/*
 * vfs.c - Virtual File System implementation.
 *
 * Author  Mohamed Lamine Karaoui (2015)
 *         Alain Greiner (2016)
 *
 * Copyright (c) UPMC Sorbonne Universites
 *
 * This file is part of ALMOS-MKH.
 *
 * ALMOS-MKH is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2.0 of the License.
 *
 * ALMOS-MKH is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ALMOS-MKH; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */


#include <kernel_config.h>
#include <hal_types.h>
#include <hal_atomic.h>
#include <hal_special.h>
#include <readlock.h>
#include <spinlock.h>
#include <printk.h>
#include <list.h>
#include <xlist.h>
#include <slist.h>
#include <xhtab.h>
#include <rpc.h>
#include <errno.h>
#include <kmem.h>
#include <mapper.h>
#include <thread.h>
#include <process.h>
#include <vfs.h>
#include <fatfs.h>
#include <ramfs.h>
#include <devfs.h>
#include <syscalls.h>


//////////////////////////////////////////////////////////////////////////////////////////
//           Extern variables         
//////////////////////////////////////////////////////////////////////////////////////////

extern vfs_ctx_t   fs_context[FS_TYPES_NR];    // allocated in kernel_init.c

  
//////////////////////////////////////////////////////////////////////////////////////////
//           Context related functions
//////////////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////
void vfs_ctx_init( vfs_fs_type_t   type,
                   uint32_t        attr,
	               uint32_t        total_clusters,
	               uint32_t        cluster_size,
	               xptr_t          vfs_root_xp,
                   void          * extend )
{
    vfs_ctx_t * vfs_ctx = &fs_context[type];

    vfs_ctx->type           = type;
    vfs_ctx->attr           = attr;
    vfs_ctx->total_clusters = total_clusters;
    vfs_ctx->cluster_size   = cluster_size;
    vfs_ctx->vfs_root_xp    = vfs_root_xp;
    vfs_ctx->extend         = extend;

    spinlock_init( &vfs_ctx->lock );

    bitmap_init( vfs_ctx->bitmap , BITMAP_SIZE(CONFIG_VFS_MAX_INODES) ); 
}

////////////////////////////////////////////
error_t vfs_ctx_inum_alloc( vfs_ctx_t * ctx,
                            uint32_t  * inum )
{
    // get lock on inum allocator
    spinlock_lock( &ctx->lock );

    // get lid from local inum allocator
    uint32_t lid = bitmap_ffc( ctx->bitmap , CONFIG_VFS_MAX_INODES );

    if( lid == -1 )   // no more free slot => error
    {
        // release lock
        spinlock_unlock( &ctx->lock );

        // return error
        return 1;
    }
    else              // found => return inum
    {
        // set slot allocated
        bitmap_set( ctx->bitmap , lid );

        // release lock
        spinlock_unlock( &ctx->lock );

        // return inum
        *inum = (((uint32_t)local_cxy) << 16) | (lid & 0xFFFF);
        return 0;
    }
}

////////////////////////////////////////////
void vfs_ctx_inum_release( vfs_ctx_t * ctx,
                           uint32_t    inum )
{
    bitmap_clear( ctx->bitmap , inum & 0xFFFF ); 
}

//////////////////////////////////////////////////////////////////////////////////////////
//           Inode related functions
//////////////////////////////////////////////////////////////////////////////////////////

char * vfs_inode_type_str( uint32_t type )
{
    if     ( type == INODE_TYPE_FILE ) return "FILE";
    else if( type == INODE_TYPE_DIR  ) return "DIR ";
    else if( type == INODE_TYPE_FIFO ) return "FIFO";
    else if( type == INODE_TYPE_PIPE ) return "PIPE";
    else if( type == INODE_TYPE_SOCK ) return "SOCK";
    else if( type == INODE_TYPE_DEV  ) return "DEV ";
    else if( type == INODE_TYPE_SYML ) return "SYML";
    else                               return "undefined";
}

//////////////////////////////////////////////////////
error_t vfs_inode_create( xptr_t            dentry_xp,
                          vfs_fs_type_t     fs_type,
                          vfs_inode_type_t  inode_type,
                          void            * extend,
                          uint32_t          attr,
                          uint32_t          rights,
                          uid_t             uid,
                          gid_t             gid,
                          xptr_t          * inode_xp )
{
    mapper_t         * mapper;     // associated mapper( to be allocated)
    vfs_inode_t      * inode;      // inode descriptor (to be allocated)
    uint32_t           inum;       // inode identifier (to be allocated)
    vfs_ctx_t        * ctx;        // file system context 
	kmem_req_t         req;        // request to kernel memory allocator
    error_t            error;

    // check fs type and get pointer on context
    if     ( fs_type == FS_TYPE_FATFS ) ctx = &fs_context[FS_TYPE_FATFS];
    else if( fs_type == FS_TYPE_RAMFS ) ctx = &fs_context[FS_TYPE_RAMFS];
    else if( fs_type == FS_TYPE_DEVFS ) ctx = &fs_context[FS_TYPE_DEVFS];
    else
    {
        ctx = NULL;
		printk("\n[PANIC] in %s : illegal file system type = %d\n", __FUNCTION__ , fs_type );
        hal_core_sleep();
    }

    // allocate inum
    error = vfs_ctx_inum_alloc( ctx , &inum );

    if( error )
    {
        printk("\n[ERROR] in %s : cannot allocate inum\n", __FUNCTION__ );
        return ENOMEM;
    }

    // allocate memory for mapper
    mapper = mapper_create( fs_type );

    if( mapper == NULL )
    {
        printk("\n[ERROR] in %s : cannot allocate mapper\n", __FUNCTION__ );
        vfs_ctx_inum_release( ctx , inum );
        return ENOMEM;
    }

    // allocate memory for VFS inode descriptor
	req.type  = KMEM_VFS_INODE;
	req.size  = sizeof(vfs_inode_t);
    req.flags = AF_KERNEL | AF_ZERO;
	inode     = (vfs_inode_t *)kmem_alloc( &req );

    if( inode == NULL )
    {
        printk("\n[ERROR] in %s : cannot allocate inode descriptor\n", __FUNCTION__ );
        vfs_ctx_inum_release( ctx , inum );
        mapper_destroy( mapper );
        return ENOMEM;
    }

    // initialize inode descriptor
    inode->gc         = 0;
    inode->type       = inode_type;
    inode->inum       = inum;
    inode->attr       = attr;
    inode->rights     = rights;
    inode->uid        = uid;
    inode->gid        = gid;
    inode->refcount   = 0;
    inode->parent_xp  = dentry_xp;
    inode->ctx        = ctx;
    inode->mapper     = mapper;
    inode->extend     = extend;

    // initialise inode field in mapper
    mapper->inode     = inode;
 
    // initialise threads waiting queue
    xlist_root_init( XPTR( local_cxy , &inode->wait_root ) );

    // initialize dentries hash table
    xhtab_init( &inode->children , XHTAB_DENTRY_TYPE );

    // initialize inode locks 
    remote_rwlock_init( XPTR( local_cxy , &inode->data_lock ) );
    remote_spinlock_init( XPTR( local_cxy , &inode->main_lock ) );

    // return extended pointer on inode
    *inode_xp = XPTR( local_cxy , inode );
    return 0;

}  // end vfs_inode_create()  

/////////////////////////////////////////////
void vfs_inode_destroy( vfs_inode_t * inode )
{
    if( inode->refcount )
    {
        printk("\n[PANIC] in %s : inode refcount non zero\n", __FUNCTION__ );
        hal_core_sleep(); 
    }       

    // release memory allocated for mapper
    mapper_destroy( inode->mapper );

    // release memory allocate for inode descriptor
	kmem_req_t req;
	req.ptr   = inode;
	req.type  = KMEM_VFS_INODE;
	kmem_free( &req );

}  // end vfs_inode_destroy()

/////////////////////////////////////////////
error_t vfs_inode_load( vfs_inode_t * parent,
                        char        * name,
                        xptr_t        child_xp )
{
    vfs_dmsg("\n[INFO] %s : enter for child <%s>\n",
             __FUNCTION__ , name );

    error_t error = 0;

    assert( (parent != NULL) , __FUNCTION__ , "parent pointer is NULL\n");

    assert( (child_xp != XPTR_NULL) , __FUNCTION__ , "child pointer is NULL\n");

    // get parent inode FS type
    vfs_fs_type_t fs_type = parent->ctx->type;

    // call relevant FS function
    if( fs_type == FS_TYPE_FATFS )
    {
        error = fatfs_inode_load( parent , name , child_xp );
    }
    else if( fs_type == FS_TYPE_RAMFS )
    {
        assert( false , __FUNCTION__ , "should not be called for RAMFS\n" );
    }
    else if( fs_type == FS_TYPE_DEVFS )
    {
        assert( false , __FUNCTION__ , "should not be called for DEVFS\n" );
    }
    else
    {
        assert( false , __FUNCTION__ , "undefined file system type\n" );
    }

    vfs_dmsg("\n[INFO] %s : exit for child <%s>\n",
             __FUNCTION__ , name );

    return error;

} // end vfs_load_inode()

////////////////////////////////////////////
void vfs_inode_remote_up( xptr_t  inode_xp )
{
    // get inode cluster and local pointer
    cxy_t         inode_cxy = GET_CXY( inode_xp );
    vfs_inode_t * inode_ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    hal_remote_atomic_add( XPTR( inode_cxy , &inode_ptr->refcount ) , 1 );    
}

//////////////////////////////////////////////
void vfs_inode_remote_down( xptr_t  inode_xp )
{
    // get inode cluster and local pointer
    cxy_t         inode_cxy = GET_CXY( inode_xp );
    vfs_inode_t * inode_ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    hal_remote_atomic_add( XPTR( inode_cxy , &inode_ptr->refcount ) , -1 );    
}

//////////////////////////////////////////////
uint32_t vfs_inode_get_size( xptr_t inode_xp )
{
    // get inode cluster and local pointer
    cxy_t         cxy = GET_CXY( inode_xp );
    vfs_inode_t * ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    // get size
    remote_rwlock_rd_lock( XPTR( cxy , &ptr->data_lock ) );
    uint32_t size = hal_remote_lw( XPTR( cxy , &ptr->size ) );
    remote_rwlock_rd_unlock( XPTR( cxy , &ptr->data_lock ) );
    return size;
}

////////////////////////////////////////////
void vfs_inode_set_size( xptr_t    inode_xp,
                              uint32_t  size )
{
    // get inode cluster and local pointer
    cxy_t         cxy = GET_CXY( inode_xp );
    vfs_inode_t * ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    // set size
    remote_rwlock_wr_unlock( XPTR( cxy , &ptr->data_lock ) );
    hal_remote_sw( XPTR( cxy , &ptr->size ) , size );
    remote_rwlock_wr_unlock( XPTR( cxy , &ptr->data_lock ) );
}

////////////////////////////////////////
void vfs_inode_unlock( xptr_t inode_xp )
{
    // get inode cluster and local pointer
    cxy_t         cxy = GET_CXY( inode_xp );
    vfs_inode_t * ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    // release the main lock
    remote_spinlock_unlock( XPTR( cxy , &ptr->main_lock ) );
}

//////////////////////////////////////
void vfs_inode_lock( xptr_t inode_xp )
{
    // get inode cluster and local pointer
    cxy_t         cxy = GET_CXY( inode_xp );
    vfs_inode_t * ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    // get the main lock
    remote_spinlock_lock( XPTR( cxy , &ptr->main_lock ) );
}

/////////////////////////////////////////
xptr_t vfs_inode_owner( xptr_t inode_xp )
{
    // get inode cluster and local pointer
    cxy_t         cxy = GET_CXY( inode_xp );
    vfs_inode_t * ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    // get the main lock
    return remote_spinlock_owner( XPTR( cxy , &ptr->main_lock ) );
}

/////////////////////////////////////////
void vfs_inode_display( xptr_t inode_xp )
{
    cxy_t          inode_cxy;
    vfs_inode_t  * inode_ptr;
    xptr_t         dentry_xp;
    cxy_t          dentry_cxy;
    vfs_dentry_t * dentry_ptr;
    
    char           name[CONFIG_VFS_MAX_NAME_LENGTH];

    // get inode cluster and local pointer
    inode_cxy = GET_CXY( inode_xp );
    inode_ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    // get parent dentry
    dentry_xp  = hal_remote_lwd( XPTR( inode_cxy , &inode_ptr->parent_xp ) );

    // get local copy of name
    if( dentry_xp == XPTR_NULL )  // it is the VFS root
    {
        strcpy( name , "/" );
    }
    else                          // not the VFS root
    {
        dentry_cxy = GET_CXY( dentry_xp );
        dentry_ptr = (vfs_dentry_t *)GET_PTR( dentry_xp );

        hal_remote_strcpy( XPTR( local_cxy  , name ) , 
                           XPTR( dentry_cxy , &dentry_ptr->name ) );
    }

    // display inode header
    printk("\n*** inode <%s> / inode_xp = %l / dentry_xp = %l ***\n",
           name , inode_xp , dentry_xp );

    // display children from xhtab
    xhtab_display( XPTR( inode_cxy , &inode_ptr->children ) );

}  // end vfs_inode_display()

////////////////////////////////////////////////////////////////////////////////////////////
//           Dentry related functions
//////////////////////////////////////////////////////////////////////////////////////////

///////////////////////////////////////////////////
error_t vfs_dentry_create( vfs_fs_type_t   fs_type,
                           char          * name,
                           vfs_inode_t   * parent,
                           xptr_t        * dentry_xp )
{
    vfs_ctx_t      * ctx;        // context descriptor
    vfs_dentry_t   * dentry;     // dentry descriptor (to be allocated)
	kmem_req_t       req;        // request to kernel memory allocator

    // get pointer on context
    if     ( fs_type == FS_TYPE_FATFS ) ctx = &fs_context[FS_TYPE_FATFS];
    else if( fs_type == FS_TYPE_RAMFS ) ctx = &fs_context[FS_TYPE_RAMFS];
    else if( fs_type == FS_TYPE_DEVFS ) ctx = &fs_context[FS_TYPE_DEVFS];
    else
    {
        ctx = NULL;
        printk("\n[PANIC] in %s : undefined file system type\n", __FUNCTION__ );
        hal_core_sleep();
    }

    // get name length
    uint32_t length = strlen( name );

    if( length >= CONFIG_VFS_MAX_NAME_LENGTH )
    {
        printk("\n[ERROR] in %s : name too long\n", __FUNCTION__ );
        return EINVAL;
    }

    // allocate memory for dentry descriptor
	req.type  = KMEM_VFS_DENTRY;
	req.size  = sizeof(vfs_dentry_t);
    req.flags = AF_KERNEL | AF_ZERO;
	dentry     = (vfs_dentry_t *)kmem_alloc( &req );

    if( dentry == NULL )
    {
        printk("\n[ERROR] in %s : cannot allocate dentry descriptor\n", __FUNCTION__ );
        return ENOMEM;
    }

    // initialize dentry descriptor

    dentry->ctx     = ctx;
    dentry->length  = length;
    dentry->parent  = parent;
    strcpy( dentry->name , name );

    // register dentry in hash table rooted in parent inode
    xhtab_insert( XPTR( local_cxy , &parent->children ),
                  name, 
                  XPTR( local_cxy , &dentry->list ) );

    // return extended pointer on dentry 
    *dentry_xp = XPTR( local_cxy , dentry );

    return 0;

}  // end vfs_dentry_create()

////////////////////////////////////////////////
void vfs_dentry_destroy( vfs_dentry_t * dentry )
{
    if( dentry->refcount )
    {
        printk("\n[PANIC] in %s : dentry refcount non zero\n", __FUNCTION__ );
        hal_core_sleep(); 
    }       

	kmem_req_t req;
	req.ptr   = dentry;
	req.type  = KMEM_VFS_DENTRY;
	kmem_free( &req );
}



//////////////////////////////////////////////////////////////////////////////////////////
//           File descriptor related functions
//////////////////////////////////////////////////////////////////////////////////////////

/////////////////////////////////////////////
error_t vfs_file_create( vfs_inode_t * inode,
                         uint32_t      attr,
                         xptr_t      * file_xp )
{
    vfs_file_t  * file;
	kmem_req_t    req;

    // allocate memory for new file descriptor
	req.type  = KMEM_VFS_FILE;
	req.size  = sizeof(vfs_file_t);
    req.flags = AF_KERNEL | AF_ZERO;
	file      = (vfs_file_t *)kmem_alloc( &req );

    if( file == NULL ) return ENOMEM;

    // initializes new file descriptor
    file->gc       = 0;
    file->type     = inode->type;
    file->attr     = attr;
    file->offset   = 0;
    file->refcount = 0;
    file->inode    = inode;
    file->ctx      = inode->ctx;
    file->mapper   = inode->mapper;

    remote_rwlock_init( XPTR( local_cxy , &file->lock ) );

    *file_xp = XPTR( local_cxy , file );
    return 0;

}  // end vfs_file_create()

///////////////////////////////////////////
void vfs_file_destroy( vfs_file_t *  file )
{
    if( file->refcount )
    {
        printk("\n[PANIC] in %s : file refcount non zero\n", __FUNCTION__ );
        hal_core_sleep(); 
    }       

	kmem_req_t req;
	req.ptr   = file;
	req.type  = KMEM_VFS_FILE;
	kmem_free( &req );

}  // end vfs_file_destroy() 


////////////////////////////////////////
void vfs_file_count_up( xptr_t file_xp )
{
    // get file cluster and local pointer
    cxy_t        file_cxy = GET_CXY( file_xp );
    vfs_file_t * file_ptr = (vfs_file_t *)GET_PTR( file_xp ); 

    // atomically increment count
    hal_remote_atomic_add( XPTR( file_cxy , &file_ptr->refcount ) , 1 ); 
}

//////////////////////////////////////////
void vfs_file_count_down( xptr_t file_xp )
{
    // get file cluster and local pointer
    cxy_t        file_cxy = GET_CXY( file_xp );
    vfs_file_t * file_ptr = (vfs_file_t *)GET_PTR( file_xp ); 

    // atomically decrement count
    hal_remote_atomic_add( XPTR( file_cxy , &file_ptr->refcount ) , -1 ); 
}

//////////////////////////////////////////////////////////////////////////////////////////
//           File access related functions
//////////////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////
error_t vfs_open( xptr_t     cwd_xp,
		          char     * path,
		          uint32_t   flags,
                  uint32_t   mode, 
		          xptr_t   * new_file_xp,
                  uint32_t * new_file_id )
{
    error_t       error;
    xptr_t        inode_xp;     // extended pointer on target inode
    cxy_t         inode_cxy;    // inode cluster identifier       
    vfs_inode_t * inode_ptr;    // inode local pointer
    uint32_t      file_attr;    // file descriptor attributes
    uint32_t      lookup_mode;  // lookup working mode        
    xptr_t        file_xp;      // extended pointer on created file descriptor
    uint32_t      file_id;      // created file descriptor index in reference fd_array

    vfs_dmsg("\n[INFO] %s : enters for <%s> at cycle %d\n",
             __FUNCTION__ , path , (uint32_t)hal_time_stamp() );

    // compute lookup working mode
    lookup_mode = VFS_LOOKUP_OPEN;
    if( (flags & O_DIR    )      )  lookup_mode |= VFS_LOOKUP_DIR;
    if( (flags & O_CREAT  )      )  lookup_mode |= VFS_LOOKUP_CREATE;
    if( (flags & O_EXCL   )      )  lookup_mode |= VFS_LOOKUP_EXCL;
 
    // compute attributes for the created file
    file_attr = 0;
    if( (flags & O_RDONLY ) == 0 )  file_attr |= FD_ATTR_READ_ENABLE;
    if( (flags & O_WRONLY ) == 0 )  file_attr |= FD_ATTR_WRITE_ENABLE;
    if( (flags & O_SYNC   )      )  file_attr |= FD_ATTR_SYNC;
    if( (flags & O_APPEND )      )  file_attr |= FD_ATTR_APPEND;
    if( (flags & O_CLOEXEC)      )  file_attr |= FD_ATTR_CLOSE_EXEC;

    // get extended pointer on target inode
    error = vfs_lookup( cwd_xp , path , lookup_mode , &inode_xp );

    vfs_dmsg("\n[INFO] %s : get inode_xp = %l for <%s> at cycle %d\n",
             __FUNCTION__ , inode_xp , path , hal_get_cycles() );

    if( error ) return error;

    // get target inode cluster and local pointer
    inode_cxy = GET_CXY( inode_xp );
    inode_ptr = (vfs_inode_t *)GET_PTR( inode_xp );
    
    // create a new file descriptor in cluster containing inode
    if( inode_cxy == local_cxy )      // target cluster is local
    {
        error = vfs_file_create( inode_ptr , file_attr , &file_xp );
    }
    else                              // target cluster is remote
    {
        rpc_vfs_file_create_client( inode_cxy , inode_ptr , file_attr , &file_xp , &error );
    }

    if( error )  return error;

    // allocate and register a new file descriptor index in reference cluster fd_array
    error = process_fd_register( file_xp , &file_id );

    if( error ) return error;

    vfs_dmsg("\n[INFO] %s : exit for <%s> / file_id = %d / file_xp = %l / at cycle %d\n",
             __FUNCTION__ , path , file_id , file_xp , hal_get_cycles() );

    // success
    *new_file_xp = file_xp;
    *new_file_id = file_id;
    return 0;

}  // end vfs_open()

/////////////////////////////////////
error_t vfs_move( bool_t   to_buffer,
                  bool_t   is_user,
                  xptr_t   file_xp,
                  void   * buffer,
                  uint32_t size )
{
    assert( ( file_xp != XPTR_NULL ) , __FUNCTION__ , "file_xp == XPTR_NULL" );

    cxy_t              file_cxy;     // remote file descriptor cluster 
    vfs_file_t       * file_ptr;     // remote file descriptor local pointer
    vfs_inode_type_t   inode_type;
    uint32_t           file_offset;  // current offset in file
    mapper_t         * mapper;
    error_t            error;

    // get cluster and local pointer on remote file descriptor
    file_cxy  = GET_CXY( file_xp );
    file_ptr  = (vfs_file_t *)GET_PTR( file_xp );

    // get inode type from remote file descriptor
    inode_type = hal_remote_lw( XPTR( file_cxy , &file_ptr->type   ) );
   
    // action depends on inode type
    if( inode_type == INODE_TYPE_FILE )
    {
        // get mapper pointer and file offset from file descriptor
        file_offset = hal_remote_lw( XPTR( file_cxy , &file_ptr->offset ) );
        mapper = (mapper_t *)hal_remote_lpt( XPTR( file_cxy , &file_ptr->mapper ) );

        // move data between mapper and buffer
        if( file_cxy == local_cxy )
        {
            error = mapper_move_buffer( mapper,
                                        to_buffer,
                                        is_user,
                                        file_offset,
                                        buffer,
                                        size );
        }
        else
        {
            rpc_mapper_move_buffer_client( file_cxy,
                                           mapper,
                                           to_buffer,
                                           is_user,
                                           file_offset,
                                           buffer,
                                           size,
                                           &error );
        } 

        if( error ) return -1;
        else        return size;
    }
    else 
    {
        printk("\n[ERROR] in %s : inode is not a file", __FUNCTION__ );
        return -1;
    }
}  // end vfs_move()

//////////////////////////////////////
error_t vfs_lseek( xptr_t     file_xp,
                   uint32_t   offset,
                   uint32_t   whence, 
                   uint32_t * new_offset )
{
    xptr_t         offset_xp;
    xptr_t         lock_xp;
    cxy_t          file_cxy;
    vfs_file_t  *  file_ptr;
    vfs_inode_t *  inode_ptr;
    uint32_t       new;

    assert( (file_xp != XPTR_NULL) , __FUNCTION__ , "file_xp == XPTR_NULL" );

    // get cluster and local pointer on remote file descriptor
    file_cxy = GET_CXY( file_xp );
    file_ptr = (vfs_file_t *)GET_PTR( file_xp );

    // build extended pointers on lock and offset
    offset_xp = XPTR( file_cxy , &file_ptr->offset );
    lock_xp   = XPTR( file_cxy , &file_ptr->lock );

    // take file descriptor lock
    remote_rwlock_wr_lock( lock_xp );

    if      ( whence == SEEK_CUR )   // new = current + offset
    {
        new = hal_remote_lw( offset_xp ) + offset;
    }
    else if ( whence == SEEK_SET )   // new = offset
    {
        new = offset;
    }
    else if ( whence == SEEK_END )   // new = size + offset
    { 
        // get local pointer on remote inode
        inode_ptr = (vfs_inode_t *)hal_remote_lpt( XPTR( file_cxy , &file_ptr->inode ) );

        new = hal_remote_lw( XPTR( file_cxy , &inode_ptr->size ) ) + offset;
    }
    else
    {
        printk("\n[ERROR] in %s : illegal whence value\n", __FUNCTION__ );
        remote_rwlock_wr_unlock( lock_xp );
        return -1;
    }

    // set new offset
    hal_remote_sw( offset_xp , new );

    // release file descriptor lock
    remote_rwlock_wr_unlock( lock_xp );

    // success
    *new_offset = new;
    return 0;

}  // vfs_lseek()

///////////////////////////////////
error_t vfs_close( xptr_t   file_xp,
                   uint32_t file_id )
{
    assert( (file_xp != XPTR_NULL) , __FUNCTION__ , "file_xp == XPTR_NULL" );

    assert( (file_id < CONFIG_PROCESS_FILE_MAX_NR) , __FUNCTION__ , "illegal file_id" );

    thread_t  * this    = CURRENT_THREAD;
    process_t * process = this->process;

    // get cluster and local pointer on remote file descriptor
    cxy_t        file_cxy = GET_CXY( file_xp );
    vfs_file_t * file_ptr = (vfs_file_t *)GET_PTR( file_xp );

    // get local pointer on local cluster manager
    cluster_t * cluster = LOCAL_CLUSTER;

    // get owner process cluster and lpid
    cxy_t   owner_cxy  = CXY_FROM_PID( process->pid );
    lpid_t  lpid       = LPID_FROM_PID( process->pid );

    // get extended pointers on copies root and lock
    xptr_t root_xp = XPTR( owner_cxy , &cluster->pmgr.copies_root[lpid] );
    xptr_t lock_xp = XPTR( owner_cxy , &cluster->pmgr.copies_lock[lpid] );

    // take the lock protecting the copies
    remote_spinlock_lock( lock_xp );

    // 1) loop on the process descriptor copies to cancel all fd_array[file_id] entries
    xptr_t  iter_xp;
    XLIST_FOREACH( root_xp , iter_xp )
    {
        xptr_t      process_xp  = XLIST_ELEMENT( iter_xp , process_t , copies_list );
        cxy_t       process_cxy = GET_CXY( process_xp );
        process_t * process_ptr = (process_t *)GET_PTR( process_xp );

        xptr_t lock_xp  = XPTR( process_cxy , &process_ptr->fd_array.lock );
        xptr_t entry_xp = XPTR( process_cxy , &process_ptr->fd_array.array[file_id] );

        // lock is required for atomic write of a 64 bits word
        remote_rwlock_wr_lock( lock_xp );
        hal_remote_swd( entry_xp , XPTR_NULL );
        remote_rwlock_wr_unlock( lock_xp );

        hal_fence();
    }    

    // 2) release memory allocated to file descriptor in remote cluster
    if( file_cxy == local_cxy )             // file cluster is local
    {
        vfs_file_destroy( file_ptr );
    }
    else                                    // file cluster is local
    {
        rpc_vfs_file_destroy_client( file_cxy , file_ptr );
    }

    return 0;

}  // end vfs_close()

////////////////////////////////////
error_t vfs_unlink( xptr_t   cwd_xp,
                    char   * path )
{
    printk("\n[PANIC] %s non implemented\n", __FUNCTION__ );
    hal_core_sleep();
    return 0;
}  // vfs_unlink()

///////////////////////////////////////
error_t vfs_stat( xptr_t       file_xp,
                  vfs_stat_t * k_stat )
{
    printk("\n[PANIC] %s non implemented\n", __FUNCTION__ );
    hal_core_sleep();
    return 0;
}

////////////////////////////////////////////
error_t vfs_readdir( xptr_t         file_xp,
                     vfs_dirent_t * k_dirent )
{
    printk("\n[PANIC] %s non implemented\n", __FUNCTION__ );
    hal_core_sleep();
    return 0;
}

//////////////////////////////////////
error_t vfs_mkdir( xptr_t     file_xp,
                   char     * path,
                   uint32_t   mode )
{
    printk("\n[PANIC] %s non implemented\n", __FUNCTION__ );
    hal_core_sleep();
    return 0;
}

////////////////////////////////////
error_t vfs_rmdir( xptr_t   file_xp,
                   char   * path )
{
    printk("\n[PANIC] %s non implemented\n", __FUNCTION__ );
    hal_core_sleep();
    return 0;
}

///////////////////////////////////
error_t vfs_chdir( xptr_t   cwd_xp,
                   char   * path )
{
    error_t           error;
    xptr_t            inode_xp;     // extended pointer on target inode
    cxy_t             inode_cxy;    // target inode cluster identifier       
    vfs_inode_t     * inode_ptr;    // target inode local pointer
    uint32_t          mode;         // lookup working mode        
    vfs_inode_type_t  inode_type;   // target inode type

    // set lookup working mode
    mode = 0;

    // get extended pointer on target inode
    error = vfs_lookup( cwd_xp , path , mode , &inode_xp );

    if( error ) return error;

    // get inode cluster and local pointer
    inode_cxy = GET_CXY( inode_xp );
    inode_ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    // get inode type from remote file
    inode_type = hal_remote_lw( XPTR( inode_cxy , &inode_ptr->type ) );

    if( inode_type != INODE_TYPE_DIR )
    {
        CURRENT_THREAD->errno = ENOTDIR;
        return -1;
    }

    printk("\n[PANIC] %s non fully implemented\n", __FUNCTION__ );
    hal_core_sleep();
    return 0;
}

///////////////////////////////////
error_t vfs_chmod( xptr_t   cwd_xp,
                   char   * path,
                   uint32_t rights )
{
    error_t           error;
    xptr_t            inode_xp;     // extended pointer on target inode
    cxy_t             inode_cxy;    // inode cluster identifier       
    vfs_inode_t     * inode_ptr;    // inode local pointer
    uint32_t          mode;         // lookup working mode
    vfs_inode_type_t  inode_type;   // target inode type

    // set lookup working mode
    mode = 0;
 
    // get extended pointer on target inode
    error = vfs_lookup( cwd_xp , path , mode , &inode_xp );

    if( error ) return error;

    // get inode cluster and local pointer
    inode_cxy = GET_CXY( inode_xp );
    inode_ptr = (vfs_inode_t *)GET_PTR( inode_xp );
    
    // get inode type from remote inode
    inode_type = hal_remote_lw( XPTR( inode_cxy , &inode_ptr->type ) );

    
    printk("\n[PANIC] %s non fully implemented\n", __FUNCTION__ );
    hal_core_sleep();
    return 0;
}

///////////////////////////////////
error_t vfs_mkfifo( xptr_t   cwd_xp,
                    char   * path,
                    uint32_t rights )
{
    printk("\n[PANIC] in %s : not implemented yet\n", __FUNCTION__ );
    hal_core_sleep(); 
    return 0;
}



//////////////////////////////////////////////////////////////////////////////////////////
//            Inode Tree functions
//////////////////////////////////////////////////////////////////////////////////////////

/////////////////////////////////
cxy_t vfs_cluster_random_select()
{
    uint32_t  x_size    = LOCAL_CLUSTER->x_size;
    uint32_t  y_size    = LOCAL_CLUSTER->y_size;
    uint32_t  y_width   = LOCAL_CLUSTER->y_width;
    uint32_t  index     = ( hal_get_cycles() + hal_get_gid() ) % (x_size * y_size);
    uint32_t  x         = index / y_size;    
    uint32_t  y         = index % y_size;

    return (x<<y_width) + y;
}


//////////////////////////////////////////////////////////////////////////
// This static function is called by the vfs_display() function.
//////////////////////////////////////////////////////////////////////////
static void vfs_recursive_display( xptr_t   inode_xp,
                                   xptr_t   name_xp,
                                   xptr_t   dentry_xp,
                                   uint32_t indent )
{
    cxy_t              inode_cxy;
    vfs_inode_t      * inode_ptr;
    vfs_inode_type_t   inode_type;
    xptr_t             children_xp;    // extended pointer on children xhtab

    xptr_t             child_dentry_xp;
    cxy_t              child_dentry_cxy;
    vfs_dentry_t     * child_dentry_ptr;
    xptr_t             child_inode_xp;
    xptr_t             child_dentry_name_xp;

    char               name[CONFIG_VFS_MAX_NAME_LENGTH];

    char *             indent_str[] = { "",                                  // level 0
                                        "  ",                                // level 1
                                        "    ",                              // level 2
                                        "      ",                            // level 3
                                        "        ",                          // level 4
                                        "          ",                        // level 5
                                        "            ",                      // level 6
                                        "              ",                    // level 7
                                        "                ",                  // level 8
                                        "                  ",                // level 9
                                        "                    ",              // level 10
                                        "                      ",            // level 11
                                        "                        ",          // level 12
                                        "                          ",        // level 13
                                        "                            ",      // level 14
                                        "                              " };  // level 15

    assert( (inode_xp != XPTR_NULL) , __FUNCTION__ , "inode_xp cannot be NULL\n" );
    assert( (name_xp  != XPTR_NULL) , __FUNCTION__ , "name_xp cannot be NULL\n" );
    assert( (indent < 16)           , __FUNCTION__ , "depth cannot be larger than 15\n" );
    
    // get inode cluster and local pointer
    inode_cxy = GET_CXY( inode_xp );
    inode_ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    // get inode type
    inode_type = hal_remote_lw( XPTR( inode_cxy , &inode_ptr->type ) );

    // make a local copy of node name
    hal_remote_strcpy( XPTR( local_cxy , name ) , name_xp );

    // display inode
    printk("%s%s <%s> inode_xp = %l / dentry_xp = %l\n",
           indent_str[indent], vfs_inode_type_str( inode_type ), 
           name , inode_xp , dentry_xp );

    // scan directory entries  
    if( inode_type == INODE_TYPE_DIR )
    {
        // get extended pointer on directory entries xhtab
        children_xp =  XPTR( inode_cxy , &inode_ptr->children );

        // get xhtab lock
        xhtab_read_lock( children_xp );

        // get first dentry from xhtab
        child_dentry_xp = xhtab_get_first( children_xp );

        while( child_dentry_xp != XPTR_NULL )
        {
            // get dentry cluster and local pointer
            child_dentry_cxy = GET_CXY( child_dentry_xp );
            child_dentry_ptr = (vfs_dentry_t *)GET_PTR( child_dentry_xp );

            // get extended pointer on child inode
            child_inode_xp = hal_remote_lwd( XPTR( child_dentry_cxy,
                                                   &child_dentry_ptr->child_xp ) );

            // get extended pointer on dentry name
            child_dentry_name_xp = XPTR( child_dentry_cxy , &child_dentry_ptr->name );

            // recursive call on child inode
            vfs_recursive_display( child_inode_xp,
                                   child_dentry_name_xp,
                                   child_dentry_xp,
                                   indent+1 );

            // get next dentry
            child_dentry_xp = xhtab_get_next( children_xp );
        }

        // release xhtab lock
        xhtab_read_unlock( children_xp );
    }
}  // end vfs_recursive_display()

///////////////////////////////////
void vfs_display( xptr_t inode_xp )
{
    xptr_t         name_xp;
    xptr_t         dentry_xp; 
    cxy_t          dentry_cxy;
    vfs_dentry_t * dentry_ptr;

    // get target inode cluster and local pointer 
    cxy_t         inode_cxy = GET_CXY( inode_xp );
    vfs_inode_t * inode_ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    // get extended pointer on associated dentry
    dentry_xp = hal_remote_lwd( XPTR( inode_cxy , &inode_ptr->parent_xp ) );

    // check if target inode is the File System root
    if( dentry_xp == XPTR_NULL )
    {
        // build extended pointer on root name
        name_xp = XPTR( local_cxy , "/" );
    }
    else
    {
        // get dentry cluster and local pointer
        dentry_cxy = GET_CXY( dentry_xp );
        dentry_ptr = (vfs_dentry_t *)GET_PTR( dentry_xp );

        // get extended pointer on dentry name
        name_xp = XPTR( dentry_cxy , &dentry_ptr->name );
    }

    // print header
    printk("\n*** VFS ***\n");

    // call recursive function
    vfs_recursive_display( inode_xp , name_xp , dentry_xp , 0 );

}  // end vfs_display()

//////////////////////////////////////////////////////////////////////////////////////////
// This function is used by the vfs_lookup() function.
// It takes an extended pointer on a remote inode (parent directory inode),
// and check access_rights violation for the calling thread.
// It can be used by any thread running in any cluster.
//////////////////////////////////////////////////////////////////////////////////////////
// @ inode_xp    : extended pointer on inode.
// @ client_uid  : client thread user ID
// @ client_gid  : client thread group ID
// @ return true if access rights are violated.
//////////////////////////////////////////////////////////////////////////////////////////
bool_t vfs_access_denied( xptr_t   inode_xp,
                          uint32_t client_uid,
                          uint32_t client_gid )
{
    // get found inode cluster and local pointer
    cxy_t         inode_cxy = GET_CXY( inode_xp );
    vfs_inode_t * inode_ptr = (vfs_inode_t *)GET_PTR( inode_xp );

    // get inode access mode, UID, and GID
    // TODO uint32_t  mode = hal_remote_lw( XPTR( inode_cxy , &inode_ptr->mode ) );
    uid_t     uid  = hal_remote_lw( XPTR( inode_cxy , &inode_ptr->uid  ) );
    gid_t     gid  = hal_remote_lw( XPTR( inode_cxy , &inode_ptr->gid  ) );

    // FIXME : me must use mode
    if( (uid == client_uid) || (gid == client_gid) ) return false;
    else                                             return true;
}

//////////////////////////////////////////////////////////////////////////////////////////
// This static function is used by the vfs_lookup() function.
// It takes an extended pointer on a remote parent directory inode, a directory 
// entry name, and returns an extended pointer on the child inode. 
// It can be used by any thread running in any cluster.
//////////////////////////////////////////////////////////////////////////////////////////
// @ parent_xp   : extended pointer on parent inode in remote cluster.
// @ name        : dentry name
// @ child_xp    : [out] buffer for extended pointer on child inode.
// @ return true if success / return false if not found.
//////////////////////////////////////////////////////////////////////////////////////////
static bool_t vfs_get_child( xptr_t   parent_xp,
                             char   * name,
                             xptr_t * child_xp )
{
    xptr_t  xhtab_xp;    // extended pointer on hash table containing children dentries
    xptr_t  dentry_xp;   // extended pointer on children dentry

    // get parent inode cluster and local pointer
    cxy_t         parent_cxy = GET_CXY( parent_xp );
    vfs_inode_t * parent_ptr = (vfs_inode_t *)GET_PTR( parent_xp );

    // get extended pointer on hash table of children directory entries
    xhtab_xp = XPTR( parent_cxy , &parent_ptr->children );

    // search extended pointer on matching dentry
    dentry_xp = xhtab_lookup( xhtab_xp , name );

    if( dentry_xp == XPTR_NULL ) return false;

    // get dentry cluster and local pointer
    cxy_t          dentry_cxy = GET_CXY( dentry_xp );
    vfs_dentry_t * dentry_ptr = (vfs_dentry_t *)GET_PTR( dentry_xp );

    // return child inode
    *child_xp = (xptr_t)hal_remote_lwd( XPTR( dentry_cxy , &dentry_ptr->child_xp ) );
    return true;

}  // end vfs_get_child()

//////////////////////////////////////////////////////////////////////////////////////////
// This static function is used by the vfs_lookup() function.
// It takes the <current> pointer on a buffer containing a complete pathname, and return
// in the <name> buffer, allocated by the caller, a single name in the path.
// It return also in the <next> pointer the next character to analyse in the path.
// Finally it returns a <last> boolean, that is true when the returned <name> is the
// last name in the path. The names are supposed to be separated by one or several '/'
// characters, that are not written in  the <name> buffer.
//////////////////////////////////////////////////////////////////////////////////////////
// @ current   : pointer on first character to analyse in buffer containing the path.
// @ name      : [out] pointer on buffer allocated by the caller for the returned name.
// @ next      : [out] pointer on next character to analyse in buffer containing the path.
// @ last      : [out] true if the returned name is the last (NUL character found).
// @ return 0 if success / return EINVAL if string empty (first chracter is NUL).
//////////////////////////////////////////////////////////////////////////////////////////
static error_t vfs_get_name_from_path( char     * current,
                                       char     * name,
                                       char    ** next,
                                       bool_t   * last )
{
    char * ptr = current;

    // skip leading '/' characters
    while( *ptr == '/' ) ptr++;

    // return EINVAL if string empty
    if( *ptr == 0 ) return EINVAL;

    // copy all characters in name until NUL or '/'
    while( (*ptr != 0) && (*ptr !='/') )  *(name++) = *(ptr++);

    // set NUL terminating character in name buffer
    *(name++) = 0;

    // return last an next
    if( *ptr == 0 )             // last found character is NUL => last name in path
    {
        *last = true;
    }
    else                        // last found character is '/' => skip it 
    {
        *last = false;
        *next = ptr + 1;
    }

    return 0;

}  // end vfs_get name_from_path()
   
//////////////////////////////////////////////
error_t vfs_lookup( xptr_t             cwd_xp,
                    char             * pathname,
                    uint32_t           mode,
					xptr_t           * inode_xp )
{
    char               name[CONFIG_VFS_MAX_NAME_LENGTH];   // one name in path 

    xptr_t             parent_xp;    // extended pointer on parent inode
    cxy_t              parent_cxy;   // cluster for parent inode
    vfs_inode_t      * parent_ptr;   // local pointer on parent inode  
    xptr_t             child_xp;     // extended pointer on child inode
    cxy_t              child_cxy;    // cluster for child inode
    vfs_inode_t      * child_ptr;    // local pointer on child inode  
    vfs_inode_type_t   child_type;   // child inode type
    vfs_fs_type_t      fs_type;      // File system type
    vfs_ctx_t        * ctx_ptr;      // local pointer on FS context
    char             * current;      // current pointer on path
    char             * next;         // next value for current pointer   
    bool_t             last;         // true when the name is the last in path
    bool_t             found;        // true when a child has been found
    thread_t         * this;         // pointer on calling thread descriptor
    process_t        * process;      // pointer on calling process descriptor
    error_t            error;

    vfs_dmsg("\n[INFO] %s : enters for <%s> at cycle %d\n",
             __FUNCTION__ , pathname , (uint32_t)hal_time_stamp() );

    this    = CURRENT_THREAD;
    process = this->process;

    // get extended pointer on first inode to search
    if( pathname[0] == '/' ) parent_xp = process->vfs_root_xp;
    else                     parent_xp = cwd_xp;

    // initialise other loop variables
    current  = pathname;
    next     = NULL;
    last     = false;
    child_xp = XPTR_NULL;

    // take lock on parent inode
    vfs_inode_lock( parent_xp );

    // load from device if one intermediate node not found
    // exit while loop when last name found (i.e. last == true)
    do
    {
        // get one name from path, and the "last" flag
        vfs_get_name_from_path( current , name , &next , &last );

        vfs_dmsg("\n[INFO] %s : looking for <%s> / last = %d\n",
                 __FUNCTION__ , name , last );

        // search a child dentry matching name in parent inode
        found = vfs_get_child( parent_xp,
                               name,
                               &child_xp );

        // if a child inode is not found in the inode tree:
        // - we create the missing inode/dentry couple in the inode tree,
        // - we scan the parent mapper to complete the child inode (type and extension),
        // - we return an error if child not found on device.
        // - if the missing child is a directory, we load the child mapper from device

        // for the last name, the behaviour depends on the "mode" argument:

        if (found == false ) // child node not found in inode tree 
        {
            vfs_dmsg("\n[INFO] %s : <%s> not found, try to load it\n",
                     __FUNCTION__ , name );

            // release lock on parent inode
            vfs_inode_unlock( parent_xp );

            // get parent inode FS type
            parent_cxy = GET_CXY( parent_xp );
            parent_ptr = (vfs_inode_t *)GET_PTR( parent_xp );

            ctx_ptr    = (vfs_ctx_t *)hal_remote_lpt( XPTR( parent_cxy ,
                                                            &parent_ptr->ctx ) );
            fs_type    = hal_remote_lw( XPTR( parent_cxy , &ctx_ptr->type ) );

            // select a cluster for missing inode
            child_cxy = vfs_cluster_random_select();
                     
            // insert a new child dentry/inode in parent inode
            error = vfs_add_child_in_parent( child_cxy,
                                             INODE_TYPE_DIR,
                                             fs_type, 
                                             parent_xp, 
                                             name, 
                                             NULL,     // fs_type_specific inode extend
                                             &child_xp );
            if( error )
            {
                printk("\n[ERROR] in %s : no memory for inode %s in path %s\n",
                       __FUNCTION__ , name , pathname );
                return ENOMEM;
            }

            // scan parent mapper to complete the missing inode
            if( parent_cxy == local_cxy )
            {
                error = vfs_inode_load( parent_ptr,
                                        name,
                                        child_xp );
            }
            else
            {
                rpc_vfs_inode_load_client( parent_cxy,
                                           parent_ptr,
                                           name,
                                           child_xp,
                                           &error );
            }

            if ( error )
            {
                printk("\n[ERROR] in %s : node %s not found in path %s\n",
                       __FUNCTION__ , name , pathname );
                return ENOENT;
            }

            // get child inode type
            child_ptr  = (vfs_inode_t *)GET_PTR( child_xp );
            child_type = hal_remote_lw( XPTR( child_cxy , &child_ptr->type ) );

            // load child mapper from device if it is a directory
            if( child_type == INODE_TYPE_DIR )
            {
                if( child_cxy == local_cxy )
                {
                    error = vfs_mapper_load_all( child_ptr );
                }
                else
                {
                    rpc_vfs_mapper_load_all_client( child_cxy,
                                                    child_ptr,
                                                    &error );
                }

                if ( error )
                {
                    printk("\n[ERROR] in %s : cannot access device for node %s in path %s\n",
                           __FUNCTION__ , name , pathname );
                    return EIO;
                }
            }

            // TODO handle lookup mode here [AG]

            // take lock on parent inode
            vfs_inode_lock( parent_xp );
        }

        vfs_dmsg("\n[INFO] %s : found <%s> / parent = %l / child = %l / last = %d\n",
                     __FUNCTION__ , name , parent_xp , child_xp , last );

        // TODO check access rights
        // error = vfs_access_denied( child_xp,
        //                            client_uid,
        //                            client_gid );
        // if( error ) 
        // {
        //     printk("\n[ERROR] in %s : permission denied for %s\n", __FUNCTION__ , name );
        //     return EACCES;
        // }

        // take lock on child inode and release lock on parent
        vfs_inode_lock( child_xp );
        vfs_inode_unlock( parent_xp );

        // update loop variables
        parent_xp = child_xp;
        current   = next;
    }
    while( last == false );

    // release lock 
    vfs_inode_unlock( parent_xp );

    vfs_dmsg("\n[INFO] in %s : exit <%s> found / inode = %l\n",
                 __FUNCTION__ , pathname , child_xp );

    // return searched pointer
    *inode_xp = child_xp;

    return 0;

}  // end vfs_lookup()

////////////////////////////////////////////
error_t vfs_get_path( xptr_t    searched_xp,
                      char    * buffer,
                      uint32_t  max_size )
{
	xptr_t       dentry_xp;   // extended pointer on current dentry
    char       * name;        // local pointer on current dentry name
	uint32_t     length;      // length of current dentry name
	uint32_t     count;       // number of characters written in buffer
	uint32_t     index;       // slot index in buffer
    xptr_t       inode_xp;    // extended pointer on    

    // implementation note:
    // we use two variables "index" and "count" because the buffer
    // is actually written in decreasing index order (from leaf to root) 
    // TODO : handle conflict with a concurrent rename 
    // FIXME : handle synchro in the loop ... [AG]

	// set the NUL character in buffer / initialise buffer index and count
	buffer[max_size - 1] = 0;
	count	 = 1;
    index    = max_size - 2;

    // initialize current inode
    inode_xp  = searched_xp;

    // exit when root inode found (i.e. dentry_xp == XPTR_NULL)
	do
    {
        // get inode cluster and local pointer
        cxy_t         inode_cxy = GET_CXY( inode_xp );
        vfs_inode_t * inode_ptr = (vfs_inode_t *)GET_PTR( inode_xp );

        // get extended pointer on parent dentry		
        dentry_xp = (xptr_t)hal_remote_lwd( XPTR( inode_cxy , inode_ptr->parent_xp ) );

        // get dentry cluster and local pointer
        cxy_t          dentry_cxy = GET_CXY( dentry_xp );
        vfs_dentry_t * dentry_ptr = (vfs_dentry_t *)GET_PTR( dentry_xp );

        // get dentry name length and pointer
        length =  hal_remote_lw( XPTR( dentry_cxy , &dentry_ptr->length ) );
        name   = (char *)hal_remote_lpt( XPTR( dentry_cxy , &dentry_ptr->name ) );

        // update index and count
        index -= (length + 1); 
        count += (length + 1);

        // check buffer overflow
        if( count >= max_size )
        {
            printk("\n[ERROR] in %s : kernel buffer too small\n", __FUNCTION__ );
            return EINVAL;
        }

        // update pathname
        hal_remote_memcpy( XPTR( local_cxy , &buffer[index + 1] ) ,
                           XPTR( dentry_cxy , name ) , length );
		buffer[index] = '/';

		// get extended pointer on next inode
        inode_xp = (xptr_t)hal_remote_lwd( XPTR( dentry_cxy , dentry_ptr->parent ) );
    }
    while( (dentry_xp != XPTR_NULL) );

	return 0;

}  // end vfs_get_path()

      
//////////////////////////////////////////////////////////////
error_t vfs_add_child_in_parent( cxy_t              child_cxy,
                                 vfs_inode_type_t   inode_type,
                                 vfs_fs_type_t      fs_type,
                                 xptr_t             parent_xp,
                                 char             * name,
                                 void             * extend,
                                 xptr_t           * child_xp )
{
    error_t         error;
    xptr_t          dentry_xp;   // extended pointer on created dentry
    xptr_t          inode_xp;    // extended pointer on created inode
    cxy_t           parent_cxy;  // parent inode cluster identifier
    vfs_inode_t   * parent_ptr;  // parent inode local pointer

    // get parent inode cluster and local pointer
    parent_cxy = GET_CXY( parent_xp );
    parent_ptr = (vfs_inode_t *)GET_PTR( parent_xp );

    // 1. create dentry
    if( parent_cxy == local_cxy )      // parent cluster is the local cluster
    {
        error = vfs_dentry_create( fs_type,
                                   name,
                                   parent_ptr,
                                   &dentry_xp );
    }
    else                               // parent cluster is remote
    {
        rpc_vfs_dentry_create_client( parent_cxy,
                                      fs_type,
                                      name,
                                      parent_ptr,
                                      &dentry_xp,
                                      &error );
    }
                                      
    if( error )
    {
        printk("\n[ERROR] in %s : cannot create dentry in cluster %x\n",
               __FUNCTION__ , parent_cxy );
        return ENOMEM;
    }

    // 2. create child inode TODO : define attr / mode / uid / gid
    uint32_t attr = 0;
    uint32_t mode = 0;
    uint32_t uid  = 0;
    uint32_t gid  = 0;
    
    if( child_cxy == local_cxy )      // child cluster is the local cluster
    {
        error = vfs_inode_create( dentry_xp,
                                  fs_type,
                                  inode_type,
                                  extend,
                                  attr,
                                  mode,
                                  uid,
                                  gid,
                                  &inode_xp );
    }
    else                              // child cluster is remote
    {
        rpc_vfs_inode_create_client( child_cxy,
                                     dentry_xp,
                                     fs_type,
                                     inode_type,
                                     extend,
                                     attr,
                                     mode,
                                     uid,
                                     gid,
                                     &inode_xp,
                                     &error );
    }
                                     
    if( error )
    {
        printk("\n[ERROR] in %s : cannot create inode in cluster %x\n",
               __FUNCTION__ , child_cxy );
 
        vfs_dentry_t * dentry = (vfs_dentry_t *)GET_PTR( dentry_xp );
        if( parent_cxy == local_cxy ) vfs_dentry_destroy( dentry );
        else rpc_vfs_dentry_destroy_client( parent_cxy , dentry );
        return ENOMEM;
    }

    // 3. update extended pointer on inode in dentry
    cxy_t          dentry_cxy = GET_CXY( dentry_xp );
    vfs_dentry_t * dentry_ptr = (vfs_dentry_t *)GET_PTR( dentry_xp );
    hal_remote_swd( XPTR( dentry_cxy , &dentry_ptr->child_xp ) , inode_xp );

    // success : return extended pointer on child inode
    *child_xp = inode_xp;
    return 0;

}  // end vfs_add_child_in_parent()

//////////////////////////////////////////////////////////////////////////////////////////
//            Mapper related functions
//////////////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////
error_t vfs_mapper_move_page( page_t * page,
                              bool_t   to_mapper )
{
    error_t error = 0;

    assert( (page != NULL) , __FUNCTION__ , "page pointer is NULL\n" );

    mapper_t    * mapper = page->mapper;


    assert( (mapper != NULL) , __FUNCTION__ , "no mapper for page\n" );

    vfs_dmsg("\n[INFO] %s : enters for page = %d in mapper = %x\n",
             __FUNCTION__ , page->index , mapper );

    // get FS type
    vfs_fs_type_t fs_type = mapper->type;

    // call relevant FS function
    if( fs_type == FS_TYPE_FATFS )
    {
        rwlock_wr_lock( &mapper->lock );
        error = fatfs_mapper_move_page( page , to_mapper ); 
        rwlock_wr_unlock( &mapper->lock );
    }
    else if( fs_type == FS_TYPE_RAMFS )
    {
        assert( false , __FUNCTION__ , "should not be called for RAMFS\n" );
    }
    else if( fs_type == FS_TYPE_DEVFS )
    {
        assert( false , __FUNCTION__ , "should not be called for DEVFS\n" );
    }
    else
    {
        assert( false , __FUNCTION__ , "undefined file system type\n" );
    }

    vfs_dmsg("\n[INFO] %s : exit for page = %d in mapper = %x\n",
             __FUNCTION__ , page->index , mapper );

    return error;

}  // end vfs_move_page()

//////////////////////////////////////////////////
error_t vfs_mapper_load_all( vfs_inode_t * inode )
{
    assert( (inode != NULL) , __FUNCTION__ , "inode pointer is NULL\n" );

    uint32_t   index;
    page_t   * page;

    mapper_t * mapper = inode->mapper;
    uint32_t   size   = inode->size;

    assert( (mapper != NULL) , __FUNCTION__ , "mapper pointer is NULL\n" );

    uint32_t npages = size >> CONFIG_PPM_PAGE_SHIFT;
    if( (size & CONFIG_PPM_PAGE_MASK) || (size == 0) ) npages++;

    // loop on pages 
    for( index = 0 ; index < npages ; index ++ )
    {
        // this function allocates the missing page in mapper,
        // and call the vfs_mapper_move_page() to load the page from device
        page = mapper_get_page( mapper , index );

        if( page == NULL ) return EIO;
    }

    return 0;

}  // end vfs_mapper_load_all()

