/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

 * Copyright by The HDF Group.                                               *

 * All rights reserved.                                                      *

 *                                                                           *

 * This file is part of HDF5.  The full HDF5 copyright notice, including     *

 * terms governing use, modification, and redistribution, is contained in    *

 * the LICENSE file, which can be found at the root of the source code       *

 * distribution tree, or in https://www.hdfgroup.org/licenses.               *

 * If you do not have access to either file, you may request a copy from     *

 * help@hdfgroup.org.                                                        *

 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*-------------------------------------------------------------------------

 *

 * Created:             H5PB.c

 *

 * Purpose:             Page Buffer routines.

 *

 *-------------------------------------------------------------------------

 */

/****************/

/* Module Setup */

/****************/

#define H5F_FRIEND      /* Suppress error about including H5Fpkg            */

#include "H5PBmodule.h" /* This source code file is part of the H5PB module */

/***********/

/* Headers */

/***********/

#include "H5private.h"   /* Generic Functions                */

#include "H5Eprivate.h"  /* Error handling                   */

#include "H5Fpkg.h"      /* Files                            */

#include "H5FDprivate.h" /* File drivers                     */

#include "H5FLprivate.h" /* Free Lists                               */

#include "H5MMprivate.h" /* Memory management                */

#include "H5PBpkg.h"     /* File access                      */

#include "H5SLprivate.h" /* Skip List                        */

/****************/

/* Local Macros */

/****************/

#define H5PB__PREPEND(page_ptr, head_ptr, tail_ptr, len)                                                     \

    {                                                                                                        \

        if ((head_ptr) == NULL) {                                                                            \

            (head_ptr) = (page_ptr);                                                                         \

            (tail_ptr) = (page_ptr);                                                                         \

        } /* end if */                                                                                       \

        else {                                                                                               \

            (head_ptr)->prev = (page_ptr);                                                                   \

            (page_ptr)->next = (head_ptr);                                                                   \

            (head_ptr)       = (page_ptr);                                                                   \

        } /* end else */                                                                                     \

        (len)++;                                                                                             \

    } /* H5PB__PREPEND() */

#define H5PB__REMOVE(page_ptr, head_ptr, tail_ptr, len)                                                      \

    {                                                                                                        \

        if ((head_ptr) == (page_ptr)) {                                                                      \

            (head_ptr) = (page_ptr)->next;                                                                   \

            if ((head_ptr) != NULL)                                                                          \

                (head_ptr)->prev = NULL;                                                                     \

        } /* end if */                                                                                       \

        else                                                                                                 \

            (page_ptr)->prev->next = (page_ptr)->next;                                                       \

        if ((tail_ptr) == (page_ptr)) {                                                                      \

            (tail_ptr) = (page_ptr)->prev;                                                                   \

            if ((tail_ptr) != NULL)                                                                          \

                (tail_ptr)->next = NULL;                                                                     \

        } /* end if */                                                                                       \

        else                                                                                                 \

            (page_ptr)->next->prev = (page_ptr)->prev;                                                       \

        page_ptr->next = NULL;                                                                               \

        page_ptr->prev = NULL;                                                                               \

        (len)--;                                                                                             \

    }

#define H5PB__INSERT_LRU(page_buf, page_ptr)                                                                 \

    {                                                                                                        \

        assert(page_buf);                                                                                    \

        assert(page_ptr);                                                                                    \

        /* insert the entry at the head of the list. */                                                      \

        H5PB__PREPEND((page_ptr), (page_buf)->LRU_head_ptr, (page_buf)->LRU_tail_ptr,                        \

                      (page_buf)->LRU_list_len)                                                              \

    }

#define H5PB__REMOVE_LRU(page_buf, page_ptr)                                                                 \

    {                                                                                                        \

        assert(page_buf);                                                                                    \

        assert(page_ptr);                                                                                    \

        /* remove the entry from the list. */                                                                \

        H5PB__REMOVE((page_ptr), (page_buf)->LRU_head_ptr, (page_buf)->LRU_tail_ptr,                         \

                     (page_buf)->LRU_list_len)                                                               \

    }

#define H5PB__MOVE_TO_TOP_LRU(page_buf, page_ptr)                                                            \

    {                                                                                                        \

        assert(page_buf);                                                                                    \

        assert(page_ptr);                                                                                    \

        /* Remove entry and insert at the head of the list. */                                               \

        H5PB__REMOVE((page_ptr), (page_buf)->LRU_head_ptr, (page_buf)->LRU_tail_ptr,                         \

                     (page_buf)->LRU_list_len)                                                               \

        H5PB__PREPEND((page_ptr), (page_buf)->LRU_head_ptr, (page_buf)->LRU_tail_ptr,                        \

                      (page_buf)->LRU_list_len)                                                              \

    }

/******************/

/* Local Typedefs */

/******************/

/* Iteration context for destroying page buffer */

typedef struct {

    H5PB_t *page_buf;

    bool    actual_slist;

} H5PB_ud1_t;

/********************/

/* Package Typedefs */

/********************/

/********************/

/* Local Prototypes */

/********************/

static herr_t H5PB__insert_entry(H5PB_t *page_buf, H5PB_entry_t *page_entry);

static htri_t H5PB__make_space(H5F_shared_t *f_sh, H5PB_t *page_buf, H5FD_mem_t inserted_type);

static herr_t H5PB__write_entry(H5F_shared_t *f_sh, H5PB_entry_t *page_entry);

/*********************/

/* Package Variables */

/*********************/

/* Package initialization variable */

bool H5_PKG_INIT_VAR = false;

/*****************************/

/* Library Private Variables */

/*****************************/

/*******************/

/* Local Variables */

/*******************/

/* Declare a free list to manage the H5PB_t struct */

H5FL_DEFINE_STATIC(H5PB_t);

/* Declare a free list to manage the H5PB_entry_t struct */

H5FL_DEFINE_STATIC(H5PB_entry_t);

/*-------------------------------------------------------------------------

 * Function:    H5PB_reset_stats

 *

 * Purpose:     This function was created without documentation.

 *              What follows is my best understanding of Mohamad's intent.

 *

 *              Reset statistics collected for the page buffer layer.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

herr_t

H5PB_reset_stats(H5PB_t *page_buf)

{

    FUNC_ENTER_NOAPI_NOERR

    /* Sanity checks */

    assert(page_buf);

    page_buf->accesses[0]  = 0;

    page_buf->accesses[1]  = 0;

    page_buf->hits[0]      = 0;

    page_buf->hits[1]      = 0;

    page_buf->misses[0]    = 0;

    page_buf->misses[1]    = 0;

    page_buf->evictions[0] = 0;

    page_buf->evictions[1] = 0;

    page_buf->bypasses[0]  = 0;

    page_buf->bypasses[1]  = 0;

    FUNC_LEAVE_NOAPI(SUCCEED)

} /* H5PB_reset_stats() */

/*-------------------------------------------------------------------------

 * Function:    H5PB_get_stats

 *

 * Purpose:     This function was created without documentation.

 *              What follows is my best understanding of Mohamad's intent.

 *

 *              Retrieve statistics collected about page accesses for the page buffer layer.

 *              --accesses: the number of metadata and raw data accesses to the page buffer layer

 *              --hits: the number of metadata and raw data hits in the page buffer layer

 *              --misses: the number of metadata and raw data misses in the page buffer layer

 *              --evictions: the number of metadata and raw data evictions from the page buffer layer

 *              --bypasses: the number of metadata and raw data accesses that bypass the page buffer layer

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

herr_t

H5PB_get_stats(const H5PB_t *page_buf, unsigned accesses[2], unsigned hits[2], unsigned misses[2],

               unsigned evictions[2], unsigned bypasses[2])

{

    FUNC_ENTER_NOAPI_NOERR

    /* Sanity checks */

    assert(page_buf);

    accesses[0]  = page_buf->accesses[0];

    accesses[1]  = page_buf->accesses[1];

    hits[0]      = page_buf->hits[0];

    hits[1]      = page_buf->hits[1];

    misses[0]    = page_buf->misses[0];

    misses[1]    = page_buf->misses[1];

    evictions[0] = page_buf->evictions[0];

    evictions[1] = page_buf->evictions[1];

    bypasses[0]  = page_buf->bypasses[0];

    bypasses[1]  = page_buf->bypasses[1];

    FUNC_LEAVE_NOAPI(SUCCEED)

} /* H5PB_get_stats */

/*-------------------------------------------------------------------------

 * Function:    H5PB_print_stats()

 *

 * Purpose:     This function was created without documentation.

 *              What follows is my best understanding of Mohamad's intent.

 *

 *              Print out statistics collected for the page buffer layer.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

herr_t

H5PB_print_stats(const H5PB_t *page_buf)

{

    FUNC_ENTER_NOAPI_NOINIT_NOERR

    assert(page_buf);

    printf("PAGE BUFFER STATISTICS:\n");

    printf("******* METADATA\n");

    printf("\t Total Accesses: %u\n", page_buf->accesses[0]);

    printf("\t Hits: %u\n", page_buf->hits[0]);

    printf("\t Misses: %u\n", page_buf->misses[0]);

    printf("\t Evictions: %u\n", page_buf->evictions[0]);

    printf("\t Bypasses: %u\n", page_buf->bypasses[0]);

    printf("\t Hit Rate = %f%%\n",

           ((double)page_buf->hits[0] / (page_buf->accesses[0] - page_buf->bypasses[0])) * 100);

    printf("*****************\n\n");

    printf("******* RAWDATA\n");

    printf("\t Total Accesses: %u\n", page_buf->accesses[1]);

    printf("\t Hits: %u\n", page_buf->hits[1]);

    printf("\t Misses: %u\n", page_buf->misses[1]);

    printf("\t Evictions: %u\n", page_buf->evictions[1]);

    printf("\t Bypasses: %u\n", page_buf->bypasses[1]);

    printf("\t Hit Rate = %f%%\n",

           ((double)page_buf->hits[1] / (page_buf->accesses[1] - page_buf->bypasses[0])) * 100);

    printf("*****************\n\n");

    FUNC_LEAVE_NOAPI(SUCCEED)

} /* H5PB_print_stats */

/*-------------------------------------------------------------------------

 * Function:    H5PB_create

 *

 * Purpose:     Create and setup the PB on the file.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

herr_t

H5PB_create(H5F_shared_t *f_sh, size_t size, unsigned page_buf_min_meta_perc, unsigned page_buf_min_raw_perc)

{

    H5PB_t *page_buf  = NULL;

    herr_t  ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_NOAPI(FAIL)

    /* Sanity checks */

    assert(f_sh);

    /* Check args */

    if (f_sh->fs_strategy != H5F_FSPACE_STRATEGY_PAGE)

        HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL,

                    "Enabling Page Buffering requires PAGE file space strategy");

    /* round down the size if it is larger than the page size */

    else if (size > f_sh->fs_page_size) {

        hsize_t temp_size;

        temp_size = (size / f_sh->fs_page_size) * f_sh->fs_page_size;

        H5_CHECKED_ASSIGN(size, size_t, temp_size, hsize_t);

    } /* end if */

    else if (0 != size % f_sh->fs_page_size)

        HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTINIT, FAIL, "Page Buffer size must be >= to the page size");

    /* Allocate the new page buffering structure */

    if (NULL == (page_buf = H5FL_CALLOC(H5PB_t)))

        HGOTO_ERROR(H5E_PAGEBUF, H5E_NOSPACE, FAIL, "memory allocation failed");

    page_buf->max_size = size;

    H5_CHECKED_ASSIGN(page_buf->page_size, size_t, f_sh->fs_page_size, hsize_t);

    page_buf->min_meta_perc = page_buf_min_meta_perc;

    page_buf->min_raw_perc  = page_buf_min_raw_perc;

    /* Calculate the minimum page count for metadata and raw data

     * based on the fractions provided

     */

    page_buf->min_meta_count = (unsigned)((size * page_buf_min_meta_perc) / (f_sh->fs_page_size * 100));

    page_buf->min_raw_count  = (unsigned)((size * page_buf_min_raw_perc) / (f_sh->fs_page_size * 100));

    if (NULL == (page_buf->slist_ptr = H5SL_create(H5SL_TYPE_HADDR, NULL)))

        HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTCREATE, FAIL, "can't create skip list");

    if (NULL == (page_buf->mf_slist_ptr = H5SL_create(H5SL_TYPE_HADDR, NULL)))

        HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTCREATE, FAIL, "can't create skip list");

    if (NULL == (page_buf->page_fac = H5FL_fac_init(page_buf->page_size)))

        HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTINIT, FAIL, "can't create page factory");

    f_sh->page_buf = page_buf;

done:

    if (ret_value < 0) {

        if (page_buf != NULL) {

            if (page_buf->slist_ptr != NULL)

                H5SL_close(page_buf->slist_ptr);

            if (page_buf->mf_slist_ptr != NULL)

                H5SL_close(page_buf->mf_slist_ptr);

            if (page_buf->page_fac != NULL)

                H5FL_fac_term(page_buf->page_fac);

            page_buf = H5FL_FREE(H5PB_t, page_buf);

        } /* end if */

    }     /* end if */

    FUNC_LEAVE_NOAPI(ret_value)

} /* H5PB_create */

/*-------------------------------------------------------------------------

 * Function:    H5PB__flush_cb

 *

 * Purpose:     Callback to flush PB skiplist entries.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

static herr_t

H5PB__flush_cb(void *item, void H5_ATTR_UNUSED *key, void *_op_data)

{

    H5PB_entry_t *page_entry = (H5PB_entry_t *)item; /* Pointer to page entry node */

    H5F_shared_t *f_sh       = (H5F_shared_t *)_op_data;

    herr_t        ret_value  = SUCCEED; /* Return value */

    FUNC_ENTER_PACKAGE

    /* Sanity checks */

    assert(page_entry);

    assert(f_sh);

    /* Flush the page if it's dirty */

    if (page_entry->is_dirty)

        if (H5PB__write_entry(f_sh, page_entry) < 0)

            HGOTO_ERROR(H5E_PAGEBUF, H5E_WRITEERROR, FAIL, "file write failed");

done:

    FUNC_LEAVE_NOAPI(ret_value)

} /* H5PB__flush_cb() */

/*-------------------------------------------------------------------------

 * Function:    H5PB_flush

 *

 * Purpose:     Flush/Free all the PB entries to the file.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

herr_t

H5PB_flush(H5F_shared_t *f_sh)

{

    herr_t ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_NOAPI(FAIL)

    /* Sanity check */

    assert(f_sh);

    /* Flush all the entries in the PB skiplist, if we have write access on the file */

    if (f_sh->page_buf && (H5F_ACC_RDWR & H5F_SHARED_INTENT(f_sh))) {

        H5PB_t *page_buf = f_sh->page_buf;

        /* Iterate over all entries in page buffer skip list */

        if (H5SL_iterate(page_buf->slist_ptr, H5PB__flush_cb, f_sh))

            HGOTO_ERROR(H5E_PAGEBUF, H5E_BADITER, FAIL, "can't flush page buffer skip list");

    } /* end if */

done:

    FUNC_LEAVE_NOAPI(ret_value)

} /* H5PB_flush */

/*-------------------------------------------------------------------------

 * Function:    H5PB__dest_cb

 *

 * Purpose:     Callback to free PB skiplist entries.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

static herr_t

H5PB__dest_cb(void *item, void H5_ATTR_UNUSED *key, void *_op_data)

{

    H5PB_entry_t *page_entry = (H5PB_entry_t *)item; /* Pointer to page entry node */

    H5PB_ud1_t   *op_data    = (H5PB_ud1_t *)_op_data;

    FUNC_ENTER_PACKAGE_NOERR

    /* Sanity checking */

    assert(page_entry);

    assert(op_data);

    assert(op_data->page_buf);

    /* Remove entry from LRU list */

    if (op_data->actual_slist) {

        H5PB__REMOVE_LRU(op_data->page_buf, page_entry)

        page_entry->page_buf_ptr = H5FL_FAC_FREE(op_data->page_buf->page_fac, page_entry->page_buf_ptr);

    } /* end if */

    /* Free page entry */

    page_entry = H5FL_FREE(H5PB_entry_t, page_entry);

    FUNC_LEAVE_NOAPI(SUCCEED)

} /* H5PB__dest_cb() */

/*-------------------------------------------------------------------------

 * Function:    H5PB_dest

 *

 * Purpose:     Flush and destroy the PB on the file if it exists.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

herr_t

H5PB_dest(H5F_shared_t *f_sh)

{

    herr_t ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_NOAPI(FAIL)

    /* Sanity checks */

    assert(f_sh);

    /* flush and destroy the page buffer, if it exists */

    if (f_sh->page_buf) {

        H5PB_t    *page_buf = f_sh->page_buf;

        H5PB_ud1_t op_data; /* Iteration context */

        if (H5PB_flush(f_sh) < 0)

            HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTFLUSH, FAIL, "can't flush page buffer");

        /* Set up context info */

        op_data.page_buf = page_buf;

        /* Destroy the skip list containing all the entries in the PB */

        op_data.actual_slist = true;

        if (H5SL_destroy(page_buf->slist_ptr, H5PB__dest_cb, &op_data))

            HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTCLOSEOBJ, FAIL, "can't destroy page buffer skip list");

        /* Destroy the skip list containing the new entries */

        op_data.actual_slist = false;

        if (H5SL_destroy(page_buf->mf_slist_ptr, H5PB__dest_cb, &op_data))

            HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTCLOSEOBJ, FAIL, "can't destroy page buffer skip list");

        /* Destroy the page factory */

        if (H5FL_fac_term(page_buf->page_fac) < 0)

            HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTRELEASE, FAIL, "can't destroy page buffer page factory");

        f_sh->page_buf = H5FL_FREE(H5PB_t, page_buf);

    } /* end if */

done:

    FUNC_LEAVE_NOAPI(ret_value)

} /* H5PB_dest */

/*-------------------------------------------------------------------------

 * Function:    H5PB_add_new_page

 *

 * Purpose:     Add a new page to the new page skip list. This is called

 *              from the MF layer when a new page is allocated to

 *              indicate to the page buffer layer that a read of the page

 *              from the file is not necessary since it's an empty page.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

herr_t

H5PB_add_new_page(H5F_shared_t *f_sh, H5FD_mem_t type, haddr_t page_addr)

{

    H5PB_t       *page_buf;             /* Page buffer to operate on */

    H5PB_entry_t *page_entry = NULL;    /* Pointer to the corresponding page entry */

    herr_t        ret_value  = SUCCEED; /* Return value */

    FUNC_ENTER_NOAPI(FAIL)

    /* Sanity checks */

    assert(f_sh);

    page_buf = f_sh->page_buf;

    assert(page_buf);

    /* If there is an existing page, this means that at some point the

     * file free space manager freed and re-allocated a page at the same

     * address.  No need to do anything here then...

     */

    /* MSC - to be safe, might want to dig in the MF layer and remove

     * the page when it is freed from this list if it still exists and

     * remove this check

     */

    if (NULL == H5SL_search(page_buf->mf_slist_ptr, &(page_addr))) {

        /* Create the new PB entry */

        if (NULL == (page_entry = H5FL_CALLOC(H5PB_entry_t)))

            HGOTO_ERROR(H5E_PAGEBUF, H5E_NOSPACE, FAIL, "memory allocation failed");

        /* Initialize page fields */

        page_entry->addr     = page_addr;

        page_entry->type     = (H5F_mem_page_t)type;

        page_entry->is_dirty = false;

        /* Insert entry in skip list */

        if (H5SL_insert(page_buf->mf_slist_ptr, page_entry, &(page_entry->addr)) < 0)

            HGOTO_ERROR(H5E_PAGEBUF, H5E_BADVALUE, FAIL, "Can't insert entry in skip list");

    } /* end if */

done:

    if (ret_value < 0)

        if (page_entry)

            page_entry = H5FL_FREE(H5PB_entry_t, page_entry);

    FUNC_LEAVE_NOAPI(ret_value)

} /* H5PB_add_new_page */

/*-------------------------------------------------------------------------

 * Function:    H5PB_update_entry

 *

 * Purpose:     In PHDF5, entries that are written by other processes and just

 *              marked clean by this process have to have their corresponding

 *              pages updated if they exist in the page buffer.

 *              This routine checks and update the pages.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

herr_t

H5PB_update_entry(H5PB_t *page_buf, haddr_t addr, size_t size, const void *buf)

{

    H5PB_entry_t *page_entry; /* Pointer to the corresponding page entry */

    haddr_t       page_addr;

    FUNC_ENTER_NOAPI_NOERR

    /* Sanity checks */

    assert(page_buf);

    assert(size <= page_buf->page_size);

    assert(buf);

    /* calculate the aligned address of the first page */

    page_addr = (addr / page_buf->page_size) * page_buf->page_size;

    /* search for the page and update if found */

    page_entry = (H5PB_entry_t *)H5SL_search(page_buf->slist_ptr, (void *)(&page_addr));

    if (page_entry) {

        haddr_t offset;

        assert(addr + size <= page_addr + page_buf->page_size);

        offset = addr - page_addr;

        H5MM_memcpy((uint8_t *)page_entry->page_buf_ptr + offset, buf, size);

        /* move to top of LRU list */

        H5PB__MOVE_TO_TOP_LRU(page_buf, page_entry)

    } /* end if */

    FUNC_LEAVE_NOAPI(SUCCEED)

} /* H5PB_update_entry */

/*-------------------------------------------------------------------------

 * Function:    H5PB_remove_entry

 *

 * Purpose:     Remove possible metadata entry with ADDR from the PB cache.

 *              This is in response to the data corruption bug from fheap.c

 *              with page buffering + page strategy.

 *              Note: Large metadata page bypasses the PB cache.

 *              Note: Update of raw data page (large or small sized) is handled by the PB cache.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

herr_t

H5PB_remove_entry(const H5F_shared_t *f_sh, haddr_t addr)

{

    H5PB_t       *page_buf;             /* Page buffer to operate on */

    H5PB_entry_t *page_entry = NULL;    /* Pointer to the page entry being searched */

    herr_t        ret_value  = SUCCEED; /* Return value */

    FUNC_ENTER_NOAPI(FAIL)

    /* Sanity checks */

    assert(f_sh);

    page_buf = f_sh->page_buf;

    assert(page_buf);

    /* Search for address in the skip list */

    page_entry = (H5PB_entry_t *)H5SL_search(page_buf->slist_ptr, (void *)(&addr));

    /* If found, remove the entry from the PB cache */

    if (page_entry) {

        assert(page_entry->type != H5F_MEM_PAGE_DRAW);

        if (NULL == H5SL_remove(page_buf->slist_ptr, &(page_entry->addr)))

            HGOTO_ERROR(H5E_CACHE, H5E_BADVALUE, FAIL, "Page Entry is not in skip list");

        /* Remove from LRU list */

        H5PB__REMOVE_LRU(page_buf, page_entry)

        assert(H5SL_count(page_buf->slist_ptr) == page_buf->LRU_list_len);

        page_buf->meta_count--;

        page_entry->page_buf_ptr = H5FL_FAC_FREE(page_buf->page_fac, page_entry->page_buf_ptr);

        page_entry               = H5FL_FREE(H5PB_entry_t, page_entry);

    } /* end if */

done:

    FUNC_LEAVE_NOAPI(ret_value)

} /* H5PB_remove_entry */

/*-------------------------------------------------------------------------

 * Function:    H5PB_read

 *

 * Purpose:     Reads in the data from the page containing it if it exists

 *              in the PB cache; otherwise reads in the page through the VFD.

 *

 * Return:      Non-negative on success/Negative on failure

 *

 *-------------------------------------------------------------------------

 */

herr_t

H5PB_read(H5F_shared_t *f_sh, H5FD_mem_t type, haddr_t addr, size_t size, void *buf /*out*/)

{

    H5PB_t       *page_buf;                        /* Page buffering info for this file */

    H5PB_entry_t *page_entry;                      /* Pointer to the corresponding page entry */

    H5FD_t       *file;                            /* File driver pointer */

    haddr_t       first_page_addr, last_page_addr; /* Addresses of the first and last pages covered by I/O */

    haddr_t       offset;

    haddr_t       search_addr;       /* Address of current page */

    hsize_t       num_touched_pages; /* Number of pages accessed */

    size_t        access_size = 0;

    bool          bypass_pb   = false; /* Whether to bypass page buffering */

    hsize_t       i;                   /* Local index variable */

    herr_t        ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_NOAPI(FAIL)

    /* Sanity checks */

    assert(f_sh);

    assert(type != H5FD_MEM_GHEAP);

    /* Get pointer to page buffer info for this file */

    page_buf = f_sh->page_buf;

#ifdef H5_HAVE_PARALLEL

    if (H5F_SHARED_HAS_FEATURE(f_sh, H5FD_FEAT_HAS_MPI)) {

#if 1

        bypass_pb = true;

#else

        /* MSC - why this stopped working ? */

        int mpi_size;

        if ((mpi_size = H5F_shared_mpi_get_size(f_sh)) < 0)

            HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTGET, FAIL, "can't retrieve MPI communicator size");

        if (1 != mpi_size)

            bypass_pb = true;

#endif

    } /* end if */

#endif

    /* If page buffering is disabled, or the I/O size is larger than that of a

     * single page, or if this is a parallel raw data access, bypass page

     * buffering.

     */

    if (NULL == page_buf || size >= page_buf->page_size || (bypass_pb && H5FD_MEM_DRAW == type)) {

        if (H5F__accum_read(f_sh, type, addr, size, buf) < 0)

            HGOTO_ERROR(H5E_PAGEBUF, H5E_READERROR, FAIL, "read through metadata accumulator failed");

        /* Update statistics */

        if (page_buf) {

            if (type == H5FD_MEM_DRAW)

                page_buf->bypasses[1]++;

            else

                page_buf->bypasses[0]++;

        } /* end if */

        /* If page buffering is disabled, or if this is a large metadata access,

         * or if this is parallel raw data access, we are done here

         */

        if (NULL == page_buf || (size >= page_buf->page_size && H5FD_MEM_DRAW != type) ||

            (bypass_pb && H5FD_MEM_DRAW == type))

            HGOTO_DONE(SUCCEED);

    } /* end if */

    /* Update statistics */

    if (page_buf) {

        if (type == H5FD_MEM_DRAW)

            page_buf->accesses[1]++;

        else

            page_buf->accesses[0]++;

    } /* end if */

    /* Calculate the aligned address of the first page */

    first_page_addr = (addr / page_buf->page_size) * page_buf->page_size;

    /* For Raw data calculate the aligned address of the last page and

     * the number of pages accessed if more than 1 page is accessed

     */

    if (H5FD_MEM_DRAW == type) {

        last_page_addr = ((addr + size - 1) / page_buf->page_size) * page_buf->page_size;

        /* How many pages does this read span */

        num_touched_pages =

            (last_page_addr / page_buf->page_size + 1) - (first_page_addr / page_buf->page_size);

        if (first_page_addr == last_page_addr) {

            assert(1 == num_touched_pages);

            last_page_addr = HADDR_UNDEF;

        } /* end if */

    }     /* end if */

    /* Otherwise set last page addr to HADDR_UNDEF */

    else {

        num_touched_pages = 1;

        last_page_addr    = HADDR_UNDEF;

    } /* end else */

    /* Translate to file driver I/O info object */

    file = f_sh->lf;

    /* Copy raw data from dirty pages into the read buffer if the read

       request spans pages in the page buffer*/

    if (H5FD_MEM_DRAW == type && size >= page_buf->page_size) {

        H5SL_node_t *node;

        /* For each touched page in the page buffer, check if it

         * exists in the page Buffer and is dirty. If it does, we

         * update the buffer with what's in the page so we get the up

         * to date data into the buffer after the big read from the file.

         */

        node = H5SL_find(page_buf->slist_ptr, (void *)(&first_page_addr));

        for (i = 0; i < num_touched_pages; i++) {

            search_addr = i * page_buf->page_size + first_page_addr;

            /* if we still haven't located a starting page, search again */

            if (!node && i != 0)

                node = H5SL_find(page_buf->slist_ptr, (void *)(&search_addr));

            /* if the current page is in the Page Buffer, do the updates */

            if (node) {

                page_entry = (H5PB_entry_t *)H5SL_item(node);

                assert(page_entry);

                /* If the current page address falls out of the access

                   block, then there are no more pages to go over */

                if (page_entry->addr >= addr + size)

                    break;

                assert(page_entry->addr == search_addr);

                if (page_entry->is_dirty) {

                    /* special handling for the first page if it is not a full page access */

                    if (i == 0 && first_page_addr != addr) {

                        offset = addr - first_page_addr;

                        assert(page_buf->page_size > offset);

                        H5MM_memcpy(buf, (uint8_t *)page_entry->page_buf_ptr + offset,

                                    page_buf->page_size - (size_t)offset);

                        /* move to top of LRU list */

                        H5PB__MOVE_TO_TOP_LRU(page_buf, page_entry)

                    } /* end if */

                    /* special handling for the last page if it is not a full page access */

                    else if (num_touched_pages > 1 && i == num_touched_pages - 1 &&

                             search_addr < addr + size) {

                        offset = (num_touched_pages - 2) * page_buf->page_size +

                                 (page_buf->page_size - (addr - first_page_addr));

                        H5MM_memcpy((uint8_t *)buf + offset, page_entry->page_buf_ptr,

                                    (size_t)((addr + size) - last_page_addr));

                        /* move to top of LRU list */

                        H5PB__MOVE_TO_TOP_LRU(page_buf, page_entry)

                    } /* end else-if */

                    /* copy the entire fully accessed pages */

                    else {

                        offset = i * page_buf->page_size;

                        H5MM_memcpy((uint8_t *)buf + (i * page_buf->page_size), page_entry->page_buf_ptr,

                                    page_buf->page_size);

                    } /* end else */

                }     /* end if */

                node = H5SL_next(node);

            } /* end if */

        }     /* end for */

    }         /* end if */

    else {

        /* A raw data access could span 1 or 2 PB entries at this point so

           we need to handle that */

        assert(1 == num_touched_pages || 2 == num_touched_pages);

        for (i = 0; i < num_touched_pages; i++) {

            haddr_t buf_offset;

            /* Calculate the aligned address of the page to search for it in the skip list */

            search_addr = (0 == i ? first_page_addr : last_page_addr);

            /* Calculate the access size if the access spans more than 1 page */

            if (1 == num_touched_pages)

                access_size = size;

            else

                access_size = (0 == i ? (size_t)((first_page_addr + page_buf->page_size) - addr)

                                      : (size - access_size));

            /* Lookup the page in the skip list */

            page_entry = (H5PB_entry_t *)H5SL_search(page_buf->slist_ptr, (void *)(&search_addr));

            /* if found */

            if (page_entry) {

                offset     = (0 == i ? addr - page_entry->addr : 0);

                buf_offset = (0 == i ? 0 : size - access_size);

                /* Account for reads that would overflow a page */

                if (offset + access_size > page_buf->page_size)

                    access_size = page_buf->page_size - offset;

                /* copy the requested data from the page into the input buffer */

                H5MM_memcpy((uint8_t *)buf + buf_offset, (uint8_t *)page_entry->page_buf_ptr + offset,

                            access_size);

                /* Update LRU */

                H5PB__MOVE_TO_TOP_LRU(page_buf, page_entry)

                /* Update statistics */

                if (type == H5FD_MEM_DRAW)

                    page_buf->hits[1]++;

                else

                    page_buf->hits[0]++;

            } /* end if */

            /* if not found */

            else {

                void   *new_page_buf = NULL;

                size_t  page_size    = page_buf->page_size;

                haddr_t eoa;

                /* make space for new entry */

                if ((H5SL_count(page_buf->slist_ptr) * page_buf->page_size) >= page_buf->max_size) {

                    htri_t can_make_space;

                    /* check if we can make space in page buffer */

                    if ((can_make_space = H5PB__make_space(f_sh, page_buf, type)) < 0)

                        HGOTO_ERROR(H5E_PAGEBUF, H5E_NOSPACE, FAIL, "make space in Page buffer Failed");

                    /* if make_space returns 0, then we can't use the page

                       buffer for this I/O and we need to bypass */

                    if (0 == can_make_space) {

                        /* make space can't return false on second touched page since the first is of the same

                         * type */

                        assert(0 == i);

                        /* read entire block from VFD and return */

                        if (H5FD_read(file, type, addr, size, buf) < 0)

                            HGOTO_ERROR(H5E_PAGEBUF, H5E_READERROR, FAIL, "driver read request failed");

                        /* Break out of loop */

                        break;

                    } /* end if */

                }     /* end if */

                /* Read page from VFD */

                if (NULL == (new_page_buf = H5FL_FAC_MALLOC(page_buf->page_fac)))

                    HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTALLOC, FAIL,

                                "memory allocation failed for page buffer entry");

                /* Read page through the VFD layer, but make sure we don't read past the EOA. */

                /* Retrieve the 'eoa' for the file */

                if (HADDR_UNDEF == (eoa = H5F_shared_get_eoa(f_sh, type)))

                    HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTGET, FAIL, "driver get_eoa request failed");

                /* If the entire page falls outside the EOA, then fail */

                if (search_addr > eoa)

                    HGOTO_ERROR(H5E_PAGEBUF, H5E_BADVALUE, FAIL,

                                "reading an entire page that is outside the file EOA");

                /* Adjust the read size to not go beyond the EOA */

                if (search_addr + page_size > eoa)

                    page_size = (size_t)(eoa - search_addr);

                /* Read page from VFD */

                if (H5FD_read(file, type, search_addr, page_size, new_page_buf) < 0)

                    HGOTO_ERROR(H5E_PAGEBUF, H5E_READERROR, FAIL, "driver read request failed");

                /* Copy the requested data from the page into the input buffer */

                offset     = (0 == i ? addr - search_addr : 0);

                buf_offset = (0 == i ? 0 : size - access_size);

                /* Account for reads that would overflow a page */

                if (offset + access_size > page_buf->page_size)

                    access_size = page_buf->page_size - offset;

                H5MM_memcpy((uint8_t *)buf + buf_offset, (uint8_t *)new_page_buf + offset, access_size);

                /* Create the new PB entry */

                if (NULL == (page_entry = H5FL_CALLOC(H5PB_entry_t)))

                    HGOTO_ERROR(H5E_PAGEBUF, H5E_NOSPACE, FAIL, "memory allocation failed");

                page_entry->page_buf_ptr = new_page_buf;

                page_entry->addr         = search_addr;

                page_entry->type         = (H5F_mem_page_t)type;

                page_entry->is_dirty     = false;

                /* Insert page into PB */

                if (H5PB__insert_entry(page_buf, page_entry) < 0)

                    HGOTO_ERROR(H5E_PAGEBUF, H5E_CANTSET, FAIL, "error inserting new page in page buffer");

                /* Update statistics */

                if (type == H5FD_MEM_DRAW)

                    page_buf->misses[1]++;

                else

                    page_buf->misses[0]++;

            } /* end else */

        }     /* end for */

    }         /* end else */

done:

    FUNC_LEAVE_NOAPI(ret_value)

} /* end H5PB_read() */

/*-------------------------------------------------------------------------