FreeBSD/Linux Kernel Cross Reference
sys/fs/nfs/dir.c

     /*
      *  linux/fs/nfs/dir.c
      *
      *  Copyright (C) 1992  Rick Sladkey
      *
      *  nfs directory handling functions
      *
      * 10 Apr 1996  Added silly rename for unlink   --okir
      * 28 Sep 1996  Improved directory cache --okir
     * 23 Aug 1997  Claus Heine claus@momo.math.rwth-aachen.de 
     *              Re-implemented silly rename for unlink, newly implemented
     *              silly rename for nfs_rename() following the suggestions
     *              of Olaf Kirch (okir) found in this file.
     *              Following Linus comments on my original hack, this version
     *              depends only on the dcache stuff and doesn't touch the inode
     *              layer (iput() and friends).
     *  6 Jun 1999  Cache readdir lookups in the page cache. -DaveM
     */
    
    #include <linux/sched.h>
    #include <linux/errno.h>
    #include <linux/stat.h>
    #include <linux/fcntl.h>
    #include <linux/string.h>
    #include <linux/kernel.h>
    #include <linux/slab.h>
    #include <linux/mm.h>
    #include <linux/sunrpc/clnt.h>
    #include <linux/nfs_fs.h>
    #include <linux/nfs_mount.h>
    #include <linux/pagemap.h>
    #include <linux/smp_lock.h>
    
    #define NFS_PARANOIA 1
    /* #define NFS_DEBUG_VERBOSE 1 */
    
    static int nfs_readdir(struct file *, void *, filldir_t);
    static struct dentry *nfs_lookup(struct inode *, struct dentry *);
    static int nfs_create(struct inode *, struct dentry *, int);
    static int nfs_mkdir(struct inode *, struct dentry *, int);
    static int nfs_rmdir(struct inode *, struct dentry *);
    static int nfs_unlink(struct inode *, struct dentry *);
    static int nfs_symlink(struct inode *, struct dentry *, const char *);
    static int nfs_link(struct dentry *, struct inode *, struct dentry *);
    static int nfs_mknod(struct inode *, struct dentry *, int, int);
    static int nfs_rename(struct inode *, struct dentry *,
                          struct inode *, struct dentry *);
    static int nfs_fsync_dir(struct file *, struct dentry *, int);
    
    struct file_operations nfs_dir_operations = {
            read:           generic_read_dir,
            readdir:        nfs_readdir,
            open:           nfs_open,
            release:        nfs_release,
            fsync:          nfs_fsync_dir
    };
    
    struct inode_operations nfs_dir_inode_operations = {
            create:         nfs_create,
            lookup:         nfs_lookup,
            link:           nfs_link,
            unlink:         nfs_unlink,
            symlink:        nfs_symlink,
            mkdir:          nfs_mkdir,
            rmdir:          nfs_rmdir,
            mknod:          nfs_mknod,
            rename:         nfs_rename,
            permission:     nfs_permission,
            revalidate:     nfs_revalidate,
            setattr:        nfs_notify_change,
    };
    
    typedef u32 * (*decode_dirent_t)(u32 *, struct nfs_entry *, int);
    typedef struct {
            struct file     *file;
            struct page     *page;
            unsigned long   page_index;
            u32             *ptr;
            u64             target;
            struct nfs_entry *entry;
            decode_dirent_t decode;
            int             plus;
            int             error;
    } nfs_readdir_descriptor_t;
    
    /* Now we cache directories properly, by stuffing the dirent
     * data directly in the page cache.
     *
     * Inode invalidation due to refresh etc. takes care of
     * _everything_, no sloppy entry flushing logic, no extraneous
     * copying, network direct to page cache, the way it was meant
     * to be.
     *
     * NOTE: Dirent information verification is done always by the
     *       page-in of the RPC reply, nowhere else, this simplies
     *       things substantially.
     */
    static
    int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page *page)
   {
           struct file     *file = desc->file;
           struct inode    *inode = file->f_dentry->d_inode;
           struct rpc_cred *cred = nfs_file_cred(file);
           int             error;
   
           dfprintk(VFS, "NFS: nfs_readdir_filler() reading cookie %Lu into page %lu.\n", (long long)desc->entry->cookie, page->index);
   
    again:
           error = NFS_PROTO(inode)->readdir(inode, cred, desc->entry->cookie, page,
                                             NFS_SERVER(inode)->dtsize, desc->plus);
           /* We requested READDIRPLUS, but the server doesn't grok it */
           if (desc->plus && error == -ENOTSUPP) {
                   NFS_FLAGS(inode) &= ~NFS_INO_ADVISE_RDPLUS;
                   desc->plus = 0;
                   goto again;
           }
           if (error < 0)
                   goto error;
           SetPageUptodate(page);
           /* Ensure consistent page alignment of the data.
            * Note: assumes we have exclusive access to this mapping either
            *       throught inode->i_sem or some other mechanism.
            */
           if (page->index == 0)
                   invalidate_inode_pages(inode);
           UnlockPage(page);
           return 0;
    error:
           SetPageError(page);
           UnlockPage(page);
           invalidate_inode_pages(inode);
           desc->error = error;
           return -EIO;
   }
   
   static inline
   int dir_decode(nfs_readdir_descriptor_t *desc)
   {
           u32     *p = desc->ptr;
           p = desc->decode(p, desc->entry, desc->plus);
           if (IS_ERR(p))
                   return PTR_ERR(p);
           desc->ptr = p;
           return 0;
   }
   
   static inline
   void dir_page_release(nfs_readdir_descriptor_t *desc)
   {
           kunmap(desc->page);
           page_cache_release(desc->page);
           desc->page = NULL;
           desc->ptr = NULL;
   }
   
   /*
    * Given a pointer to a buffer that has already been filled by a call
    * to readdir, find the next entry.
    *
    * If the end of the buffer has been reached, return -EAGAIN, if not,
    * return the offset within the buffer of the next entry to be
    * read.
    */
   static inline
   int find_dirent(nfs_readdir_descriptor_t *desc, struct page *page)
   {
           struct nfs_entry *entry = desc->entry;
           int             loop_count = 0,
                           status;
   
           while((status = dir_decode(desc)) == 0) {
                   dfprintk(VFS, "NFS: found cookie %Lu\n", (long long)entry->cookie);
                   if (entry->prev_cookie == desc->target)
                           break;
                   if (loop_count++ > 200) {
                           loop_count = 0;
                           schedule();
                   }
           }
           dfprintk(VFS, "NFS: find_dirent() returns %d\n", status);
           return status;
   }
   
   /*
    * Find the given page, and call find_dirent() in order to try to
    * return the next entry.
    */
   static inline
   int find_dirent_page(nfs_readdir_descriptor_t *desc)
   {
           struct inode    *inode = desc->file->f_dentry->d_inode;
           struct page     *page;
           int             status;
   
           dfprintk(VFS, "NFS: find_dirent_page() searching directory page %ld\n", desc->page_index);
   
           desc->plus = NFS_USE_READDIRPLUS(inode);
           page = read_cache_page(&inode->i_data, desc->page_index,
                                  (filler_t *)nfs_readdir_filler, desc);
           if (IS_ERR(page)) {
                   status = PTR_ERR(page);
                   goto out;
           }
           if (!Page_Uptodate(page))
                   goto read_error;
   
           /* NOTE: Someone else may have changed the READDIRPLUS flag */
           desc->page = page;
           desc->ptr = kmap(page);
           status = find_dirent(desc, page);
           if (status < 0)
                   dir_page_release(desc);
    out:
           dfprintk(VFS, "NFS: find_dirent_page() returns %d\n", status);
           return status;
    read_error:
           page_cache_release(page);
           return -EIO;
   }
   
   /*
    * Recurse through the page cache pages, and return a
    * filled nfs_entry structure of the next directory entry if possible.
    *
    * The target for the search is 'desc->target'.
    */
   static inline
   int readdir_search_pagecache(nfs_readdir_descriptor_t *desc)
   {
           int             loop_count = 0;
           int             res;
   
           dfprintk(VFS, "NFS: readdir_search_pagecache() searching for cookie %Lu\n", (long long)desc->target);
           for (;;) {
                   res = find_dirent_page(desc);
                   if (res != -EAGAIN)
                           break;
                   /* Align to beginning of next page */
                   desc->page_index ++;
                   if (loop_count++ > 200) {
                           loop_count = 0;
                           schedule();
                   }
           }
           dfprintk(VFS, "NFS: readdir_search_pagecache() returned %d\n", res);
           return res;
   }
   
   /*
    * Once we've found the start of the dirent within a page: fill 'er up...
    */
   static 
   int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
                      filldir_t filldir)
   {
           struct file     *file = desc->file;
           struct nfs_entry *entry = desc->entry;
           unsigned long   fileid;
           int             loop_count = 0,
                           res;
   
           dfprintk(VFS, "NFS: nfs_do_filldir() filling starting @ cookie %Lu\n", (long long)desc->target);
   
           for(;;) {
                   /* Note: entry->prev_cookie contains the cookie for
                    *       retrieving the current dirent on the server */
                   fileid = nfs_fileid_to_ino_t(entry->ino);
                   res = filldir(dirent, entry->name, entry->len, 
                                 entry->prev_cookie, fileid, DT_UNKNOWN);
                   if (res < 0)
                           break;
                   file->f_pos = desc->target = entry->cookie;
                   if (dir_decode(desc) != 0) {
                           desc->page_index ++;
                           break;
                   }
                   if (loop_count++ > 200) {
                           loop_count = 0;
                           schedule();
                   }
           }
           dir_page_release(desc);
   
           dfprintk(VFS, "NFS: nfs_do_filldir() filling ended @ cookie %Lu; returning = %d\n", (long long)desc->target, res);
           return res;
   }
   
   /*
    * If we cannot find a cookie in our cache, we suspect that this is
    * because it points to a deleted file, so we ask the server to return
    * whatever it thinks is the next entry. We then feed this to filldir.
    * If all goes well, we should then be able to find our way round the
    * cache on the next call to readdir_search_pagecache();
    *
    * NOTE: we cannot add the anonymous page to the pagecache because
    *       the data it contains might not be page aligned. Besides,
    *       we should already have a complete representation of the
    *       directory in the page cache by the time we get here.
    */
   static inline
   int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
                        filldir_t filldir)
   {
           struct file     *file = desc->file;
           struct inode    *inode = file->f_dentry->d_inode;
           struct rpc_cred *cred = nfs_file_cred(file);
           struct page     *page = NULL;
           int             status;
   
           dfprintk(VFS, "NFS: uncached_readdir() searching for cookie %Lu\n", (long long)desc->target);
   
           page = alloc_page(GFP_HIGHUSER);
           if (!page) {
                   status = -ENOMEM;
                   goto out;
           }
           desc->error = NFS_PROTO(inode)->readdir(inode, cred, desc->target,
                                                   page,
                                                   NFS_SERVER(inode)->dtsize,
                                                   desc->plus);
           desc->page = page;
           desc->ptr = kmap(page);
           if (desc->error >= 0) {
                   if ((status = dir_decode(desc)) == 0)
                           desc->entry->prev_cookie = desc->target;
           } else
                   status = -EIO;
           if (status < 0)
                   goto out_release;
   
           status = nfs_do_filldir(desc, dirent, filldir);
   
           /* Reset read descriptor so it searches the page cache from
            * the start upon the next call to readdir_search_pagecache() */
           desc->page_index = 0;
           memset(desc->entry, 0, sizeof(*desc->entry));
    out:
           dfprintk(VFS, "NFS: uncached_readdir() returns %d\n", status);
           return status;
    out_release:
           dir_page_release(desc);
           goto out;
   }
   
   /* The file offset position is now represented as a true offset into the
    * page cache as is the case in most of the other filesystems.
    */
   static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
   {
           struct dentry   *dentry = filp->f_dentry;
           struct inode    *inode = dentry->d_inode;
           nfs_readdir_descriptor_t my_desc,
                           *desc = &my_desc;
           struct nfs_entry my_entry;
           long            res;
   
           res = nfs_revalidate(dentry);
           if (res < 0)
                   return res;
   
           /*
            * filp->f_pos points to the file offset in the page cache.
            * but if the cache has meanwhile been zapped, we need to
            * read from the last dirent to revalidate f_pos
            * itself.
            */
           memset(desc, 0, sizeof(*desc));
           memset(&my_entry, 0, sizeof(my_entry));
   
           desc->file = filp;
           desc->target = filp->f_pos;
           desc->entry = &my_entry;
           desc->decode = NFS_PROTO(inode)->decode_dirent;
   
           while(!desc->entry->eof) {
                   res = readdir_search_pagecache(desc);
                   if (res == -EBADCOOKIE) {
                           /* This means either end of directory */
                           if (desc->entry->cookie != desc->target) {
                                   /* Or that the server has 'lost' a cookie */
                                   res = uncached_readdir(desc, dirent, filldir);
                                   if (res >= 0)
                                           continue;
                           }
                           res = 0;
                           break;
                   } else if (res < 0)
                           break;
   
                   res = nfs_do_filldir(desc, dirent, filldir);
                   if (res < 0) {
                           res = 0;
                           break;
                   }
           }
           if (desc->error < 0)
                   return desc->error;
           if (res < 0)
                   return res;
           return 0;
   }
   
   /*
    * All directory operations under NFS are synchronous, so fsync()
    * is a dummy operation.
    */
   int nfs_fsync_dir(struct file *filp, struct dentry *dentry, int datasync)
   {
           return 0;
   }
   
   /*
    * A check for whether or not the parent directory has changed.
    * In the case it has, we assume that the dentries are untrustworthy
    * and may need to be looked up again.
    */
   static inline
   int nfs_check_verifier(struct inode *dir, struct dentry *dentry)
   {
           if (IS_ROOT(dentry))
                   return 1;
           if (nfs_revalidate_inode(NFS_SERVER(dir), dir))
                   return 0;
           return time_after(dentry->d_time, NFS_MTIME_UPDATE(dir));
   }
   
   /*
    * Whenever an NFS operation succeeds, we know that the dentry
    * is valid, so we update the revalidation timestamp.
    */
   static inline void nfs_renew_times(struct dentry * dentry)
   {
           dentry->d_time = jiffies;
   }
   
   static inline
   int nfs_lookup_verify_inode(struct inode *inode, int flags)
   {
           struct nfs_server *server = NFS_SERVER(inode);
           /*
            * If we're interested in close-to-open cache consistency,
            * then we revalidate the inode upon lookup.
            */
           if (!(server->flags & NFS_MOUNT_NOCTO) && !(flags & LOOKUP_CONTINUE))
                   NFS_CACHEINV(inode);
           return nfs_revalidate_inode(server, inode);
   }
   
   /*
    * We judge how long we want to trust negative
    * dentries by looking at the parent inode mtime.
    *
    * If parent mtime has changed, we revalidate, else we wait for a
    * period corresponding to the parent's attribute cache timeout value.
    */
   static inline int nfs_neg_need_reval(struct inode *dir, struct dentry *dentry)
   {
           if (!nfs_check_verifier(dir, dentry))
                   return 1;
           return time_after(jiffies, dentry->d_time + NFS_ATTRTIMEO(dir));
   }
   
   /*
    * This is called every time the dcache has a lookup hit,
    * and we should check whether we can really trust that
    * lookup.
    *
    * NOTE! The hit can be a negative hit too, don't assume
    * we have an inode!
    *
    * If the parent directory is seen to have changed, we throw out the
    * cached dentry and do a new lookup.
    */
   static int nfs_lookup_revalidate(struct dentry * dentry, int flags)
   {
           struct inode *dir;
           struct inode *inode;
           int error;
           struct nfs_fh fhandle;
           struct nfs_fattr fattr;
   
           lock_kernel();
           dir = dentry->d_parent->d_inode;
           inode = dentry->d_inode;
   
           if (!inode) {
                   if (nfs_neg_need_reval(dir, dentry))
                           goto out_bad;
                   goto out_valid;
           }
   
           if (is_bad_inode(inode)) {
                   dfprintk(VFS, "nfs_lookup_validate: %s/%s has dud inode\n",
                           dentry->d_parent->d_name.name, dentry->d_name.name);
                   goto out_bad;
           }
   
           /* Force a full look up iff the parent directory has changed */
           if (nfs_check_verifier(dir, dentry)) {
                   if (nfs_lookup_verify_inode(inode, flags))
                           goto out_bad;
                   goto out_valid;
           }
   
           if (NFS_STALE(inode))
                   goto out_bad;
   
           error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr);
           if (error)
                   goto out_bad;
           if (memcmp(NFS_FH(inode), &fhandle, sizeof(struct nfs_fh))!= 0)
                   goto out_bad;
           if ((error = nfs_refresh_inode(inode, &fattr)) != 0)
                   goto out_bad;
   
           nfs_renew_times(dentry);
    out_valid:
           unlock_kernel();
           return 1;
    out_bad:
           NFS_CACHEINV(dir);
           if (inode && S_ISDIR(inode->i_mode)) {
                   /* Purge readdir caches. */
                   nfs_zap_caches(inode);
                   /* If we have submounts, don't unhash ! */
                   if (have_submounts(dentry))
                           goto out_valid;
                   shrink_dcache_parent(dentry);
           }
           d_drop(dentry);
           unlock_kernel();
           return 0;
   }
   
   /*
    * This is called from dput() when d_count is going to 0.
    */
   static int nfs_dentry_delete(struct dentry *dentry)
   {
           dfprintk(VFS, "NFS: dentry_delete(%s/%s, %x)\n",
                   dentry->d_parent->d_name.name, dentry->d_name.name,
                   dentry->d_flags);
   
           if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
                   /* Unhash it, so that ->d_iput() would be called */
                   return 1;
           }
           return 0;
   
   }
   
   /*
    * Called when the dentry loses inode.
    * We use it to clean up silly-renamed files.
    */
   static void nfs_dentry_iput(struct dentry *dentry, struct inode *inode)
   {
           if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
                   lock_kernel();
                   nfs_complete_unlink(dentry);
                   unlock_kernel();
           }
           if (is_bad_inode(inode))
                   force_delete(inode);
           iput(inode);
   }
   
   struct dentry_operations nfs_dentry_operations = {
           d_revalidate:   nfs_lookup_revalidate,
           d_delete:       nfs_dentry_delete,
           d_iput:         nfs_dentry_iput,
   };
   
   static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry)
   {
           struct inode *inode;
           int error;
           struct nfs_fh fhandle;
           struct nfs_fattr fattr;
   
           dfprintk(VFS, "NFS: lookup(%s/%s)\n",
                   dentry->d_parent->d_name.name, dentry->d_name.name);
   
           error = -ENAMETOOLONG;
           if (dentry->d_name.len > NFS_SERVER(dir)->namelen)
                   goto out;
   
           error = -ENOMEM;
           dentry->d_op = &nfs_dentry_operations;
   
           error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr);
           inode = NULL;
           if (error == -ENOENT)
                   goto no_entry;
           if (!error) {
                   error = -EACCES;
                   inode = nfs_fhget(dentry, &fhandle, &fattr);
                   if (inode) {
               no_entry:
                           d_add(dentry, inode);
                           error = 0;
                   }
                   nfs_renew_times(dentry);
           }
   out:
           return ERR_PTR(error);
   }
   
   /*
    * Code common to create, mkdir, and mknod.
    */
   static int nfs_instantiate(struct dentry *dentry, struct nfs_fh *fhandle,
                                   struct nfs_fattr *fattr)
   {
           struct inode *inode;
           int error = -EACCES;
   
           if (fhandle->size == 0 || !(fattr->valid & NFS_ATTR_FATTR)) {
                   struct inode *dir = dentry->d_parent->d_inode;
                   error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, fhandle, fattr);
                   if (error)
                           goto out_err;
           }
           inode = nfs_fhget(dentry, fhandle, fattr);
           if (inode) {
                   d_instantiate(dentry, inode);
                   nfs_renew_times(dentry);
                   error = 0;
           }
           return error;
   out_err:
           d_drop(dentry);
           return error;
   }
   
   /*
    * Following a failed create operation, we drop the dentry rather
    * than retain a negative dentry. This avoids a problem in the event
    * that the operation succeeded on the server, but an error in the
    * reply path made it appear to have failed.
    */
   static int nfs_create(struct inode *dir, struct dentry *dentry, int mode)
   {
           struct iattr attr;
           struct nfs_fattr fattr;
           struct nfs_fh fhandle;
           int error;
   
           dfprintk(VFS, "NFS: create(%x/%ld, %s\n",
                   dir->i_dev, dir->i_ino, dentry->d_name.name);
   
           attr.ia_mode = mode;
           attr.ia_valid = ATTR_MODE;
   
           /*
            * The 0 argument passed into the create function should one day
            * contain the O_EXCL flag if requested. This allows NFSv3 to
            * select the appropriate create strategy. Currently open_namei
            * does not pass the create flags.
            */
           nfs_zap_caches(dir);
           error = NFS_PROTO(dir)->create(dir, &dentry->d_name,
                                            &attr, 0, &fhandle, &fattr);
           if (!error)
                   error = nfs_instantiate(dentry, &fhandle, &fattr);
           else
                   d_drop(dentry);
           return error;
   }
   
   /*
    * See comments for nfs_proc_create regarding failed operations.
    */
   static int nfs_mknod(struct inode *dir, struct dentry *dentry, int mode, int rdev)
   {
           struct iattr attr;
           struct nfs_fattr fattr;
           struct nfs_fh fhandle;
           int error;
   
           dfprintk(VFS, "NFS: mknod(%x/%ld, %s\n",
                   dir->i_dev, dir->i_ino, dentry->d_name.name);
   
           attr.ia_mode = mode;
           attr.ia_valid = ATTR_MODE;
   
           nfs_zap_caches(dir);
           error = NFS_PROTO(dir)->mknod(dir, &dentry->d_name, &attr, rdev,
                                           &fhandle, &fattr);
           if (!error)
                   error = nfs_instantiate(dentry, &fhandle, &fattr);
           else
                   d_drop(dentry);
           return error;
   }
   
   /*
    * See comments for nfs_proc_create regarding failed operations.
    */
   static int nfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
   {
           struct iattr attr;
           struct nfs_fattr fattr;
           struct nfs_fh fhandle;
           int error;
   
           dfprintk(VFS, "NFS: mkdir(%x/%ld, %s\n",
                   dir->i_dev, dir->i_ino, dentry->d_name.name);
   
           attr.ia_valid = ATTR_MODE;
           attr.ia_mode = mode | S_IFDIR;
   
   #if 0
           /*
            * Always drop the dentry, we can't always depend on
            * the fattr returned by the server (AIX seems to be
            * broken). We're better off doing another lookup than
            * depending on potentially bogus information.
            */
           d_drop(dentry);
   #endif
           nfs_zap_caches(dir);
           error = NFS_PROTO(dir)->mkdir(dir, &dentry->d_name, &attr, &fhandle,
                                           &fattr);
           if (!error)
                   error = nfs_instantiate(dentry, &fhandle, &fattr);
           else
                   d_drop(dentry);
           return error;
   }
   
   static int nfs_rmdir(struct inode *dir, struct dentry *dentry)
   {
           int error;
   
           dfprintk(VFS, "NFS: rmdir(%x/%ld, %s\n",
                   dir->i_dev, dir->i_ino, dentry->d_name.name);
   
           nfs_zap_caches(dir);
           error = NFS_PROTO(dir)->rmdir(dir, &dentry->d_name);
           if (!error)
                   dentry->d_inode->i_nlink = 0;
   
           return error;
   }
   
   static int nfs_sillyrename(struct inode *dir, struct dentry *dentry)
   {
           static unsigned int sillycounter;
           const int      i_inosize  = sizeof(dir->i_ino)*2;
           const int      countersize = sizeof(sillycounter)*2;
           const int      slen       = strlen(".nfs") + i_inosize + countersize;
           char           silly[slen+1];
           struct qstr    qsilly;
           struct dentry *sdentry;
           int            error = -EIO;
   
           dfprintk(VFS, "NFS: silly-rename(%s/%s, ct=%d)\n",
                   dentry->d_parent->d_name.name, dentry->d_name.name, 
                   atomic_read(&dentry->d_count));
   
           if (atomic_read(&dentry->d_count) == 1)
                   goto out;  /* No need to silly rename. */
   
   
   #ifdef NFS_PARANOIA
   if (!dentry->d_inode)
   printk("NFS: silly-renaming %s/%s, negative dentry??\n",
   dentry->d_parent->d_name.name, dentry->d_name.name);
   #endif
           /*
            * We don't allow a dentry to be silly-renamed twice.
            */
           error = -EBUSY;
           if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
                   goto out;
   
           sprintf(silly, ".nfs%*.*lx",
                   i_inosize, i_inosize, dentry->d_inode->i_ino);
   
           sdentry = NULL;
           do {
                   char *suffix = silly + slen - countersize;
   
                   dput(sdentry);
                   sillycounter++;
                   sprintf(suffix, "%*.*x", countersize, countersize, sillycounter);
   
                   dfprintk(VFS, "trying to rename %s to %s\n",
                            dentry->d_name.name, silly);
                   
                   sdentry = lookup_one_len(silly, dentry->d_parent, slen);
                   /*
                    * N.B. Better to return EBUSY here ... it could be
                    * dangerous to delete the file while it's in use.
                    */
                   if (IS_ERR(sdentry))
                           goto out;
           } while(sdentry->d_inode != NULL); /* need negative lookup */
   
           nfs_zap_caches(dir);
           qsilly.name = silly;
           qsilly.len  = strlen(silly);
           error = NFS_PROTO(dir)->rename(dir, &dentry->d_name, dir, &qsilly);
           if (!error) {
                   nfs_renew_times(dentry);
                   d_move(dentry, sdentry);
                   error = nfs_async_unlink(dentry);
                   /* If we return 0 we don't unlink */
           }
           dput(sdentry);
   out:
           return error;
   }
   
   /*
    * Remove a file after making sure there are no pending writes,
    * and after checking that the file has only one user. 
    *
    * We invalidate the attribute cache and free the inode prior to the operation
    * to avoid possible races if the server reuses the inode.
    */
   static int nfs_safe_remove(struct dentry *dentry)
   {
           struct inode *dir = dentry->d_parent->d_inode;
           struct inode *inode = dentry->d_inode;
           int error = -EBUSY, rehash = 0;
                   
           dfprintk(VFS, "NFS: safe_remove(%s/%s)\n",
                   dentry->d_parent->d_name.name, dentry->d_name.name);
   
           /*
            * Unhash the dentry while we remove the file ...
            */
           if (!d_unhashed(dentry)) {
                   d_drop(dentry);
                   rehash = 1;
           }
           if (atomic_read(&dentry->d_count) > 1) {
   #ifdef NFS_PARANOIA
                   printk("nfs_safe_remove: %s/%s busy, d_count=%d\n",
                           dentry->d_parent->d_name.name, dentry->d_name.name,
                           atomic_read(&dentry->d_count));
   #endif
                   goto out;
           }
   
           /* If the dentry was sillyrenamed, we simply call d_delete() */
           if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
                   error = 0;
                   goto out_delete;
           }
   
           nfs_zap_caches(dir);
           if (inode)
                   NFS_CACHEINV(inode);
           error = NFS_PROTO(dir)->remove(dir, &dentry->d_name);
           if (error < 0)
                   goto out;
           if (inode)
                   inode->i_nlink--;
   
    out_delete:
           /*
            * Free the inode
            */
           d_delete(dentry);
   out:
           if (rehash)
                   d_rehash(dentry);
           return error;
   }
   
   /*  We do silly rename. In case sillyrename() returns -EBUSY, the inode
    *  belongs to an active ".nfs..." file and we return -EBUSY.
    *
    *  If sillyrename() returns 0, we do nothing, otherwise we unlink.
    */
   static int nfs_unlink(struct inode *dir, struct dentry *dentry)
   {
           int error;
   
           dfprintk(VFS, "NFS: unlink(%x/%ld, %s)\n",
                   dir->i_dev, dir->i_ino, dentry->d_name.name);
   
           error = nfs_sillyrename(dir, dentry);
           if (error && error != -EBUSY) {
                   error = nfs_safe_remove(dentry);
                   if (!error) {
                           nfs_renew_times(dentry);
                   }
           }
           return error;
   }
   
   static int
   nfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
   {
           struct iattr attr;
           struct nfs_fattr sym_attr;
           struct nfs_fh sym_fh;
           struct qstr qsymname;
           unsigned int maxlen;
           int error;
   
           dfprintk(VFS, "NFS: symlink(%x/%ld, %s, %s)\n",
                   dir->i_dev, dir->i_ino, dentry->d_name.name, symname);
   
           error = -ENAMETOOLONG;
           maxlen = (NFS_PROTO(dir)->version==2) ? NFS2_MAXPATHLEN : NFS3_MAXPATHLEN;
           if (strlen(symname) > maxlen)
                   goto out;
   
   #ifdef NFS_PARANOIA
   if (dentry->d_inode)
   printk("nfs_proc_symlink: %s/%s not negative!\n",
   dentry->d_parent->d_name.name, dentry->d_name.name);
   #endif
           /*
            * Fill in the sattr for the call.
            * Note: SunOS 4.1.2 crashes if the mode isn't initialized!
            */
           attr.ia_valid = ATTR_MODE;
           attr.ia_mode = S_IFLNK | S_IRWXUGO;
   
           qsymname.name = symname;
           qsymname.len  = strlen(symname);
   
           nfs_zap_caches(dir);
           error = NFS_PROTO(dir)->symlink(dir, &dentry->d_name, &qsymname,
                                             &attr, &sym_fh, &sym_attr);
           if (!error) {
                   error = nfs_instantiate(dentry, &sym_fh, &sym_attr);
           } else {
                   if (error == -EEXIST)
                           printk("nfs_proc_symlink: %s/%s already exists??\n",
                                  dentry->d_parent->d_name.name, dentry->d_name.name);
                   d_drop(dentry);
           }
   
   out:
           return error;
   }
   
   static int 
   nfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
   {
           struct inode *inode = old_dentry->d_inode;
           int error;
   
           dfprintk(VFS, "NFS: link(%s/%s -> %s/%s)\n",
                   old_dentry->d_parent->d_name.name, old_dentry->d_name.name,
                   dentry->d_parent->d_name.name, dentry->d_name.name);
   
           /*
            * Drop the dentry in advance to force a new lookup.
            * Since nfs_proc_link doesn't return a file handle,
            * we can't use the existing dentry.
            */
           d_drop(dentry);
           nfs_zap_caches(dir);
           NFS_CACHEINV(inode);
           error = NFS_PROTO(dir)->link(inode, dir, &dentry->d_name);
           return error;
   }
   
   /*
    * RENAME
    * FIXME: Some nfsds, like the Linux user space nfsd, may generate a
    * different file handle for the same inode after a rename (e.g. when
    * moving to a different directory). A fail-safe method to do so would
    * be to look up old_dir/old_name, create a link to new_dir/new_name and
    * rename the old file using the sillyrename stuff. This way, the original
    * file in old_dir will go away when the last process iput()s the inode.
    *
    * FIXED.
    * 
    * It actually works quite well. One needs to have the possibility for
    * at least one ".nfs..." file in each directory the file ever gets
    * moved or linked to which happens automagically with the new
    * implementation that only depends on the dcache stuff instead of
    * using the inode layer
    *
    * Unfortunately, things are a little more complicated than indicated
    * above. For a cross-directory move, we want to make sure we can get
    * rid of the old inode after the operation.  This means there must be
    * no pending writes (if it's a file), and the use count must be 1.
    * If these conditions are met, we can drop the dentries before doing
    * the rename.
    */
   static int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
                         struct inode *new_dir, struct dentry *new_dentry)
   {
           struct inode *old_inode = old_dentry->d_inode;
           struct inode *new_inode = new_dentry->d_inode;
           struct dentry *dentry = NULL, *rehash = NULL;
           int error = -EBUSY;
   
           /*
           * To prevent any new references to the target during the rename,
           * we unhash the dentry and free the inode in advance.
           */
          if (!d_unhashed(new_dentry)) {
                  d_drop(new_dentry);
                  rehash = new_dentry;
          }
  
          dfprintk(VFS, "NFS: rename(%s/%s -> %s/%s, ct=%d)\n",
                   old_dentry->d_parent->d_name.name, old_dentry->d_name.name,
                   new_dentry->d_parent->d_name.name, new_dentry->d_name.name,
                   atomic_read(&new_dentry->d_count));
  
          /*
           * First check whether the target is busy ... we can't
           * safely do _any_ rename if the target is in use.
           *
           * For files, make a copy of the dentry and then do a 
           * silly-rename. If the silly-rename succeeds, the
           * copied dentry is hashed and becomes the new target.
           */
          if (!new_inode)
                  goto go_ahead;
          if (S_ISDIR(new_inode->i_mode))
                  goto out;
          else if (atomic_read(&new_dentry->d_count) > 1) {
                  int err;
                  /* copy the target dentry's name */
                  dentry = d_alloc(new_dentry->d_parent,
                                   &new_dentry->d_name);
                  if (!dentry)
                          goto out;
  
                  /* silly-rename the existing target ... */
                  err = nfs_sillyrename(new_dir, new_dentry);
                  if (!err) {
                          new_dentry = rehash = dentry;
                          new_inode = NULL;
                          /* instantiate the replacement target */
                          d_instantiate(new_dentry, NULL);
                  }
  
                  /* dentry still busy? */
                  if (atomic_read(&new_dentry->d_count) > 1) {
  #ifdef NFS_PARANOIA
                          printk("nfs_rename: target %s/%s busy, d_count=%d\n",
                                 new_dentry->d_parent->d_name.name,
                                 new_dentry->d_name.name,
                                 atomic_read(&new_dentry->d_count));
  #endif
                          goto out;
                  }
          }
  
  go_ahead:
          /*
           * ... prune child dentries and writebacks if needed.
           */
          if (atomic_read(&old_dentry->d_count) > 1) {
                  nfs_wb_all(old_inode);
                  shrink_dcache_parent(old_dentry);
          }
  
          if (new_inode)
                  d_delete(new_dentry);
  
          nfs_zap_caches(new_dir);
          nfs_zap_caches(old_dir);
          error = NFS_PROTO(old_dir)->rename(old_dir, &old_dentry->d_name,
                                             new_dir, &new_dentry->d_name);
  out:
          if (rehash)
                  d_rehash(rehash);
          if (!error && !S_ISDIR(old_inode->i_mode))
                  d_move(old_dentry, new_dentry);
  
          /* new dentry created? */
          if (dentry)
                  dput(dentry);
          return error;
  }
  
  int
  nfs_permission(struct inode *inode, int mask)
  {
          int                     error = vfs_permission(inode, mask);
  
          if (!NFS_PROTO(inode)->access)
                  goto out;
  
          if (error == -EROFS)
                  goto out;
  
          /*
           * Trust UNIX mode bits except:
           *
           * 1) When override capabilities may have been invoked
           * 2) When root squashing may be involved
           * 3) When ACLs may overturn a negative answer */
          if (!capable(CAP_DAC_OVERRIDE) && !capable(CAP_DAC_READ_SEARCH)
              && (current->fsuid != 0) && (current->fsgid != 0)
              && error != -EACCES)
                  goto out;
  
          error = NFS_PROTO(inode)->access(inode, mask, 0);
  
          if (error == -EACCES && NFS_CLIENT(inode)->cl_droppriv &&
              current->uid != 0 && current->gid != 0 &&
              (current->fsuid != current->uid || current->fsgid != current->gid))
                  error = NFS_PROTO(inode)->access(inode, mask, 1);
  
   out:
          return error;
  }
  
  /*
   * Local variables:
   *  version-control: t
   *  kept-new-versions: 5
   * End:
   */

Cache object: 44cbcf3e168e37b7d288e7fc0589cf22