Linux-2.4.0-test2

[davej-history.git] / fs / nfs / inode.c

/*
 *  linux/fs/nfs/inode.c
 *
 *  Copyright (C) 1992  Rick Sladkey
 *
 *  nfs inode and superblock handling functions
 *
 *  Modularised by Alan Cox <Alan.Cox@linux.org>, while hacking some
 *  experimental NFS changes. Modularisation taken straight from SYS5 fs.
 *
 *  Change to nfs_read_super() to permit NFS mounts to multi-homed hosts.
 *  J.S.Peatfield@damtp.cam.ac.uk
 *
 */

#include <linux/config.h>
#include <linux/module.h>

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/locks.h>
#include <linux/unistd.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/stats.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/nfs_flushd.h>
#include <linux/lockd/bind.h>
#include <linux/smp_lock.h>

#include <asm/system.h>
#include <asm/uaccess.h>

#define CONFIG_NFS_SNAPSHOT 1
#define NFSDBG_FACILITY         NFSDBG_VFS
#define NFS_PARANOIA 1

static struct inode * __nfs_fhget(struct super_block *, struct nfs_fattr *);
void nfs_zap_caches(struct inode *);
static void nfs_invalidate_inode(struct inode *);

static void nfs_read_inode(struct inode *);
static void nfs_delete_inode(struct inode *);
static void nfs_put_super(struct super_block *);
static void nfs_umount_begin(struct super_block *);
static int  nfs_statfs(struct super_block *, struct statfs *);

static struct super_operations nfs_sops = { 
        read_inode:     nfs_read_inode,
        put_inode:      force_delete,
        delete_inode:   nfs_delete_inode,
        put_super:      nfs_put_super,
        statfs:         nfs_statfs,
        umount_begin:   nfs_umount_begin,
};

/*
 * RPC cruft for NFS
 */
struct rpc_stat                 nfs_rpcstat = { &nfs_program };
static struct rpc_version *     nfs_version[] = {
        NULL,
        NULL,
        &nfs_version2,
#ifdef CONFIG_NFS_V3
        &nfs_version3,
#endif
};

struct rpc_program              nfs_program = {
        "nfs",
        NFS_PROGRAM,
        sizeof(nfs_version) / sizeof(nfs_version[0]),
        nfs_version,
        &nfs_rpcstat,
};

static inline unsigned long
nfs_fattr_to_ino_t(struct nfs_fattr *fattr)
{
        return nfs_fileid_to_ino_t(fattr->fileid);
}

/*
 * The "read_inode" function doesn't actually do anything:
 * the real data is filled in later in nfs_fhget. Here we
 * just mark the cache times invalid, and zero out i_mode
 * (the latter makes "nfs_refresh_inode" do the right thing
 * wrt pipe inodes)
 */
static void
nfs_read_inode(struct inode * inode)
{
        inode->i_blksize = inode->i_sb->s_blocksize;
        inode->i_mode = 0;
        inode->i_rdev = 0;
        NFS_FILEID(inode) = 0;
        NFS_FSID(inode) = 0;
        INIT_LIST_HEAD(&inode->u.nfs_i.read);
        INIT_LIST_HEAD(&inode->u.nfs_i.dirty);
        INIT_LIST_HEAD(&inode->u.nfs_i.commit);
        INIT_LIST_HEAD(&inode->u.nfs_i.writeback);
        inode->u.nfs_i.nread = 0;
        inode->u.nfs_i.ndirty = 0;
        inode->u.nfs_i.ncommit = 0;
        inode->u.nfs_i.npages = 0;
        NFS_CACHEINV(inode);
        NFS_ATTRTIMEO(inode) = NFS_MINATTRTIMEO(inode);
        NFS_ATTRTIMEO_UPDATE(inode) = jiffies;
}

static void
nfs_delete_inode(struct inode * inode)
{
        dprintk("NFS: delete_inode(%x/%ld)\n", inode->i_dev, inode->i_ino);

        /*
         * The following can never actually happen...
         */
        if (nfs_have_writebacks(inode) || nfs_have_read(inode)) {
                printk(KERN_ERR "nfs_delete_inode: inode %ld has pending RPC requests\n", inode->i_ino);
        }

        clear_inode(inode);
}

void
nfs_put_super(struct super_block *sb)
{
        struct nfs_server *server = &sb->u.nfs_sb.s_server;
        struct rpc_clnt *rpc;

        /*
         * First get rid of the request flushing daemon.
         * Relies on rpc_shutdown_client() waiting on all
         * client tasks to finish.
         */
        nfs_reqlist_exit(server);

        if ((rpc = server->client) != NULL)
                rpc_shutdown_client(rpc);

        nfs_reqlist_free(server);

        if (!(server->flags & NFS_MOUNT_NONLM))
                lockd_down();   /* release rpc.lockd */
        rpciod_down();          /* release rpciod */

        kfree(server->hostname);
}

void
nfs_umount_begin(struct super_block *sb)
{
        struct nfs_server *server = &sb->u.nfs_sb.s_server;
        struct rpc_clnt *rpc;

        /* -EIO all pending I/O */
        if ((rpc = server->client) != NULL)
                rpc_killall_tasks(rpc);
}


static inline unsigned long
nfs_block_bits(unsigned long bsize, unsigned char *nrbitsp)
{
        /* make sure blocksize is a power of two */
        if ((bsize & (bsize - 1)) || nrbitsp) {
                unsigned char   nrbits;

                for (nrbits = 31; nrbits && !(bsize & (1 << nrbits)); nrbits--)
                        ;
                bsize = 1 << nrbits;
                if (nrbitsp)
                        *nrbitsp = nrbits;
        }

        return bsize;
}

/*
 * Calculate the number of 512byte blocks used.
 */
static inline unsigned long
nfs_calc_block_size(u64 tsize)
{
        loff_t used = (tsize + 511) >> 9;
        return (used > ULONG_MAX) ? ULONG_MAX : used;
}

/*
 * Compute and set NFS server blocksize
 */
static inline unsigned long
nfs_block_size(unsigned long bsize, unsigned char *nrbitsp)
{
        if (bsize < 1024)
                bsize = NFS_DEF_FILE_IO_BUFFER_SIZE;
        else if (bsize >= NFS_MAX_FILE_IO_BUFFER_SIZE)
                bsize = NFS_MAX_FILE_IO_BUFFER_SIZE;

        return nfs_block_bits(bsize, nrbitsp);
}

/*
 * Obtain the root inode of the file system.
 */
static struct inode *
nfs_get_root(struct super_block *sb, struct nfs_fh *rootfh)
{
        struct nfs_server       *server = &sb->u.nfs_sb.s_server;
        struct nfs_fattr        fattr;
        struct inode            *inode;
        int                     error;

        if ((error = server->rpc_ops->getroot(server, rootfh, &fattr)) < 0) {
                printk(KERN_NOTICE "nfs_get_root: getattr error = %d\n", -error);
                return NULL;
        }

        inode = __nfs_fhget(sb, &fattr);
        return inode;
}

extern struct nfs_fh *nfs_fh_alloc(void);
extern void nfs_fh_free(struct nfs_fh *p);

/*
 * The way this works is that the mount process passes a structure
 * in the data argument which contains the server's IP address
 * and the root file handle obtained from the server's mount
 * daemon. We stash these away in the private superblock fields.
 */
struct super_block *
nfs_read_super(struct super_block *sb, void *raw_data, int silent)
{
        struct nfs_mount_data   *data = (struct nfs_mount_data *) raw_data;
        struct nfs_server       *server;
        struct rpc_xprt         *xprt = NULL;
        struct rpc_clnt         *clnt = NULL;
        struct nfs_fh           *root = &data->root, *root_fh, fh;
        struct inode            *root_inode = NULL;
        unsigned int            authflavor;
        struct sockaddr_in      srvaddr;
        struct rpc_timeout      timeparms;
        struct nfs_fsinfo       fsinfo;
        int                     tcp, version, maxlen;

        memset(&sb->u.nfs_sb, 0, sizeof(sb->u.nfs_sb));
        if (!data)
                goto out_miss_args;

        memset(&fh, 0, sizeof(fh));
        if (data->version != NFS_MOUNT_VERSION) {
                printk("nfs warning: mount version %s than kernel\n",
                        data->version < NFS_MOUNT_VERSION ? "older" : "newer");
                if (data->version < 2)
                        data->namlen = 0;
                if (data->version < 3)
                        data->bsize  = 0;
                if (data->version < 4) {
                        data->flags &= ~NFS_MOUNT_VER3;
                        root = &fh;
                        root->size = NFS2_FHSIZE;
                        memcpy(root->data, data->old_root.data, NFS2_FHSIZE);
                }
        }

        /* We now require that the mount process passes the remote address */
        memcpy(&srvaddr, &data->addr, sizeof(srvaddr));
        if (srvaddr.sin_addr.s_addr == INADDR_ANY)
                goto out_no_remote;

        sb->s_flags |= MS_ODD_RENAME; /* This should go away */

        sb->s_magic      = NFS_SUPER_MAGIC;
        sb->s_op         = &nfs_sops;
        sb->s_blocksize_bits = 0;
        sb->s_blocksize  = nfs_block_size(data->bsize, &sb->s_blocksize_bits);
        server           = &sb->u.nfs_sb.s_server;
        server->rsize    = nfs_block_size(data->rsize, NULL);
        server->wsize    = nfs_block_size(data->wsize, NULL);
        server->flags    = data->flags & NFS_MOUNT_FLAGMASK;

        if (data->flags & NFS_MOUNT_NOAC) {
                data->acregmin = data->acregmax = 0;
                data->acdirmin = data->acdirmax = 0;
        }
        server->acregmin = data->acregmin*HZ;
        server->acregmax = data->acregmax*HZ;
        server->acdirmin = data->acdirmin*HZ;
        server->acdirmax = data->acdirmax*HZ;

        server->namelen  = data->namlen;
        server->hostname = kmalloc(strlen(data->hostname) + 1, GFP_KERNEL);
        if (!server->hostname)
                goto out_unlock;
        strcpy(server->hostname, data->hostname);

 nfsv3_try_again:
        /* Check NFS protocol revision and initialize RPC op vector
         * and file handle pool. */
        if (data->flags & NFS_MOUNT_VER3) {
#ifdef CONFIG_NFS_V3
                server->rpc_ops = &nfs_v3_clientops;
                version = 3;
                if (data->version < 4) {
                        printk(KERN_NOTICE "NFS: NFSv3 not supported by mount program.\n");
                        goto out_unlock;
                }
#else
                printk(KERN_NOTICE "NFS: NFSv3 not supported.\n");
                goto out_unlock;
#endif
        } else {
                server->rpc_ops = &nfs_v2_clientops;
                version = 2;
        }

        /* Which protocol do we use? */
        tcp   = (data->flags & NFS_MOUNT_TCP);

        /* Initialize timeout values */
        timeparms.to_initval = data->timeo * HZ / 10;
        timeparms.to_retries = data->retrans;
        timeparms.to_maxval  = tcp? RPC_MAX_TCP_TIMEOUT : RPC_MAX_UDP_TIMEOUT;
        timeparms.to_exponential = 1;

        if (!timeparms.to_initval)
                timeparms.to_initval = (tcp ? 600 : 11) * HZ / 10;
        if (!timeparms.to_retries)
                timeparms.to_retries = 5;

        /* Now create transport and client */
        xprt = xprt_create_proto(tcp? IPPROTO_TCP : IPPROTO_UDP,
                                                &srvaddr, &timeparms);
        if (xprt == NULL)
                goto out_no_xprt;

        /* Choose authentication flavor */
        authflavor = RPC_AUTH_UNIX;
        if (data->flags & NFS_MOUNT_SECURE)
                authflavor = RPC_AUTH_DES;
        else if (data->flags & NFS_MOUNT_KERBEROS)
                authflavor = RPC_AUTH_KRB;

        clnt = rpc_create_client(xprt, server->hostname, &nfs_program,
                                 version, authflavor);
        if (clnt == NULL)
                goto out_no_client;

        clnt->cl_intr     = (data->flags & NFS_MOUNT_INTR)? 1 : 0;
        clnt->cl_softrtry = (data->flags & NFS_MOUNT_SOFT)? 1 : 0;
        clnt->cl_chatty   = 1;
        server->client    = clnt;

        /* Fire up rpciod if not yet running */
        if (rpciod_up() != 0)
                goto out_no_iod;

        /*
         * Keep the super block locked while we try to get 
         * the root fh attributes.
         */
        root_fh = nfs_fh_alloc();
        if (!root_fh)
                goto out_no_fh;
        memcpy((u8*)root_fh, (u8*)root, sizeof(*root));

        /* Did getting the root inode fail? */
        if (!(root_inode = nfs_get_root(sb, root))
            && (data->flags & NFS_MOUNT_VER3)) {
                data->flags &= ~NFS_MOUNT_VER3;
                nfs_fh_free(root_fh);
                rpciod_down();
                rpc_shutdown_client(server->client);
                goto nfsv3_try_again;
        }

        if (!root_inode)
                goto out_no_root;
        sb->s_root = d_alloc_root(root_inode);
        if (!sb->s_root)
                goto out_no_root;

        sb->s_root->d_op = &nfs_dentry_operations;
        sb->s_root->d_fsdata = root_fh;

        /* Get some general file system info */
        if (server->rpc_ops->statfs(server, root, &fsinfo) >= 0) {
                if (server->namelen == 0)
                        server->namelen = fsinfo.namelen;
        } else {
                printk(KERN_NOTICE "NFS: cannot retrieve file system info.\n");
                goto out_no_root;
        }

        /* Work out a lot of parameters */
        if (data->rsize == 0)
                server->rsize = nfs_block_size(fsinfo.rtpref, NULL);
        if (data->wsize == 0)
                server->wsize = nfs_block_size(fsinfo.wtpref, NULL);
        server->dtsize = nfs_block_size(fsinfo.dtpref, NULL);
        if (server->dtsize > PAGE_CACHE_SIZE)
                server->dtsize = PAGE_CACHE_SIZE;
        /* NFSv3: we don't have bsize, but rather rtmult and wtmult... */
        if (!fsinfo.bsize)
                fsinfo.bsize = (fsinfo.rtmult>fsinfo.wtmult) ? fsinfo.rtmult : fsinfo.wtmult;
        /* Also make sure we don't go below rsize/wsize since
         * RPC calls are expensive */
        if (fsinfo.bsize < server->rsize)
                fsinfo.bsize = server->rsize;
        if (fsinfo.bsize < server->wsize)
                fsinfo.bsize = server->wsize;

        if (data->bsize == 0)
                sb->s_blocksize = nfs_block_bits(fsinfo.bsize, &sb->s_blocksize_bits);
        if (server->rsize > fsinfo.rtmax)
                server->rsize = fsinfo.rtmax;
        if (server->wsize > fsinfo.wtmax)
                server->wsize = fsinfo.wtmax;

        server->rpages = (server->rsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
        if (server->rpages > NFS_READ_MAXIOV) {
                server->rpages = NFS_READ_MAXIOV;
                server->rsize = server->rpages << PAGE_CACHE_SHIFT;
        }

        server->wpages = (server->wsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
        if (server->wpages > NFS_WRITE_MAXIOV) {
                server->wpages = NFS_WRITE_MAXIOV;
                server->wsize = server->wpages << PAGE_CACHE_SHIFT;
        }

        maxlen = (version == 2) ? NFS2_MAXNAMLEN : NFS3_MAXNAMLEN;

        if (server->namelen == 0 || server->namelen > maxlen)
                server->namelen = maxlen;

        /* Fire up the writeback cache */
        if (nfs_reqlist_alloc(server) < 0) {
                printk(KERN_NOTICE "NFS: cannot initialize writeback cache.\n");
                goto failure_kill_reqlist;
        }

        /* We're airborne */

        /* Check whether to start the lockd process */
        if (!(server->flags & NFS_MOUNT_NONLM))
                lockd_up();
        return sb;

        /* Yargs. It didn't work out. */
 failure_kill_reqlist:
        nfs_reqlist_exit(server);
out_no_root:
        printk("nfs_read_super: get root inode failed\n");
        iput(root_inode);
        nfs_fh_free(root_fh);
out_no_fh:
        rpciod_down();
        goto out_shutdown;

out_no_iod:
        printk(KERN_WARNING "NFS: couldn't start rpciod!\n");
out_shutdown:
        rpc_shutdown_client(server->client);
        goto out_free_host;

out_no_client:
        printk(KERN_WARNING "NFS: cannot create RPC client.\n");
        xprt_destroy(xprt);
        goto out_free_host;

out_no_xprt:
        printk(KERN_WARNING "NFS: cannot create RPC transport.\n");

out_free_host:
        nfs_reqlist_free(server);
        kfree(server->hostname);
out_unlock:
        goto out_fail;

out_no_remote:
        printk("NFS: mount program didn't pass remote address!\n");
        goto out_fail;

out_miss_args:
        printk("nfs_read_super: missing data argument\n");

out_fail:
        return NULL;
}

static int
nfs_statfs(struct super_block *sb, struct statfs *buf)
{
        struct nfs_server *server = &sb->u.nfs_sb.s_server;
        unsigned char blockbits;
        unsigned long blockres;
        struct nfs_fsinfo res;
        int error;

        error = server->rpc_ops->statfs(server, NFS_FH(sb->s_root), &res);
        buf->f_type = NFS_SUPER_MAGIC;
        if (error < 0)
                goto out_err;

        if (res.bsize == 0)
                res.bsize = sb->s_blocksize;
        buf->f_bsize = nfs_block_bits(res.bsize, &blockbits);
        blockres = (1 << blockbits) - 1;
        buf->f_blocks = (res.tbytes + blockres) >> blockbits;
        buf->f_bfree = (res.fbytes + blockres) >> blockbits;
        buf->f_bavail = (res.abytes + blockres) >> blockbits;
        buf->f_files = res.tfiles;
        buf->f_ffree = res.afiles;
        if (res.namelen == 0 || res.namelen > server->namelen)
                res.namelen = server->namelen;
        buf->f_namelen = res.namelen;
        return 0;
 out_err:
        printk("nfs_statfs: statfs error = %d\n", -error);
        buf->f_bsize = buf->f_blocks = buf->f_bfree = buf->f_bavail = -1;
        return 0;
}

/*
 * Free all unused dentries in an inode's alias list.
 *
 * Subtle note: we have to be very careful not to cause
 * any IO operations with the stale dentries, as this
 * could cause file corruption. But since the dentry
 * count is 0 and all pending IO for a dentry has been
 * flushed when the count went to 0, we're safe here.
 * Also returns the number of unhashed dentries
 */
static int
nfs_free_dentries(struct inode *inode)
{
        struct list_head *tmp, *head = &inode->i_dentry;
        int unhashed;

        if (S_ISDIR(inode->i_mode)) {
                struct dentry *dentry = d_find_alias(inode);
                if (dentry) {
                        shrink_dcache_parent(dentry);
                        dput(dentry);
                }
        }
        d_prune_aliases(inode);
        tmp = head;
        unhashed = 0;
        while ((tmp = tmp->next) != head) {
                struct dentry *dentry = list_entry(tmp, struct dentry, d_alias);
                if (d_unhashed(dentry))
                        unhashed++;
        }
        return unhashed;
}

/*
 * Invalidate the local caches
 */
void
nfs_zap_caches(struct inode *inode)
{
        NFS_ATTRTIMEO(inode) = NFS_MINATTRTIMEO(inode);
        NFS_ATTRTIMEO_UPDATE(inode) = jiffies;

        invalidate_inode_pages(inode);

        memset(NFS_COOKIEVERF(inode), 0, sizeof(NFS_COOKIEVERF(inode)));
        NFS_CACHEINV(inode);
}

/*
 * Invalidate, but do not unhash, the inode
 */
static void
nfs_invalidate_inode(struct inode *inode)
{
        umode_t save_mode = inode->i_mode;

        make_bad_inode(inode);
        inode->i_mode = save_mode;
        nfs_zap_caches(inode);
}

/*
 * Fill in inode information from the fattr.
 */
static void
nfs_fill_inode(struct inode *inode, struct nfs_fattr *fattr)
{
        /*
         * Check whether the mode has been set, as we only want to
         * do this once. (We don't allow inodes to change types.)
         */
        if (inode->i_mode == 0) {
                NFS_FILEID(inode) = fattr->fileid;
                NFS_FSID(inode) = fattr->fsid;
                inode->i_mode = fattr->mode;
                /* Why so? Because we want revalidate for devices/FIFOs, and
                 * that's precisely what we have in nfs_file_inode_operations.
                 */
                inode->i_op = &nfs_file_inode_operations;
                if (S_ISREG(inode->i_mode)) {
                        inode->i_fop = &nfs_file_operations;
                        inode->i_data.a_ops = &nfs_file_aops;
                } else if (S_ISDIR(inode->i_mode)) {
                        inode->i_op = &nfs_dir_inode_operations;
                        inode->i_fop = &nfs_dir_operations;
                } else if (S_ISLNK(inode->i_mode))
                        inode->i_op = &nfs_symlink_inode_operations;
                else
                        init_special_inode(inode, inode->i_mode, fattr->rdev);
                /*
                 * Preset the size and mtime, as there's no need
                 * to invalidate the caches.
                 */ 
                inode->i_size  = nfs_size_to_loff_t(fattr->size);
                inode->i_mtime = nfs_time_to_secs(fattr->mtime);
                inode->i_atime = nfs_time_to_secs(fattr->atime);
                inode->i_ctime = nfs_time_to_secs(fattr->ctime);
                NFS_CACHE_CTIME(inode) = fattr->ctime;
                NFS_CACHE_MTIME(inode) = fattr->mtime;
                NFS_CACHE_ATIME(inode) = fattr->atime;
                NFS_CACHE_ISIZE(inode) = fattr->size;
                NFS_ATTRTIMEO(inode) = NFS_MINATTRTIMEO(inode);
                NFS_ATTRTIMEO_UPDATE(inode) = jiffies;
        }
        nfs_refresh_inode(inode, fattr);
}

/*
 * In NFSv3 we can have 64bit inode numbers. In order to support
 * this, and re-exported directories (also seen in NFSv2)
 * we are forced to allow 2 different inodes to have the same
 * i_ino.
 */
static int
nfs_find_actor(struct inode *inode, unsigned long ino, void *opaque)
{
        struct nfs_fattr *fattr = (struct nfs_fattr *)opaque;
        if (NFS_FSID(inode) != fattr->fsid)
                return 0;
        if (NFS_FILEID(inode) != fattr->fileid)
                return 0;
        return 1;
}

static int
nfs_inode_is_stale(struct inode *inode, struct nfs_fattr *fattr)
{
        int unhashed;
        int is_stale = 0;

        if (inode->i_mode &&
            (fattr->mode & S_IFMT) != (inode->i_mode & S_IFMT))
                is_stale = 1;

        if (is_bad_inode(inode))
                is_stale = 1;

        /*
         * If the inode seems stale, free up cached dentries.
         */
        unhashed = nfs_free_dentries(inode);

        /* Assume we're holding an i_count
         *
         * NB: sockets sometimes have volatile file handles
         *     don't invalidate their inodes even if all dentries are
         *     unhashed.
         */
        if (unhashed && atomic_read(&inode->i_count) == unhashed + 1
            && !S_ISSOCK(inode->i_mode) && !S_ISFIFO(inode->i_mode))
                is_stale = 1;

        return is_stale;
}

/*
 * This is our own version of iget that looks up inodes by file handle
 * instead of inode number.  We use this technique instead of using
 * the vfs read_inode function because there is no way to pass the
 * file handle or current attributes into the read_inode function.
 *
 * We provide a special check for NetApp .snapshot directories to avoid
 * inode aliasing problems. All snapshot inodes are anonymous (unhashed).
 */
struct inode *
nfs_fhget(struct dentry *dentry, struct nfs_fh *fhandle,
                                 struct nfs_fattr *fattr)
{
        struct super_block *sb = dentry->d_sb;

        dprintk("NFS: nfs_fhget(%s/%s fileid=%Ld)\n",
                dentry->d_parent->d_name.name, dentry->d_name.name,
                (long long)fattr->fileid);

        /* Install the file handle in the dentry */
        memcpy(dentry->d_fsdata, fhandle, sizeof(struct nfs_fh));

#ifdef CONFIG_NFS_SNAPSHOT
        /*
         * Check for NetApp snapshot dentries, and get an 
         * unhashed inode to avoid aliasing problems.
         */
        if ((dentry->d_parent->d_inode->u.nfs_i.flags & NFS_IS_SNAPSHOT) ||
            (dentry->d_name.len == 9 &&
             memcmp(dentry->d_name.name, ".snapshot", 9) == 0)) {
                struct inode *inode = get_empty_inode();
                if (!inode)
                        goto out;       
                inode->i_sb = sb;
                inode->i_dev = sb->s_dev;
                inode->i_flags = 0;
                inode->i_ino = nfs_fattr_to_ino_t(fattr);
                nfs_read_inode(inode);
                nfs_fill_inode(inode, fattr);
                inode->u.nfs_i.flags |= NFS_IS_SNAPSHOT;
                dprintk("NFS: nfs_fhget(snapshot ino=%ld)\n", inode->i_ino);
        out:
                return inode;
        }
#endif
        return __nfs_fhget(sb, fattr);
}

/*
 * Look up the inode by super block and fattr->fileid.
 *
 * Note carefully the special handling of busy inodes (i_count > 1).
 * With the kernel 2.1.xx dcache all inodes except hard links must
 * have i_count == 1 after iget(). Otherwise, it indicates that the
 * server has reused a fileid (i_ino) and we have a stale inode.
 */
static struct inode *
__nfs_fhget(struct super_block *sb, struct nfs_fattr *fattr)
{
        struct inode *inode = NULL;
        unsigned long ino;

        if ((fattr->valid & NFS_ATTR_FATTR) == 0)
                goto out_no_inode;

        if (!fattr->nlink) {
                printk("NFS: Buggy server - nlink == 0!\n");
                goto out_no_inode;
        }

        ino = nfs_fattr_to_ino_t(fattr);

        while((inode = iget4(sb, ino, nfs_find_actor, fattr)) != NULL) {

                /*
                 * Check for busy inodes, and attempt to get rid of any
                 * unused local references. If successful, we release the
                 * inode and try again.
                 *
                 * Note that the busy test uses the values in the fattr,
                 * as the inode may have become a different object.
                 * (We can probably handle modes changes here, too.)
                 */
                if (!nfs_inode_is_stale(inode,fattr))
                        break;

                dprintk("__nfs_fhget: inode %ld still busy, i_count=%d\n",
                       inode->i_ino, atomic_read(&inode->i_count));
                nfs_zap_caches(inode);
                remove_inode_hash(inode);
                iput(inode);
        }

        if (!inode)
                goto out_no_inode;

        nfs_fill_inode(inode, fattr);
        dprintk("NFS: __nfs_fhget(%x/%ld ct=%d)\n",
                inode->i_dev, inode->i_ino, atomic_read(&inode->i_count));

out:
        return inode;

out_no_inode:
        printk("__nfs_fhget: iget failed\n");
        goto out;
}

int
nfs_notify_change(struct dentry *dentry, struct iattr *attr)
{
        struct inode *inode = dentry->d_inode;
        struct nfs_fattr fattr;
        int error;

        /*
         * Make sure the inode is up-to-date.
         */
        error = nfs_revalidate(dentry);
        if (error) {
#ifdef NFS_PARANOIA
printk("nfs_notify_change: revalidate failed, error=%d\n", error);
#endif
                goto out;
        }

        if (!S_ISREG(inode->i_mode))
                attr->ia_valid &= ~ATTR_SIZE;

        error = nfs_wb_all(inode);
        if (error)
                goto out;

        error = NFS_PROTO(inode)->setattr(dentry, &fattr, attr);
        if (error)
                goto out;
        /*
         * If we changed the size or mtime, update the inode
         * now to avoid invalidating the page cache.
         */
        if (attr->ia_valid & ATTR_SIZE) {
                if (attr->ia_size != fattr.size)
                        printk("nfs_notify_change: attr=%Ld, fattr=%Ld??\n",
                               (long long) attr->ia_size, (long long)fattr.size);
                vmtruncate(inode, attr->ia_size);
        }

        /*
         * If we changed the size or mtime, update the inode
         * now to avoid invalidating the page cache.
         */
        if (!(fattr.valid & NFS_ATTR_WCC)) {
                fattr.pre_size = NFS_CACHE_ISIZE(inode);
                fattr.pre_mtime = NFS_CACHE_MTIME(inode);
                fattr.pre_ctime = NFS_CACHE_CTIME(inode);
                fattr.valid |= NFS_ATTR_WCC;
        }
        error = nfs_refresh_inode(inode, &fattr);
out:
        return error;
}

/*
 * Wait for the inode to get unlocked.
 * (Used for NFS_INO_LOCKED and NFS_INO_REVALIDATING).
 */
int
nfs_wait_on_inode(struct inode *inode, int flag)
{
        struct rpc_clnt *clnt = NFS_CLIENT(inode);
        int error;
        if (!(NFS_FLAGS(inode) & flag))
                return 0;
        atomic_inc(&inode->i_count);
        error = nfs_wait_event(clnt, inode->i_wait, !(NFS_FLAGS(inode) & flag));
        iput(inode);
        return error;
}

/*
 * Externally visible revalidation function
 */
int
nfs_revalidate(struct dentry *dentry)
{
        return nfs_revalidate_inode(NFS_DSERVER(dentry), dentry);
}

/*
 * These are probably going to contain hooks for
 * allocating and releasing RPC credentials for
 * the file. I'll have to think about Tronds patch
 * a bit more..
 */
int nfs_open(struct inode *inode, struct file *filp)
{
        struct rpc_auth *auth = NFS_CLIENT(inode)->cl_auth;
        struct rpc_cred *cred = rpcauth_lookupcred(auth, 0);

        filp->private_data = cred;
        return 0;
}

int nfs_release(struct inode *inode, struct file *filp)
{
        struct rpc_auth *auth = NFS_CLIENT(inode)->cl_auth;
        struct rpc_cred *cred = nfs_file_cred(filp);

        if (cred)
                rpcauth_releasecred(auth, cred);
        return 0;
}

/*
 * This function is called whenever some part of NFS notices that
 * the cached attributes have to be refreshed.
 */
int
__nfs_revalidate_inode(struct nfs_server *server, struct dentry *dentry)
{
        struct inode    *inode = dentry->d_inode;
        int              status = 0;
        struct nfs_fattr fattr;

        dfprintk(PAGECACHE, "NFS: revalidating %s/%s, ino=%ld\n",
                dentry->d_parent->d_name.name, dentry->d_name.name,
                inode->i_ino);

        if (!inode || is_bad_inode(inode))
                return -ESTALE;

        while (NFS_REVALIDATING(inode)) {
                status = nfs_wait_on_inode(inode, NFS_INO_REVALIDATING);
                if (status < 0)
                        return status;
                if (time_before(jiffies,NFS_READTIME(inode)+NFS_ATTRTIMEO(inode)))
                        return 0;
        }
        NFS_FLAGS(inode) |= NFS_INO_REVALIDATING;

        status = NFS_PROTO(inode)->getattr(dentry, &fattr);
        if (status) {
                struct dentry *dir = dentry->d_parent;
                struct inode *dir_i = dir->d_inode;
                int error;
                u32 *fh;
                struct nfs_fh fhandle;
                dfprintk(PAGECACHE, "nfs_revalidate_inode: %s/%s getattr failed, ino=%ld, error=%d\n",
                         dir->d_name.name, dentry->d_name.name,
                         inode->i_ino, status);
                if (status != -ESTALE)
                        goto out;
                /*
                 * A "stale filehandle" error ... show the current fh
                 * and find out what the filehandle should be.
                 */
                fh = (u32 *) NFS_FH(dentry)->data;
                dfprintk(PAGECACHE, "NFS: bad fh %08x%08x%08x%08x%08x%08x%08x%08x\n",
                        fh[0],fh[1],fh[2],fh[3],fh[4],fh[5],fh[6],fh[7]);
                error = NFS_PROTO(dir_i)->lookup(dir, &dentry->d_name,
                                                 &fhandle, &fattr);
                if (error) {
                        dfprintk(PAGECACHE, "NFS: lookup failed, error=%d\n", error);
                        goto out;
                }
                fh = (u32 *) fhandle.data;
                dfprintk(PAGECACHE, "            %08x%08x%08x%08x%08x%08x%08x%08x\n",
                        fh[0],fh[1],fh[2],fh[3],fh[4],fh[5],fh[6],fh[7]);
                goto out;
        }

        status = nfs_refresh_inode(inode, &fattr);
        if (status) {
                dfprintk(PAGECACHE, "nfs_revalidate_inode: %s/%s refresh failed, ino=%ld, error=%d\n",
                        dentry->d_parent->d_name.name,
                        dentry->d_name.name, inode->i_ino, status);
                goto out;
        }
        dfprintk(PAGECACHE, "NFS: %s/%s revalidation complete\n",
                dentry->d_parent->d_name.name, dentry->d_name.name);
out:
        NFS_FLAGS(inode) &= ~NFS_INO_REVALIDATING;
        wake_up(&inode->i_wait);
        return status;
}

/*
 * Many nfs protocol calls return the new file attributes after
 * an operation.  Here we update the inode to reflect the state
 * of the server's inode.
 *
 * This is a bit tricky because we have to make sure all dirty pages
 * have been sent off to the server before calling invalidate_inode_pages.
 * To make sure no other process adds more write requests while we try
 * our best to flush them, we make them sleep during the attribute refresh.
 *
 * A very similar scenario holds for the dir cache.
 */
int
nfs_refresh_inode(struct inode *inode, struct nfs_fattr *fattr)
{
        __u64           new_size, new_mtime;
        loff_t          new_isize;
        int             invalid = 0;
        int             error = -EIO;

        if (!inode || !fattr) {
                printk(KERN_ERR "nfs_refresh_inode: inode or fattr is NULL\n");
                goto out;
        }
        if (inode->i_mode == 0) {
                printk(KERN_ERR "nfs_refresh_inode: empty inode\n");
                goto out;
        }

        if ((fattr->valid & NFS_ATTR_FATTR) == 0)
                goto out;

        if (is_bad_inode(inode))
                goto out;

        dfprintk(VFS, "NFS: refresh_inode(%x/%ld ct=%d info=0x%x)\n",
                        inode->i_dev, inode->i_ino,
                        atomic_read(&inode->i_count), fattr->valid);


        if (NFS_FSID(inode) != fattr->fsid ||
            NFS_FILEID(inode) != fattr->fileid) {
                printk(KERN_ERR "nfs_refresh_inode: inode number mismatch\n"
                       "expected (0x%Lx/0x%Lx), got (0x%Lx/0x%Lx)\n",
                       (long long)NFS_FSID(inode), (long long)NFS_FILEID(inode),
                       (long long)fattr->fsid, (long long)fattr->fileid);
                goto out;
        }

        /*
         * Make sure the inode's type hasn't changed.
         */
        if ((inode->i_mode & S_IFMT) != (fattr->mode & S_IFMT))
                goto out_changed;

        new_mtime = fattr->mtime;
        new_size = fattr->size;
        new_isize = nfs_size_to_loff_t(fattr->size);

        error = 0;

        /*
         * Update the read time so we don't revalidate too often.
         */
        NFS_READTIME(inode) = jiffies;

        /*
         * Note: NFS_CACHE_ISIZE(inode) reflects the state of the cache.
         *       NOT inode->i_size!!!
         */
        if (NFS_CACHE_ISIZE(inode) != new_size) {
#ifdef NFS_DEBUG_VERBOSE
                printk(KERN_DEBUG "NFS: isize change on %x/%ld\n", inode->i_dev, inode->i_ino);
#endif
                invalid = 1;
        }

        /*
         * Note: we don't check inode->i_mtime since pipes etc.
         *       can change this value in VFS without requiring a
         *       cache revalidation.
         */
        if (NFS_CACHE_MTIME(inode) != new_mtime) {
#ifdef NFS_DEBUG_VERBOSE
                printk(KERN_DEBUG "NFS: mtime change on %x/%ld\n", inode->i_dev, inode->i_ino);
#endif
                invalid = 1;
        }

        /* Check Weak Cache Consistency data.
         * If size and mtime match the pre-operation values, we can
         * assume that any attribute changes were caused by our NFS
         * operation, so there's no need to invalidate the caches.
         */
        if ((fattr->valid & NFS_ATTR_WCC)
            && NFS_CACHE_ISIZE(inode) == fattr->pre_size
            && NFS_CACHE_MTIME(inode) == fattr->pre_mtime) {
                invalid = 0;
        }

        /*
         * If we have pending writebacks, things can get
         * messy.
         */
        if (nfs_have_writebacks(inode) && new_isize < inode->i_size)
                new_isize = inode->i_size;

        NFS_CACHE_CTIME(inode) = fattr->ctime;
        inode->i_ctime = nfs_time_to_secs(fattr->ctime);
        /* If we've been messing around with atime, don't
         * update it. Save the server value in NFS_CACHE_ATIME.
         */
        NFS_CACHE_ATIME(inode) = fattr->atime;
        if (time_before(inode->i_atime, nfs_time_to_secs(fattr->atime)))
                inode->i_atime = nfs_time_to_secs(fattr->atime);

        NFS_CACHE_MTIME(inode) = new_mtime;
        inode->i_mtime = nfs_time_to_secs(new_mtime);

        NFS_CACHE_ISIZE(inode) = new_size;
        inode->i_size = new_isize;

        inode->i_mode = fattr->mode;
        inode->i_nlink = fattr->nlink;
        inode->i_uid = fattr->uid;
        inode->i_gid = fattr->gid;

        if (fattr->valid & NFS_ATTR_FATTR_V3) {
                /*
                 * report the blocks in 512byte units
                 */
                inode->i_blocks = nfs_calc_block_size(fattr->du.nfs3.used);
                inode->i_blksize = inode->i_sb->s_blocksize;
        } else {
                inode->i_blocks = fattr->du.nfs2.blocks;
                inode->i_blksize = fattr->du.nfs2.blocksize;
        }
        inode->i_rdev = 0;
        if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode))
                inode->i_rdev = to_kdev_t(fattr->rdev);
 
        /* Update attrtimeo value */
        if (!invalid && time_after(jiffies, NFS_ATTRTIMEO_UPDATE(inode)+NFS_ATTRTIMEO(inode))) {
                if ((NFS_ATTRTIMEO(inode) <<= 1) > NFS_MAXATTRTIMEO(inode))
                        NFS_ATTRTIMEO(inode) = NFS_MAXATTRTIMEO(inode);
                NFS_ATTRTIMEO_UPDATE(inode) = jiffies;
        }

        if (invalid)
                nfs_zap_caches(inode);

out:
        return error;

out_changed:
        /*
         * Big trouble! The inode has become a different object.
         */
#ifdef NFS_PARANOIA
        printk(KERN_DEBUG "nfs_refresh_inode: inode %ld mode changed, %07o to %07o\n",
               inode->i_ino, inode->i_mode, fattr->mode);
#endif
        /*
         * No need to worry about unhashing the dentry, as the
         * lookup validation will know that the inode is bad.
         * (But we fall through to invalidate the caches.)
         */
        nfs_invalidate_inode(inode);
        goto out;
}

/*
 * File system information
 */
static DECLARE_FSTYPE(nfs_fs_type, "nfs", nfs_read_super, 0);

extern int nfs_init_fhcache(void);
extern void nfs_destroy_fhcache(void);
extern int nfs_init_nfspagecache(void);
extern void nfs_destroy_nfspagecache(void);
extern int nfs_init_readpagecache(void);
extern int nfs_destroy_readpagecache(void);

/*
 * Initialize NFS
 */
int
init_nfs_fs(void)
{
        int err;

        err = nfs_init_fhcache();
        if (err)
                return err;

        err = nfs_init_nfspagecache();
        if (err)
                return err;

        err = nfs_init_readpagecache();
        if (err)
                return err;

#ifdef CONFIG_PROC_FS
        rpc_proc_register(&nfs_rpcstat);
#endif
        return register_filesystem(&nfs_fs_type);
}

/*
 * Every kernel module contains stuff like this.
 */
#ifdef MODULE

EXPORT_NO_SYMBOLS;
/* Not quite true; I just maintain it */
MODULE_AUTHOR("Olaf Kirch <okir@monad.swb.de>");

int
init_module(void)
{
        return init_nfs_fs();
}

void
cleanup_module(void)
{
        nfs_destroy_readpagecache();
        nfs_destroy_nfspagecache();
        nfs_destroy_fhcache();
#ifdef CONFIG_PROC_FS
        rpc_proc_unregister("nfs");
#endif
        unregister_filesystem(&nfs_fs_type);
}
#endif