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/*
* 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/nfs_page.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_flushd.h>
#include <linux/nfs_mount.h>
#define NFS_PARANOIA 1
/*
* Spinlock
*/
spinlock_t nfs_wreq_lock = SPIN_LOCK_UNLOCKED;
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_NOFS);
if (p) {
memset(p, 0, sizeof(*p));
INIT_LIST_HEAD(&p->wb_hash);
INIT_LIST_HEAD(&p->wb_list);
INIT_LIST_HEAD(&p->wb_lru);
init_waitqueue_head(&p->wb_wait);
}
return p;
}
static inline void
nfs_page_free(struct nfs_page *p)
{
kmem_cache_free(nfs_page_cachep, p);
}
static int nfs_try_to_free_pages(struct nfs_server *);
/**
* nfs_create_request - Create an NFS read/write request.
* @file: file that owns this request
* @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 file *file, struct inode *inode,
struct page *page,
unsigned int offset, unsigned int count)
{
struct nfs_server *server = NFS_SERVER(inode);
struct nfs_reqlist *cache = NFS_REQUESTLIST(inode);
struct nfs_page *req;
/* Deal with hard limits. */
for (;;) {
/* Prevent races by incrementing *before* we test */
atomic_inc(&cache->nr_requests);
/* If we haven't reached the local hard limit yet,
* try to allocate the request struct */
if (atomic_read(&cache->nr_requests) <= MAX_REQUEST_HARD) {
req = nfs_page_alloc();
if (req != NULL)
break;
}
atomic_dec(&cache->nr_requests);
/* Try to free up at least one request in order to stay
* below the hard limit
*/
if (nfs_try_to_free_pages(server))
continue;
if (signalled() && (server->flags & NFS_MOUNT_INTR))
return ERR_PTR(-ERESTARTSYS);
current->policy = SCHED_YIELD;
schedule();
}
/* 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;
page_cache_get(page);
req->wb_offset = offset;
req->wb_bytes = count;
/* If we have a struct file, use its cached credentials */
if (file) {
req->wb_file = file;
get_file(file);
req->wb_cred = nfs_file_cred(file);
}
req->wb_inode = inode;
req->wb_count = 1;
return req;
}
/**
* nfs_release_request - Release the count on an NFS read/write request
* @req: request to release
*
* Release all resources associated with a write request after it
* has been committed to stable storage
*
* Note: Should never be called with the spinlock held!
*/
void
nfs_release_request(struct nfs_page *req)
{
struct inode *inode = req->wb_inode;
struct nfs_reqlist *cache = NFS_REQUESTLIST(inode);
spin_lock(&nfs_wreq_lock);
if (--req->wb_count) {
spin_unlock(&nfs_wreq_lock);
return;
}
__nfs_del_lru(req);
spin_unlock(&nfs_wreq_lock);
atomic_dec(&cache->nr_requests);
#ifdef NFS_PARANOIA
if (!list_empty(&req->wb_list))
BUG();
if (!list_empty(&req->wb_hash))
BUG();
if (NFS_WBACK_BUSY(req))
BUG();
if (atomic_read(&cache->nr_requests) < 0)
BUG();
#endif
/* Release struct file or cached credential */
if (req->wb_file)
fput(req->wb_file);
else if (req->wb_cred)
put_rpccred(req->wb_cred);
page_cache_release(req->wb_page);
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;
unsigned long pg_idx = page_index(req->wb_page);
#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 (page_index(p->wb_page) < pg_idx)
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_inode;
struct rpc_clnt *clnt = NFS_CLIENT(inode);
if (!NFS_WBACK_BUSY(req))
return 0;
return nfs_wait_event(clnt, req->wb_wait, !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 they originated from the same file.
*/
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_file != prev->wb_file)
break;
if (page_index(req->wb_page) != page_index(prev->wb_page)+1)
break;
if (req->wb_offset != 0)
break;
}
nfs_list_remove_request(req);
nfs_list_add_request(req, dst);
npages++;
if (req->wb_offset + req->wb_bytes != PAGE_CACHE_SIZE)
break;
if (npages >= nmax)
break;
}
return npages;
}
/*
* nfs_scan_forward - Coalesce more requests
* @req: First request to add
* @dst: destination list
* @nmax: maximum number of requests to coalesce
*
* Tries to coalesce more requests by traversing the request's wb_list.
* Moves the resulting list into dst. Requests are guaranteed to be
* contiguous, and to originate from the same file.
*/
static int
nfs_scan_forward(struct nfs_page *req, struct list_head *dst, int nmax)
{
struct nfs_server *server = NFS_SERVER(req->wb_inode);
struct list_head *pos, *head = req->wb_list_head;
struct file *file = req->wb_file;
unsigned long idx = page_index(req->wb_page) + 1;
int npages = 0;
for (pos = req->wb_list.next; nfs_lock_request(req); pos = pos->next) {
nfs_list_remove_request(req);
nfs_list_add_request(req, dst);
__nfs_del_lru(req);
__nfs_add_lru(&server->lru_busy, req);
npages++;
if (npages == nmax)
break;
if (pos == head)
break;
if (req->wb_offset + req->wb_bytes != PAGE_CACHE_SIZE)
break;
req = nfs_list_entry(pos);
if (page_index(req->wb_page) != idx++)
break;
if (req->wb_offset != 0)
break;
if (req->wb_file != file)
break;
}
return npages;
}
/**
* nfs_scan_lru - Scan one of the least recently used list
* @head: One of the NFS superblock lru lists
* @dst: Destination list
* @nmax: maximum number of requests to coalesce
*
* Scans one of the NFS superblock lru lists for upto nmax requests
* and returns them on a list. The requests are all guaranteed to be
* contiguous, originating from the same inode and the same file.
*/
int
nfs_scan_lru(struct list_head *head, struct list_head *dst, int nmax)
{
struct list_head *pos;
struct nfs_page *req;
int npages = 0;
list_for_each(pos, head) {
req = nfs_lru_entry(pos);
npages = nfs_scan_forward(req, dst, nmax);
if (npages)
break;
}
return npages;
}
/**
* nfs_scan_lru_timeout - Scan one of the superblock lru lists for timed out requests
* @head: One of the NFS superblock lru lists
* @dst: Destination list
* @nmax: maximum number of requests to coalesce
*
* Scans one of the NFS superblock lru lists for upto nmax requests
* and returns them on a list. The requests are all guaranteed to be
* contiguous, originating from the same inode and the same file.
* The first request on the destination list will be timed out, the
* others are not guaranteed to be so.
*/
int
nfs_scan_lru_timeout(struct list_head *head, struct list_head *dst, int nmax)
{
struct list_head *pos;
struct nfs_page *req;
int npages = 0;
list_for_each(pos, head) {
req = nfs_lru_entry(pos);
if (time_after(req->wb_timeout, jiffies))
break;
npages = nfs_scan_forward(req, dst, nmax);
if (npages)
break;
}
return npages;
}
/**
* nfs_scan_list - Scan a list for matching requests
* @head: One of the NFS inode request lists
* @dst: Destination list
* @file: if set, ensure we match requests from this file
* @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 nfs_wreq_lock when calling this function
*/
int
nfs_scan_list(struct list_head *head, struct list_head *dst,
struct file *file,
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) {
unsigned long pg_idx;
req = nfs_list_entry(pos);
if (file && req->wb_file != file)
continue;
pg_idx = page_index(req->wb_page);
if (pg_idx < idx_start)
continue;
if (pg_idx > idx_end)
break;
if (!nfs_lock_request(req))
continue;
nfs_list_remove_request(req);
nfs_list_add_request(req, dst);
__nfs_del_lru(req);
__nfs_add_lru(&NFS_SERVER(req->wb_inode)->lru_busy, req);
res++;
}
return res;
}
/*
* nfs_try_to_free_pages - Free up NFS read/write requests
* @server: The NFS superblock
*
* This function attempts to flush out NFS reads and writes in order
* to keep the hard limit on the total number of pending requests
* on a given NFS partition.
* Note: we first try to commit unstable writes, then flush out pending
* reads, then finally the dirty pages.
* The assumption is that this reflects the ordering from the fastest
* to the slowest method for reclaiming requests.
*/
static int
nfs_try_to_free_pages(struct nfs_server *server)
{
LIST_HEAD(head);
struct nfs_page *req = NULL;
int nreq;
for (;;) {
if (req) {
int status = nfs_wait_on_request(req);
nfs_release_request(req);
if (status)
break;
req = NULL;
}
nreq = atomic_read(&server->rw_requests->nr_requests);
if (nreq < MAX_REQUEST_HARD)
return 1;
spin_lock(&nfs_wreq_lock);
/* Are there any busy RPC calls that might free up requests? */
if (!list_empty(&server->lru_busy)) {
req = nfs_lru_entry(server->lru_busy.next);
req->wb_count++;
__nfs_del_lru(req);
spin_unlock(&nfs_wreq_lock);
continue;
}
#ifdef CONFIG_NFS_V3
/* Let's try to free up some completed NFSv3 unstable writes */
nfs_scan_lru_commit(server, &head);
if (!list_empty(&head)) {
spin_unlock(&nfs_wreq_lock);
nfs_commit_list(&head, 0);
continue;
}
#endif
/* OK, so we try to free up some pending readaheads */
nfs_scan_lru_read(server, &head);
if (!list_empty(&head)) {
spin_unlock(&nfs_wreq_lock);
nfs_pagein_list(&head, server->rpages);
continue;
}
/* Last resort: we try to flush out single requests */
nfs_scan_lru_dirty(server, &head);
if (!list_empty(&head)) {
spin_unlock(&nfs_wreq_lock);
nfs_flush_list(&head, server->wpages, FLUSH_STABLE);
continue;
}
spin_unlock(&nfs_wreq_lock);
break;
}
/* We failed to free up requests */
return 0;
}
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");
}
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