xref: /openbmc/linux/fs/ext4/page-io.c (revision 5bd8e16d) 
1 /*
2  * linux/fs/ext4/page-io.c
3  *
4  * This contains the new page_io functions for ext4
5  *
6  * Written by Theodore Ts'o, 2010.
7  */
8 
9 #include <linux/fs.h>
10 #include <linux/time.h>
11 #include <linux/jbd2.h>
12 #include <linux/highuid.h>
13 #include <linux/pagemap.h>
14 #include <linux/quotaops.h>
15 #include <linux/string.h>
16 #include <linux/buffer_head.h>
17 #include <linux/writeback.h>
18 #include <linux/pagevec.h>
19 #include <linux/mpage.h>
20 #include <linux/namei.h>
21 #include <linux/aio.h>
22 #include <linux/uio.h>
23 #include <linux/bio.h>
24 #include <linux/workqueue.h>
25 #include <linux/kernel.h>
26 #include <linux/slab.h>
27 #include <linux/mm.h>
28 #include <linux/ratelimit.h>
29 
30 #include "ext4_jbd2.h"
31 #include "xattr.h"
32 #include "acl.h"
33 
34 static struct kmem_cache *io_end_cachep;
35 
36 int __init ext4_init_pageio(void)
37 {
38 	io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
39 	if (io_end_cachep == NULL)
40 		return -ENOMEM;
41 	return 0;
42 }
43 
44 void ext4_exit_pageio(void)
45 {
46 	kmem_cache_destroy(io_end_cachep);
47 }
48 
49 /*
50  * Print an buffer I/O error compatible with the fs/buffer.c.  This
51  * provides compatibility with dmesg scrapers that look for a specific
52  * buffer I/O error message.  We really need a unified error reporting
53  * structure to userspace ala Digital Unix's uerf system, but it's
54  * probably not going to happen in my lifetime, due to LKML politics...
55  */
56 static void buffer_io_error(struct buffer_head *bh)
57 {
58 	char b[BDEVNAME_SIZE];
59 	printk_ratelimited(KERN_ERR "Buffer I/O error on device %s, logical block %llu\n",
60 			bdevname(bh->b_bdev, b),
61 			(unsigned long long)bh->b_blocknr);
62 }
63 
64 static void ext4_finish_bio(struct bio *bio)
65 {
66 	int i;
67 	int error = !test_bit(BIO_UPTODATE, &bio->bi_flags);
68 
69 	for (i = 0; i < bio->bi_vcnt; i++) {
70 		struct bio_vec *bvec = &bio->bi_io_vec[i];
71 		struct page *page = bvec->bv_page;
72 		struct buffer_head *bh, *head;
73 		unsigned bio_start = bvec->bv_offset;
74 		unsigned bio_end = bio_start + bvec->bv_len;
75 		unsigned under_io = 0;
76 		unsigned long flags;
77 
78 		if (!page)
79 			continue;
80 
81 		if (error) {
82 			SetPageError(page);
83 			set_bit(AS_EIO, &page->mapping->flags);
84 		}
85 		bh = head = page_buffers(page);
86 		/*
87 		 * We check all buffers in the page under BH_Uptodate_Lock
88 		 * to avoid races with other end io clearing async_write flags
89 		 */
90 		local_irq_save(flags);
91 		bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
92 		do {
93 			if (bh_offset(bh) < bio_start ||
94 			    bh_offset(bh) + bh->b_size > bio_end) {
95 				if (buffer_async_write(bh))
96 					under_io++;
97 				continue;
98 			}
99 			clear_buffer_async_write(bh);
100 			if (error)
101 				buffer_io_error(bh);
102 		} while ((bh = bh->b_this_page) != head);
103 		bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
104 		local_irq_restore(flags);
105 		if (!under_io)
106 			end_page_writeback(page);
107 	}
108 }
109 
110 static void ext4_release_io_end(ext4_io_end_t *io_end)
111 {
112 	struct bio *bio, *next_bio;
113 
114 	BUG_ON(!list_empty(&io_end->list));
115 	BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
116 	WARN_ON(io_end->handle);
117 
118 	if (atomic_dec_and_test(&EXT4_I(io_end->inode)->i_ioend_count))
119 		wake_up_all(ext4_ioend_wq(io_end->inode));
120 
121 	for (bio = io_end->bio; bio; bio = next_bio) {
122 		next_bio = bio->bi_private;
123 		ext4_finish_bio(bio);
124 		bio_put(bio);
125 	}
126 	kmem_cache_free(io_end_cachep, io_end);
127 }
128 
129 static void ext4_clear_io_unwritten_flag(ext4_io_end_t *io_end)
130 {
131 	struct inode *inode = io_end->inode;
132 
133 	io_end->flag &= ~EXT4_IO_END_UNWRITTEN;
134 	/* Wake up anyone waiting on unwritten extent conversion */
135 	if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
136 		wake_up_all(ext4_ioend_wq(inode));
137 }
138 
139 /*
140  * Check a range of space and convert unwritten extents to written. Note that
141  * we are protected from truncate touching same part of extent tree by the
142  * fact that truncate code waits for all DIO to finish (thus exclusion from
143  * direct IO is achieved) and also waits for PageWriteback bits. Thus we
144  * cannot get to ext4_ext_truncate() before all IOs overlapping that range are
145  * completed (happens from ext4_free_ioend()).
146  */
147 static int ext4_end_io(ext4_io_end_t *io)
148 {
149 	struct inode *inode = io->inode;
150 	loff_t offset = io->offset;
151 	ssize_t size = io->size;
152 	handle_t *handle = io->handle;
153 	int ret = 0;
154 
155 	ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
156 		   "list->prev 0x%p\n",
157 		   io, inode->i_ino, io->list.next, io->list.prev);
158 
159 	io->handle = NULL;	/* Following call will use up the handle */
160 	ret = ext4_convert_unwritten_extents(handle, inode, offset, size);
161 	if (ret < 0) {
162 		ext4_msg(inode->i_sb, KERN_EMERG,
163 			 "failed to convert unwritten extents to written "
164 			 "extents -- potential data loss!  "
165 			 "(inode %lu, offset %llu, size %zd, error %d)",
166 			 inode->i_ino, offset, size, ret);
167 	}
168 	ext4_clear_io_unwritten_flag(io);
169 	ext4_release_io_end(io);
170 	return ret;
171 }
172 
173 static void dump_completed_IO(struct inode *inode, struct list_head *head)
174 {
175 #ifdef	EXT4FS_DEBUG
176 	struct list_head *cur, *before, *after;
177 	ext4_io_end_t *io, *io0, *io1;
178 
179 	if (list_empty(head))
180 		return;
181 
182 	ext4_debug("Dump inode %lu completed io list\n", inode->i_ino);
183 	list_for_each_entry(io, head, list) {
184 		cur = &io->list;
185 		before = cur->prev;
186 		io0 = container_of(before, ext4_io_end_t, list);
187 		after = cur->next;
188 		io1 = container_of(after, ext4_io_end_t, list);
189 
190 		ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
191 			    io, inode->i_ino, io0, io1);
192 	}
193 #endif
194 }
195 
196 /* Add the io_end to per-inode completed end_io list. */
197 static void ext4_add_complete_io(ext4_io_end_t *io_end)
198 {
199 	struct ext4_inode_info *ei = EXT4_I(io_end->inode);
200 	struct workqueue_struct *wq;
201 	unsigned long flags;
202 
203 	/* Only reserved conversions from writeback should enter here */
204 	WARN_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
205 	WARN_ON(!io_end->handle);
206 	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
207 	wq = EXT4_SB(io_end->inode->i_sb)->rsv_conversion_wq;
208 	if (list_empty(&ei->i_rsv_conversion_list))
209 		queue_work(wq, &ei->i_rsv_conversion_work);
210 	list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
211 	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
212 }
213 
214 static int ext4_do_flush_completed_IO(struct inode *inode,
215 				      struct list_head *head)
216 {
217 	ext4_io_end_t *io;
218 	struct list_head unwritten;
219 	unsigned long flags;
220 	struct ext4_inode_info *ei = EXT4_I(inode);
221 	int err, ret = 0;
222 
223 	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
224 	dump_completed_IO(inode, head);
225 	list_replace_init(head, &unwritten);
226 	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
227 
228 	while (!list_empty(&unwritten)) {
229 		io = list_entry(unwritten.next, ext4_io_end_t, list);
230 		BUG_ON(!(io->flag & EXT4_IO_END_UNWRITTEN));
231 		list_del_init(&io->list);
232 
233 		err = ext4_end_io(io);
234 		if (unlikely(!ret && err))
235 			ret = err;
236 	}
237 	return ret;
238 }
239 
240 /*
241  * work on completed IO, to convert unwritten extents to extents
242  */
243 void ext4_end_io_rsv_work(struct work_struct *work)
244 {
245 	struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
246 						  i_rsv_conversion_work);
247 	ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
248 }
249 
250 ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
251 {
252 	ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);
253 	if (io) {
254 		atomic_inc(&EXT4_I(inode)->i_ioend_count);
255 		io->inode = inode;
256 		INIT_LIST_HEAD(&io->list);
257 		atomic_set(&io->count, 1);
258 	}
259 	return io;
260 }
261 
262 void ext4_put_io_end_defer(ext4_io_end_t *io_end)
263 {
264 	if (atomic_dec_and_test(&io_end->count)) {
265 		if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) || !io_end->size) {
266 			ext4_release_io_end(io_end);
267 			return;
268 		}
269 		ext4_add_complete_io(io_end);
270 	}
271 }
272 
273 int ext4_put_io_end(ext4_io_end_t *io_end)
274 {
275 	int err = 0;
276 
277 	if (atomic_dec_and_test(&io_end->count)) {
278 		if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
279 			err = ext4_convert_unwritten_extents(io_end->handle,
280 						io_end->inode, io_end->offset,
281 						io_end->size);
282 			io_end->handle = NULL;
283 			ext4_clear_io_unwritten_flag(io_end);
284 		}
285 		ext4_release_io_end(io_end);
286 	}
287 	return err;
288 }
289 
290 ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
291 {
292 	atomic_inc(&io_end->count);
293 	return io_end;
294 }
295 
296 /* BIO completion function for page writeback */
297 static void ext4_end_bio(struct bio *bio, int error)
298 {
299 	ext4_io_end_t *io_end = bio->bi_private;
300 	sector_t bi_sector = bio->bi_sector;
301 
302 	BUG_ON(!io_end);
303 	bio->bi_end_io = NULL;
304 	if (test_bit(BIO_UPTODATE, &bio->bi_flags))
305 		error = 0;
306 
307 	if (error) {
308 		struct inode *inode = io_end->inode;
309 
310 		ext4_warning(inode->i_sb, "I/O error writing to inode %lu "
311 			     "(offset %llu size %ld starting block %llu)",
312 			     inode->i_ino,
313 			     (unsigned long long) io_end->offset,
314 			     (long) io_end->size,
315 			     (unsigned long long)
316 			     bi_sector >> (inode->i_blkbits - 9));
317 	}
318 
319 	if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
320 		/*
321 		 * Link bio into list hanging from io_end. We have to do it
322 		 * atomically as bio completions can be racing against each
323 		 * other.
324 		 */
325 		bio->bi_private = xchg(&io_end->bio, bio);
326 		ext4_put_io_end_defer(io_end);
327 	} else {
328 		/*
329 		 * Drop io_end reference early. Inode can get freed once
330 		 * we finish the bio.
331 		 */
332 		ext4_put_io_end_defer(io_end);
333 		ext4_finish_bio(bio);
334 		bio_put(bio);
335 	}
336 }
337 
338 void ext4_io_submit(struct ext4_io_submit *io)
339 {
340 	struct bio *bio = io->io_bio;
341 
342 	if (bio) {
343 		bio_get(io->io_bio);
344 		submit_bio(io->io_op, io->io_bio);
345 		BUG_ON(bio_flagged(io->io_bio, BIO_EOPNOTSUPP));
346 		bio_put(io->io_bio);
347 	}
348 	io->io_bio = NULL;
349 }
350 
351 void ext4_io_submit_init(struct ext4_io_submit *io,
352 			 struct writeback_control *wbc)
353 {
354 	io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?  WRITE_SYNC : WRITE);
355 	io->io_bio = NULL;
356 	io->io_end = NULL;
357 }
358 
359 static int io_submit_init_bio(struct ext4_io_submit *io,
360 			      struct buffer_head *bh)
361 {
362 	int nvecs = bio_get_nr_vecs(bh->b_bdev);
363 	struct bio *bio;
364 
365 	bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
366 	if (!bio)
367 		return -ENOMEM;
368 	bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
369 	bio->bi_bdev = bh->b_bdev;
370 	bio->bi_end_io = ext4_end_bio;
371 	bio->bi_private = ext4_get_io_end(io->io_end);
372 	io->io_bio = bio;
373 	io->io_next_block = bh->b_blocknr;
374 	return 0;
375 }
376 
377 static int io_submit_add_bh(struct ext4_io_submit *io,
378 			    struct inode *inode,
379 			    struct buffer_head *bh)
380 {
381 	int ret;
382 
383 	if (io->io_bio && bh->b_blocknr != io->io_next_block) {
384 submit_and_retry:
385 		ext4_io_submit(io);
386 	}
387 	if (io->io_bio == NULL) {
388 		ret = io_submit_init_bio(io, bh);
389 		if (ret)
390 			return ret;
391 	}
392 	ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
393 	if (ret != bh->b_size)
394 		goto submit_and_retry;
395 	io->io_next_block++;
396 	return 0;
397 }
398 
399 int ext4_bio_write_page(struct ext4_io_submit *io,
400 			struct page *page,
401 			int len,
402 			struct writeback_control *wbc)
403 {
404 	struct inode *inode = page->mapping->host;
405 	unsigned block_start, blocksize;
406 	struct buffer_head *bh, *head;
407 	int ret = 0;
408 	int nr_submitted = 0;
409 
410 	blocksize = 1 << inode->i_blkbits;
411 
412 	BUG_ON(!PageLocked(page));
413 	BUG_ON(PageWriteback(page));
414 
415 	set_page_writeback(page);
416 	ClearPageError(page);
417 
418 	/*
419 	 * In the first loop we prepare and mark buffers to submit. We have to
420 	 * mark all buffers in the page before submitting so that
421 	 * end_page_writeback() cannot be called from ext4_bio_end_io() when IO
422 	 * on the first buffer finishes and we are still working on submitting
423 	 * the second buffer.
424 	 */
425 	bh = head = page_buffers(page);
426 	do {
427 		block_start = bh_offset(bh);
428 		if (block_start >= len) {
429 			/*
430 			 * Comments copied from block_write_full_page_endio:
431 			 *
432 			 * The page straddles i_size.  It must be zeroed out on
433 			 * each and every writepage invocation because it may
434 			 * be mmapped.  "A file is mapped in multiples of the
435 			 * page size.  For a file that is not a multiple of
436 			 * the  page size, the remaining memory is zeroed when
437 			 * mapped, and writes to that region are not written
438 			 * out to the file."
439 			 */
440 			zero_user_segment(page, block_start,
441 					  block_start + blocksize);
442 			clear_buffer_dirty(bh);
443 			set_buffer_uptodate(bh);
444 			continue;
445 		}
446 		if (!buffer_dirty(bh) || buffer_delay(bh) ||
447 		    !buffer_mapped(bh) || buffer_unwritten(bh)) {
448 			/* A hole? We can safely clear the dirty bit */
449 			if (!buffer_mapped(bh))
450 				clear_buffer_dirty(bh);
451 			if (io->io_bio)
452 				ext4_io_submit(io);
453 			continue;
454 		}
455 		if (buffer_new(bh)) {
456 			clear_buffer_new(bh);
457 			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
458 		}
459 		set_buffer_async_write(bh);
460 	} while ((bh = bh->b_this_page) != head);
461 
462 	/* Now submit buffers to write */
463 	bh = head = page_buffers(page);
464 	do {
465 		if (!buffer_async_write(bh))
466 			continue;
467 		ret = io_submit_add_bh(io, inode, bh);
468 		if (ret) {
469 			/*
470 			 * We only get here on ENOMEM.  Not much else
471 			 * we can do but mark the page as dirty, and
472 			 * better luck next time.
473 			 */
474 			redirty_page_for_writepage(wbc, page);
475 			break;
476 		}
477 		nr_submitted++;
478 		clear_buffer_dirty(bh);
479 	} while ((bh = bh->b_this_page) != head);
480 
481 	/* Error stopped previous loop? Clean up buffers... */
482 	if (ret) {
483 		do {
484 			clear_buffer_async_write(bh);
485 			bh = bh->b_this_page;
486 		} while (bh != head);
487 	}
488 	unlock_page(page);
489 	/* Nothing submitted - we have to end page writeback */
490 	if (!nr_submitted)
491 		end_page_writeback(page);
492 	return ret;
493 }
494