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Linux/fs/nfsd/vfs.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * File operations used by nfsd. Some of these have been ripped from
  4  * other parts of the kernel because they weren't exported, others
  5  * are partial duplicates with added or changed functionality.
  6  *
  7  * Note that several functions dget() the dentry upon which they want
  8  * to act, most notably those that create directory entries. Response
  9  * dentry's are dput()'d if necessary in the release callback.
 10  * So if you notice code paths that apparently fail to dput() the
 11  * dentry, don't worry--they have been taken care of.
 12  *
 13  * Copyright (C) 1995-1999 Olaf Kirch <okir@monad.swb.de>
 14  * Zerocpy NFS support (C) 2002 Hirokazu Takahashi <taka@valinux.co.jp>
 15  */
 16 
 17 #include <linux/fs.h>
 18 #include <linux/file.h>
 19 #include <linux/splice.h>
 20 #include <linux/falloc.h>
 21 #include <linux/fcntl.h>
 22 #include <linux/namei.h>
 23 #include <linux/delay.h>
 24 #include <linux/fsnotify.h>
 25 #include <linux/posix_acl_xattr.h>
 26 #include <linux/xattr.h>
 27 #include <linux/jhash.h>
 28 #include <linux/ima.h>
 29 #include <linux/slab.h>
 30 #include <linux/uaccess.h>
 31 #include <linux/exportfs.h>
 32 #include <linux/writeback.h>
 33 #include <linux/security.h>
 34 
 35 #ifdef CONFIG_NFSD_V3
 36 #include "xdr3.h"
 37 #endif /* CONFIG_NFSD_V3 */
 38 
 39 #ifdef CONFIG_NFSD_V4
 40 #include "../internal.h"
 41 #include "acl.h"
 42 #include "idmap.h"
 43 #endif /* CONFIG_NFSD_V4 */
 44 
 45 #include "nfsd.h"
 46 #include "vfs.h"
 47 #include "trace.h"
 48 
 49 #define NFSDDBG_FACILITY                NFSDDBG_FILEOP
 50 
 51 
 52 /*
 53  * This is a cache of readahead params that help us choose the proper
 54  * readahead strategy. Initially, we set all readahead parameters to 0
 55  * and let the VFS handle things.
 56  * If you increase the number of cached files very much, you'll need to
 57  * add a hash table here.
 58  */
 59 struct raparms {
 60         struct raparms          *p_next;
 61         unsigned int            p_count;
 62         ino_t                   p_ino;
 63         dev_t                   p_dev;
 64         int                     p_set;
 65         struct file_ra_state    p_ra;
 66         unsigned int            p_hindex;
 67 };
 68 
 69 struct raparm_hbucket {
 70         struct raparms          *pb_head;
 71         spinlock_t              pb_lock;
 72 } ____cacheline_aligned_in_smp;
 73 
 74 #define RAPARM_HASH_BITS        4
 75 #define RAPARM_HASH_SIZE        (1<<RAPARM_HASH_BITS)
 76 #define RAPARM_HASH_MASK        (RAPARM_HASH_SIZE-1)
 77 static struct raparm_hbucket    raparm_hash[RAPARM_HASH_SIZE];
 78 
 79 /* 
 80  * Called from nfsd_lookup and encode_dirent. Check if we have crossed 
 81  * a mount point.
 82  * Returns -EAGAIN or -ETIMEDOUT leaving *dpp and *expp unchanged,
 83  *  or nfs_ok having possibly changed *dpp and *expp
 84  */
 85 int
 86 nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp, 
 87                         struct svc_export **expp)
 88 {
 89         struct svc_export *exp = *expp, *exp2 = NULL;
 90         struct dentry *dentry = *dpp;
 91         struct path path = {.mnt = mntget(exp->ex_path.mnt),
 92                             .dentry = dget(dentry)};
 93         int err = 0;
 94 
 95         err = follow_down(&path);
 96         if (err < 0)
 97                 goto out;
 98         if (path.mnt == exp->ex_path.mnt && path.dentry == dentry &&
 99             nfsd_mountpoint(dentry, exp) == 2) {
100                 /* This is only a mountpoint in some other namespace */
101                 path_put(&path);
102                 goto out;
103         }
104 
105         exp2 = rqst_exp_get_by_name(rqstp, &path);
106         if (IS_ERR(exp2)) {
107                 err = PTR_ERR(exp2);
108                 /*
109                  * We normally allow NFS clients to continue
110                  * "underneath" a mountpoint that is not exported.
111                  * The exception is V4ROOT, where no traversal is ever
112                  * allowed without an explicit export of the new
113                  * directory.
114                  */
115                 if (err == -ENOENT && !(exp->ex_flags & NFSEXP_V4ROOT))
116                         err = 0;
117                 path_put(&path);
118                 goto out;
119         }
120         if (nfsd_v4client(rqstp) ||
121                 (exp->ex_flags & NFSEXP_CROSSMOUNT) || EX_NOHIDE(exp2)) {
122                 /* successfully crossed mount point */
123                 /*
124                  * This is subtle: path.dentry is *not* on path.mnt
125                  * at this point.  The only reason we are safe is that
126                  * original mnt is pinned down by exp, so we should
127                  * put path *before* putting exp
128                  */
129                 *dpp = path.dentry;
130                 path.dentry = dentry;
131                 *expp = exp2;
132                 exp2 = exp;
133         }
134         path_put(&path);
135         exp_put(exp2);
136 out:
137         return err;
138 }
139 
140 static void follow_to_parent(struct path *path)
141 {
142         struct dentry *dp;
143 
144         while (path->dentry == path->mnt->mnt_root && follow_up(path))
145                 ;
146         dp = dget_parent(path->dentry);
147         dput(path->dentry);
148         path->dentry = dp;
149 }
150 
151 static int nfsd_lookup_parent(struct svc_rqst *rqstp, struct dentry *dparent, struct svc_export **exp, struct dentry **dentryp)
152 {
153         struct svc_export *exp2;
154         struct path path = {.mnt = mntget((*exp)->ex_path.mnt),
155                             .dentry = dget(dparent)};
156 
157         follow_to_parent(&path);
158 
159         exp2 = rqst_exp_parent(rqstp, &path);
160         if (PTR_ERR(exp2) == -ENOENT) {
161                 *dentryp = dget(dparent);
162         } else if (IS_ERR(exp2)) {
163                 path_put(&path);
164                 return PTR_ERR(exp2);
165         } else {
166                 *dentryp = dget(path.dentry);
167                 exp_put(*exp);
168                 *exp = exp2;
169         }
170         path_put(&path);
171         return 0;
172 }
173 
174 /*
175  * For nfsd purposes, we treat V4ROOT exports as though there was an
176  * export at *every* directory.
177  * We return:
178  * '1' if this dentry *must* be an export point,
179  * '2' if it might be, if there is really a mount here, and
180  * '' if there is no chance of an export point here.
181  */
182 int nfsd_mountpoint(struct dentry *dentry, struct svc_export *exp)
183 {
184         if (!d_inode(dentry))
185                 return 0;
186         if (exp->ex_flags & NFSEXP_V4ROOT)
187                 return 1;
188         if (nfsd4_is_junction(dentry))
189                 return 1;
190         if (d_mountpoint(dentry))
191                 /*
192                  * Might only be a mountpoint in a different namespace,
193                  * but we need to check.
194                  */
195                 return 2;
196         return 0;
197 }
198 
199 __be32
200 nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp,
201                    const char *name, unsigned int len,
202                    struct svc_export **exp_ret, struct dentry **dentry_ret)
203 {
204         struct svc_export       *exp;
205         struct dentry           *dparent;
206         struct dentry           *dentry;
207         int                     host_err;
208 
209         dprintk("nfsd: nfsd_lookup(fh %s, %.*s)\n", SVCFH_fmt(fhp), len,name);
210 
211         dparent = fhp->fh_dentry;
212         exp = exp_get(fhp->fh_export);
213 
214         /* Lookup the name, but don't follow links */
215         if (isdotent(name, len)) {
216                 if (len==1)
217                         dentry = dget(dparent);
218                 else if (dparent != exp->ex_path.dentry)
219                         dentry = dget_parent(dparent);
220                 else if (!EX_NOHIDE(exp) && !nfsd_v4client(rqstp))
221                         dentry = dget(dparent); /* .. == . just like at / */
222                 else {
223                         /* checking mountpoint crossing is very different when stepping up */
224                         host_err = nfsd_lookup_parent(rqstp, dparent, &exp, &dentry);
225                         if (host_err)
226                                 goto out_nfserr;
227                 }
228         } else {
229                 /*
230                  * In the nfsd4_open() case, this may be held across
231                  * subsequent open and delegation acquisition which may
232                  * need to take the child's i_mutex:
233                  */
234                 fh_lock_nested(fhp, I_MUTEX_PARENT);
235                 dentry = lookup_one_len(name, dparent, len);
236                 host_err = PTR_ERR(dentry);
237                 if (IS_ERR(dentry))
238                         goto out_nfserr;
239                 if (nfsd_mountpoint(dentry, exp)) {
240                         /*
241                          * We don't need the i_mutex after all.  It's
242                          * still possible we could open this (regular
243                          * files can be mountpoints too), but the
244                          * i_mutex is just there to prevent renames of
245                          * something that we might be about to delegate,
246                          * and a mountpoint won't be renamed:
247                          */
248                         fh_unlock(fhp);
249                         if ((host_err = nfsd_cross_mnt(rqstp, &dentry, &exp))) {
250                                 dput(dentry);
251                                 goto out_nfserr;
252                         }
253                 }
254         }
255         *dentry_ret = dentry;
256         *exp_ret = exp;
257         return 0;
258 
259 out_nfserr:
260         exp_put(exp);
261         return nfserrno(host_err);
262 }
263 
264 /*
265  * Look up one component of a pathname.
266  * N.B. After this call _both_ fhp and resfh need an fh_put
267  *
268  * If the lookup would cross a mountpoint, and the mounted filesystem
269  * is exported to the client with NFSEXP_NOHIDE, then the lookup is
270  * accepted as it stands and the mounted directory is
271  * returned. Otherwise the covered directory is returned.
272  * NOTE: this mountpoint crossing is not supported properly by all
273  *   clients and is explicitly disallowed for NFSv3
274  *      NeilBrown <neilb@cse.unsw.edu.au>
275  */
276 __be32
277 nfsd_lookup(struct svc_rqst *rqstp, struct svc_fh *fhp, const char *name,
278                                 unsigned int len, struct svc_fh *resfh)
279 {
280         struct svc_export       *exp;
281         struct dentry           *dentry;
282         __be32 err;
283 
284         err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_EXEC);
285         if (err)
286                 return err;
287         err = nfsd_lookup_dentry(rqstp, fhp, name, len, &exp, &dentry);
288         if (err)
289                 return err;
290         err = check_nfsd_access(exp, rqstp);
291         if (err)
292                 goto out;
293         /*
294          * Note: we compose the file handle now, but as the
295          * dentry may be negative, it may need to be updated.
296          */
297         err = fh_compose(resfh, exp, dentry, fhp);
298         if (!err && d_really_is_negative(dentry))
299                 err = nfserr_noent;
300 out:
301         dput(dentry);
302         exp_put(exp);
303         return err;
304 }
305 
306 /*
307  * Commit metadata changes to stable storage.
308  */
309 static int
310 commit_metadata(struct svc_fh *fhp)
311 {
312         struct inode *inode = d_inode(fhp->fh_dentry);
313         const struct export_operations *export_ops = inode->i_sb->s_export_op;
314 
315         if (!EX_ISSYNC(fhp->fh_export))
316                 return 0;
317 
318         if (export_ops->commit_metadata)
319                 return export_ops->commit_metadata(inode);
320         return sync_inode_metadata(inode, 1);
321 }
322 
323 /*
324  * Go over the attributes and take care of the small differences between
325  * NFS semantics and what Linux expects.
326  */
327 static void
328 nfsd_sanitize_attrs(struct inode *inode, struct iattr *iap)
329 {
330         /* sanitize the mode change */
331         if (iap->ia_valid & ATTR_MODE) {
332                 iap->ia_mode &= S_IALLUGO;
333                 iap->ia_mode |= (inode->i_mode & ~S_IALLUGO);
334         }
335 
336         /* Revoke setuid/setgid on chown */
337         if (!S_ISDIR(inode->i_mode) &&
338             ((iap->ia_valid & ATTR_UID) || (iap->ia_valid & ATTR_GID))) {
339                 iap->ia_valid |= ATTR_KILL_PRIV;
340                 if (iap->ia_valid & ATTR_MODE) {
341                         /* we're setting mode too, just clear the s*id bits */
342                         iap->ia_mode &= ~S_ISUID;
343                         if (iap->ia_mode & S_IXGRP)
344                                 iap->ia_mode &= ~S_ISGID;
345                 } else {
346                         /* set ATTR_KILL_* bits and let VFS handle it */
347                         iap->ia_valid |= (ATTR_KILL_SUID | ATTR_KILL_SGID);
348                 }
349         }
350 }
351 
352 static __be32
353 nfsd_get_write_access(struct svc_rqst *rqstp, struct svc_fh *fhp,
354                 struct iattr *iap)
355 {
356         struct inode *inode = d_inode(fhp->fh_dentry);
357         int host_err;
358 
359         if (iap->ia_size < inode->i_size) {
360                 __be32 err;
361 
362                 err = nfsd_permission(rqstp, fhp->fh_export, fhp->fh_dentry,
363                                 NFSD_MAY_TRUNC | NFSD_MAY_OWNER_OVERRIDE);
364                 if (err)
365                         return err;
366         }
367 
368         host_err = get_write_access(inode);
369         if (host_err)
370                 goto out_nfserrno;
371 
372         host_err = locks_verify_truncate(inode, NULL, iap->ia_size);
373         if (host_err)
374                 goto out_put_write_access;
375         return 0;
376 
377 out_put_write_access:
378         put_write_access(inode);
379 out_nfserrno:
380         return nfserrno(host_err);
381 }
382 
383 /*
384  * Set various file attributes.  After this call fhp needs an fh_put.
385  */
386 __be32
387 nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
388              int check_guard, time_t guardtime)
389 {
390         struct dentry   *dentry;
391         struct inode    *inode;
392         int             accmode = NFSD_MAY_SATTR;
393         umode_t         ftype = 0;
394         __be32          err;
395         int             host_err;
396         bool            get_write_count;
397         bool            size_change = (iap->ia_valid & ATTR_SIZE);
398 
399         if (iap->ia_valid & (ATTR_ATIME | ATTR_MTIME | ATTR_SIZE))
400                 accmode |= NFSD_MAY_WRITE|NFSD_MAY_OWNER_OVERRIDE;
401         if (iap->ia_valid & ATTR_SIZE)
402                 ftype = S_IFREG;
403 
404         /* Callers that do fh_verify should do the fh_want_write: */
405         get_write_count = !fhp->fh_dentry;
406 
407         /* Get inode */
408         err = fh_verify(rqstp, fhp, ftype, accmode);
409         if (err)
410                 return err;
411         if (get_write_count) {
412                 host_err = fh_want_write(fhp);
413                 if (host_err)
414                         goto out;
415         }
416 
417         dentry = fhp->fh_dentry;
418         inode = d_inode(dentry);
419 
420         /* Ignore any mode updates on symlinks */
421         if (S_ISLNK(inode->i_mode))
422                 iap->ia_valid &= ~ATTR_MODE;
423 
424         if (!iap->ia_valid)
425                 return 0;
426 
427         nfsd_sanitize_attrs(inode, iap);
428 
429         if (check_guard && guardtime != inode->i_ctime.tv_sec)
430                 return nfserr_notsync;
431 
432         /*
433          * The size case is special, it changes the file in addition to the
434          * attributes, and file systems don't expect it to be mixed with
435          * "random" attribute changes.  We thus split out the size change
436          * into a separate call to ->setattr, and do the rest as a separate
437          * setattr call.
438          */
439         if (size_change) {
440                 err = nfsd_get_write_access(rqstp, fhp, iap);
441                 if (err)
442                         return err;
443         }
444 
445         fh_lock(fhp);
446         if (size_change) {
447                 /*
448                  * RFC5661, Section 18.30.4:
449                  *   Changing the size of a file with SETATTR indirectly
450                  *   changes the time_modify and change attributes.
451                  *
452                  * (and similar for the older RFCs)
453                  */
454                 struct iattr size_attr = {
455                         .ia_valid       = ATTR_SIZE | ATTR_CTIME | ATTR_MTIME,
456                         .ia_size        = iap->ia_size,
457                 };
458 
459                 host_err = notify_change(dentry, &size_attr, NULL);
460                 if (host_err)
461                         goto out_unlock;
462                 iap->ia_valid &= ~ATTR_SIZE;
463 
464                 /*
465                  * Avoid the additional setattr call below if the only other
466                  * attribute that the client sends is the mtime, as we update
467                  * it as part of the size change above.
468                  */
469                 if ((iap->ia_valid & ~ATTR_MTIME) == 0)
470                         goto out_unlock;
471         }
472 
473         iap->ia_valid |= ATTR_CTIME;
474         host_err = notify_change(dentry, iap, NULL);
475 
476 out_unlock:
477         fh_unlock(fhp);
478         if (size_change)
479                 put_write_access(inode);
480 out:
481         if (!host_err)
482                 host_err = commit_metadata(fhp);
483         return nfserrno(host_err);
484 }
485 
486 #if defined(CONFIG_NFSD_V4)
487 /*
488  * NFS junction information is stored in an extended attribute.
489  */
490 #define NFSD_JUNCTION_XATTR_NAME        XATTR_TRUSTED_PREFIX "junction.nfs"
491 
492 /**
493  * nfsd4_is_junction - Test if an object could be an NFS junction
494  *
495  * @dentry: object to test
496  *
497  * Returns 1 if "dentry" appears to contain NFS junction information.
498  * Otherwise 0 is returned.
499  */
500 int nfsd4_is_junction(struct dentry *dentry)
501 {
502         struct inode *inode = d_inode(dentry);
503 
504         if (inode == NULL)
505                 return 0;
506         if (inode->i_mode & S_IXUGO)
507                 return 0;
508         if (!(inode->i_mode & S_ISVTX))
509                 return 0;
510         if (vfs_getxattr(dentry, NFSD_JUNCTION_XATTR_NAME, NULL, 0) <= 0)
511                 return 0;
512         return 1;
513 }
514 #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
515 __be32 nfsd4_set_nfs4_label(struct svc_rqst *rqstp, struct svc_fh *fhp,
516                 struct xdr_netobj *label)
517 {
518         __be32 error;
519         int host_error;
520         struct dentry *dentry;
521 
522         error = fh_verify(rqstp, fhp, 0 /* S_IFREG */, NFSD_MAY_SATTR);
523         if (error)
524                 return error;
525 
526         dentry = fhp->fh_dentry;
527 
528         inode_lock(d_inode(dentry));
529         host_error = security_inode_setsecctx(dentry, label->data, label->len);
530         inode_unlock(d_inode(dentry));
531         return nfserrno(host_error);
532 }
533 #else
534 __be32 nfsd4_set_nfs4_label(struct svc_rqst *rqstp, struct svc_fh *fhp,
535                 struct xdr_netobj *label)
536 {
537         return nfserr_notsupp;
538 }
539 #endif
540 
541 __be32 nfsd4_clone_file_range(struct file *src, u64 src_pos, struct file *dst,
542                 u64 dst_pos, u64 count)
543 {
544         return nfserrno(do_clone_file_range(src, src_pos, dst, dst_pos, count));
545 }
546 
547 ssize_t nfsd_copy_file_range(struct file *src, u64 src_pos, struct file *dst,
548                              u64 dst_pos, u64 count)
549 {
550 
551         /*
552          * Limit copy to 4MB to prevent indefinitely blocking an nfsd
553          * thread and client rpc slot.  The choice of 4MB is somewhat
554          * arbitrary.  We might instead base this on r/wsize, or make it
555          * tunable, or use a time instead of a byte limit, or implement
556          * asynchronous copy.  In theory a client could also recognize a
557          * limit like this and pipeline multiple COPY requests.
558          */
559         count = min_t(u64, count, 1 << 22);
560         return vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0);
561 }
562 
563 __be32 nfsd4_vfs_fallocate(struct svc_rqst *rqstp, struct svc_fh *fhp,
564                            struct file *file, loff_t offset, loff_t len,
565                            int flags)
566 {
567         int error;
568 
569         if (!S_ISREG(file_inode(file)->i_mode))
570                 return nfserr_inval;
571 
572         error = vfs_fallocate(file, flags, offset, len);
573         if (!error)
574                 error = commit_metadata(fhp);
575 
576         return nfserrno(error);
577 }
578 #endif /* defined(CONFIG_NFSD_V4) */
579 
580 #ifdef CONFIG_NFSD_V3
581 /*
582  * Check server access rights to a file system object
583  */
584 struct accessmap {
585         u32             access;
586         int             how;
587 };
588 static struct accessmap nfs3_regaccess[] = {
589     {   NFS3_ACCESS_READ,       NFSD_MAY_READ                   },
590     {   NFS3_ACCESS_EXECUTE,    NFSD_MAY_EXEC                   },
591     {   NFS3_ACCESS_MODIFY,     NFSD_MAY_WRITE|NFSD_MAY_TRUNC   },
592     {   NFS3_ACCESS_EXTEND,     NFSD_MAY_WRITE                  },
593 
594     {   0,                      0                               }
595 };
596 
597 static struct accessmap nfs3_diraccess[] = {
598     {   NFS3_ACCESS_READ,       NFSD_MAY_READ                   },
599     {   NFS3_ACCESS_LOOKUP,     NFSD_MAY_EXEC                   },
600     {   NFS3_ACCESS_MODIFY,     NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC},
601     {   NFS3_ACCESS_EXTEND,     NFSD_MAY_EXEC|NFSD_MAY_WRITE    },
602     {   NFS3_ACCESS_DELETE,     NFSD_MAY_REMOVE                 },
603 
604     {   0,                      0                               }
605 };
606 
607 static struct accessmap nfs3_anyaccess[] = {
608         /* Some clients - Solaris 2.6 at least, make an access call
609          * to the server to check for access for things like /dev/null
610          * (which really, the server doesn't care about).  So
611          * We provide simple access checking for them, looking
612          * mainly at mode bits, and we make sure to ignore read-only
613          * filesystem checks
614          */
615     {   NFS3_ACCESS_READ,       NFSD_MAY_READ                   },
616     {   NFS3_ACCESS_EXECUTE,    NFSD_MAY_EXEC                   },
617     {   NFS3_ACCESS_MODIFY,     NFSD_MAY_WRITE|NFSD_MAY_LOCAL_ACCESS    },
618     {   NFS3_ACCESS_EXTEND,     NFSD_MAY_WRITE|NFSD_MAY_LOCAL_ACCESS    },
619 
620     {   0,                      0                               }
621 };
622 
623 __be32
624 nfsd_access(struct svc_rqst *rqstp, struct svc_fh *fhp, u32 *access, u32 *supported)
625 {
626         struct accessmap        *map;
627         struct svc_export       *export;
628         struct dentry           *dentry;
629         u32                     query, result = 0, sresult = 0;
630         __be32                  error;
631 
632         error = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP);
633         if (error)
634                 goto out;
635 
636         export = fhp->fh_export;
637         dentry = fhp->fh_dentry;
638 
639         if (d_is_reg(dentry))
640                 map = nfs3_regaccess;
641         else if (d_is_dir(dentry))
642                 map = nfs3_diraccess;
643         else
644                 map = nfs3_anyaccess;
645 
646 
647         query = *access;
648         for  (; map->access; map++) {
649                 if (map->access & query) {
650                         __be32 err2;
651 
652                         sresult |= map->access;
653 
654                         err2 = nfsd_permission(rqstp, export, dentry, map->how);
655                         switch (err2) {
656                         case nfs_ok:
657                                 result |= map->access;
658                                 break;
659                                 
660                         /* the following error codes just mean the access was not allowed,
661                          * rather than an error occurred */
662                         case nfserr_rofs:
663                         case nfserr_acces:
664                         case nfserr_perm:
665                                 /* simply don't "or" in the access bit. */
666                                 break;
667                         default:
668                                 error = err2;
669                                 goto out;
670                         }
671                 }
672         }
673         *access = result;
674         if (supported)
675                 *supported = sresult;
676 
677  out:
678         return error;
679 }
680 #endif /* CONFIG_NFSD_V3 */
681 
682 static int nfsd_open_break_lease(struct inode *inode, int access)
683 {
684         unsigned int mode;
685 
686         if (access & NFSD_MAY_NOT_BREAK_LEASE)
687                 return 0;
688         mode = (access & NFSD_MAY_WRITE) ? O_WRONLY : O_RDONLY;
689         return break_lease(inode, mode | O_NONBLOCK);
690 }
691 
692 /*
693  * Open an existing file or directory.
694  * The may_flags argument indicates the type of open (read/write/lock)
695  * and additional flags.
696  * N.B. After this call fhp needs an fh_put
697  */
698 __be32
699 nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
700                         int may_flags, struct file **filp)
701 {
702         struct path     path;
703         struct inode    *inode;
704         struct file     *file;
705         int             flags = O_RDONLY|O_LARGEFILE;
706         __be32          err;
707         int             host_err = 0;
708 
709         validate_process_creds();
710 
711         /*
712          * If we get here, then the client has already done an "open",
713          * and (hopefully) checked permission - so allow OWNER_OVERRIDE
714          * in case a chmod has now revoked permission.
715          *
716          * Arguably we should also allow the owner override for
717          * directories, but we never have and it doesn't seem to have
718          * caused anyone a problem.  If we were to change this, note
719          * also that our filldir callbacks would need a variant of
720          * lookup_one_len that doesn't check permissions.
721          */
722         if (type == S_IFREG)
723                 may_flags |= NFSD_MAY_OWNER_OVERRIDE;
724         err = fh_verify(rqstp, fhp, type, may_flags);
725         if (err)
726                 goto out;
727 
728         path.mnt = fhp->fh_export->ex_path.mnt;
729         path.dentry = fhp->fh_dentry;
730         inode = d_inode(path.dentry);
731 
732         /* Disallow write access to files with the append-only bit set
733          * or any access when mandatory locking enabled
734          */
735         err = nfserr_perm;
736         if (IS_APPEND(inode) && (may_flags & NFSD_MAY_WRITE))
737                 goto out;
738         /*
739          * We must ignore files (but only files) which might have mandatory
740          * locks on them because there is no way to know if the accesser has
741          * the lock.
742          */
743         if (S_ISREG((inode)->i_mode) && mandatory_lock(inode))
744                 goto out;
745 
746         if (!inode->i_fop)
747                 goto out;
748 
749         host_err = nfsd_open_break_lease(inode, may_flags);
750         if (host_err) /* NOMEM or WOULDBLOCK */
751                 goto out_nfserr;
752 
753         if (may_flags & NFSD_MAY_WRITE) {
754                 if (may_flags & NFSD_MAY_READ)
755                         flags = O_RDWR|O_LARGEFILE;
756                 else
757                         flags = O_WRONLY|O_LARGEFILE;
758         }
759 
760         file = dentry_open(&path, flags, current_cred());
761         if (IS_ERR(file)) {
762                 host_err = PTR_ERR(file);
763                 goto out_nfserr;
764         }
765 
766         host_err = ima_file_check(file, may_flags, 0);
767         if (host_err) {
768                 fput(file);
769                 goto out_nfserr;
770         }
771 
772         if (may_flags & NFSD_MAY_64BIT_COOKIE)
773                 file->f_mode |= FMODE_64BITHASH;
774         else
775                 file->f_mode |= FMODE_32BITHASH;
776 
777         *filp = file;
778 out_nfserr:
779         err = nfserrno(host_err);
780 out:
781         validate_process_creds();
782         return err;
783 }
784 
785 struct raparms *
786 nfsd_init_raparms(struct file *file)
787 {
788         struct inode *inode = file_inode(file);
789         dev_t dev = inode->i_sb->s_dev;
790         ino_t ino = inode->i_ino;
791         struct raparms  *ra, **rap, **frap = NULL;
792         int depth = 0;
793         unsigned int hash;
794         struct raparm_hbucket *rab;
795 
796         hash = jhash_2words(dev, ino, 0xfeedbeef) & RAPARM_HASH_MASK;
797         rab = &raparm_hash[hash];
798 
799         spin_lock(&rab->pb_lock);
800         for (rap = &rab->pb_head; (ra = *rap); rap = &ra->p_next) {
801                 if (ra->p_ino == ino && ra->p_dev == dev)
802                         goto found;
803                 depth++;
804                 if (ra->p_count == 0)
805                         frap = rap;
806         }
807         depth = nfsdstats.ra_size;
808         if (!frap) {    
809                 spin_unlock(&rab->pb_lock);
810                 return NULL;
811         }
812         rap = frap;
813         ra = *frap;
814         ra->p_dev = dev;
815         ra->p_ino = ino;
816         ra->p_set = 0;
817         ra->p_hindex = hash;
818 found:
819         if (rap != &rab->pb_head) {
820                 *rap = ra->p_next;
821                 ra->p_next   = rab->pb_head;
822                 rab->pb_head = ra;
823         }
824         ra->p_count++;
825         nfsdstats.ra_depth[depth*10/nfsdstats.ra_size]++;
826         spin_unlock(&rab->pb_lock);
827 
828         if (ra->p_set)
829                 file->f_ra = ra->p_ra;
830         return ra;
831 }
832 
833 void nfsd_put_raparams(struct file *file, struct raparms *ra)
834 {
835         struct raparm_hbucket *rab = &raparm_hash[ra->p_hindex];
836 
837         spin_lock(&rab->pb_lock);
838         ra->p_ra = file->f_ra;
839         ra->p_set = 1;
840         ra->p_count--;
841         spin_unlock(&rab->pb_lock);
842 }
843 
844 /*
845  * Grab and keep cached pages associated with a file in the svc_rqst
846  * so that they can be passed to the network sendmsg/sendpage routines
847  * directly. They will be released after the sending has completed.
848  */
849 static int
850 nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
851                   struct splice_desc *sd)
852 {
853         struct svc_rqst *rqstp = sd->u.data;
854         struct page **pp = rqstp->rq_next_page;
855         struct page *page = buf->page;
856         size_t size;
857 
858         size = sd->len;
859 
860         if (rqstp->rq_res.page_len == 0) {
861                 get_page(page);
862                 put_page(*rqstp->rq_next_page);
863                 *(rqstp->rq_next_page++) = page;
864                 rqstp->rq_res.page_base = buf->offset;
865                 rqstp->rq_res.page_len = size;
866         } else if (page != pp[-1]) {
867                 get_page(page);
868                 if (*rqstp->rq_next_page)
869                         put_page(*rqstp->rq_next_page);
870                 *(rqstp->rq_next_page++) = page;
871                 rqstp->rq_res.page_len += size;
872         } else
873                 rqstp->rq_res.page_len += size;
874 
875         return size;
876 }
877 
878 static int nfsd_direct_splice_actor(struct pipe_inode_info *pipe,
879                                     struct splice_desc *sd)
880 {
881         return __splice_from_pipe(pipe, sd, nfsd_splice_actor);
882 }
883 
884 static __be32 nfsd_finish_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
885                                struct file *file, loff_t offset,
886                                unsigned long *count, int host_err)
887 {
888         if (host_err >= 0) {
889                 nfsdstats.io_read += host_err;
890                 *count = host_err;
891                 fsnotify_access(file);
892                 trace_nfsd_read_io_done(rqstp, fhp, offset, *count);
893                 return 0;
894         } else {
895                 trace_nfsd_read_err(rqstp, fhp, offset, host_err);
896                 return nfserrno(host_err);
897         }
898 }
899 
900 __be32 nfsd_splice_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
901                         struct file *file, loff_t offset, unsigned long *count)
902 {
903         struct splice_desc sd = {
904                 .len            = 0,
905                 .total_len      = *count,
906                 .pos            = offset,
907                 .u.data         = rqstp,
908         };
909         int host_err;
910 
911         trace_nfsd_read_splice(rqstp, fhp, offset, *count);
912         rqstp->rq_next_page = rqstp->rq_respages + 1;
913         host_err = splice_direct_to_actor(file, &sd, nfsd_direct_splice_actor);
914         return nfsd_finish_read(rqstp, fhp, file, offset, count, host_err);
915 }
916 
917 __be32 nfsd_readv(struct svc_rqst *rqstp, struct svc_fh *fhp,
918                   struct file *file, loff_t offset,
919                   struct kvec *vec, int vlen, unsigned long *count)
920 {
921         struct iov_iter iter;
922         int host_err;
923 
924         trace_nfsd_read_vector(rqstp, fhp, offset, *count);
925         iov_iter_kvec(&iter, READ | ITER_KVEC, vec, vlen, *count);
926         host_err = vfs_iter_read(file, &iter, &offset, 0);
927         return nfsd_finish_read(rqstp, fhp, file, offset, count, host_err);
928 }
929 
930 /*
931  * Gathered writes: If another process is currently writing to the file,
932  * there's a high chance this is another nfsd (triggered by a bulk write
933  * from a client's biod). Rather than syncing the file with each write
934  * request, we sleep for 10 msec.
935  *
936  * I don't know if this roughly approximates C. Juszak's idea of
937  * gathered writes, but it's a nice and simple solution (IMHO), and it
938  * seems to work:-)
939  *
940  * Note: we do this only in the NFSv2 case, since v3 and higher have a
941  * better tool (separate unstable writes and commits) for solving this
942  * problem.
943  */
944 static int wait_for_concurrent_writes(struct file *file)
945 {
946         struct inode *inode = file_inode(file);
947         static ino_t last_ino;
948         static dev_t last_dev;
949         int err = 0;
950 
951         if (atomic_read(&inode->i_writecount) > 1
952             || (last_ino == inode->i_ino && last_dev == inode->i_sb->s_dev)) {
953                 dprintk("nfsd: write defer %d\n", task_pid_nr(current));
954                 msleep(10);
955                 dprintk("nfsd: write resume %d\n", task_pid_nr(current));
956         }
957 
958         if (inode->i_state & I_DIRTY) {
959                 dprintk("nfsd: write sync %d\n", task_pid_nr(current));
960                 err = vfs_fsync(file, 0);
961         }
962         last_ino = inode->i_ino;
963         last_dev = inode->i_sb->s_dev;
964         return err;
965 }
966 
967 __be32
968 nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
969                                 loff_t offset, struct kvec *vec, int vlen,
970                                 unsigned long *cnt, int stable)
971 {
972         struct svc_export       *exp;
973         struct iov_iter         iter;
974         __be32                  nfserr;
975         int                     host_err;
976         int                     use_wgather;
977         loff_t                  pos = offset;
978         unsigned int            pflags = current->flags;
979         rwf_t                   flags = 0;
980 
981         trace_nfsd_write_opened(rqstp, fhp, offset, *cnt);
982 
983         if (test_bit(RQ_LOCAL, &rqstp->rq_flags))
984                 /*
985                  * We want less throttling in balance_dirty_pages()
986                  * and shrink_inactive_list() so that nfs to
987                  * localhost doesn't cause nfsd to lock up due to all
988                  * the client's dirty pages or its congested queue.
989                  */
990                 current->flags |= PF_LESS_THROTTLE;
991 
992         exp = fhp->fh_export;
993         use_wgather = (rqstp->rq_vers == 2) && EX_WGATHER(exp);
994 
995         if (!EX_ISSYNC(exp))
996                 stable = NFS_UNSTABLE;
997 
998         if (stable && !use_wgather)
999                 flags |= RWF_SYNC;
1000 
1001         iov_iter_kvec(&iter, WRITE | ITER_KVEC, vec, vlen, *cnt);
1002         host_err = vfs_iter_write(file, &iter, &pos, flags);
1003         if (host_err < 0)
1004                 goto out_nfserr;
1005         nfsdstats.io_write += *cnt;
1006         fsnotify_modify(file);
1007 
1008         if (stable && use_wgather)
1009                 host_err = wait_for_concurrent_writes(file);
1010 
1011 out_nfserr:
1012         if (host_err >= 0) {
1013                 trace_nfsd_write_io_done(rqstp, fhp, offset, *cnt);
1014                 nfserr = nfs_ok;
1015         } else {
1016                 trace_nfsd_write_err(rqstp, fhp, offset, host_err);
1017                 nfserr = nfserrno(host_err);
1018         }
1019         if (test_bit(RQ_LOCAL, &rqstp->rq_flags))
1020                 current_restore_flags(pflags, PF_LESS_THROTTLE);
1021         return nfserr;
1022 }
1023 
1024 /*
1025  * Read data from a file. count must contain the requested read count
1026  * on entry. On return, *count contains the number of bytes actually read.
1027  * N.B. After this call fhp needs an fh_put
1028  */
1029 __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
1030         loff_t offset, struct kvec *vec, int vlen, unsigned long *count)
1031 {
1032         struct file *file;
1033         struct raparms  *ra;
1034         __be32 err;
1035 
1036         trace_nfsd_read_start(rqstp, fhp, offset, *count);
1037         err = nfsd_open(rqstp, fhp, S_IFREG, NFSD_MAY_READ, &file);
1038         if (err)
1039                 return err;
1040 
1041         ra = nfsd_init_raparms(file);
1042 
1043         if (file->f_op->splice_read && test_bit(RQ_SPLICE_OK, &rqstp->rq_flags))
1044                 err = nfsd_splice_read(rqstp, fhp, file, offset, count);
1045         else
1046                 err = nfsd_readv(rqstp, fhp, file, offset, vec, vlen, count);
1047 
1048         if (ra)
1049                 nfsd_put_raparams(file, ra);
1050         fput(file);
1051 
1052         trace_nfsd_read_done(rqstp, fhp, offset, *count);
1053 
1054         return err;
1055 }
1056 
1057 /*
1058  * Write data to a file.
1059  * The stable flag requests synchronous writes.
1060  * N.B. After this call fhp needs an fh_put
1061  */
1062 __be32
1063 nfsd_write(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t offset,
1064            struct kvec *vec, int vlen, unsigned long *cnt, int stable)
1065 {
1066         struct file *file = NULL;
1067         __be32 err = 0;
1068 
1069         trace_nfsd_write_start(rqstp, fhp, offset, *cnt);
1070 
1071         err = nfsd_open(rqstp, fhp, S_IFREG, NFSD_MAY_WRITE, &file);
1072         if (err)
1073                 goto out;
1074 
1075         err = nfsd_vfs_write(rqstp, fhp, file, offset, vec, vlen, cnt, stable);
1076         fput(file);
1077 out:
1078         trace_nfsd_write_done(rqstp, fhp, offset, *cnt);
1079         return err;
1080 }
1081 
1082 #ifdef CONFIG_NFSD_V3
1083 /*
1084  * Commit all pending writes to stable storage.
1085  *
1086  * Note: we only guarantee that data that lies within the range specified
1087  * by the 'offset' and 'count' parameters will be synced.
1088  *
1089  * Unfortunately we cannot lock the file to make sure we return full WCC
1090  * data to the client, as locking happens lower down in the filesystem.
1091  */
1092 __be32
1093 nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp,
1094                loff_t offset, unsigned long count)
1095 {
1096         struct file     *file;
1097         loff_t          end = LLONG_MAX;
1098         __be32          err = nfserr_inval;
1099 
1100         if (offset < 0)
1101                 goto out;
1102         if (count != 0) {
1103                 end = offset + (loff_t)count - 1;
1104                 if (end < offset)
1105                         goto out;
1106         }
1107 
1108         err = nfsd_open(rqstp, fhp, S_IFREG,
1109                         NFSD_MAY_WRITE|NFSD_MAY_NOT_BREAK_LEASE, &file);
1110         if (err)
1111                 goto out;
1112         if (EX_ISSYNC(fhp->fh_export)) {
1113                 int err2 = vfs_fsync_range(file, offset, end, 0);
1114 
1115                 if (err2 != -EINVAL)
1116                         err = nfserrno(err2);
1117                 else
1118                         err = nfserr_notsupp;
1119         }
1120 
1121         fput(file);
1122 out:
1123         return err;
1124 }
1125 #endif /* CONFIG_NFSD_V3 */
1126 
1127 static __be32
1128 nfsd_create_setattr(struct svc_rqst *rqstp, struct svc_fh *resfhp,
1129                         struct iattr *iap)
1130 {
1131         /*
1132          * Mode has already been set earlier in create:
1133          */
1134         iap->ia_valid &= ~ATTR_MODE;
1135         /*
1136          * Setting uid/gid works only for root.  Irix appears to
1137          * send along the gid on create when it tries to implement
1138          * setgid directories via NFS:
1139          */
1140         if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID))
1141                 iap->ia_valid &= ~(ATTR_UID|ATTR_GID);
1142         if (iap->ia_valid)
1143                 return nfsd_setattr(rqstp, resfhp, iap, 0, (time_t)0);
1144         /* Callers expect file metadata to be committed here */
1145         return nfserrno(commit_metadata(resfhp));
1146 }
1147 
1148 /* HPUX client sometimes creates a file in mode 000, and sets size to 0.
1149  * setting size to 0 may fail for some specific file systems by the permission
1150  * checking which requires WRITE permission but the mode is 000.
1151  * we ignore the resizing(to 0) on the just new created file, since the size is
1152  * 0 after file created.
1153  *
1154  * call this only after vfs_create() is called.
1155  * */
1156 static void
1157 nfsd_check_ignore_resizing(struct iattr *iap)
1158 {
1159         if ((iap->ia_valid & ATTR_SIZE) && (iap->ia_size == 0))
1160                 iap->ia_valid &= ~ATTR_SIZE;
1161 }
1162 
1163 /* The parent directory should already be locked: */
1164 __be32
1165 nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
1166                 char *fname, int flen, struct iattr *iap,
1167                 int type, dev_t rdev, struct svc_fh *resfhp)
1168 {
1169         struct dentry   *dentry, *dchild;
1170         struct inode    *dirp;
1171         __be32          err;
1172         __be32          err2;
1173         int             host_err;
1174 
1175         dentry = fhp->fh_dentry;
1176         dirp = d_inode(dentry);
1177 
1178         dchild = dget(resfhp->fh_dentry);
1179         if (!fhp->fh_locked) {
1180                 WARN_ONCE(1, "nfsd_create: parent %pd2 not locked!\n",
1181                                 dentry);
1182                 err = nfserr_io;
1183                 goto out;
1184         }
1185 
1186         err = nfsd_permission(rqstp, fhp->fh_export, dentry, NFSD_MAY_CREATE);
1187         if (err)
1188                 goto out;
1189 
1190         if (!(iap->ia_valid & ATTR_MODE))
1191                 iap->ia_mode = 0;
1192         iap->ia_mode = (iap->ia_mode & S_IALLUGO) | type;
1193 
1194         err = 0;
1195         host_err = 0;
1196         switch (type) {
1197         case S_IFREG:
1198                 host_err = vfs_create(dirp, dchild, iap->ia_mode, true);
1199                 if (!host_err)
1200                         nfsd_check_ignore_resizing(iap);
1201                 break;
1202         case S_IFDIR:
1203                 host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
1204                 if (!host_err && unlikely(d_unhashed(dchild))) {
1205                         struct dentry *d;
1206                         d = lookup_one_len(dchild->d_name.name,
1207                                            dchild->d_parent,
1208                                            dchild->d_name.len);
1209                         if (IS_ERR(d)) {
1210                                 host_err = PTR_ERR(d);
1211                                 break;
1212                         }
1213                         if (unlikely(d_is_negative(d))) {
1214                                 dput(d);
1215                                 err = nfserr_serverfault;
1216                                 goto out;
1217                         }
1218                         dput(resfhp->fh_dentry);
1219                         resfhp->fh_dentry = dget(d);
1220                         err = fh_update(resfhp);
1221                         dput(dchild);
1222                         dchild = d;
1223                         if (err)
1224                                 goto out;
1225                 }
1226                 break;
1227         case S_IFCHR:
1228         case S_IFBLK:
1229         case S_IFIFO:
1230         case S_IFSOCK:
1231                 host_err = vfs_mknod(dirp, dchild, iap->ia_mode, rdev);
1232                 break;
1233         default:
1234                 printk(KERN_WARNING "nfsd: bad file type %o in nfsd_create\n",
1235                        type);
1236                 host_err = -EINVAL;
1237         }
1238         if (host_err < 0)
1239                 goto out_nfserr;
1240 
1241         err = nfsd_create_setattr(rqstp, resfhp, iap);
1242 
1243         /*
1244          * nfsd_create_setattr already committed the child.  Transactional
1245          * filesystems had a chance to commit changes for both parent and
1246          * child simultaneously making the following commit_metadata a
1247          * noop.
1248          */
1249         err2 = nfserrno(commit_metadata(fhp));
1250         if (err2)
1251                 err = err2;
1252         /*
1253          * Update the file handle to get the new inode info.
1254          */
1255         if (!err)
1256                 err = fh_update(resfhp);
1257 out:
1258         dput(dchild);
1259         return err;
1260 
1261 out_nfserr:
1262         err = nfserrno(host_err);
1263         goto out;
1264 }
1265 
1266 /*
1267  * Create a filesystem object (regular, directory, special).
1268  * Note that the parent directory is left locked.
1269  *
1270  * N.B. Every call to nfsd_create needs an fh_put for _both_ fhp and resfhp
1271  */
1272 __be32
1273 nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
1274                 char *fname, int flen, struct iattr *iap,
1275                 int type, dev_t rdev, struct svc_fh *resfhp)
1276 {
1277         struct dentry   *dentry, *dchild = NULL;
1278         struct inode    *dirp;
1279         __be32          err;
1280         int             host_err;
1281 
1282         if (isdotent(fname, flen))
1283                 return nfserr_exist;
1284 
1285         err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_NOP);
1286         if (err)
1287                 return err;
1288 
1289         dentry = fhp->fh_dentry;
1290         dirp = d_inode(dentry);
1291 
1292         host_err = fh_want_write(fhp);
1293         if (host_err)
1294                 return nfserrno(host_err);
1295 
1296         fh_lock_nested(fhp, I_MUTEX_PARENT);
1297         dchild = lookup_one_len(fname, dentry, flen);
1298         host_err = PTR_ERR(dchild);
1299         if (IS_ERR(dchild))
1300                 return nfserrno(host_err);
1301         err = fh_compose(resfhp, fhp->fh_export, dchild, fhp);
1302         /*
1303          * We unconditionally drop our ref to dchild as fh_compose will have
1304          * already grabbed its own ref for it.
1305          */
1306         dput(dchild);
1307         if (err)
1308                 return err;
1309         return nfsd_create_locked(rqstp, fhp, fname, flen, iap, type,
1310                                         rdev, resfhp);
1311 }
1312 
1313 #ifdef CONFIG_NFSD_V3
1314 
1315 /*
1316  * NFSv3 and NFSv4 version of nfsd_create
1317  */
1318 __be32
1319 do_nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
1320                 char *fname, int flen, struct iattr *iap,
1321                 struct svc_fh *resfhp, int createmode, u32 *verifier,
1322                 bool *truncp, bool *created)
1323 {
1324         struct dentry   *dentry, *dchild = NULL;
1325         struct inode    *dirp;
1326         __be32          err;
1327         int             host_err;
1328         __u32           v_mtime=0, v_atime=0;
1329 
1330         err = nfserr_perm;
1331         if (!flen)
1332                 goto out;
1333         err = nfserr_exist;
1334         if (isdotent(fname, flen))
1335                 goto out;
1336         if (!(iap->ia_valid & ATTR_MODE))
1337                 iap->ia_mode = 0;
1338         err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_EXEC);
1339         if (err)
1340                 goto out;
1341 
1342         dentry = fhp->fh_dentry;
1343         dirp = d_inode(dentry);
1344 
1345         host_err = fh_want_write(fhp);
1346         if (host_err)
1347                 goto out_nfserr;
1348 
1349         fh_lock_nested(fhp, I_MUTEX_PARENT);
1350 
1351         /*
1352          * Compose the response file handle.
1353          */
1354         dchild = lookup_one_len(fname, dentry, flen);
1355         host_err = PTR_ERR(dchild);
1356         if (IS_ERR(dchild))
1357                 goto out_nfserr;
1358 
1359         /* If file doesn't exist, check for permissions to create one */
1360         if (d_really_is_negative(dchild)) {
1361                 err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
1362                 if (err)
1363                         goto out;
1364         }
1365 
1366         err = fh_compose(resfhp, fhp->fh_export, dchild, fhp);
1367         if (err)
1368                 goto out;
1369 
1370         if (nfsd_create_is_exclusive(createmode)) {
1371                 /* solaris7 gets confused (bugid 4218508) if these have
1372                  * the high bit set, so just clear the high bits. If this is
1373                  * ever changed to use different attrs for storing the
1374                  * verifier, then do_open_lookup() will also need to be fixed
1375                  * accordingly.
1376                  */
1377                 v_mtime = verifier[0]&0x7fffffff;
1378                 v_atime = verifier[1]&0x7fffffff;
1379         }
1380         
1381         if (d_really_is_positive(dchild)) {
1382                 err = 0;
1383 
1384                 switch (createmode) {
1385                 case NFS3_CREATE_UNCHECKED:
1386                         if (! d_is_reg(dchild))
1387                                 goto out;
1388                         else if (truncp) {
1389                                 /* in nfsv4, we need to treat this case a little
1390                                  * differently.  we don't want to truncate the
1391                                  * file now; this would be wrong if the OPEN
1392                                  * fails for some other reason.  furthermore,
1393                                  * if the size is nonzero, we should ignore it
1394                                  * according to spec!
1395                                  */
1396                                 *truncp = (iap->ia_valid & ATTR_SIZE) && !iap->ia_size;
1397                         }
1398                         else {
1399                                 iap->ia_valid &= ATTR_SIZE;
1400                                 goto set_attr;
1401                         }
1402                         break;
1403                 case NFS3_CREATE_EXCLUSIVE:
1404                         if (   d_inode(dchild)->i_mtime.tv_sec == v_mtime
1405                             && d_inode(dchild)->i_atime.tv_sec == v_atime
1406                             && d_inode(dchild)->i_size  == 0 ) {
1407                                 if (created)
1408                                         *created = 1;
1409                                 break;
1410                         }
1411                 case NFS4_CREATE_EXCLUSIVE4_1:
1412                         if (   d_inode(dchild)->i_mtime.tv_sec == v_mtime
1413                             && d_inode(dchild)->i_atime.tv_sec == v_atime
1414                             && d_inode(dchild)->i_size  == 0 ) {
1415                                 if (created)
1416                                         *created = 1;
1417                                 goto set_attr;
1418                         }
1419                          /* fallthru */
1420                 case NFS3_CREATE_GUARDED:
1421                         err = nfserr_exist;
1422                 }
1423                 fh_drop_write(fhp);
1424                 goto out;
1425         }
1426 
1427         host_err = vfs_create(dirp, dchild, iap->ia_mode, true);
1428         if (host_err < 0) {
1429                 fh_drop_write(fhp);
1430                 goto out_nfserr;
1431         }
1432         if (created)
1433                 *created = 1;
1434 
1435         nfsd_check_ignore_resizing(iap);
1436 
1437         if (nfsd_create_is_exclusive(createmode)) {
1438                 /* Cram the verifier into atime/mtime */
1439                 iap->ia_valid = ATTR_MTIME|ATTR_ATIME
1440                         | ATTR_MTIME_SET|ATTR_ATIME_SET;
1441                 /* XXX someone who knows this better please fix it for nsec */ 
1442                 iap->ia_mtime.tv_sec = v_mtime;
1443                 iap->ia_atime.tv_sec = v_atime;
1444                 iap->ia_mtime.tv_nsec = 0;
1445                 iap->ia_atime.tv_nsec = 0;
1446         }
1447 
1448  set_attr:
1449         err = nfsd_create_setattr(rqstp, resfhp, iap);
1450 
1451         /*
1452          * nfsd_create_setattr already committed the child
1453          * (and possibly also the parent).
1454          */
1455         if (!err)
1456                 err = nfserrno(commit_metadata(fhp));
1457 
1458         /*
1459          * Update the filehandle to get the new inode info.
1460          */
1461         if (!err)
1462                 err = fh_update(resfhp);
1463 
1464  out:
1465         fh_unlock(fhp);
1466         if (dchild && !IS_ERR(dchild))
1467                 dput(dchild);
1468         fh_drop_write(fhp);
1469         return err;
1470  
1471  out_nfserr:
1472         err = nfserrno(host_err);
1473         goto out;
1474 }
1475 #endif /* CONFIG_NFSD_V3 */
1476 
1477 /*
1478  * Read a symlink. On entry, *lenp must contain the maximum path length that
1479  * fits into the buffer. On return, it contains the true length.
1480  * N.B. After this call fhp needs an fh_put
1481  */
1482 __be32
1483 nfsd_readlink(struct svc_rqst *rqstp, struct svc_fh *fhp, char *buf, int *lenp)
1484 {
1485         __be32          err;
1486         const char *link;
1487         struct path path;
1488         DEFINE_DELAYED_CALL(done);
1489         int len;
1490 
1491         err = fh_verify(rqstp, fhp, S_IFLNK, NFSD_MAY_NOP);
1492         if (unlikely(err))
1493                 return err;
1494 
1495         path.mnt = fhp->fh_export->ex_path.mnt;
1496         path.dentry = fhp->fh_dentry;
1497 
1498         if (unlikely(!d_is_symlink(path.dentry)))
1499                 return nfserr_inval;
1500 
1501         touch_atime(&path);
1502 
1503         link = vfs_get_link(path.dentry, &done);
1504         if (IS_ERR(link))
1505                 return nfserrno(PTR_ERR(link));
1506 
1507         len = strlen(link);
1508         if (len < *lenp)
1509                 *lenp = len;
1510         memcpy(buf, link, *lenp);
1511         do_delayed_call(&done);
1512         return 0;
1513 }
1514 
1515 /*
1516  * Create a symlink and look up its inode
1517  * N.B. After this call _both_ fhp and resfhp need an fh_put
1518  */
1519 __be32
1520 nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
1521                                 char *fname, int flen,
1522                                 char *path,
1523                                 struct svc_fh *resfhp)
1524 {
1525         struct dentry   *dentry, *dnew;
1526         __be32          err, cerr;
1527         int             host_err;
1528 
1529         err = nfserr_noent;
1530         if (!flen || path[0] == '\0')
1531                 goto out;
1532         err = nfserr_exist;
1533         if (isdotent(fname, flen))
1534                 goto out;
1535 
1536         err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
1537         if (err)
1538                 goto out;
1539 
1540         host_err = fh_want_write(fhp);
1541         if (host_err)
1542                 goto out_nfserr;
1543 
1544         fh_lock(fhp);
1545         dentry = fhp->fh_dentry;
1546         dnew = lookup_one_len(fname, dentry, flen);
1547         host_err = PTR_ERR(dnew);
1548         if (IS_ERR(dnew))
1549                 goto out_nfserr;
1550 
1551         host_err = vfs_symlink(d_inode(dentry), dnew, path);
1552         err = nfserrno(host_err);
1553         if (!err)
1554                 err = nfserrno(commit_metadata(fhp));
1555         fh_unlock(fhp);
1556 
1557         fh_drop_write(fhp);
1558 
1559         cerr = fh_compose(resfhp, fhp->fh_export, dnew, fhp);
1560         dput(dnew);
1561         if (err==0) err = cerr;
1562 out:
1563         return err;
1564 
1565 out_nfserr:
1566         err = nfserrno(host_err);
1567         goto out;
1568 }
1569 
1570 /*
1571  * Create a hardlink
1572  * N.B. After this call _both_ ffhp and tfhp need an fh_put
1573  */
1574 __be32
1575 nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
1576                                 char *name, int len, struct svc_fh *tfhp)
1577 {
1578         struct dentry   *ddir, *dnew, *dold;
1579         struct inode    *dirp;
1580         __be32          err;
1581         int             host_err;
1582 
1583         err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_CREATE);
1584         if (err)
1585                 goto out;
1586         err = fh_verify(rqstp, tfhp, 0, NFSD_MAY_NOP);
1587         if (err)
1588                 goto out;
1589         err = nfserr_isdir;
1590         if (d_is_dir(tfhp->fh_dentry))
1591                 goto out;
1592         err = nfserr_perm;
1593         if (!len)
1594                 goto out;
1595         err = nfserr_exist;
1596         if (isdotent(name, len))
1597                 goto out;
1598 
1599         host_err = fh_want_write(tfhp);
1600         if (host_err) {
1601                 err = nfserrno(host_err);
1602                 goto out;
1603         }
1604 
1605         fh_lock_nested(ffhp, I_MUTEX_PARENT);
1606         ddir = ffhp->fh_dentry;
1607         dirp = d_inode(ddir);
1608 
1609         dnew = lookup_one_len(name, ddir, len);
1610         host_err = PTR_ERR(dnew);
1611         if (IS_ERR(dnew))
1612                 goto out_nfserr;
1613 
1614         dold = tfhp->fh_dentry;
1615 
1616         err = nfserr_noent;
1617         if (d_really_is_negative(dold))
1618                 goto out_dput;
1619         host_err = vfs_link(dold, dirp, dnew, NULL);
1620         if (!host_err) {
1621                 err = nfserrno(commit_metadata(ffhp));
1622                 if (!err)
1623                         err = nfserrno(commit_metadata(tfhp));
1624         } else {
1625                 if (host_err == -EXDEV && rqstp->rq_vers == 2)
1626                         err = nfserr_acces;
1627                 else
1628                         err = nfserrno(host_err);
1629         }
1630 out_dput:
1631         dput(dnew);
1632 out_unlock:
1633         fh_unlock(ffhp);
1634         fh_drop_write(tfhp);
1635 out:
1636         return err;
1637 
1638 out_nfserr:
1639         err = nfserrno(host_err);
1640         goto out_unlock;
1641 }
1642 
1643 /*
1644  * Rename a file
1645  * N.B. After this call _both_ ffhp and tfhp need an fh_put
1646  */
1647 __be32
1648 nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
1649                             struct svc_fh *tfhp, char *tname, int tlen)
1650 {
1651         struct dentry   *fdentry, *tdentry, *odentry, *ndentry, *trap;
1652         struct inode    *fdir, *tdir;
1653         __be32          err;
1654         int             host_err;
1655 
1656         err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_REMOVE);
1657         if (err)
1658                 goto out;
1659         err = fh_verify(rqstp, tfhp, S_IFDIR, NFSD_MAY_CREATE);
1660         if (err)
1661                 goto out;
1662 
1663         fdentry = ffhp->fh_dentry;
1664         fdir = d_inode(fdentry);
1665 
1666         tdentry = tfhp->fh_dentry;
1667         tdir = d_inode(tdentry);
1668 
1669         err = nfserr_perm;
1670         if (!flen || isdotent(fname, flen) || !tlen || isdotent(tname, tlen))
1671                 goto out;
1672 
1673         host_err = fh_want_write(ffhp);
1674         if (host_err) {
1675                 err = nfserrno(host_err);
1676                 goto out;
1677         }
1678 
1679         /* cannot use fh_lock as we need deadlock protective ordering
1680          * so do it by hand */
1681         trap = lock_rename(tdentry, fdentry);
1682         ffhp->fh_locked = tfhp->fh_locked = true;
1683         fill_pre_wcc(ffhp);
1684         fill_pre_wcc(tfhp);
1685 
1686         odentry = lookup_one_len(fname, fdentry, flen);
1687         host_err = PTR_ERR(odentry);
1688         if (IS_ERR(odentry))
1689                 goto out_nfserr;
1690 
1691         host_err = -ENOENT;
1692         if (d_really_is_negative(odentry))
1693                 goto out_dput_old;
1694         host_err = -EINVAL;
1695         if (odentry == trap)
1696                 goto out_dput_old;
1697 
1698         ndentry = lookup_one_len(tname, tdentry, tlen);
1699         host_err = PTR_ERR(ndentry);
1700         if (IS_ERR(ndentry))
1701                 goto out_dput_old;
1702         host_err = -ENOTEMPTY;
1703         if (ndentry == trap)
1704                 goto out_dput_new;
1705 
1706         host_err = -EXDEV;
1707         if (ffhp->fh_export->ex_path.mnt != tfhp->fh_export->ex_path.mnt)
1708                 goto out_dput_new;
1709         if (ffhp->fh_export->ex_path.dentry != tfhp->fh_export->ex_path.dentry)
1710                 goto out_dput_new;
1711 
1712         host_err = vfs_rename(fdir, odentry, tdir, ndentry, NULL, 0);
1713         if (!host_err) {
1714                 host_err = commit_metadata(tfhp);
1715                 if (!host_err)
1716                         host_err = commit_metadata(ffhp);
1717         }
1718  out_dput_new:
1719         dput(ndentry);
1720  out_dput_old:
1721         dput(odentry);
1722  out_nfserr:
1723         err = nfserrno(host_err);
1724         /*
1725          * We cannot rely on fh_unlock on the two filehandles,
1726          * as that would do the wrong thing if the two directories
1727          * were the same, so again we do it by hand.
1728          */
1729         fill_post_wcc(ffhp);
1730         fill_post_wcc(tfhp);
1731         unlock_rename(tdentry, fdentry);
1732         ffhp->fh_locked = tfhp->fh_locked = false;
1733         fh_drop_write(ffhp);
1734 
1735 out:
1736         return err;
1737 }
1738 
1739 /*
1740  * Unlink a file or directory
1741  * N.B. After this call fhp needs an fh_put
1742  */
1743 __be32
1744 nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
1745                                 char *fname, int flen)
1746 {
1747         struct dentry   *dentry, *rdentry;
1748         struct inode    *dirp;
1749         __be32          err;
1750         int             host_err;
1751 
1752         err = nfserr_acces;
1753         if (!flen || isdotent(fname, flen))
1754                 goto out;
1755         err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_REMOVE);
1756         if (err)
1757                 goto out;
1758 
1759         host_err = fh_want_write(fhp);
1760         if (host_err)
1761                 goto out_nfserr;
1762 
1763         fh_lock_nested(fhp, I_MUTEX_PARENT);
1764         dentry = fhp->fh_dentry;
1765         dirp = d_inode(dentry);
1766 
1767         rdentry = lookup_one_len(fname, dentry, flen);
1768         host_err = PTR_ERR(rdentry);
1769         if (IS_ERR(rdentry))
1770                 goto out_nfserr;
1771 
1772         if (d_really_is_negative(rdentry)) {
1773                 dput(rdentry);
1774                 err = nfserr_noent;
1775                 goto out;
1776         }
1777 
1778         if (!type)
1779                 type = d_inode(rdentry)->i_mode & S_IFMT;
1780 
1781         if (type != S_IFDIR)
1782                 host_err = vfs_unlink(dirp, rdentry, NULL);
1783         else
1784                 host_err = vfs_rmdir(dirp, rdentry);
1785         if (!host_err)
1786                 host_err = commit_metadata(fhp);
1787         dput(rdentry);
1788 
1789 out_nfserr:
1790         err = nfserrno(host_err);
1791 out:
1792         return err;
1793 }
1794 
1795 /*
1796  * We do this buffering because we must not call back into the file
1797  * system's ->lookup() method from the filldir callback. That may well
1798  * deadlock a number of file systems.
1799  *
1800  * This is based heavily on the implementation of same in XFS.
1801  */
1802 struct buffered_dirent {
1803         u64             ino;
1804         loff_t          offset;
1805         int             namlen;
1806         unsigned int    d_type;
1807         char            name[];
1808 };
1809 
1810 struct readdir_data {
1811         struct dir_context ctx;
1812         char            *dirent;
1813         size_t          used;
1814         int             full;
1815 };
1816 
1817 static int nfsd_buffered_filldir(struct dir_context *ctx, const char *name,
1818                                  int namlen, loff_t offset, u64 ino,
1819                                  unsigned int d_type)
1820 {
1821         struct readdir_data *buf =
1822                 container_of(ctx, struct readdir_data, ctx);
1823         struct buffered_dirent *de = (void *)(buf->dirent + buf->used);
1824         unsigned int reclen;
1825 
1826         reclen = ALIGN(sizeof(struct buffered_dirent) + namlen, sizeof(u64));
1827         if (buf->used + reclen > PAGE_SIZE) {
1828                 buf->full = 1;
1829                 return -EINVAL;
1830         }
1831 
1832         de->namlen = namlen;
1833         de->offset = offset;
1834         de->ino = ino;
1835         de->d_type = d_type;
1836         memcpy(de->name, name, namlen);
1837         buf->used += reclen;
1838 
1839         return 0;
1840 }
1841 
1842 static __be32 nfsd_buffered_readdir(struct file *file, nfsd_filldir_t func,
1843                                     struct readdir_cd *cdp, loff_t *offsetp)
1844 {
1845         struct buffered_dirent *de;
1846         int host_err;
1847         int size;
1848         loff_t offset;
1849         struct readdir_data buf = {
1850                 .ctx.actor = nfsd_buffered_filldir,
1851                 .dirent = (void *)__get_free_page(GFP_KERNEL)
1852         };
1853 
1854         if (!buf.dirent)
1855                 return nfserrno(-ENOMEM);
1856 
1857         offset = *offsetp;
1858 
1859         while (1) {
1860                 unsigned int reclen;
1861 
1862                 cdp->err = nfserr_eof; /* will be cleared on successful read */
1863                 buf.used = 0;
1864                 buf.full = 0;
1865 
1866                 host_err = iterate_dir(file, &buf.ctx);
1867                 if (buf.full)
1868                         host_err = 0;
1869 
1870                 if (host_err < 0)
1871                         break;
1872 
1873                 size = buf.used;
1874 
1875                 if (!size)
1876                         break;
1877 
1878                 de = (struct buffered_dirent *)buf.dirent;
1879                 while (size > 0) {
1880                         offset = de->offset;
1881 
1882                         if (func(cdp, de->name, de->namlen, de->offset,
1883                                  de->ino, de->d_type))
1884                                 break;
1885 
1886                         if (cdp->err != nfs_ok)
1887                                 break;
1888 
1889                         reclen = ALIGN(sizeof(*de) + de->namlen,
1890                                        sizeof(u64));
1891                         size -= reclen;
1892                         de = (struct buffered_dirent *)((char *)de + reclen);
1893                 }
1894                 if (size > 0) /* We bailed out early */
1895                         break;
1896 
1897                 offset = vfs_llseek(file, 0, SEEK_CUR);
1898         }
1899 
1900         free_page((unsigned long)(buf.dirent));
1901 
1902         if (host_err)
1903                 return nfserrno(host_err);
1904 
1905         *offsetp = offset;
1906         return cdp->err;
1907 }
1908 
1909 /*
1910  * Read entries from a directory.
1911  * The  NFSv3/4 verifier we ignore for now.
1912  */
1913 __be32
1914 nfsd_readdir(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t *offsetp, 
1915              struct readdir_cd *cdp, nfsd_filldir_t func)
1916 {
1917         __be32          err;
1918         struct file     *file;
1919         loff_t          offset = *offsetp;
1920         int             may_flags = NFSD_MAY_READ;
1921 
1922         /* NFSv2 only supports 32 bit cookies */
1923         if (rqstp->rq_vers > 2)
1924                 may_flags |= NFSD_MAY_64BIT_COOKIE;
1925 
1926         err = nfsd_open(rqstp, fhp, S_IFDIR, may_flags, &file);
1927         if (err)
1928                 goto out;
1929 
1930         offset = vfs_llseek(file, offset, SEEK_SET);
1931         if (offset < 0) {
1932                 err = nfserrno((int)offset);
1933                 goto out_close;
1934         }
1935 
1936         err = nfsd_buffered_readdir(file, func, cdp, offsetp);
1937 
1938         if (err == nfserr_eof || err == nfserr_toosmall)
1939                 err = nfs_ok; /* can still be found in ->err */
1940 out_close:
1941         fput(file);
1942 out:
1943         return err;
1944 }
1945 
1946 /*
1947  * Get file system stats
1948  * N.B. After this call fhp needs an fh_put
1949  */
1950 __be32
1951 nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat, int access)
1952 {
1953         __be32 err;
1954 
1955         err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP | access);
1956         if (!err) {
1957                 struct path path = {
1958                         .mnt    = fhp->fh_export->ex_path.mnt,
1959                         .dentry = fhp->fh_dentry,
1960                 };
1961                 if (vfs_statfs(&path, stat))
1962                         err = nfserr_io;
1963         }
1964         return err;
1965 }
1966 
1967 static int exp_rdonly(struct svc_rqst *rqstp, struct svc_export *exp)
1968 {
1969         return nfsexp_flags(rqstp, exp) & NFSEXP_READONLY;
1970 }
1971 
1972 /*
1973  * Check for a user's access permissions to this inode.
1974  */
1975 __be32
1976 nfsd_permission(struct svc_rqst *rqstp, struct svc_export *exp,
1977                                         struct dentry *dentry, int acc)
1978 {
1979         struct inode    *inode = d_inode(dentry);
1980         int             err;
1981 
1982         if ((acc & NFSD_MAY_MASK) == NFSD_MAY_NOP)
1983                 return 0;
1984 #if 0
1985         dprintk("nfsd: permission 0x%x%s%s%s%s%s%s%s mode 0%o%s%s%s\n",
1986                 acc,
1987                 (acc & NFSD_MAY_READ)?  " read"  : "",
1988                 (acc & NFSD_MAY_WRITE)? " write" : "",
1989                 (acc & NFSD_MAY_EXEC)?  " exec"  : "",
1990                 (acc & NFSD_MAY_SATTR)? " sattr" : "",
1991                 (acc & NFSD_MAY_TRUNC)? " trunc" : "",
1992                 (acc & NFSD_MAY_LOCK)?  " lock"  : "",
1993                 (acc & NFSD_MAY_OWNER_OVERRIDE)? " owneroverride" : "",
1994                 inode->i_mode,
1995                 IS_IMMUTABLE(inode)?    " immut" : "",
1996                 IS_APPEND(inode)?       " append" : "",
1997                 __mnt_is_readonly(exp->ex_path.mnt)?    " ro" : "");
1998         dprintk("      owner %d/%d user %d/%d\n",
1999                 inode->i_uid, inode->i_gid, current_fsuid(), current_fsgid());
2000 #endif
2001 
2002         /* Normally we reject any write/sattr etc access on a read-only file
2003          * system.  But if it is IRIX doing check on write-access for a 
2004          * device special file, we ignore rofs.
2005          */
2006         if (!(acc & NFSD_MAY_LOCAL_ACCESS))
2007                 if (acc & (NFSD_MAY_WRITE | NFSD_MAY_SATTR | NFSD_MAY_TRUNC)) {
2008                         if (exp_rdonly(rqstp, exp) ||
2009                             __mnt_is_readonly(exp->ex_path.mnt))
2010                                 return nfserr_rofs;
2011                         if (/* (acc & NFSD_MAY_WRITE) && */ IS_IMMUTABLE(inode))
2012                                 return nfserr_perm;
2013                 }
2014         if ((acc & NFSD_MAY_TRUNC) && IS_APPEND(inode))
2015                 return nfserr_perm;
2016 
2017         if (acc & NFSD_MAY_LOCK) {
2018                 /* If we cannot rely on authentication in NLM requests,
2019                  * just allow locks, otherwise require read permission, or
2020                  * ownership
2021                  */
2022                 if (exp->ex_flags & NFSEXP_NOAUTHNLM)
2023                         return 0;
2024                 else
2025                         acc = NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE;
2026         }
2027         /*
2028          * The file owner always gets access permission for accesses that
2029          * would normally be checked at open time. This is to make
2030          * file access work even when the client has done a fchmod(fd, 0).
2031          *
2032          * However, `cp foo bar' should fail nevertheless when bar is
2033          * readonly. A sensible way to do this might be to reject all
2034          * attempts to truncate a read-only file, because a creat() call
2035          * always implies file truncation.
2036          * ... but this isn't really fair.  A process may reasonably call
2037          * ftruncate on an open file descriptor on a file with perm 000.
2038          * We must trust the client to do permission checking - using "ACCESS"
2039          * with NFSv3.
2040          */
2041         if ((acc & NFSD_MAY_OWNER_OVERRIDE) &&
2042             uid_eq(inode->i_uid, current_fsuid()))
2043                 return 0;
2044 
2045         /* This assumes  NFSD_MAY_{READ,WRITE,EXEC} == MAY_{READ,WRITE,EXEC} */
2046         err = inode_permission(inode, acc & (MAY_READ|MAY_WRITE|MAY_EXEC));
2047 
2048         /* Allow read access to binaries even when mode 111 */
2049         if (err == -EACCES && S_ISREG(inode->i_mode) &&
2050              (acc == (NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE) ||
2051               acc == (NFSD_MAY_READ | NFSD_MAY_READ_IF_EXEC)))
2052                 err = inode_permission(inode, MAY_EXEC);
2053 
2054         return err? nfserrno(err) : 0;
2055 }
2056 
2057 void
2058 nfsd_racache_shutdown(void)
2059 {
2060         struct raparms *raparm, *last_raparm;
2061         unsigned int i;
2062 
2063         dprintk("nfsd: freeing readahead buffers.\n");
2064 
2065         for (i = 0; i < RAPARM_HASH_SIZE; i++) {
2066                 raparm = raparm_hash[i].pb_head;
2067                 while(raparm) {
2068                         last_raparm = raparm;
2069                         raparm = raparm->p_next;
2070                         kfree(last_raparm);
2071                 }
2072                 raparm_hash[i].pb_head = NULL;
2073         }
2074 }
2075 /*
2076  * Initialize readahead param cache
2077  */
2078 int
2079 nfsd_racache_init(int cache_size)
2080 {
2081         int     i;
2082         int     j = 0;
2083         int     nperbucket;
2084         struct raparms **raparm = NULL;
2085 
2086 
2087         if (raparm_hash[0].pb_head)
2088                 return 0;
2089         nperbucket = DIV_ROUND_UP(cache_size, RAPARM_HASH_SIZE);
2090         nperbucket = max(2, nperbucket);
2091         cache_size = nperbucket * RAPARM_HASH_SIZE;
2092 
2093         dprintk("nfsd: allocating %d readahead buffers.\n", cache_size);
2094 
2095         for (i = 0; i < RAPARM_HASH_SIZE; i++) {
2096                 spin_lock_init(&raparm_hash[i].pb_lock);
2097 
2098                 raparm = &raparm_hash[i].pb_head;
2099                 for (j = 0; j < nperbucket; j++) {
2100                         *raparm = kzalloc(sizeof(struct raparms), GFP_KERNEL);
2101                         if (!*raparm)
2102                                 goto out_nomem;
2103                         raparm = &(*raparm)->p_next;
2104                 }
2105                 *raparm = NULL;
2106         }
2107 
2108         nfsdstats.ra_size = cache_size;
2109         return 0;
2110 
2111 out_nomem:
2112         dprintk("nfsd: kmalloc failed, freeing readahead buffers\n");
2113         nfsd_racache_shutdown();
2114         return -ENOMEM;
2115 }
2116 

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