Fix prototype of SMP version of synchronize_irq.

[linux-2.6/linux-mips.git] / fs / nfs / write.c

/*
 * linux/fs/nfs/write.c
 *
 * Writing file data over NFS.
 *
 * We do it like this: When a (user) process wishes to write data to an
 * NFS file, a write request is allocated that contains the RPC task data
 * plus some info on the page to be written, and added to the inode's
 * write chain. If the process writes past the end of the page, an async
 * RPC call to write the page is scheduled immediately; otherwise, the call
 * is delayed for a few seconds.
 *
 * Just like readahead, no async I/O is performed if wsize < PAGE_SIZE.
 *
 * Write requests are kept on the inode's writeback list. Each entry in
 * that list references the page (portion) to be written. When the
 * cache timeout has expired, the RPC task is woken up, and tries to
 * lock the page. As soon as it manages to do so, the request is moved
 * from the writeback list to the writelock list.
 *
 * Note: we must make sure never to confuse the inode passed in the
 * write_page request with the one in page->inode. As far as I understand
 * it, these are different when doing a swap-out.
 *
 * To understand everything that goes on here and in the NFS read code,
 * one should be aware that a page is locked in exactly one of the following
 * cases:
 *
 *  -   A write request is in progress.
 *  -   A user process is in generic_file_write/nfs_update_page
 *  -   A user process is in generic_file_read
 *
 * Also note that because of the way pages are invalidated in
 * nfs_revalidate_inode, the following assertions hold:
 *
 *  -   If a page is dirty, there will be no read requests (a page will
 *      not be re-read unless invalidated by nfs_revalidate_inode).
 *  -   If the page is not uptodate, there will be no pending write
 *      requests, and no process will be in nfs_update_page.
 *
 * FIXME: Interaction with the vmscan routines is not optimal yet.
 * Either vmscan must be made nfs-savvy, or we need a different page
 * reclaim concept that supports something like FS-independent
 * buffer_heads with a b_ops-> field.
 *
 * Copyright (C) 1996, 1997, Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/config.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/mpage.h>
#include <linux/writeback.h>

#include <linux/sunrpc/clnt.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/nfs_page.h>
#include <asm/uaccess.h>
#include <linux/smp_lock.h>
#include <linux/mempool.h>

#define NFSDBG_FACILITY         NFSDBG_PAGECACHE

#define MIN_POOL_WRITE          (32)
#define MIN_POOL_COMMIT         (4)

/*
 * Local function declarations
 */
static struct nfs_page * nfs_update_request(struct file*, struct inode *,
                                            struct page *,
                                            unsigned int, unsigned int);
static void     nfs_strategy(struct inode *inode);

static kmem_cache_t *nfs_wdata_cachep;
static mempool_t *nfs_wdata_mempool;
static mempool_t *nfs_commit_mempool;

static __inline__ struct nfs_write_data *nfs_writedata_alloc(void)
{
        struct nfs_write_data   *p;
        p = (struct nfs_write_data *)mempool_alloc(nfs_wdata_mempool, SLAB_NOFS);
        if (p) {
                memset(p, 0, sizeof(*p));
                INIT_LIST_HEAD(&p->pages);
        }
        return p;
}

static __inline__ void nfs_writedata_free(struct nfs_write_data *p)
{
        mempool_free(p, nfs_wdata_mempool);
}

void nfs_writedata_release(struct rpc_task *task)
{
        struct nfs_write_data   *wdata = (struct nfs_write_data *)task->tk_calldata;
        nfs_writedata_free(wdata);
}

static __inline__ struct nfs_write_data *nfs_commit_alloc(void)
{
        struct nfs_write_data   *p;
        p = (struct nfs_write_data *)mempool_alloc(nfs_commit_mempool, SLAB_NOFS);
        if (p) {
                memset(p, 0, sizeof(*p));
                INIT_LIST_HEAD(&p->pages);
        }
        return p;
}

static __inline__ void nfs_commit_free(struct nfs_write_data *p)
{
        mempool_free(p, nfs_commit_mempool);
}

void nfs_commit_release(struct rpc_task *task)
{
        struct nfs_write_data   *wdata = (struct nfs_write_data *)task->tk_calldata;
        nfs_commit_free(wdata);
}

/*
 * Write a page synchronously.
 * Offset is the data offset within the page.
 */
static int
nfs_writepage_sync(struct file *file, struct inode *inode, struct page *page,
                   unsigned int offset, unsigned int count)
{
        struct rpc_cred *cred = NULL;
        loff_t          base;
        unsigned int    wsize = NFS_SERVER(inode)->wsize;
        int             result, refresh = 0, written = 0, flags;
        u8              *buffer;
        struct nfs_fattr fattr;
        struct nfs_writeverf verf;


        if (file)
                cred = get_rpccred(nfs_file_cred(file));
        if (!cred)
                cred = get_rpccred(NFS_I(inode)->mm_cred);

        dprintk("NFS:      nfs_writepage_sync(%s/%Ld %d@%Ld)\n",
                inode->i_sb->s_id,
                (long long)NFS_FILEID(inode),
                count, (long long)(page_offset(page) + offset));

        base = page_offset(page) + offset;

        flags = ((IS_SWAPFILE(inode)) ? NFS_RW_SWAP : 0) | NFS_RW_SYNC;

        do {
                if (count < wsize && !IS_SWAPFILE(inode))
                        wsize = count;

                result = NFS_PROTO(inode)->write(inode, cred, &fattr, flags,
                                                 offset, wsize, page, &verf);

                if (result < 0) {
                        /* Must mark the page invalid after I/O error */
                        ClearPageUptodate(page);
                        goto io_error;
                }
                if (result != wsize)
                        printk("NFS: short write, wsize=%u, result=%d\n",
                        wsize, result);
                refresh = 1;
                buffer  += wsize;
                base    += wsize;
                offset  += wsize;
                written += wsize;
                count   -= wsize;
                /*
                 * If we've extended the file, update the inode
                 * now so we don't invalidate the cache.
                 */
                if (base > inode->i_size)
                        inode->i_size = base;
        } while (count);

        if (PageError(page))
                ClearPageError(page);

io_error:
        if (cred)
                put_rpccred(cred);

        return written? written : result;
}

static int
nfs_writepage_async(struct file *file, struct inode *inode, struct page *page,
                    unsigned int offset, unsigned int count)
{
        struct nfs_page *req;
        loff_t          end;
        int             status;

        req = nfs_update_request(file, inode, page, offset, count);
        status = (IS_ERR(req)) ? PTR_ERR(req) : 0;
        if (status < 0)
                goto out;
        if (!req->wb_cred)
                req->wb_cred = get_rpccred(NFS_I(inode)->mm_cred);
        nfs_unlock_request(req);
        nfs_strategy(inode);
        end = ((loff_t)page->index<<PAGE_CACHE_SHIFT) + (loff_t)(offset + count);
        if (inode->i_size < end)
                inode->i_size = end;

 out:
        return status;
}

/*
 * Write an mmapped page to the server.
 */
int
nfs_writepage(struct page *page, struct writeback_control *wbc)
{
        struct inode *inode = page->mapping->host;
        unsigned long end_index;
        unsigned offset = PAGE_CACHE_SIZE;
        int err;

        end_index = inode->i_size >> PAGE_CACHE_SHIFT;

        /* Ensure we've flushed out any previous writes */
        nfs_wb_page(inode,page);

        /* easy case */
        if (page->index < end_index)
                goto do_it;
        /* things got complicated... */
        offset = inode->i_size & (PAGE_CACHE_SIZE-1);

        /* OK, are we completely out? */
        err = -EIO;
        if (page->index >= end_index+1 || !offset)
                goto out;
do_it:
        lock_kernel();
        if (NFS_SERVER(inode)->wsize >= PAGE_CACHE_SIZE && !IS_SYNC(inode)) {
                err = nfs_writepage_async(NULL, inode, page, 0, offset);
                if (err >= 0)
                        err = 0;
        } else {
                err = nfs_writepage_sync(NULL, inode, page, 0, offset); 
                if (err == offset)
                        err = 0;
        }
        unlock_kernel();
out:
        unlock_page(page);
        return err; 
}

int
nfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
{
        struct inode *inode = mapping->host;
        int is_sync = !wbc->nonblocking;
        int err;

        err = generic_writepages(mapping, wbc);
        if (err)
                goto out;
        err = nfs_flush_file(inode, NULL, 0, 0, 0);
        if (err < 0)
                goto out;
        if (wbc->sync_mode == WB_SYNC_HOLD)
                goto out;
        if (is_sync && wbc->sync_mode == WB_SYNC_ALL) {
                err = nfs_wb_all(inode);
        } else
                nfs_commit_file(inode, NULL, 0, 0, 0);
out:
        return err;
}

/*
 * Insert a write request into an inode
 */
static inline int
nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        int error;

        error = radix_tree_insert(&nfsi->nfs_page_tree, req->wb_index, req);
        BUG_ON(error == -EEXIST);
        if (error)
                return error;
        if (!nfsi->npages)
                igrab(inode);
        nfsi->npages++;
        req->wb_count++;
        return 0;
}

/*
 * Insert a write request into an inode
 */
static inline void
nfs_inode_remove_request(struct nfs_page *req)
{
        struct nfs_inode *nfsi;
        struct inode *inode;

        BUG_ON (!NFS_WBACK_BUSY(req));
        spin_lock(&nfs_wreq_lock);
        inode = req->wb_inode;
        nfsi = NFS_I(inode);
        radix_tree_delete(&nfsi->nfs_page_tree, req->wb_index);
        nfsi->npages--;
        if (!nfsi->npages) {
                spin_unlock(&nfs_wreq_lock);
                iput(inode);
        } else
                spin_unlock(&nfs_wreq_lock);
        nfs_clear_request(req);
        nfs_release_request(req);
}

/*
 * Find a request
 */
static inline struct nfs_page *
_nfs_find_request(struct inode *inode, unsigned long index)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_page *req;

        req = (struct nfs_page*)radix_tree_lookup(&nfsi->nfs_page_tree, index);
        if (req)
                req->wb_count++;
        return req;
}

static struct nfs_page *
nfs_find_request(struct inode *inode, unsigned long index)
{
        struct nfs_page         *req;

        spin_lock(&nfs_wreq_lock);
        req = _nfs_find_request(inode, index);
        spin_unlock(&nfs_wreq_lock);
        return req;
}

/*
 * Add a request to the inode's dirty list.
 */
static inline void
nfs_mark_request_dirty(struct nfs_page *req)
{
        struct inode *inode = req->wb_inode;
        struct nfs_inode *nfsi = NFS_I(inode);

        spin_lock(&nfs_wreq_lock);
        nfs_list_add_request(req, &nfsi->dirty);
        nfsi->ndirty++;
        spin_unlock(&nfs_wreq_lock);
        inc_page_state(nr_dirty);
        mark_inode_dirty(inode);
}

/*
 * Check if a request is dirty
 */
static inline int
nfs_dirty_request(struct nfs_page *req)
{
        struct nfs_inode *nfsi = NFS_I(req->wb_inode);
        return !list_empty(&req->wb_list) && req->wb_list_head == &nfsi->dirty;
}

#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
/*
 * Add a request to the inode's commit list.
 */
static inline void
nfs_mark_request_commit(struct nfs_page *req)
{
        struct inode *inode = req->wb_inode;
        struct nfs_inode *nfsi = NFS_I(inode);

        spin_lock(&nfs_wreq_lock);
        nfs_list_add_request(req, &nfsi->commit);
        nfsi->ncommit++;
        spin_unlock(&nfs_wreq_lock);
        inc_page_state(nr_unstable);
        mark_inode_dirty(inode);
}
#endif

/*
 * Wait for a request to complete.
 *
 * Interruptible by signals only if mounted with intr flag.
 */
static int
nfs_wait_on_requests(struct inode *inode, struct file *file, unsigned long idx_start, unsigned int npages)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_page *req;
        unsigned long           idx_end, next;
        unsigned int            res = 0;
        int                     error;

        if (npages == 0)
                idx_end = ~0;
        else
                idx_end = idx_start + npages - 1;

        spin_lock(&nfs_wreq_lock);
        next = idx_start;
        while (radix_tree_gang_lookup(&nfsi->nfs_page_tree, (void **)&req, next, 1)) {
                if (req->wb_index > idx_end)
                        break;

                next = req->wb_index + 1;
                if (file && req->wb_file != file)
                        continue;
                if (!NFS_WBACK_BUSY(req))
                        continue;

                req->wb_count++;
                spin_unlock(&nfs_wreq_lock);
                error = nfs_wait_on_request(req);
                nfs_release_request(req);
                if (error < 0)
                        return error;
                spin_lock(&nfs_wreq_lock);
                next = idx_start;
                res++;
        }
        spin_unlock(&nfs_wreq_lock);
        return res;
}

/*
 * nfs_scan_dirty - Scan an inode for dirty requests
 * @inode: NFS inode to scan
 * @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 requests from the inode's dirty page list.
 * The requests are *not* checked to ensure that they form a contiguous set.
 */
static int
nfs_scan_dirty(struct inode *inode, struct list_head *dst, struct file *file, unsigned long idx_start, unsigned int npages)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        int     res;
        res = nfs_scan_list(&nfsi->dirty, dst, file, idx_start, npages);
        nfsi->ndirty -= res;
        sub_page_state(nr_dirty,res);
        if ((nfsi->ndirty == 0) != list_empty(&nfsi->dirty))
                printk(KERN_ERR "NFS: desynchronized value of nfs_i.ndirty.\n");
        return res;
}

#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
/*
 * nfs_scan_commit - Scan an inode for commit requests
 * @inode: NFS inode to scan
 * @dst: destination list
 * @file: if set, ensure we collect requests from this file only.
 * @idx_start: lower bound of page->index to scan.
 * @npages: idx_start + npages sets the upper bound to scan.
 *
 * Moves requests from the inode's 'commit' request list.
 * The requests are *not* checked to ensure that they form a contiguous set.
 */
static int
nfs_scan_commit(struct inode *inode, struct list_head *dst, struct file *file, unsigned long idx_start, unsigned int npages)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        int     res;
        res = nfs_scan_list(&nfsi->commit, dst, file, idx_start, npages);
        nfsi->ncommit -= res;
        if ((nfsi->ncommit == 0) != list_empty(&nfsi->commit))
                printk(KERN_ERR "NFS: desynchronized value of nfs_i.ncommit.\n");
        return res;
}
#endif


/*
 * Try to update any existing write request, or create one if there is none.
 * In order to match, the request's credentials must match those of
 * the calling process.
 *
 * Note: Should always be called with the Page Lock held!
 */
static struct nfs_page *
nfs_update_request(struct file* file, struct inode *inode, struct page *page,
                   unsigned int offset, unsigned int bytes)
{
        struct nfs_page         *req, *new = NULL;
        unsigned long           rqend, end;

        end = offset + bytes;

        for (;;) {
                /* Loop over all inode entries and see if we find
                 * A request for the page we wish to update
                 */
                spin_lock(&nfs_wreq_lock);
                req = _nfs_find_request(inode, page->index);
                if (req) {
                        if (!nfs_lock_request_dontget(req)) {
                                int error;
                                spin_unlock(&nfs_wreq_lock);
                                error = nfs_wait_on_request(req);
                                nfs_release_request(req);
                                if (error < 0)
                                        return ERR_PTR(error);
                                continue;
                        }
                        spin_unlock(&nfs_wreq_lock);
                        if (new)
                                nfs_release_request(new);
                        break;
                }

                if (new) {
                        int error;
                        nfs_lock_request_dontget(new);
                        error = nfs_inode_add_request(inode, new);
                        if (error) {
                                spin_unlock(&nfs_wreq_lock);
                                nfs_unlock_request(new);
                                return ERR_PTR(error);
                        }
                        spin_unlock(&nfs_wreq_lock);
                        nfs_mark_request_dirty(new);
                        return new;
                }
                spin_unlock(&nfs_wreq_lock);

                new = nfs_create_request(nfs_file_cred(file), inode, page, offset, bytes);
                if (IS_ERR(new))
                        return new;
                if (file) {
                        new->wb_file = file;
                        get_file(file);
                }
        }

        /* We have a request for our page.
         * If the creds don't match, or the
         * page addresses don't match,
         * tell the caller to wait on the conflicting
         * request.
         */
        rqend = req->wb_offset + req->wb_bytes;
        if (req->wb_file != file
            || req->wb_page != page
            || !nfs_dirty_request(req)
            || offset > rqend || end < req->wb_offset) {
                nfs_unlock_request(req);
                return ERR_PTR(-EBUSY);
        }

        /* Okay, the request matches. Update the region */
        if (offset < req->wb_offset) {
                req->wb_offset = offset;
                req->wb_pgbase = offset;
                req->wb_bytes = rqend - req->wb_offset;
        }

        if (end > rqend)
                req->wb_bytes = end - req->wb_offset;

        return req;
}

/*
 * This is the strategy routine for NFS.
 * It is called by nfs_updatepage whenever the user wrote up to the end
 * of a page.
 *
 * We always try to submit a set of requests in parallel so that the
 * server's write code can gather writes. This is mainly for the benefit
 * of NFSv2.
 *
 * We never submit more requests than we think the remote can handle.
 * For UDP sockets, we make sure we don't exceed the congestion window;
 * for TCP, we limit the number of requests to 8.
 *
 * NFS_STRATEGY_PAGES gives the minimum number of requests for NFSv2 that
 * should be sent out in one go. This is for the benefit of NFSv2 servers
 * that perform write gathering.
 *
 * FIXME: Different servers may have different sweet spots.
 * Record the average congestion window in server struct?
 */
#define NFS_STRATEGY_PAGES      8
static void
nfs_strategy(struct inode *inode)
{
        unsigned int    dirty, wpages;

        dirty  = NFS_I(inode)->ndirty;
        wpages = NFS_SERVER(inode)->wpages;
#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
        if (NFS_PROTO(inode)->version == 2) {
                if (dirty >= NFS_STRATEGY_PAGES * wpages)
                        nfs_flush_file(inode, NULL, 0, 0, 0);
        } else if (dirty >= wpages)
                nfs_flush_file(inode, NULL, 0, 0, 0);
#else
        if (dirty >= NFS_STRATEGY_PAGES * wpages)
                nfs_flush_file(inode, NULL, 0, 0, 0);
#endif
}

int
nfs_flush_incompatible(struct file *file, struct page *page)
{
        struct inode    *inode = page->mapping->host;
        struct rpc_cred *cred = nfs_file_cred(file);
        struct nfs_page *req;
        int             status = 0;
        /*
         * Look for a request corresponding to this page. If there
         * is one, and it belongs to another file, we flush it out
         * before we try to copy anything into the page. Do this
         * due to the lack of an ACCESS-type call in NFSv2.
         * Also do the same if we find a request from an existing
         * dropped page.
         */
        req = nfs_find_request(inode, page->index);
        if (req) {
                if (req->wb_file != file || req->wb_cred != cred || req->wb_page != page)
                        status = nfs_wb_page(inode, page);
                nfs_release_request(req);
        }
        return (status < 0) ? status : 0;
}

/*
 * Update and possibly write a cached page of an NFS file.
 *
 * XXX: Keep an eye on generic_file_read to make sure it doesn't do bad
 * things with a page scheduled for an RPC call (e.g. invalidate it).
 */
int
nfs_updatepage(struct file *file, struct page *page, unsigned int offset, unsigned int count)
{
        struct dentry   *dentry = file->f_dentry;
        struct inode    *inode = page->mapping->host;
        struct nfs_page *req;
        loff_t          end;
        int             status = 0;

        dprintk("NFS:      nfs_updatepage(%s/%s %d@%Ld)\n",
                dentry->d_parent->d_name.name, dentry->d_name.name,
                count, (long long)(page_offset(page) +offset));

        /*
         * If wsize is smaller than page size, update and write
         * page synchronously.
         */
        if (NFS_SERVER(inode)->wsize < PAGE_CACHE_SIZE || IS_SYNC(inode)) {
                status = nfs_writepage_sync(file, inode, page, offset, count);
                if (status > 0) {
                        if (offset == 0 && status == PAGE_CACHE_SIZE)
                                SetPageUptodate(page);
                        return 0;
                }
                return status;
        }

        /*
         * Try to find an NFS request corresponding to this page
         * and update it.
         * If the existing request cannot be updated, we must flush
         * it out now.
         */
        do {
                req = nfs_update_request(file, inode, page, offset, count);
                status = (IS_ERR(req)) ? PTR_ERR(req) : 0;
                if (status != -EBUSY)
                        break;
                /* Request could not be updated. Flush it out and try again */
                status = nfs_wb_page(inode, page);
        } while (status >= 0);
        if (status < 0)
                goto done;

        status = 0;
        end = ((loff_t)page->index<<PAGE_CACHE_SHIFT) + (loff_t)(offset + count);
        if (inode->i_size < end)
                inode->i_size = end;

        /* If we wrote past the end of the page.
         * Call the strategy routine so it can send out a bunch
         * of requests.
         */
        if (req->wb_pgbase == 0 && req->wb_bytes == PAGE_CACHE_SIZE) {
                SetPageUptodate(page);
                nfs_unlock_request(req);
                nfs_strategy(inode);
        } else
                nfs_unlock_request(req);
done:
        dprintk("NFS:      nfs_updatepage returns %d (isize %Ld)\n",
                                                status, (long long)inode->i_size);
        if (status < 0)
                ClearPageUptodate(page);
        return status;
}

/*
 * Set up the argument/result storage required for the RPC call.
 */
static void
nfs_write_rpcsetup(struct list_head *head, struct nfs_write_data *data, int how)
{
        struct rpc_task         *task = &data->task;
        struct inode            *inode;
        struct nfs_page         *req;
        struct page             **pages;
        unsigned int            count;

        /* Set up the RPC argument and reply structs
         * NB: take care not to mess about with data->commit et al. */

        pages = data->pagevec;
        count = 0;
        while (!list_empty(head)) {
                req = nfs_list_entry(head->next);
                nfs_list_remove_request(req);
                nfs_list_add_request(req, &data->pages);
                SetPageWriteback(req->wb_page);
                *pages++ = req->wb_page;
                count += req->wb_bytes;
        }
        req = nfs_list_entry(data->pages.next);
        data->inode = inode = req->wb_inode;
        data->cred = req->wb_cred;

        NFS_PROTO(inode)->write_setup(data, count, how);

        dprintk("NFS: %4d initiated write call (req %s/%Ld, %u bytes @ offset %Lu)\n",
                task->tk_pid,
                inode->i_sb->s_id,
                (long long)NFS_FILEID(inode),
                count,
                (unsigned long long)req_offset(req));
}

/*
 * Create an RPC task for the given write request and kick it.
 * The page must have been locked by the caller.
 *
 * It may happen that the page we're passed is not marked dirty.
 * This is the case if nfs_updatepage detects a conflicting request
 * that has been written but not committed.
 */
static int
nfs_flush_one(struct list_head *head, struct inode *inode, int how)
{
        struct rpc_clnt         *clnt = NFS_CLIENT(inode);
        struct nfs_write_data   *data;
        sigset_t                oldset;

        data = nfs_writedata_alloc();
        if (!data)
                goto out_bad;

        /* Set up the argument struct */
        nfs_write_rpcsetup(head, data, how);

        rpc_clnt_sigmask(clnt, &oldset);
        lock_kernel();
        rpc_execute(&data->task);
        unlock_kernel();
        rpc_clnt_sigunmask(clnt, &oldset);
        return 0;
 out_bad:
        while (!list_empty(head)) {
                struct nfs_page *req = nfs_list_entry(head->next);
                nfs_list_remove_request(req);
                nfs_mark_request_dirty(req);
                nfs_unlock_request(req);
        }
        return -ENOMEM;
}

int
nfs_flush_list(struct list_head *head, int wpages, int how)
{
        LIST_HEAD(one_request);
        struct nfs_page         *req;
        int                     error = 0;
        unsigned int            pages = 0;

        while (!list_empty(head)) {
                pages += nfs_coalesce_requests(head, &one_request, wpages);
                req = nfs_list_entry(one_request.next);
                error = nfs_flush_one(&one_request, req->wb_inode, how);
                if (error < 0)
                        break;
        }
        if (error >= 0)
                return pages;

        while (!list_empty(head)) {
                req = nfs_list_entry(head->next);
                nfs_list_remove_request(req);
                nfs_mark_request_dirty(req);
                nfs_unlock_request(req);
        }
        return error;
}


/*
 * This function is called when the WRITE call is complete.
 */
void
nfs_writeback_done(struct rpc_task *task)
{
        struct nfs_write_data   *data = (struct nfs_write_data *) task->tk_calldata;
        struct nfs_writeargs    *argp = &data->args;
        struct nfs_writeres     *resp = &data->res;
        struct nfs_page         *req;
        struct page             *page;

        dprintk("NFS: %4d nfs_writeback_done (status %d)\n",
                task->tk_pid, task->tk_status);

        /* We can't handle that yet but we check for it nevertheless */
        if (resp->count < argp->count && task->tk_status >= 0) {
                static unsigned long    complain;
                if (time_before(complain, jiffies)) {
                        printk(KERN_WARNING
                               "NFS: Server wrote less than requested.\n");
                        complain = jiffies + 300 * HZ;
                }
                /* Can't do anything about it right now except throw
                 * an error. */
                task->tk_status = -EIO;
        }
#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
        if (data->verf.committed < argp->stable && task->tk_status >= 0) {
                /* We tried a write call, but the server did not
                 * commit data to stable storage even though we
                 * requested it.
                 * Note: There is a known bug in Tru64 < 5.0 in which
                 *       the server reports NFS_DATA_SYNC, but performs
                 *       NFS_FILE_SYNC. We therefore implement this checking
                 *       as a dprintk() in order to avoid filling syslog.
                 */
                static unsigned long    complain;

                if (time_before(complain, jiffies)) {
                        dprintk("NFS: faulty NFS server %s:"
                                " (committed = %d) != (stable = %d)\n",
                                NFS_SERVER(data->inode)->hostname,
                                data->verf.committed, argp->stable);
                        complain = jiffies + 300 * HZ;
                }
        }
#endif

        /*
         * Update attributes as result of writeback.
         * FIXME: There is an inherent race with invalidate_inode_pages and
         *        writebacks since the page->count is kept > 1 for as long
         *        as the page has a write request pending.
         */
        while (!list_empty(&data->pages)) {
                req = nfs_list_entry(data->pages.next);
                nfs_list_remove_request(req);
                page = req->wb_page;

                dprintk("NFS: write (%s/%Ld %d@%Ld)",
                        req->wb_inode->i_sb->s_id,
                        (long long)NFS_FILEID(req->wb_inode),
                        req->wb_bytes,
                        (long long)req_offset(req));

                if (task->tk_status < 0) {
                        ClearPageUptodate(page);
                        SetPageError(page);
                        if (req->wb_file)
                                req->wb_file->f_error = task->tk_status;
                        end_page_writeback(page);
                        nfs_inode_remove_request(req);
                        dprintk(", error = %d\n", task->tk_status);
                        goto next;
                }
                end_page_writeback(page);

#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
                if (argp->stable != NFS_UNSTABLE || data->verf.committed == NFS_FILE_SYNC) {
                        nfs_inode_remove_request(req);
                        dprintk(" OK\n");
                        goto next;
                }
                memcpy(&req->wb_verf, &data->verf, sizeof(req->wb_verf));
                nfs_mark_request_commit(req);
                dprintk(" marked for commit\n");
#else
                nfs_inode_remove_request(req);
#endif
        next:
                nfs_unlock_request(req);
        }
}


#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
/*
 * Set up the argument/result storage required for the RPC call.
 */
static void
nfs_commit_rpcsetup(struct list_head *head, struct nfs_write_data *data, int how)
{
        struct rpc_task         *task = &data->task;
        struct nfs_page         *first, *last;
        struct inode            *inode;
        loff_t                  start, end, len;

        /* Set up the RPC argument and reply structs
         * NB: take care not to mess about with data->commit et al. */

        list_splice_init(head, &data->pages);
        first = nfs_list_entry(data->pages.next);
        last = nfs_list_entry(data->pages.prev);
        inode = first->wb_inode;

        /*
         * Determine the offset range of requests in the COMMIT call.
         * We rely on the fact that data->pages is an ordered list...
         */
        start = req_offset(first);
        end = req_offset(last) + last->wb_bytes;
        len = end - start;
        /* If 'len' is not a 32-bit quantity, pass '0' in the COMMIT call */
        if (end >= inode->i_size || len < 0 || len > (~((u32)0) >> 1))
                len = 0;

        data->inode       = inode;
        data->cred        = first->wb_cred;

        NFS_PROTO(inode)->commit_setup(data, start, len, how);
        
        dprintk("NFS: %4d initiated commit call\n", task->tk_pid);
}

/*
 * Commit dirty pages
 */
int
nfs_commit_list(struct list_head *head, int how)
{
        struct rpc_clnt         *clnt;
        struct nfs_write_data   *data;
        struct nfs_page         *req;
        sigset_t                oldset;

        data = nfs_commit_alloc();

        if (!data)
                goto out_bad;

        /* Set up the argument struct */
        nfs_commit_rpcsetup(head, data, how);
        clnt = NFS_CLIENT(data->inode);

        rpc_clnt_sigmask(clnt, &oldset);
        lock_kernel();
        rpc_execute(&data->task);
        unlock_kernel();
        rpc_clnt_sigunmask(clnt, &oldset);
        return 0;
 out_bad:
        while (!list_empty(head)) {
                req = nfs_list_entry(head->next);
                nfs_list_remove_request(req);
                nfs_mark_request_commit(req);
                nfs_unlock_request(req);
        }
        return -ENOMEM;
}

/*
 * COMMIT call returned
 */
void
nfs_commit_done(struct rpc_task *task)
{
        struct nfs_write_data   *data = (struct nfs_write_data *)task->tk_calldata;
        struct nfs_page         *req;
        int res = 0;

        dprintk("NFS: %4d nfs_commit_done (status %d)\n",
                                task->tk_pid, task->tk_status);

        while (!list_empty(&data->pages)) {
                req = nfs_list_entry(data->pages.next);
                nfs_list_remove_request(req);

                dprintk("NFS: commit (%s/%Ld %d@%Ld)",
                        req->wb_inode->i_sb->s_id,
                        (long long)NFS_FILEID(req->wb_inode),
                        req->wb_bytes,
                        (long long)req_offset(req));
                if (task->tk_status < 0) {
                        if (req->wb_file)
                                req->wb_file->f_error = task->tk_status;
                        nfs_inode_remove_request(req);
                        dprintk(", error = %d\n", task->tk_status);
                        goto next;
                }

                /* Okay, COMMIT succeeded, apparently. Check the verifier
                 * returned by the server against all stored verfs. */
                if (!memcmp(req->wb_verf.verifier, data->verf.verifier, sizeof(data->verf.verifier))) {
                        /* We have a match */
                        nfs_inode_remove_request(req);
                        dprintk(" OK\n");
                        goto next;
                }
                /* We have a mismatch. Write the page again */
                dprintk(" mismatch\n");
                nfs_mark_request_dirty(req);
        next:
                nfs_unlock_request(req);
                res++;
        }
        sub_page_state(nr_unstable,res);
}
#endif

int nfs_flush_file(struct inode *inode, struct file *file, unsigned long idx_start,
                   unsigned int npages, int how)
{
        LIST_HEAD(head);
        int                     res,
                                error = 0;

        spin_lock(&nfs_wreq_lock);
        res = nfs_scan_dirty(inode, &head, file, idx_start, npages);
        spin_unlock(&nfs_wreq_lock);
        if (res)
                error = nfs_flush_list(&head, NFS_SERVER(inode)->wpages, how);
        if (error < 0)
                return error;
        return res;
}

#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
int nfs_commit_file(struct inode *inode, struct file *file, unsigned long idx_start,
                    unsigned int npages, int how)
{
        LIST_HEAD(head);
        int                     res,
                                error = 0;

        spin_lock(&nfs_wreq_lock);
        res = nfs_scan_commit(inode, &head, file, idx_start, npages);
        spin_unlock(&nfs_wreq_lock);
        if (res)
                error = nfs_commit_list(&head, how);
        if (error < 0)
                return error;
        return res;
}
#endif

int nfs_sync_file(struct inode *inode, struct file *file, unsigned long idx_start,
                  unsigned int npages, int how)
{
        int     error,
                wait;

        wait = how & FLUSH_WAIT;
        how &= ~FLUSH_WAIT;

        if (!inode && file)
                inode = file->f_dentry->d_inode;

        do {
                error = 0;
                if (wait)
                        error = nfs_wait_on_requests(inode, file, idx_start, npages);
                if (error == 0)
                        error = nfs_flush_file(inode, file, idx_start, npages, how);
#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
                if (error == 0)
                        error = nfs_commit_file(inode, file, idx_start, npages, how);
#endif
        } while (error > 0);
        return error;
}

int nfs_init_writepagecache(void)
{
        nfs_wdata_cachep = kmem_cache_create("nfs_write_data",
                                             sizeof(struct nfs_write_data),
                                             0, SLAB_HWCACHE_ALIGN,
                                             NULL, NULL);
        if (nfs_wdata_cachep == NULL)
                return -ENOMEM;

        nfs_wdata_mempool = mempool_create(MIN_POOL_WRITE,
                                           mempool_alloc_slab,
                                           mempool_free_slab,
                                           nfs_wdata_cachep);
        if (nfs_wdata_mempool == NULL)
                return -ENOMEM;

        nfs_commit_mempool = mempool_create(MIN_POOL_COMMIT,
                                           mempool_alloc_slab,
                                           mempool_free_slab,
                                           nfs_wdata_cachep);
        if (nfs_commit_mempool == NULL)
                return -ENOMEM;

        return 0;
}

void nfs_destroy_writepagecache(void)
{
        mempool_destroy(nfs_commit_mempool);
        mempool_destroy(nfs_wdata_mempool);
        if (kmem_cache_destroy(nfs_wdata_cachep))
                printk(KERN_INFO "nfs_write_data: not all structures were freed\n");
}