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[linux-2.6/history.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/mempool.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>

#define NFSDBG_FACILITY         NFSDBG_PAGECACHE

static int nfs_pagein_one(struct list_head *, struct inode *);

static kmem_cache_t *nfs_rdata_cachep;
static mempool_t *nfs_rdata_mempool;

#define MIN_POOL_READ   (32)

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

static __inline__ void nfs_readdata_free(struct nfs_read_data *p)
{
        mempool_free(p, nfs_rdata_mempool);
}

void nfs_readdata_release(struct rpc_task *task)
{
        struct nfs_read_data   *data = (struct nfs_read_data *)task->tk_calldata;
        nfs_readdata_free(data);
}

/*
 * Read a page synchronously.
 */
static int
nfs_readpage_sync(struct file *file, 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 = {
                .flags          = (IS_SWAPFILE(inode)? NFS_RPC_SWAPFLAGS : 0),
                .cred           = NULL,
                .inode          = inode,
                .args           = {
                        .fh             = NFS_FH(inode),
                        .pages          = &page,
                        .pgbase         = 0UL,
                        .count          = rsize,
                },
                .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, file);
                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;
                if (result < rdata.args.count)  /* NFSv2ism */
                        break;
        } while (count);

        if (count)
                memclear_highpage_flush(page, rdata.args.pgbase, count);
        SetPageUptodate(page);
        if (PageError(page))
                ClearPageError(page);
        result = 0;

io_error:
        unlock_page(page);
        return result;
}

static int
nfs_readpage_async(struct file *file, struct inode *inode, struct page *page)
{
        LIST_HEAD(one_request);
        struct nfs_page *new;

        new = nfs_create_request(file, inode, page, 0, PAGE_CACHE_SIZE);
        if (IS_ERR(new)) {
                unlock_page(page);
                return PTR_ERR(new);
        }
        nfs_lock_request(new);
        nfs_list_add_request(new, &one_request);
        nfs_pagein_one(&one_request, inode);
        return 0;
}

/*
 * Set up the NFS read request struct
 */
static void
nfs_read_rpcsetup(struct list_head *head, struct nfs_read_data *data)
{
        struct inode            *inode;
        struct nfs_page         *req;
        struct page             **pages;
        unsigned int            count;

        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);
                *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)->read_setup(data, count);

        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)req_offset(req));
}

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

        while (!list_empty(head)) {
                req = nfs_list_entry(head->next);
                page = req->wb_page;
                nfs_list_remove_request(req);
                SetPageError(page);
                unlock_page(page);
                nfs_clear_request(req);
                nfs_release_request(req);
                nfs_unlock_request(req);
        }
}

static int
nfs_pagein_one(struct list_head *head, struct inode *inode)
{
        struct rpc_clnt         *clnt = NFS_CLIENT(inode);
        struct nfs_read_data    *data;
        sigset_t                oldset;

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

        nfs_read_rpcsetup(head, data);

        /* Start the async call */
        rpc_clnt_sigmask(clnt, &oldset);
        lock_kernel();
        rpc_execute(&data->task);
        unlock_kernel();
        rpc_clnt_sigunmask(clnt, &oldset);
        return 0;
out_bad:
        nfs_async_read_error(head);
        return -ENOMEM;
}

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_inode);
                if (error < 0)
                        break;
        }
        if (error >= 0)
                return pages;

        nfs_async_read_error(head);
        return error;
}

/*
 * This is the callback from RPC telling us whether a reply was
 * received or some error occurred (timeout or socket shutdown).
 */
void
nfs_readpage_result(struct rpc_task *task)
{
        struct nfs_read_data *data = (struct nfs_read_data *)task->tk_calldata;
        unsigned int count = data->res.count;

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

        while (!list_empty(&data->pages)) {
                struct nfs_page *req = nfs_list_entry(data->pages.next);
                struct page *page = req->wb_page;
                nfs_list_remove_request(req);

                if (task->tk_status >= 0) {
                        if (count < PAGE_CACHE_SIZE) {
                                memclear_highpage_flush(page,
                                                        req->wb_pgbase + count,
                                                        req->wb_bytes - count);

                                count = 0;
                        } else
                                count -= PAGE_CACHE_SIZE;
                        SetPageUptodate(page);
                } else
                        SetPageError(page);
                unlock_page(page);

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

/*
 * Read a page over NFS.
 * We read the page synchronously in the following cases:
 *  -   The NFS rsize is smaller than PAGE_CACHE_SIZE. We could kludge our way
 *      around this by creating several consecutive read requests, but
 *      that's hardly worth it.
 *  -   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 inode *inode = page->mapping->host;
        int             error;

        dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
                page, PAGE_CACHE_SIZE, page->index);
        /*
         * 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 (!PageError(page) && NFS_SERVER(inode)->rsize >= PAGE_CACHE_SIZE) {
                error = nfs_readpage_async(file, inode, page);
                goto out;
        }

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

out_error:
        unlock_page(page);
        goto out;
}

struct nfs_readdesc {
        struct list_head *head;
        struct file *filp;
};

static int
readpage_sync_filler(void *data, struct page *page)
{
        struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
        return nfs_readpage_sync(desc->filp, page->mapping->host, page);
}

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;

        nfs_wb_page(inode, page);
        new = nfs_create_request(desc->filp, inode, page, 0, PAGE_CACHE_SIZE);
        if (IS_ERR(new)) {
                        SetPageError(page);
                        unlock_page(page);
                        return PTR_ERR(new);
        }
        nfs_lock_request(new);
        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 = {
                .filp           = filp,
                .head           = &head,
        };
        struct nfs_server *server = NFS_SERVER(mapping->host);
        int is_sync = server->rsize < PAGE_CACHE_SIZE;
        int ret;

        ret = read_cache_pages(mapping, pages,
                               is_sync ? readpage_sync_filler :
                                         readpage_async_filler,
                               &desc);
        if (!list_empty(&head)) {
                int err = nfs_pagein_list(&head, server->rpages);
                if (!ret)
                        ret = err;
        }
        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(MIN_POOL_READ,
                                           mempool_alloc_slab,
                                           mempool_free_slab,
                                           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");
}