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TOMOYO Linux Cross Reference
Linux/fs/nfs/direct.c

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  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                                 max_count,      /* max expected count */
 91                                 bytes_left,     /* bytes left to be sent */
 92                                 io_start,       /* start of IO */
 93                                 error;          /* any reported error */
 94         struct completion       completion;     /* wait for i/o completion */
 95 
 96         /* commit state */
 97         struct nfs_mds_commit_info mds_cinfo;   /* Storage for cinfo */
 98         struct pnfs_ds_commit_info ds_cinfo;    /* Storage for cinfo */
 99         struct work_struct      work;
100         int                     flags;
101 #define NFS_ODIRECT_DO_COMMIT           (1)     /* an unstable reply was received */
102 #define NFS_ODIRECT_RESCHED_WRITES      (2)     /* write verification failed */
103         struct nfs_writeverf    verf;           /* unstable write verifier */
104 };
105 
106 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops;
107 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops;
108 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode);
109 static void nfs_direct_write_schedule_work(struct work_struct *work);
110 
111 static inline void get_dreq(struct nfs_direct_req *dreq)
112 {
113         atomic_inc(&dreq->io_count);
114 }
115 
116 static inline int put_dreq(struct nfs_direct_req *dreq)
117 {
118         return atomic_dec_and_test(&dreq->io_count);
119 }
120 
121 static void
122 nfs_direct_good_bytes(struct nfs_direct_req *dreq, struct nfs_pgio_header *hdr)
123 {
124         int i;
125         ssize_t count;
126 
127         WARN_ON_ONCE(dreq->count >= dreq->max_count);
128 
129         if (dreq->mirror_count == 1) {
130                 dreq->mirrors[hdr->pgio_mirror_idx].count += hdr->good_bytes;
131                 dreq->count += hdr->good_bytes;
132         } else {
133                 /* mirrored writes */
134                 count = dreq->mirrors[hdr->pgio_mirror_idx].count;
135                 if (count + dreq->io_start < hdr->io_start + hdr->good_bytes) {
136                         count = hdr->io_start + hdr->good_bytes - dreq->io_start;
137                         dreq->mirrors[hdr->pgio_mirror_idx].count = count;
138                 }
139                 /* update the dreq->count by finding the minimum agreed count from all
140                  * mirrors */
141                 count = dreq->mirrors[0].count;
142 
143                 for (i = 1; i < dreq->mirror_count; i++)
144                         count = min(count, dreq->mirrors[i].count);
145 
146                 dreq->count = count;
147         }
148 }
149 
150 /*
151  * nfs_direct_select_verf - select the right verifier
152  * @dreq - direct request possibly spanning multiple servers
153  * @ds_clp - nfs_client of data server or NULL if MDS / non-pnfs
154  * @commit_idx - commit bucket index for the DS
155  *
156  * returns the correct verifier to use given the role of the server
157  */
158 static struct nfs_writeverf *
159 nfs_direct_select_verf(struct nfs_direct_req *dreq,
160                        struct nfs_client *ds_clp,
161                        int commit_idx)
162 {
163         struct nfs_writeverf *verfp = &dreq->verf;
164 
165 #ifdef CONFIG_NFS_V4_1
166         /*
167          * pNFS is in use, use the DS verf except commit_through_mds is set
168          * for layout segment where nbuckets is zero.
169          */
170         if (ds_clp && dreq->ds_cinfo.nbuckets > 0) {
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 static int nfs_direct_cmp_verf(const struct nfs_writeverf *v1,
200                 const struct nfs_writeverf *v2)
201 {
202         return nfs_write_verifier_cmp(&v1->verifier, &v2->verifier);
203 }
204 
205 /*
206  * nfs_direct_cmp_hdr_verf - compare verifier for pgio header
207  * @dreq - direct request possibly spanning multiple servers
208  * @hdr - pageio header to validate against previously seen verf
209  *
210  * set the server's "seen" verf if not initialized.
211  * returns result of comparison between @hdr->verf and the "seen"
212  * verf of the server used by @hdr (DS or MDS)
213  */
214 static int nfs_direct_set_or_cmp_hdr_verf(struct nfs_direct_req *dreq,
215                                           struct nfs_pgio_header *hdr)
216 {
217         struct nfs_writeverf *verfp;
218 
219         verfp = nfs_direct_select_verf(dreq, hdr->ds_clp, hdr->ds_commit_idx);
220         if (verfp->committed < 0) {
221                 nfs_direct_set_hdr_verf(dreq, hdr);
222                 return 0;
223         }
224         return nfs_direct_cmp_verf(verfp, &hdr->verf);
225 }
226 
227 /*
228  * nfs_direct_cmp_commit_data_verf - compare verifier for commit data
229  * @dreq - direct request possibly spanning multiple servers
230  * @data - commit data to validate against previously seen verf
231  *
232  * returns result of comparison between @data->verf and the verf of
233  * the server used by @data (DS or MDS)
234  */
235 static int nfs_direct_cmp_commit_data_verf(struct nfs_direct_req *dreq,
236                                            struct nfs_commit_data *data)
237 {
238         struct nfs_writeverf *verfp;
239 
240         verfp = nfs_direct_select_verf(dreq, data->ds_clp,
241                                          data->ds_commit_index);
242 
243         /* verifier not set so always fail */
244         if (verfp->committed < 0)
245                 return 1;
246 
247         return nfs_direct_cmp_verf(verfp, &data->verf);
248 }
249 
250 /**
251  * nfs_direct_IO - NFS address space operation for direct I/O
252  * @iocb: target I/O control block
253  * @iter: I/O buffer
254  *
255  * The presence of this routine in the address space ops vector means
256  * the NFS client supports direct I/O. However, for most direct IO, we
257  * shunt off direct read and write requests before the VFS gets them,
258  * so this method is only ever called for swap.
259  */
260 ssize_t nfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
261 {
262         struct inode *inode = iocb->ki_filp->f_mapping->host;
263 
264         /* we only support swap file calling nfs_direct_IO */
265         if (!IS_SWAPFILE(inode))
266                 return 0;
267 
268         VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE);
269 
270         if (iov_iter_rw(iter) == READ)
271                 return nfs_file_direct_read(iocb, iter);
272         return nfs_file_direct_write(iocb, iter);
273 }
274 
275 static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
276 {
277         unsigned int i;
278         for (i = 0; i < npages; i++)
279                 put_page(pages[i]);
280 }
281 
282 void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
283                               struct nfs_direct_req *dreq)
284 {
285         cinfo->inode = dreq->inode;
286         cinfo->mds = &dreq->mds_cinfo;
287         cinfo->ds = &dreq->ds_cinfo;
288         cinfo->dreq = dreq;
289         cinfo->completion_ops = &nfs_direct_commit_completion_ops;
290 }
291 
292 static inline void nfs_direct_setup_mirroring(struct nfs_direct_req *dreq,
293                                              struct nfs_pageio_descriptor *pgio,
294                                              struct nfs_page *req)
295 {
296         int mirror_count = 1;
297 
298         if (pgio->pg_ops->pg_get_mirror_count)
299                 mirror_count = pgio->pg_ops->pg_get_mirror_count(pgio, req);
300 
301         dreq->mirror_count = mirror_count;
302 }
303 
304 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
305 {
306         struct nfs_direct_req *dreq;
307 
308         dreq = kmem_cache_zalloc(nfs_direct_cachep, GFP_KERNEL);
309         if (!dreq)
310                 return NULL;
311 
312         kref_init(&dreq->kref);
313         kref_get(&dreq->kref);
314         init_completion(&dreq->completion);
315         INIT_LIST_HEAD(&dreq->mds_cinfo.list);
316         dreq->verf.committed = NFS_INVALID_STABLE_HOW;  /* not set yet */
317         INIT_WORK(&dreq->work, nfs_direct_write_schedule_work);
318         dreq->mirror_count = 1;
319         spin_lock_init(&dreq->lock);
320 
321         return dreq;
322 }
323 
324 static void nfs_direct_req_free(struct kref *kref)
325 {
326         struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
327 
328         nfs_free_pnfs_ds_cinfo(&dreq->ds_cinfo);
329         if (dreq->l_ctx != NULL)
330                 nfs_put_lock_context(dreq->l_ctx);
331         if (dreq->ctx != NULL)
332                 put_nfs_open_context(dreq->ctx);
333         kmem_cache_free(nfs_direct_cachep, dreq);
334 }
335 
336 static void nfs_direct_req_release(struct nfs_direct_req *dreq)
337 {
338         kref_put(&dreq->kref, nfs_direct_req_free);
339 }
340 
341 ssize_t nfs_dreq_bytes_left(struct nfs_direct_req *dreq)
342 {
343         return dreq->bytes_left;
344 }
345 EXPORT_SYMBOL_GPL(nfs_dreq_bytes_left);
346 
347 /*
348  * Collects and returns the final error value/byte-count.
349  */
350 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
351 {
352         ssize_t result = -EIOCBQUEUED;
353 
354         /* Async requests don't wait here */
355         if (dreq->iocb)
356                 goto out;
357 
358         result = wait_for_completion_killable(&dreq->completion);
359 
360         if (!result) {
361                 result = dreq->count;
362                 WARN_ON_ONCE(dreq->count < 0);
363         }
364         if (!result)
365                 result = dreq->error;
366 
367 out:
368         return (ssize_t) result;
369 }
370 
371 /*
372  * Synchronous I/O uses a stack-allocated iocb.  Thus we can't trust
373  * the iocb is still valid here if this is a synchronous request.
374  */
375 static void nfs_direct_complete(struct nfs_direct_req *dreq)
376 {
377         struct inode *inode = dreq->inode;
378 
379         inode_dio_end(inode);
380 
381         if (dreq->iocb) {
382                 long res = (long) dreq->error;
383                 if (dreq->count != 0) {
384                         res = (long) dreq->count;
385                         WARN_ON_ONCE(dreq->count < 0);
386                 }
387                 dreq->iocb->ki_complete(dreq->iocb, res, 0);
388         }
389 
390         complete_all(&dreq->completion);
391 
392         nfs_direct_req_release(dreq);
393 }
394 
395 static void nfs_direct_readpage_release(struct nfs_page *req)
396 {
397         dprintk("NFS: direct read done (%s/%llu %d@%lld)\n",
398                 req->wb_context->dentry->d_sb->s_id,
399                 (unsigned long long)NFS_FILEID(d_inode(req->wb_context->dentry)),
400                 req->wb_bytes,
401                 (long long)req_offset(req));
402         nfs_release_request(req);
403 }
404 
405 static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
406 {
407         unsigned long bytes = 0;
408         struct nfs_direct_req *dreq = hdr->dreq;
409 
410         if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
411                 goto out_put;
412 
413         spin_lock(&dreq->lock);
414         if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) && (hdr->good_bytes == 0))
415                 dreq->error = hdr->error;
416         else
417                 nfs_direct_good_bytes(dreq, hdr);
418 
419         spin_unlock(&dreq->lock);
420 
421         while (!list_empty(&hdr->pages)) {
422                 struct nfs_page *req = nfs_list_entry(hdr->pages.next);
423                 struct page *page = req->wb_page;
424 
425                 if (!PageCompound(page) && bytes < hdr->good_bytes)
426                         set_page_dirty(page);
427                 bytes += req->wb_bytes;
428                 nfs_list_remove_request(req);
429                 nfs_direct_readpage_release(req);
430         }
431 out_put:
432         if (put_dreq(dreq))
433                 nfs_direct_complete(dreq);
434         hdr->release(hdr);
435 }
436 
437 static void nfs_read_sync_pgio_error(struct list_head *head)
438 {
439         struct nfs_page *req;
440 
441         while (!list_empty(head)) {
442                 req = nfs_list_entry(head->next);
443                 nfs_list_remove_request(req);
444                 nfs_release_request(req);
445         }
446 }
447 
448 static void nfs_direct_pgio_init(struct nfs_pgio_header *hdr)
449 {
450         get_dreq(hdr->dreq);
451 }
452 
453 static const struct nfs_pgio_completion_ops nfs_direct_read_completion_ops = {
454         .error_cleanup = nfs_read_sync_pgio_error,
455         .init_hdr = nfs_direct_pgio_init,
456         .completion = nfs_direct_read_completion,
457 };
458 
459 /*
460  * For each rsize'd chunk of the user's buffer, dispatch an NFS READ
461  * operation.  If nfs_readdata_alloc() or get_user_pages() fails,
462  * bail and stop sending more reads.  Read length accounting is
463  * handled automatically by nfs_direct_read_result().  Otherwise, if
464  * no requests have been sent, just return an error.
465  */
466 
467 static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
468                                               struct iov_iter *iter,
469                                               loff_t pos)
470 {
471         struct nfs_pageio_descriptor desc;
472         struct inode *inode = dreq->inode;
473         ssize_t result = -EINVAL;
474         size_t requested_bytes = 0;
475         size_t rsize = max_t(size_t, NFS_SERVER(inode)->rsize, PAGE_SIZE);
476 
477         nfs_pageio_init_read(&desc, dreq->inode, false,
478                              &nfs_direct_read_completion_ops);
479         get_dreq(dreq);
480         desc.pg_dreq = dreq;
481         inode_dio_begin(inode);
482 
483         while (iov_iter_count(iter)) {
484                 struct page **pagevec;
485                 size_t bytes;
486                 size_t pgbase;
487                 unsigned npages, i;
488 
489                 result = iov_iter_get_pages_alloc(iter, &pagevec, 
490                                                   rsize, &pgbase);
491                 if (result < 0)
492                         break;
493         
494                 bytes = result;
495                 iov_iter_advance(iter, bytes);
496                 npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
497                 for (i = 0; i < npages; i++) {
498                         struct nfs_page *req;
499                         unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
500                         /* XXX do we need to do the eof zeroing found in async_filler? */
501                         req = nfs_create_request(dreq->ctx, pagevec[i], NULL,
502                                                  pgbase, req_len);
503                         if (IS_ERR(req)) {
504                                 result = PTR_ERR(req);
505                                 break;
506                         }
507                         req->wb_index = pos >> PAGE_SHIFT;
508                         req->wb_offset = pos & ~PAGE_MASK;
509                         if (!nfs_pageio_add_request(&desc, req)) {
510                                 result = desc.pg_error;
511                                 nfs_release_request(req);
512                                 break;
513                         }
514                         pgbase = 0;
515                         bytes -= req_len;
516                         requested_bytes += req_len;
517                         pos += req_len;
518                         dreq->bytes_left -= req_len;
519                 }
520                 nfs_direct_release_pages(pagevec, npages);
521                 kvfree(pagevec);
522                 if (result < 0)
523                         break;
524         }
525 
526         nfs_pageio_complete(&desc);
527 
528         /*
529          * If no bytes were started, return the error, and let the
530          * generic layer handle the completion.
531          */
532         if (requested_bytes == 0) {
533                 inode_dio_end(inode);
534                 nfs_direct_req_release(dreq);
535                 return result < 0 ? result : -EIO;
536         }
537 
538         if (put_dreq(dreq))
539                 nfs_direct_complete(dreq);
540         return 0;
541 }
542 
543 /**
544  * nfs_file_direct_read - file direct read operation for NFS files
545  * @iocb: target I/O control block
546  * @iter: vector of user buffers into which to read data
547  *
548  * We use this function for direct reads instead of calling
549  * generic_file_aio_read() in order to avoid gfar's check to see if
550  * the request starts before the end of the file.  For that check
551  * to work, we must generate a GETATTR before each direct read, and
552  * even then there is a window between the GETATTR and the subsequent
553  * READ where the file size could change.  Our preference is simply
554  * to do all reads the application wants, and the server will take
555  * care of managing the end of file boundary.
556  *
557  * This function also eliminates unnecessarily updating the file's
558  * atime locally, as the NFS server sets the file's atime, and this
559  * client must read the updated atime from the server back into its
560  * cache.
561  */
562 ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter)
563 {
564         struct file *file = iocb->ki_filp;
565         struct address_space *mapping = file->f_mapping;
566         struct inode *inode = mapping->host;
567         struct nfs_direct_req *dreq;
568         struct nfs_lock_context *l_ctx;
569         ssize_t result = -EINVAL;
570         size_t count = iov_iter_count(iter);
571         nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, count);
572 
573         dfprintk(FILE, "NFS: direct read(%pD2, %zd@%Ld)\n",
574                 file, count, (long long) iocb->ki_pos);
575 
576         result = 0;
577         if (!count)
578                 goto out;
579 
580         task_io_account_read(count);
581 
582         result = -ENOMEM;
583         dreq = nfs_direct_req_alloc();
584         if (dreq == NULL)
585                 goto out;
586 
587         dreq->inode = inode;
588         dreq->bytes_left = dreq->max_count = count;
589         dreq->io_start = iocb->ki_pos;
590         dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
591         l_ctx = nfs_get_lock_context(dreq->ctx);
592         if (IS_ERR(l_ctx)) {
593                 result = PTR_ERR(l_ctx);
594                 goto out_release;
595         }
596         dreq->l_ctx = l_ctx;
597         if (!is_sync_kiocb(iocb))
598                 dreq->iocb = iocb;
599 
600         nfs_start_io_direct(inode);
601 
602         NFS_I(inode)->read_io += count;
603         result = nfs_direct_read_schedule_iovec(dreq, iter, iocb->ki_pos);
604 
605         nfs_end_io_direct(inode);
606 
607         if (!result) {
608                 result = nfs_direct_wait(dreq);
609                 if (result > 0)
610                         iocb->ki_pos += result;
611         }
612 
613 out_release:
614         nfs_direct_req_release(dreq);
615 out:
616         return result;
617 }
618 
619 static void
620 nfs_direct_write_scan_commit_list(struct inode *inode,
621                                   struct list_head *list,
622                                   struct nfs_commit_info *cinfo)
623 {
624         spin_lock(&cinfo->inode->i_lock);
625 #ifdef CONFIG_NFS_V4_1
626         if (cinfo->ds != NULL && cinfo->ds->nwritten != 0)
627                 NFS_SERVER(inode)->pnfs_curr_ld->recover_commit_reqs(list, cinfo);
628 #endif
629         nfs_scan_commit_list(&cinfo->mds->list, list, cinfo, 0);
630         spin_unlock(&cinfo->inode->i_lock);
631 }
632 
633 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
634 {
635         struct nfs_pageio_descriptor desc;
636         struct nfs_page *req, *tmp;
637         LIST_HEAD(reqs);
638         struct nfs_commit_info cinfo;
639         LIST_HEAD(failed);
640         int i;
641 
642         nfs_init_cinfo_from_dreq(&cinfo, dreq);
643         nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
644 
645         dreq->count = 0;
646         dreq->verf.committed = NFS_INVALID_STABLE_HOW;
647         nfs_clear_pnfs_ds_commit_verifiers(&dreq->ds_cinfo);
648         for (i = 0; i < dreq->mirror_count; i++)
649                 dreq->mirrors[i].count = 0;
650         get_dreq(dreq);
651 
652         nfs_pageio_init_write(&desc, dreq->inode, FLUSH_STABLE, false,
653                               &nfs_direct_write_completion_ops);
654         desc.pg_dreq = dreq;
655 
656         req = nfs_list_entry(reqs.next);
657         nfs_direct_setup_mirroring(dreq, &desc, req);
658         if (desc.pg_error < 0) {
659                 list_splice_init(&reqs, &failed);
660                 goto out_failed;
661         }
662 
663         list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
664                 if (!nfs_pageio_add_request(&desc, req)) {
665                         nfs_list_remove_request(req);
666                         nfs_list_add_request(req, &failed);
667                         spin_lock(&cinfo.inode->i_lock);
668                         dreq->flags = 0;
669                         if (desc.pg_error < 0)
670                                 dreq->error = desc.pg_error;
671                         else
672                                 dreq->error = -EIO;
673                         spin_unlock(&cinfo.inode->i_lock);
674                 }
675                 nfs_release_request(req);
676         }
677         nfs_pageio_complete(&desc);
678 
679 out_failed:
680         while (!list_empty(&failed)) {
681                 req = nfs_list_entry(failed.next);
682                 nfs_list_remove_request(req);
683                 nfs_unlock_and_release_request(req);
684         }
685 
686         if (put_dreq(dreq))
687                 nfs_direct_write_complete(dreq, dreq->inode);
688 }
689 
690 static void nfs_direct_commit_complete(struct nfs_commit_data *data)
691 {
692         struct nfs_direct_req *dreq = data->dreq;
693         struct nfs_commit_info cinfo;
694         struct nfs_page *req;
695         int status = data->task.tk_status;
696 
697         nfs_init_cinfo_from_dreq(&cinfo, dreq);
698         if (status < 0) {
699                 dprintk("NFS: %5u commit failed with error %d.\n",
700                         data->task.tk_pid, status);
701                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
702         } else if (nfs_direct_cmp_commit_data_verf(dreq, data)) {
703                 dprintk("NFS: %5u commit verify failed\n", data->task.tk_pid);
704                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
705         }
706 
707         dprintk("NFS: %5u commit returned %d\n", data->task.tk_pid, status);
708         while (!list_empty(&data->pages)) {
709                 req = nfs_list_entry(data->pages.next);
710                 nfs_list_remove_request(req);
711                 if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES) {
712                         /* Note the rewrite will go through mds */
713                         nfs_mark_request_commit(req, NULL, &cinfo, 0);
714                 } else
715                         nfs_release_request(req);
716                 nfs_unlock_and_release_request(req);
717         }
718 
719         if (atomic_dec_and_test(&cinfo.mds->rpcs_out))
720                 nfs_direct_write_complete(dreq, data->inode);
721 }
722 
723 static void nfs_direct_resched_write(struct nfs_commit_info *cinfo,
724                 struct nfs_page *req)
725 {
726         struct nfs_direct_req *dreq = cinfo->dreq;
727 
728         spin_lock(&dreq->lock);
729         dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
730         spin_unlock(&dreq->lock);
731         nfs_mark_request_commit(req, NULL, cinfo, 0);
732 }
733 
734 static const struct nfs_commit_completion_ops nfs_direct_commit_completion_ops = {
735         .completion = nfs_direct_commit_complete,
736         .resched_write = nfs_direct_resched_write,
737 };
738 
739 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
740 {
741         int res;
742         struct nfs_commit_info cinfo;
743         LIST_HEAD(mds_list);
744 
745         nfs_init_cinfo_from_dreq(&cinfo, dreq);
746         nfs_scan_commit(dreq->inode, &mds_list, &cinfo);
747         res = nfs_generic_commit_list(dreq->inode, &mds_list, 0, &cinfo);
748         if (res < 0) /* res == -ENOMEM */
749                 nfs_direct_write_reschedule(dreq);
750 }
751 
752 static void nfs_direct_write_schedule_work(struct work_struct *work)
753 {
754         struct nfs_direct_req *dreq = container_of(work, struct nfs_direct_req, work);
755         int flags = dreq->flags;
756 
757         dreq->flags = 0;
758         switch (flags) {
759                 case NFS_ODIRECT_DO_COMMIT:
760                         nfs_direct_commit_schedule(dreq);
761                         break;
762                 case NFS_ODIRECT_RESCHED_WRITES:
763                         nfs_direct_write_reschedule(dreq);
764                         break;
765                 default:
766                         nfs_zap_mapping(dreq->inode, dreq->inode->i_mapping);
767                         nfs_direct_complete(dreq);
768         }
769 }
770 
771 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
772 {
773         schedule_work(&dreq->work); /* Calls nfs_direct_write_schedule_work */
774 }
775 
776 static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
777 {
778         struct nfs_direct_req *dreq = hdr->dreq;
779         struct nfs_commit_info cinfo;
780         bool request_commit = false;
781         struct nfs_page *req = nfs_list_entry(hdr->pages.next);
782 
783         if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
784                 goto out_put;
785 
786         nfs_init_cinfo_from_dreq(&cinfo, dreq);
787 
788         spin_lock(&dreq->lock);
789 
790         if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
791                 dreq->flags = 0;
792                 dreq->error = hdr->error;
793         }
794         if (dreq->error == 0) {
795                 nfs_direct_good_bytes(dreq, hdr);
796                 if (nfs_write_need_commit(hdr)) {
797                         if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES)
798                                 request_commit = true;
799                         else if (dreq->flags == 0) {
800                                 nfs_direct_set_hdr_verf(dreq, hdr);
801                                 request_commit = true;
802                                 dreq->flags = NFS_ODIRECT_DO_COMMIT;
803                         } else if (dreq->flags == NFS_ODIRECT_DO_COMMIT) {
804                                 request_commit = true;
805                                 if (nfs_direct_set_or_cmp_hdr_verf(dreq, hdr))
806                                         dreq->flags =
807                                                 NFS_ODIRECT_RESCHED_WRITES;
808                         }
809                 }
810         }
811         spin_unlock(&dreq->lock);
812 
813         while (!list_empty(&hdr->pages)) {
814 
815                 req = nfs_list_entry(hdr->pages.next);
816                 nfs_list_remove_request(req);
817                 if (request_commit) {
818                         kref_get(&req->wb_kref);
819                         nfs_mark_request_commit(req, hdr->lseg, &cinfo,
820                                 hdr->ds_commit_idx);
821                 }
822                 nfs_unlock_and_release_request(req);
823         }
824 
825 out_put:
826         if (put_dreq(dreq))
827                 nfs_direct_write_complete(dreq, hdr->inode);
828         hdr->release(hdr);
829 }
830 
831 static void nfs_write_sync_pgio_error(struct list_head *head)
832 {
833         struct nfs_page *req;
834 
835         while (!list_empty(head)) {
836                 req = nfs_list_entry(head->next);
837                 nfs_list_remove_request(req);
838                 nfs_unlock_and_release_request(req);
839         }
840 }
841 
842 static void nfs_direct_write_reschedule_io(struct nfs_pgio_header *hdr)
843 {
844         struct nfs_direct_req *dreq = hdr->dreq;
845 
846         spin_lock(&dreq->lock);
847         if (dreq->error == 0) {
848                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
849                 /* fake unstable write to let common nfs resend pages */
850                 hdr->verf.committed = NFS_UNSTABLE;
851                 hdr->good_bytes = hdr->args.count;
852         }
853         spin_unlock(&dreq->lock);
854 }
855 
856 static const struct nfs_pgio_completion_ops nfs_direct_write_completion_ops = {
857         .error_cleanup = nfs_write_sync_pgio_error,
858         .init_hdr = nfs_direct_pgio_init,
859         .completion = nfs_direct_write_completion,
860         .reschedule_io = nfs_direct_write_reschedule_io,
861 };
862 
863 
864 /*
865  * NB: Return the value of the first error return code.  Subsequent
866  *     errors after the first one are ignored.
867  */
868 /*
869  * For each wsize'd chunk of the user's buffer, dispatch an NFS WRITE
870  * operation.  If nfs_writedata_alloc() or get_user_pages() fails,
871  * bail and stop sending more writes.  Write length accounting is
872  * handled automatically by nfs_direct_write_result().  Otherwise, if
873  * no requests have been sent, just return an error.
874  */
875 static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
876                                                struct iov_iter *iter,
877                                                loff_t pos)
878 {
879         struct nfs_pageio_descriptor desc;
880         struct inode *inode = dreq->inode;
881         ssize_t result = 0;
882         size_t requested_bytes = 0;
883         size_t wsize = max_t(size_t, NFS_SERVER(inode)->wsize, PAGE_SIZE);
884 
885         nfs_pageio_init_write(&desc, inode, FLUSH_COND_STABLE, false,
886                               &nfs_direct_write_completion_ops);
887         desc.pg_dreq = dreq;
888         get_dreq(dreq);
889         inode_dio_begin(inode);
890 
891         NFS_I(inode)->write_io += iov_iter_count(iter);
892         while (iov_iter_count(iter)) {
893                 struct page **pagevec;
894                 size_t bytes;
895                 size_t pgbase;
896                 unsigned npages, i;
897 
898                 result = iov_iter_get_pages_alloc(iter, &pagevec, 
899                                                   wsize, &pgbase);
900                 if (result < 0)
901                         break;
902 
903                 bytes = result;
904                 iov_iter_advance(iter, bytes);
905                 npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
906                 for (i = 0; i < npages; i++) {
907                         struct nfs_page *req;
908                         unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
909 
910                         req = nfs_create_request(dreq->ctx, pagevec[i], NULL,
911                                                  pgbase, req_len);
912                         if (IS_ERR(req)) {
913                                 result = PTR_ERR(req);
914                                 break;
915                         }
916 
917                         nfs_direct_setup_mirroring(dreq, &desc, req);
918                         if (desc.pg_error < 0) {
919                                 nfs_free_request(req);
920                                 result = desc.pg_error;
921                                 break;
922                         }
923 
924                         nfs_lock_request(req);
925                         req->wb_index = pos >> PAGE_SHIFT;
926                         req->wb_offset = pos & ~PAGE_MASK;
927                         if (!nfs_pageio_add_request(&desc, req)) {
928                                 result = desc.pg_error;
929                                 nfs_unlock_and_release_request(req);
930                                 break;
931                         }
932                         pgbase = 0;
933                         bytes -= req_len;
934                         requested_bytes += req_len;
935                         pos += req_len;
936                         dreq->bytes_left -= req_len;
937                 }
938                 nfs_direct_release_pages(pagevec, npages);
939                 kvfree(pagevec);
940                 if (result < 0)
941                         break;
942         }
943         nfs_pageio_complete(&desc);
944 
945         /*
946          * If no bytes were started, return the error, and let the
947          * generic layer handle the completion.
948          */
949         if (requested_bytes == 0) {
950                 inode_dio_end(inode);
951                 nfs_direct_req_release(dreq);
952                 return result < 0 ? result : -EIO;
953         }
954 
955         if (put_dreq(dreq))
956                 nfs_direct_write_complete(dreq, dreq->inode);
957         return 0;
958 }
959 
960 /**
961  * nfs_file_direct_write - file direct write operation for NFS files
962  * @iocb: target I/O control block
963  * @iter: vector of user buffers from which to write data
964  *
965  * We use this function for direct writes instead of calling
966  * generic_file_aio_write() in order to avoid taking the inode
967  * semaphore and updating the i_size.  The NFS server will set
968  * the new i_size and this client must read the updated size
969  * back into its cache.  We let the server do generic write
970  * parameter checking and report problems.
971  *
972  * We eliminate local atime updates, see direct read above.
973  *
974  * We avoid unnecessary page cache invalidations for normal cached
975  * readers of this file.
976  *
977  * Note that O_APPEND is not supported for NFS direct writes, as there
978  * is no atomic O_APPEND write facility in the NFS protocol.
979  */
980 ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
981 {
982         ssize_t result = -EINVAL;
983         size_t count;
984         struct file *file = iocb->ki_filp;
985         struct address_space *mapping = file->f_mapping;
986         struct inode *inode = mapping->host;
987         struct nfs_direct_req *dreq;
988         struct nfs_lock_context *l_ctx;
989         loff_t pos, end;
990 
991         dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
992                 file, iov_iter_count(iter), (long long) iocb->ki_pos);
993 
994         result = generic_write_checks(iocb, iter);
995         if (result <= 0)
996                 return result;
997         count = result;
998         nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
999 
1000         pos = iocb->ki_pos;
1001         end = (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT;
1002 
1003         task_io_account_write(count);
1004 
1005         result = -ENOMEM;
1006         dreq = nfs_direct_req_alloc();
1007         if (!dreq)
1008                 goto out;
1009 
1010         dreq->inode = inode;
1011         dreq->bytes_left = dreq->max_count = count;
1012         dreq->io_start = pos;
1013         dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
1014         l_ctx = nfs_get_lock_context(dreq->ctx);
1015         if (IS_ERR(l_ctx)) {
1016                 result = PTR_ERR(l_ctx);
1017                 goto out_release;
1018         }
1019         dreq->l_ctx = l_ctx;
1020         if (!is_sync_kiocb(iocb))
1021                 dreq->iocb = iocb;
1022 
1023         nfs_start_io_direct(inode);
1024 
1025         result = nfs_direct_write_schedule_iovec(dreq, iter, pos);
1026 
1027         if (mapping->nrpages) {
1028                 invalidate_inode_pages2_range(mapping,
1029                                               pos >> PAGE_SHIFT, end);
1030         }
1031 
1032         nfs_end_io_direct(inode);
1033 
1034         if (!result) {
1035                 result = nfs_direct_wait(dreq);
1036                 if (result > 0) {
1037                         iocb->ki_pos = pos + result;
1038                         /* XXX: should check the generic_write_sync retval */
1039                         generic_write_sync(iocb, result);
1040                 }
1041         }
1042 out_release:
1043         nfs_direct_req_release(dreq);
1044 out:
1045         return result;
1046 }
1047 
1048 /**
1049  * nfs_init_directcache - create a slab cache for nfs_direct_req structures
1050  *
1051  */
1052 int __init nfs_init_directcache(void)
1053 {
1054         nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
1055                                                 sizeof(struct nfs_direct_req),
1056                                                 0, (SLAB_RECLAIM_ACCOUNT|
1057                                                         SLAB_MEM_SPREAD),
1058                                                 NULL);
1059         if (nfs_direct_cachep == NULL)
1060                 return -ENOMEM;
1061 
1062         return 0;
1063 }
1064 
1065 /**
1066  * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
1067  *
1068  */
1069 void nfs_destroy_directcache(void)
1070 {
1071         kmem_cache_destroy(nfs_direct_cachep);
1072 }
1073 

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