xref: /openbmc/linux/fs/nfs/direct.c (revision 92b19ff5)
1 /*
2  * linux/fs/nfs/direct.c
3  *
4  * Copyright (C) 2003 by Chuck Lever <cel@netapp.com>
5  *
6  * High-performance uncached I/O for the Linux NFS client
7  *
8  * There are important applications whose performance or correctness
9  * depends on uncached access to file data.  Database clusters
10  * (multiple copies of the same instance running on separate hosts)
11  * implement their own cache coherency protocol that subsumes file
12  * system cache protocols.  Applications that process datasets
13  * considerably larger than the client's memory do not always benefit
14  * from a local cache.  A streaming video server, for instance, has no
15  * need to cache the contents of a file.
16  *
17  * When an application requests uncached I/O, all read and write requests
18  * are made directly to the server; data stored or fetched via these
19  * requests is not cached in the Linux page cache.  The client does not
20  * correct unaligned requests from applications.  All requested bytes are
21  * held on permanent storage before a direct write system call returns to
22  * an application.
23  *
24  * Solaris implements an uncached I/O facility called directio() that
25  * is used for backups and sequential I/O to very large files.  Solaris
26  * also supports uncaching whole NFS partitions with "-o forcedirectio,"
27  * an undocumented mount option.
28  *
29  * Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust, with
30  * help from Andrew Morton.
31  *
32  * 18 Dec 2001	Initial implementation for 2.4  --cel
33  * 08 Jul 2002	Version for 2.4.19, with bug fixes --trondmy
34  * 08 Jun 2003	Port to 2.5 APIs  --cel
35  * 31 Mar 2004	Handle direct I/O without VFS support  --cel
36  * 15 Sep 2004	Parallel async reads  --cel
37  * 04 May 2005	support O_DIRECT with aio  --cel
38  *
39  */
40 
41 #include <linux/errno.h>
42 #include <linux/sched.h>
43 #include <linux/kernel.h>
44 #include <linux/file.h>
45 #include <linux/pagemap.h>
46 #include <linux/kref.h>
47 #include <linux/slab.h>
48 #include <linux/task_io_accounting_ops.h>
49 #include <linux/module.h>
50 
51 #include <linux/nfs_fs.h>
52 #include <linux/nfs_page.h>
53 #include <linux/sunrpc/clnt.h>
54 
55 #include <asm/uaccess.h>
56 #include <linux/atomic.h>
57 
58 #include "internal.h"
59 #include "iostat.h"
60 #include "pnfs.h"
61 
62 #define NFSDBG_FACILITY		NFSDBG_VFS
63 
64 static struct kmem_cache *nfs_direct_cachep;
65 
66 /*
67  * This represents a set of asynchronous requests that we're waiting on
68  */
69 struct nfs_direct_mirror {
70 	ssize_t count;
71 };
72 
73 struct nfs_direct_req {
74 	struct kref		kref;		/* release manager */
75 
76 	/* I/O parameters */
77 	struct nfs_open_context	*ctx;		/* file open context info */
78 	struct nfs_lock_context *l_ctx;		/* Lock context info */
79 	struct kiocb *		iocb;		/* controlling i/o request */
80 	struct inode *		inode;		/* target file of i/o */
81 
82 	/* completion state */
83 	atomic_t		io_count;	/* i/os we're waiting for */
84 	spinlock_t		lock;		/* protect completion state */
85 
86 	struct nfs_direct_mirror mirrors[NFS_PAGEIO_DESCRIPTOR_MIRROR_MAX];
87 	int			mirror_count;
88 
89 	ssize_t			count,		/* bytes actually processed */
90 				bytes_left,	/* bytes left to be sent */
91 				io_start,	/* start of IO */
92 				error;		/* any reported error */
93 	struct completion	completion;	/* wait for i/o completion */
94 
95 	/* commit state */
96 	struct nfs_mds_commit_info mds_cinfo;	/* Storage for cinfo */
97 	struct pnfs_ds_commit_info ds_cinfo;	/* Storage for cinfo */
98 	struct work_struct	work;
99 	int			flags;
100 #define NFS_ODIRECT_DO_COMMIT		(1)	/* an unstable reply was received */
101 #define NFS_ODIRECT_RESCHED_WRITES	(2)	/* write verification failed */
102 	struct nfs_writeverf	verf;		/* unstable write verifier */
103 };
104 
105 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops;
106 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops;
107 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode);
108 static void nfs_direct_write_schedule_work(struct work_struct *work);
109 
110 static inline void get_dreq(struct nfs_direct_req *dreq)
111 {
112 	atomic_inc(&dreq->io_count);
113 }
114 
115 static inline int put_dreq(struct nfs_direct_req *dreq)
116 {
117 	return atomic_dec_and_test(&dreq->io_count);
118 }
119 
120 void nfs_direct_set_resched_writes(struct nfs_direct_req *dreq)
121 {
122 	dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
123 }
124 EXPORT_SYMBOL_GPL(nfs_direct_set_resched_writes);
125 
126 static void
127 nfs_direct_good_bytes(struct nfs_direct_req *dreq, struct nfs_pgio_header *hdr)
128 {
129 	int i;
130 	ssize_t count;
131 
132 	if (dreq->mirror_count == 1) {
133 		dreq->mirrors[hdr->pgio_mirror_idx].count += hdr->good_bytes;
134 		dreq->count += hdr->good_bytes;
135 	} else {
136 		/* mirrored writes */
137 		count = dreq->mirrors[hdr->pgio_mirror_idx].count;
138 		if (count + dreq->io_start < hdr->io_start + hdr->good_bytes) {
139 			count = hdr->io_start + hdr->good_bytes - dreq->io_start;
140 			dreq->mirrors[hdr->pgio_mirror_idx].count = count;
141 		}
142 		/* update the dreq->count by finding the minimum agreed count from all
143 		 * mirrors */
144 		count = dreq->mirrors[0].count;
145 
146 		for (i = 1; i < dreq->mirror_count; i++)
147 			count = min(count, dreq->mirrors[i].count);
148 
149 		dreq->count = count;
150 	}
151 }
152 
153 /*
154  * nfs_direct_select_verf - select the right verifier
155  * @dreq - direct request possibly spanning multiple servers
156  * @ds_clp - nfs_client of data server or NULL if MDS / non-pnfs
157  * @commit_idx - commit bucket index for the DS
158  *
159  * returns the correct verifier to use given the role of the server
160  */
161 static struct nfs_writeverf *
162 nfs_direct_select_verf(struct nfs_direct_req *dreq,
163 		       struct nfs_client *ds_clp,
164 		       int commit_idx)
165 {
166 	struct nfs_writeverf *verfp = &dreq->verf;
167 
168 #ifdef CONFIG_NFS_V4_1
169 	if (ds_clp) {
170 		/* pNFS is in use, use the DS verf */
171 		if (commit_idx >= 0 && commit_idx < dreq->ds_cinfo.nbuckets)
172 			verfp = &dreq->ds_cinfo.buckets[commit_idx].direct_verf;
173 		else
174 			WARN_ON_ONCE(1);
175 	}
176 #endif
177 	return verfp;
178 }
179 
180 
181 /*
182  * nfs_direct_set_hdr_verf - set the write/commit verifier
183  * @dreq - direct request possibly spanning multiple servers
184  * @hdr - pageio header to validate against previously seen verfs
185  *
186  * Set the server's (MDS or DS) "seen" verifier
187  */
188 static void nfs_direct_set_hdr_verf(struct nfs_direct_req *dreq,
189 				    struct nfs_pgio_header *hdr)
190 {
191 	struct nfs_writeverf *verfp;
192 
193 	verfp = nfs_direct_select_verf(dreq, hdr->ds_clp, hdr->ds_commit_idx);
194 	WARN_ON_ONCE(verfp->committed >= 0);
195 	memcpy(verfp, &hdr->verf, sizeof(struct nfs_writeverf));
196 	WARN_ON_ONCE(verfp->committed < 0);
197 }
198 
199 /*
200  * nfs_direct_cmp_hdr_verf - compare verifier for pgio header
201  * @dreq - direct request possibly spanning multiple servers
202  * @hdr - pageio header to validate against previously seen verf
203  *
204  * set the server's "seen" verf if not initialized.
205  * returns result of comparison between @hdr->verf and the "seen"
206  * verf of the server used by @hdr (DS or MDS)
207  */
208 static int nfs_direct_set_or_cmp_hdr_verf(struct nfs_direct_req *dreq,
209 					  struct nfs_pgio_header *hdr)
210 {
211 	struct nfs_writeverf *verfp;
212 
213 	verfp = nfs_direct_select_verf(dreq, hdr->ds_clp, hdr->ds_commit_idx);
214 	if (verfp->committed < 0) {
215 		nfs_direct_set_hdr_verf(dreq, hdr);
216 		return 0;
217 	}
218 	return memcmp(verfp, &hdr->verf, sizeof(struct nfs_writeverf));
219 }
220 
221 /*
222  * nfs_direct_cmp_commit_data_verf - compare verifier for commit data
223  * @dreq - direct request possibly spanning multiple servers
224  * @data - commit data to validate against previously seen verf
225  *
226  * returns result of comparison between @data->verf and the verf of
227  * the server used by @data (DS or MDS)
228  */
229 static int nfs_direct_cmp_commit_data_verf(struct nfs_direct_req *dreq,
230 					   struct nfs_commit_data *data)
231 {
232 	struct nfs_writeverf *verfp;
233 
234 	verfp = nfs_direct_select_verf(dreq, data->ds_clp,
235 					 data->ds_commit_index);
236 
237 	/* verifier not set so always fail */
238 	if (verfp->committed < 0)
239 		return 1;
240 
241 	return memcmp(verfp, &data->verf, sizeof(struct nfs_writeverf));
242 }
243 
244 /**
245  * nfs_direct_IO - NFS address space operation for direct I/O
246  * @iocb: target I/O control block
247  * @iov: array of vectors that define I/O buffer
248  * @pos: offset in file to begin the operation
249  * @nr_segs: size of iovec array
250  *
251  * The presence of this routine in the address space ops vector means
252  * the NFS client supports direct I/O. However, for most direct IO, we
253  * shunt off direct read and write requests before the VFS gets them,
254  * so this method is only ever called for swap.
255  */
256 ssize_t nfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t pos)
257 {
258 	struct inode *inode = iocb->ki_filp->f_mapping->host;
259 
260 	/* we only support swap file calling nfs_direct_IO */
261 	if (!IS_SWAPFILE(inode))
262 		return 0;
263 
264 	VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE);
265 
266 	if (iov_iter_rw(iter) == READ)
267 		return nfs_file_direct_read(iocb, iter, pos);
268 	return nfs_file_direct_write(iocb, iter);
269 }
270 
271 static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
272 {
273 	unsigned int i;
274 	for (i = 0; i < npages; i++)
275 		page_cache_release(pages[i]);
276 }
277 
278 void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
279 			      struct nfs_direct_req *dreq)
280 {
281 	cinfo->lock = &dreq->inode->i_lock;
282 	cinfo->mds = &dreq->mds_cinfo;
283 	cinfo->ds = &dreq->ds_cinfo;
284 	cinfo->dreq = dreq;
285 	cinfo->completion_ops = &nfs_direct_commit_completion_ops;
286 }
287 
288 static inline void nfs_direct_setup_mirroring(struct nfs_direct_req *dreq,
289 					     struct nfs_pageio_descriptor *pgio,
290 					     struct nfs_page *req)
291 {
292 	int mirror_count = 1;
293 
294 	if (pgio->pg_ops->pg_get_mirror_count)
295 		mirror_count = pgio->pg_ops->pg_get_mirror_count(pgio, req);
296 
297 	dreq->mirror_count = mirror_count;
298 }
299 
300 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
301 {
302 	struct nfs_direct_req *dreq;
303 
304 	dreq = kmem_cache_zalloc(nfs_direct_cachep, GFP_KERNEL);
305 	if (!dreq)
306 		return NULL;
307 
308 	kref_init(&dreq->kref);
309 	kref_get(&dreq->kref);
310 	init_completion(&dreq->completion);
311 	INIT_LIST_HEAD(&dreq->mds_cinfo.list);
312 	dreq->verf.committed = NFS_INVALID_STABLE_HOW;	/* not set yet */
313 	INIT_WORK(&dreq->work, nfs_direct_write_schedule_work);
314 	dreq->mirror_count = 1;
315 	spin_lock_init(&dreq->lock);
316 
317 	return dreq;
318 }
319 
320 static void nfs_direct_req_free(struct kref *kref)
321 {
322 	struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
323 
324 	nfs_free_pnfs_ds_cinfo(&dreq->ds_cinfo);
325 	if (dreq->l_ctx != NULL)
326 		nfs_put_lock_context(dreq->l_ctx);
327 	if (dreq->ctx != NULL)
328 		put_nfs_open_context(dreq->ctx);
329 	kmem_cache_free(nfs_direct_cachep, dreq);
330 }
331 
332 static void nfs_direct_req_release(struct nfs_direct_req *dreq)
333 {
334 	kref_put(&dreq->kref, nfs_direct_req_free);
335 }
336 
337 ssize_t nfs_dreq_bytes_left(struct nfs_direct_req *dreq)
338 {
339 	return dreq->bytes_left;
340 }
341 EXPORT_SYMBOL_GPL(nfs_dreq_bytes_left);
342 
343 /*
344  * Collects and returns the final error value/byte-count.
345  */
346 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
347 {
348 	ssize_t result = -EIOCBQUEUED;
349 
350 	/* Async requests don't wait here */
351 	if (dreq->iocb)
352 		goto out;
353 
354 	result = wait_for_completion_killable(&dreq->completion);
355 
356 	if (!result)
357 		result = dreq->error;
358 	if (!result)
359 		result = dreq->count;
360 
361 out:
362 	return (ssize_t) result;
363 }
364 
365 /*
366  * Synchronous I/O uses a stack-allocated iocb.  Thus we can't trust
367  * the iocb is still valid here if this is a synchronous request.
368  */
369 static void nfs_direct_complete(struct nfs_direct_req *dreq, bool write)
370 {
371 	struct inode *inode = dreq->inode;
372 
373 	if (dreq->iocb && write) {
374 		loff_t pos = dreq->iocb->ki_pos + dreq->count;
375 
376 		spin_lock(&inode->i_lock);
377 		if (i_size_read(inode) < pos)
378 			i_size_write(inode, pos);
379 		spin_unlock(&inode->i_lock);
380 	}
381 
382 	if (write)
383 		nfs_zap_mapping(inode, inode->i_mapping);
384 
385 	inode_dio_end(inode);
386 
387 	if (dreq->iocb) {
388 		long res = (long) dreq->error;
389 		if (!res)
390 			res = (long) dreq->count;
391 		dreq->iocb->ki_complete(dreq->iocb, res, 0);
392 	}
393 
394 	complete_all(&dreq->completion);
395 
396 	nfs_direct_req_release(dreq);
397 }
398 
399 static void nfs_direct_readpage_release(struct nfs_page *req)
400 {
401 	dprintk("NFS: direct read done (%s/%llu %d@%lld)\n",
402 		d_inode(req->wb_context->dentry)->i_sb->s_id,
403 		(unsigned long long)NFS_FILEID(d_inode(req->wb_context->dentry)),
404 		req->wb_bytes,
405 		(long long)req_offset(req));
406 	nfs_release_request(req);
407 }
408 
409 static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
410 {
411 	unsigned long bytes = 0;
412 	struct nfs_direct_req *dreq = hdr->dreq;
413 
414 	if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
415 		goto out_put;
416 
417 	spin_lock(&dreq->lock);
418 	if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) && (hdr->good_bytes == 0))
419 		dreq->error = hdr->error;
420 	else
421 		nfs_direct_good_bytes(dreq, hdr);
422 
423 	spin_unlock(&dreq->lock);
424 
425 	while (!list_empty(&hdr->pages)) {
426 		struct nfs_page *req = nfs_list_entry(hdr->pages.next);
427 		struct page *page = req->wb_page;
428 
429 		if (!PageCompound(page) && bytes < hdr->good_bytes)
430 			set_page_dirty(page);
431 		bytes += req->wb_bytes;
432 		nfs_list_remove_request(req);
433 		nfs_direct_readpage_release(req);
434 	}
435 out_put:
436 	if (put_dreq(dreq))
437 		nfs_direct_complete(dreq, false);
438 	hdr->release(hdr);
439 }
440 
441 static void nfs_read_sync_pgio_error(struct list_head *head)
442 {
443 	struct nfs_page *req;
444 
445 	while (!list_empty(head)) {
446 		req = nfs_list_entry(head->next);
447 		nfs_list_remove_request(req);
448 		nfs_release_request(req);
449 	}
450 }
451 
452 static void nfs_direct_pgio_init(struct nfs_pgio_header *hdr)
453 {
454 	get_dreq(hdr->dreq);
455 }
456 
457 static const struct nfs_pgio_completion_ops nfs_direct_read_completion_ops = {
458 	.error_cleanup = nfs_read_sync_pgio_error,
459 	.init_hdr = nfs_direct_pgio_init,
460 	.completion = nfs_direct_read_completion,
461 };
462 
463 /*
464  * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
465  * operation.  If nfs_readdata_alloc() or get_user_pages() fails,
466  * bail and stop sending more reads.  Read length accounting is
467  * handled automatically by nfs_direct_read_result().  Otherwise, if
468  * no requests have been sent, just return an error.
469  */
470 
471 static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
472 					      struct iov_iter *iter,
473 					      loff_t pos)
474 {
475 	struct nfs_pageio_descriptor desc;
476 	struct inode *inode = dreq->inode;
477 	ssize_t result = -EINVAL;
478 	size_t requested_bytes = 0;
479 	size_t rsize = max_t(size_t, NFS_SERVER(inode)->rsize, PAGE_SIZE);
480 
481 	nfs_pageio_init_read(&desc, dreq->inode, false,
482 			     &nfs_direct_read_completion_ops);
483 	get_dreq(dreq);
484 	desc.pg_dreq = dreq;
485 	inode_dio_begin(inode);
486 
487 	while (iov_iter_count(iter)) {
488 		struct page **pagevec;
489 		size_t bytes;
490 		size_t pgbase;
491 		unsigned npages, i;
492 
493 		result = iov_iter_get_pages_alloc(iter, &pagevec,
494 						  rsize, &pgbase);
495 		if (result < 0)
496 			break;
497 
498 		bytes = result;
499 		iov_iter_advance(iter, bytes);
500 		npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
501 		for (i = 0; i < npages; i++) {
502 			struct nfs_page *req;
503 			unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
504 			/* XXX do we need to do the eof zeroing found in async_filler? */
505 			req = nfs_create_request(dreq->ctx, pagevec[i], NULL,
506 						 pgbase, req_len);
507 			if (IS_ERR(req)) {
508 				result = PTR_ERR(req);
509 				break;
510 			}
511 			req->wb_index = pos >> PAGE_SHIFT;
512 			req->wb_offset = pos & ~PAGE_MASK;
513 			if (!nfs_pageio_add_request(&desc, req)) {
514 				result = desc.pg_error;
515 				nfs_release_request(req);
516 				break;
517 			}
518 			pgbase = 0;
519 			bytes -= req_len;
520 			requested_bytes += req_len;
521 			pos += req_len;
522 			dreq->bytes_left -= req_len;
523 		}
524 		nfs_direct_release_pages(pagevec, npages);
525 		kvfree(pagevec);
526 		if (result < 0)
527 			break;
528 	}
529 
530 	nfs_pageio_complete(&desc);
531 
532 	/*
533 	 * If no bytes were started, return the error, and let the
534 	 * generic layer handle the completion.
535 	 */
536 	if (requested_bytes == 0) {
537 		inode_dio_end(inode);
538 		nfs_direct_req_release(dreq);
539 		return result < 0 ? result : -EIO;
540 	}
541 
542 	if (put_dreq(dreq))
543 		nfs_direct_complete(dreq, false);
544 	return 0;
545 }
546 
547 /**
548  * nfs_file_direct_read - file direct read operation for NFS files
549  * @iocb: target I/O control block
550  * @iter: vector of user buffers into which to read data
551  * @pos: byte offset in file where reading starts
552  *
553  * We use this function for direct reads instead of calling
554  * generic_file_aio_read() in order to avoid gfar's check to see if
555  * the request starts before the end of the file.  For that check
556  * to work, we must generate a GETATTR before each direct read, and
557  * even then there is a window between the GETATTR and the subsequent
558  * READ where the file size could change.  Our preference is simply
559  * to do all reads the application wants, and the server will take
560  * care of managing the end of file boundary.
561  *
562  * This function also eliminates unnecessarily updating the file's
563  * atime locally, as the NFS server sets the file's atime, and this
564  * client must read the updated atime from the server back into its
565  * cache.
566  */
567 ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
568 				loff_t pos)
569 {
570 	struct file *file = iocb->ki_filp;
571 	struct address_space *mapping = file->f_mapping;
572 	struct inode *inode = mapping->host;
573 	struct nfs_direct_req *dreq;
574 	struct nfs_lock_context *l_ctx;
575 	ssize_t result = -EINVAL;
576 	size_t count = iov_iter_count(iter);
577 	nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
578 
579 	dfprintk(FILE, "NFS: direct read(%pD2, %zd@%Ld)\n",
580 		file, count, (long long) pos);
581 
582 	result = 0;
583 	if (!count)
584 		goto out;
585 
586 	mutex_lock(&inode->i_mutex);
587 	result = nfs_sync_mapping(mapping);
588 	if (result)
589 		goto out_unlock;
590 
591 	task_io_account_read(count);
592 
593 	result = -ENOMEM;
594 	dreq = nfs_direct_req_alloc();
595 	if (dreq == NULL)
596 		goto out_unlock;
597 
598 	dreq->inode = inode;
599 	dreq->bytes_left = count;
600 	dreq->io_start = pos;
601 	dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
602 	l_ctx = nfs_get_lock_context(dreq->ctx);
603 	if (IS_ERR(l_ctx)) {
604 		result = PTR_ERR(l_ctx);
605 		goto out_release;
606 	}
607 	dreq->l_ctx = l_ctx;
608 	if (!is_sync_kiocb(iocb))
609 		dreq->iocb = iocb;
610 
611 	NFS_I(inode)->read_io += count;
612 	result = nfs_direct_read_schedule_iovec(dreq, iter, pos);
613 
614 	mutex_unlock(&inode->i_mutex);
615 
616 	if (!result) {
617 		result = nfs_direct_wait(dreq);
618 		if (result > 0)
619 			iocb->ki_pos = pos + result;
620 	}
621 
622 	nfs_direct_req_release(dreq);
623 	return result;
624 
625 out_release:
626 	nfs_direct_req_release(dreq);
627 out_unlock:
628 	mutex_unlock(&inode->i_mutex);
629 out:
630 	return result;
631 }
632 
633 static void
634 nfs_direct_write_scan_commit_list(struct inode *inode,
635 				  struct list_head *list,
636 				  struct nfs_commit_info *cinfo)
637 {
638 	spin_lock(cinfo->lock);
639 #ifdef CONFIG_NFS_V4_1
640 	if (cinfo->ds != NULL && cinfo->ds->nwritten != 0)
641 		NFS_SERVER(inode)->pnfs_curr_ld->recover_commit_reqs(list, cinfo);
642 #endif
643 	nfs_scan_commit_list(&cinfo->mds->list, list, cinfo, 0);
644 	spin_unlock(cinfo->lock);
645 }
646 
647 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
648 {
649 	struct nfs_pageio_descriptor desc;
650 	struct nfs_page *req, *tmp;
651 	LIST_HEAD(reqs);
652 	struct nfs_commit_info cinfo;
653 	LIST_HEAD(failed);
654 	int i;
655 
656 	nfs_init_cinfo_from_dreq(&cinfo, dreq);
657 	nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
658 
659 	dreq->count = 0;
660 	for (i = 0; i < dreq->mirror_count; i++)
661 		dreq->mirrors[i].count = 0;
662 	get_dreq(dreq);
663 
664 	nfs_pageio_init_write(&desc, dreq->inode, FLUSH_STABLE, false,
665 			      &nfs_direct_write_completion_ops);
666 	desc.pg_dreq = dreq;
667 
668 	req = nfs_list_entry(reqs.next);
669 	nfs_direct_setup_mirroring(dreq, &desc, req);
670 
671 	list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
672 		if (!nfs_pageio_add_request(&desc, req)) {
673 			nfs_list_remove_request(req);
674 			nfs_list_add_request(req, &failed);
675 			spin_lock(cinfo.lock);
676 			dreq->flags = 0;
677 			dreq->error = -EIO;
678 			spin_unlock(cinfo.lock);
679 		}
680 		nfs_release_request(req);
681 	}
682 	nfs_pageio_complete(&desc);
683 
684 	while (!list_empty(&failed)) {
685 		req = nfs_list_entry(failed.next);
686 		nfs_list_remove_request(req);
687 		nfs_unlock_and_release_request(req);
688 	}
689 
690 	if (put_dreq(dreq))
691 		nfs_direct_write_complete(dreq, dreq->inode);
692 }
693 
694 static void nfs_direct_commit_complete(struct nfs_commit_data *data)
695 {
696 	struct nfs_direct_req *dreq = data->dreq;
697 	struct nfs_commit_info cinfo;
698 	struct nfs_page *req;
699 	int status = data->task.tk_status;
700 
701 	nfs_init_cinfo_from_dreq(&cinfo, dreq);
702 	if (status < 0) {
703 		dprintk("NFS: %5u commit failed with error %d.\n",
704 			data->task.tk_pid, status);
705 		dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
706 	} else if (nfs_direct_cmp_commit_data_verf(dreq, data)) {
707 		dprintk("NFS: %5u commit verify failed\n", data->task.tk_pid);
708 		dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
709 	}
710 
711 	dprintk("NFS: %5u commit returned %d\n", data->task.tk_pid, status);
712 	while (!list_empty(&data->pages)) {
713 		req = nfs_list_entry(data->pages.next);
714 		nfs_list_remove_request(req);
715 		if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES) {
716 			/* Note the rewrite will go through mds */
717 			nfs_mark_request_commit(req, NULL, &cinfo, 0);
718 		} else
719 			nfs_release_request(req);
720 		nfs_unlock_and_release_request(req);
721 	}
722 
723 	if (atomic_dec_and_test(&cinfo.mds->rpcs_out))
724 		nfs_direct_write_complete(dreq, data->inode);
725 }
726 
727 static void nfs_direct_error_cleanup(struct nfs_inode *nfsi)
728 {
729 	/* There is no lock to clear */
730 }
731 
732 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = {
733 	.completion = nfs_direct_commit_complete,
734 	.error_cleanup = nfs_direct_error_cleanup,
735 };
736 
737 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
738 {
739 	int res;
740 	struct nfs_commit_info cinfo;
741 	LIST_HEAD(mds_list);
742 
743 	nfs_init_cinfo_from_dreq(&cinfo, dreq);
744 	nfs_scan_commit(dreq->inode, &mds_list, &cinfo);
745 	res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo);
746 	if (res < 0) /* res == -ENOMEM */
747 		nfs_direct_write_reschedule(dreq);
748 }
749 
750 static void nfs_direct_write_schedule_work(struct work_struct *work)
751 {
752 	struct nfs_direct_req *dreq = container_of(work, struct nfs_direct_req, work);
753 	int flags = dreq->flags;
754 
755 	dreq->flags = 0;
756 	switch (flags) {
757 		case NFS_ODIRECT_DO_COMMIT:
758 			nfs_direct_commit_schedule(dreq);
759 			break;
760 		case NFS_ODIRECT_RESCHED_WRITES:
761 			nfs_direct_write_reschedule(dreq);
762 			break;
763 		default:
764 			nfs_direct_complete(dreq, true);
765 	}
766 }
767 
768 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
769 {
770 	schedule_work(&dreq->work); /* Calls nfs_direct_write_schedule_work */
771 }
772 
773 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
774 {
775 	struct nfs_direct_req *dreq = hdr->dreq;
776 	struct nfs_commit_info cinfo;
777 	bool request_commit = false;
778 	struct nfs_page *req = nfs_list_entry(hdr->pages.next);
779 
780 	if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
781 		goto out_put;
782 
783 	nfs_init_cinfo_from_dreq(&cinfo, dreq);
784 
785 	spin_lock(&dreq->lock);
786 
787 	if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
788 		dreq->flags = 0;
789 		dreq->error = hdr->error;
790 	}
791 	if (dreq->error == 0) {
792 		nfs_direct_good_bytes(dreq, hdr);
793 		if (nfs_write_need_commit(hdr)) {
794 			if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES)
795 				request_commit = true;
796 			else if (dreq->flags == 0) {
797 				nfs_direct_set_hdr_verf(dreq, hdr);
798 				request_commit = true;
799 				dreq->flags = NFS_ODIRECT_DO_COMMIT;
800 			} else if (dreq->flags == NFS_ODIRECT_DO_COMMIT) {
801 				request_commit = true;
802 				if (nfs_direct_set_or_cmp_hdr_verf(dreq, hdr))
803 					dreq->flags =
804 						NFS_ODIRECT_RESCHED_WRITES;
805 			}
806 		}
807 	}
808 	spin_unlock(&dreq->lock);
809 
810 	while (!list_empty(&hdr->pages)) {
811 
812 		req = nfs_list_entry(hdr->pages.next);
813 		nfs_list_remove_request(req);
814 		if (request_commit) {
815 			kref_get(&req->wb_kref);
816 			nfs_mark_request_commit(req, hdr->lseg, &cinfo,
817 				hdr->ds_commit_idx);
818 		}
819 		nfs_unlock_and_release_request(req);
820 	}
821 
822 out_put:
823 	if (put_dreq(dreq))
824 		nfs_direct_write_complete(dreq, hdr->inode);
825 	hdr->release(hdr);
826 }
827 
828 static void nfs_write_sync_pgio_error(struct list_head *head)
829 {
830 	struct nfs_page *req;
831 
832 	while (!list_empty(head)) {
833 		req = nfs_list_entry(head->next);
834 		nfs_list_remove_request(req);
835 		nfs_unlock_and_release_request(req);
836 	}
837 }
838 
839 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
840 	.error_cleanup = nfs_write_sync_pgio_error,
841 	.init_hdr = nfs_direct_pgio_init,
842 	.completion = nfs_direct_write_completion,
843 };
844 
845 
846 /*
847  * NB: Return the value of the first error return code.  Subsequent
848  *     errors after the first one are ignored.
849  */
850 /*
851  * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
852  * operation.  If nfs_writedata_alloc() or get_user_pages() fails,
853  * bail and stop sending more writes.  Write length accounting is
854  * handled automatically by nfs_direct_write_result().  Otherwise, if
855  * no requests have been sent, just return an error.
856  */
857 static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
858 					       struct iov_iter *iter,
859 					       loff_t pos)
860 {
861 	struct nfs_pageio_descriptor desc;
862 	struct inode *inode = dreq->inode;
863 	ssize_t result = 0;
864 	size_t requested_bytes = 0;
865 	size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE);
866 
867 	nfs_pageio_init_write(&desc, inode, FLUSH_COND_STABLE, false,
868 			      &nfs_direct_write_completion_ops);
869 	desc.pg_dreq = dreq;
870 	get_dreq(dreq);
871 	inode_dio_begin(inode);
872 
873 	NFS_I(inode)->write_io += iov_iter_count(iter);
874 	while (iov_iter_count(iter)) {
875 		struct page **pagevec;
876 		size_t bytes;
877 		size_t pgbase;
878 		unsigned npages, i;
879 
880 		result = iov_iter_get_pages_alloc(iter, &pagevec,
881 						  wsize, &pgbase);
882 		if (result < 0)
883 			break;
884 
885 		bytes = result;
886 		iov_iter_advance(iter, bytes);
887 		npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
888 		for (i = 0; i < npages; i++) {
889 			struct nfs_page *req;
890 			unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
891 
892 			req = nfs_create_request(dreq->ctx, pagevec[i], NULL,
893 						 pgbase, req_len);
894 			if (IS_ERR(req)) {
895 				result = PTR_ERR(req);
896 				break;
897 			}
898 
899 			nfs_direct_setup_mirroring(dreq, &desc, req);
900 
901 			nfs_lock_request(req);
902 			req->wb_index = pos >> PAGE_SHIFT;
903 			req->wb_offset = pos & ~PAGE_MASK;
904 			if (!nfs_pageio_add_request(&desc, req)) {
905 				result = desc.pg_error;
906 				nfs_unlock_and_release_request(req);
907 				break;
908 			}
909 			pgbase = 0;
910 			bytes -= req_len;
911 			requested_bytes += req_len;
912 			pos += req_len;
913 			dreq->bytes_left -= req_len;
914 		}
915 		nfs_direct_release_pages(pagevec, npages);
916 		kvfree(pagevec);
917 		if (result < 0)
918 			break;
919 	}
920 	nfs_pageio_complete(&desc);
921 
922 	/*
923 	 * If no bytes were started, return the error, and let the
924 	 * generic layer handle the completion.
925 	 */
926 	if (requested_bytes == 0) {
927 		inode_dio_end(inode);
928 		nfs_direct_req_release(dreq);
929 		return result < 0 ? result : -EIO;
930 	}
931 
932 	if (put_dreq(dreq))
933 		nfs_direct_write_complete(dreq, dreq->inode);
934 	return 0;
935 }
936 
937 /**
938  * nfs_file_direct_write - file direct write operation for NFS files
939  * @iocb: target I/O control block
940  * @iter: vector of user buffers from which to write data
941  * @pos: byte offset in file where writing starts
942  *
943  * We use this function for direct writes instead of calling
944  * generic_file_aio_write() in order to avoid taking the inode
945  * semaphore and updating the i_size.  The NFS server will set
946  * the new i_size and this client must read the updated size
947  * back into its cache.  We let the server do generic write
948  * parameter checking and report problems.
949  *
950  * We eliminate local atime updates, see direct read above.
951  *
952  * We avoid unnecessary page cache invalidations for normal cached
953  * readers of this file.
954  *
955  * Note that O_APPEND is not supported for NFS direct writes, as there
956  * is no atomic O_APPEND write facility in the NFS protocol.
957  */
958 ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
959 {
960 	ssize_t result = -EINVAL;
961 	struct file *file = iocb->ki_filp;
962 	struct address_space *mapping = file->f_mapping;
963 	struct inode *inode = mapping->host;
964 	struct nfs_direct_req *dreq;
965 	struct nfs_lock_context *l_ctx;
966 	loff_t pos, end;
967 
968 	dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
969 		file, iov_iter_count(iter), (long long) iocb->ki_pos);
970 
971 	nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES,
972 		      iov_iter_count(iter));
973 
974 	pos = iocb->ki_pos;
975 	end = (pos + iov_iter_count(iter) - 1) >> PAGE_CACHE_SHIFT;
976 
977 	mutex_lock(&inode->i_mutex);
978 
979 	result = nfs_sync_mapping(mapping);
980 	if (result)
981 		goto out_unlock;
982 
983 	if (mapping->nrpages) {
984 		result = invalidate_inode_pages2_range(mapping,
985 					pos >> PAGE_CACHE_SHIFT, end);
986 		if (result)
987 			goto out_unlock;
988 	}
989 
990 	task_io_account_write(iov_iter_count(iter));
991 
992 	result = -ENOMEM;
993 	dreq = nfs_direct_req_alloc();
994 	if (!dreq)
995 		goto out_unlock;
996 
997 	dreq->inode = inode;
998 	dreq->bytes_left = iov_iter_count(iter);
999 	dreq->io_start = pos;
1000 	dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
1001 	l_ctx = nfs_get_lock_context(dreq->ctx);
1002 	if (IS_ERR(l_ctx)) {
1003 		result = PTR_ERR(l_ctx);
1004 		goto out_release;
1005 	}
1006 	dreq->l_ctx = l_ctx;
1007 	if (!is_sync_kiocb(iocb))
1008 		dreq->iocb = iocb;
1009 
1010 	result = nfs_direct_write_schedule_iovec(dreq, iter, pos);
1011 
1012 	if (mapping->nrpages) {
1013 		invalidate_inode_pages2_range(mapping,
1014 					      pos >> PAGE_CACHE_SHIFT, end);
1015 	}
1016 
1017 	mutex_unlock(&inode->i_mutex);
1018 
1019 	if (!result) {
1020 		result = nfs_direct_wait(dreq);
1021 		if (result > 0) {
1022 			struct inode *inode = mapping->host;
1023 
1024 			iocb->ki_pos = pos + result;
1025 			spin_lock(&inode->i_lock);
1026 			if (i_size_read(inode) < iocb->ki_pos)
1027 				i_size_write(inode, iocb->ki_pos);
1028 			spin_unlock(&inode->i_lock);
1029 			generic_write_sync(file, pos, result);
1030 		}
1031 	}
1032 	nfs_direct_req_release(dreq);
1033 	return result;
1034 
1035 out_release:
1036 	nfs_direct_req_release(dreq);
1037 out_unlock:
1038 	mutex_unlock(&inode->i_mutex);
1039 	return result;
1040 }
1041 
1042 /**
1043  * nfs_init_directcache - create a slab cache for nfs_direct_req structures
1044  *
1045  */
1046 int __init nfs_init_directcache(void)
1047 {
1048 	nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
1049 						sizeof(struct nfs_direct_req),
1050 						0, (SLAB_RECLAIM_ACCOUNT|
1051 							SLAB_MEM_SPREAD),
1052 						NULL);
1053 	if (nfs_direct_cachep == NULL)
1054 		return -ENOMEM;
1055 
1056 	return 0;
1057 }
1058 
1059 /**
1060  * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
1061  *
1062  */
1063 void nfs_destroy_directcache(void)
1064 {
1065 	kmem_cache_destroy(nfs_direct_cachep);
1066 }
1067