patch-2.4.22 linux-2.4.22/fs/nfs/direct.c

• Lines: 383
• Date: 2003-08-25 04:44:43.000000000 -0700
• Orig file: linux-2.4.21/fs/nfs/direct.c
• Orig date: 1969-12-31 16:00:00.000000000 -0800

diff -urN linux-2.4.21/fs/nfs/direct.c linux-2.4.22/fs/nfs/direct.c
@@ -0,0 +1,382 @@
+/*
+ * linux/fs/nfs/direct.c
+ *
+ * High-performance direct I/O for the NFS client
+ *
+ * When an application requests uncached I/O, all read and write requests
+ * are made directly to the server; data stored or fetched via these
+ * requests is not cached in the Linux page cache.  The client does not
+ * correct unaligned requests from applications.  All requested bytes are
+ * held on permanent storage before a direct write system call returns to
+ * an application.  Applications that manage their own data caching, such
+ * as databases, make very good use of direct I/O on local file systems.
+ *
+ * Solaris implements an uncached I/O facility called directio() that
+ * is used for backups and sequential I/O to very large files.  Solaris
+ * also supports uncaching whole NFS partitions with "-o forcedirectio,"
+ * an undocumented mount option.
+ *
+ * Note that I/O to read in executables (e.g. kernel_read) cannot use
+ * direct (kiobuf) reads because there is no vma backing the passed-in
+ * data buffer.
+ *
+ * Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust.
+ *
+ * Initial implementation:	12/2001 by Chuck Lever <cel@netapp.com>
+ *
+ * TODO:
+ *
+ * 1.  Use concurrent asynchronous network requests rather than
+ *     serialized synchronous network requests for normal (non-sync)
+ *     direct I/O.
+ */
+
+#include <linux/config.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/file.h>
+#include <linux/errno.h>
+#include <linux/nfs_fs.h>
+#include <linux/smp_lock.h>
+#include <linux/sunrpc/clnt.h>
+#include <linux/iobuf.h>
+
+#include <asm/system.h>
+#include <asm/uaccess.h>
+
+#define NFSDBG_FACILITY		(NFSDBG_PAGECACHE | NFSDBG_VFS)
+#define VERF_SIZE		(2 * sizeof(__u32))
+
+static inline int
+nfs_direct_read_rpc(struct file *file, struct nfs_readargs *arg)
+{
+	int result;
+	struct inode * inode = file->f_dentry->d_inode;
+	struct nfs_fattr fattr;
+        struct rpc_message msg;
+        struct nfs_readres res = { &fattr, arg->count, 0 };
+
+#ifdef CONFIG_NFS_V3
+	msg.rpc_proc = (NFS_PROTO(inode)->version == 3) ?
+						NFS3PROC_READ : NFSPROC_READ;
+#else
+	msg.rpc_proc = NFSPROC_READ;
+#endif
+	msg.rpc_argp = arg;
+        msg.rpc_resp = &res;
+
+	lock_kernel();
+        msg.rpc_cred = nfs_file_cred(file);
+        fattr.valid = 0;
+        result = rpc_call_sync(NFS_CLIENT(inode), &msg, 0);
+	nfs_refresh_inode(inode, &fattr);
+	unlock_kernel();
+
+	return result;
+}
+
+static inline int
+nfs_direct_write_rpc(struct file *file, struct nfs_writeargs *arg,
+	struct nfs_writeverf *verf)
+{
+	int result;
+	struct inode *inode = file->f_dentry->d_inode;
+	struct nfs_fattr fattr;
+        struct rpc_message msg;
+        struct nfs_writeres res = { &fattr, verf, 0 };
+
+#ifdef CONFIG_NFS_V3
+	msg.rpc_proc = (NFS_PROTO(inode)->version == 3) ?
+						NFS3PROC_WRITE : NFSPROC_WRITE;
+#else
+	msg.rpc_proc = NFSPROC_WRITE;
+#endif
+	msg.rpc_argp = arg;
+        msg.rpc_resp = &res;
+
+	lock_kernel();
+	msg.rpc_cred = get_rpccred(nfs_file_cred(file));
+	fattr.valid = 0;
+        result = rpc_call_sync(NFS_CLIENT(inode), &msg, 0);
+	nfs_write_attributes(inode, &fattr);
+	put_rpccred(msg.rpc_cred);
+	unlock_kernel();
+
+#ifdef CONFIG_NFS_V3
+	if (NFS_PROTO(inode)->version == 3) {
+		if (result > 0) {
+			if ((arg->stable == NFS_FILE_SYNC) &&
+			    (verf->committed != NFS_FILE_SYNC)) {
+				printk(KERN_ERR
+				"%s: server didn't sync stable write request\n",
+				__FUNCTION__);
+				return -EIO;
+			}
+
+			if (result != arg->count) {
+				printk(KERN_INFO
+					"%s: short write, count=%u, result=%d\n",
+					__FUNCTION__, arg->count, result);
+			}
+		}
+		return result;
+	} else {
+#endif
+        	verf->committed = NFS_FILE_SYNC; /* NFSv2 always syncs data */
+		if (result == 0)
+			return arg->count;
+		return result;
+#ifdef CONFIG_NFS_V3
+	}
+#endif
+}
+
+#ifdef CONFIG_NFS_V3
+static inline int
+nfs_direct_commit_rpc(struct inode *inode, loff_t offset, size_t count,
+	struct nfs_writeverf *verf)
+{
+	int result;
+	struct nfs_fattr fattr;
+	struct nfs_writeargs	arg = { NFS_FH(inode), offset, count, 0, 0,
+					NULL };
+	struct nfs_writeres	res = { &fattr, verf, 0 };
+	struct rpc_message	msg = { NFS3PROC_COMMIT, &arg, &res, NULL };
+
+	fattr.valid = 0;
+
+	lock_kernel();
+	result = rpc_call_sync(NFS_CLIENT(inode), &msg, 0);
+	nfs_write_attributes(inode, &fattr);
+	unlock_kernel();
+
+	return result;
+}
+#else
+static inline int
+nfs_direct_commit_rpc(struct inode *inode, loff_t offset, size_t count,
+	struct nfs_writeverf *verf)
+{
+	return 0;
+}
+#endif
+
+/*
+ * Walk through the iobuf and create an iovec for each "rsize" bytes.
+ */
+static int
+nfs_direct_read(struct file *file, struct kiobuf *iobuf, loff_t offset,
+	size_t count)
+{
+	int curpage, total;
+	int result = 0;
+	struct inode *inode = file->f_dentry->d_inode;
+	int rsize = NFS_SERVER(inode)->rsize;
+	struct page *pages[NFS_READ_MAXIOV];
+	struct nfs_readargs args = { NFS_FH(inode), offset, 0, iobuf->offset,
+				     pages };
+
+	total = 0;
+	curpage = 0;
+        while (count) {
+		int len, request;
+		struct page **dest = pages;
+
+                request = count;
+                if (count > rsize)
+                        request = rsize;
+		args.count = request;
+		args.offset = offset;
+		args.pgbase = (iobuf->offset + total) & ~PAGE_MASK;
+		len = PAGE_SIZE - args.pgbase;
+
+		do {
+			struct page *page = iobuf->maplist[curpage];
+
+			if (curpage >= iobuf->nr_pages || !page) {
+				result = -EFAULT;
+				goto out_err;
+			}
+
+			*dest++ = page;
+			/* zero after the first iov */
+			if (request < len)
+				break;
+			request -= len;
+			len = PAGE_SIZE;
+			curpage++;
+		} while (request != 0);
+
+                result = nfs_direct_read_rpc(file, &args);
+
+                if (result < 0)
+                        break;
+
+                total += result;
+                if (result < args.count)   /* NFSv2ism */
+                        break;
+                count -= result;
+                offset += result;
+        };
+out_err:
+	if (!total)
+		return result;
+	return total;
+}
+
+/*
+ * Walk through the iobuf and create an iovec for each "wsize" bytes.
+ * If only one network write is necessary, or if the O_SYNC flag or
+ * 'sync' mount option are present, or if this is a V2 inode, use
+ * FILE_SYNC.  Otherwise, use UNSTABLE and finish with a COMMIT.
+ *
+ * The mechanics of this function are much the same as nfs_direct_read,
+ * with the added complexity of committing unstable writes.
+ */
+static int
+nfs_direct_write(struct file *file, struct kiobuf *iobuf,
+	loff_t offset, size_t count)
+{
+	int curpage, total;
+	int need_commit = 0;
+	int result = 0;
+	loff_t save_offset = offset;
+	struct inode *inode = file->f_dentry->d_inode;
+	int wsize = NFS_SERVER(inode)->wsize;
+	struct nfs_writeverf first_verf, ret_verf;
+	struct page *pages[NFS_WRITE_MAXIOV];
+        struct nfs_writeargs args = { NFS_FH(inode), 0, 0, NFS_FILE_SYNC, 0,
+				pages };
+
+#ifdef CONFIG_NFS_V3
+	if ((NFS_PROTO(inode)->version == 3) && (count > wsize) &&
+							(!IS_SYNC(inode)))
+		args.stable = NFS_UNSTABLE;
+#endif
+
+retry:
+	total = 0;
+	curpage = 0;
+        while (count) {
+		int len, request;
+		struct page **dest = pages;
+
+                request = count;
+                if (count > wsize)
+                        request = wsize;
+		args.count = request;
+		args.offset = offset;
+		args.pgbase = (iobuf->offset + total) & ~PAGE_MASK;
+		len = PAGE_SIZE - args.pgbase;
+
+		do {
+			struct page *page = iobuf->maplist[curpage];
+
+			if (curpage >= iobuf->nr_pages || !page) {
+				result = -EFAULT;
+				goto out_err;
+			}
+
+			*dest++ = page;
+			/* zero after the first iov */
+			if (request < len)
+				break;
+			request -= len;
+			len = PAGE_SIZE;
+			curpage++;
+		} while (request != 0);
+
+                result = nfs_direct_write_rpc(file, &args, &ret_verf);
+
+                if (result < 0)
+                        break;
+
+		if (!total)
+			memcpy(&first_verf.verifier, &ret_verf.verifier,
+								VERF_SIZE);
+		if (ret_verf.committed != NFS_FILE_SYNC) {
+			need_commit = 1;
+			if (memcmp(&first_verf.verifier, &ret_verf.verifier,
+								VERF_SIZE))
+				goto print_retry;
+		}
+
+                total += result;
+                count -= result;
+                offset += result;
+        };
+
+out_err:
+	/*
+	 * Commit data written so far, even in the event of an error
+	 */
+	if (need_commit) {
+		if (nfs_direct_commit_rpc(inode, save_offset,
+					iobuf->length - count, &ret_verf))
+			goto print_retry;
+		if (memcmp(&first_verf.verifier, &ret_verf.verifier,
+								VERF_SIZE))
+			goto print_retry;
+	}
+
+	if (!total)
+		return result;
+	return total;
+
+print_retry:
+	printk(KERN_INFO "%s: detected server restart; retrying with FILE_SYNC\n",
+			__FUNCTION__);
+	args.stable = NFS_FILE_SYNC;
+	offset = save_offset;
+	count = iobuf->length;
+	goto retry;
+}
+
+/*
+ * Read or write data, moving the data directly to/from the
+ * application's buffer without caching in the page cache.
+ *
+ * Rules for direct I/O
+ *
+ * 1.  block size = 512 bytes or more
+ * 2.  file byte offset is block aligned
+ * 3.  byte count is a multiple of block size
+ * 4.  user buffer is not aligned
+ * 5.  user buffer is faulted in and pinned
+ *
+ * These are verified before we get here.
+ */
+int
+nfs_direct_IO(int rw, struct file *file, struct kiobuf *iobuf,
+	unsigned long blocknr, int blocksize)
+{
+	int result = -EINVAL;
+	size_t count = iobuf->length;
+	struct dentry *dentry = file->f_dentry;
+	struct inode *inode = dentry->d_inode;
+	loff_t offset = blocknr << inode->i_blkbits;
+
+	switch (rw) {
+	case READ:
+		dfprintk(VFS,
+			"NFS: direct_IO(READ) (%s/%s) off/cnt(%Lu/%d)\n",
+				dentry->d_parent->d_name.name,
+					dentry->d_name.name, offset, count);
+
+		result = nfs_direct_read(file, iobuf, offset, count);
+		break;
+	case WRITE:
+		dfprintk(VFS,
+			"NFS: direct_IO(WRITE) (%s/%s) off/cnt(%Lu/%d)\n",
+				dentry->d_parent->d_name.name,
+					dentry->d_name.name, offset, count);
+
+		result = nfs_direct_write(file, iobuf, offset, count);
+		break;
+	default:
+		break;
+	}
+
+	dfprintk(VFS, "NFS: direct_IO result = %d\n", result);
+	return result;
+}