1 files changed, 333 insertions, 0 deletions
diff --git a/module/zfs/zpl_file.c b/module/zfs/zpl_file.c
new file mode 100644
index 000000000..ed6704bb2
--- /dev/null
+++ b/module/zfs/zpl_file.c
@@ -0,0 +1,333 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2011, Lawrence Livermore National Security, LLC.
+ */
+
+
+#include <sys/zfs_vfsops.h>
+#include <sys/zfs_vnops.h>
+#include <sys/zfs_znode.h>
+#include <sys/zpl.h>
+
+
+static int
+zpl_readdir(struct file *filp, void *dirent, filldir_t filldir)
+{
+	struct dentry *dentry = filp->f_path.dentry;
+	cred_t *cr;
+	int error;
+
+	cr = (cred_t *)get_current_cred();
+	error = -zfs_readdir(dentry->d_inode, dirent, filldir,
+	    &filp->f_pos, cr);
+	put_cred(cr);
+	ASSERT3S(error, <=, 0);
+
+	return (error);
+}
+
+ZPL_FSYNC_PROTO(zpl_fsync, filp, unused_dentry, datasync)
+{
+	cred_t *cr;
+	int error;
+
+	cr = (cred_t *)get_current_cred();
+	error = -zfs_fsync(filp->f_path.dentry->d_inode, datasync, cr);
+	put_cred(cr);
+	ASSERT3S(error, <=, 0);
+
+	return (error);
+}
+
+ssize_t
+zpl_read_common(struct inode *ip, const char *buf, size_t len, loff_t pos,
+     uio_seg_t segment, int flags, cred_t *cr)
+{
+	int error;
+	struct iovec iov;
+	uio_t uio;
+
+	iov.iov_base = (void *)buf;
+	iov.iov_len = len;
+
+	uio.uio_iov = &iov;
+	uio.uio_resid = len;
+	uio.uio_iovcnt = 1;
+	uio.uio_loffset = pos;
+	uio.uio_limit = MAXOFFSET_T;
+	uio.uio_segflg = segment;
+
+	error = -zfs_read(ip, &uio, flags, cr);
+	if (error < 0)
+		return (error);
+
+	return (len - uio.uio_resid);
+}
+
+static ssize_t
+zpl_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
+{
+	cred_t *cr;
+	ssize_t read;
+
+	cr = (cred_t *)get_current_cred();
+	read = zpl_read_common(filp->f_mapping->host, buf, len, *ppos,
+	    UIO_USERSPACE, filp->f_flags, cr);
+	put_cred(cr);
+
+	if (read < 0)
+		return (read);
+
+	*ppos += read;
+	return (read);
+}
+
+ssize_t
+zpl_write_common(struct inode *ip, const char *buf, size_t len, loff_t pos,
+    uio_seg_t segment, int flags, cred_t *cr)
+{
+	int error;
+	struct iovec iov;
+	uio_t uio;
+
+	iov.iov_base = (void *)buf;
+	iov.iov_len = len;
+
+	uio.uio_iov = &iov;
+	uio.uio_resid = len,
+	uio.uio_iovcnt = 1;
+	uio.uio_loffset = pos;
+	uio.uio_limit = MAXOFFSET_T;
+	uio.uio_segflg = segment;
+
+	error = -zfs_write(ip, &uio, flags, cr);
+	if (error < 0)
+		return (error);
+
+	return (len - uio.uio_resid);
+}
+
+static ssize_t
+zpl_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
+{
+	cred_t *cr;
+	ssize_t wrote;
+
+	cr = (cred_t *)get_current_cred();
+	wrote = zpl_write_common(filp->f_mapping->host, buf, len, *ppos,
+	    UIO_USERSPACE, filp->f_flags, cr);
+	put_cred(cr);
+
+	if (wrote < 0)
+		return (wrote);
+
+	*ppos += wrote;
+	return (wrote);
+}
+
+/*
+ * It's worth taking a moment to describe how mmap is implemented
+ * for zfs because it differs considerably from other Linux filesystems.
+ * However, this issue is handled the same way under OpenSolaris.
+ *
+ * The issue is that by design zfs bypasses the Linux page cache and
+ * leaves all caching up to the ARC.  This has been shown to work
+ * well for the common read(2)/write(2) case.  However, mmap(2)
+ * is problem because it relies on being tightly integrated with the
+ * page cache.  To handle this we cache mmap'ed files twice, once in
+ * the ARC and a second time in the page cache.  The code is careful
+ * to keep both copies synchronized.
+ *
+ * When a file with an mmap'ed region is written to using write(2)
+ * both the data in the ARC and existing pages in the page cache
+ * are updated.  For a read(2) data will be read first from the page
+ * cache then the ARC if needed.  Neither a write(2) or read(2) will
+ * will ever result in new pages being added to the page cache.
+ *
+ * New pages are added to the page cache only via .readpage() which
+ * is called when the vfs needs to read a page off disk to back the
+ * virtual memory region.  These pages may be modified without
+ * notifying the ARC and will be written out periodically via
+ * .writepage().  This will occur due to either a sync or the usual
+ * page aging behavior.  Note because a read(2) of a mmap'ed file
+ * will always check the page cache first even when the ARC is out
+ * of date correct data will still be returned.
+ *
+ * While this implementation ensures correct behavior it does have
+ * have some drawbacks.  The most obvious of which is that it
+ * increases the required memory footprint when access mmap'ed
+ * files.  It also adds additional complexity to the code keeping
+ * both caches synchronized.
+ *
+ * Longer term it may be possible to cleanly resolve this wart by
+ * mapping page cache pages directly on to the ARC buffers.  The
+ * Linux address space operations are flexible enough to allow
+ * selection of which pages back a particular index.  The trick
+ * would be working out the details of which subsystem is in
+ * charge, the ARC, the page cache, or both.  It may also prove
+ * helpful to move the ARC buffers to a scatter-gather lists
+ * rather than a vmalloc'ed region.
+ */
+static int
+zpl_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	znode_t *zp = ITOZ(filp->f_mapping->host);
+	int error;
+
+	error = generic_file_mmap(filp, vma);
+	if (error)
+		return (error);
+
+	mutex_enter(&zp->z_lock);
+	zp->z_is_mapped = 1;
+	mutex_exit(&zp->z_lock);
+
+	return (error);
+}
+
+/*
+ * Populate a page with data for the Linux page cache.  This function is
+ * only used to support mmap(2).  There will be an identical copy of the
+ * data in the ARC which is kept up to date via .write() and .writepage().
+ *
+ * Current this function relies on zpl_read_common() and the O_DIRECT
+ * flag to read in a page.  This works but the more correct way is to
+ * update zfs_fillpage() to be Linux friendly and use that interface.
+ */
+static int
+zpl_readpage(struct file *filp, struct page *pp)
+{
+	struct inode *ip;
+	loff_t off, i_size;
+	size_t len, wrote;
+	cred_t *cr;
+	void *pb;
+	int error = 0;
+
+	ASSERT(PageLocked(pp));
+	ip = pp->mapping->host;
+	off = page_offset(pp);
+	i_size = i_size_read(ip);
+	ASSERT3S(off, <, i_size);
+
+	cr = (cred_t *)get_current_cred();
+	len = MIN(PAGE_CACHE_SIZE, i_size - off);
+
+	pb = kmap(pp);
+
+	/* O_DIRECT is passed to bypass the page cache and avoid deadlock. */
+	wrote = zpl_read_common(ip, pb, len, off, UIO_SYSSPACE, O_DIRECT, cr);
+	if (wrote != len)
+		error = -EIO;
+
+	if (!error && (len < PAGE_CACHE_SIZE))
+		memset(pb + len, 0, PAGE_CACHE_SIZE - len);
+
+	kunmap(pp);
+	put_cred(cr);
+
+	if (error) {
+		SetPageError(pp);
+		ClearPageUptodate(pp);
+	} else {
+		ClearPageError(pp);
+		SetPageUptodate(pp);
+		flush_dcache_page(pp);
+	}
+
+	unlock_page(pp);
+
+	return (error);
+}
+
+/*
+ * Write out dirty pages to the ARC, this function is only required to
+ * support mmap(2).  Mapped pages may be dirtied by memory operations
+ * which never call .write().  These dirty pages are kept in sync with
+ * the ARC buffers via this hook.
+ *
+ * Currently this function relies on zpl_write_common() and the O_DIRECT
+ * flag to push out the page.  This works but the more correct way is
+ * to update zfs_putapage() to be Linux friendly and use that interface.
+ */
+static int
+zpl_writepage(struct page *pp, struct writeback_control *wbc)
+{
+	struct inode *ip;
+	loff_t off, i_size;
+	size_t len, read;
+	cred_t *cr;
+	void *pb;
+	int error = 0;
+
+	ASSERT(PageLocked(pp));
+	ip = pp->mapping->host;
+	off = page_offset(pp);
+	i_size = i_size_read(ip);
+
+	cr = (cred_t *)get_current_cred();
+	len = MIN(PAGE_CACHE_SIZE, i_size - off);
+
+	pb = kmap(pp);
+
+	/* O_DIRECT is passed to bypass the page cache and avoid deadlock. */
+	read = zpl_write_common(ip, pb, len, off, UIO_SYSSPACE, O_DIRECT, cr);
+	if (read != len)
+		error = -EIO;
+
+	kunmap(pp);
+	put_cred(cr);
+
+	if (error) {
+		SetPageError(pp);
+		ClearPageUptodate(pp);
+	} else {
+		ClearPageError(pp);
+		SetPageUptodate(pp);
+	}
+
+	unlock_page(pp);
+
+	return (error);
+}
+
+const struct address_space_operations zpl_address_space_operations = {
+	.readpage	= zpl_readpage,
+	.writepage	= zpl_writepage,
+};
+
+const struct file_operations zpl_file_operations = {
+	.open		= generic_file_open,
+	.llseek		= generic_file_llseek,
+	.read		= zpl_read,
+	.write		= zpl_write,
+	.readdir	= zpl_readdir,
+	.mmap		= zpl_mmap,
+	.fsync		= zpl_fsync,
+};
+
+const struct file_operations zpl_dir_file_operations = {
+	.llseek		= generic_file_llseek,
+	.read		= generic_read_dir,
+	.readdir	= zpl_readdir,
+	.fsync		= zpl_fsync,
+};