/*
* 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/config.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs3.h>
#include <linux/nfs4.h>
#include <linux/nfs_page.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#define NFS_PARANOIA 1
static kmem_cache_t *nfs_page_cachep;
static inline struct nfs_page *
nfs_page_alloc(void)
{
struct nfs_page *p;
p = kmem_cache_alloc(nfs_page_cachep, SLAB_KERNEL);
if (p) {
memset(p, 0, sizeof(*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.
* @file: file descriptor 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, and avoids
* a possible deadlock when we reach the hard limit on the number
* of dirty pages.
* 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_server *server = NFS_SERVER(inode);
struct nfs_page *req;
/* Deal with hard limits. */
for (;;) {
/* try to allocate the request struct */
req = nfs_page_alloc();
if (req != NULL)
break;
/* Try to free up at least one request in order to stay
* below the hard limit
*/
if (signalled() && (server->flags & NFS_MOUNT_INTR))
return ERR_PTR(-ERESTARTSYS);
yield();
}
/* 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;
atomic_set(&req->wb_complete, 0);
req->wb_index = page->index;
page_cache_get(page);
req->wb_offset = offset;
req->wb_pgbase = offset;
req->wb_bytes = count;
atomic_set(&req->wb_count, 1);
req->wb_context = get_nfs_open_context(ctx);
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_all(&req->wb_context->waitq);
nfs_release_request(req);
}
/**
* nfs_clear_request - Free up all resources allocated to the request
* @req:
*
* Release page resources associated with a write request after it
* has completed.
*/
void nfs_clear_request(struct nfs_page *req)
{
if (req->wb_page) {
page_cache_release(req->wb_page);
req->wb_page = 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!
*/
void
nfs_release_request(struct nfs_page *req)
{
if (!atomic_dec_and_test(&req->wb_count))
return;
#ifdef NFS_PARANOIA
BUG_ON (!list_empty(&req->wb_list));
BUG_ON (NFS_WBACK_BUSY(req));
#endif
/* Release struct file or cached credential */
nfs_clear_request(req);
put_nfs_open_context(req->wb_context);
nfs_page_free(req);
}
/**
* nfs_list_add_request - Insert a request into a sorted list
* @req: request
* @head: head of list into which to insert the request.
*
* Note that the wb_list is sorted by page index in order to facilitate
* coalescing of requests.
* We use an insertion sort that is optimized for the case of appended
* writes.
*/
void
nfs_list_add_request(struct nfs_page *req, struct list_head *head)
{
struct list_head *pos;
#ifdef NFS_PARANOIA
if (!list_empty(&req->wb_list)) {
printk(KERN_ERR "NFS: Add to list failed!\n");
BUG();
}
#endif
list_for_each_prev(pos, head) {
struct nfs_page *p = nfs_list_entry(pos);
if (p->wb_index < req->wb_index)
break;
}
list_add(&req->wb_list, pos);
req->wb_list_head = head;
}
/**
* nfs_wait_on_request - Wait for a request to complete.
* @req: request to wait upon.
*
* Interruptible by signals only if mounted with intr flag.
* The user is responsible for holding a count on the request.
*/
int
nfs_wait_on_request(struct nfs_page *req)
{
struct inode *inode = req->wb_context->dentry->d_inode;
struct rpc_clnt *clnt = NFS_CLIENT(inode);
if (!NFS_WBACK_BUSY(req))
return 0;
return nfs_wait_event(clnt, req->wb_context->waitq, !NFS_WBACK_BUSY(req));
}
/**
* nfs_coalesce_requests - Split coalesced requests out from a list.
* @head: source list
* @dst: destination list
* @nmax: maximum number of requests to coalesce
*
* Moves a maximum of 'nmax' elements from one list to another.
* The elements are checked to ensure that they form a contiguous set
* of pages, and that the RPC credentials are the same.
*/
int
nfs_coalesce_requests(struct list_head *head, struct list_head *dst,
unsigned int nmax)
{
struct nfs_page *req = NULL;
unsigned int npages = 0;
while (!list_empty(head)) {
struct nfs_page *prev = req;
req = nfs_list_entry(head->next);
if (prev) {
if (req->wb_context->cred != prev->wb_context->cred)
break;
if (req->wb_context->lockowner != prev->wb_context->lockowner)
break;
if (req->wb_context->state != prev->wb_context->state)
break;
if (req->wb_index != (prev->wb_index + 1))
break;
if (req->wb_pgbase != 0)
break;
}
nfs_list_remove_request(req);
nfs_list_add_request(req, dst);
npages++;
if (req->wb_pgbase + req->wb_bytes != PAGE_CACHE_SIZE)
break;
if (npages >= nmax)
break;
}
return npages;
}
/**
* nfs_scan_list - Scan a list for matching requests
* @head: One of the NFS inode request lists
* @dst: Destination list
* @idx_start: lower bound of page->index to scan
* @npages: idx_start + npages sets the upper bound to scan.
*
* Moves elements from one of the inode request lists.
* If the number of requests is set to 0, the entire address_space
* starting at index idx_start, is scanned.
* The requests are *not* checked to ensure that they form a contiguous set.
* You must be holding the inode's req_lock when calling this function
*/
int
nfs_scan_list(struct list_head *head, struct list_head *dst,
unsigned long idx_start, unsigned int npages)
{
struct list_head *pos, *tmp;
struct nfs_page *req;
unsigned long idx_end;
int res;
res = 0;
if (npages == 0)
idx_end = ~0;
else
idx_end = idx_start + npages - 1;
list_for_each_safe(pos, tmp, head) {
req = nfs_list_entry(pos);
if (req->wb_index < idx_start)
continue;
if (req->wb_index > idx_end)
break;
if (!nfs_lock_request(req))
continue;
nfs_list_remove_request(req);
nfs_list_add_request(req, dst);
res++;
}
return res;
}
int nfs_init_nfspagecache(void)
{
nfs_page_cachep = kmem_cache_create("nfs_page",
sizeof(struct nfs_page),
0, SLAB_HWCACHE_ALIGN,
NULL, NULL);
if (nfs_page_cachep == NULL)
return -ENOMEM;
return 0;
}
void nfs_destroy_nfspagecache(void)
{
if (kmem_cache_destroy(nfs_page_cachep))
printk(KERN_INFO "nfs_page: not all structures were freed\n");
}
