Multi Dataset (#2120)

* Fix bug with cross platform compatibility of references within vlens.
No testing yet.

* Merge from multi_rd_wd_coll_io to a more recent branch from develop.
Untested, probably does not work yet.

* Committing clang-format changes

* Committing clang-format changes

* Fix many bugs in multi dataset branch.  Mostly works, some issues in
SWMR tests.

* Committing clang-format changes

* Disable test in swmr.c that was failing due to bug in HDF5 unrelated to
multi dataset.

* Committing clang-format changes

* Fixed fortran multi-dataset tests

* Fixed xlf errors

* Added benchmark code for multi-datasets

* loops over datasets

* added missing error arg.

* Added gnuplot formatting

* Jonathan Kim original MD benchmarking code

* updated MD benchmarking code

* code clean-up

* Only make files in feature test mode

* misc clean-up

* removed TEST_MDSET_NO_LAST_DSET_2ND_PROC option

* Committing clang-format changes

* Change multi dataset API to use arrays of individual parameters instead
of the parameter struct.

* Committing clang-format changes

* Update to new multi dataset Fortran API and tests. (#1724)

* Update to new multi dataset Fortran API and tests.
* Sync Fortran with develop.
* skipping h5pget_mpio_actual_io_mode_f for now

* Fixed issue with dxpl_id, changed to variable size dim. (#1770)

* Remove "is_coll_broken" field from H5D_io_info_t struct

* Committing clang-format changes

* Minor cleanup in multi dataset code.

* Committing clang-format changes

* Clean up in multi dataset code.

* Committing clang-format changes

* Committing clang-format changes

* Fix speeling

* Fix bug in parallel compression. Switch base_maddr in io_info to be a
union.

* Committing clang-format changes

* Implement selection I/O support with multi dataset.  Will be broken in
parallel until PR 1803 is merged to develop then the MDS branch.

* Committing clang-format changes

* Spelling

* Fix bug in multi dataset that could cause errors when only some of the
datasets in the multi dataset I/O used type conversion.

* Committing clang-format changes

* Integrate multi dataset APIs with VOL layer.  Add async versions of
multi dataset APIs.

* Committing clang-format changes

* Spelling fixes

* Fix bug in non-parallel HDF5 compilation.

* Committing clang-format changes

* Fix potential memory/free list error. Minor performance fix. Other minor
changes.

* Committing clang-format changes

* Fix memory leak with memory dataspace for I/O.

* Committing clang-format changes

* Fix stack variables too large.  Rename H5D_dset_info_t to
H5D_dset_io_info_t.

* Committing clang-format changes

* Remove mem_space_alloc field from H5D_dset_io_info_t.  Each function is
now responsible for freeing any spaces it adds to dset_info.

* Committing clang-format changes

* fixed _multi Fortran declaration

* Refactor various things in (mostly) the serial I/O code path to make
things more maintainable.

* Committing clang-format changes

* updated to array based, doxygen, and examples

* Reinstate H5D_chunk_map_t, stored (via pointer) inside
H5D_dset_io_info_t.

* Change from calloc to malloc for H5D_dset_io_info_t and H5D_chunk_map_t.
Switch temporary dset_infos to be local stack variables.

* Committing clang-format changes

* format cleanup

* format cleanup

* added coll and ind

* Modify all parallel I/O paths to take dset_info instead of assuming
dset_info[0].

* Committing clang-format changes

* fixed output

* Rework parallel I/O code to work properly with multi dataset in more
cases.  Fix bug in parallel compression.

* Committing clang-format changes

* Prevent H5D__multi_chunk_collective_io() from messing up collective opt
property for other datasets in I/O.  Other minor cleanup.  Add new test
case to t_pmulti_dset.c for H5FD_MPIO_INDIVIDUAL_IO, disabled for now
due to failures apparently unrelated to multi dataset code.

* Fix spelling

* Committing clang-format changes

* Replace N log N algorithm for finding chunk in
H5D__multi_chunk_collective_io() with O(N) algorithm, and remove use of
io_info->sel_pieces in that function.

* Committing clang-format changes

* Replace sel_pieces skiplist in io_info with flat array of pointers, use
qsort in I/O routine only when necessary.

* Committing clang-format changes

* Add new test case to mdset.c

* Committing clang-format changes

* Fix spelling

* Very minor fix in H5VL__native_dataset_read()

* Fix bug that could affect filtered parallel multi-dataset I/O.

* Add RM entries for H5Dread_multi(), H5Dread_multi_async(),
H5Dwrite_multi(), and H5Dwrite_multi_async()

* Unskip test in swmr.c

* Committing clang-format changes

* Eliminate H5D__pre_read and H5D__pre_write

* Remove examples/ph5mdsettest.c. Will fix and re-add as a test.

* Enable hyperslab combinations in mdset test

* Committing clang-format changes

* Clarify H5Dread/write_multi documentation.

* Fix bugs in multi-dataset I/O.  Expand serial multi dataset test.
Update macro in parallel multi dataset test.

* Committing clang-format changes

* Spelling

* Remove obsolete entry in bin/trace

* Rework type conversion buffer allocation. Only one buffer is shared
between datasets in mdset mode, and it is malloced instead of calloced.

* Committing clang-format changes

* Fix bug in error handling in H5D__read/write

* added multi-dataset fortran check with optional dataset creation id (#2150)

* removed dup. dll entry

* Address comments from code review.

* Remove spurious changes in H5Fmpi.c

* Fix issue with reading unallocated datasets in multi-dataset mode.
Address other comments from code review.

* Committing clang-format changes

* Delay chunk index lookup from io_init to mdio_init so it doesn't add
overhead to single dataset I/O.

* Committing clang-format changes

* Fix inappropriate use of piece_count

* updated copyright on new file, removed benchmark from testing dir.

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: M. Scot Breitenfeld <brtnfld@hdfgroup.org>
Co-authored-by: Dana Robinson <43805+derobins@users.noreply.github.com>

1 files changed, 169 insertions, 154 deletions

diff --git a/src/H5Dpkg.h b/src/H5Dpkg.h
index 0b98ce7..557d745 100644
--- a/src/H5Dpkg.h
+++ b/src/H5Dpkg.h
@@ -33,6 +33,7 @@
 #include "H5ACprivate.h" /* Metadata cache            */
 #include "H5B2private.h" /* v2 B-trees                */
 #include "H5Fprivate.h"  /* File access               */
+#include "H5FLprivate.h" /* Free Lists                */
 #include "H5Gprivate.h"  /* Groups                    */
 #include "H5SLprivate.h" /* Skip lists                */
 #include "H5Tprivate.h"  /* Datatypes                 */
@@ -44,20 +45,6 @@
 /* Set the minimum object header size to create objects with */
 #define H5D_MINHDR_SIZE 256
 
-/* [Simple] Macro to construct a H5D_io_info_t from it's components */
-#define H5D_BUILD_IO_INFO_WRT(io_info, ds, str, buf)                                                         \
-    (io_info)->dset    = ds;                                                                                 \
-    (io_info)->f_sh    = H5F_SHARED((ds)->oloc.file);                                                        \
-    (io_info)->store   = str;                                                                                \
-    (io_info)->op_type = H5D_IO_OP_WRITE;                                                                    \
-    (io_info)->u.wbuf  = buf
-#define H5D_BUILD_IO_INFO_RD(io_info, ds, str, buf)                                                          \
-    (io_info)->dset    = ds;                                                                                 \
-    (io_info)->f_sh    = H5F_SHARED((ds)->oloc.file);                                                        \
-    (io_info)->store   = str;                                                                                \
-    (io_info)->op_type = H5D_IO_OP_READ;                                                                     \
-    (io_info)->u.rbuf  = buf
-
 /* Flags for marking aspects of a dataset dirty */
 #define H5D_MARK_SPACE  0x01
 #define H5D_MARK_LAYOUT 0x02
@@ -83,6 +70,9 @@
 #define H5D_BT2_SPLIT_PERC        100
 #define H5D_BT2_MERGE_PERC        40
 
+/* Macro to determine if the layout I/O callback should perform I/O */
+#define H5D_LAYOUT_CB_PERFORM_IO(IO_INFO) (!(IO_INFO)->use_select_io || (IO_INFO)->count == 1)
+
 /****************************/
 /* Package Private Typedefs */
 /****************************/
@@ -97,23 +87,20 @@ typedef struct H5D_type_info_t {
     hid_t        dst_type_id; /* Destination datatype ID */
 
     /* Computed/derived values */
-    size_t                   src_type_size;  /* Size of source type */
-    size_t                   dst_type_size;  /* Size of destination type */
-    size_t                   max_type_size;  /* Size of largest source/destination type */
-    hbool_t                  is_conv_noop;   /* Whether the type conversion is a NOOP */
-    hbool_t                  is_xform_noop;  /* Whether the data transform is a NOOP */
-    const H5T_subset_info_t *cmpd_subset;    /* Info related to the compound subset conversion functions */
-    H5T_bkg_t                need_bkg;       /* Type of background buf needed */
-    size_t                   request_nelmts; /* Requested strip mine */
-    uint8_t                 *tconv_buf;      /* Datatype conv buffer */
-    hbool_t                  tconv_buf_allocated; /* Whether the type conversion buffer was allocated */
-    uint8_t                 *bkg_buf;             /* Background buffer */
-    hbool_t                  bkg_buf_allocated;   /* Whether the background buffer was allocated */
+    size_t                   src_type_size;     /* Size of source type */
+    size_t                   dst_type_size;     /* Size of destination type */
+    hbool_t                  is_conv_noop;      /* Whether the type conversion is a NOOP */
+    hbool_t                  is_xform_noop;     /* Whether the data transform is a NOOP */
+    const H5T_subset_info_t *cmpd_subset;       /* Info related to the compound subset conversion functions */
+    H5T_bkg_t                need_bkg;          /* Type of background buf needed */
+    size_t                   request_nelmts;    /* Requested strip mine */
+    uint8_t                 *bkg_buf;           /* Background buffer */
+    hbool_t                  bkg_buf_allocated; /* Whether the background buffer was allocated */
 } H5D_type_info_t;
 
 /* Forward declaration of structs used below */
 struct H5D_io_info_t;
-struct H5D_chunk_map_t;
+struct H5D_dset_io_info_t;
 typedef struct H5D_shared_t H5D_shared_t;
 
 /* Function pointers for I/O on particular types of dataset layouts */
@@ -121,27 +108,27 @@ typedef herr_t (*H5D_layout_construct_func_t)(H5F_t *f, H5D_t *dset);
 typedef herr_t (*H5D_layout_init_func_t)(H5F_t *f, const H5D_t *dset, hid_t dapl_id);
 typedef hbool_t (*H5D_layout_is_space_alloc_func_t)(const H5O_storage_t *storage);
 typedef hbool_t (*H5D_layout_is_data_cached_func_t)(const H5D_shared_t *shared_dset);
-typedef herr_t (*H5D_layout_io_init_func_t)(struct H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                            hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space,
-                                            struct H5D_chunk_map_t *cm);
-typedef herr_t (*H5D_layout_read_func_t)(struct H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                         hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space,
-                                         struct H5D_chunk_map_t *fm);
-typedef herr_t (*H5D_layout_write_func_t)(struct H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                          hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space,
-                                          struct H5D_chunk_map_t *fm);
-typedef ssize_t (*H5D_layout_readvv_func_t)(const struct H5D_io_info_t *io_info, size_t dset_max_nseq,
+typedef herr_t (*H5D_layout_io_init_func_t)(struct H5D_io_info_t *io_info, struct H5D_dset_io_info_t *dinfo);
+typedef herr_t (*H5D_layout_mdio_init_func_t)(struct H5D_io_info_t      *io_info,
+                                              struct H5D_dset_io_info_t *dinfo);
+typedef herr_t (*H5D_layout_read_func_t)(struct H5D_io_info_t *io_info, struct H5D_dset_io_info_t *dinfo);
+typedef herr_t (*H5D_layout_write_func_t)(struct H5D_io_info_t *io_info, struct H5D_dset_io_info_t *dinfo);
+typedef herr_t (*H5D_layout_read_md_func_t)(struct H5D_io_info_t *io_info);
+typedef herr_t (*H5D_layout_write_md_func_t)(struct H5D_io_info_t *io_info);
+typedef ssize_t (*H5D_layout_readvv_func_t)(const struct H5D_io_info_t      *io_info,
+                                            const struct H5D_dset_io_info_t *dset_info, size_t dset_max_nseq,
                                             size_t *dset_curr_seq, size_t dset_len_arr[],
                                             hsize_t dset_offset_arr[], size_t mem_max_nseq,
                                             size_t *mem_curr_seq, size_t mem_len_arr[],
                                             hsize_t mem_offset_arr[]);
-typedef ssize_t (*H5D_layout_writevv_func_t)(const struct H5D_io_info_t *io_info, size_t dset_max_nseq,
+typedef ssize_t (*H5D_layout_writevv_func_t)(const struct H5D_io_info_t      *io_info,
+                                             const struct H5D_dset_io_info_t *dset_info, size_t dset_max_nseq,
                                              size_t *dset_curr_seq, size_t dset_len_arr[],
                                              hsize_t dset_offset_arr[], size_t mem_max_nseq,
                                              size_t *mem_curr_seq, size_t mem_len_arr[],
                                              hsize_t mem_offset_arr[]);
 typedef herr_t (*H5D_layout_flush_func_t)(H5D_t *dataset);
-typedef herr_t (*H5D_layout_io_term_func_t)(const struct H5D_chunk_map_t *cm);
+typedef herr_t (*H5D_layout_io_term_func_t)(struct H5D_io_info_t *io_info, struct H5D_dset_io_info_t *di);
 typedef herr_t (*H5D_layout_dest_func_t)(H5D_t *dataset);
 
 /* Typedef for grouping layout I/O routines */
@@ -152,27 +139,28 @@ typedef struct H5D_layout_ops_t {
     H5D_layout_is_data_cached_func_t
         is_data_cached; /* Query routine to determine if any raw data is cached.  If routine is not present
                            then the layout type never caches raw data. */
-    H5D_layout_io_init_func_t io_init;   /* I/O initialization routine */
-    H5D_layout_read_func_t    ser_read;  /* High-level I/O routine for reading data in serial */
-    H5D_layout_write_func_t   ser_write; /* High-level I/O routine for writing data in serial */
-#ifdef H5_HAVE_PARALLEL
-    H5D_layout_read_func_t  par_read;  /* High-level I/O routine for reading data in parallel */
-    H5D_layout_write_func_t par_write; /* High-level I/O routine for writing data in parallel */
-#endif                                 /* H5_HAVE_PARALLEL */
-    H5D_layout_readvv_func_t  readvv;  /* Low-level I/O routine for reading data */
-    H5D_layout_writevv_func_t writevv; /* Low-level I/O routine for writing data */
-    H5D_layout_flush_func_t   flush;   /* Low-level I/O routine for flushing raw data */
-    H5D_layout_io_term_func_t io_term; /* I/O shutdown routine */
-    H5D_layout_dest_func_t    dest;    /* Destroy layout info */
+    H5D_layout_io_init_func_t   io_init;   /* I/O initialization routine */
+    H5D_layout_mdio_init_func_t mdio_init; /* Multi Dataset I/O initialization routine - called after all
+                                              datasets have done io_init and sel_pieces has been allocated */
+    H5D_layout_read_func_t    ser_read;    /* High-level I/O routine for reading data in serial */
+    H5D_layout_write_func_t   ser_write;   /* High-level I/O routine for writing data in serial */
+    H5D_layout_readvv_func_t  readvv;      /* Low-level I/O routine for reading data */
+    H5D_layout_writevv_func_t writevv;     /* Low-level I/O routine for writing data */
+    H5D_layout_flush_func_t   flush;       /* Low-level I/O routine for flushing raw data */
+    H5D_layout_io_term_func_t io_term;     /* I/O shutdown routine for multi-dset */
+    H5D_layout_dest_func_t    dest;        /* Destroy layout info */
 } H5D_layout_ops_t;
 
 /* Function pointers for either multiple or single block I/O access */
-typedef herr_t (*H5D_io_single_read_func_t)(const struct H5D_io_info_t *io_info,
-                                            const H5D_type_info_t *type_info, hsize_t nelmts,
-                                            H5S_t *file_space, H5S_t *mem_space);
-typedef herr_t (*H5D_io_single_write_func_t)(const struct H5D_io_info_t *io_info,
-                                             const H5D_type_info_t *type_info, hsize_t nelmts,
-                                             H5S_t *file_space, H5S_t *mem_space);
+typedef herr_t (*H5D_io_single_read_func_t)(const struct H5D_io_info_t      *io_info,
+                                            const struct H5D_dset_io_info_t *dset_info);
+typedef herr_t (*H5D_io_single_write_func_t)(const struct H5D_io_info_t      *io_info,
+                                             const struct H5D_dset_io_info_t *dset_info);
+
+typedef herr_t (*H5D_io_single_read_md_func_t)(const struct H5D_io_info_t *io_info, hsize_t nelmts,
+                                               H5S_t *file_space, H5S_t *mem_space);
+typedef herr_t (*H5D_io_single_write_md_func_t)(const struct H5D_io_info_t *io_info, hsize_t nelmts,
+                                                H5S_t *file_space, H5S_t *mem_space);
 
 /* Typedef for raw data I/O framework info */
 typedef struct H5D_io_ops_t {
@@ -182,6 +170,14 @@ typedef struct H5D_io_ops_t {
     H5D_io_single_write_func_t single_write; /* I/O routine for writing single block */
 } H5D_io_ops_t;
 
+/* Typedef for raw data I/O framework info (multi-dataset I/O) */
+typedef struct H5D_md_io_ops_t {
+    H5D_layout_read_md_func_t     multi_read_md;  /* High-level I/O routine for reading data for multi-dset */
+    H5D_layout_write_md_func_t    multi_write_md; /* High-level I/O routine for writing data for multi-dset */
+    H5D_io_single_read_md_func_t  single_read_md; /* I/O routine for reading single block for multi-dset */
+    H5D_io_single_write_md_func_t single_write_md; /* I/O routine for writing single block for multi-dset */
+} H5D_md_io_ops_t;
+
 /* Typedefs for dataset storage information */
 typedef struct {
     haddr_t dset_addr; /* Address of dataset in file */
@@ -210,25 +206,79 @@ typedef enum H5D_io_op_type_t {
     H5D_IO_OP_WRITE /* Write operation */
 } H5D_io_op_type_t;
 
+/* Piece info for a data chunk/block during I/O */
+typedef struct H5D_piece_info_t {
+    haddr_t  faddr;                    /* File address */
+    hsize_t  index;                    /* "Index" of chunk in dataset */
+    hsize_t  piece_points;             /* Number of elements selected in piece */
+    hsize_t  scaled[H5O_LAYOUT_NDIMS]; /* Scaled coordinates of chunk (in file dataset's dataspace) */
+    H5S_t   *fspace;                   /* Dataspace describing chunk & selection in it */
+    unsigned fspace_shared; /* Indicate that the file space for a chunk is shared and shouldn't be freed */
+    H5S_t   *mspace;        /* Dataspace describing selection in memory corresponding to this chunk */
+    unsigned mspace_shared; /* Indicate that the memory space for a chunk is shared and shouldn't be freed */
+    struct H5D_dset_io_info_t *dset_info; /* Pointer to dset_info */
+} H5D_piece_info_t;
+
+/* I/O info for a single dataset */
+typedef struct H5D_dset_io_info_t {
+    H5D_t                  *dset;       /* Pointer to dataset being operated on */
+    H5D_storage_t          *store;      /* Dataset storage info */
+    H5D_layout_ops_t        layout_ops; /* Dataset layout I/O operation function pointers */
+    H5_flexible_const_ptr_t buf;        /* Buffer pointer */
+
+    H5D_io_ops_t io_ops; /* I/O operations for this dataset */
+
+    H5O_layout_t *layout; /* Dataset layout information*/
+    hsize_t       nelmts; /* Number of elements selected in file & memory dataspaces */
+
+    H5S_t *file_space; /* Pointer to the file dataspace */
+    H5S_t *mem_space;  /* Pointer to the memory dataspace */
+
+    union {
+        struct H5D_chunk_map_t *chunk_map;         /* Chunk specific I/O info */
+        H5D_piece_info_t       *contig_piece_info; /* Piece info for contiguous dataset */
+    } layout_io_info;
+
+    hid_t           mem_type_id; /* memory datatype ID */
+    H5D_type_info_t type_info;
+    hbool_t         skip_io; /* Whether to skip I/O for this dataset */
+} H5D_dset_io_info_t;
+
+/* I/O info for entire I/O operation */
 typedef struct H5D_io_info_t {
-    const H5D_t *dset;  /* Pointer to dataset being operated on */
-                        /* QAK: Delete the f_sh field when oloc has a shared file pointer? */
+    /* QAK: Delete the f_sh field when oloc has a shared file pointer? */
     H5F_shared_t *f_sh; /* Pointer to shared file struct that dataset is within */
 #ifdef H5_HAVE_PARALLEL
-    MPI_Comm comm;               /* MPI communicator for file */
-    hbool_t  using_mpi_vfd;      /* Whether the file is using an MPI-based VFD */
-#endif                           /* H5_HAVE_PARALLEL */
-    H5D_storage_t   *store;      /* Dataset storage info */
-    H5D_layout_ops_t layout_ops; /* Dataset layout I/O operation function pointers */
-    H5D_io_ops_t     io_ops;     /* I/O operation function pointers */
-    H5D_io_op_type_t op_type;
-    hbool_t          use_select_io; /* Whether to use selection I/O */
-    union {
-        void       *rbuf; /* Pointer to buffer for read */
-        const void *wbuf; /* Pointer to buffer to write */
-    } u;
+    MPI_Comm comm;                     /* MPI communicator for file */
+    hbool_t  using_mpi_vfd;            /* Whether the file is using an MPI-based VFD */
+#endif                                 /* H5_HAVE_PARALLEL */
+    H5D_md_io_ops_t         md_io_ops; /* Multi dataset I/O operation function pointers */
+    H5D_io_op_type_t        op_type;
+    size_t                  count;               /* Number of datasets in I/O request */
+    H5D_dset_io_info_t     *dsets_info;          /* dsets info where I/O is done to/from */
+    size_t                  piece_count;         /* Number of pieces in I/O request */
+    size_t                  pieces_added;        /* Number of pieces added so far to arrays */
+    H5D_piece_info_t      **sel_pieces;          /* Array of info struct for all pieces in I/O */
+    H5S_t                 **mem_spaces;          /* Array of chunk memory spaces */
+    H5S_t                 **file_spaces;         /* Array of chunk file spaces */
+    haddr_t                *addrs;               /* Array of chunk addresses */
+    size_t                 *element_sizes;       /* Array of element sizes */
+    void                  **rbufs;               /* Array of read buffers */
+    const void            **wbufs;               /* Array of write buffers */
+    haddr_t                 store_faddr;         /* lowest file addr for read/write */
+    H5_flexible_const_ptr_t base_maddr;          /* starting mem address */
+    hbool_t                 use_select_io;       /* Whether to use selection I/O */
+    uint8_t                *tconv_buf;           /* Datatype conv buffer */
+    hbool_t                 tconv_buf_allocated; /* Whether the type conversion buffer was allocated */
+    size_t                  max_type_size;       /* Largest of all source and destination type sizes */
 } H5D_io_info_t;
 
+/* Created to pass both at once for callback func */
+typedef struct H5D_io_info_wrap_t {
+    H5D_io_info_t      *io_info;
+    H5D_dset_io_info_t *dinfo;
+} H5D_io_info_wrap_t;
+
 /******************/
 /* Chunk typedefs */
 /******************/
@@ -330,46 +380,26 @@ typedef struct H5D_chunk_ops_t {
     H5D_chunk_dest_func_t  dest;          /* Routine to destroy indexing information in memory */
 } H5D_chunk_ops_t;
 
-/* Structure holding information about a chunk's selection for mapping */
-typedef struct H5D_chunk_info_t {
-    hsize_t  index;                    /* "Index" of chunk in dataset */
-    uint32_t chunk_points;             /* Number of elements selected in chunk */
-    hsize_t  scaled[H5O_LAYOUT_NDIMS]; /* Scaled coordinates of chunk (in file dataset's dataspace) */
-    H5S_t   *fspace;                   /* Dataspace describing chunk & selection in it */
-    hbool_t  fspace_shared; /* Indicate that the file space for a chunk is shared and shouldn't be freed */
-    H5S_t   *mspace;        /* Dataspace describing selection in memory corresponding to this chunk */
-    hbool_t  mspace_shared; /* Indicate that the memory space for a chunk is shared and shouldn't be freed */
-} H5D_chunk_info_t;
-
 /* Main structure holding the mapping between file chunks and memory */
 typedef struct H5D_chunk_map_t {
-    H5O_layout_t *layout; /* Dataset layout information*/
-    hsize_t       nelmts; /* Number of elements selected in file & memory dataspaces */
+    unsigned f_ndims; /* Number of dimensions for file dataspace */
 
-    H5S_t   *file_space; /* Pointer to the file dataspace */
-    unsigned f_ndims;    /* Number of dimensions for file dataspace */
-
-    H5S_t         *mem_space;   /* Pointer to the memory dataspace */
     H5S_t         *mchunk_tmpl; /* Dataspace template for new memory chunks */
     H5S_sel_iter_t mem_iter;    /* Iterator for elements in memory selection */
     unsigned       m_ndims;     /* Number of dimensions for memory dataspace */
     H5S_sel_type   msel_type;   /* Selection type in memory */
     H5S_sel_type   fsel_type;   /* Selection type in file */
 
-    H5SL_t *sel_chunks; /* Skip list containing information for each chunk selected */
+    H5SL_t *dset_sel_pieces; /* Skip list containing information for each chunk selected */
 
     H5S_t            *single_space;      /* Dataspace for single chunk */
-    H5D_chunk_info_t *single_chunk_info; /* Pointer to single chunk's info */
+    H5D_piece_info_t *single_piece_info; /* Pointer to single chunk's info */
     hbool_t           use_single;        /* Whether I/O is on a single element */
 
     hsize_t           last_index;      /* Index of last chunk operated on */
-    H5D_chunk_info_t *last_chunk_info; /* Pointer to last chunk's info */
+    H5D_piece_info_t *last_piece_info; /* Pointer to last chunk's info */
 
     hsize_t chunk_dim[H5O_LAYOUT_NDIMS]; /* Size of chunk in each dimension */
-
-#ifdef H5_HAVE_PARALLEL
-    H5D_chunk_info_t **select_chunk; /* Store the information about whether this chunk is selected or not */
-#endif                               /* H5_HAVE_PARALLEL */
 } H5D_chunk_map_t;
 
 /* Cached information about a particular chunk */
@@ -415,7 +445,7 @@ typedef struct H5D_rdcc_t {
     struct H5D_rdcc_ent_t **slot;              /* Chunk slots, each points to a chunk*/
     H5SL_t                 *sel_chunks;        /* Skip list containing information for each chunk selected */
     H5S_t                  *single_space;      /* Dataspace for single element I/O on chunks */
-    H5D_chunk_info_t       *single_chunk_info; /* Pointer to single chunk's info */
+    H5D_piece_info_t       *single_piece_info; /* Pointer to single piece's info */
 
     /* Cached information about scaled dataspace dimensions */
     hsize_t  scaled_dims[H5S_MAX_RANK];        /* The scaled dim sizes */
@@ -458,12 +488,13 @@ struct H5D_shared_t {
 
     /* Buffered/cached information for types of raw data storage*/
     struct {
-        H5D_rdcdc_t contig; /* Information about contiguous data */
-                            /* (Note that the "contig" cache
-                             * information can be used by a chunked
-                             * dataset in certain circumstances)
-                             */
-        H5D_rdcc_t chunk;   /* Information about chunked data */
+        H5D_rdcdc_t contig;    /* Information about contiguous data */
+                               /* (Note that the "contig" cache
+                                * information can be used by a chunked
+                                * dataset in certain circumstances)
+                                */
+        H5D_rdcc_t chunk;      /* Information about chunked data */
+        H5SL_t    *sel_pieces; /* Skip list containing information for each piece selected */
     } cache;
 
     H5D_append_flush_t append_flush;   /* Append flush property information */
@@ -556,8 +587,8 @@ H5_DLL H5D_t  *H5D__open_name(const H5G_loc_t *loc, const char *name, hid_t dapl
 H5_DLL hid_t   H5D__get_space(const H5D_t *dset);
 H5_DLL hid_t   H5D__get_type(const H5D_t *dset);
 H5_DLL herr_t  H5D__get_space_status(const H5D_t *dset, H5D_space_status_t *allocation);
-H5_DLL herr_t  H5D__alloc_storage(const H5D_io_info_t *io_info, H5D_time_alloc_t time_alloc,
-                                  hbool_t full_overwrite, hsize_t old_dim[]);
+H5_DLL herr_t  H5D__alloc_storage(H5D_t *dset, H5D_time_alloc_t time_alloc, hbool_t full_overwrite,
+                                  hsize_t old_dim[]);
 H5_DLL herr_t  H5D__get_storage_size(const H5D_t *dset, hsize_t *storage_size);
 H5_DLL herr_t  H5D__get_chunk_storage_size(H5D_t *dset, const hsize_t *offset, hsize_t *storage_size);
 H5_DLL herr_t  H5D__chunk_index_empty(const H5D_t *dset, hbool_t *empty);
@@ -582,16 +613,12 @@ H5_DLL herr_t  H5D__refresh(H5D_t *dataset, hid_t dset_id);
 H5_DLL herr_t H5D__format_convert(H5D_t *dataset);
 
 /* Internal I/O routines */
-H5_DLL herr_t H5D__read(H5D_t *dataset, hid_t mem_type_id, H5S_t *mem_space, H5S_t *file_space,
-                        void *buf /*out*/);
-H5_DLL herr_t H5D__write(H5D_t *dataset, hid_t mem_type_id, H5S_t *mem_space, H5S_t *file_space,
-                         const void *buf);
+H5_DLL herr_t H5D__read(size_t count, H5D_dset_io_info_t *dset_info);
+H5_DLL herr_t H5D__write(size_t count, H5D_dset_io_info_t *dset_info);
 
 /* Functions that perform direct serial I/O operations */
-H5_DLL herr_t H5D__select_read(const H5D_io_info_t *io_info, const H5D_type_info_t *type_info, hsize_t nelmts,
-                               H5S_t *file_space, H5S_t *mem_space);
-H5_DLL herr_t H5D__select_write(const H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space);
+H5_DLL herr_t H5D__select_read(const H5D_io_info_t *io_info, const H5D_dset_io_info_t *dset_info);
+H5_DLL herr_t H5D__select_write(const H5D_io_info_t *io_info, const H5D_dset_io_info_t *dset_info);
 
 /* Functions that perform direct copying between memory buffers */
 H5_DLL herr_t H5D_select_io_mem(void *dst_buf, H5S_t *dst_space, const void *src_buf, H5S_t *src_space,
@@ -601,10 +628,8 @@ H5_DLL herr_t H5D_select_io_mem(void *dst_buf, H5S_t *dst_space, const void *src
 H5_DLL herr_t H5D__scatter_mem(const void *_tscat_buf, H5S_sel_iter_t *iter, size_t nelmts, void *_buf);
 H5_DLL size_t H5D__gather_mem(const void *_buf, H5S_sel_iter_t *iter, size_t nelmts,
                               void *_tgath_buf /*out*/);
-H5_DLL herr_t H5D__scatgath_read(const H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                 hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space);
-H5_DLL herr_t H5D__scatgath_write(const H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                  hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space);
+H5_DLL herr_t H5D__scatgath_read(const H5D_io_info_t *io_info, const H5D_dset_io_info_t *dset_info);
+H5_DLL herr_t H5D__scatgath_write(const H5D_io_info_t *io_info, const H5D_dset_io_info_t *dset_info);
 
 /* Functions that operate on dataset's layout information */
 H5_DLL herr_t H5D__layout_set_io_ops(const H5D_t *dataset);
@@ -620,25 +645,23 @@ H5_DLL herr_t H5D__layout_oh_write(const H5D_t *dataset, H5O_t *oh, unsigned upd
 H5_DLL herr_t  H5D__contig_alloc(H5F_t *f, H5O_storage_contig_t *storage);
 H5_DLL hbool_t H5D__contig_is_space_alloc(const H5O_storage_t *storage);
 H5_DLL hbool_t H5D__contig_is_data_cached(const H5D_shared_t *shared_dset);
-H5_DLL herr_t  H5D__contig_fill(const H5D_io_info_t *io_info);
-H5_DLL herr_t  H5D__contig_read(H5D_io_info_t *io_info, const H5D_type_info_t *type_info, hsize_t nelmts,
-                                H5S_t *file_space, H5S_t *mem_space, H5D_chunk_map_t *fm);
-H5_DLL herr_t  H5D__contig_write(H5D_io_info_t *io_info, const H5D_type_info_t *type_info, hsize_t nelmts,
-                                 H5S_t *file_space, H5S_t *mem_space, H5D_chunk_map_t *fm);
+H5_DLL herr_t  H5D__contig_fill(H5D_t *dset);
+H5_DLL herr_t  H5D__contig_read(H5D_io_info_t *io_info, H5D_dset_io_info_t *dinfo);
+H5_DLL herr_t  H5D__contig_write(H5D_io_info_t *io_info, H5D_dset_io_info_t *dinfo);
 H5_DLL herr_t  H5D__contig_copy(H5F_t *f_src, const H5O_storage_contig_t *storage_src, H5F_t *f_dst,
                                 H5O_storage_contig_t *storage_dst, H5T_t *src_dtype, H5O_copy_t *cpy_info);
 H5_DLL herr_t  H5D__contig_delete(H5F_t *f, const H5O_storage_t *store);
 
 /* Functions that operate on chunked dataset storage */
-H5_DLL htri_t  H5D__chunk_cacheable(const H5D_io_info_t *io_info, haddr_t caddr, hbool_t write_op);
-H5_DLL herr_t  H5D__chunk_create(const H5D_t *dset /*in,out*/);
-H5_DLL herr_t  H5D__chunk_set_info(const H5D_t *dset);
+H5_DLL htri_t H5D__chunk_cacheable(const H5D_io_info_t *io_info, H5D_dset_io_info_t *dset_info, haddr_t caddr,
+                                   hbool_t write_op);
+H5_DLL herr_t H5D__chunk_create(const H5D_t *dset /*in,out*/);
+H5_DLL herr_t H5D__chunk_set_info(const H5D_t *dset);
 H5_DLL hbool_t H5D__chunk_is_space_alloc(const H5O_storage_t *storage);
 H5_DLL hbool_t H5D__chunk_is_data_cached(const H5D_shared_t *shared_dset);
 H5_DLL herr_t  H5D__chunk_lookup(const H5D_t *dset, const hsize_t *scaled, H5D_chunk_ud_t *udata);
 H5_DLL herr_t  H5D__chunk_allocated(const H5D_t *dset, hsize_t *nbytes);
-H5_DLL herr_t  H5D__chunk_allocate(const H5D_io_info_t *io_info, hbool_t full_overwrite,
-                                   const hsize_t old_dim[]);
+H5_DLL herr_t  H5D__chunk_allocate(const H5D_t *dset, hbool_t full_overwrite, const hsize_t old_dim[]);
 H5_DLL herr_t  H5D__chunk_file_alloc(const H5D_chk_idx_info_t *idx_info, const H5F_block_t *old_chunk,
                                      H5F_block_t *new_chunk, hbool_t *need_insert, const hsize_t *scaled);
 H5_DLL void   *H5D__chunk_mem_alloc(size_t size, void *pline);
@@ -651,7 +674,7 @@ H5_DLL hbool_t H5D__chunk_is_partial_edge_chunk(unsigned dset_ndims, const uint3
 H5_DLL herr_t  H5D__chunk_prune_by_extent(H5D_t *dset, const hsize_t *old_dim);
 H5_DLL herr_t  H5D__chunk_set_sizes(H5D_t *dset);
 #ifdef H5_HAVE_PARALLEL
-H5_DLL herr_t H5D__chunk_addrmap(const H5D_io_info_t *io_info, haddr_t chunk_addr[]);
+H5_DLL herr_t H5D__chunk_addrmap(const H5D_t *dset, haddr_t chunk_addr[]);
 #endif /* H5_HAVE_PARALLEL */
 H5_DLL herr_t H5D__chunk_update_cache(H5D_t *dset);
 H5_DLL herr_t H5D__chunk_copy(H5F_t *f_src, H5O_storage_chunk_t *storage_src, H5O_layout_chunk_t *layout_src,
@@ -662,8 +685,8 @@ H5_DLL herr_t H5D__chunk_bh_info(const H5O_loc_t *loc, H5O_t *oh, H5O_layout_t *
 H5_DLL herr_t H5D__chunk_dump_index(H5D_t *dset, FILE *stream);
 H5_DLL herr_t H5D__chunk_delete(H5F_t *f, H5O_t *oh, H5O_storage_t *store);
 H5_DLL herr_t H5D__chunk_get_offset_copy(const H5D_t *dset, const hsize_t *offset, hsize_t *offset_copy);
-H5_DLL herr_t H5D__chunk_direct_write(const H5D_t *dset, uint32_t filters, hsize_t *offset,
-                                      uint32_t data_size, const void *buf);
+H5_DLL herr_t H5D__chunk_direct_write(H5D_t *dset, uint32_t filters, hsize_t *offset, uint32_t data_size,
+                                      const void *buf);
 H5_DLL herr_t H5D__chunk_direct_read(const H5D_t *dset, hsize_t *offset, uint32_t *filters, void *buf);
 #ifdef H5D_CHUNK_DEBUG
 H5_DLL herr_t H5D__chunk_stats(const H5D_t *dset, hbool_t headers);
@@ -711,39 +734,31 @@ H5_DLL herr_t H5D__fill_term(H5D_fill_buf_info_t *fb_info);
 #define H5Dmpio_DEBUG
 #endif /*H5Dmpio_DEBUG*/
 #endif /*H5D_DEBUG*/
-/* MPI-IO function to read, it will select either regular or irregular read */
-H5_DLL herr_t H5D__mpio_select_read(const H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                    hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space);
-
-/* MPI-IO function to write, it will select either regular or irregular read */
-H5_DLL herr_t H5D__mpio_select_write(const H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                     hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space);
-
-/* MPI-IO functions to handle contiguous collective IO */
-H5_DLL herr_t H5D__contig_collective_read(H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                          hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space,
-                                          H5D_chunk_map_t *fm);
-H5_DLL herr_t H5D__contig_collective_write(H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                           hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space,
-                                           H5D_chunk_map_t *fm);
-
-/* MPI-IO functions to handle chunked collective IO */
-H5_DLL herr_t H5D__chunk_collective_read(H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                         hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space,
-                                         H5D_chunk_map_t *fm);
-H5_DLL herr_t H5D__chunk_collective_write(H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
-                                          hsize_t nelmts, H5S_t *file_space, H5S_t *mem_space,
-                                          H5D_chunk_map_t *fm);
+/* MPI-IO function to read multi-dsets (Chunk, Contig), it will select either
+ * regular or irregular read */
+H5_DLL herr_t H5D__mpio_select_read(const H5D_io_info_t *io_info, hsize_t nelmts, H5S_t *file_space,
+                                    H5S_t *mem_space);
+
+/* MPI-IO function to write multi-dsets (Chunk, Contig), it will select either
+ * regular or irregular write */
+H5_DLL herr_t H5D__mpio_select_write(const H5D_io_info_t *io_info, hsize_t nelmts, H5S_t *file_space,
+                                     H5S_t *mem_space);
+
+/* MPI-IO functions to handle collective IO for multiple dsets (CONTIG, CHUNK) */
+H5_DLL herr_t H5D__collective_read(H5D_io_info_t *io_info);
+H5_DLL herr_t H5D__collective_write(H5D_io_info_t *io_info);
 
 /* MPI-IO function to check if a direct I/O transfer is possible between
  * memory and the file */
-H5_DLL htri_t H5D__mpio_opt_possible(const H5D_io_info_t *io_info, const H5S_t *file_space,
-                                     const H5S_t *mem_space, const H5D_type_info_t *type_info);
+H5_DLL htri_t H5D__mpio_opt_possible(H5D_io_info_t *io_info);
 H5_DLL herr_t H5D__mpio_get_no_coll_cause_strings(char *local_cause, size_t local_cause_len,
                                                   char *global_cause, size_t global_cause_len);
 
 #endif /* H5_HAVE_PARALLEL */
 
+/* Free a piece (chunk or contiguous dataset data block) info struct */
+H5_DLL herr_t H5D__free_piece_info(void *item, void *key, void *opdata);
+
 /* Testing functions */
 #ifdef H5D_TESTING
 H5_DLL herr_t H5D__layout_version_test(hid_t did, unsigned *version);