blob: fade02c15e6ef11a8575e6381b6f10445a1de375 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/nfs/file.c
3 *
4 * Copyright (C) 1992 Rick Sladkey
5 *
6 * Changes Copyright (C) 1994 by Florian La Roche
7 * - Do not copy data too often around in the kernel.
8 * - In nfs_file_read the return value of kmalloc wasn't checked.
9 * - Put in a better version of read look-ahead buffering. Original idea
10 * and implementation by Wai S Kok elekokws@ee.nus.sg.
11 *
12 * Expire cache on write to a file by Wai S Kok (Oct 1994).
13 *
14 * Total rewrite of read side for new NFS buffer cache.. Linus.
15 *
16 * nfs regular file handling functions
17 */
18
19#include <linux/time.h>
20#include <linux/kernel.h>
21#include <linux/errno.h>
22#include <linux/fcntl.h>
23#include <linux/stat.h>
24#include <linux/nfs_fs.h>
25#include <linux/nfs_mount.h>
26#include <linux/mm.h>
27#include <linux/slab.h>
28#include <linux/pagemap.h>
29#include <linux/smp_lock.h>
30
31#include <asm/uaccess.h>
32#include <asm/system.h>
33
34#include "delegation.h"
Chuck Lever91d5b472006-03-20 13:44:14 -050035#include "iostat.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070036
37#define NFSDBG_FACILITY NFSDBG_FILE
38
39static int nfs_file_open(struct inode *, struct file *);
40static int nfs_file_release(struct inode *, struct file *);
Trond Myklebust980802e2005-06-13 11:14:01 -040041static loff_t nfs_file_llseek(struct file *file, loff_t offset, int origin);
Linus Torvalds1da177e2005-04-16 15:20:36 -070042static int nfs_file_mmap(struct file *, struct vm_area_struct *);
43static ssize_t nfs_file_sendfile(struct file *, loff_t *, size_t, read_actor_t, void *);
44static ssize_t nfs_file_read(struct kiocb *, char __user *, size_t, loff_t);
45static ssize_t nfs_file_write(struct kiocb *, const char __user *, size_t, loff_t);
46static int nfs_file_flush(struct file *);
47static int nfs_fsync(struct file *, struct dentry *dentry, int datasync);
48static int nfs_check_flags(int flags);
49static int nfs_lock(struct file *filp, int cmd, struct file_lock *fl);
50static int nfs_flock(struct file *filp, int cmd, struct file_lock *fl);
51
Arjan van de Ven4b6f5d22006-03-28 01:56:42 -080052const struct file_operations nfs_file_operations = {
Trond Myklebust980802e2005-06-13 11:14:01 -040053 .llseek = nfs_file_llseek,
Linus Torvalds1da177e2005-04-16 15:20:36 -070054 .read = do_sync_read,
55 .write = do_sync_write,
56 .aio_read = nfs_file_read,
57 .aio_write = nfs_file_write,
58 .mmap = nfs_file_mmap,
59 .open = nfs_file_open,
60 .flush = nfs_file_flush,
61 .release = nfs_file_release,
62 .fsync = nfs_fsync,
63 .lock = nfs_lock,
64 .flock = nfs_flock,
65 .sendfile = nfs_file_sendfile,
66 .check_flags = nfs_check_flags,
67};
68
69struct inode_operations nfs_file_inode_operations = {
70 .permission = nfs_permission,
71 .getattr = nfs_getattr,
72 .setattr = nfs_setattr,
73};
74
Andreas Gruenbacherb7fa0552005-06-22 17:16:27 +000075#ifdef CONFIG_NFS_V3
76struct inode_operations nfs3_file_inode_operations = {
77 .permission = nfs_permission,
78 .getattr = nfs_getattr,
79 .setattr = nfs_setattr,
80 .listxattr = nfs3_listxattr,
81 .getxattr = nfs3_getxattr,
82 .setxattr = nfs3_setxattr,
83 .removexattr = nfs3_removexattr,
84};
85#endif /* CONFIG_NFS_v3 */
86
Linus Torvalds1da177e2005-04-16 15:20:36 -070087/* Hack for future NFS swap support */
88#ifndef IS_SWAPFILE
89# define IS_SWAPFILE(inode) (0)
90#endif
91
92static int nfs_check_flags(int flags)
93{
94 if ((flags & (O_APPEND | O_DIRECT)) == (O_APPEND | O_DIRECT))
95 return -EINVAL;
96
97 return 0;
98}
99
100/*
101 * Open file
102 */
103static int
104nfs_file_open(struct inode *inode, struct file *filp)
105{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 int res;
107
108 res = nfs_check_flags(filp->f_flags);
109 if (res)
110 return res;
111
Chuck Lever91d5b472006-03-20 13:44:14 -0500112 nfs_inc_stats(inode, NFSIOS_VFSOPEN);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 lock_kernel();
Chuck Lever91d5b472006-03-20 13:44:14 -0500114 res = NFS_SERVER(inode)->rpc_ops->file_open(inode, filp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 unlock_kernel();
116 return res;
117}
118
119static int
120nfs_file_release(struct inode *inode, struct file *filp)
121{
122 /* Ensure that dirty pages are flushed out with the right creds */
123 if (filp->f_mode & FMODE_WRITE)
124 filemap_fdatawrite(filp->f_mapping);
Chuck Lever91d5b472006-03-20 13:44:14 -0500125 nfs_inc_stats(inode, NFSIOS_VFSRELEASE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126 return NFS_PROTO(inode)->file_release(inode, filp);
127}
128
Trond Myklebust980802e2005-06-13 11:14:01 -0400129/**
Trond Myklebustfe51beec2005-06-22 17:16:30 +0000130 * nfs_revalidate_file - Revalidate the page cache & related metadata
131 * @inode - pointer to inode struct
132 * @file - pointer to file
133 */
134static int nfs_revalidate_file(struct inode *inode, struct file *filp)
135{
Chuck Lever55296802005-08-18 11:24:09 -0700136 struct nfs_inode *nfsi = NFS_I(inode);
Trond Myklebustfe51beec2005-06-22 17:16:30 +0000137 int retval = 0;
138
Trond Myklebustb3c52da2005-10-17 06:02:00 -0400139 if ((nfsi->cache_validity & (NFS_INO_REVAL_PAGECACHE|NFS_INO_INVALID_ATTR))
140 || nfs_attribute_timeout(inode))
Trond Myklebustfe51beec2005-06-22 17:16:30 +0000141 retval = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
142 nfs_revalidate_mapping(inode, filp->f_mapping);
143 return 0;
144}
145
146/**
Trond Myklebust980802e2005-06-13 11:14:01 -0400147 * nfs_revalidate_size - Revalidate the file size
148 * @inode - pointer to inode struct
149 * @file - pointer to struct file
150 *
151 * Revalidates the file length. This is basically a wrapper around
152 * nfs_revalidate_inode() that takes into account the fact that we may
153 * have cached writes (in which case we don't care about the server's
154 * idea of what the file length is), or O_DIRECT (in which case we
155 * shouldn't trust the cache).
156 */
157static int nfs_revalidate_file_size(struct inode *inode, struct file *filp)
158{
159 struct nfs_server *server = NFS_SERVER(inode);
160 struct nfs_inode *nfsi = NFS_I(inode);
161
162 if (server->flags & NFS_MOUNT_NOAC)
163 goto force_reval;
164 if (filp->f_flags & O_DIRECT)
165 goto force_reval;
166 if (nfsi->npages != 0)
167 return 0;
Chuck Lever55296802005-08-18 11:24:09 -0700168 if (!(nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE) && !nfs_attribute_timeout(inode))
Trond Myklebustfe51beec2005-06-22 17:16:30 +0000169 return 0;
Trond Myklebust980802e2005-06-13 11:14:01 -0400170force_reval:
171 return __nfs_revalidate_inode(server, inode);
172}
173
174static loff_t nfs_file_llseek(struct file *filp, loff_t offset, int origin)
175{
176 /* origin == SEEK_END => we must revalidate the cached file length */
177 if (origin == 2) {
178 struct inode *inode = filp->f_mapping->host;
179 int retval = nfs_revalidate_file_size(inode, filp);
180 if (retval < 0)
181 return (loff_t)retval;
182 }
183 return remote_llseek(filp, offset, origin);
184}
185
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186/*
187 * Flush all dirty pages, and check for write errors.
188 *
189 */
190static int
191nfs_file_flush(struct file *file)
192{
193 struct nfs_open_context *ctx = (struct nfs_open_context *)file->private_data;
194 struct inode *inode = file->f_dentry->d_inode;
195 int status;
196
197 dfprintk(VFS, "nfs: flush(%s/%ld)\n", inode->i_sb->s_id, inode->i_ino);
198
199 if ((file->f_mode & FMODE_WRITE) == 0)
200 return 0;
Chuck Lever91d5b472006-03-20 13:44:14 -0500201 nfs_inc_stats(inode, NFSIOS_VFSFLUSH);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202 lock_kernel();
203 /* Ensure that data+attribute caches are up to date after close() */
204 status = nfs_wb_all(inode);
205 if (!status) {
206 status = ctx->error;
207 ctx->error = 0;
Trond Myklebust3338c142005-10-27 22:12:41 -0400208 if (!status)
209 nfs_revalidate_inode(NFS_SERVER(inode), inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210 }
211 unlock_kernel();
212 return status;
213}
214
215static ssize_t
216nfs_file_read(struct kiocb *iocb, char __user * buf, size_t count, loff_t pos)
217{
218 struct dentry * dentry = iocb->ki_filp->f_dentry;
219 struct inode * inode = dentry->d_inode;
220 ssize_t result;
221
222#ifdef CONFIG_NFS_DIRECTIO
223 if (iocb->ki_filp->f_flags & O_DIRECT)
224 return nfs_file_direct_read(iocb, buf, count, pos);
225#endif
226
227 dfprintk(VFS, "nfs: read(%s/%s, %lu@%lu)\n",
228 dentry->d_parent->d_name.name, dentry->d_name.name,
229 (unsigned long) count, (unsigned long) pos);
230
Trond Myklebustfe51beec2005-06-22 17:16:30 +0000231 result = nfs_revalidate_file(inode, iocb->ki_filp);
Chuck Lever91d5b472006-03-20 13:44:14 -0500232 nfs_add_stats(inode, NFSIOS_NORMALREADBYTES, count);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233 if (!result)
234 result = generic_file_aio_read(iocb, buf, count, pos);
235 return result;
236}
237
238static ssize_t
239nfs_file_sendfile(struct file *filp, loff_t *ppos, size_t count,
240 read_actor_t actor, void *target)
241{
242 struct dentry *dentry = filp->f_dentry;
243 struct inode *inode = dentry->d_inode;
244 ssize_t res;
245
246 dfprintk(VFS, "nfs: sendfile(%s/%s, %lu@%Lu)\n",
247 dentry->d_parent->d_name.name, dentry->d_name.name,
248 (unsigned long) count, (unsigned long long) *ppos);
249
Trond Myklebustfe51beec2005-06-22 17:16:30 +0000250 res = nfs_revalidate_file(inode, filp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251 if (!res)
252 res = generic_file_sendfile(filp, ppos, count, actor, target);
253 return res;
254}
255
256static int
257nfs_file_mmap(struct file * file, struct vm_area_struct * vma)
258{
259 struct dentry *dentry = file->f_dentry;
260 struct inode *inode = dentry->d_inode;
261 int status;
262
263 dfprintk(VFS, "nfs: mmap(%s/%s)\n",
264 dentry->d_parent->d_name.name, dentry->d_name.name);
265
Trond Myklebustfe51beec2005-06-22 17:16:30 +0000266 status = nfs_revalidate_file(inode, file);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267 if (!status)
268 status = generic_file_mmap(file, vma);
269 return status;
270}
271
272/*
273 * Flush any dirty pages for this process, and check for write errors.
274 * The return status from this call provides a reliable indication of
275 * whether any write errors occurred for this process.
276 */
277static int
278nfs_fsync(struct file *file, struct dentry *dentry, int datasync)
279{
280 struct nfs_open_context *ctx = (struct nfs_open_context *)file->private_data;
281 struct inode *inode = dentry->d_inode;
282 int status;
283
284 dfprintk(VFS, "nfs: fsync(%s/%ld)\n", inode->i_sb->s_id, inode->i_ino);
285
Chuck Lever91d5b472006-03-20 13:44:14 -0500286 nfs_inc_stats(inode, NFSIOS_VFSFSYNC);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700287 lock_kernel();
288 status = nfs_wb_all(inode);
289 if (!status) {
290 status = ctx->error;
291 ctx->error = 0;
292 }
293 unlock_kernel();
294 return status;
295}
296
297/*
298 * This does the "real" work of the write. The generic routine has
299 * allocated the page, locked it, done all the page alignment stuff
300 * calculations etc. Now we should just copy the data from user
301 * space and write it back to the real medium..
302 *
303 * If the writer ends up delaying the write, the writer needs to
304 * increment the page use counts until he is done with the page.
305 */
306static int nfs_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
307{
308 return nfs_flush_incompatible(file, page);
309}
310
311static int nfs_commit_write(struct file *file, struct page *page, unsigned offset, unsigned to)
312{
313 long status;
314
315 lock_kernel();
316 status = nfs_updatepage(file, page, offset, to-offset);
317 unlock_kernel();
318 return status;
319}
320
NeilBrown2ff28e22006-03-26 01:37:18 -0800321static void nfs_invalidate_page(struct page *page, unsigned long offset)
Trond Myklebustcd52ed32006-03-20 13:44:04 -0500322{
323 /* FIXME: we really should cancel any unstarted writes on this page */
Trond Myklebustcd52ed32006-03-20 13:44:04 -0500324}
325
326static int nfs_release_page(struct page *page, gfp_t gfp)
327{
328 return !nfs_wb_page(page->mapping->host, page);
329}
330
Linus Torvalds1da177e2005-04-16 15:20:36 -0700331struct address_space_operations nfs_file_aops = {
332 .readpage = nfs_readpage,
333 .readpages = nfs_readpages,
334 .set_page_dirty = __set_page_dirty_nobuffers,
335 .writepage = nfs_writepage,
336 .writepages = nfs_writepages,
337 .prepare_write = nfs_prepare_write,
338 .commit_write = nfs_commit_write,
Trond Myklebustcd52ed32006-03-20 13:44:04 -0500339 .invalidatepage = nfs_invalidate_page,
340 .releasepage = nfs_release_page,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341#ifdef CONFIG_NFS_DIRECTIO
342 .direct_IO = nfs_direct_IO,
343#endif
344};
345
346/*
347 * Write to a file (through the page cache).
348 */
349static ssize_t
350nfs_file_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t pos)
351{
352 struct dentry * dentry = iocb->ki_filp->f_dentry;
353 struct inode * inode = dentry->d_inode;
354 ssize_t result;
355
356#ifdef CONFIG_NFS_DIRECTIO
357 if (iocb->ki_filp->f_flags & O_DIRECT)
358 return nfs_file_direct_write(iocb, buf, count, pos);
359#endif
360
361 dfprintk(VFS, "nfs: write(%s/%s(%ld), %lu@%lu)\n",
362 dentry->d_parent->d_name.name, dentry->d_name.name,
363 inode->i_ino, (unsigned long) count, (unsigned long) pos);
364
365 result = -EBUSY;
366 if (IS_SWAPFILE(inode))
367 goto out_swapfile;
Trond Myklebust7d52e862005-06-22 17:16:30 +0000368 /*
369 * O_APPEND implies that we must revalidate the file length.
370 */
371 if (iocb->ki_filp->f_flags & O_APPEND) {
372 result = nfs_revalidate_file_size(inode, iocb->ki_filp);
373 if (result)
374 goto out;
Trond Myklebustfe51beec2005-06-22 17:16:30 +0000375 }
376 nfs_revalidate_mapping(inode, iocb->ki_filp->f_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700377
378 result = count;
379 if (!count)
380 goto out;
381
Chuck Lever91d5b472006-03-20 13:44:14 -0500382 nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, count);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383 result = generic_file_aio_write(iocb, buf, count, pos);
384out:
385 return result;
386
387out_swapfile:
388 printk(KERN_INFO "NFS: attempt to write to active swap file!\n");
389 goto out;
390}
391
392static int do_getlk(struct file *filp, int cmd, struct file_lock *fl)
393{
Andy Adamson8dc7c312006-03-20 13:44:26 -0500394 struct file_lock cfl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700395 struct inode *inode = filp->f_mapping->host;
396 int status = 0;
397
398 lock_kernel();
Trond Myklebust039c4d72005-10-18 14:20:16 -0700399 /* Try local locking first */
Andy Adamson8dc7c312006-03-20 13:44:26 -0500400 if (posix_test_lock(filp, fl, &cfl)) {
Trond Myklebuste4cd0382006-03-20 13:44:44 -0500401 fl->fl_start = cfl.fl_start;
402 fl->fl_end = cfl.fl_end;
403 fl->fl_type = cfl.fl_type;
404 fl->fl_pid = cfl.fl_pid;
Trond Myklebust039c4d72005-10-18 14:20:16 -0700405 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700406 }
Trond Myklebust039c4d72005-10-18 14:20:16 -0700407
408 if (nfs_have_delegation(inode, FMODE_READ))
409 goto out_noconflict;
410
411 if (NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM)
412 goto out_noconflict;
413
414 status = NFS_PROTO(inode)->lock(filp, cmd, fl);
415out:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416 unlock_kernel();
417 return status;
Trond Myklebust039c4d72005-10-18 14:20:16 -0700418out_noconflict:
419 fl->fl_type = F_UNLCK;
420 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700421}
422
423static int do_vfs_lock(struct file *file, struct file_lock *fl)
424{
425 int res = 0;
426 switch (fl->fl_flags & (FL_POSIX|FL_FLOCK)) {
427 case FL_POSIX:
428 res = posix_lock_file_wait(file, fl);
429 break;
430 case FL_FLOCK:
431 res = flock_lock_file_wait(file, fl);
432 break;
433 default:
434 BUG();
435 }
436 if (res < 0)
437 printk(KERN_WARNING "%s: VFS is out of sync with lock manager!\n",
438 __FUNCTION__);
439 return res;
440}
441
442static int do_unlk(struct file *filp, int cmd, struct file_lock *fl)
443{
444 struct inode *inode = filp->f_mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 int status;
446
Linus Torvalds1da177e2005-04-16 15:20:36 -0700447 /*
448 * Flush all pending writes before doing anything
449 * with locks..
450 */
Trond Myklebust29884df2005-12-13 16:13:54 -0500451 nfs_sync_mapping(filp->f_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452
453 /* NOTE: special case
454 * If we're signalled while cleaning up locks on process exit, we
455 * still need to complete the unlock.
456 */
457 lock_kernel();
458 /* Use local locking if mounted with "-onolock" */
459 if (!(NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM))
460 status = NFS_PROTO(inode)->lock(filp, cmd, fl);
461 else
462 status = do_vfs_lock(filp, fl);
463 unlock_kernel();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700464 return status;
465}
466
467static int do_setlk(struct file *filp, int cmd, struct file_lock *fl)
468{
469 struct inode *inode = filp->f_mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700470 int status;
471
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472 /*
473 * Flush all pending writes before doing anything
474 * with locks..
475 */
Trond Myklebust29884df2005-12-13 16:13:54 -0500476 status = nfs_sync_mapping(filp->f_mapping);
477 if (status != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700478 goto out;
479
480 lock_kernel();
481 /* Use local locking if mounted with "-onolock" */
482 if (!(NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM)) {
483 status = NFS_PROTO(inode)->lock(filp, cmd, fl);
484 /* If we were signalled we still need to ensure that
485 * we clean up any state on the server. We therefore
486 * record the lock call as having succeeded in order to
487 * ensure that locks_remove_posix() cleans it out when
488 * the process exits.
489 */
490 if (status == -EINTR || status == -ERESTARTSYS)
491 do_vfs_lock(filp, fl);
492 } else
493 status = do_vfs_lock(filp, fl);
494 unlock_kernel();
495 if (status < 0)
496 goto out;
497 /*
498 * Make sure we clear the cache whenever we try to get the lock.
499 * This makes locking act as a cache coherency point.
500 */
Trond Myklebust29884df2005-12-13 16:13:54 -0500501 nfs_sync_mapping(filp->f_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700502 nfs_zap_caches(inode);
503out:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504 return status;
505}
506
507/*
508 * Lock a (portion of) a file
509 */
510static int nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
511{
512 struct inode * inode = filp->f_mapping->host;
513
514 dprintk("NFS: nfs_lock(f=%s/%ld, t=%x, fl=%x, r=%Ld:%Ld)\n",
515 inode->i_sb->s_id, inode->i_ino,
516 fl->fl_type, fl->fl_flags,
517 (long long)fl->fl_start, (long long)fl->fl_end);
Chuck Lever91d5b472006-03-20 13:44:14 -0500518 nfs_inc_stats(inode, NFSIOS_VFSLOCK);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700519
520 /* No mandatory locks over NFS */
ASANO Masahiro0800c5f2005-12-22 13:24:54 +0900521 if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
522 fl->fl_type != F_UNLCK)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700523 return -ENOLCK;
524
525 if (IS_GETLK(cmd))
526 return do_getlk(filp, cmd, fl);
527 if (fl->fl_type == F_UNLCK)
528 return do_unlk(filp, cmd, fl);
529 return do_setlk(filp, cmd, fl);
530}
531
532/*
533 * Lock a (portion of) a file
534 */
535static int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
536{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537 dprintk("NFS: nfs_flock(f=%s/%ld, t=%x, fl=%x)\n",
Trond Myklebuste99170f2006-04-18 13:21:42 -0400538 filp->f_dentry->d_inode->i_sb->s_id,
539 filp->f_dentry->d_inode->i_ino,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700540 fl->fl_type, fl->fl_flags);
541
Linus Torvalds1da177e2005-04-16 15:20:36 -0700542 /*
543 * No BSD flocks over NFS allowed.
544 * Note: we could try to fake a POSIX lock request here by
545 * using ((u32) filp | 0x80000000) or some such as the pid.
546 * Not sure whether that would be unique, though, or whether
547 * that would break in other places.
548 */
549 if (!(fl->fl_flags & FL_FLOCK))
550 return -ENOLCK;
551
552 /* We're simulating flock() locks using posix locks on the server */
553 fl->fl_owner = (fl_owner_t)filp;
554 fl->fl_start = 0;
555 fl->fl_end = OFFSET_MAX;
556
557 if (fl->fl_type == F_UNLCK)
558 return do_unlk(filp, cmd, fl);
559 return do_setlk(filp, cmd, fl);
560}