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

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  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 
 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 
 46 static void nfs_readhdr_free(struct nfs_pgio_header *rhdr)
 47 {
 48         kmem_cache_free(nfs_rdata_cachep, rhdr);
 49 }
 50 
 51 static
 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 
 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 
 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 
 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 
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 
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 
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 
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
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  */
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 
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 
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 pos = hdr->args.offset + hdr->res.count;
280                 unsigned int new = pos - hdr->io_start;
281 
282                 if (hdr->good_bytes > new) {
283                         hdr->good_bytes = new;
284                         set_bit(NFS_IOHDR_EOF, &hdr->flags);
285                         clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
286                 }
287         } else if (hdr->res.count < hdr->args.count)
288                 nfs_readpage_retry(task, hdr);
289 }
290 
291 /*
292  * Read a page over NFS.
293  * We read the page synchronously in the following case:
294  *  -   The error flag is set for this page. This happens only when a
295  *      previous async read operation failed.
296  */
297 int nfs_readpage(struct file *file, struct page *page)
298 {
299         struct nfs_open_context *ctx;
300         struct inode *inode = page_file_mapping(page)->host;
301         int             error;
302 
303         dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
304                 page, PAGE_SIZE, page_index(page));
305         nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
306         nfs_add_stats(inode, NFSIOS_READPAGES, 1);
307 
308         /*
309          * Try to flush any pending writes to the file..
310          *
311          * NOTE! Because we own the page lock, there cannot
312          * be any new pending writes generated at this point
313          * for this page (other pages can be written to).
314          */
315         error = nfs_wb_page(inode, page);
316         if (error)
317                 goto out_unlock;
318         if (PageUptodate(page))
319                 goto out_unlock;
320 
321         error = -ESTALE;
322         if (NFS_STALE(inode))
323                 goto out_unlock;
324 
325         if (file == NULL) {
326                 error = -EBADF;
327                 ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
328                 if (ctx == NULL)
329                         goto out_unlock;
330         } else
331                 ctx = get_nfs_open_context(nfs_file_open_context(file));
332 
333         if (!IS_SYNC(inode)) {
334                 error = nfs_readpage_from_fscache(ctx, inode, page);
335                 if (error == 0)
336                         goto out;
337         }
338 
339         error = nfs_readpage_async(ctx, inode, page);
340 
341 out:
342         put_nfs_open_context(ctx);
343         return error;
344 out_unlock:
345         unlock_page(page);
346         return error;
347 }
348 
349 struct nfs_readdesc {
350         struct nfs_pageio_descriptor *pgio;
351         struct nfs_open_context *ctx;
352 };
353 
354 static int
355 readpage_async_filler(void *data, struct page *page)
356 {
357         struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
358         struct nfs_page *new;
359         unsigned int len;
360         int error;
361 
362         len = nfs_page_length(page);
363         if (len == 0)
364                 return nfs_return_empty_page(page);
365 
366         new = nfs_create_request(desc->ctx, page, NULL, 0, len);
367         if (IS_ERR(new))
368                 goto out_error;
369 
370         if (len < PAGE_SIZE)
371                 zero_user_segment(page, len, PAGE_SIZE);
372         if (!nfs_pageio_add_request(desc->pgio, new)) {
373                 nfs_list_remove_request(new);
374                 nfs_readpage_release(new);
375                 error = desc->pgio->pg_error;
376                 goto out;
377         }
378         return 0;
379 out_error:
380         error = PTR_ERR(new);
381         unlock_page(page);
382 out:
383         return error;
384 }
385 
386 int nfs_readpages(struct file *filp, struct address_space *mapping,
387                 struct list_head *pages, unsigned nr_pages)
388 {
389         struct nfs_pageio_descriptor pgio;
390         struct nfs_pgio_mirror *pgm;
391         struct nfs_readdesc desc = {
392                 .pgio = &pgio,
393         };
394         struct inode *inode = mapping->host;
395         unsigned long npages;
396         int ret = -ESTALE;
397 
398         dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
399                         inode->i_sb->s_id,
400                         (unsigned long long)NFS_FILEID(inode),
401                         nr_pages);
402         nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
403 
404         if (NFS_STALE(inode))
405                 goto out;
406 
407         if (filp == NULL) {
408                 desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
409                 if (desc.ctx == NULL)
410                         return -EBADF;
411         } else
412                 desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
413 
414         /* attempt to read as many of the pages as possible from the cache
415          * - this returns -ENOBUFS immediately if the cookie is negative
416          */
417         ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
418                                          pages, &nr_pages);
419         if (ret == 0)
420                 goto read_complete; /* all pages were read */
421 
422         nfs_pageio_init_read(&pgio, inode, false,
423                              &nfs_async_read_completion_ops);
424 
425         ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
426         nfs_pageio_complete(&pgio);
427 
428         /* It doesn't make sense to do mirrored reads! */
429         WARN_ON_ONCE(pgio.pg_mirror_count != 1);
430 
431         pgm = &pgio.pg_mirrors[0];
432         NFS_I(inode)->read_io += pgm->pg_bytes_written;
433         npages = (pgm->pg_bytes_written + PAGE_SIZE - 1) >>
434                  PAGE_SHIFT;
435         nfs_add_stats(inode, NFSIOS_READPAGES, npages);
436 read_complete:
437         put_nfs_open_context(desc.ctx);
438 out:
439         return ret;
440 }
441 
442 int __init nfs_init_readpagecache(void)
443 {
444         nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
445                                              sizeof(struct nfs_pgio_header),
446                                              0, SLAB_HWCACHE_ALIGN,
447                                              NULL);
448         if (nfs_rdata_cachep == NULL)
449                 return -ENOMEM;
450 
451         return 0;
452 }
453 
454 void nfs_destroy_readpagecache(void)
455 {
456         kmem_cache_destroy(nfs_rdata_cachep);
457 }
458 
459 static const struct nfs_rw_ops nfs_rw_read_ops = {
460         .rw_alloc_header        = nfs_readhdr_alloc,
461         .rw_free_header         = nfs_readhdr_free,
462         .rw_done                = nfs_readpage_done,
463         .rw_result              = nfs_readpage_result,
464         .rw_initiate            = nfs_initiate_read,
465 };
466 

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