/* * 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"); }