![Trond Myklebust](/assets/img/avatar_default.png)
Ensure that we always get a layout before setting up the i/o request. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
454 lines
12 KiB
C
454 lines
12 KiB
C
/*
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* linux/fs/nfs/pagelist.c
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*
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* A set of helper functions for managing NFS read and write requests.
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* The main purpose of these routines is to provide support for the
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* coalescing of several requests into a single RPC call.
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*
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* Copyright 2000, 2001 (c) Trond Myklebust <trond.myklebust@fys.uio.no>
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*
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*/
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/sched.h>
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#include <linux/sunrpc/clnt.h>
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#include <linux/nfs3.h>
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#include <linux/nfs4.h>
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#include <linux/nfs_page.h>
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#include <linux/nfs_fs.h>
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#include <linux/nfs_mount.h>
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#include "internal.h"
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#include "pnfs.h"
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static struct kmem_cache *nfs_page_cachep;
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static inline struct nfs_page *
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nfs_page_alloc(void)
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{
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struct nfs_page *p = kmem_cache_zalloc(nfs_page_cachep, GFP_KERNEL);
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if (p)
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INIT_LIST_HEAD(&p->wb_list);
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return p;
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}
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static inline void
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nfs_page_free(struct nfs_page *p)
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{
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kmem_cache_free(nfs_page_cachep, p);
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}
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/**
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* nfs_create_request - Create an NFS read/write request.
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* @file: file descriptor to use
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* @inode: inode to which the request is attached
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* @page: page to write
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* @offset: starting offset within the page for the write
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* @count: number of bytes to read/write
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*
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* The page must be locked by the caller. This makes sure we never
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* create two different requests for the same page.
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* User should ensure it is safe to sleep in this function.
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*/
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struct nfs_page *
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nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
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struct page *page,
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unsigned int offset, unsigned int count)
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{
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struct nfs_page *req;
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/* try to allocate the request struct */
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req = nfs_page_alloc();
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if (req == NULL)
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return ERR_PTR(-ENOMEM);
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/* get lock context early so we can deal with alloc failures */
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req->wb_lock_context = nfs_get_lock_context(ctx);
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if (req->wb_lock_context == NULL) {
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nfs_page_free(req);
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return ERR_PTR(-ENOMEM);
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}
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/* Initialize the request struct. Initially, we assume a
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* long write-back delay. This will be adjusted in
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* update_nfs_request below if the region is not locked. */
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req->wb_page = page;
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atomic_set(&req->wb_complete, 0);
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req->wb_index = page->index;
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page_cache_get(page);
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BUG_ON(PagePrivate(page));
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BUG_ON(!PageLocked(page));
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BUG_ON(page->mapping->host != inode);
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req->wb_offset = offset;
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req->wb_pgbase = offset;
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req->wb_bytes = count;
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req->wb_context = get_nfs_open_context(ctx);
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kref_init(&req->wb_kref);
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return req;
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}
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/**
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* nfs_unlock_request - Unlock request and wake up sleepers.
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* @req:
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*/
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void nfs_unlock_request(struct nfs_page *req)
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{
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if (!NFS_WBACK_BUSY(req)) {
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printk(KERN_ERR "NFS: Invalid unlock attempted\n");
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BUG();
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}
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smp_mb__before_clear_bit();
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clear_bit(PG_BUSY, &req->wb_flags);
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smp_mb__after_clear_bit();
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wake_up_bit(&req->wb_flags, PG_BUSY);
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nfs_release_request(req);
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}
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/**
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* nfs_set_page_tag_locked - Tag a request as locked
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* @req:
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*/
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int nfs_set_page_tag_locked(struct nfs_page *req)
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{
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if (!nfs_lock_request_dontget(req))
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return 0;
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if (test_bit(PG_MAPPED, &req->wb_flags))
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radix_tree_tag_set(&NFS_I(req->wb_context->path.dentry->d_inode)->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
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return 1;
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}
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/**
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* nfs_clear_page_tag_locked - Clear request tag and wake up sleepers
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*/
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void nfs_clear_page_tag_locked(struct nfs_page *req)
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{
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if (test_bit(PG_MAPPED, &req->wb_flags)) {
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struct inode *inode = req->wb_context->path.dentry->d_inode;
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struct nfs_inode *nfsi = NFS_I(inode);
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spin_lock(&inode->i_lock);
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radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
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nfs_unlock_request(req);
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spin_unlock(&inode->i_lock);
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} else
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nfs_unlock_request(req);
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}
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/*
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* nfs_clear_request - Free up all resources allocated to the request
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* @req:
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*
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* Release page and open context resources associated with a read/write
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* request after it has completed.
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*/
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static void nfs_clear_request(struct nfs_page *req)
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{
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struct page *page = req->wb_page;
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struct nfs_open_context *ctx = req->wb_context;
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struct nfs_lock_context *l_ctx = req->wb_lock_context;
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if (page != NULL) {
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page_cache_release(page);
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req->wb_page = NULL;
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}
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if (l_ctx != NULL) {
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nfs_put_lock_context(l_ctx);
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req->wb_lock_context = NULL;
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}
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if (ctx != NULL) {
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put_nfs_open_context(ctx);
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req->wb_context = NULL;
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}
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}
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/**
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* nfs_release_request - Release the count on an NFS read/write request
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* @req: request to release
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*
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* Note: Should never be called with the spinlock held!
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*/
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static void nfs_free_request(struct kref *kref)
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{
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struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
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/* Release struct file and open context */
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nfs_clear_request(req);
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nfs_page_free(req);
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}
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void nfs_release_request(struct nfs_page *req)
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{
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kref_put(&req->wb_kref, nfs_free_request);
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}
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static int nfs_wait_bit_uninterruptible(void *word)
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{
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io_schedule();
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return 0;
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}
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/**
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* nfs_wait_on_request - Wait for a request to complete.
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* @req: request to wait upon.
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*
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* Interruptible by fatal signals only.
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* The user is responsible for holding a count on the request.
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*/
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int
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nfs_wait_on_request(struct nfs_page *req)
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{
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return wait_on_bit(&req->wb_flags, PG_BUSY,
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nfs_wait_bit_uninterruptible,
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TASK_UNINTERRUPTIBLE);
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}
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bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *prev, struct nfs_page *req)
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{
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/*
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* FIXME: ideally we should be able to coalesce all requests
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* that are not block boundary aligned, but currently this
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* is problematic for the case of bsize < PAGE_CACHE_SIZE,
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* since nfs_flush_multi and nfs_pagein_multi assume you
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* can have only one struct nfs_page.
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*/
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if (desc->pg_bsize < PAGE_SIZE)
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return 0;
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return desc->pg_count + req->wb_bytes <= desc->pg_bsize;
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}
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EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
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/**
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* nfs_pageio_init - initialise a page io descriptor
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* @desc: pointer to descriptor
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* @inode: pointer to inode
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* @doio: pointer to io function
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* @bsize: io block size
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* @io_flags: extra parameters for the io function
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*/
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void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
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struct inode *inode,
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const struct nfs_pageio_ops *pg_ops,
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size_t bsize,
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int io_flags)
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{
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INIT_LIST_HEAD(&desc->pg_list);
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desc->pg_bytes_written = 0;
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desc->pg_count = 0;
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desc->pg_bsize = bsize;
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desc->pg_base = 0;
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desc->pg_moreio = 0;
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desc->pg_inode = inode;
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desc->pg_ops = pg_ops;
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desc->pg_ioflags = io_flags;
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desc->pg_error = 0;
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desc->pg_lseg = NULL;
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}
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/**
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* nfs_can_coalesce_requests - test two requests for compatibility
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* @prev: pointer to nfs_page
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* @req: pointer to nfs_page
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*
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* The nfs_page structures 'prev' and 'req' are compared to ensure that the
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* page data area they describe is contiguous, and that their RPC
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* credentials, NFSv4 open state, and lockowners are the same.
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*
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* Return 'true' if this is the case, else return 'false'.
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*/
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static bool nfs_can_coalesce_requests(struct nfs_page *prev,
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struct nfs_page *req,
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struct nfs_pageio_descriptor *pgio)
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{
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if (req->wb_context->cred != prev->wb_context->cred)
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return false;
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if (req->wb_lock_context->lockowner != prev->wb_lock_context->lockowner)
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return false;
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if (req->wb_context->state != prev->wb_context->state)
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return false;
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if (req->wb_index != (prev->wb_index + 1))
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return false;
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if (req->wb_pgbase != 0)
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return false;
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if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
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return false;
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return pgio->pg_ops->pg_test(pgio, prev, req);
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}
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/**
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* nfs_pageio_do_add_request - Attempt to coalesce a request into a page list.
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* @desc: destination io descriptor
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* @req: request
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*
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* Returns true if the request 'req' was successfully coalesced into the
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* existing list of pages 'desc'.
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*/
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static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
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struct nfs_page *req)
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{
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if (desc->pg_count != 0) {
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struct nfs_page *prev;
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prev = nfs_list_entry(desc->pg_list.prev);
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if (!nfs_can_coalesce_requests(prev, req, desc))
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return 0;
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} else {
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if (desc->pg_ops->pg_init)
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desc->pg_ops->pg_init(desc, req);
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desc->pg_base = req->wb_pgbase;
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}
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nfs_list_remove_request(req);
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nfs_list_add_request(req, &desc->pg_list);
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desc->pg_count += req->wb_bytes;
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return 1;
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}
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/*
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* Helper for nfs_pageio_add_request and nfs_pageio_complete
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*/
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static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
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{
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if (!list_empty(&desc->pg_list)) {
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int error = desc->pg_ops->pg_doio(desc);
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if (error < 0)
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desc->pg_error = error;
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else
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desc->pg_bytes_written += desc->pg_count;
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}
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if (list_empty(&desc->pg_list)) {
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desc->pg_count = 0;
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desc->pg_base = 0;
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}
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}
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/**
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* nfs_pageio_add_request - Attempt to coalesce a request into a page list.
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* @desc: destination io descriptor
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* @req: request
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*
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* Returns true if the request 'req' was successfully coalesced into the
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* existing list of pages 'desc'.
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*/
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int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
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struct nfs_page *req)
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{
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while (!nfs_pageio_do_add_request(desc, req)) {
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desc->pg_moreio = 1;
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nfs_pageio_doio(desc);
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if (desc->pg_error < 0)
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return 0;
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desc->pg_moreio = 0;
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}
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return 1;
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}
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/**
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* nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
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* @desc: pointer to io descriptor
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*/
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void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
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{
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nfs_pageio_doio(desc);
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}
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/**
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* nfs_pageio_cond_complete - Conditional I/O completion
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* @desc: pointer to io descriptor
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* @index: page index
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*
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* It is important to ensure that processes don't try to take locks
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* on non-contiguous ranges of pages as that might deadlock. This
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* function should be called before attempting to wait on a locked
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* nfs_page. It will complete the I/O if the page index 'index'
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* is not contiguous with the existing list of pages in 'desc'.
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*/
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void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
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{
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if (!list_empty(&desc->pg_list)) {
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struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
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if (index != prev->wb_index + 1)
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nfs_pageio_doio(desc);
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}
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}
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#define NFS_SCAN_MAXENTRIES 16
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/**
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* nfs_scan_list - Scan a list for matching requests
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* @nfsi: NFS inode
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* @dst: Destination list
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* @idx_start: lower bound of page->index to scan
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* @npages: idx_start + npages sets the upper bound to scan.
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* @tag: tag to scan for
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*
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* Moves elements from one of the inode request lists.
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* If the number of requests is set to 0, the entire address_space
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* starting at index idx_start, is scanned.
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* The requests are *not* checked to ensure that they form a contiguous set.
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* You must be holding the inode's i_lock when calling this function
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*/
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int nfs_scan_list(struct nfs_inode *nfsi,
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struct list_head *dst, pgoff_t idx_start,
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unsigned int npages, int tag)
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{
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struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
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struct nfs_page *req;
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pgoff_t idx_end;
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int found, i;
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int res;
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struct list_head *list;
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res = 0;
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if (npages == 0)
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idx_end = ~0;
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else
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idx_end = idx_start + npages - 1;
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for (;;) {
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found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
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(void **)&pgvec[0], idx_start,
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NFS_SCAN_MAXENTRIES, tag);
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if (found <= 0)
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break;
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for (i = 0; i < found; i++) {
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req = pgvec[i];
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if (req->wb_index > idx_end)
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goto out;
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idx_start = req->wb_index + 1;
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if (nfs_set_page_tag_locked(req)) {
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kref_get(&req->wb_kref);
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radix_tree_tag_clear(&nfsi->nfs_page_tree,
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req->wb_index, tag);
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list = pnfs_choose_commit_list(req, dst);
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nfs_list_add_request(req, list);
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res++;
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if (res == INT_MAX)
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goto out;
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}
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}
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/* for latency reduction */
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cond_resched_lock(&nfsi->vfs_inode.i_lock);
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}
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out:
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return res;
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}
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int __init nfs_init_nfspagecache(void)
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{
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nfs_page_cachep = kmem_cache_create("nfs_page",
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sizeof(struct nfs_page),
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0, SLAB_HWCACHE_ALIGN,
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NULL);
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if (nfs_page_cachep == NULL)
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return -ENOMEM;
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return 0;
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}
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void nfs_destroy_nfspagecache(void)
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{
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kmem_cache_destroy(nfs_page_cachep);
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}
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