1/*
2 * fs/logfs/file.c	- prepare_write, commit_write and friends
3 *
4 * As should be obvious for Linux kernel code, license is GPLv2
5 *
6 * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
7 */
8#include "logfs.h"
9#include <linux/sched.h>
10#include <linux/writeback.h>
11
12static int logfs_write_begin(struct file *file, struct address_space *mapping,
13		loff_t pos, unsigned len, unsigned flags,
14		struct page **pagep, void **fsdata)
15{
16	struct inode *inode = mapping->host;
17	struct page *page;
18	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
19
20	page = grab_cache_page_write_begin(mapping, index, flags);
21	if (!page)
22		return -ENOMEM;
23	*pagep = page;
24
25	if ((len == PAGE_CACHE_SIZE) || PageUptodate(page))
26		return 0;
27	if ((pos & PAGE_CACHE_MASK) >= i_size_read(inode)) {
28		unsigned start = pos & (PAGE_CACHE_SIZE - 1);
29		unsigned end = start + len;
30
31		/* Reading beyond i_size is simple: memset to zero */
32		zero_user_segments(page, 0, start, end, PAGE_CACHE_SIZE);
33		return 0;
34	}
35	return logfs_readpage_nolock(page);
36}
37
38static int logfs_write_end(struct file *file, struct address_space *mapping,
39		loff_t pos, unsigned len, unsigned copied, struct page *page,
40		void *fsdata)
41{
42	struct inode *inode = mapping->host;
43	pgoff_t index = page->index;
44	unsigned start = pos & (PAGE_CACHE_SIZE - 1);
45	unsigned end = start + copied;
46	int ret = 0;
47
48	BUG_ON(PAGE_CACHE_SIZE != inode->i_sb->s_blocksize);
49	BUG_ON(page->index > I3_BLOCKS);
50
51	if (copied < len) {
52		/*
53		 * Short write of a non-initialized paged.  Just tell userspace
54		 * to retry the entire page.
55		 */
56		if (!PageUptodate(page)) {
57			copied = 0;
58			goto out;
59		}
60	}
61	if (copied == 0)
62		goto out;
63
64	if (i_size_read(inode) < (index << PAGE_CACHE_SHIFT) + end) {
65		i_size_write(inode, (index << PAGE_CACHE_SHIFT) + end);
66		mark_inode_dirty_sync(inode);
67	}
68
69	SetPageUptodate(page);
70	if (!PageDirty(page)) {
71		if (!get_page_reserve(inode, page))
72			__set_page_dirty_nobuffers(page);
73		else
74			ret = logfs_write_buf(inode, page, WF_LOCK);
75	}
76out:
77	unlock_page(page);
78	page_cache_release(page);
79	return ret ? ret : copied;
80}
81
82int logfs_readpage(struct file *file, struct page *page)
83{
84	int ret;
85
86	ret = logfs_readpage_nolock(page);
87	unlock_page(page);
88	return ret;
89}
90
91/* Clear the page's dirty flag in the radix tree. */
92/* TODO: mucking with PageWriteback is silly.  Add a generic function to clear
93 * the dirty bit from the radix tree for filesystems that don't have to wait
94 * for page writeback to finish (i.e. any compressing filesystem).
95 */
96static void clear_radix_tree_dirty(struct page *page)
97{
98	BUG_ON(PagePrivate(page) || page->private);
99	set_page_writeback(page);
100	end_page_writeback(page);
101}
102
103static int __logfs_writepage(struct page *page)
104{
105	struct inode *inode = page->mapping->host;
106	int err;
107
108	err = logfs_write_buf(inode, page, WF_LOCK);
109	if (err)
110		set_page_dirty(page);
111	else
112		clear_radix_tree_dirty(page);
113	unlock_page(page);
114	return err;
115}
116
117static int logfs_writepage(struct page *page, struct writeback_control *wbc)
118{
119	struct inode *inode = page->mapping->host;
120	loff_t i_size = i_size_read(inode);
121	pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
122	unsigned offset;
123	u64 bix;
124	level_t level;
125
126	log_file("logfs_writepage(%lx, %lx, %p)\n", inode->i_ino, page->index,
127			page);
128
129	logfs_unpack_index(page->index, &bix, &level);
130
131	/* Indirect blocks are never truncated */
132	if (level != 0)
133		return __logfs_writepage(page);
134
135	/*
136	 * TODO: everything below is a near-verbatim copy of nobh_writepage().
137	 * The relevant bits should be factored out after logfs is merged.
138	 */
139
140	/* Is the page fully inside i_size? */
141	if (bix < end_index)
142		return __logfs_writepage(page);
143
144	 /* Is the page fully outside i_size? (truncate in progress) */
145	offset = i_size & (PAGE_CACHE_SIZE-1);
146	if (bix > end_index || offset == 0) {
147		unlock_page(page);
148		return 0; /* don't care */
149	}
150
151	/*
152	 * The page straddles i_size.  It must be zeroed out on each and every
153	 * writepage invokation because it may be mmapped.  "A file is mapped
154	 * in multiples of the page size.  For a file that is not a multiple of
155	 * the  page size, the remaining memory is zeroed when mapped, and
156	 * writes to that region are not written out to the file."
157	 */
158	zero_user_segment(page, offset, PAGE_CACHE_SIZE);
159	return __logfs_writepage(page);
160}
161
162static void logfs_invalidatepage(struct page *page, unsigned long offset)
163{
164	struct logfs_block *block = logfs_block(page);
165
166	if (block->reserved_bytes) {
167		struct super_block *sb = page->mapping->host->i_sb;
168		struct logfs_super *super = logfs_super(sb);
169
170		super->s_dirty_pages -= block->reserved_bytes;
171		block->ops->free_block(sb, block);
172		BUG_ON(bitmap_weight(block->alias_map, LOGFS_BLOCK_FACTOR));
173	} else
174		move_page_to_btree(page);
175	BUG_ON(PagePrivate(page) || page->private);
176}
177
178static int logfs_releasepage(struct page *page, gfp_t only_xfs_uses_this)
179{
180	return 0; /* None of these are easy to release */
181}
182
183
184long logfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
185{
186	struct inode *inode = file->f_path.dentry->d_inode;
187	struct logfs_inode *li = logfs_inode(inode);
188	unsigned int oldflags, flags;
189	int err;
190
191	switch (cmd) {
192	case FS_IOC_GETFLAGS:
193		flags = li->li_flags & LOGFS_FL_USER_VISIBLE;
194		return put_user(flags, (int __user *)arg);
195	case FS_IOC_SETFLAGS:
196		if (IS_RDONLY(inode))
197			return -EROFS;
198
199		if (!is_owner_or_cap(inode))
200			return -EACCES;
201
202		err = get_user(flags, (int __user *)arg);
203		if (err)
204			return err;
205
206		mutex_lock(&inode->i_mutex);
207		oldflags = li->li_flags;
208		flags &= LOGFS_FL_USER_MODIFIABLE;
209		flags |= oldflags & ~LOGFS_FL_USER_MODIFIABLE;
210		li->li_flags = flags;
211		mutex_unlock(&inode->i_mutex);
212
213		inode->i_ctime = CURRENT_TIME;
214		mark_inode_dirty_sync(inode);
215		return 0;
216
217	default:
218		return -ENOTTY;
219	}
220}
221
222int logfs_fsync(struct file *file, int datasync)
223{
224	struct super_block *sb = file->f_mapping->host->i_sb;
225
226	logfs_write_anchor(sb);
227	return 0;
228}
229
230static int logfs_setattr(struct dentry *dentry, struct iattr *attr)
231{
232	struct inode *inode = dentry->d_inode;
233	int err = 0;
234
235	err = inode_change_ok(inode, attr);
236	if (err)
237		return err;
238
239	if (attr->ia_valid & ATTR_SIZE) {
240		err = logfs_truncate(inode, attr->ia_size);
241		if (err)
242			return err;
243	}
244
245	setattr_copy(inode, attr);
246	mark_inode_dirty(inode);
247	return 0;
248}
249
250const struct inode_operations logfs_reg_iops = {
251	.setattr	= logfs_setattr,
252};
253
254const struct file_operations logfs_reg_fops = {
255	.aio_read	= generic_file_aio_read,
256	.aio_write	= generic_file_aio_write,
257	.fsync		= logfs_fsync,
258	.unlocked_ioctl	= logfs_ioctl,
259	.llseek		= generic_file_llseek,
260	.mmap		= generic_file_readonly_mmap,
261	.open		= generic_file_open,
262	.read		= do_sync_read,
263	.write		= do_sync_write,
264};
265
266const struct address_space_operations logfs_reg_aops = {
267	.invalidatepage	= logfs_invalidatepage,
268	.readpage	= logfs_readpage,
269	.releasepage	= logfs_releasepage,
270	.set_page_dirty	= __set_page_dirty_nobuffers,
271	.writepage	= logfs_writepage,
272	.writepages	= generic_writepages,
273	.write_begin	= logfs_write_begin,
274	.write_end	= logfs_write_end,
275};
276