4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
22 * Copyright (c) 2011, Lawrence Livermore National Security, LLC.
26 #include <sys/zfs_vfsops.h>
27 #include <sys/zfs_vnops.h>
28 #include <sys/zfs_znode.h>
33 zpl_readdir(struct file *filp, void *dirent, filldir_t filldir)
35 struct dentry *dentry = filp->f_path.dentry;
39 cr = (cred_t *)get_current_cred();
40 error = -zfs_readdir(dentry->d_inode, dirent, filldir,
43 ASSERT3S(error, <=, 0);
48 ZPL_FSYNC_PROTO(zpl_fsync, filp, unused_dentry, datasync)
53 cr = (cred_t *)get_current_cred();
54 error = -zfs_fsync(filp->f_path.dentry->d_inode, datasync, cr);
56 ASSERT3S(error, <=, 0);
62 zpl_read_common(struct inode *ip, const char *buf, size_t len, loff_t pos,
63 uio_seg_t segment, int flags, cred_t *cr)
69 iov.iov_base = (void *)buf;
75 uio.uio_loffset = pos;
76 uio.uio_limit = MAXOFFSET_T;
77 uio.uio_segflg = segment;
79 error = -zfs_read(ip, &uio, flags, cr);
83 return (len - uio.uio_resid);
87 zpl_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
92 cr = (cred_t *)get_current_cred();
93 read = zpl_read_common(filp->f_mapping->host, buf, len, *ppos,
94 UIO_USERSPACE, filp->f_flags, cr);
105 zpl_write_common(struct inode *ip, const char *buf, size_t len, loff_t pos,
106 uio_seg_t segment, int flags, cred_t *cr)
112 iov.iov_base = (void *)buf;
118 uio.uio_loffset = pos;
119 uio.uio_limit = MAXOFFSET_T;
120 uio.uio_segflg = segment;
122 error = -zfs_write(ip, &uio, flags, cr);
126 return (len - uio.uio_resid);
130 zpl_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
135 cr = (cred_t *)get_current_cred();
136 wrote = zpl_write_common(filp->f_mapping->host, buf, len, *ppos,
137 UIO_USERSPACE, filp->f_flags, cr);
148 * It's worth taking a moment to describe how mmap is implemented
149 * for zfs because it differs considerably from other Linux filesystems.
150 * However, this issue is handled the same way under OpenSolaris.
152 * The issue is that by design zfs bypasses the Linux page cache and
153 * leaves all caching up to the ARC. This has been shown to work
154 * well for the common read(2)/write(2) case. However, mmap(2)
155 * is problem because it relies on being tightly integrated with the
156 * page cache. To handle this we cache mmap'ed files twice, once in
157 * the ARC and a second time in the page cache. The code is careful
158 * to keep both copies synchronized.
160 * When a file with an mmap'ed region is written to using write(2)
161 * both the data in the ARC and existing pages in the page cache
162 * are updated. For a read(2) data will be read first from the page
163 * cache then the ARC if needed. Neither a write(2) or read(2) will
164 * will ever result in new pages being added to the page cache.
166 * New pages are added to the page cache only via .readpage() which
167 * is called when the vfs needs to read a page off disk to back the
168 * virtual memory region. These pages may be modified without
169 * notifying the ARC and will be written out periodically via
170 * .writepage(). This will occur due to either a sync or the usual
171 * page aging behavior. Note because a read(2) of a mmap'ed file
172 * will always check the page cache first even when the ARC is out
173 * of date correct data will still be returned.
175 * While this implementation ensures correct behavior it does have
176 * have some drawbacks. The most obvious of which is that it
177 * increases the required memory footprint when access mmap'ed
178 * files. It also adds additional complexity to the code keeping
179 * both caches synchronized.
181 * Longer term it may be possible to cleanly resolve this wart by
182 * mapping page cache pages directly on to the ARC buffers. The
183 * Linux address space operations are flexible enough to allow
184 * selection of which pages back a particular index. The trick
185 * would be working out the details of which subsystem is in
186 * charge, the ARC, the page cache, or both. It may also prove
187 * helpful to move the ARC buffers to a scatter-gather lists
188 * rather than a vmalloc'ed region.
191 zpl_mmap(struct file *filp, struct vm_area_struct *vma)
193 znode_t *zp = ITOZ(filp->f_mapping->host);
196 error = generic_file_mmap(filp, vma);
200 mutex_enter(&zp->z_lock);
202 mutex_exit(&zp->z_lock);
208 * Populate a page with data for the Linux page cache. This function is
209 * only used to support mmap(2). There will be an identical copy of the
210 * data in the ARC which is kept up to date via .write() and .writepage().
212 * Current this function relies on zpl_read_common() and the O_DIRECT
213 * flag to read in a page. This works but the more correct way is to
214 * update zfs_fillpage() to be Linux friendly and use that interface.
217 zpl_readpage(struct file *filp, struct page *pp)
226 ASSERT(PageLocked(pp));
227 ip = pp->mapping->host;
228 off = page_offset(pp);
229 i_size = i_size_read(ip);
230 ASSERT3S(off, <, i_size);
232 cr = (cred_t *)get_current_cred();
233 len = MIN(PAGE_CACHE_SIZE, i_size - off);
237 /* O_DIRECT is passed to bypass the page cache and avoid deadlock. */
238 wrote = zpl_read_common(ip, pb, len, off, UIO_SYSSPACE, O_DIRECT, cr);
242 if (!error && (len < PAGE_CACHE_SIZE))
243 memset(pb + len, 0, PAGE_CACHE_SIZE - len);
250 ClearPageUptodate(pp);
254 flush_dcache_page(pp);
263 * Write out dirty pages to the ARC, this function is only required to
264 * support mmap(2). Mapped pages may be dirtied by memory operations
265 * which never call .write(). These dirty pages are kept in sync with
266 * the ARC buffers via this hook.
268 * Currently this function relies on zpl_write_common() and the O_DIRECT
269 * flag to push out the page. This works but the more correct way is
270 * to update zfs_putapage() to be Linux friendly and use that interface.
273 zpl_writepage(struct page *pp, struct writeback_control *wbc)
282 ASSERT(PageLocked(pp));
283 ip = pp->mapping->host;
284 off = page_offset(pp);
285 i_size = i_size_read(ip);
287 cr = (cred_t *)get_current_cred();
288 len = MIN(PAGE_CACHE_SIZE, i_size - off);
292 /* O_DIRECT is passed to bypass the page cache and avoid deadlock. */
293 read = zpl_write_common(ip, pb, len, off, UIO_SYSSPACE, O_DIRECT, cr);
302 ClearPageUptodate(pp);
313 const struct address_space_operations zpl_address_space_operations = {
314 .readpage = zpl_readpage,
315 .writepage = zpl_writepage,
318 const struct file_operations zpl_file_operations = {
319 .open = generic_file_open,
320 .llseek = generic_file_llseek,
323 .readdir = zpl_readdir,
328 const struct file_operations zpl_dir_file_operations = {
329 .llseek = generic_file_llseek,
330 .read = generic_read_dir,
331 .readdir = zpl_readdir,