| /* |
| * 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. |
| * @cred: RPC credential 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 rpc_cred *cred, 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); |
| 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; |
| page_cache_get(page); |
| req->wb_offset = offset; |
| req->wb_bytes = count; |
| |
| if (cred) |
| req->wb_cred = get_rpccred(cred); |
| req->wb_inode = inode; |
| req->wb_count = 1; |
| |
| return req; |
| } |
| |
| /** |
| * nfs_clear_request - Free up all resources allocated to the request |
| * @req: |
| * |
| * Release all resources associated with a write request after it |
| * has completed. |
| */ |
| void nfs_clear_request(struct nfs_page *req) |
| { |
| /* Release struct file or cached credential */ |
| if (req->wb_file) { |
| fput(req->wb_file); |
| req->wb_file = NULL; |
| } |
| if (req->wb_cred) { |
| put_rpccred(req->wb_cred); |
| req->wb_cred = NULL; |
| } |
| if (req->wb_page) { |
| atomic_dec(&NFS_REQUESTLIST(req->wb_inode)->nr_requests); |
| #ifdef NFS_PARANOIA |
| BUG_ON(atomic_read(&NFS_REQUESTLIST(req->wb_inode)->nr_requests) < 0); |
| #endif |
| 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) |
| { |
| spin_lock(&nfs_wreq_lock); |
| if (--req->wb_count) { |
| spin_unlock(&nfs_wreq_lock); |
| return; |
| } |
| __nfs_del_lru(req); |
| spin_unlock(&nfs_wreq_lock); |
| |
| #ifdef NFS_PARANOIA |
| BUG_ON(!list_empty(&req->wb_list)); |
| BUG_ON(!list_empty(&req->wb_hash)); |
| BUG_ON(NFS_WBACK_BUSY(req)); |
| #endif |
| |
| /* Release struct file or cached credential */ |
| nfs_clear_request(req); |
| 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_cred != prev->wb_cred) |
| 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 rpc_cred *cred = req->wb_cred; |
| 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_cred != cred) |
| 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 |
| * @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, |
| 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); |
| |
| 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"); |
| } |
| |