1 /*
2  * linux/fs/nfs/read.c
3  *
4  * Block I/O for NFS
5  *
6  * Partial copy of Linus' read cache modifications to fs/nfs/file.c
7  * modified for async RPC by okir@monad.swb.de
8  */
9 
10 #include <linux/time.h>
11 #include <linux/kernel.h>
12 #include <linux/errno.h>
13 #include <linux/fcntl.h>
14 #include <linux/stat.h>
15 #include <linux/mm.h>
16 #include <linux/slab.h>
17 #include <linux/pagemap.h>
18 #include <linux/sunrpc/clnt.h>
19 #include <linux/nfs_fs.h>
20 #include <linux/nfs_page.h>
21 #include <linux/module.h>
22 
23 #include "nfs4_fs.h"
24 #include "internal.h"
25 #include "iostat.h"
26 #include "fscache.h"
27 #include "pnfs.h"
28 #include "nfstrace.h"
29 
30 #define NFSDBG_FACILITY		NFSDBG_PAGECACHE
31 
32 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
33 static const struct nfs_rw_ops nfs_rw_read_ops;
34 
35 static struct kmem_cache *nfs_rdata_cachep;
36 
nfs_readhdr_alloc(void)37 static struct nfs_pgio_header *nfs_readhdr_alloc(void)
38 {
39 	struct nfs_pgio_header *p = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
40 
41 	if (p)
42 		p->rw_mode = FMODE_READ;
43 	return p;
44 }
45 
nfs_readhdr_free(struct nfs_pgio_header * rhdr)46 static void nfs_readhdr_free(struct nfs_pgio_header *rhdr)
47 {
48 	kmem_cache_free(nfs_rdata_cachep, rhdr);
49 }
50 
51 static
nfs_return_empty_page(struct page * page)52 int nfs_return_empty_page(struct page *page)
53 {
54 	zero_user(page, 0, PAGE_SIZE);
55 	SetPageUptodate(page);
56 	unlock_page(page);
57 	return 0;
58 }
59 
nfs_pageio_init_read(struct nfs_pageio_descriptor * pgio,struct inode * inode,bool force_mds,const struct nfs_pgio_completion_ops * compl_ops)60 void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
61 			      struct inode *inode, bool force_mds,
62 			      const struct nfs_pgio_completion_ops *compl_ops)
63 {
64 	struct nfs_server *server = NFS_SERVER(inode);
65 	const struct nfs_pageio_ops *pg_ops = &nfs_pgio_rw_ops;
66 
67 #ifdef CONFIG_NFS_V4_1
68 	if (server->pnfs_curr_ld && !force_mds)
69 		pg_ops = server->pnfs_curr_ld->pg_read_ops;
70 #endif
71 	nfs_pageio_init(pgio, inode, pg_ops, compl_ops, &nfs_rw_read_ops,
72 			server->rsize, 0);
73 }
74 EXPORT_SYMBOL_GPL(nfs_pageio_init_read);
75 
nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor * pgio)76 void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
77 {
78 	struct nfs_pgio_mirror *mirror;
79 
80 	if (pgio->pg_ops && pgio->pg_ops->pg_cleanup)
81 		pgio->pg_ops->pg_cleanup(pgio);
82 
83 	pgio->pg_ops = &nfs_pgio_rw_ops;
84 
85 	/* read path should never have more than one mirror */
86 	WARN_ON_ONCE(pgio->pg_mirror_count != 1);
87 
88 	mirror = &pgio->pg_mirrors[0];
89 	mirror->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
90 }
91 EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
92 
nfs_readpage_release(struct nfs_page * req)93 static void nfs_readpage_release(struct nfs_page *req)
94 {
95 	struct inode *inode = d_inode(req->wb_context->dentry);
96 
97 	dprintk("NFS: read done (%s/%llu %d@%lld)\n", inode->i_sb->s_id,
98 		(unsigned long long)NFS_FILEID(inode), req->wb_bytes,
99 		(long long)req_offset(req));
100 
101 	if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE)) {
102 		if (PageUptodate(req->wb_page))
103 			nfs_readpage_to_fscache(inode, req->wb_page, 0);
104 
105 		unlock_page(req->wb_page);
106 	}
107 	nfs_release_request(req);
108 }
109 
nfs_readpage_async(struct nfs_open_context * ctx,struct inode * inode,struct page * page)110 int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
111 		       struct page *page)
112 {
113 	struct nfs_page	*new;
114 	unsigned int len;
115 	struct nfs_pageio_descriptor pgio;
116 	struct nfs_pgio_mirror *pgm;
117 
118 	len = nfs_page_length(page);
119 	if (len == 0)
120 		return nfs_return_empty_page(page);
121 	new = nfs_create_request(ctx, page, NULL, 0, len);
122 	if (IS_ERR(new)) {
123 		unlock_page(page);
124 		return PTR_ERR(new);
125 	}
126 	if (len < PAGE_SIZE)
127 		zero_user_segment(page, len, PAGE_SIZE);
128 
129 	nfs_pageio_init_read(&pgio, inode, false,
130 			     &nfs_async_read_completion_ops);
131 	if (!nfs_pageio_add_request(&pgio, new)) {
132 		nfs_list_remove_request(new);
133 		nfs_readpage_release(new);
134 	}
135 	nfs_pageio_complete(&pgio);
136 
137 	/* It doesn't make sense to do mirrored reads! */
138 	WARN_ON_ONCE(pgio.pg_mirror_count != 1);
139 
140 	pgm = &pgio.pg_mirrors[0];
141 	NFS_I(inode)->read_io += pgm->pg_bytes_written;
142 
143 	return pgio.pg_error < 0 ? pgio.pg_error : 0;
144 }
145 
nfs_page_group_set_uptodate(struct nfs_page * req)146 static void nfs_page_group_set_uptodate(struct nfs_page *req)
147 {
148 	if (nfs_page_group_sync_on_bit(req, PG_UPTODATE))
149 		SetPageUptodate(req->wb_page);
150 }
151 
nfs_read_completion(struct nfs_pgio_header * hdr)152 static void nfs_read_completion(struct nfs_pgio_header *hdr)
153 {
154 	unsigned long bytes = 0;
155 
156 	if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
157 		goto out;
158 	while (!list_empty(&hdr->pages)) {
159 		struct nfs_page *req = nfs_list_entry(hdr->pages.next);
160 		struct page *page = req->wb_page;
161 		unsigned long start = req->wb_pgbase;
162 		unsigned long end = req->wb_pgbase + req->wb_bytes;
163 
164 		if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
165 			/* note: regions of the page not covered by a
166 			 * request are zeroed in nfs_readpage_async /
167 			 * readpage_async_filler */
168 			if (bytes > hdr->good_bytes) {
169 				/* nothing in this request was good, so zero
170 				 * the full extent of the request */
171 				zero_user_segment(page, start, end);
172 
173 			} else if (hdr->good_bytes - bytes < req->wb_bytes) {
174 				/* part of this request has good bytes, but
175 				 * not all. zero the bad bytes */
176 				start += hdr->good_bytes - bytes;
177 				WARN_ON(start < req->wb_pgbase);
178 				zero_user_segment(page, start, end);
179 			}
180 		}
181 		bytes += req->wb_bytes;
182 		if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
183 			if (bytes <= hdr->good_bytes)
184 				nfs_page_group_set_uptodate(req);
185 		} else
186 			nfs_page_group_set_uptodate(req);
187 		nfs_list_remove_request(req);
188 		nfs_readpage_release(req);
189 	}
190 out:
191 	hdr->release(hdr);
192 }
193 
nfs_initiate_read(struct nfs_pgio_header * hdr,struct rpc_message * msg,const struct nfs_rpc_ops * rpc_ops,struct rpc_task_setup * task_setup_data,int how)194 static void nfs_initiate_read(struct nfs_pgio_header *hdr,
195 			      struct rpc_message *msg,
196 			      const struct nfs_rpc_ops *rpc_ops,
197 			      struct rpc_task_setup *task_setup_data, int how)
198 {
199 	struct inode *inode = hdr->inode;
200 	int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;
201 
202 	task_setup_data->flags |= swap_flags;
203 	rpc_ops->read_setup(hdr, msg);
204 	trace_nfs_initiate_read(inode, hdr->io_start, hdr->good_bytes);
205 }
206 
207 static void
nfs_async_read_error(struct list_head * head,int error)208 nfs_async_read_error(struct list_head *head, int error)
209 {
210 	struct nfs_page	*req;
211 
212 	while (!list_empty(head)) {
213 		req = nfs_list_entry(head->next);
214 		nfs_list_remove_request(req);
215 		nfs_readpage_release(req);
216 	}
217 }
218 
219 static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
220 	.error_cleanup = nfs_async_read_error,
221 	.completion = nfs_read_completion,
222 };
223 
224 /*
225  * This is the callback from RPC telling us whether a reply was
226  * received or some error occurred (timeout or socket shutdown).
227  */
nfs_readpage_done(struct rpc_task * task,struct nfs_pgio_header * hdr,struct inode * inode)228 static int nfs_readpage_done(struct rpc_task *task,
229 			     struct nfs_pgio_header *hdr,
230 			     struct inode *inode)
231 {
232 	int status = NFS_PROTO(inode)->read_done(task, hdr);
233 	if (status != 0)
234 		return status;
235 
236 	nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, hdr->res.count);
237 	trace_nfs_readpage_done(inode, task->tk_status,
238 				hdr->args.offset, hdr->res.eof);
239 
240 	if (task->tk_status == -ESTALE) {
241 		set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
242 		nfs_mark_for_revalidate(inode);
243 	}
244 	return 0;
245 }
246 
nfs_readpage_retry(struct rpc_task * task,struct nfs_pgio_header * hdr)247 static void nfs_readpage_retry(struct rpc_task *task,
248 			       struct nfs_pgio_header *hdr)
249 {
250 	struct nfs_pgio_args *argp = &hdr->args;
251 	struct nfs_pgio_res  *resp = &hdr->res;
252 
253 	/* This is a short read! */
254 	nfs_inc_stats(hdr->inode, NFSIOS_SHORTREAD);
255 	/* Has the server at least made some progress? */
256 	if (resp->count == 0) {
257 		nfs_set_pgio_error(hdr, -EIO, argp->offset);
258 		return;
259 	}
260 
261 	/* For non rpc-based layout drivers, retry-through-MDS */
262 	if (!task->tk_ops) {
263 		hdr->pnfs_error = -EAGAIN;
264 		return;
265 	}
266 
267 	/* Yes, so retry the read at the end of the hdr */
268 	hdr->mds_offset += resp->count;
269 	argp->offset += resp->count;
270 	argp->pgbase += resp->count;
271 	argp->count -= resp->count;
272 	rpc_restart_call_prepare(task);
273 }
274 
nfs_readpage_result(struct rpc_task * task,struct nfs_pgio_header * hdr)275 static void nfs_readpage_result(struct rpc_task *task,
276 				struct nfs_pgio_header *hdr)
277 {
278 	if (hdr->res.eof) {
279 		loff_t bound;
280 
281 		bound = hdr->args.offset + hdr->res.count;
282 		spin_lock(&hdr->lock);
283 		if (bound < hdr->io_start + hdr->good_bytes) {
284 			set_bit(NFS_IOHDR_EOF, &hdr->flags);
285 			clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
286 			hdr->good_bytes = bound - hdr->io_start;
287 		}
288 		spin_unlock(&hdr->lock);
289 	} else if (hdr->res.count < hdr->args.count)
290 		nfs_readpage_retry(task, hdr);
291 }
292 
293 /*
294  * Read a page over NFS.
295  * We read the page synchronously in the following case:
296  *  -	The error flag is set for this page. This happens only when a
297  *	previous async read operation failed.
298  */
nfs_readpage(struct file * file,struct page * page)299 int nfs_readpage(struct file *file, struct page *page)
300 {
301 	struct nfs_open_context *ctx;
302 	struct inode *inode = page_file_mapping(page)->host;
303 	int		error;
304 
305 	dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
306 		page, PAGE_SIZE, page_index(page));
307 	nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
308 	nfs_add_stats(inode, NFSIOS_READPAGES, 1);
309 
310 	/*
311 	 * Try to flush any pending writes to the file..
312 	 *
313 	 * NOTE! Because we own the page lock, there cannot
314 	 * be any new pending writes generated at this point
315 	 * for this page (other pages can be written to).
316 	 */
317 	error = nfs_wb_page(inode, page);
318 	if (error)
319 		goto out_unlock;
320 	if (PageUptodate(page))
321 		goto out_unlock;
322 
323 	error = -ESTALE;
324 	if (NFS_STALE(inode))
325 		goto out_unlock;
326 
327 	if (file == NULL) {
328 		error = -EBADF;
329 		ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
330 		if (ctx == NULL)
331 			goto out_unlock;
332 	} else
333 		ctx = get_nfs_open_context(nfs_file_open_context(file));
334 
335 	if (!IS_SYNC(inode)) {
336 		error = nfs_readpage_from_fscache(ctx, inode, page);
337 		if (error == 0)
338 			goto out;
339 	}
340 
341 	error = nfs_readpage_async(ctx, inode, page);
342 
343 out:
344 	put_nfs_open_context(ctx);
345 	return error;
346 out_unlock:
347 	unlock_page(page);
348 	return error;
349 }
350 
351 struct nfs_readdesc {
352 	struct nfs_pageio_descriptor *pgio;
353 	struct nfs_open_context *ctx;
354 };
355 
356 static int
readpage_async_filler(void * data,struct page * page)357 readpage_async_filler(void *data, struct page *page)
358 {
359 	struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
360 	struct nfs_page *new;
361 	unsigned int len;
362 	int error;
363 
364 	len = nfs_page_length(page);
365 	if (len == 0)
366 		return nfs_return_empty_page(page);
367 
368 	new = nfs_create_request(desc->ctx, page, NULL, 0, len);
369 	if (IS_ERR(new))
370 		goto out_error;
371 
372 	if (len < PAGE_SIZE)
373 		zero_user_segment(page, len, PAGE_SIZE);
374 	if (!nfs_pageio_add_request(desc->pgio, new)) {
375 		nfs_list_remove_request(new);
376 		nfs_readpage_release(new);
377 		error = desc->pgio->pg_error;
378 		goto out;
379 	}
380 	return 0;
381 out_error:
382 	error = PTR_ERR(new);
383 	unlock_page(page);
384 out:
385 	return error;
386 }
387 
nfs_readpages(struct file * filp,struct address_space * mapping,struct list_head * pages,unsigned nr_pages)388 int nfs_readpages(struct file *filp, struct address_space *mapping,
389 		struct list_head *pages, unsigned nr_pages)
390 {
391 	struct nfs_pageio_descriptor pgio;
392 	struct nfs_pgio_mirror *pgm;
393 	struct nfs_readdesc desc = {
394 		.pgio = &pgio,
395 	};
396 	struct inode *inode = mapping->host;
397 	unsigned long npages;
398 	int ret = -ESTALE;
399 
400 	dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
401 			inode->i_sb->s_id,
402 			(unsigned long long)NFS_FILEID(inode),
403 			nr_pages);
404 	nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
405 
406 	if (NFS_STALE(inode))
407 		goto out;
408 
409 	if (filp == NULL) {
410 		desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
411 		if (desc.ctx == NULL)
412 			return -EBADF;
413 	} else
414 		desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
415 
416 	/* attempt to read as many of the pages as possible from the cache
417 	 * - this returns -ENOBUFS immediately if the cookie is negative
418 	 */
419 	ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
420 					 pages, &nr_pages);
421 	if (ret == 0)
422 		goto read_complete; /* all pages were read */
423 
424 	nfs_pageio_init_read(&pgio, inode, false,
425 			     &nfs_async_read_completion_ops);
426 
427 	ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
428 	nfs_pageio_complete(&pgio);
429 
430 	/* It doesn't make sense to do mirrored reads! */
431 	WARN_ON_ONCE(pgio.pg_mirror_count != 1);
432 
433 	pgm = &pgio.pg_mirrors[0];
434 	NFS_I(inode)->read_io += pgm->pg_bytes_written;
435 	npages = (pgm->pg_bytes_written + PAGE_SIZE - 1) >>
436 		 PAGE_SHIFT;
437 	nfs_add_stats(inode, NFSIOS_READPAGES, npages);
438 read_complete:
439 	put_nfs_open_context(desc.ctx);
440 out:
441 	return ret;
442 }
443 
nfs_init_readpagecache(void)444 int __init nfs_init_readpagecache(void)
445 {
446 	nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
447 					     sizeof(struct nfs_pgio_header),
448 					     0, SLAB_HWCACHE_ALIGN,
449 					     NULL);
450 	if (nfs_rdata_cachep == NULL)
451 		return -ENOMEM;
452 
453 	return 0;
454 }
455 
nfs_destroy_readpagecache(void)456 void nfs_destroy_readpagecache(void)
457 {
458 	kmem_cache_destroy(nfs_rdata_cachep);
459 }
460 
461 static const struct nfs_rw_ops nfs_rw_read_ops = {
462 	.rw_alloc_header	= nfs_readhdr_alloc,
463 	.rw_free_header		= nfs_readhdr_free,
464 	.rw_done		= nfs_readpage_done,
465 	.rw_result		= nfs_readpage_result,
466 	.rw_initiate		= nfs_initiate_read,
467 };
468