NFS: Clean up and fix page zeroing when we have short reads

[deliverable/linux.git] / fs / nfs / read.c

/*
 * linux/fs/nfs/read.c
 *
 * Block I/O for NFS
 *
 * Partial copy of Linus' read cache modifications to fs/nfs/file.c
 * modified for async RPC by okir@monad.swb.de
 *
 * We do an ugly hack here in order to return proper error codes to the
 * user program when a read request failed: since generic_file_read
 * only checks the return value of inode->i_op->readpage() which is always 0
 * for async RPC, we set the error bit of the page to 1 when an error occurs,
 * and make nfs_readpage transmit requests synchronously when encountering this.
 * This is only a small problem, though, since we now retry all operations
 * within the RPC code when root squashing is suspected.
 */

#include <linux/config.h>
#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_page.h>
#include <linux/smp_lock.h>

#include <asm/system.h>

#include "iostat.h"

#define NFSDBG_FACILITY         NFSDBG_PAGECACHE

static int nfs_pagein_one(struct list_head *, struct inode *);
static const struct rpc_call_ops nfs_read_partial_ops;
static const struct rpc_call_ops nfs_read_full_ops;

static kmem_cache_t *nfs_rdata_cachep;
static mempool_t *nfs_rdata_mempool;

#define MIN_POOL_READ   (32)

struct nfs_read_data *nfs_readdata_alloc(unsigned int pagecount)
{
        struct nfs_read_data *p = mempool_alloc(nfs_rdata_mempool, SLAB_NOFS);

        if (p) {
                memset(p, 0, sizeof(*p));
                INIT_LIST_HEAD(&p->pages);
                if (pagecount < NFS_PAGEVEC_SIZE)
                        p->pagevec = &p->page_array[0];
                else {
                        size_t size = ++pagecount * sizeof(struct page *);
                        p->pagevec = kmalloc(size, GFP_NOFS);
                        if (p->pagevec) {
                                memset(p->pagevec, 0, size);
                        } else {
                                mempool_free(p, nfs_rdata_mempool);
                                p = NULL;
                        }
                }
        }
        return p;
}

void nfs_readdata_free(struct nfs_read_data *p)
{
        if (p && (p->pagevec != &p->page_array[0]))
                kfree(p->pagevec);
        mempool_free(p, nfs_rdata_mempool);
}

void nfs_readdata_release(void *data)
{
        nfs_readdata_free(data);
}

static
unsigned int nfs_page_length(struct inode *inode, struct page *page)
{
        loff_t i_size = i_size_read(inode);
        unsigned long idx;

        if (i_size <= 0)
                return 0;
        idx = (i_size - 1) >> PAGE_CACHE_SHIFT;
        if (page->index > idx)
                return 0;
        if (page->index != idx)
                return PAGE_CACHE_SIZE;
        return 1 + ((i_size - 1) & (PAGE_CACHE_SIZE - 1));
}

static
int nfs_return_empty_page(struct page *page)
{
        memclear_highpage_flush(page, 0, PAGE_CACHE_SIZE);
        SetPageUptodate(page);
        unlock_page(page);
        return 0;
}

static void nfs_readpage_truncate_uninitialised_page(struct nfs_read_data *data)
{
        unsigned int remainder = data->args.count - data->res.count;
        unsigned int base = data->args.pgbase + data->res.count;
        unsigned int pglen;
        struct page **pages;

        if (data->res.eof == 0 || remainder == 0)
                return;
        /*
         * Note: "remainder" can never be negative, since we check for
         *      this in the XDR code.
         */
        pages = &data->args.pages[base >> PAGE_CACHE_SHIFT];
        base &= ~PAGE_CACHE_MASK;
        pglen = PAGE_CACHE_SIZE - base;
        if (pglen < remainder)
                memclear_highpage_flush(*pages, base, pglen);
        else
                memclear_highpage_flush(*pages, base, remainder);
}

/*
 * Read a page synchronously.
 */
static int nfs_readpage_sync(struct nfs_open_context *ctx, struct inode *inode,
                struct page *page)
{
        unsigned int    rsize = NFS_SERVER(inode)->rsize;
        unsigned int    count = PAGE_CACHE_SIZE;
        int             result;
        struct nfs_read_data *rdata;

        rdata = nfs_readdata_alloc(1);
        if (!rdata)
                return -ENOMEM;

        memset(rdata, 0, sizeof(*rdata));
        rdata->flags = (IS_SWAPFILE(inode)? NFS_RPC_SWAPFLAGS : 0);
        rdata->cred = ctx->cred;
        rdata->inode = inode;
        INIT_LIST_HEAD(&rdata->pages);
        rdata->args.fh = NFS_FH(inode);
        rdata->args.context = ctx;
        rdata->args.pages = &page;
        rdata->args.pgbase = 0UL;
        rdata->args.count = rsize;
        rdata->res.fattr = &rdata->fattr;

        dprintk("NFS: nfs_readpage_sync(%p)\n", page);

        /*
         * This works now because the socket layer never tries to DMA
         * into this buffer directly.
         */
        do {
                if (count < rsize)
                        rdata->args.count = count;
                rdata->res.count = rdata->args.count;
                rdata->args.offset = page_offset(page) + rdata->args.pgbase;

                dprintk("NFS: nfs_proc_read(%s, (%s/%Ld), %Lu, %u)\n",
                        NFS_SERVER(inode)->hostname,
                        inode->i_sb->s_id,
                        (long long)NFS_FILEID(inode),
                        (unsigned long long)rdata->args.pgbase,
                        rdata->args.count);

                lock_kernel();
                result = NFS_PROTO(inode)->read(rdata);
                unlock_kernel();

                /*
                 * Even if we had a partial success we can't mark the page
                 * cache valid.
                 */
                if (result < 0) {
                        if (result == -EISDIR)
                                result = -EINVAL;
                        goto io_error;
                }
                count -= result;
                rdata->args.pgbase += result;
                nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, result);

                /* Note: result == 0 should only happen if we're caching
                 * a write that extends the file and punches a hole.
                 */
                if (rdata->res.eof != 0 || result == 0)
                        break;
        } while (count);
        spin_lock(&inode->i_lock);
        NFS_I(inode)->cache_validity |= NFS_INO_INVALID_ATIME;
        spin_unlock(&inode->i_lock);

        nfs_readpage_truncate_uninitialised_page(rdata);
        if (rdata->res.eof || rdata->res.count == rdata->args.count)
                SetPageUptodate(page);
        result = 0;

io_error:
        unlock_page(page);
        nfs_readdata_free(rdata);
        return result;
}

static int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
                struct page *page)
{
        LIST_HEAD(one_request);
        struct nfs_page *new;
        unsigned int len;

        len = nfs_page_length(inode, page);
        if (len == 0)
                return nfs_return_empty_page(page);
        new = nfs_create_request(ctx, inode, page, 0, len);
        if (IS_ERR(new)) {
                unlock_page(page);
                return PTR_ERR(new);
        }
        if (len < PAGE_CACHE_SIZE)
                memclear_highpage_flush(page, len, PAGE_CACHE_SIZE - len);

        nfs_list_add_request(new, &one_request);
        nfs_pagein_one(&one_request, inode);
        return 0;
}

static void nfs_readpage_release(struct nfs_page *req)
{
        unlock_page(req->wb_page);

        dprintk("NFS: read done (%s/%Ld %d@%Ld)\n",
                        req->wb_context->dentry->d_inode->i_sb->s_id,
                        (long long)NFS_FILEID(req->wb_context->dentry->d_inode),
                        req->wb_bytes,
                        (long long)req_offset(req));
        nfs_clear_request(req);
        nfs_release_request(req);
}

/*
 * Set up the NFS read request struct
 */
static void nfs_read_rpcsetup(struct nfs_page *req, struct nfs_read_data *data,
                const struct rpc_call_ops *call_ops,
                unsigned int count, unsigned int offset)
{
        struct inode            *inode;
        int flags;

        data->req         = req;
        data->inode       = inode = req->wb_context->dentry->d_inode;
        data->cred        = req->wb_context->cred;

        data->args.fh     = NFS_FH(inode);
        data->args.offset = req_offset(req) + offset;
        data->args.pgbase = req->wb_pgbase + offset;
        data->args.pages  = data->pagevec;
        data->args.count  = count;
        data->args.context = req->wb_context;

        data->res.fattr   = &data->fattr;
        data->res.count   = count;
        data->res.eof     = 0;
        nfs_fattr_init(&data->fattr);

        /* Set up the initial task struct. */
        flags = RPC_TASK_ASYNC | (IS_SWAPFILE(inode)? NFS_RPC_SWAPFLAGS : 0);
        rpc_init_task(&data->task, NFS_CLIENT(inode), flags, call_ops, data);
        NFS_PROTO(inode)->read_setup(data);

        data->task.tk_cookie = (unsigned long)inode;

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

static void
nfs_async_read_error(struct list_head *head)
{
        struct nfs_page *req;

        while (!list_empty(head)) {
                req = nfs_list_entry(head->next);
                nfs_list_remove_request(req);
                SetPageError(req->wb_page);
                nfs_readpage_release(req);
        }
}

/*
 * Start an async read operation
 */
static void nfs_execute_read(struct nfs_read_data *data)
{
        struct rpc_clnt *clnt = NFS_CLIENT(data->inode);
        sigset_t oldset;

        rpc_clnt_sigmask(clnt, &oldset);
        lock_kernel();
        rpc_execute(&data->task);
        unlock_kernel();
        rpc_clnt_sigunmask(clnt, &oldset);
}

/*
 * Generate multiple requests to fill a single page.
 *
 * We optimize to reduce the number of read operations on the wire.  If we
 * detect that we're reading a page, or an area of a page, that is past the
 * end of file, we do not generate NFS read operations but just clear the
 * parts of the page that would have come back zero from the server anyway.
 *
 * We rely on the cached value of i_size to make this determination; another
 * client can fill pages on the server past our cached end-of-file, but we
 * won't see the new data until our attribute cache is updated.  This is more
 * or less conventional NFS client behavior.
 */
static int nfs_pagein_multi(struct list_head *head, struct inode *inode)
{
        struct nfs_page *req = nfs_list_entry(head->next);
        struct page *page = req->wb_page;
        struct nfs_read_data *data;
        unsigned int rsize = NFS_SERVER(inode)->rsize;
        unsigned int nbytes, offset;
        int requests = 0;
        LIST_HEAD(list);

        nfs_list_remove_request(req);

        nbytes = req->wb_bytes;
        for(;;) {
                data = nfs_readdata_alloc(1);
                if (!data)
                        goto out_bad;
                INIT_LIST_HEAD(&data->pages);
                list_add(&data->pages, &list);
                requests++;
                if (nbytes <= rsize)
                        break;
                nbytes -= rsize;
        }
        atomic_set(&req->wb_complete, requests);

        ClearPageError(page);
        offset = 0;
        nbytes = req->wb_bytes;
        do {
                data = list_entry(list.next, struct nfs_read_data, pages);
                list_del_init(&data->pages);

                data->pagevec[0] = page;

                if (nbytes > rsize) {
                        nfs_read_rpcsetup(req, data, &nfs_read_partial_ops,
                                        rsize, offset);
                        offset += rsize;
                        nbytes -= rsize;
                } else {
                        nfs_read_rpcsetup(req, data, &nfs_read_partial_ops,
                                        nbytes, offset);
                        nbytes = 0;
                }
                nfs_execute_read(data);
        } while (nbytes != 0);

        return 0;

out_bad:
        while (!list_empty(&list)) {
                data = list_entry(list.next, struct nfs_read_data, pages);
                list_del(&data->pages);
                nfs_readdata_free(data);
        }
        SetPageError(page);
        nfs_readpage_release(req);
        return -ENOMEM;
}

static int nfs_pagein_one(struct list_head *head, struct inode *inode)
{
        struct nfs_page         *req;
        struct page             **pages;
        struct nfs_read_data    *data;
        unsigned int            count;

        if (NFS_SERVER(inode)->rsize < PAGE_CACHE_SIZE)
                return nfs_pagein_multi(head, inode);

        data = nfs_readdata_alloc(NFS_SERVER(inode)->rpages);
        if (!data)
                goto out_bad;

        INIT_LIST_HEAD(&data->pages);
        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);
                ClearPageError(req->wb_page);
                *pages++ = req->wb_page;
                count += req->wb_bytes;
        }
        req = nfs_list_entry(data->pages.next);

        nfs_read_rpcsetup(req, data, &nfs_read_full_ops, count, 0);

        nfs_execute_read(data);
        return 0;
out_bad:
        nfs_async_read_error(head);
        return -ENOMEM;
}

static int
nfs_pagein_list(struct list_head *head, int rpages)
{
        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, rpages);
                req = nfs_list_entry(one_request.next);
                error = nfs_pagein_one(&one_request, req->wb_context->dentry->d_inode);
                if (error < 0)
                        break;
        }
        if (error >= 0)
                return pages;

        nfs_async_read_error(head);
        return error;
}

/*
 * Handle a read reply that fills part of a page.
 */
static void nfs_readpage_result_partial(struct rpc_task *task, void *calldata)
{
        struct nfs_read_data *data = calldata;
        struct nfs_page *req = data->req;
        struct page *page = req->wb_page;
 
        if (likely(task->tk_status >= 0))
                nfs_readpage_truncate_uninitialised_page(data);
        else
                SetPageError(page);
        if (nfs_readpage_result(task, data) != 0)
                return;
        if (atomic_dec_and_test(&req->wb_complete)) {
                if (!PageError(page))
                        SetPageUptodate(page);
                nfs_readpage_release(req);
        }
}

static const struct rpc_call_ops nfs_read_partial_ops = {
        .rpc_call_done = nfs_readpage_result_partial,
        .rpc_release = nfs_readdata_release,
};

static void nfs_readpage_set_pages_uptodate(struct nfs_read_data *data)
{
        unsigned int count = data->res.count;
        unsigned int base = data->args.pgbase;
        struct page **pages;

        if (unlikely(count == 0))
                return;
        pages = &data->args.pages[base >> PAGE_CACHE_SHIFT];
        base &= ~PAGE_CACHE_MASK;
        count += base;
        for (;count >= PAGE_CACHE_SIZE; count -= PAGE_CACHE_SIZE, pages++)
                SetPageUptodate(*pages);
        /*
         * Was this an eof or a short read? If the latter, don't mark the page
         * as uptodate yet.
         */
        if (count > 0 && (data->res.eof || data->args.count == data->res.count))
                SetPageUptodate(*pages);
}

static void nfs_readpage_set_pages_error(struct nfs_read_data *data)
{
        unsigned int count = data->args.count;
        unsigned int base = data->args.pgbase;
        struct page **pages;

        pages = &data->args.pages[base >> PAGE_CACHE_SHIFT];
        base &= ~PAGE_CACHE_MASK;
        count += base;
        for (;count >= PAGE_CACHE_SIZE; count -= PAGE_CACHE_SIZE, pages++)
                SetPageError(*pages);
}

/*
 * This is the callback from RPC telling us whether a reply was
 * received or some error occurred (timeout or socket shutdown).
 */
static void nfs_readpage_result_full(struct rpc_task *task, void *calldata)
{
        struct nfs_read_data *data = calldata;

        /*
         * Note: nfs_readpage_result may change the values of
         * data->args. In the multi-page case, we therefore need
         * to ensure that we call the next nfs_readpage_set_page_uptodate()
         * first in the multi-page case.
         */
        if (likely(task->tk_status >= 0)) {
                nfs_readpage_truncate_uninitialised_page(data);
                nfs_readpage_set_pages_uptodate(data);
        } else
                nfs_readpage_set_pages_error(data);
        if (nfs_readpage_result(task, data) != 0)
                return;
        while (!list_empty(&data->pages)) {
                struct nfs_page *req = nfs_list_entry(data->pages.next);

                nfs_list_remove_request(req);
                nfs_readpage_release(req);
        }
}

static const struct rpc_call_ops nfs_read_full_ops = {
        .rpc_call_done = nfs_readpage_result_full,
        .rpc_release = nfs_readdata_release,
};

/*
 * This is the callback from RPC telling us whether a reply was
 * received or some error occurred (timeout or socket shutdown).
 */
int nfs_readpage_result(struct rpc_task *task, struct nfs_read_data *data)
{
        struct nfs_readargs *argp = &data->args;
        struct nfs_readres *resp = &data->res;
        int status;

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

        status = NFS_PROTO(data->inode)->read_done(task, data);
        if (status != 0)
                return status;

        nfs_add_stats(data->inode, NFSIOS_SERVERREADBYTES, resp->count);

        /* Is this a short read? */
        if (task->tk_status >= 0 && resp->count < argp->count && !resp->eof) {
                nfs_inc_stats(data->inode, NFSIOS_SHORTREAD);
                /* Has the server at least made some progress? */
                if (resp->count != 0) {
                        /* Yes, so retry the read at the end of the data */
                        argp->offset += resp->count;
                        argp->pgbase += resp->count;
                        argp->count -= resp->count;
                        rpc_restart_call(task);
                        return -EAGAIN;
                }
                task->tk_status = -EIO;
        }
        spin_lock(&data->inode->i_lock);
        NFS_I(data->inode)->cache_validity |= NFS_INO_INVALID_ATIME;
        spin_unlock(&data->inode->i_lock);
        return 0;
}

/*
 * Read a page over NFS.
 * We read the page synchronously in the following case:
 *  -   The error flag is set for this page. This happens only when a
 *      previous async read operation failed.
 */
int nfs_readpage(struct file *file, struct page *page)
{
        struct nfs_open_context *ctx;
        struct inode *inode = page->mapping->host;
        int             error;

        dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
                page, PAGE_CACHE_SIZE, page->index);
        nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
        nfs_add_stats(inode, NFSIOS_READPAGES, 1);

        /*
         * Try to flush any pending writes to the file..
         *
         * NOTE! Because we own the page lock, there cannot
         * be any new pending writes generated at this point
         * for this page (other pages can be written to).
         */
        error = nfs_wb_page(inode, page);
        if (error)
                goto out_error;

        if (file == NULL) {
                ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
                if (ctx == NULL)
                        return -EBADF;
        } else
                ctx = get_nfs_open_context((struct nfs_open_context *)
                                file->private_data);
        if (!IS_SYNC(inode)) {
                error = nfs_readpage_async(ctx, inode, page);
                goto out;
        }

        error = nfs_readpage_sync(ctx, inode, page);
        if (error < 0 && IS_SWAPFILE(inode))
                printk("Aiee.. nfs swap-in of page failed!\n");
out:
        put_nfs_open_context(ctx);
        return error;

out_error:
        unlock_page(page);
        return error;
}

struct nfs_readdesc {
        struct list_head *head;
        struct nfs_open_context *ctx;
};

static int
readpage_async_filler(void *data, struct page *page)
{
        struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
        struct inode *inode = page->mapping->host;
        struct nfs_page *new;
        unsigned int len;

        nfs_wb_page(inode, page);
        len = nfs_page_length(inode, page);
        if (len == 0)
                return nfs_return_empty_page(page);
        new = nfs_create_request(desc->ctx, inode, page, 0, len);
        if (IS_ERR(new)) {
                        SetPageError(page);
                        unlock_page(page);
                        return PTR_ERR(new);
        }
        if (len < PAGE_CACHE_SIZE)
                memclear_highpage_flush(page, len, PAGE_CACHE_SIZE - len);
        nfs_list_add_request(new, desc->head);
        return 0;
}

int nfs_readpages(struct file *filp, struct address_space *mapping,
                struct list_head *pages, unsigned nr_pages)
{
        LIST_HEAD(head);
        struct nfs_readdesc desc = {
                .head           = &head,
        };
        struct inode *inode = mapping->host;
        struct nfs_server *server = NFS_SERVER(inode);
        int ret;

        dprintk("NFS: nfs_readpages (%s/%Ld %d)\n",
                        inode->i_sb->s_id,
                        (long long)NFS_FILEID(inode),
                        nr_pages);
        nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);

        if (filp == NULL) {
                desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
                if (desc.ctx == NULL)
                        return -EBADF;
        } else
                desc.ctx = get_nfs_open_context((struct nfs_open_context *)
                                filp->private_data);
        ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
        if (!list_empty(&head)) {
                int err = nfs_pagein_list(&head, server->rpages);
                if (!ret)
                        nfs_add_stats(inode, NFSIOS_READPAGES, err);
                        ret = err;
        }
        put_nfs_open_context(desc.ctx);
        return ret;
}

int nfs_init_readpagecache(void)
{
        nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
                                             sizeof(struct nfs_read_data),
                                             0, SLAB_HWCACHE_ALIGN,
                                             NULL, NULL);
        if (nfs_rdata_cachep == NULL)
                return -ENOMEM;

        nfs_rdata_mempool = mempool_create_slab_pool(MIN_POOL_READ,
                                                     nfs_rdata_cachep);
        if (nfs_rdata_mempool == NULL)
                return -ENOMEM;

        return 0;
}

void nfs_destroy_readpagecache(void)
{
        mempool_destroy(nfs_rdata_mempool);
        if (kmem_cache_destroy(nfs_rdata_cachep))
                printk(KERN_INFO "nfs_read_data: not all structures were freed\n");
}