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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(vfs_clone_file_range(src, src_pos, dst, dst_pos,
545                                              count));
546 }
547 
548 ssize_t nfsd_copy_file_range(struct file *src, u64 src_pos, struct file *dst,
549                              u64 dst_pos, u64 count)
550 {
551 
552         /*
553          * Limit copy to 4MB to prevent indefinitely blocking an nfsd
554          * thread and client rpc slot.  The choice of 4MB is somewhat
555          * arbitrary.  We might instead base this on r/wsize, or make it
556          * tunable, or use a time instead of a byte limit, or implement
557          * asynchronous copy.  In theory a client could also recognize a
558          * limit like this and pipeline multiple COPY requests.
559          */
560         count = min_t(u64, count, 1 << 22);
561         return vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0);
562 }
563 
564 __be32 nfsd4_vfs_fallocate(struct svc_rqst *rqstp, struct svc_fh *fhp,
565                            struct file *file, loff_t offset, loff_t len,
566                            int flags)
567 {
568         int error;
569 
570         if (!S_ISREG(file_inode(file)->i_mode))
571                 return nfserr_inval;
572 
573         error = vfs_fallocate(file, flags, offset, len);
574         if (!error)
575                 error = commit_metadata(fhp);
576 
577         return nfserrno(error);
578 }
579 #endif /* defined(CONFIG_NFSD_V4) */
580 
581 #ifdef CONFIG_NFSD_V3
582 /*
583  * Check server access rights to a file system object
584  */
585 struct accessmap {
586         u32             access;
587         int             how;
588 };
589 static struct accessmap nfs3_regaccess[] = {
590     {   NFS3_ACCESS_READ,       NFSD_MAY_READ                   },
591     {   NFS3_ACCESS_EXECUTE,    NFSD_MAY_EXEC                   },
592     {   NFS3_ACCESS_MODIFY,     NFSD_MAY_WRITE|NFSD_MAY_TRUNC   },
593     {   NFS3_ACCESS_EXTEND,     NFSD_MAY_WRITE                  },
594 
595     {   0,                      0                               }
596 };
597 
598 static struct accessmap nfs3_diraccess[] = {
599     {   NFS3_ACCESS_READ,       NFSD_MAY_READ                   },
600     {   NFS3_ACCESS_LOOKUP,     NFSD_MAY_EXEC                   },
601     {   NFS3_ACCESS_MODIFY,     NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC},
602     {   NFS3_ACCESS_EXTEND,     NFSD_MAY_EXEC|NFSD_MAY_WRITE    },
603     {   NFS3_ACCESS_DELETE,     NFSD_MAY_REMOVE                 },
604 
605     {   0,                      0                               }
606 };
607 
608 static struct accessmap nfs3_anyaccess[] = {
609         /* Some clients - Solaris 2.6 at least, make an access call
610          * to the server to check for access for things like /dev/null
611          * (which really, the server doesn't care about).  So
612          * We provide simple access checking for them, looking
613          * mainly at mode bits, and we make sure to ignore read-only
614          * filesystem checks
615          */
616     {   NFS3_ACCESS_READ,       NFSD_MAY_READ                   },
617     {   NFS3_ACCESS_EXECUTE,    NFSD_MAY_EXEC                   },
618     {   NFS3_ACCESS_MODIFY,     NFSD_MAY_WRITE|NFSD_MAY_LOCAL_ACCESS    },
619     {   NFS3_ACCESS_EXTEND,     NFSD_MAY_WRITE|NFSD_MAY_LOCAL_ACCESS    },
620 
621     {   0,                      0                               }
622 };
623 
624 __be32
625 nfsd_access(struct svc_rqst *rqstp, struct svc_fh *fhp, u32 *access, u32 *supported)
626 {
627         struct accessmap        *map;
628         struct svc_export       *export;
629         struct dentry           *dentry;
630         u32                     query, result = 0, sresult = 0;
631         __be32                  error;
632 
633         error = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP);
634         if (error)
635                 goto out;
636 
637         export = fhp->fh_export;
638         dentry = fhp->fh_dentry;
639 
640         if (d_is_reg(dentry))
641                 map = nfs3_regaccess;
642         else if (d_is_dir(dentry))
643                 map = nfs3_diraccess;
644         else
645                 map = nfs3_anyaccess;
646 
647 
648         query = *access;
649         for  (; map->access; map++) {
650                 if (map->access & query) {
651                         __be32 err2;
652 
653                         sresult |= map->access;
654 
655                         err2 = nfsd_permission(rqstp, export, dentry, map->how);
656                         switch (err2) {
657                         case nfs_ok:
658                                 result |= map->access;
659                                 break;
660                                 
661                         /* the following error codes just mean the access was not allowed,
662                          * rather than an error occurred */
663                         case nfserr_rofs:
664                         case nfserr_acces:
665                         case nfserr_perm:
666                                 /* simply don't "or" in the access bit. */
667                                 break;
668                         default:
669                                 error = err2;
670                                 goto out;
671                         }
672                 }
673         }
674         *access = result;
675         if (supported)
676                 *supported = sresult;
677 
678  out:
679         return error;
680 }
681 #endif /* CONFIG_NFSD_V3 */
682 
683 static int nfsd_open_break_lease(struct inode *inode, int access)
684 {
685         unsigned int mode;
686 
687         if (access & NFSD_MAY_NOT_BREAK_LEASE)
688                 return 0;
689         mode = (access & NFSD_MAY_WRITE) ? O_WRONLY : O_RDONLY;
690         return break_lease(inode, mode | O_NONBLOCK);
691 }
692 
693 /*
694  * Open an existing file or directory.
695  * The may_flags argument indicates the type of open (read/write/lock)
696  * and additional flags.
697  * N.B. After this call fhp needs an fh_put
698  */
699 __be32
700 nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
701                         int may_flags, struct file **filp)
702 {
703         struct path     path;
704         struct inode    *inode;
705         struct file     *file;
706         int             flags = O_RDONLY|O_LARGEFILE;
707         __be32          err;
708         int             host_err = 0;
709 
710         validate_process_creds();
711 
712         /*
713          * If we get here, then the client has already done an "open",
714          * and (hopefully) checked permission - so allow OWNER_OVERRIDE
715          * in case a chmod has now revoked permission.
716          *
717          * Arguably we should also allow the owner override for
718          * directories, but we never have and it doesn't seem to have
719          * caused anyone a problem.  If we were to change this, note
720          * also that our filldir callbacks would need a variant of
721          * lookup_one_len that doesn't check permissions.
722          */
723         if (type == S_IFREG)
724                 may_flags |= NFSD_MAY_OWNER_OVERRIDE;
725         err = fh_verify(rqstp, fhp, type, may_flags);
726         if (err)
727                 goto out;
728 
729         path.mnt = fhp->fh_export->ex_path.mnt;
730         path.dentry = fhp->fh_dentry;
731         inode = d_inode(path.dentry);
732 
733         /* Disallow write access to files with the append-only bit set
734          * or any access when mandatory locking enabled
735          */
736         err = nfserr_perm;
737         if (IS_APPEND(inode) && (may_flags & NFSD_MAY_WRITE))
738                 goto out;
739         /*
740          * We must ignore files (but only files) which might have mandatory
741          * locks on them because there is no way to know if the accesser has
742          * the lock.
743          */
744         if (S_ISREG((inode)->i_mode) && mandatory_lock(inode))
745                 goto out;
746 
747         if (!inode->i_fop)
748                 goto out;
749 
750         host_err = nfsd_open_break_lease(inode, may_flags);
751         if (host_err) /* NOMEM or WOULDBLOCK */
752                 goto out_nfserr;
753 
754         if (may_flags & NFSD_MAY_WRITE) {
755                 if (may_flags & NFSD_MAY_READ)
756                         flags = O_RDWR|O_LARGEFILE;
757                 else
758                         flags = O_WRONLY|O_LARGEFILE;
759         }
760 
761         file = dentry_open(&path, flags, current_cred());
762         if (IS_ERR(file)) {
763                 host_err = PTR_ERR(file);
764                 goto out_nfserr;
765         }
766 
767         host_err = ima_file_check(file, may_flags);
768         if (host_err) {
769                 fput(file);
770                 goto out_nfserr;
771         }
772 
773         if (may_flags & NFSD_MAY_64BIT_COOKIE)
774                 file->f_mode |= FMODE_64BITHASH;
775         else
776                 file->f_mode |= FMODE_32BITHASH;
777 
778         *filp = file;
779 out_nfserr:
780         err = nfserrno(host_err);
781 out:
782         validate_process_creds();
783         return err;
784 }
785 
786 struct raparms *
787 nfsd_init_raparms(struct file *file)
788 {
789         struct inode *inode = file_inode(file);
790         dev_t dev = inode->i_sb->s_dev;
791         ino_t ino = inode->i_ino;
792         struct raparms  *ra, **rap, **frap = NULL;
793         int depth = 0;
794         unsigned int hash;
795         struct raparm_hbucket *rab;
796 
797         hash = jhash_2words(dev, ino, 0xfeedbeef) & RAPARM_HASH_MASK;
798         rab = &raparm_hash[hash];
799 
800         spin_lock(&rab->pb_lock);
801         for (rap = &rab->pb_head; (ra = *rap); rap = &ra->p_next) {
802                 if (ra->p_ino == ino && ra->p_dev == dev)
803                         goto found;
804                 depth++;
805                 if (ra->p_count == 0)
806                         frap = rap;
807         }
808         depth = nfsdstats.ra_size;
809         if (!frap) {    
810                 spin_unlock(&rab->pb_lock);
811                 return NULL;
812         }
813         rap = frap;
814         ra = *frap;
815         ra->p_dev = dev;
816         ra->p_ino = ino;
817         ra->p_set = 0;
818         ra->p_hindex = hash;
819 found:
820         if (rap != &rab->pb_head) {
821                 *rap = ra->p_next;
822                 ra->p_next   = rab->pb_head;
823                 rab->pb_head = ra;
824         }
825         ra->p_count++;
826         nfsdstats.ra_depth[depth*10/nfsdstats.ra_size]++;
827         spin_unlock(&rab->pb_lock);
828 
829         if (ra->p_set)
830                 file->f_ra = ra->p_ra;
831         return ra;
832 }
833 
834 void nfsd_put_raparams(struct file *file, struct raparms *ra)
835 {
836         struct raparm_hbucket *rab = &raparm_hash[ra->p_hindex];
837 
838         spin_lock(&rab->pb_lock);
839         ra->p_ra = file->f_ra;
840         ra->p_set = 1;
841         ra->p_count--;
842         spin_unlock(&rab->pb_lock);
843 }
844 
845 /*
846  * Grab and keep cached pages associated with a file in the svc_rqst
847  * so that they can be passed to the network sendmsg/sendpage routines
848  * directly. They will be released after the sending has completed.
849  */
850 static int
851 nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
852                   struct splice_desc *sd)
853 {
854         struct svc_rqst *rqstp = sd->u.data;
855         struct page **pp = rqstp->rq_next_page;
856         struct page *page = buf->page;
857         size_t size;
858 
859         size = sd->len;
860 
861         if (rqstp->rq_res.page_len == 0) {
862                 get_page(page);
863                 put_page(*rqstp->rq_next_page);
864                 *(rqstp->rq_next_page++) = page;
865                 rqstp->rq_res.page_base = buf->offset;
866                 rqstp->rq_res.page_len = size;
867         } else if (page != pp[-1]) {
868                 get_page(page);
869                 if (*rqstp->rq_next_page)
870                         put_page(*rqstp->rq_next_page);
871                 *(rqstp->rq_next_page++) = page;
872                 rqstp->rq_res.page_len += size;
873         } else
874                 rqstp->rq_res.page_len += size;
875 
876         return size;
877 }
878 
879 static int nfsd_direct_splice_actor(struct pipe_inode_info *pipe,
880                                     struct splice_desc *sd)
881 {
882         return __splice_from_pipe(pipe, sd, nfsd_splice_actor);
883 }
884 
885 static __be32 nfsd_finish_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
886                                struct file *file, loff_t offset,
887                                unsigned long *count, int host_err)
888 {
889         if (host_err >= 0) {
890                 nfsdstats.io_read += host_err;
891                 *count = host_err;
892                 fsnotify_access(file);
893                 trace_nfsd_read_io_done(rqstp, fhp, offset, *count);
894                 return 0;
895         } else {
896                 trace_nfsd_read_err(rqstp, fhp, offset, host_err);
897                 return nfserrno(host_err);
898         }
899 }
900 
901 __be32 nfsd_splice_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
902                         struct file *file, loff_t offset, unsigned long *count)
903 {
904         struct splice_desc sd = {
905                 .len            = 0,
906                 .total_len      = *count,
907                 .pos            = offset,
908                 .u.data         = rqstp,
909         };
910         int host_err;
911 
912         trace_nfsd_read_splice(rqstp, fhp, offset, *count);
913         rqstp->rq_next_page = rqstp->rq_respages + 1;
914         host_err = splice_direct_to_actor(file, &sd, nfsd_direct_splice_actor);
915         return nfsd_finish_read(rqstp, fhp, file, offset, count, host_err);
916 }
917 
918 __be32 nfsd_readv(struct svc_rqst *rqstp, struct svc_fh *fhp,
919                   struct file *file, loff_t offset,
920                   struct kvec *vec, int vlen, unsigned long *count)
921 {
922         struct iov_iter iter;
923         int host_err;
924 
925         trace_nfsd_read_vector(rqstp, fhp, offset, *count);
926         iov_iter_kvec(&iter, READ | ITER_KVEC, vec, vlen, *count);
927         host_err = vfs_iter_read(file, &iter, &offset, 0);
928         return nfsd_finish_read(rqstp, fhp, file, offset, count, host_err);
929 }
930 
931 /*
932  * Gathered writes: If another process is currently writing to the file,
933  * there's a high chance this is another nfsd (triggered by a bulk write
934  * from a client's biod). Rather than syncing the file with each write
935  * request, we sleep for 10 msec.
936  *
937  * I don't know if this roughly approximates C. Juszak's idea of
938  * gathered writes, but it's a nice and simple solution (IMHO), and it
939  * seems to work:-)
940  *
941  * Note: we do this only in the NFSv2 case, since v3 and higher have a
942  * better tool (separate unstable writes and commits) for solving this
943  * problem.
944  */
945 static int wait_for_concurrent_writes(struct file *file)
946 {
947         struct inode *inode = file_inode(file);
948         static ino_t last_ino;
949         static dev_t last_dev;
950         int err = 0;
951 
952         if (atomic_read(&inode->i_writecount) > 1
953             || (last_ino == inode->i_ino && last_dev == inode->i_sb->s_dev)) {
954                 dprintk("nfsd: write defer %d\n", task_pid_nr(current));
955                 msleep(10);
956                 dprintk("nfsd: write resume %d\n", task_pid_nr(current));
957         }
958 
959         if (inode->i_state & I_DIRTY) {
960                 dprintk("nfsd: write sync %d\n", task_pid_nr(current));
961                 err = vfs_fsync(file, 0);
962         }
963         last_ino = inode->i_ino;
964         last_dev = inode->i_sb->s_dev;
965         return err;
966 }
967 
968 __be32
969 nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
970                                 loff_t offset, struct kvec *vec, int vlen,
971                                 unsigned long *cnt, int stable)
972 {
973         struct svc_export       *exp;
974         struct iov_iter         iter;
975         __be32                  nfserr;
976         int                     host_err;
977         int                     use_wgather;
978         loff_t                  pos = offset;
979         unsigned int            pflags = current->flags;
980         rwf_t                   flags = 0;
981 
982         trace_nfsd_write_opened(rqstp, fhp, offset, *cnt);
983 
984         if (test_bit(RQ_LOCAL, &rqstp->rq_flags))
985                 /*
986                  * We want less throttling in balance_dirty_pages()
987                  * and shrink_inactive_list() so that nfs to
988                  * localhost doesn't cause nfsd to lock up due to all
989                  * the client's dirty pages or its congested queue.
990                  */
991                 current->flags |= PF_LESS_THROTTLE;
992 
993         exp = fhp->fh_export;
994         use_wgather = (rqstp->rq_vers == 2) && EX_WGATHER(exp);
995 
996         if (!EX_ISSYNC(exp))
997                 stable = NFS_UNSTABLE;
998 
999         if (stable && !use_wgather)
1000                 flags |= RWF_SYNC;
1001 
1002         iov_iter_kvec(&iter, WRITE | ITER_KVEC, vec, vlen, *cnt);
1003         host_err = vfs_iter_write(file, &iter, &pos, flags);
1004         if (host_err < 0)
1005                 goto out_nfserr;
1006         nfsdstats.io_write += *cnt;
1007         fsnotify_modify(file);
1008 
1009         if (stable && use_wgather)
1010                 host_err = wait_for_concurrent_writes(file);
1011 
1012 out_nfserr:
1013         if (host_err >= 0) {
1014                 trace_nfsd_write_io_done(rqstp, fhp, offset, *cnt);
1015                 nfserr = nfs_ok;
1016         } else {
1017                 trace_nfsd_write_err(rqstp, fhp, offset, host_err);
1018                 nfserr = nfserrno(host_err);
1019         }
1020         if (test_bit(RQ_LOCAL, &rqstp->rq_flags))
1021                 current_restore_flags(pflags, PF_LESS_THROTTLE);
1022         return nfserr;
1023 }
1024 
1025 /*
1026  * Read data from a file. count must contain the requested read count
1027  * on entry. On return, *count contains the number of bytes actually read.
1028  * N.B. After this call fhp needs an fh_put
1029  */
1030 __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
1031         loff_t offset, struct kvec *vec, int vlen, unsigned long *count)
1032 {
1033         struct file *file;
1034         struct raparms  *ra;
1035         __be32 err;
1036 
1037         trace_nfsd_read_start(rqstp, fhp, offset, *count);
1038         err = nfsd_open(rqstp, fhp, S_IFREG, NFSD_MAY_READ, &file);
1039         if (err)
1040                 return err;
1041 
1042         ra = nfsd_init_raparms(file);
1043 
1044         if (file->f_op->splice_read && test_bit(RQ_SPLICE_OK, &rqstp->rq_flags))
1045                 err = nfsd_splice_read(rqstp, fhp, file, offset, count);
1046         else
1047                 err = nfsd_readv(rqstp, fhp, file, offset, vec, vlen, count);
1048 
1049         if (ra)
1050                 nfsd_put_raparams(file, ra);
1051         fput(file);
1052 
1053         trace_nfsd_read_done(rqstp, fhp, offset, *count);
1054 
1055         return err;
1056 }
1057 
1058 /*
1059  * Write data to a file.
1060  * The stable flag requests synchronous writes.
1061  * N.B. After this call fhp needs an fh_put
1062  */
1063 __be32
1064 nfsd_write(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t offset,
1065            struct kvec *vec, int vlen, unsigned long *cnt, int stable)
1066 {
1067         struct file *file = NULL;
1068         __be32 err = 0;
1069 
1070         trace_nfsd_write_start(rqstp, fhp, offset, *cnt);
1071 
1072         err = nfsd_open(rqstp, fhp, S_IFREG, NFSD_MAY_WRITE, &file);
1073         if (err)
1074                 goto out;
1075 
1076         err = nfsd_vfs_write(rqstp, fhp, file, offset, vec, vlen, cnt, stable);
1077         fput(file);
1078 out:
1079         trace_nfsd_write_done(rqstp, fhp, offset, *cnt);
1080         return err;
1081 }
1082 
1083 #ifdef CONFIG_NFSD_V3
1084 /*
1085  * Commit all pending writes to stable storage.
1086  *
1087  * Note: we only guarantee that data that lies within the range specified
1088  * by the 'offset' and 'count' parameters will be synced.
1089  *
1090  * Unfortunately we cannot lock the file to make sure we return full WCC
1091  * data to the client, as locking happens lower down in the filesystem.
1092  */
1093 __be32
1094 nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp,
1095                loff_t offset, unsigned long count)
1096 {
1097         struct file     *file;
1098         loff_t          end = LLONG_MAX;
1099         __be32          err = nfserr_inval;
1100 
1101         if (offset < 0)
1102                 goto out;
1103         if (count != 0) {
1104                 end = offset + (loff_t)count - 1;
1105                 if (end < offset)
1106                         goto out;
1107         }
1108 
1109         err = nfsd_open(rqstp, fhp, S_IFREG,
1110                         NFSD_MAY_WRITE|NFSD_MAY_NOT_BREAK_LEASE, &file);
1111         if (err)
1112                 goto out;
1113         if (EX_ISSYNC(fhp->fh_export)) {
1114                 int err2 = vfs_fsync_range(file, offset, end, 0);
1115 
1116                 if (err2 != -EINVAL)
1117                         err = nfserrno(err2);
1118                 else
1119                         err = nfserr_notsupp;
1120         }
1121 
1122         fput(file);
1123 out:
1124         return err;
1125 }
1126 #endif /* CONFIG_NFSD_V3 */
1127 
1128 static __be32
1129 nfsd_create_setattr(struct svc_rqst *rqstp, struct svc_fh *resfhp,
1130                         struct iattr *iap)
1131 {
1132         /*
1133          * Mode has already been set earlier in create:
1134          */
1135         iap->ia_valid &= ~ATTR_MODE;
1136         /*
1137          * Setting uid/gid works only for root.  Irix appears to
1138          * send along the gid on create when it tries to implement
1139          * setgid directories via NFS:
1140          */
1141         if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID))
1142                 iap->ia_valid &= ~(ATTR_UID|ATTR_GID);
1143         if (iap->ia_valid)
1144                 return nfsd_setattr(rqstp, resfhp, iap, 0, (time_t)0);
1145         /* Callers expect file metadata to be committed here */
1146         return nfserrno(commit_metadata(resfhp));
1147 }
1148 
1149 /* HPUX client sometimes creates a file in mode 000, and sets size to 0.
1150  * setting size to 0 may fail for some specific file systems by the permission
1151  * checking which requires WRITE permission but the mode is 000.
1152  * we ignore the resizing(to 0) on the just new created file, since the size is
1153  * 0 after file created.
1154  *
1155  * call this only after vfs_create() is called.
1156  * */
1157 static void
1158 nfsd_check_ignore_resizing(struct iattr *iap)
1159 {
1160         if ((iap->ia_valid & ATTR_SIZE) && (iap->ia_size == 0))
1161                 iap->ia_valid &= ~ATTR_SIZE;
1162 }
1163 
1164 /* The parent directory should already be locked: */
1165 __be32
1166 nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
1167                 char *fname, int flen, struct iattr *iap,
1168                 int type, dev_t rdev, struct svc_fh *resfhp)
1169 {
1170         struct dentry   *dentry, *dchild;
1171         struct inode    *dirp;
1172         __be32          err;
1173         __be32          err2;
1174         int             host_err;
1175 
1176         dentry = fhp->fh_dentry;
1177         dirp = d_inode(dentry);
1178 
1179         dchild = dget(resfhp->fh_dentry);
1180         if (!fhp->fh_locked) {
1181                 WARN_ONCE(1, "nfsd_create: parent %pd2 not locked!\n",
1182                                 dentry);
1183                 err = nfserr_io;
1184                 goto out;
1185         }
1186 
1187         err = nfsd_permission(rqstp, fhp->fh_export, dentry, NFSD_MAY_CREATE);
1188         if (err)
1189                 goto out;
1190 
1191         if (!(iap->ia_valid & ATTR_MODE))
1192                 iap->ia_mode = 0;
1193         iap->ia_mode = (iap->ia_mode & S_IALLUGO) | type;
1194 
1195         err = 0;
1196         host_err = 0;
1197         switch (type) {
1198         case S_IFREG:
1199                 host_err = vfs_create(dirp, dchild, iap->ia_mode, true);
1200                 if (!host_err)
1201                         nfsd_check_ignore_resizing(iap);
1202                 break;
1203         case S_IFDIR:
1204                 host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
1205                 if (!host_err && unlikely(d_unhashed(dchild))) {
1206                         struct dentry *d;
1207                         d = lookup_one_len(dchild->d_name.name,
1208                                            dchild->d_parent,
1209                                            dchild->d_name.len);
1210                         if (IS_ERR(d)) {
1211                                 host_err = PTR_ERR(d);
1212                                 break;
1213                         }
1214                         if (unlikely(d_is_negative(d))) {
1215                                 dput(d);
1216                                 err = nfserr_serverfault;
1217                                 goto out;
1218                         }
1219                         dput(resfhp->fh_dentry);
1220                         resfhp->fh_dentry = dget(d);
1221                         err = fh_update(resfhp);
1222                         dput(dchild);
1223                         dchild = d;
1224                         if (err)
1225                                 goto out;
1226                 }
1227                 break;
1228         case S_IFCHR:
1229         case S_IFBLK:
1230         case S_IFIFO:
1231         case S_IFSOCK:
1232                 host_err = vfs_mknod(dirp, dchild, iap->ia_mode, rdev);
1233                 break;
1234         default:
1235                 printk(KERN_WARNING "nfsd: bad file type %o in nfsd_create\n",
1236                        type);
1237                 host_err = -EINVAL;
1238         }
1239         if (host_err < 0)
1240                 goto out_nfserr;
1241 
1242         err = nfsd_create_setattr(rqstp, resfhp, iap);
1243 
1244         /*
1245          * nfsd_create_setattr already committed the child.  Transactional
1246          * filesystems had a chance to commit changes for both parent and
1247          * child simultaneously making the following commit_metadata a
1248          * noop.
1249          */
1250         err2 = nfserrno(commit_metadata(fhp));
1251         if (err2)
1252                 err = err2;
1253         /*
1254          * Update the file handle to get the new inode info.
1255          */
1256         if (!err)
1257                 err = fh_update(resfhp);
1258 out:
1259         dput(dchild);
1260         return err;
1261 
1262 out_nfserr:
1263         err = nfserrno(host_err);
1264         goto out;
1265 }
1266 
1267 /*
1268  * Create a filesystem object (regular, directory, special).
1269  * Note that the parent directory is left locked.
1270  *
1271  * N.B. Every call to nfsd_create needs an fh_put for _both_ fhp and resfhp
1272  */
1273 __be32
1274 nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
1275                 char *fname, int flen, struct iattr *iap,
1276                 int type, dev_t rdev, struct svc_fh *resfhp)
1277 {
1278         struct dentry   *dentry, *dchild = NULL;
1279         struct inode    *dirp;
1280         __be32          err;
1281         int             host_err;
1282 
1283         if (isdotent(fname, flen))
1284                 return nfserr_exist;
1285 
1286         err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_NOP);
1287         if (err)
1288                 return err;
1289 
1290         dentry = fhp->fh_dentry;
1291         dirp = d_inode(dentry);
1292 
1293         host_err = fh_want_write(fhp);
1294         if (host_err)
1295                 return nfserrno(host_err);
1296 
1297         fh_lock_nested(fhp, I_MUTEX_PARENT);
1298         dchild = lookup_one_len(fname, dentry, flen);
1299         host_err = PTR_ERR(dchild);
1300         if (IS_ERR(dchild))
1301                 return nfserrno(host_err);
1302         err = fh_compose(resfhp, fhp->fh_export, dchild, fhp);
1303         /*
1304          * We unconditionally drop our ref to dchild as fh_compose will have
1305          * already grabbed its own ref for it.
1306          */
1307         dput(dchild);
1308         if (err)
1309                 return err;
1310         return nfsd_create_locked(rqstp, fhp, fname, flen, iap, type,
1311                                         rdev, resfhp);
1312 }
1313 
1314 #ifdef CONFIG_NFSD_V3
1315 
1316 /*
1317  * NFSv3 and NFSv4 version of nfsd_create
1318  */
1319 __be32
1320 do_nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
1321                 char *fname, int flen, struct iattr *iap,
1322                 struct svc_fh *resfhp, int createmode, u32 *verifier,
1323                 bool *truncp, bool *created)
1324 {
1325         struct dentry   *dentry, *dchild = NULL;
1326         struct inode    *dirp;
1327         __be32          err;
1328         int             host_err;
1329         __u32           v_mtime=0, v_atime=0;
1330 
1331         err = nfserr_perm;
1332         if (!flen)
1333                 goto out;
1334         err = nfserr_exist;
1335         if (isdotent(fname, flen))
1336                 goto out;
1337         if (!(iap->ia_valid & ATTR_MODE))
1338                 iap->ia_mode = 0;
1339         err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_EXEC);
1340         if (err)
1341                 goto out;
1342 
1343         dentry = fhp->fh_dentry;
1344         dirp = d_inode(dentry);
1345 
1346         host_err = fh_want_write(fhp);
1347         if (host_err)
1348                 goto out_nfserr;
1349 
1350         fh_lock_nested(fhp, I_MUTEX_PARENT);
1351 
1352         /*
1353          * Compose the response file handle.
1354          */
1355         dchild = lookup_one_len(fname, dentry, flen);
1356         host_err = PTR_ERR(dchild);
1357         if (IS_ERR(dchild))
1358                 goto out_nfserr;
1359 
1360         /* If file doesn't exist, check for permissions to create one */
1361         if (d_really_is_negative(dchild)) {
1362                 err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
1363                 if (err)
1364                         goto out;
1365         }
1366 
1367         err = fh_compose(resfhp, fhp->fh_export, dchild, fhp);
1368         if (err)
1369                 goto out;
1370 
1371         if (nfsd_create_is_exclusive(createmode)) {
1372                 /* solaris7 gets confused (bugid 4218508) if these have
1373                  * the high bit set, so just clear the high bits. If this is
1374                  * ever changed to use different attrs for storing the
1375                  * verifier, then do_open_lookup() will also need to be fixed
1376                  * accordingly.
1377                  */
1378                 v_mtime = verifier[0]&0x7fffffff;
1379                 v_atime = verifier[1]&0x7fffffff;
1380         }
1381         
1382         if (d_really_is_positive(dchild)) {
1383                 err = 0;
1384 
1385                 switch (createmode) {
1386                 case NFS3_CREATE_UNCHECKED:
1387                         if (! d_is_reg(dchild))
1388                                 goto out;
1389                         else if (truncp) {
1390                                 /* in nfsv4, we need to treat this case a little
1391                                  * differently.  we don't want to truncate the
1392                                  * file now; this would be wrong if the OPEN
1393                                  * fails for some other reason.  furthermore,
1394                                  * if the size is nonzero, we should ignore it
1395                                  * according to spec!
1396                                  */
1397                                 *truncp = (iap->ia_valid & ATTR_SIZE) && !iap->ia_size;
1398                         }
1399                         else {
1400                                 iap->ia_valid &= ATTR_SIZE;
1401                                 goto set_attr;
1402                         }
1403                         break;
1404                 case NFS3_CREATE_EXCLUSIVE:
1405                         if (   d_inode(dchild)->i_mtime.tv_sec == v_mtime
1406                             && d_inode(dchild)->i_atime.tv_sec == v_atime
1407                             && d_inode(dchild)->i_size  == 0 ) {
1408                                 if (created)
1409                                         *created = 1;
1410                                 break;
1411                         }
1412                 case NFS4_CREATE_EXCLUSIVE4_1:
1413                         if (   d_inode(dchild)->i_mtime.tv_sec == v_mtime
1414                             && d_inode(dchild)->i_atime.tv_sec == v_atime
1415                             && d_inode(dchild)->i_size  == 0 ) {
1416                                 if (created)
1417                                         *created = 1;
1418                                 goto set_attr;
1419                         }
1420                          /* fallthru */
1421                 case NFS3_CREATE_GUARDED:
1422                         err = nfserr_exist;
1423                 }
1424                 fh_drop_write(fhp);
1425                 goto out;
1426         }
1427 
1428         host_err = vfs_create(dirp, dchild, iap->ia_mode, true);
1429         if (host_err < 0) {
1430                 fh_drop_write(fhp);
1431                 goto out_nfserr;
1432         }
1433         if (created)
1434                 *created = 1;
1435 
1436         nfsd_check_ignore_resizing(iap);
1437 
1438         if (nfsd_create_is_exclusive(createmode)) {
1439                 /* Cram the verifier into atime/mtime */
1440                 iap->ia_valid = ATTR_MTIME|ATTR_ATIME
1441                         | ATTR_MTIME_SET|ATTR_ATIME_SET;
1442                 /* XXX someone who knows this better please fix it for nsec */ 
1443                 iap->ia_mtime.tv_sec = v_mtime;
1444                 iap->ia_atime.tv_sec = v_atime;
1445                 iap->ia_mtime.tv_nsec = 0;
1446                 iap->ia_atime.tv_nsec = 0;
1447         }
1448 
1449  set_attr:
1450         err = nfsd_create_setattr(rqstp, resfhp, iap);
1451 
1452         /*
1453          * nfsd_create_setattr already committed the child
1454          * (and possibly also the parent).
1455          */
1456         if (!err)
1457                 err = nfserrno(commit_metadata(fhp));
1458 
1459         /*
1460          * Update the filehandle to get the new inode info.
1461          */
1462         if (!err)
1463                 err = fh_update(resfhp);
1464 
1465  out:
1466         fh_unlock(fhp);
1467         if (dchild && !IS_ERR(dchild))
1468                 dput(dchild);
1469         fh_drop_write(fhp);
1470         return err;
1471  
1472  out_nfserr:
1473         err = nfserrno(host_err);
1474         goto out;
1475 }
1476 #endif /* CONFIG_NFSD_V3 */
1477 
1478 /*
1479  * Read a symlink. On entry, *lenp must contain the maximum path length that
1480  * fits into the buffer. On return, it contains the true length.
1481  * N.B. After this call fhp needs an fh_put
1482  */
1483 __be32
1484 nfsd_readlink(struct svc_rqst *rqstp, struct svc_fh *fhp, char *buf, int *lenp)
1485 {
1486         __be32          err;
1487         const char *link;
1488         struct path path;
1489         DEFINE_DELAYED_CALL(done);
1490         int len;
1491 
1492         err = fh_verify(rqstp, fhp, S_IFLNK, NFSD_MAY_NOP);
1493         if (unlikely(err))
1494                 return err;
1495 
1496         path.mnt = fhp->fh_export->ex_path.mnt;
1497         path.dentry = fhp->fh_dentry;
1498 
1499         if (unlikely(!d_is_symlink(path.dentry)))
1500                 return nfserr_inval;
1501 
1502         touch_atime(&path);
1503 
1504         link = vfs_get_link(path.dentry, &done);
1505         if (IS_ERR(link))
1506                 return nfserrno(PTR_ERR(link));
1507 
1508         len = strlen(link);
1509         if (len < *lenp)
1510                 *lenp = len;
1511         memcpy(buf, link, *lenp);
1512         do_delayed_call(&done);
1513         return 0;
1514 }
1515 
1516 /*
1517  * Create a symlink and look up its inode
1518  * N.B. After this call _both_ fhp and resfhp need an fh_put
1519  */
1520 __be32
1521 nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
1522                                 char *fname, int flen,
1523                                 char *path,
1524                                 struct svc_fh *resfhp)
1525 {
1526         struct dentry   *dentry, *dnew;
1527         __be32          err, cerr;
1528         int             host_err;
1529 
1530         err = nfserr_noent;
1531         if (!flen || path[0] == '\0')
1532                 goto out;
1533         err = nfserr_exist;
1534         if (isdotent(fname, flen))
1535                 goto out;
1536 
1537         err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_CREATE);
1538         if (err)
1539                 goto out;
1540 
1541         host_err = fh_want_write(fhp);
1542         if (host_err)
1543                 goto out_nfserr;
1544 
1545         fh_lock(fhp);
1546         dentry = fhp->fh_dentry;
1547         dnew = lookup_one_len(fname, dentry, flen);
1548         host_err = PTR_ERR(dnew);
1549         if (IS_ERR(dnew))
1550                 goto out_nfserr;
1551 
1552         host_err = vfs_symlink(d_inode(dentry), dnew, path);
1553         err = nfserrno(host_err);
1554         if (!err)
1555                 err = nfserrno(commit_metadata(fhp));
1556         fh_unlock(fhp);
1557 
1558         fh_drop_write(fhp);
1559 
1560         cerr = fh_compose(resfhp, fhp->fh_export, dnew, fhp);
1561         dput(dnew);
1562         if (err==0) err = cerr;
1563 out:
1564         return err;
1565 
1566 out_nfserr:
1567         err = nfserrno(host_err);
1568         goto out;
1569 }
1570 
1571 /*
1572  * Create a hardlink
1573  * N.B. After this call _both_ ffhp and tfhp need an fh_put
1574  */
1575 __be32
1576 nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
1577                                 char *name, int len, struct svc_fh *tfhp)
1578 {
1579         struct dentry   *ddir, *dnew, *dold;
1580         struct inode    *dirp;
1581         __be32          err;
1582         int             host_err;
1583 
1584         err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_CREATE);
1585         if (err)
1586                 goto out;
1587         err = fh_verify(rqstp, tfhp, 0, NFSD_MAY_NOP);
1588         if (err)
1589                 goto out;
1590         err = nfserr_isdir;
1591         if (d_is_dir(tfhp->fh_dentry))
1592                 goto out;
1593         err = nfserr_perm;
1594         if (!len)
1595                 goto out;
1596         err = nfserr_exist;
1597         if (isdotent(name, len))
1598                 goto out;
1599 
1600         host_err = fh_want_write(tfhp);
1601         if (host_err) {
1602                 err = nfserrno(host_err);
1603                 goto out;
1604         }
1605 
1606         fh_lock_nested(ffhp, I_MUTEX_PARENT);
1607         ddir = ffhp->fh_dentry;
1608         dirp = d_inode(ddir);
1609 
1610         dnew = lookup_one_len(name, ddir, len);
1611         host_err = PTR_ERR(dnew);
1612         if (IS_ERR(dnew))
1613                 goto out_nfserr;
1614 
1615         dold = tfhp->fh_dentry;
1616 
1617         err = nfserr_noent;
1618         if (d_really_is_negative(dold))
1619                 goto out_dput;
1620         host_err = vfs_link(dold, dirp, dnew, NULL);
1621         if (!host_err) {
1622                 err = nfserrno(commit_metadata(ffhp));
1623                 if (!err)
1624                         err = nfserrno(commit_metadata(tfhp));
1625         } else {
1626                 if (host_err == -EXDEV && rqstp->rq_vers == 2)
1627                         err = nfserr_acces;
1628                 else
1629                         err = nfserrno(host_err);
1630         }
1631 out_dput:
1632         dput(dnew);
1633 out_unlock:
1634         fh_unlock(ffhp);
1635         fh_drop_write(tfhp);
1636 out:
1637         return err;
1638 
1639 out_nfserr:
1640         err = nfserrno(host_err);
1641         goto out_unlock;
1642 }
1643 
1644 /*
1645  * Rename a file
1646  * N.B. After this call _both_ ffhp and tfhp need an fh_put
1647  */
1648 __be32
1649 nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
1650                             struct svc_fh *tfhp, char *tname, int tlen)
1651 {
1652         struct dentry   *fdentry, *tdentry, *odentry, *ndentry, *trap;
1653         struct inode    *fdir, *tdir;
1654         __be32          err;
1655         int             host_err;
1656 
1657         err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_REMOVE);
1658         if (err)
1659                 goto out;
1660         err = fh_verify(rqstp, tfhp, S_IFDIR, NFSD_MAY_CREATE);
1661         if (err)
1662                 goto out;
1663 
1664         fdentry = ffhp->fh_dentry;
1665         fdir = d_inode(fdentry);
1666 
1667         tdentry = tfhp->fh_dentry;
1668         tdir = d_inode(tdentry);
1669 
1670         err = nfserr_perm;
1671         if (!flen || isdotent(fname, flen) || !tlen || isdotent(tname, tlen))
1672                 goto out;
1673 
1674         host_err = fh_want_write(ffhp);
1675         if (host_err) {
1676                 err = nfserrno(host_err);
1677                 goto out;
1678         }
1679 
1680         /* cannot use fh_lock as we need deadlock protective ordering
1681          * so do it by hand */
1682         trap = lock_rename(tdentry, fdentry);
1683         ffhp->fh_locked = tfhp->fh_locked = true;
1684         fill_pre_wcc(ffhp);
1685         fill_pre_wcc(tfhp);
1686 
1687         odentry = lookup_one_len(fname, fdentry, flen);
1688         host_err = PTR_ERR(odentry);
1689         if (IS_ERR(odentry))
1690                 goto out_nfserr;
1691 
1692         host_err = -ENOENT;
1693         if (d_really_is_negative(odentry))
1694                 goto out_dput_old;
1695         host_err = -EINVAL;
1696         if (odentry == trap)
1697                 goto out_dput_old;
1698 
1699         ndentry = lookup_one_len(tname, tdentry, tlen);
1700         host_err = PTR_ERR(ndentry);
1701         if (IS_ERR(ndentry))
1702                 goto out_dput_old;
1703         host_err = -ENOTEMPTY;
1704         if (ndentry == trap)
1705                 goto out_dput_new;
1706 
1707         host_err = -EXDEV;
1708         if (ffhp->fh_export->ex_path.mnt != tfhp->fh_export->ex_path.mnt)
1709                 goto out_dput_new;
1710         if (ffhp->fh_export->ex_path.dentry != tfhp->fh_export->ex_path.dentry)
1711                 goto out_dput_new;
1712 
1713         host_err = vfs_rename(fdir, odentry, tdir, ndentry, NULL, 0);
1714         if (!host_err) {
1715                 host_err = commit_metadata(tfhp);
1716                 if (!host_err)
1717                         host_err = commit_metadata(ffhp);
1718         }
1719  out_dput_new:
1720         dput(ndentry);
1721  out_dput_old:
1722         dput(odentry);
1723  out_nfserr:
1724         err = nfserrno(host_err);
1725         /*
1726          * We cannot rely on fh_unlock on the two filehandles,
1727          * as that would do the wrong thing if the two directories
1728          * were the same, so again we do it by hand.
1729          */
1730         fill_post_wcc(ffhp);
1731         fill_post_wcc(tfhp);
1732         unlock_rename(tdentry, fdentry);
1733         ffhp->fh_locked = tfhp->fh_locked = false;
1734         fh_drop_write(ffhp);
1735 
1736 out:
1737         return err;
1738 }
1739 
1740 /*
1741  * Unlink a file or directory
1742  * N.B. After this call fhp needs an fh_put
1743  */
1744 __be32
1745 nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
1746                                 char *fname, int flen)
1747 {
1748         struct dentry   *dentry, *rdentry;
1749         struct inode    *dirp;
1750         __be32          err;
1751         int             host_err;
1752 
1753         err = nfserr_acces;
1754         if (!flen || isdotent(fname, flen))
1755                 goto out;
1756         err = fh_verify(rqstp, fhp, S_IFDIR, NFSD_MAY_REMOVE);
1757         if (err)
1758                 goto out;
1759 
1760         host_err = fh_want_write(fhp);
1761         if (host_err)
1762                 goto out_nfserr;
1763 
1764         fh_lock_nested(fhp, I_MUTEX_PARENT);
1765         dentry = fhp->fh_dentry;
1766         dirp = d_inode(dentry);
1767 
1768         rdentry = lookup_one_len(fname, dentry, flen);
1769         host_err = PTR_ERR(rdentry);
1770         if (IS_ERR(rdentry))
1771                 goto out_nfserr;
1772 
1773         if (d_really_is_negative(rdentry)) {
1774                 dput(rdentry);
1775                 err = nfserr_noent;
1776                 goto out;
1777         }
1778 
1779         if (!type)
1780                 type = d_inode(rdentry)->i_mode & S_IFMT;
1781 
1782         if (type != S_IFDIR)
1783                 host_err = vfs_unlink(dirp, rdentry, NULL);
1784         else
1785                 host_err = vfs_rmdir(dirp, rdentry);
1786         if (!host_err)
1787                 host_err = commit_metadata(fhp);
1788         dput(rdentry);
1789 
1790 out_nfserr:
1791         err = nfserrno(host_err);
1792 out:
1793         return err;
1794 }
1795 
1796 /*
1797  * We do this buffering because we must not call back into the file
1798  * system's ->lookup() method from the filldir callback. That may well
1799  * deadlock a number of file systems.
1800  *
1801  * This is based heavily on the implementation of same in XFS.
1802  */
1803 struct buffered_dirent {
1804         u64             ino;
1805         loff_t          offset;
1806         int             namlen;
1807         unsigned int    d_type;
1808         char            name[];
1809 };
1810 
1811 struct readdir_data {
1812         struct dir_context ctx;
1813         char            *dirent;
1814         size_t          used;
1815         int             full;
1816 };
1817 
1818 static int nfsd_buffered_filldir(struct dir_context *ctx, const char *name,
1819                                  int namlen, loff_t offset, u64 ino,
1820                                  unsigned int d_type)
1821 {
1822         struct readdir_data *buf =
1823                 container_of(ctx, struct readdir_data, ctx);
1824         struct buffered_dirent *de = (void *)(buf->dirent + buf->used);
1825         unsigned int reclen;
1826 
1827         reclen = ALIGN(sizeof(struct buffered_dirent) + namlen, sizeof(u64));
1828         if (buf->used + reclen > PAGE_SIZE) {
1829                 buf->full = 1;
1830                 return -EINVAL;
1831         }
1832 
1833         de->namlen = namlen;
1834         de->offset = offset;
1835         de->ino = ino;
1836         de->d_type = d_type;
1837         memcpy(de->name, name, namlen);
1838         buf->used += reclen;
1839 
1840         return 0;
1841 }
1842 
1843 static __be32 nfsd_buffered_readdir(struct file *file, nfsd_filldir_t func,
1844                                     struct readdir_cd *cdp, loff_t *offsetp)
1845 {
1846         struct buffered_dirent *de;
1847         int host_err;
1848         int size;
1849         loff_t offset;
1850         struct readdir_data buf = {
1851                 .ctx.actor = nfsd_buffered_filldir,
1852                 .dirent = (void *)__get_free_page(GFP_KERNEL)
1853         };
1854 
1855         if (!buf.dirent)
1856                 return nfserrno(-ENOMEM);
1857 
1858         offset = *offsetp;
1859 
1860         while (1) {
1861                 unsigned int reclen;
1862 
1863                 cdp->err = nfserr_eof; /* will be cleared on successful read */
1864                 buf.used = 0;
1865                 buf.full = 0;
1866 
1867                 host_err = iterate_dir(file, &buf.ctx);
1868                 if (buf.full)
1869                         host_err = 0;
1870 
1871                 if (host_err < 0)
1872                         break;
1873 
1874                 size = buf.used;
1875 
1876                 if (!size)
1877                         break;
1878 
1879                 de = (struct buffered_dirent *)buf.dirent;
1880                 while (size > 0) {
1881                         offset = de->offset;
1882 
1883                         if (func(cdp, de->name, de->namlen, de->offset,
1884                                  de->ino, de->d_type))
1885                                 break;
1886 
1887                         if (cdp->err != nfs_ok)
1888                                 break;
1889 
1890                         reclen = ALIGN(sizeof(*de) + de->namlen,
1891                                        sizeof(u64));
1892                         size -= reclen;
1893                         de = (struct buffered_dirent *)((char *)de + reclen);
1894                 }
1895                 if (size > 0) /* We bailed out early */
1896                         break;
1897 
1898                 offset = vfs_llseek(file, 0, SEEK_CUR);
1899         }
1900 
1901         free_page((unsigned long)(buf.dirent));
1902 
1903         if (host_err)
1904                 return nfserrno(host_err);
1905 
1906         *offsetp = offset;
1907         return cdp->err;
1908 }
1909 
1910 /*
1911  * Read entries from a directory.
1912  * The  NFSv3/4 verifier we ignore for now.
1913  */
1914 __be32
1915 nfsd_readdir(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t *offsetp, 
1916              struct readdir_cd *cdp, nfsd_filldir_t func)
1917 {
1918         __be32          err;
1919         struct file     *file;
1920         loff_t          offset = *offsetp;
1921         int             may_flags = NFSD_MAY_READ;
1922 
1923         /* NFSv2 only supports 32 bit cookies */
1924         if (rqstp->rq_vers > 2)
1925                 may_flags |= NFSD_MAY_64BIT_COOKIE;
1926 
1927         err = nfsd_open(rqstp, fhp, S_IFDIR, may_flags, &file);
1928         if (err)
1929                 goto out;
1930 
1931         offset = vfs_llseek(file, offset, SEEK_SET);
1932         if (offset < 0) {
1933                 err = nfserrno((int)offset);
1934                 goto out_close;
1935         }
1936 
1937         err = nfsd_buffered_readdir(file, func, cdp, offsetp);
1938 
1939         if (err == nfserr_eof || err == nfserr_toosmall)
1940                 err = nfs_ok; /* can still be found in ->err */
1941 out_close:
1942         fput(file);
1943 out:
1944         return err;
1945 }
1946 
1947 /*
1948  * Get file system stats
1949  * N.B. After this call fhp needs an fh_put
1950  */
1951 __be32
1952 nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat, int access)
1953 {
1954         __be32 err;
1955 
1956         err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP | access);
1957         if (!err) {
1958                 struct path path = {
1959                         .mnt    = fhp->fh_export->ex_path.mnt,
1960                         .dentry = fhp->fh_dentry,
1961                 };
1962                 if (vfs_statfs(&path, stat))
1963                         err = nfserr_io;
1964         }
1965         return err;
1966 }
1967 
1968 static int exp_rdonly(struct svc_rqst *rqstp, struct svc_export *exp)
1969 {
1970         return nfsexp_flags(rqstp, exp) & NFSEXP_READONLY;
1971 }
1972 
1973 /*
1974  * Check for a user's access permissions to this inode.
1975  */
1976 __be32
1977 nfsd_permission(struct svc_rqst *rqstp, struct svc_export *exp,
1978                                         struct dentry *dentry, int acc)
1979 {
1980         struct inode    *inode = d_inode(dentry);
1981         int             err;
1982 
1983         if ((acc & NFSD_MAY_MASK) == NFSD_MAY_NOP)
1984                 return 0;
1985 #if 0
1986         dprintk("nfsd: permission 0x%x%s%s%s%s%s%s%s mode 0%o%s%s%s\n",
1987                 acc,
1988                 (acc & NFSD_MAY_READ)?  " read"  : "",
1989                 (acc & NFSD_MAY_WRITE)? " write" : "",
1990                 (acc & NFSD_MAY_EXEC)?  " exec"  : "",
1991                 (acc & NFSD_MAY_SATTR)? " sattr" : "",
1992                 (acc & NFSD_MAY_TRUNC)? " trunc" : "",
1993                 (acc & NFSD_MAY_LOCK)?  " lock"  : "",
1994                 (acc & NFSD_MAY_OWNER_OVERRIDE)? " owneroverride" : "",
1995                 inode->i_mode,
1996                 IS_IMMUTABLE(inode)?    " immut" : "",
1997                 IS_APPEND(inode)?       " append" : "",
1998                 __mnt_is_readonly(exp->ex_path.mnt)?    " ro" : "");
1999         dprintk("      owner %d/%d user %d/%d\n",
2000                 inode->i_uid, inode->i_gid, current_fsuid(), current_fsgid());
2001 #endif
2002 
2003         /* Normally we reject any write/sattr etc access on a read-only file
2004          * system.  But if it is IRIX doing check on write-access for a 
2005          * device special file, we ignore rofs.
2006          */
2007         if (!(acc & NFSD_MAY_LOCAL_ACCESS))
2008                 if (acc & (NFSD_MAY_WRITE | NFSD_MAY_SATTR | NFSD_MAY_TRUNC)) {
2009                         if (exp_rdonly(rqstp, exp) ||
2010                             __mnt_is_readonly(exp->ex_path.mnt))
2011                                 return nfserr_rofs;
2012                         if (/* (acc & NFSD_MAY_WRITE) && */ IS_IMMUTABLE(inode))
2013                                 return nfserr_perm;
2014                 }
2015         if ((acc & NFSD_MAY_TRUNC) && IS_APPEND(inode))
2016                 return nfserr_perm;
2017 
2018         if (acc & NFSD_MAY_LOCK) {
2019                 /* If we cannot rely on authentication in NLM requests,
2020                  * just allow locks, otherwise require read permission, or
2021                  * ownership
2022                  */
2023                 if (exp->ex_flags & NFSEXP_NOAUTHNLM)
2024                         return 0;
2025                 else
2026                         acc = NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE;
2027         }
2028         /*
2029          * The file owner always gets access permission for accesses that
2030          * would normally be checked at open time. This is to make
2031          * file access work even when the client has done a fchmod(fd, 0).
2032          *
2033          * However, `cp foo bar' should fail nevertheless when bar is
2034          * readonly. A sensible way to do this might be to reject all
2035          * attempts to truncate a read-only file, because a creat() call
2036          * always implies file truncation.
2037          * ... but this isn't really fair.  A process may reasonably call
2038          * ftruncate on an open file descriptor on a file with perm 000.
2039          * We must trust the client to do permission checking - using "ACCESS"
2040          * with NFSv3.
2041          */
2042         if ((acc & NFSD_MAY_OWNER_OVERRIDE) &&
2043             uid_eq(inode->i_uid, current_fsuid()))
2044                 return 0;
2045 
2046         /* This assumes  NFSD_MAY_{READ,WRITE,EXEC} == MAY_{READ,WRITE,EXEC} */
2047         err = inode_permission(inode, acc & (MAY_READ|MAY_WRITE|MAY_EXEC));
2048 
2049         /* Allow read access to binaries even when mode 111 */
2050         if (err == -EACCES && S_ISREG(inode->i_mode) &&
2051              (acc == (NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE) ||
2052               acc == (NFSD_MAY_READ | NFSD_MAY_READ_IF_EXEC)))
2053                 err = inode_permission(inode, MAY_EXEC);
2054 
2055         return err? nfserrno(err) : 0;
2056 }
2057 
2058 void
2059 nfsd_racache_shutdown(void)
2060 {
2061         struct raparms *raparm, *last_raparm;
2062         unsigned int i;
2063 
2064         dprintk("nfsd: freeing readahead buffers.\n");
2065 
2066         for (i = 0; i < RAPARM_HASH_SIZE; i++) {
2067                 raparm = raparm_hash[i].pb_head;
2068                 while(raparm) {
2069                         last_raparm = raparm;
2070                         raparm = raparm->p_next;
2071                         kfree(last_raparm);
2072                 }
2073                 raparm_hash[i].pb_head = NULL;
2074         }
2075 }
2076 /*
2077  * Initialize readahead param cache
2078  */
2079 int
2080 nfsd_racache_init(int cache_size)
2081 {
2082         int     i;
2083         int     j = 0;
2084         int     nperbucket;
2085         struct raparms **raparm = NULL;
2086 
2087 
2088         if (raparm_hash[0].pb_head)
2089                 return 0;
2090         nperbucket = DIV_ROUND_UP(cache_size, RAPARM_HASH_SIZE);
2091         nperbucket = max(2, nperbucket);
2092         cache_size = nperbucket * RAPARM_HASH_SIZE;
2093 
2094         dprintk("nfsd: allocating %d readahead buffers.\n", cache_size);
2095 
2096         for (i = 0; i < RAPARM_HASH_SIZE; i++) {
2097                 spin_lock_init(&raparm_hash[i].pb_lock);
2098 
2099                 raparm = &raparm_hash[i].pb_head;
2100                 for (j = 0; j < nperbucket; j++) {
2101                         *raparm = kzalloc(sizeof(struct raparms), GFP_KERNEL);
2102                         if (!*raparm)
2103                                 goto out_nomem;
2104                         raparm = &(*raparm)->p_next;
2105                 }
2106                 *raparm = NULL;
2107         }
2108 
2109         nfsdstats.ra_size = cache_size;
2110         return 0;
2111 
2112 out_nomem:
2113         dprintk("nfsd: kmalloc failed, freeing readahead buffers\n");
2114         nfsd_racache_shutdown();
2115         return -ENOMEM;
2116 }
2117 

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