1 files changed, 232 insertions, 0 deletions
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
new file mode 100644
index 000000000..cf7c5ece7
--- /dev/null
+++ b/fs/nfs/read.c
@@ -0,0 +1,232 @@
+/*
+ * 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.
+ */
+
+#define NFS_NEED_XDR_TYPES
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fcntl.h>
+#include <linux/stat.h>
+#include <linux/mm.h>
+#include <linux/malloc.h>
+#include <linux/pagemap.h>
+#include <linux/sunrpc/clnt.h>
+#include <linux/nfs_fs.h>
+
+#include <asm/segment.h>
+#include <asm/system.h>
+
+#define NFSDBG_FACILITY		NFSDBG_PAGECACHE
+
+struct nfs_rreq {
+	struct inode *		ra_inode;	/* inode from which to read */
+	struct page *		ra_page;	/* page to be read */
+	struct nfs_readargs	ra_args;	/* XDR argument struct */
+	struct nfs_readres	ra_res;		/* ... and result struct */
+	struct nfs_fattr	ra_fattr;	/* fattr storage */
+};
+
+/* Hack for future NFS swap support */
+#ifndef IS_SWAPFILE
+# define IS_SWAPFILE(inode)	(0)
+#endif
+
+
+/*
+ * Set up the NFS read request struct
+ */
+static inline void
+nfs_readreq_setup(struct nfs_rreq *req, struct nfs_fh *fh,
+		  unsigned long offset, void *buffer, unsigned int rsize)
+{
+	req->ra_args.fh     = fh;
+	req->ra_args.offset = offset;
+	req->ra_args.count  = rsize;
+	req->ra_args.buffer = buffer;
+	req->ra_res.fattr   = &req->ra_fattr;
+	req->ra_res.count   = rsize;
+}
+
+
+/*
+ * Read a page synchronously.
+ */
+int
+nfs_readpage_sync(struct inode *inode, struct page *page)
+{
+	struct nfs_rreq	rqst;
+	unsigned long	offset = page->offset;
+	char		*buffer = (char *) page_address(page);
+	int		rsize = NFS_SERVER(inode)->rsize;
+	int		result, refresh = 0;
+	int		count = PAGE_SIZE;
+	int		flags = IS_SWAPFILE(inode)? NFS_RPC_SWAPFLAGS : 0;
+
+	dprintk("NFS: nfs_readpage_sync(%p)\n", page);
+	clear_bit(PG_error, &page->flags);
+
+	do {
+		if (count < rsize)
+			rsize = count;
+
+		dprintk("NFS: nfs_proc_read(%s, (%x,%lx), %ld, %d, %p)\n",
+			NFS_SERVER(inode)->hostname, inode->i_dev,
+			inode->i_ino, offset, rsize, buffer);
+
+		/* Set up arguments and perform rpc call */
+		nfs_readreq_setup(&rqst, NFS_FH(inode), offset, buffer, rsize);
+		result = rpc_call(NFS_CLIENT(inode), NFSPROC_READ,
+					&rqst.ra_args, &rqst.ra_res, flags);
+
+		/*
+		 * 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;
+		}
+		refresh = 1;
+		count  -= result;
+		offset += result;
+		buffer += result;
+		if (result < rsize)	/* NFSv2ism */
+			break;
+	} while (count);
+
+	memset(buffer, 0, count);
+	set_bit(PG_uptodate, &page->flags);
+	result = 0;
+
+io_error:
+	if (refresh)
+		nfs_refresh_inode(inode, &rqst.ra_fattr);
+	clear_bit(PG_locked, &page->flags);
+	wake_up(&page->wait);
+	return result;
+}
+
+/*
+ * 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(struct rpc_task *task)
+{
+	struct nfs_rreq	*req = (struct nfs_rreq *) task->tk_calldata;
+	struct page	*page = req->ra_page;
+	int		result = task->tk_status;
+	static int	succ = 0, fail = 0;
+
+	dprintk("NFS: %4d received callback for page %lx, result %d\n",
+			task->tk_pid, page_address(page), result);
+
+	if (result >= 0) {
+		result = req->ra_res.count;
+		if (result < PAGE_SIZE) {
+			memset((char *) page_address(page) + result, 0,
+							PAGE_SIZE - result);
+		}
+		nfs_refresh_inode(req->ra_inode, &req->ra_fattr);
+		set_bit(PG_uptodate, &page->flags);
+		succ++;
+	} else {
+		set_bit(PG_error, &page->flags);
+		fail++;
+		dprintk("NFS: %d successful reads, %d failures\n", succ, fail);
+	}
+	iput(req->ra_inode);
+	clear_bit(PG_locked, &page->flags);
+	wake_up(&page->wait);
+
+	free_page(page_address(page));
+
+	rpc_release_task(task);
+	kfree(req);
+}
+
+static inline int
+nfs_readpage_async(struct inode *inode, struct page *page)
+{
+	struct nfs_rreq	*req;
+	int		result, flags;
+
+	dprintk("NFS: nfs_readpage_async(%p)\n", page);
+	flags = RPC_TASK_ASYNC | (IS_SWAPFILE(inode)? NFS_RPC_SWAPFLAGS : 0);
+
+	if (NFS_CONGESTED(inode)
+	 || !(req = (struct nfs_rreq *) rpc_allocate(flags, sizeof(*req)))) {
+		dprintk("NFS: deferring async READ request.\n");
+		return -1;
+	}
+
+	/* Initialize request */
+	nfs_readreq_setup(req, NFS_FH(inode), page->offset,
+				(void *) page_address(page), PAGE_SIZE);
+	req->ra_inode = inode;
+	req->ra_page = page;
+
+	/* Start the async call */
+	dprintk("NFS: executing async READ request.\n");
+	result = rpc_do_call(NFS_CLIENT(inode), NFSPROC_READ,
+				&req->ra_args, &req->ra_res, flags,
+				nfs_readpage_result, req);
+
+	if (result >= 0) {
+		inode->i_count++;
+		atomic_inc(&page->count);
+		return 0;
+	}
+
+	dprintk("NFS: failed to enqueue async READ request.\n");
+	kfree(req);
+	return -1;
+}
+
+/*
+ * Read a page over NFS.
+ * We read the page synchronously in the following cases:
+ *  -	The file is a swap file. Swap-ins are always sync operations,
+ *	so there's no need bothering to make async reads 100% fail-safe.
+ *  -	The NFS rsize is smaller than PAGE_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.
+ *  -	The server is congested.
+ */
+int
+nfs_readpage(struct inode *inode, struct page *page)
+{
+	unsigned long	address;
+	int		error = -1;
+
+	dprintk("NFS: nfs_readpage %08lx\n", page_address(page));
+	set_bit(PG_locked, &page->flags);
+	address = page_address(page);
+	atomic_inc(&page->count);
+	if (!IS_SWAPFILE(inode) && !PageError(page)
+	 && NFS_SERVER(inode)->rsize >= PAGE_SIZE)
+		error = nfs_readpage_async(inode, page);
+	if (error < 0)		/* couldn't enqueue */
+		error = nfs_readpage_sync(inode, page);
+	if (error < 0 && IS_SWAPFILE(inode))
+		printk("Aiee.. nfs swap-in of page failed!\n");
+	free_page(address);
+	return error;
+}