunrpc/clnt.h>
#include <linux/uaccess.h>
#include <linux/atomic.h>
#include "internal.h"
#include "iostat.h"
#include "pnfs.h"
#define NFSDBG_FACILITY NFSDBG_VFS
static struct kmem_cache *nfs_direct_cachep;
struct nfs_direct_req {
struct kref kref; /* release manager */
/* I/O parameters */
struct nfs_open_context *ctx; /* file open context info */
struct nfs_lock_context *l_ctx; /* Lock context info */
struct kiocb * iocb; /* controlling i/o request */
struct inode * inode; /* target file of i/o */
/* completion state */
atomic_t io_count; /* i/os we're waiting for */
spinlock_t lock; /* protect completion state */
loff_t io_start; /* Start offset for I/O */
ssize_t count, /* bytes actually processed */
max_count, /* max expected count */
bytes_left, /* bytes left to be sent */
error; /* any reported error */
struct completion completion; /* wait for i/o completion */
/* commit state */
struct nfs_mds_commit_info mds_cinfo; /* Storage for cinfo */
struct pnfs_ds_commit_info ds_cinfo; /* Storage for cinfo */
struct work_struct work;
int flags;
/* for write */
#define NFS_ODIRECT_DO_COMMIT (1) /* an unstable reply was received */
#define NFS_ODIRECT_RESCHED_WRITES (2) /* write verification failed */
/* for read */
#define NFS_ODIRECT_SHOULD_DIRTY (3) /* dirty user-space page after read */
#define NFS_ODIRECT_DONE INT_MAX /* write verification failed */
};
static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops;
static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops;
static void nfs_direct_write_complete(struct nfs_direct_req *dreq);
static void nfs_direct_write_schedule_work(struct work_struct *work);
static inline void get_dreq(struct nfs_direct_req *dreq)
{
atomic_inc(&dreq->io_count);
}
static inline int put_dreq(struct nfs_direct_req *dreq)
{
return atomic_dec_and_test(&dreq->io_count);
}
static void
nfs_direct_handle_truncated(struct nfs_direct_req *dreq,
const struct nfs_pgio_header *hdr,
ssize_t dreq_len)
{
if (!(test_bit(NFS_IOHDR_ERROR, &hdr->flags) ||
test_bit(NFS_IOHDR_EOF, &hdr->flags)))
return;
if (dreq->max_count >= dreq_len) {
dreq->max_count = dreq_len;
if (dreq->count > dreq_len)
dreq->count = dreq_len;
if (test_bit(NFS_IOHDR_ERROR, &hdr->flags))
dreq->error = hdr->error;
else /* Clear outstanding error if this is EOF */
dreq->error = 0;
}
}
static void
nfs_direct_count_bytes(struct nfs_direct_req *dreq,
const struct nfs_pgio_header *hdr)
{
loff_t hdr_end = hdr->io_start + hdr->good_bytes;
ssize_t dreq_len = 0;
if (hdr_end > dreq->io_start)
dreq_len = hdr_end - dreq->io_start;
nfs_direct_handle_truncated(dreq, hdr, dreq_len);
if (dreq_len > dreq->max_count)
dreq_len = dreq->max_count;
if (dreq->count < dreq_len)
dreq->count = dreq_len;
}
/**
* nfs_direct_IO - NFS address space operation for direct I/O
* @iocb: target I/O control block
* @iter: I/O buffer
*
* The presence of this routine in the address space ops vector means
* the NFS client supports direct I/O. However, for most direct IO, we
* shunt off direct read and write requests before the VFS gets them,
* so this method is only ever called for swap.
*/
ssize_t nfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
struct inode *inode = iocb->ki_filp->f_mapping->host;
/* we only support swap file calling nfs_direct_IO */
if (!IS_SWAPFILE(inode))
return 0;
VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE);
if (iov_iter_rw(iter) == READ)
return nfs_file_direct_read(iocb, iter);
return nfs_file_direct_write(iocb, iter);
}
static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
{
unsigned int i;
for (i = 0; i < npages; i++)
put_page(pages[i]);
}
void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
struct nfs_direct_req *dreq)
{
cinfo->inode = dreq->inode;
cinfo->mds = &dreq->mds_cinfo;
cinfo->ds = &dreq->ds_cinfo;
cinfo->dreq = dreq;
cinfo->completion_ops = &nfs_direct_commit_completion_ops;
}
static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
{
struct nfs_direct_req *dreq;
dreq = kmem_cache_zalloc(nfs_direct_cachep, GFP_KERNEL);
if (!dreq)
return NULL;
kref_init(&dreq->kref);
kref_get(&dreq->kref);
init_completion(&dreq->completion);
INIT_LIST_HEAD(&dreq->mds_cinfo.list);
pnfs_init_ds_commit_info(&dreq->ds_cinfo);
INIT_WORK(&dreq->work, nfs_direct_write_schedule_work);
spin_lock_init(&dreq->lock);
return dreq;
}
static void nfs_direct_req_free(struct kref *kref)
{
struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
pnfs_release_ds_info(&dreq->ds_cinfo, dreq->inode);
if (dreq->l_ctx != NULL)
nfs_put_lock_context(dreq->l_ctx);
if (dreq->ctx != NULL)
put_nfs_open_context(dreq->ctx);
kmem_cache_free(nfs_direct_cachep, dreq);
}
static void nfs_direct_req_release(struct nfs_direct_req *dreq)
{
kref_put(&dreq->kref, nfs_direct_req_free);
}
ssize_t nfs_dreq_bytes_left(struct nfs_direct_req *dreq)
{
return dreq->bytes_left;
}
EXPORT_SYMBOL_GPL(nfs_dreq_bytes_left);
/*
* 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_killable(&dreq->completion);
if (!result) {
result = dreq->count;
WARN_ON_ONCE(dreq->count < 0);
}
if (!result)
result = dreq->error;
out:
return (ssize_t) result;
}
/*
* 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.
*/
static void nfs_direct_complete(struct nfs_direct_req *dreq)
{
struct inode *inode = dreq->inode;
inode_dio_end(inode);
if (dreq->iocb) {
long res = (long) dreq->error;
if (dreq->count != 0) {
res = (long) dreq->count;
WARN_ON_ONCE(dreq->count < 0);
}
dreq->iocb->ki_complete(dreq->iocb, res, 0);
}
complete(&dreq->completion);
nfs_direct_req_release(dreq);
}
static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
{
unsigned long bytes = 0;
struct nfs_direct_req *dreq = hdr->dreq;
spin_lock(&dreq->lock);
if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
spin_unlock(&dreq->lock);
goto out_put;
}
nfs_direct_count_bytes(dreq, hdr);
spin_unlock(&dreq->lock);
while (!list_empty(&hdr->pages)) {
struct nfs_page *req = nfs_list_entry(hdr->pages.next);
struct page *page = req->wb_page;
if (!PageCompound(page) && bytes < hdr->good_bytes &&
(dreq->flags == NFS_ODIRECT_SHOULD_DIRTY))
set_page_dirty(page);
bytes += req->wb_bytes;
nfs_list_remove_request(req);
nfs_release_request(req);
}
out_put:
if (put_dreq(dreq))
nfs_direct_complete(dreq);
hdr->release(hdr);
}
static void nfs_read_sync_pgio_error(struct list_head *head, int error)
{
struct nfs_page *req;
while (!list_empty(head)) {
req = nfs_list_entry(head->next);
nfs_list_remove_request(req);
nfs_release_request(req);
}
}
static void nfs_direct_pgio_init(struct nfs_pgio_header *hdr)
{
get_dreq(hdr->dreq);
}
static const struct nfs_pgio_completion_ops nfs_direct_read_completion_ops = {
.error_cleanup = nfs_read_sync_pgio_error,
.init_hdr = nfs_direct_pgio_init,
.completion = nfs_direct_read_completion,
};
/*
* For each rsize'd chunk of the user's buffer, dispatch an NFS READ
* operation. If nfs_readdata_alloc() or get_user_pages() fails,
* bail and stop sending more reads. Read length accounting is
* handled automatically by nfs_direct_read_result(). Otherwise, if
* no requests have been sent, just return an error.
*/
static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
struct iov_iter *iter,
loff_t pos)
{
struct nfs_pageio_descriptor desc;
struct inode *inode = dreq->inode;
ssize_t result = -EINVAL;
size_t requested_bytes = 0;
size_t rsize = max_t(size_t, NFS_SERVER(inode)->rsize, PAGE_SIZE);
nfs_pageio_init_read(&desc, dreq->inode, false,
&nfs_direct_read_completion_ops);
get_dreq(dreq);
desc.pg_dreq = dreq;
inode_dio_begin(inode);
while (iov_iter_count(iter)) {
struct page **pagevec;
size_t bytes;
size_t pgbase;
unsigned npages, i;
result = iov_iter_get_pages_alloc(iter, &pagevec,
rsize, &pgbase);
if (result < 0)
break;
bytes = result;
iov_iter_advance(iter, bytes);
npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
for (i = 0; i < npages; i++) {
struct nfs_page *req;
unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
/* XXX do we need to do the eof zeroing found in async_filler? */
req = nfs_create_request(dreq->ctx, pagevec[i],
pgbase, req_len);
if (IS_ERR(req)) {
result = PTR_ERR(req);
break;
}
req->wb_index = pos >> PAGE_SHIFT;
req->wb_offset = pos & ~PAGE_MASK;
if (!nfs_pageio_add_request(&desc, req)) {
result = desc.pg_error;
nfs_release_request(req);
break;
}
pgbase = 0;
bytes -= req_len;
requested_bytes += req_len;
pos += req_len;
dreq->bytes_left -= req_len;
}
nfs_direct_release_pages(pagevec, npages);
kvfree(pagevec);
if (result < 0)
break;
}
nfs_pageio_complete(&desc);
/*
* If no bytes were started, return the error, and let the
* generic layer handle the completion.
*/
if (requested_bytes == 0) {
inode_dio_end(inode);
nfs_direct_req_release(dreq);
return result < 0 ? result : -EIO;
}
if (put_dreq(dreq))
nfs_direct_complete(dreq);
return requested_bytes;
}
/**
* nfs_file_direct_read - file direct read operation for NFS files
* @iocb: target I/O control block
* @iter: vector of user buffers into which to read data
*
* 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, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
struct nfs_direct_req *dreq;
struct nfs_lock_context *l_ctx;
ssize_t result, requested;
size_t count = iov_iter_count(iter);
nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
dfprintk(FILE, "NFS: direct read(%pD2, %zd@%Ld)\n",
file, count, (long long) iocb->ki_pos);
result = 0;
if (!count)
goto out;
task_io_account_read(count);
result = -ENOMEM;
dreq = nfs_direct_req_alloc();
if (dreq == NULL)
goto out;
dreq->inode = inode;
dreq->bytes_left = dreq->max_count = count;
dreq->io_start = iocb->ki_pos;
dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
l_ctx = nfs_get_lock_context(dreq->ctx);
if (IS_ERR(l_ctx)) {
result = PTR_ERR(l_ctx);
nfs_direct_req_release(dreq);
goto out_release;
}
dreq->l_ctx = l_ctx;
if (!is_sync_kiocb(iocb))
dreq->iocb = iocb;
if (iter_is_iovec(iter))
dreq->flags = NFS_ODIRECT_SHOULD_DIRTY;
nfs_start_io_direct(inode);
NFS_I(inode)->read_io += count;
requested = nfs_direct_read_schedule_iovec(dreq, iter, iocb->ki_pos);
nfs_end_io_direct(inode);
if (requested > 0) {
result = nfs_direct_wait(dreq);
if (result > 0) {
requested -= result;
iocb->ki_pos += result;
}
iov_iter_revert(iter, requested);
} else {
result = requested;
}
out_release:
nfs_direct_req_release(dreq);
out:
return result;
}
static void
nfs_direct_join_group(struct list_head *list, struct inode *inode)
{
struct nfs_page *req, *next;
list_for_each_entry(req, list, wb_list) {
if (req->wb_head != req || req->wb_this_page == req)
continue;
for (next = req->wb_this_page;
next != req->wb_head;
next = next->wb_this_page) {
nfs_list_remove_request(next);
nfs_release_request(next);
}
nfs_join_page_group(req, inode);
}
}
static void
nfs_direct_write_scan_commit_list(struct inode *inode,
struct list_head *list,
struct nfs_commit_info *cinfo)
{
mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);
pnfs_recover_commit_reqs(list, cinfo);
nfs_scan_commit_list(&cinfo->mds->list, list, cinfo, 0);
mutex_unlock(&NFS_I(cinfo->inode)->commit_mutex);
}
static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
{
struct nfs_pageio_descriptor desc;
struct nfs_page *req, *tmp;
LIST_HEAD(reqs);
struct nfs_commit_info cinfo;
LIST_HEAD(failed);
nfs_init_cinfo_from_dreq(&cinfo, dreq);
nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
nfs_direct_join_group(&reqs, dreq->inode);
dreq->count = 0;
dreq->max_count = 0;
list_for_each_entry(req, &reqs, wb_list)
dreq->max_count += req->wb_bytes;
nfs_clear_pnfs_ds_commit_verifiers(&dreq->ds_cinfo);
get_dreq(dreq);
nfs_pageio_init_write(&desc, dreq->inode, FLUSH_STABLE, false,
&nfs_direct_write_completion_ops);
desc.pg_dreq = dreq;
list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
/* Bump the transmission count */
req->wb_nio++;
if (!nfs_pageio_add_request(&desc, req)) {
nfs_list_move_request(req, &failed);
spin_lock(&cinfo.inode->i_lock);
dreq->flags = 0;
if (desc.pg_error < 0)
dreq->error = desc.pg_error;
else
dreq->error = -EIO;
spin_unlock(&cinfo.inode->i_lock);
}
nfs_release_request(req);
}
nfs_pageio_complete(&desc);
while (!list_empty(&failed)) {
req = nfs_list_entry(failed.next);
nfs_list_remove_request(req);
nfs_unlock_and_release_request(req);
}
if (put_dreq(dreq))
nfs_direct_write_complete(dreq);
}
static void nfs_direct_commit_complete(struct nfs_commit_data *data)
{
const struct nfs_writeverf *verf = data->res.verf;
struct nfs_direct_req *dreq = data->dreq;
struct nfs_commit_info cinfo;
struct nfs_page *req;
int status = data->task.tk_status;
if (status < 0) {
/* Errors in commit are fatal */
dreq->error = status;
dreq->max_count = 0;
dreq->count = 0;
dreq->flags = NFS_ODIRECT_DONE;
} else if (dreq->flags == NFS_ODIRECT_DONE)
status = dreq->error;
nfs_init_cinfo_from_dreq(&cinfo, dreq);
while (!list_empty(&data->pages)) {
req = nfs_list_entry(data->pages.next);
nfs_list_remove_request(req);
if (status >= 0 && !nfs_write_match_verf(verf, req)) {
dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
/*
* Despite the reboot, the write was successful,
* so reset wb_nio.
*/
req->wb_nio = 0;
nfs_mark_request_commit(req, NULL, &cinfo, 0);
} else /* Error or match */
nfs_release_request(req);
nfs_unlock_and_release_request(req);
}
if (atomic_dec_and_test(&cinfo.mds->rpcs_out))
nfs_direct_write_complete(dreq);
}
static void nfs_direct_resched_write(struct nfs_commit_info *cinfo,
struct nfs_page *req)
{
struct nfs_direct_req *dreq = cinfo->dreq;
spin_lock(&dreq->lock);
if (dreq->flags != NFS_ODIRECT_DONE)
dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
spin_unlock(&dreq->lock);
nfs_mark_request_commit(req, NULL, cinfo, 0);
}
static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = {
.completion = nfs_direct_commit_complete,
.resched_write = nfs_direct_resched_write,
};
static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
{
int res;
struct nfs_commit_info cinfo;
LIST_HEAD(mds_list);
nfs_init_cinfo_from_dreq(&cinfo, dreq);
nfs_scan_commit(dreq->inode, &mds_list, &cinfo);
res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo);
if (res < 0) /* res == -ENOMEM */
nfs_direct_write_reschedule(dreq);
}
static void nfs_direct_write_clear_reqs(struct nfs_direct_req *dreq)
{
struct nfs_commit_info cinfo;
struct nfs_page *req;
LIST_HEAD(reqs);
nfs_init_cinfo_from_dreq(&cinfo, dreq);
nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
while (!list_empty(&reqs)) {
req = nfs_list_entry(reqs.next);
nfs_list_remove_request(req);
nfs_release_request(req);
nfs_unlock_and_release_request(req);
}
}
static void nfs_direct_write_schedule_work(struct work_struct *work)
{
struct nfs_direct_req *dreq = container_of(work, struct nfs_direct_req, work);
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_direct_write_clear_reqs(dreq);
nfs_zap_mapping(dreq->inode, dreq->inode->i_mapping);
nfs_direct_complete(dreq);
}
}
static void nfs_direct_write_complete(struct nfs_direct_req *dreq)
{
queue_work(nfsiod_workqueue, &dreq->work); /* Calls nfs_direct_write_schedule_work */
}
static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
{
struct nfs_direct_req *dreq = hdr->dreq;
struct nfs_commit_info cinfo;
bool request_commit = false;
struct nfs_page *req = nfs_list_entry(hdr->pages.next);
nfs_init_cinfo_from_dreq(&cinfo, dreq);
spin_lock(&dreq->lock);
if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
spin_unlock(&dreq->lock);
goto out_put;
}
nfs_direct_count_bytes(dreq, hdr);
if (hdr->good_bytes != 0 && nfs_write_need_commit(hdr)) {
switch (dreq->flags) {
case 0:
dreq->flags = NFS_ODIRECT_DO_COMMIT;
request_commit = true;
break;
case NFS_ODIRECT_RESCHED_WRITES:
case NFS_ODIRECT_DO_COMMIT:
request_commit = true;
}
}
spin_unlock(&dreq->lock);
while (!list_empty(&hdr->pages)) {
req = nfs_list_entry(hdr->pages.next);
nfs_list_remove_request(req);
if (request_commit) {
kref_get(&req->wb_kref);
memcpy(&req->wb_verf, &hdr->verf.verifier,
sizeof(req->wb_verf));
nfs_mark_request_commit(req, hdr->lseg, &cinfo,
hdr->ds_commit_idx);
}
nfs_unlock_and_release_request(req);
}
out_put:
if (put_dreq(dreq))
nfs_direct_write_complete(dreq);
hdr->release(hdr);
}
static void nfs_write_sync_pgio_error(struct list_head *head, int error)
{
struct nfs_page *req;
while (!list_empty(head)) {
req = nfs_list_entry(head->next);
nfs_list_remove_request(req);
nfs_unlock_and_release_request(req);
}
}
static void nfs_direct_write_reschedule_io(struct nfs_pgio_header *hdr)
{
struct nfs_direct_req *dreq = hdr->dreq;
spin_lock(&dreq->lock);
if (dreq->error == 0) {
dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
/* fake unstable write to let common nfs resend pages */
hdr->verf.committed = NFS_UNSTABLE;
hdr->good_bytes = hdr->args.offset + hdr->args.count -
hdr->io_start;
}
spin_unlock(&dreq->lock);
}
static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
.error_cleanup = nfs_write_sync_pgio_error,
.init_hdr = nfs_direct_pgio_init,
.completion = nfs_direct_write_completion,
.reschedule_io = nfs_direct_write_reschedule_io,
};
/*
* NB: Return the value of the first error return code. Subsequent
* errors after the first one are ignored.
*/
/*
* For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
* operation. If nfs_writedata_alloc() or get_user_pages() fails,
* bail and stop sending more writes. Write length accounting is
* handled automatically by nfs_direct_write_result(). Otherwise, if
* no requests have been sent, just return an error.
*/
static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
struct iov_iter *iter,
loff_t pos)
{
struct nfs_pageio_descriptor desc;
struct inode *inode = dreq->inode;
ssize_t result = 0;
size_t requested_bytes = 0;
size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE);
nfs_pageio_init_write(&desc, inode, FLUSH_COND_STABLE, false,
&nfs_direct_write_completion_ops);
desc.pg_dreq = dreq;
get_dreq(dreq);
inode_dio_begin(inode);
NFS_I(inode)->write_io += iov_iter_count(iter);
while (iov_iter_count(iter)) {
struct page **pagevec;
size_t bytes;
size_t pgbase;
unsigned npages, i;
result = iov_iter_get_pages_alloc(iter, &pagevec,
wsize, &pgbase);
if (result < 0)
break;
bytes = result;
iov_iter_advance(iter, bytes);
npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
for (i = 0; i < npages; i++) {
struct nfs_page *req;
unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
req = nfs_create_request(dreq->ctx, pagevec[i],
pgbase, req_len);
if (IS_ERR(req)) {
result = PTR_ERR(req);
break;
}
if (desc.pg_error < 0) {
nfs_free_request(req);
result = desc.pg_error;
break;
}
nfs_lock_request(req);
req->wb_index = pos >> PAGE_SHIFT;
req->wb_offset = pos & ~PAGE_MASK;
if (!nfs_pageio_add_request(&desc, req)) {
result = desc.pg_error;
nfs_unlock_and_release_request(req);
break;
}
pgbase = 0;
bytes -= req_len;
requested_bytes += req_len;
pos += req_len;
dreq->bytes_left -= req_len;
}
nfs_direct_release_pages(pagevec, npages);
kvfree(pagevec);
if (result < 0)
break;
}
nfs_pageio_complete(&desc);
/*
* If no bytes were started, return the error, and let the
* generic layer handle the completion.
*/
if (requested_bytes == 0) {
inode_dio_end(inode);
nfs_direct_req_release(dreq);
return result < 0 ? result : -EIO;
}
if (put_dreq(dreq))
nfs_direct_write_complete(dreq);
return requested_bytes;
}
/**
* nfs_file_direct_write - file direct write operation for NFS files
* @iocb: target I/O control block
* @iter: vector of user buffers from which to write data
*
* 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 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, struct iov_iter *iter)
{
ssize_t result, requested;
size_t count;
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
struct nfs_direct_req *dreq;
struct nfs_lock_context *l_ctx;
loff_t pos, end;
dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
file, iov_iter_count(iter), (long long) iocb->ki_pos);
result = generic_write_checks(iocb, iter);
if (result <= 0)
return result;
count = result;
nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
pos = iocb->ki_pos;
end = (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT;
task_io_account_write(count);
result = -ENOMEM;
dreq = nfs_direct_req_alloc();
if (!dreq)
goto out;
dreq->inode = inode;
dreq->bytes_left = dreq->max_count = count;
dreq->io_start = pos;
dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
l_ctx = nfs_get_lock_context(dreq->ctx);
if (IS_ERR(l_ctx)) {
result = PTR_ERR(l_ctx);
nfs_direct_req_release(dreq);
goto out_release;
}
dreq->l_ctx = l_ctx;
if (!is_sync_kiocb(iocb))
dreq->iocb = iocb;
pnfs_init_ds_commit_info_ops(&dreq->ds_cinfo, inode);
nfs_start_io_direct(inode);
requested = nfs_direct_write_schedule_iovec(dreq, iter, pos);
if (mapping->nrpages) {
invalidate_inode_pages2_range(mapping,
pos >> PAGE_SHIFT, end);
}
nfs_end_io_direct(inode);
if (requested > 0) {
result = nfs_direct_wait(dreq);
if (result > 0) {
requested -= result;
iocb->ki_pos = pos + result;
/* XXX: should check the generic_write_sync retval */
generic_write_sync(iocb, result);
}
iov_iter_revert(iter, requested);
} else {
result = requested;
}
out_release:
nfs_direct_req_release(dreq);
out:
return result;
}
/**
* 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);
if (nfs_direct_cachep == NULL)
return -ENOMEM;
return 0;
}
/**
* nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
*
*/
void nfs_destroy_directcache(void)
{
kmem_cache_destroy(nfs_direct_cachep);
}
