read.c

linux 内核源代码

		nfs_list_add_request(req, &data->pages);
		ClearPageError(req->wb_page);
		*pages++ = req->wb_page;
	}
	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;
}

/*
 * 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)
{
	int status;

	dprintk("NFS: %s: %5u, (status %d)\n", __FUNCTION__, 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, data->res.count);

	if (task->tk_status == -ESTALE) {
		set_bit(NFS_INO_STALE, &NFS_FLAGS(data->inode));
		nfs_mark_for_revalidate(data->inode);
	}
	return 0;
}

static int nfs_readpage_retry(struct rpc_task *task, struct nfs_read_data *data)
{
	struct nfs_readargs *argp = &data->args;
	struct nfs_readres *resp = &data->res;

	if (resp->eof || resp->count == argp->count)
		return 0;

	/* This is a short read! */
	nfs_inc_stats(data->inode, NFSIOS_SHORTREAD);
	/* Has the server at least made some progress? */
	if (resp->count == 0)
		return 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;
}

/*
 * 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 (nfs_readpage_result(task, data) != 0)
		return;

	if (likely(task->tk_status >= 0)) {
		nfs_readpage_truncate_uninitialised_page(data);
		if (nfs_readpage_retry(task, data) != 0)
			return;
	}
	if (unlikely(task->tk_status < 0))
		SetPageError(page);
	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 (data->res.eof)
		count = data->args.count;
	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);
	if (count == 0)
		return;
	/* Was this a short read? */
	if (data->res.eof || data->res.count == data->args.count)
		SetPageUptodate(*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;

	if (nfs_readpage_result(task, data) != 0)
		return;
	/*
	 * Note: nfs_readpage_retry may change the values of
	 * data->args. In the multi-page case, we therefore need
	 * to ensure that we call nfs_readpage_set_pages_uptodate()
	 * first.
	 */
	if (likely(task->tk_status >= 0)) {
		nfs_readpage_truncate_uninitialised_page(data);
		nfs_readpage_set_pages_uptodate(data);
		if (nfs_readpage_retry(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,
};

/*
 * 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_unlock;
	if (PageUptodate(page))
		goto out_unlock;

	error = -ESTALE;
	if (NFS_STALE(inode))
		goto out_unlock;

	if (file == NULL) {
		error = -EBADF;
		ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
		if (ctx == NULL)
			goto out_unlock;
	} else
		ctx = get_nfs_open_context(nfs_file_open_context(file));

	error = nfs_readpage_async(ctx, inode, page);

	put_nfs_open_context(ctx);
	return error;
out_unlock:
	unlock_page(page);
	return error;
}

struct nfs_readdesc {
	struct nfs_pageio_descriptor *pgio;
	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;
	int error;

	error = nfs_wb_page(inode, page);
	if (error)
		goto out_unlock;
	if (PageUptodate(page))
		goto out_unlock;

	len = nfs_page_length(page);
	if (len == 0)
		return nfs_return_empty_page(page);

	new = nfs_create_request(desc->ctx, inode, page, 0, len);
	if (IS_ERR(new))
		goto out_error;

	if (len < PAGE_CACHE_SIZE)
		zero_user_page(page, len, PAGE_CACHE_SIZE - len, KM_USER0);
	nfs_pageio_add_request(desc->pgio, new);
	return 0;
out_error:
	error = PTR_ERR(new);
	SetPageError(page);
out_unlock:
	unlock_page(page);
	return error;
}

int nfs_readpages(struct file *filp, struct address_space *mapping,
		struct list_head *pages, unsigned nr_pages)
{
	struct nfs_pageio_descriptor pgio;
	struct nfs_readdesc desc = {
		.pgio = &pgio,
	};
	struct inode *inode = mapping->host;
	struct nfs_server *server = NFS_SERVER(inode);
	size_t rsize = server->rsize;
	unsigned long npages;
	int ret = -ESTALE;

	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 (NFS_STALE(inode))
		goto out;

	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(nfs_file_open_context(filp));
	if (rsize < PAGE_CACHE_SIZE)
		nfs_pageio_init(&pgio, inode, nfs_pagein_multi, rsize, 0);
	else
		nfs_pageio_init(&pgio, inode, nfs_pagein_one, rsize, 0);

	ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);

	nfs_pageio_complete(&pgio);
	npages = (pgio.pg_bytes_written + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	nfs_add_stats(inode, NFSIOS_READPAGES, npages);
	put_nfs_open_context(desc.ctx);
out:
	return ret;
}

int __init nfs_init_readpagecache(void)
{
	nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
					     sizeof(struct nfs_read_data),
					     0, SLAB_HWCACHE_ALIGN,
					     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);
	kmem_cache_destroy(nfs_rdata_cachep);
}