1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2010 Red Hat, Inc.
  4 * Copyright (c) 2016-2021 Christoph Hellwig.
  5 */
  6#include <linux/module.h>
  7#include <linux/compiler.h>
  8#include <linux/fs.h>
  9#include <linux/fscrypt.h>
 10#include <linux/pagemap.h>
 11#include <linux/iomap.h>
 12#include <linux/backing-dev.h>
 13#include <linux/uio.h>
 14#include <linux/task_io_accounting_ops.h>
 15#include "trace.h"
 16
 17#include "../internal.h"
 18
 19/*
 20 * Private flags for iomap_dio, must not overlap with the public ones in
 21 * iomap.h:
 22 */
 23#define IOMAP_DIO_CALLER_COMP	(1U << 26)
 24#define IOMAP_DIO_INLINE_COMP	(1U << 27)
 25#define IOMAP_DIO_WRITE_THROUGH	(1U << 28)
 26#define IOMAP_DIO_NEED_SYNC	(1U << 29)
 27#define IOMAP_DIO_WRITE		(1U << 30)
 28#define IOMAP_DIO_DIRTY		(1U << 31)
 29
 30struct iomap_dio {
 31	struct kiocb		*iocb;
 32	const struct iomap_dio_ops *dops;
 33	loff_t			i_size;
 34	loff_t			size;
 35	atomic_t		ref;
 36	unsigned		flags;
 37	int			error;
 38	size_t			done_before;
 39	bool			wait_for_completion;
 40
 41	union {
 42		/* used during submission and for synchronous completion: */
 43		struct {
 44			struct iov_iter		*iter;
 45			struct task_struct	*waiter;
 
 
 46		} submit;
 47
 48		/* used for aio completion: */
 49		struct {
 50			struct work_struct	work;
 51		} aio;
 52	};
 53};
 54
 55static struct bio *iomap_dio_alloc_bio(const struct iomap_iter *iter,
 56		struct iomap_dio *dio, unsigned short nr_vecs, blk_opf_t opf)
 57{
 58	if (dio->dops && dio->dops->bio_set)
 59		return bio_alloc_bioset(iter->iomap.bdev, nr_vecs, opf,
 60					GFP_KERNEL, dio->dops->bio_set);
 61	return bio_alloc(iter->iomap.bdev, nr_vecs, opf, GFP_KERNEL);
 
 62}
 
 63
 64static void iomap_dio_submit_bio(const struct iomap_iter *iter,
 65		struct iomap_dio *dio, struct bio *bio, loff_t pos)
 66{
 67	struct kiocb *iocb = dio->iocb;
 68
 69	atomic_inc(&dio->ref);
 70
 71	/* Sync dio can't be polled reliably */
 72	if ((iocb->ki_flags & IOCB_HIPRI) && !is_sync_kiocb(iocb)) {
 73		bio_set_polled(bio, iocb);
 74		WRITE_ONCE(iocb->private, bio);
 75	}
 76
 
 77	if (dio->dops && dio->dops->submit_io)
 78		dio->dops->submit_io(iter, bio, pos);
 
 
 79	else
 80		submit_bio(bio);
 81}
 82
 83ssize_t iomap_dio_complete(struct iomap_dio *dio)
 84{
 85	const struct iomap_dio_ops *dops = dio->dops;
 86	struct kiocb *iocb = dio->iocb;
 
 87	loff_t offset = iocb->ki_pos;
 88	ssize_t ret = dio->error;
 89
 90	if (dops && dops->end_io)
 91		ret = dops->end_io(iocb, dio->size, ret, dio->flags);
 92
 93	if (likely(!ret)) {
 94		ret = dio->size;
 95		/* check for short read */
 96		if (offset + ret > dio->i_size &&
 97		    !(dio->flags & IOMAP_DIO_WRITE))
 98			ret = dio->i_size - offset;
 
 99	}
100
101	/*
102	 * Try again to invalidate clean pages which might have been cached by
103	 * non-direct readahead, or faulted in by get_user_pages() if the source
104	 * of the write was an mmap'ed region of the file we're writing.  Either
105	 * one is a pretty crazy thing to do, so we don't support it 100%.  If
106	 * this invalidation fails, tough, the write still worked...
107	 *
108	 * And this page cache invalidation has to be after ->end_io(), as some
109	 * filesystems convert unwritten extents to real allocations in
110	 * ->end_io() when necessary, otherwise a racing buffer read would cache
111	 * zeros from unwritten extents.
112	 */
113	if (!dio->error && dio->size && (dio->flags & IOMAP_DIO_WRITE))
114		kiocb_invalidate_post_direct_write(iocb, dio->size);
115
116	inode_dio_end(file_inode(iocb->ki_filp));
 
 
 
 
 
117
118	if (ret > 0) {
119		iocb->ki_pos += ret;
 
 
 
 
120
121		/*
122		 * If this is a DSYNC write, make sure we push it to stable
123		 * storage now that we've written data.
124		 */
125		if (dio->flags & IOMAP_DIO_NEED_SYNC)
126			ret = generic_write_sync(iocb, ret);
127		if (ret > 0)
128			ret += dio->done_before;
129	}
130	trace_iomap_dio_complete(iocb, dio->error, ret);
131	kfree(dio);
132	return ret;
133}
134EXPORT_SYMBOL_GPL(iomap_dio_complete);
135
136static ssize_t iomap_dio_deferred_complete(void *data)
137{
138	return iomap_dio_complete(data);
139}
140
141static void iomap_dio_complete_work(struct work_struct *work)
142{
143	struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
144	struct kiocb *iocb = dio->iocb;
145
146	iocb->ki_complete(iocb, iomap_dio_complete(dio));
147}
148
149/*
150 * Set an error in the dio if none is set yet.  We have to use cmpxchg
151 * as the submission context and the completion context(s) can race to
152 * update the error.
153 */
154static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
155{
156	cmpxchg(&dio->error, 0, ret);
157}
158
159void iomap_dio_bio_end_io(struct bio *bio)
160{
161	struct iomap_dio *dio = bio->bi_private;
162	bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
163	struct kiocb *iocb = dio->iocb;
164
165	if (bio->bi_status)
166		iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
167	if (!atomic_dec_and_test(&dio->ref))
168		goto release_bio;
169
170	/*
171	 * Synchronous dio, task itself will handle any completion work
172	 * that needs after IO. All we need to do is wake the task.
173	 */
174	if (dio->wait_for_completion) {
175		struct task_struct *waiter = dio->submit.waiter;
 
176
177		WRITE_ONCE(dio->submit.waiter, NULL);
178		blk_wake_io_task(waiter);
179		goto release_bio;
180	}
181
182	/*
183	 * Flagged with IOMAP_DIO_INLINE_COMP, we can complete it inline
184	 */
185	if (dio->flags & IOMAP_DIO_INLINE_COMP) {
186		WRITE_ONCE(iocb->private, NULL);
187		iomap_dio_complete_work(&dio->aio.work);
188		goto release_bio;
189	}
190
191	/*
192	 * If this dio is flagged with IOMAP_DIO_CALLER_COMP, then schedule
193	 * our completion that way to avoid an async punt to a workqueue.
194	 */
195	if (dio->flags & IOMAP_DIO_CALLER_COMP) {
196		/* only polled IO cares about private cleared */
197		iocb->private = dio;
198		iocb->dio_complete = iomap_dio_deferred_complete;
199
200		/*
201		 * Invoke ->ki_complete() directly. We've assigned our
202		 * dio_complete callback handler, and since the issuer set
203		 * IOCB_DIO_CALLER_COMP, we know their ki_complete handler will
204		 * notice ->dio_complete being set and will defer calling that
205		 * handler until it can be done from a safe task context.
206		 *
207		 * Note that the 'res' being passed in here is not important
208		 * for this case. The actual completion value of the request
209		 * will be gotten from dio_complete when that is run by the
210		 * issuer.
211		 */
212		iocb->ki_complete(iocb, 0);
213		goto release_bio;
214	}
215
216	/*
217	 * Async DIO completion that requires filesystem level completion work
218	 * gets punted to a work queue to complete as the operation may require
219	 * more IO to be issued to finalise filesystem metadata changes or
220	 * guarantee data integrity.
221	 */
222	INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
223	queue_work(file_inode(iocb->ki_filp)->i_sb->s_dio_done_wq,
224			&dio->aio.work);
225release_bio:
226	if (should_dirty) {
227		bio_check_pages_dirty(bio);
228	} else {
229		bio_release_pages(bio, false);
230		bio_put(bio);
231	}
232}
233EXPORT_SYMBOL_GPL(iomap_dio_bio_end_io);
234
235static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
236		loff_t pos, unsigned len)
 
237{
238	struct inode *inode = file_inode(dio->iocb->ki_filp);
239	struct page *page = ZERO_PAGE(0);
 
240	struct bio *bio;
241
242	bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
243	fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
244				  GFP_KERNEL);
245	bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos);
246	bio->bi_private = dio;
247	bio->bi_end_io = iomap_dio_bio_end_io;
248
 
249	__bio_add_page(bio, page, len, 0);
250	iomap_dio_submit_bio(iter, dio, bio, pos);
 
251}
252
253/*
254 * Figure out the bio's operation flags from the dio request, the
255 * mapping, and whether or not we want FUA.  Note that we can end up
256 * clearing the WRITE_THROUGH flag in the dio request.
257 */
258static inline blk_opf_t iomap_dio_bio_opflags(struct iomap_dio *dio,
259		const struct iomap *iomap, bool use_fua)
260{
261	blk_opf_t opflags = REQ_SYNC | REQ_IDLE;
262
263	if (!(dio->flags & IOMAP_DIO_WRITE))
264		return REQ_OP_READ;
265
266	opflags |= REQ_OP_WRITE;
267	if (use_fua)
268		opflags |= REQ_FUA;
269	else
270		dio->flags &= ~IOMAP_DIO_WRITE_THROUGH;
271
272	return opflags;
273}
274
275static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
276		struct iomap_dio *dio)
277{
278	const struct iomap *iomap = &iter->iomap;
279	struct inode *inode = iter->inode;
280	unsigned int fs_block_size = i_blocksize(inode), pad;
281	loff_t length = iomap_length(iter);
282	loff_t pos = iter->pos;
283	blk_opf_t bio_opf;
284	struct bio *bio;
285	bool need_zeroout = false;
286	bool use_fua = false;
287	int nr_pages, ret = 0;
288	size_t copied = 0;
289	size_t orig_count;
290
291	if ((pos | length) & (bdev_logical_block_size(iomap->bdev) - 1) ||
292	    !bdev_iter_is_aligned(iomap->bdev, dio->submit.iter))
293		return -EINVAL;
294
295	if (iomap->type == IOMAP_UNWRITTEN) {
296		dio->flags |= IOMAP_DIO_UNWRITTEN;
297		need_zeroout = true;
298	}
299
300	if (iomap->flags & IOMAP_F_SHARED)
301		dio->flags |= IOMAP_DIO_COW;
302
303	if (iomap->flags & IOMAP_F_NEW) {
304		need_zeroout = true;
305	} else if (iomap->type == IOMAP_MAPPED) {
306		/*
307		 * Use a FUA write if we need datasync semantics, this is a pure
308		 * data IO that doesn't require any metadata updates (including
309		 * after IO completion such as unwritten extent conversion) and
310		 * the underlying device either supports FUA or doesn't have
311		 * a volatile write cache. This allows us to avoid cache flushes
312		 * on IO completion. If we can't use writethrough and need to
313		 * sync, disable in-task completions as dio completion will
314		 * need to call generic_write_sync() which will do a blocking
315		 * fsync / cache flush call.
316		 */
317		if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
318		    (dio->flags & IOMAP_DIO_WRITE_THROUGH) &&
319		    (bdev_fua(iomap->bdev) || !bdev_write_cache(iomap->bdev)))
320			use_fua = true;
321		else if (dio->flags & IOMAP_DIO_NEED_SYNC)
322			dio->flags &= ~IOMAP_DIO_CALLER_COMP;
323	}
324
325	/*
326	 * Save the original count and trim the iter to just the extent we
327	 * are operating on right now.  The iter will be re-expanded once
328	 * we are done.
329	 */
330	orig_count = iov_iter_count(dio->submit.iter);
331	iov_iter_truncate(dio->submit.iter, length);
332
333	if (!iov_iter_count(dio->submit.iter))
 
 
334		goto out;
335
336	/*
337	 * We can only do deferred completion for pure overwrites that
338	 * don't require additional IO at completion. This rules out
339	 * writes that need zeroing or extent conversion, extend
340	 * the file size, or issue journal IO or cache flushes
341	 * during completion processing.
342	 */
343	if (need_zeroout ||
344	    ((dio->flags & IOMAP_DIO_NEED_SYNC) && !use_fua) ||
345	    ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode)))
346		dio->flags &= ~IOMAP_DIO_CALLER_COMP;
347
348	/*
349	 * The rules for polled IO completions follow the guidelines as the
350	 * ones we set for inline and deferred completions. If none of those
351	 * are available for this IO, clear the polled flag.
352	 */
353	if (!(dio->flags & (IOMAP_DIO_INLINE_COMP|IOMAP_DIO_CALLER_COMP)))
354		dio->iocb->ki_flags &= ~IOCB_HIPRI;
355
356	if (need_zeroout) {
357		/* zero out from the start of the block to the write offset */
358		pad = pos & (fs_block_size - 1);
359		if (pad)
360			iomap_dio_zero(iter, dio, pos - pad, pad);
361	}
362
363	/*
364	 * Set the operation flags early so that bio_iov_iter_get_pages
365	 * can set up the page vector appropriately for a ZONE_APPEND
366	 * operation.
367	 */
368	bio_opf = iomap_dio_bio_opflags(dio, iomap, use_fua);
369
370	nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, BIO_MAX_VECS);
371	do {
372		size_t n;
373		if (dio->error) {
374			iov_iter_revert(dio->submit.iter, copied);
375			copied = ret = 0;
376			goto out;
377		}
378
379		bio = iomap_dio_alloc_bio(iter, dio, nr_pages, bio_opf);
380		fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
381					  GFP_KERNEL);
382		bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
383		bio->bi_write_hint = inode->i_write_hint;
384		bio->bi_ioprio = dio->iocb->ki_ioprio;
385		bio->bi_private = dio;
386		bio->bi_end_io = iomap_dio_bio_end_io;
387
388		ret = bio_iov_iter_get_pages(bio, dio->submit.iter);
389		if (unlikely(ret)) {
390			/*
391			 * We have to stop part way through an IO. We must fall
392			 * through to the sub-block tail zeroing here, otherwise
393			 * this short IO may expose stale data in the tail of
394			 * the block we haven't written data to.
395			 */
396			bio_put(bio);
397			goto zero_tail;
398		}
399
400		n = bio->bi_iter.bi_size;
401		if (dio->flags & IOMAP_DIO_WRITE) {
 
 
 
 
 
402			task_io_account_write(n);
403		} else {
 
404			if (dio->flags & IOMAP_DIO_DIRTY)
405				bio_set_pages_dirty(bio);
406		}
407
408		dio->size += n;
409		copied += n;
410
411		nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter,
412						 BIO_MAX_VECS);
413		/*
414		 * We can only poll for single bio I/Os.
415		 */
416		if (nr_pages)
417			dio->iocb->ki_flags &= ~IOCB_HIPRI;
418		iomap_dio_submit_bio(iter, dio, bio, pos);
419		pos += n;
420	} while (nr_pages);
421
422	/*
423	 * We need to zeroout the tail of a sub-block write if the extent type
424	 * requires zeroing or the write extends beyond EOF. If we don't zero
425	 * the block tail in the latter case, we can expose stale data via mmap
426	 * reads of the EOF block.
427	 */
428zero_tail:
429	if (need_zeroout ||
430	    ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) {
431		/* zero out from the end of the write to the end of the block */
432		pad = pos & (fs_block_size - 1);
433		if (pad)
434			iomap_dio_zero(iter, dio, pos, fs_block_size - pad);
435	}
436out:
437	/* Undo iter limitation to current extent */
438	iov_iter_reexpand(dio->submit.iter, orig_count - copied);
439	if (copied)
440		return copied;
441	return ret;
442}
443
444static loff_t iomap_dio_hole_iter(const struct iomap_iter *iter,
445		struct iomap_dio *dio)
446{
447	loff_t length = iov_iter_zero(iomap_length(iter), dio->submit.iter);
448
449	dio->size += length;
450	if (!length)
451		return -EFAULT;
452	return length;
453}
454
455static loff_t iomap_dio_inline_iter(const struct iomap_iter *iomi,
456		struct iomap_dio *dio)
 
457{
458	const struct iomap *iomap = &iomi->iomap;
459	struct iov_iter *iter = dio->submit.iter;
460	void *inline_data = iomap_inline_data(iomap, iomi->pos);
461	loff_t length = iomap_length(iomi);
462	loff_t pos = iomi->pos;
463	size_t copied;
464
465	if (WARN_ON_ONCE(!iomap_inline_data_valid(iomap)))
466		return -EIO;
467
468	if (dio->flags & IOMAP_DIO_WRITE) {
469		loff_t size = iomi->inode->i_size;
470
471		if (pos > size)
472			memset(iomap_inline_data(iomap, size), 0, pos - size);
473		copied = copy_from_iter(inline_data, length, iter);
474		if (copied) {
475			if (pos + copied > size)
476				i_size_write(iomi->inode, pos + copied);
477			mark_inode_dirty(iomi->inode);
478		}
479	} else {
480		copied = copy_to_iter(inline_data, length, iter);
481	}
482	dio->size += copied;
483	if (!copied)
484		return -EFAULT;
485	return copied;
486}
487
488static loff_t iomap_dio_iter(const struct iomap_iter *iter,
489		struct iomap_dio *dio)
 
490{
491	switch (iter->iomap.type) {
 
 
492	case IOMAP_HOLE:
493		if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
494			return -EIO;
495		return iomap_dio_hole_iter(iter, dio);
496	case IOMAP_UNWRITTEN:
497		if (!(dio->flags & IOMAP_DIO_WRITE))
498			return iomap_dio_hole_iter(iter, dio);
499		return iomap_dio_bio_iter(iter, dio);
500	case IOMAP_MAPPED:
501		return iomap_dio_bio_iter(iter, dio);
502	case IOMAP_INLINE:
503		return iomap_dio_inline_iter(iter, dio);
504	case IOMAP_DELALLOC:
505		/*
506		 * DIO is not serialised against mmap() access at all, and so
507		 * if the page_mkwrite occurs between the writeback and the
508		 * iomap_iter() call in the DIO path, then it will see the
509		 * DELALLOC block that the page-mkwrite allocated.
510		 */
511		pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s\n",
512				    dio->iocb->ki_filp, current->comm);
513		return -EIO;
514	default:
515		WARN_ON_ONCE(1);
516		return -EIO;
517	}
518}
519
520/*
521 * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
522 * is being issued as AIO or not.  This allows us to optimise pure data writes
523 * to use REQ_FUA rather than requiring generic_write_sync() to issue a
524 * REQ_FLUSH post write. This is slightly tricky because a single request here
525 * can be mapped into multiple disjoint IOs and only a subset of the IOs issued
526 * may be pure data writes. In that case, we still need to do a full data sync
527 * completion.
528 *
529 * When page faults are disabled and @dio_flags includes IOMAP_DIO_PARTIAL,
530 * __iomap_dio_rw can return a partial result if it encounters a non-resident
531 * page in @iter after preparing a transfer.  In that case, the non-resident
532 * pages can be faulted in and the request resumed with @done_before set to the
533 * number of bytes previously transferred.  The request will then complete with
534 * the correct total number of bytes transferred; this is essential for
535 * completing partial requests asynchronously.
536 *
537 * Returns -ENOTBLK In case of a page invalidation invalidation failure for
538 * writes.  The callers needs to fall back to buffered I/O in this case.
539 */
540struct iomap_dio *
541__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
542		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
543		unsigned int dio_flags, void *private, size_t done_before)
544{
 
545	struct inode *inode = file_inode(iocb->ki_filp);
546	struct iomap_iter iomi = {
547		.inode		= inode,
548		.pos		= iocb->ki_pos,
549		.len		= iov_iter_count(iter),
550		.flags		= IOMAP_DIRECT,
551		.private	= private,
552	};
553	bool wait_for_completion =
554		is_sync_kiocb(iocb) || (dio_flags & IOMAP_DIO_FORCE_WAIT);
555	struct blk_plug plug;
556	struct iomap_dio *dio;
557	loff_t ret = 0;
558
559	trace_iomap_dio_rw_begin(iocb, iter, dio_flags, done_before);
 
560
561	if (!iomi.len)
562		return NULL;
563
564	dio = kmalloc(sizeof(*dio), GFP_KERNEL);
565	if (!dio)
566		return ERR_PTR(-ENOMEM);
567
568	dio->iocb = iocb;
569	atomic_set(&dio->ref, 1);
570	dio->size = 0;
571	dio->i_size = i_size_read(inode);
572	dio->dops = dops;
573	dio->error = 0;
574	dio->flags = 0;
575	dio->done_before = done_before;
576
577	dio->submit.iter = iter;
578	dio->submit.waiter = current;
579
580	if (iocb->ki_flags & IOCB_NOWAIT)
581		iomi.flags |= IOMAP_NOWAIT;
582
583	if (iov_iter_rw(iter) == READ) {
584		/* reads can always complete inline */
585		dio->flags |= IOMAP_DIO_INLINE_COMP;
586
587		if (iomi.pos >= dio->i_size)
588			goto out_free_dio;
589
590		if (user_backed_iter(iter))
591			dio->flags |= IOMAP_DIO_DIRTY;
592
593		ret = kiocb_write_and_wait(iocb, iomi.len);
594		if (ret)
595			goto out_free_dio;
596	} else {
597		iomi.flags |= IOMAP_WRITE;
598		dio->flags |= IOMAP_DIO_WRITE;
599
 
 
 
 
600		/*
601		 * Flag as supporting deferred completions, if the issuer
602		 * groks it. This can avoid a workqueue punt for writes.
603		 * We may later clear this flag if we need to do other IO
604		 * as part of this IO completion.
605		 */
606		if (iocb->ki_flags & IOCB_DIO_CALLER_COMP)
607			dio->flags |= IOMAP_DIO_CALLER_COMP;
 
608
609		if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
 
610			ret = -EAGAIN;
611			if (iomi.pos >= dio->i_size ||
612			    iomi.pos + iomi.len > dio->i_size)
613				goto out_free_dio;
614			iomi.flags |= IOMAP_OVERWRITE_ONLY;
615		}
 
 
616
617		/* for data sync or sync, we need sync completion processing */
618		if (iocb_is_dsync(iocb)) {
619			dio->flags |= IOMAP_DIO_NEED_SYNC;
620
621		       /*
622			* For datasync only writes, we optimistically try using
623			* WRITE_THROUGH for this IO. This flag requires either
624			* FUA writes through the device's write cache, or a
625			* normal write to a device without a volatile write
626			* cache. For the former, Any non-FUA write that occurs
627			* will clear this flag, hence we know before completion
628			* whether a cache flush is necessary.
629			*/
630			if (!(iocb->ki_flags & IOCB_SYNC))
631				dio->flags |= IOMAP_DIO_WRITE_THROUGH;
632		}
633
 
634		/*
635		 * Try to invalidate cache pages for the range we are writing.
636		 * If this invalidation fails, let the caller fall back to
637		 * buffered I/O.
638		 */
639		ret = kiocb_invalidate_pages(iocb, iomi.len);
640		if (ret) {
641			if (ret != -EAGAIN) {
642				trace_iomap_dio_invalidate_fail(inode, iomi.pos,
643								iomi.len);
644				ret = -ENOTBLK;
645			}
646			goto out_free_dio;
647		}
648
649		if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) {
650			ret = sb_init_dio_done_wq(inode->i_sb);
651			if (ret < 0)
652				goto out_free_dio;
653		}
654	}
655
656	inode_dio_begin(inode);
657
658	blk_start_plug(&plug);
659	while ((ret = iomap_iter(&iomi, ops)) > 0) {
660		iomi.processed = iomap_dio_iter(&iomi, dio);
661
662		/*
663		 * We can only poll for single bio I/Os.
664		 */
665		iocb->ki_flags &= ~IOCB_HIPRI;
666	}
 
 
 
 
667
 
 
 
 
 
 
 
 
 
 
668	blk_finish_plug(&plug);
669
670	/*
671	 * We only report that we've read data up to i_size.
672	 * Revert iter to a state corresponding to that as some callers (such
673	 * as the splice code) rely on it.
674	 */
675	if (iov_iter_rw(iter) == READ && iomi.pos >= dio->i_size)
676		iov_iter_revert(iter, iomi.pos - dio->i_size);
677
678	if (ret == -EFAULT && dio->size && (dio_flags & IOMAP_DIO_PARTIAL)) {
679		if (!(iocb->ki_flags & IOCB_NOWAIT))
680			wait_for_completion = true;
681		ret = 0;
682	}
683
684	/* magic error code to fall back to buffered I/O */
685	if (ret == -ENOTBLK) {
686		wait_for_completion = true;
687		ret = 0;
688	}
689	if (ret < 0)
690		iomap_dio_set_error(dio, ret);
691
692	/*
693	 * If all the writes we issued were already written through to the
694	 * media, we don't need to flush the cache on IO completion. Clear the
695	 * sync flag for this case.
696	 */
697	if (dio->flags & IOMAP_DIO_WRITE_THROUGH)
698		dio->flags &= ~IOMAP_DIO_NEED_SYNC;
699
 
 
 
700	/*
701	 * We are about to drop our additional submission reference, which
702	 * might be the last reference to the dio.  There are three different
703	 * ways we can progress here:
704	 *
705	 *  (a) If this is the last reference we will always complete and free
706	 *	the dio ourselves.
707	 *  (b) If this is not the last reference, and we serve an asynchronous
708	 *	iocb, we must never touch the dio after the decrement, the
709	 *	I/O completion handler will complete and free it.
710	 *  (c) If this is not the last reference, but we serve a synchronous
711	 *	iocb, the I/O completion handler will wake us up on the drop
712	 *	of the final reference, and we will complete and free it here
713	 *	after we got woken by the I/O completion handler.
714	 */
715	dio->wait_for_completion = wait_for_completion;
716	if (!atomic_dec_and_test(&dio->ref)) {
717		if (!wait_for_completion) {
718			trace_iomap_dio_rw_queued(inode, iomi.pos, iomi.len);
719			return ERR_PTR(-EIOCBQUEUED);
720		}
721
722		for (;;) {
723			set_current_state(TASK_UNINTERRUPTIBLE);
724			if (!READ_ONCE(dio->submit.waiter))
725				break;
726
727			blk_io_schedule();
 
 
 
 
728		}
729		__set_current_state(TASK_RUNNING);
730	}
731
732	return dio;
733
734out_free_dio:
735	kfree(dio);
736	if (ret)
737		return ERR_PTR(ret);
738	return NULL;
739}
740EXPORT_SYMBOL_GPL(__iomap_dio_rw);
741
742ssize_t
743iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
744		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
745		unsigned int dio_flags, void *private, size_t done_before)
746{
747	struct iomap_dio *dio;
748
749	dio = __iomap_dio_rw(iocb, iter, ops, dops, dio_flags, private,
750			     done_before);
751	if (IS_ERR_OR_NULL(dio))
752		return PTR_ERR_OR_ZERO(dio);
753	return iomap_dio_complete(dio);
754}
755EXPORT_SYMBOL_GPL(iomap_dio_rw);