source: trunk/kernel/mm/mapper.h @ 606

/*
 * mapper.h - Kernel cache for FS files or directories definition.
 *
 * Authors   Mohamed Lamine Karaoui (2015)
 *           Alain Greiner (2016,2017,2018)
 *
 * 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
 */

#ifndef _MAPPER_H_
#define _MAPPER_H_

#include <hal_kernel_types.h>
#include <hal_atomic.h>
#include <xlist.h>
#include <grdxt.h>
#include <rwlock.h>

/****  Forward declarations ****/

struct page_s;
struct vfs_inode_s;

/*******************************************************************************************
 * The mapper implements the kernel cache for a given file or directory.
 * There is one mapper per file/dir. It is implemented as a three levels radix tree,
 * entirely stored in the same cluster as the inode representing the file/dir.
 * - The fast retrieval key is the page index in the file.
 *   The ix1_width, ix2_width, ix3_width sub-indexes are configuration parameters.
 * - The leaves are pointers on physical page descriptors, dynamically allocated
 *   in the local cluster.
 * - In a given cluster, a mapper is a "private" structure: a thread accessing the mapper
 *   must be running in the cluster containing it (can be a local thread or a RPC thread).
 * - The mapper is protected by a blocking "rwlock", to support several simultaneous
 *   readers, and only one writer. This lock implement a busy waiting policy.
 * - The mapper_get_page() function that return a page descriptor pointer from a page
 *   index in file is in charge of handling the miss on the mapper cache.
 * - The vfs_mapper_move_page() function access the file system to handle a mapper miss,
 *   or update a dirty page on device.
 * - The vfs_mapper_load_all() functions is used to load all pages of a given file 
 *   or directory into the mapper.
 * - the mapper_move_user() function is used to move data to or from an user buffer.
 *   This user space buffer can be physically distributed in several clusters.
 * - the mapper_move_kernel() function is used to move data to or from a remote kernel
 *   buffer, that can be physically located in any cluster.
 * - In the present implementation the cache size for a given file increases on demand,
 *   and the  allocated memory is only released when the mapper/inode is destroyed.
 ******************************************************************************************/


/*******************************************************************************************
 * This structure defines the mapper descriptor.
 ******************************************************************************************/

typedef struct mapper_s
{
        struct vfs_inode_s * inode;           /*! owner inode                                     */
    uint32_t             type;        /*! file system type                                */
        grdxt_t              rt;              /*! embedded pages cache descriptor (radix tree)    */
        remote_rwlock_t      lock;        /*! several readers / only one writer               */
        uint32_t                 refcount;    /*! several vsegs can refer the same file           */
        xlist_entry_t        vsegs_root;  /*! root of list of vsegs refering this mapper      */
        xlist_entry_t        wait_root;   /*! root of list of threads waiting on mapper       */
    list_entry_t         dirty_root;  /*! root of list of dirty pages                     */
}
mapper_t;

/*******************************************************************************************
 * This structure defines a "fragment". It is used to move data between the kernel mapper,
 * and an user buffer, that can be split in several distributed physical pages located
 * in different clusters. A fragment is a set of contiguous bytes in the file.
 * - It can be stored in one single physical page in the user buffer.
 * - It can spread two successive physical pages in the kernel mapper.
 ******************************************************************************************/

typedef struct fragment_s
{
    uint32_t    file_offset;         /*! offset of fragment in file (i.e. in mapper)      */
    uint32_t    size;                /*! number of bytes in fragment                      */
    cxy_t       buf_cxy;             /*! user buffer cluster identifier                   */
    void      * buf_ptr;             /*! local pointer on first byte in user buffer       */
}
fragment_t;

/*******************************************************************************************
 * This function allocates physical memory for a mapper descriptor, and initializes it
 * (refcount <= 0) / inode <= NULL).
 * It must be executed by a thread running in the cluster containing the mapper.
 *******************************************************************************************
 * @ type   : type of the mapper to create.
 * @ return : pointer on created mapper if success / return NULL if no memory
 ******************************************************************************************/
mapper_t * mapper_create( vfs_fs_type_t type );

/*******************************************************************************************
 * This function releases all physical memory allocated for a mapper.
 * Both the mapper descriptor and the radix tree are released.
 * It does NOT synchronize dirty pages. Use the vfs_sync_inode() function if required.
 * It must be executed by a thread running in the cluster containing the mapper.
 *******************************************************************************************
 * @ mapper      : target mapper.
 ******************************************************************************************/
void mapper_destroy( mapper_t * mapper );

/*******************************************************************************************
 * This function load from device a missing page identified by the <page_id> argument
 * into the mapper identified by the <mapper> local pointer.
 * It allocates a physical page from the local cluster, initialise by accessing device,
 * and register the page in the mapper radix tree.
 * It must be executed by a thread running in the cluster containing the mapper.
 * WARNING : the calling function mapper_remote_get_page() is supposed to take and release
 * the lock protecting the mapper in WRITE_MODE.
 *******************************************************************************************
 * @ mapper      : [in]  target mapper.
 * @ page_id : [in]  missing page index in file.
 * @ page_xp : [out] buffer for extended pointer on missing page descriptor.
 * @ return 0 if success / return -1 if a dirty page cannot be updated on device.
 ******************************************************************************************/
error_t mapper_handle_miss( mapper_t * mapper,
                            uint32_t   page_id,
                            xptr_t   * page_xp );

/*******************************************************************************************
 * This function move data between a local mapper, and a distributed user buffer.
 * It must be called by a thread running in cluster containing the mapper.
 * It is called by the vfs_user_move() to implement sys_read() and sys_write() syscalls.
 * If required, the data transfer is split in "fragments", where one fragment contains 
 * contiguous bytes in the same mapper page.
 * It uses "hal_uspace" accesses to move a fragment to/from the user buffer.
 * In case of write, the dirty bit is set for all pages written in the mapper.
 * The mapper being an extendable cache, it is automatically extended when required
 * for both read and write accesses. 
 * The "offset" field in the file descriptor, and the "size" field in inode descriptor
 * are not modified by this function.
 *******************************************************************************************
 * @ mapper       : local pointer on mapper.
 * @ to_buffer    : mapper -> buffer if true / buffer -> mapper if false.
 * @ file_offset  : first byte to move in file.
 * @ u_buf        : user space pointer on user buffer.
 * @ size         : number of bytes to move.
 * returns O if success / returns -1 if error.
 ******************************************************************************************/
error_t mapper_move_user( mapper_t * mapper,
                          bool_t     to_buffer,
                          uint32_t   file_offset,
                          void     * u_buf,
                          uint32_t   size );

/********************************************************************************************
 * This function move data between a remote mapper and a remote kernel buffer. 
 * It can be called by a thread running any cluster. 
 * If required, the data transfer is split in "fragments", where one fragment contains 
 * contiguous bytes in the same mapper page.
 * It uses a "remote_memcpy" to move a fragment to/from the kernel buffer.
 * In case of write, the dirty bit is set for all pages written in the mapper.
 *******************************************************************************************
 * @ mapper_xp    : extended pointer on mapper.
 * @ to_buffer    : mapper -> buffer if true / buffer -> mapper if false.
 * @ file_offset  : first byte to move in file.
 * @ buffer_xp    : extended pointer on kernel buffer.
 * @ size         : number of bytes to move.
 * returns O if success / returns -1 if error.
 ******************************************************************************************/
error_t mapper_move_kernel( xptr_t     mapper_xp,
                            bool_t     to_buffer,
                            uint32_t   file_offset,
                            xptr_t     buffer_xp,
                            uint32_t   size );

/*******************************************************************************************
 * This function removes a physical page from the mapper, and releases
 * the page to the local PPM. It is called by the mapper_destroy() function.
 * It must be executed by a thread running in the cluster containing the mapper.
 * It takes the mapper lock in WRITE_MODE to update the mapper.
 *******************************************************************************************
 * @ mapper     : local pointer on the mapper.
 * @ page       : pointer on page to remove.
 ******************************************************************************************/
void mapper_release_page( mapper_t      * mapper,
                          struct page_s * page );

/*******************************************************************************************
 * This function returns an extended pointer on a mapper page, identified by <page_id>,
 * index in the file. The - possibly remote - mapper is identified by the <mapper_xp>
 * argument.  It can be executed by a thread running in any cluster, as it uses remote
 * access primitives to scan the mapper.
 * In case of miss, this function takes the mapper lock in WRITE_MODE, and call the 
 * mapper_handle_miss() to load the missing page from device to mapper, using an RPC 
 * when the mapper is remote.
 *******************************************************************************************
 * @ mapper_xp  : extended pointer on the mapper.
 * @ page_id    : page index in file
 * @ returns extended pointer on page base if success / return XPTR_NULL if error.
 ******************************************************************************************/
xptr_t mapper_remote_get_page( xptr_t    mapper_xp,
                               uint32_t  page_id );

/*******************************************************************************************
 * This function allows to read a single word in a mapper seen as and array of uint32_t.
 * It has bee designed to support remote access tho the FAT mapper of the FATFS. 
 * It can be called by any thread running in any cluster.
 * In case of miss, it takes the mapper lock in WRITE_MODE, load the missing
 * page from device to mapper, and release the mapper lock.
 *******************************************************************************************
 * @ mapper_xp  : [in]  extended pointer on the mapper.
 * @ index          : [in]  32 bits word index in file.
 * @ p_value    : [out] local pointer on destination buffer.
 * @ returns 0 if success / return -1 if error.
 ******************************************************************************************/
error_t mapper_remote_get_32( xptr_t     mapper_xp,
                              uint32_t   word_id,
                              uint32_t * p_value );

/*******************************************************************************************
 * This function allows to write a single word to a mapper seen as and array of uint32_t.
 * It has bee designed to support remote access tho the FAT mapper of the FATFS. 
 * It can be called by any thread running in any cluster.
 * In case of miss, it takes the mapper lock in WRITE_MODE, load the missing
 * page from device to mapper, and release the mapper lock.
 *******************************************************************************************
 * @ mapper_xp  : [in]  extended pointer on the mapper.
 * @ index          : [in]  32 bits word index in file.
 * @ p_value    : [in]  value to be written.
 * @ returns 0 if success / return -1 if error.
 ******************************************************************************************/
error_t mapper_remote_set_32( xptr_t     mapper_xp,
                              uint32_t   word_id,
                              uint32_t   value );

#endif /* _MAPPER_H_ */