/* * 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/slab.h> #include <linux/file.h> #include <linux/sched.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> #include "internal.h" static struct kmem_cache *nfs_page_cachep; static inline struct nfs_page * nfs_page_alloc(void) { struct nfs_page *p; p = kmem_cache_alloc(nfs_page_cachep, GFP_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. * 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_page *req; for (;;) { /* try to allocate the request struct */ req = nfs_page_alloc(); if (req != NULL) break; if (fatal_signal_pending(current)) 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); BUG_ON(PagePrivate(page)); BUG_ON(!PageLocked(page)); BUG_ON(page->mapping->host != inode); req->wb_offset = offset; req->wb_pgbase = offset; req->wb_bytes = count; req->wb_context = get_nfs_open_context(ctx); kref_init(&req->wb_kref); 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_bit(&req->wb_flags, PG_BUSY); nfs_release_request(req); } /** * nfs_set_page_tag_locked - Tag a request as locked * @req: */ int nfs_set_page_tag_locked(struct nfs_page *req) { struct nfs_inode *nfsi = NFS_I(req->wb_context->path.dentry->d_inode); if (!nfs_lock_request_dontget(req)) return 0; if (req->wb_page != NULL) radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED); return 1; } /** * nfs_clear_page_tag_locked - Clear request tag and wake up sleepers */ void nfs_clear_page_tag_locked(struct nfs_page *req) { struct inode *inode = req->wb_context->path.dentry->d_inode; struct nfs_inode *nfsi = NFS_I(inode); if (req->wb_page != NULL) { spin_lock(&inode->i_lock); radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED); nfs_unlock_request(req); spin_unlock(&inode->i_lock); } else nfs_unlock_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) { struct page *page = req->wb_page; if (page != NULL) { page_cache_release(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! */ static void nfs_free_request(struct kref *kref) { struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref); /* Release struct file or cached credential */ nfs_clear_request(req); put_nfs_open_context(req->wb_context); nfs_page_free(req); } void nfs_release_request(struct nfs_page *req) { kref_put(&req->wb_kref, nfs_free_request); } static int nfs_wait_bit_killable(void *word) { int ret = 0; if (fatal_signal_pending(current)) ret = -ERESTARTSYS; else schedule(); return ret; } /** * nfs_wait_on_request - Wait for a request to complete. * @req: request to wait upon. * * Interruptible by fatal signals only. * The user is responsible for holding a count on the request. */ int nfs_wait_on_request(struct nfs_page *req) { int ret = 0; if (!test_bit(PG_BUSY, &req->wb_flags)) goto out; ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY, nfs_wait_bit_killable, TASK_KILLABLE); out: return ret; } /** * nfs_pageio_init - initialise a page io descriptor * @desc: pointer to descriptor * @inode: pointer to inode * @doio: pointer to io function * @bsize: io block size * @io_flags: extra parameters for the io function */ void nfs_pageio_init(struct nfs_pageio_descriptor *desc, struct inode *inode, int (*doio)(struct inode *, struct list_head *, unsigned int, size_t, int), size_t bsize, int io_flags) { INIT_LIST_HEAD(&desc->pg_list); desc->pg_bytes_written = 0; desc->pg_count = 0; desc->pg_bsize = bsize; desc->pg_base = 0; desc->pg_inode = inode; desc->pg_doio = doio; desc->pg_ioflags = io_flags; desc->pg_error = 0; } /** * nfs_can_coalesce_requests - test two requests for compatibility * @prev: pointer to nfs_page * @req: pointer to nfs_page * * The nfs_page structures 'prev' and 'req' are compared to ensure that the * page data area they describe is contiguous, and that their RPC * credentials, NFSv4 open state, and lockowners are the same. * * Return 'true' if this is the case, else return 'false'. */ static int nfs_can_coalesce_requests(struct nfs_page *prev, struct nfs_page *req) { if (req->wb_context->cred != prev->wb_context->cred) return 0; if (req->wb_context->lockowner != prev->wb_context->lockowner) return 0; if (req->wb_context->state != prev->wb_context->state) return 0; if (req->wb_index != (prev->wb_index + 1)) return 0; if (req->wb_pgbase != 0) return 0; if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE) return 0; return 1; } /** * nfs_pageio_do_add_request - Attempt to coalesce a request into a page list. * @desc: destination io descriptor * @req: request * * Returns true if the request 'req' was successfully coalesced into the * existing list of pages 'desc'. */ static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc, struct nfs_page *req) { size_t newlen = req->wb_bytes; if (desc->pg_count != 0) { struct nfs_page *prev; /* * FIXME: ideally we should be able to coalesce all requests * that are not block boundary aligned, but currently this * is problematic for the case of bsize < PAGE_CACHE_SIZE, * since nfs_flush_multi and nfs_pagein_multi assume you * can have only one struct nfs_page. */ if (desc->pg_bsize < PAGE_SIZE) return 0; newlen += desc->pg_count; if (newlen > desc->pg_bsize) return 0; prev = nfs_list_entry(desc->pg_list.prev); if (!nfs_can_coalesce_requests(prev, req)) return 0; } else desc->pg_base = req->wb_pgbase; nfs_list_remove_request(req); nfs_list_add_request(req, &desc->pg_list); desc->pg_count = newlen; return 1; } /* * Helper for nfs_pageio_add_request and nfs_pageio_complete */ static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc) { if (!list_empty(&desc->pg_list)) { int error = desc->pg_doio(desc->pg_inode, &desc->pg_list, nfs_page_array_len(desc->pg_base, desc->pg_count), desc->pg_count, desc->pg_ioflags); if (error < 0) desc->pg_error = error; else desc->pg_bytes_written += desc->pg_count; } if (list_empty(&desc->pg_list)) { desc->pg_count = 0; desc->pg_base = 0; } } /** * nfs_pageio_add_request - Attempt to coalesce a request into a page list. * @desc: destination io descriptor * @req: request * * Returns true if the request 'req' was successfully coalesced into the * existing list of pages 'desc'. */ int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc, struct nfs_page *req) { while (!nfs_pageio_do_add_request(desc, req)) { nfs_pageio_doio(desc); if (desc->pg_error < 0) return 0; } return 1; } /** * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor * @desc: pointer to io descriptor */ void nfs_pageio_complete(struct nfs_pageio_descriptor *desc) { nfs_pageio_doio(desc); } /** * nfs_pageio_cond_complete - Conditional I/O completion * @desc: pointer to io descriptor * @index: page index * * It is important to ensure that processes don't try to take locks * on non-contiguous ranges of pages as that might deadlock. This * function should be called before attempting to wait on a locked * nfs_page. It will complete the I/O if the page index 'index' * is not contiguous with the existing list of pages in 'desc'. */ void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index) { if (!list_empty(&desc->pg_list)) { struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev); if (index != prev->wb_index + 1) nfs_pageio_doio(desc); } } #define NFS_SCAN_MAXENTRIES 16 /** * nfs_scan_list - Scan a list for matching requests * @nfsi: NFS inode * @dst: Destination list * @idx_start: lower bound of page->index to scan * @npages: idx_start + npages sets the upper bound to scan. * @tag: tag to scan for * * 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 i_lock when calling this function */ int nfs_scan_list(struct nfs_inode *nfsi, struct list_head *dst, pgoff_t idx_start, unsigned int npages, int tag) { struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES]; struct nfs_page *req; pgoff_t idx_end; int found, i; int res; res = 0; if (npages == 0) idx_end = ~0; else idx_end = idx_start + npages - 1; for (;;) { found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree, (void **)&pgvec[0], idx_start, NFS_SCAN_MAXENTRIES, tag); if (found <= 0) break; for (i = 0; i < found; i++) { req = pgvec[i]; if (req->wb_index > idx_end) goto out; idx_start = req->wb_index + 1; if (nfs_set_page_tag_locked(req)) { kref_get(&req->wb_kref); nfs_list_remove_request(req); radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, tag); nfs_list_add_request(req, dst); res++; if (res == INT_MAX) goto out; } } /* for latency reduction */ cond_resched_lock(&nfsi->vfs_inode.i_lock); } out: return res; } int __init nfs_init_nfspagecache(void) { nfs_page_cachep = kmem_cache_create("nfs_page", sizeof(struct nfs_page), 0, SLAB_HWCACHE_ALIGN, NULL); if (nfs_page_cachep == NULL) return -ENOMEM; return 0; } void nfs_destroy_nfspagecache(void) { kmem_cache_destroy(nfs_page_cachep); }