linux/fs/nfs/pagelist.c

455 lines
11 KiB
C

/*
* linux/fs/nfs/pagelist.c
*
* A set of helper functions for managing NFS read and write requests.
* The main purpose of these routines is to provide support for the
* coalescing of several requests into a single RPC call.
*
* Copyright 2000, 2001 (c) Trond Myklebust <trond.myklebust@fys.uio.no>
*
*/
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/sched.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs.h>
#include <linux/nfs3.h>
#include <linux/nfs4.h>
#include <linux/nfs_page.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/export.h>
#include "internal.h"
#include "pnfs.h"
static struct kmem_cache *nfs_page_cachep;
bool nfs_pgarray_set(struct nfs_page_array *p, unsigned int pagecount)
{
p->npages = pagecount;
if (pagecount <= ARRAY_SIZE(p->page_array))
p->pagevec = p->page_array;
else {
p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_KERNEL);
if (!p->pagevec)
p->npages = 0;
}
return p->pagevec != NULL;
}
void nfs_pgheader_init(struct nfs_pageio_descriptor *desc,
struct nfs_pgio_header *hdr,
void (*release)(struct nfs_pgio_header *hdr))
{
hdr->req = nfs_list_entry(desc->pg_list.next);
hdr->inode = desc->pg_inode;
hdr->cred = hdr->req->wb_context->cred;
hdr->io_start = req_offset(hdr->req);
hdr->good_bytes = desc->pg_count;
hdr->release = release;
hdr->completion_ops = desc->pg_completion_ops;
}
void nfs_set_pgio_error(struct nfs_pgio_header *hdr, int error, loff_t pos)
{
spin_lock(&hdr->lock);
if (pos < hdr->io_start + hdr->good_bytes) {
set_bit(NFS_IOHDR_ERROR, &hdr->flags);
clear_bit(NFS_IOHDR_EOF, &hdr->flags);
hdr->good_bytes = pos - hdr->io_start;
hdr->error = error;
}
spin_unlock(&hdr->lock);
}
static inline struct nfs_page *
nfs_page_alloc(void)
{
struct nfs_page *p = kmem_cache_zalloc(nfs_page_cachep, GFP_KERNEL);
if (p)
INIT_LIST_HEAD(&p->wb_list);
return p;
}
static inline void
nfs_page_free(struct nfs_page *p)
{
kmem_cache_free(nfs_page_cachep, p);
}
/**
* nfs_create_request - Create an NFS read/write request.
* @ctx: open context to use
* @inode: inode to which the request is attached
* @page: page to write
* @offset: starting offset within the page for the write
* @count: number of bytes to read/write
*
* The page must be locked by the caller. This makes sure we never
* create two different requests for the same page.
* User should ensure it is safe to sleep in this function.
*/
struct nfs_page *
nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
struct page *page,
unsigned int offset, unsigned int count)
{
struct nfs_page *req;
/* try to allocate the request struct */
req = nfs_page_alloc();
if (req == NULL)
return ERR_PTR(-ENOMEM);
/* get lock context early so we can deal with alloc failures */
req->wb_lock_context = nfs_get_lock_context(ctx);
if (req->wb_lock_context == NULL) {
nfs_page_free(req);
return ERR_PTR(-ENOMEM);
}
/* Initialize the request struct. Initially, we assume a
* long write-back delay. This will be adjusted in
* update_nfs_request below if the region is not locked. */
req->wb_page = page;
req->wb_index = page->index;
page_cache_get(page);
BUG_ON(PagePrivate(page));
BUG_ON(!PageLocked(page));
BUG_ON(page->mapping->host != inode);
req->wb_offset = offset;
req->wb_pgbase = offset;
req->wb_bytes = count;
req->wb_context = get_nfs_open_context(ctx);
kref_init(&req->wb_kref);
return req;
}
/**
* nfs_unlock_request - Unlock request and wake up sleepers.
* @req:
*/
void nfs_unlock_request(struct nfs_page *req)
{
if (!NFS_WBACK_BUSY(req)) {
printk(KERN_ERR "NFS: Invalid unlock attempted\n");
BUG();
}
smp_mb__before_clear_bit();
clear_bit(PG_BUSY, &req->wb_flags);
smp_mb__after_clear_bit();
wake_up_bit(&req->wb_flags, PG_BUSY);
nfs_release_request(req);
}
/*
* nfs_clear_request - Free up all resources allocated to the request
* @req:
*
* Release page and open context resources associated with a read/write
* request after it has completed.
*/
static void nfs_clear_request(struct nfs_page *req)
{
struct page *page = req->wb_page;
struct nfs_open_context *ctx = req->wb_context;
struct nfs_lock_context *l_ctx = req->wb_lock_context;
if (page != NULL) {
page_cache_release(page);
req->wb_page = NULL;
}
if (l_ctx != NULL) {
nfs_put_lock_context(l_ctx);
req->wb_lock_context = NULL;
}
if (ctx != NULL) {
put_nfs_open_context(ctx);
req->wb_context = NULL;
}
}
/**
* nfs_release_request - Release the count on an NFS read/write request
* @req: request to release
*
* Note: Should never be called with the spinlock held!
*/
static void nfs_free_request(struct kref *kref)
{
struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
/* Release struct file and open context */
nfs_clear_request(req);
nfs_page_free(req);
}
void nfs_release_request(struct nfs_page *req)
{
kref_put(&req->wb_kref, nfs_free_request);
}
static int nfs_wait_bit_uninterruptible(void *word)
{
io_schedule();
return 0;
}
/**
* nfs_wait_on_request - Wait for a request to complete.
* @req: request to wait upon.
*
* Interruptible by fatal signals only.
* The user is responsible for holding a count on the request.
*/
int
nfs_wait_on_request(struct nfs_page *req)
{
return wait_on_bit(&req->wb_flags, PG_BUSY,
nfs_wait_bit_uninterruptible,
TASK_UNINTERRUPTIBLE);
}
bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *prev, struct nfs_page *req)
{
/*
* FIXME: ideally we should be able to coalesce all requests
* that are not block boundary aligned, but currently this
* is problematic for the case of bsize < PAGE_CACHE_SIZE,
* since nfs_flush_multi and nfs_pagein_multi assume you
* can have only one struct nfs_page.
*/
if (desc->pg_bsize < PAGE_SIZE)
return 0;
return desc->pg_count + req->wb_bytes <= desc->pg_bsize;
}
EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
/**
* nfs_pageio_init - initialise a page io descriptor
* @desc: pointer to descriptor
* @inode: pointer to inode
* @doio: pointer to io function
* @bsize: io block size
* @io_flags: extra parameters for the io function
*/
void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
struct inode *inode,
const struct nfs_pageio_ops *pg_ops,
const struct nfs_pgio_completion_ops *compl_ops,
size_t bsize,
int io_flags)
{
INIT_LIST_HEAD(&desc->pg_list);
desc->pg_bytes_written = 0;
desc->pg_count = 0;
desc->pg_bsize = bsize;
desc->pg_base = 0;
desc->pg_moreio = 0;
desc->pg_recoalesce = 0;
desc->pg_inode = inode;
desc->pg_ops = pg_ops;
desc->pg_completion_ops = compl_ops;
desc->pg_ioflags = io_flags;
desc->pg_error = 0;
desc->pg_lseg = NULL;
}
/**
* nfs_can_coalesce_requests - test two requests for compatibility
* @prev: pointer to nfs_page
* @req: pointer to nfs_page
*
* The nfs_page structures 'prev' and 'req' are compared to ensure that the
* page data area they describe is contiguous, and that their RPC
* credentials, NFSv4 open state, and lockowners are the same.
*
* Return 'true' if this is the case, else return 'false'.
*/
static bool nfs_can_coalesce_requests(struct nfs_page *prev,
struct nfs_page *req,
struct nfs_pageio_descriptor *pgio)
{
if (req->wb_context->cred != prev->wb_context->cred)
return false;
if (req->wb_lock_context->lockowner != prev->wb_lock_context->lockowner)
return false;
if (req->wb_context->state != prev->wb_context->state)
return false;
if (req->wb_index != (prev->wb_index + 1))
return false;
if (req->wb_pgbase != 0)
return false;
if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
return false;
return pgio->pg_ops->pg_test(pgio, prev, req);
}
/**
* nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
* @desc: destination io descriptor
* @req: request
*
* Returns true if the request 'req' was successfully coalesced into the
* existing list of pages 'desc'.
*/
static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
struct nfs_page *req)
{
if (desc->pg_count != 0) {
struct nfs_page *prev;
prev = nfs_list_entry(desc->pg_list.prev);
if (!nfs_can_coalesce_requests(prev, req, desc))
return 0;
} else {
if (desc->pg_ops->pg_init)
desc->pg_ops->pg_init(desc, req);
desc->pg_base = req->wb_pgbase;
}
nfs_list_remove_request(req);
nfs_list_add_request(req, &desc->pg_list);
desc->pg_count += req->wb_bytes;
return 1;
}
/*
* Helper for nfs_pageio_add_request and nfs_pageio_complete
*/
static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
{
if (!list_empty(&desc->pg_list)) {
int error = desc->pg_ops->pg_doio(desc);
if (error < 0)
desc->pg_error = error;
else
desc->pg_bytes_written += desc->pg_count;
}
if (list_empty(&desc->pg_list)) {
desc->pg_count = 0;
desc->pg_base = 0;
}
}
/**
* nfs_pageio_add_request - Attempt to coalesce a request into a page list.
* @desc: destination io descriptor
* @req: request
*
* Returns true if the request 'req' was successfully coalesced into the
* existing list of pages 'desc'.
*/
static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
struct nfs_page *req)
{
while (!nfs_pageio_do_add_request(desc, req)) {
desc->pg_moreio = 1;
nfs_pageio_doio(desc);
if (desc->pg_error < 0)
return 0;
desc->pg_moreio = 0;
if (desc->pg_recoalesce)
return 0;
}
return 1;
}
static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
{
LIST_HEAD(head);
do {
list_splice_init(&desc->pg_list, &head);
desc->pg_bytes_written -= desc->pg_count;
desc->pg_count = 0;
desc->pg_base = 0;
desc->pg_recoalesce = 0;
while (!list_empty(&head)) {
struct nfs_page *req;
req = list_first_entry(&head, struct nfs_page, wb_list);
nfs_list_remove_request(req);
if (__nfs_pageio_add_request(desc, req))
continue;
if (desc->pg_error < 0)
return 0;
break;
}
} while (desc->pg_recoalesce);
return 1;
}
int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
struct nfs_page *req)
{
int ret;
do {
ret = __nfs_pageio_add_request(desc, req);
if (ret)
break;
if (desc->pg_error < 0)
break;
ret = nfs_do_recoalesce(desc);
} while (ret);
return ret;
}
/**
* nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
* @desc: pointer to io descriptor
*/
void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
{
for (;;) {
nfs_pageio_doio(desc);
if (!desc->pg_recoalesce)
break;
if (!nfs_do_recoalesce(desc))
break;
}
}
/**
* nfs_pageio_cond_complete - Conditional I/O completion
* @desc: pointer to io descriptor
* @index: page index
*
* It is important to ensure that processes don't try to take locks
* on non-contiguous ranges of pages as that might deadlock. This
* function should be called before attempting to wait on a locked
* nfs_page. It will complete the I/O if the page index 'index'
* is not contiguous with the existing list of pages in 'desc'.
*/
void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
{
if (!list_empty(&desc->pg_list)) {
struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
if (index != prev->wb_index + 1)
nfs_pageio_complete(desc);
}
}
int __init nfs_init_nfspagecache(void)
{
nfs_page_cachep = kmem_cache_create("nfs_page",
sizeof(struct nfs_page),
0, SLAB_HWCACHE_ALIGN,
NULL);
if (nfs_page_cachep == NULL)
return -ENOMEM;
return 0;
}
void nfs_destroy_nfspagecache(void)
{
kmem_cache_destroy(nfs_page_cachep);
}