patch-2.4.15 linux/fs/nfs/pagelist.c

• Lines: 499
• Date: Fri Nov 9 14:28:15 2001
• Orig file: v2.4.14/linux/fs/nfs/pagelist.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.14/linux/fs/nfs/pagelist.c linux/fs/nfs/pagelist.c
@@ -0,0 +1,498 @@
+/*
+ * 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
+	for (pos = head->prev; pos != head; pos = pos->prev) {
+		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");
+}
+