[svn-r14761] Several odds and sods:

1) Code to read and write the metadata journaling configuration block
   and associated test code.  (Quincey: Just recalled that I have not
   converted the memory type of the metadata journaling configuration
   block to H5FD_MEM_SUPER per our email conversation.  It will be in
   the next checkin.)

2) Dummy begin/end transaction calls on the off chance that Quincey
   gets to working on this before I check in the real ones.

3) Updates to cache2 in test to reduce the size of the test according
   to the value of the HDF5TestExpress environment variable.  Run times
   on Phoenix using the core file driver are as follows:

        HDF5TestExpress = 0		20:20
        HDF5TestExpress = 1		 4:56
        HDF5TestExpress = 2		 3:18
        HDF5TestExpress = 3		 0:25

   With HDF5TestExpress = 3, I skip the smoke checks entirely.  With
   HDF5TestExpress = 2, I set the number of itterations as low as it
   can go without a major re-write.  (Albert:  I hope running with 
   HDF5TestExpress = 2 will work for you.  If it doesn't, we will just
   have to run with HDF5TestExpress = 3 on RedStorm, and skip the
   smoke checks for now.

Tested serial on Phonenix and parallel on kagiso.

5 files changed, 808 insertions, 5 deletions

diff --git a/src/H5C2.c b/src/H5C2.c
index 51ca741..987c518 100644
--- a/src/H5C2.c
+++ b/src/H5C2.c
@@ -3057,6 +3057,7 @@ H5C2_create(const H5F_t *               f,
     /* metadata journaling related fields */
     cache_ptr->mdj_enabled				 = FALSE;
     cache_ptr->mdj_file_name_ptr                         = NULL;
+    cache_ptr->mdj_conf_block_addr                       = HADDR_UNDEF;
     cache_ptr->mdj_conf_block_len                        = 0;
     cache_ptr->mdj_conf_block_ptr                        = NULL;
     (cache_ptr->mdj_jbrb).magic                          = 
diff --git a/src/H5C2journal.c b/src/H5C2journal.c
index 97a6f1d..6109cd7 100644
--- a/src/H5C2journal.c
+++ b/src/H5C2journal.c
@@ -36,15 +36,746 @@
  *-------------------------------------------------------------------------
  */
 
-#define H5C2_PACKAGE            /*suppress error about including H5C2pkg  */
+#define H5F_PACKAGE             /* suppress error about including H5Fpkg  */
+#define H5C2_PACKAGE            /* suppress error about including H5C2pkg */
 
 #include "H5private.h"          /* Generic Functions                    */
 #include "H5Eprivate.h"         /* Error handling                       */
 #include "H5MMprivate.h"        /* Memory management                    */
+#include "H5MFprivate.h"        /* File memory management               */
+#include "H5Fpkg.h"		/* File access                          */
 #include "H5C2pkg.h"            /* Cache                                */
 
 
 /**************************************************************************/
+/************************* journaling code proper *************************/
+/**************************************************************************/
+
+/*-------------------------------------------------------------------------
+ * Function:    H5C2__begin_transaction
+ *
+ * Purpose:     Handle book keeping for the beginning of a transaction, and
+ *              return the transaction ID assigned to the transaction in 
+ *              *trans_num_ptr.  
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ * Programmer:  John Mainzer
+ *              March 18, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/* This function is just a shell for now. -- JRM */
+
+herr_t
+H5C2__begin_transaction(H5C2_t * cache_ptr,
+		        uint64_t * trans_num_ptr)
+{
+    herr_t ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(H5C2__begin_transaction, FAIL)
+    
+    HDassert( cache_ptr != NULL );
+    HDassert( cache_ptr->magic == H5C2__H5C2_T_MAGIC );
+
+    /* we need at least one error to keep the macros happy */
+    if ( trans_num_ptr == NULL ) {
+
+	HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "trans_num_ptr NULL on entry.")
+    }
+
+    *trans_num_ptr = 1024;
+
+done:
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5C2__begin_transaction() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5C2__end_transaction
+ *
+ * Purpose:     Handle book keeping for the end of a transaction.
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ * Programmer:  John Mainzer
+ *              March 18, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/* This function is just a shell for now. -- JRM */
+
+herr_t
+H5C2__end_transaction(H5C2_t * cache_ptr,
+                      uint64_t trans_num)
+{
+    herr_t ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(H5C2__end_transaction, FAIL)
+    
+    HDassert( cache_ptr != NULL );
+    HDassert( cache_ptr->magic == H5C2__H5C2_T_MAGIC );
+
+    /* we need at least one error to keep the macros happy */
+    if ( trans_num != 1024 ) {
+
+	HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "unexpected transaction number.")
+    }
+
+done:
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5C2__end_transaction() */
+
+
+
+/**************************************************************************/
+/***************** journal config block management code *******************/
+/**************************************************************************/
+
+/*-------------------------------------------------------------------------
+ * Function:    H5C2__create_journal_config_block()
+ *
+ * Purpose:     Given a string containing a journal file name and a pointer
+ * 		to the associated instance of H5C2_t, allocate a journal
+ * 		configuration block, write it to file, and update the 
+ * 		instance of H5C2_t.
+ *
+ * 		Note that the method assumes that mdj_conf_block_addr is 
+ * 		NULL on entry.
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ * Programmer:  John Mainzer
+ *              March 7, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+
+herr_t
+H5C2_create_journal_config_block(H5C2_t * cache_ptr,
+                                 hid_t dxpl_id,
+                                 const char * journal_file_name_ptr)
+{
+    size_t path_len = 0;
+    hsize_t block_len = 0;
+    haddr_t block_addr = HADDR_UNDEF;
+    void * block_ptr = NULL;
+    uint8_t version = H5C2__JOURNAL_CONF_VERSION;
+    uint8_t * p = NULL;
+    char * jfn_ptr = NULL;
+    uint32_t chksum;
+    herr_t ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(H5C2_create_journal_config_block, FAIL)
+
+    HDassert( cache_ptr );
+    HDassert( cache_ptr->magic == H5C2__H5C2_T_MAGIC );
+    HDassert( cache_ptr->f != NULL );
+
+    if ( cache_ptr->mdj_conf_block_ptr != NULL ) {
+
+            HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, \
+		        "cache_ptr->mdj_conf_block_ptr != NULL on entry?!?")
+    } 
+
+    HDassert( journal_file_name_ptr != NULL );
+
+    path_len = strlen(journal_file_name_ptr) + 1;
+
+    HDassert( path_len > 0 );
+
+    block_len = H5C2__JOURNAL_BLOCK_LEN(path_len, cache_ptr->f);
+
+    block_ptr = (void *)H5MM_malloc((size_t)block_len);
+
+    if ( block_ptr == NULL ) {
+
+	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, \
+                    "allocation of in core journal config block failed.");
+    }
+
+    p = (uint8_t *)block_ptr;
+
+    /* copy the signature into the config block */
+    HDmemcpy(p, H5C2__JOURNAL_CONF_MAGIC, H5C2__JOURNAL_MAGIC_LEN);
+    p += H5C2__JOURNAL_MAGIC_LEN;
+
+    /* copy the version into the config block */
+    HDmemcpy(p, &version, 1);
+    p++;
+
+    /* copy the length of the journal file path into the config block */
+    H5F_ENCODE_LENGTH(cache_ptr->f, p, path_len);
+
+    /* copy the path to the journal file into the config block, including 
+     * the terminalting null.  Before we do so, make note of p, as its 
+     * value will be the address of our copy of the journal file path.
+     */
+    jfn_ptr = (char *)p;
+    HDmemcpy(p, journal_file_name_ptr, path_len + 1);
+    p += path_len + 1;
+
+    HDassert( strcmp(jfn_ptr, journal_file_name_ptr) == 0 );
+
+    /* compute and save checksum */
+    chksum = H5_checksum_metadata(block_ptr, (size_t)(block_len - 4), 0);
+    UINT32ENCODE(p, chksum);
+
+    HDassert( (unsigned)(p - (uint8_t *)block_ptr) == block_len );
+
+
+    /* having created an in core image of the journaling configuration block,
+     * we must now allocate space for it in file, and write it to disk.
+     */
+
+    block_addr = H5MF_alloc(cache_ptr->f,
+		            H5FD_MEM_MDJCONFIG,
+			    dxpl_id,
+			    block_len);
+
+    if ( block_addr == HADDR_UNDEF ) {
+
+	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, \
+                    "allocation of file journal config block failed.");
+    }
+
+    /* now write the block to disk -- note that we don't sync.  We will
+     * have to do that later.
+     */
+     if ( H5F_block_write(cache_ptr->f, H5FD_MEM_MDJCONFIG, block_addr,
+                          (size_t)block_len, dxpl_id, block_ptr) < 0 )
+     {
+         HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                     "Can't write metadata journaling config block to file.")
+     }
+
+     /* finally, if we we get this far, update the cache data structure to
+      * record the metadata journaling configuration block.
+      */
+     cache_ptr->mdj_file_name_ptr = jfn_ptr;
+     cache_ptr->mdj_conf_block_addr = block_addr;
+     cache_ptr->mdj_conf_block_len = block_len;
+     cache_ptr->mdj_conf_block_ptr = block_ptr;
+
+done:
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5AC2__create_journal_config_block() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5C2__discard_journal_config_block()
+ *
+ * Purpose:     Free the file and core space allocated to the metadata 
+ *              journaling configuration block, and re-set all the associated
+ *              fields in the cache's instance of H5C2_t.
+ *
+ * 		Note that the method assumes that 
+ *
+ * 			struct_ptr->mdj_file_name_ptr,
+ * 			struct_ptr->mdj_conf_block_addr,
+ * 			struct_ptr->mdj_conf_block_len, and
+ * 			struct_ptr->mdj_conf_block_ptr
+ * 		
+ * 		are all set up for the current metadata journaling 
+ * 		configuration block on entry.  On successful exit, these
+ * 		fields will all be reset to their initial values.
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ * Programmer:  John Mainzer
+ *              March 7, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+
+herr_t
+H5C2_discard_journal_config_block(H5C2_t * cache_ptr,
+                                  hid_t dxpl_id)
+{
+    herr_t ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(H5C2_discard_journal_config_block, FAIL)
+
+    HDassert( cache_ptr );
+    HDassert( cache_ptr->magic == H5C2__H5C2_T_MAGIC );
+    HDassert( cache_ptr->f != NULL );
+
+    if ( ( cache_ptr->mdj_conf_block_addr == HADDR_UNDEF ) ||
+         ( cache_ptr->mdj_conf_block_len == 0 ) ||
+	 ( cache_ptr->mdj_conf_block_ptr == NULL ) ||
+	 ( cache_ptr->mdj_file_name_ptr == NULL ) ) {
+
+            HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, \
+		        "metadata journaling config block undefined on entry?!?")
+    } 
+
+    if ( H5MF_xfree(cache_ptr->f, H5FD_MEM_MDJCONFIG, dxpl_id, 
+		    cache_ptr->mdj_conf_block_addr,
+		    cache_ptr->mdj_conf_block_len) < 0 ) {
+
+	HGOTO_ERROR(H5E_RESOURCE, H5E_CANTFREE, FAIL, \
+                    "deallocation of file journal config block failed.");
+    }
+
+    H5MM_xfree(cache_ptr->mdj_conf_block_ptr);
+
+    /* if we get this far, go ahead and null out the fields in *cache_ptr */
+    cache_ptr->mdj_conf_block_addr = HADDR_UNDEF;
+    cache_ptr->mdj_conf_block_len = 0;
+    cache_ptr->mdj_conf_block_ptr = NULL;
+    cache_ptr->mdj_file_name_ptr = NULL;
+
+done:
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5AC2__discard_journal_config_block() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5C2_get_journaling_in_progress()
+ *
+ * Purpose:     Query the HDF5 file to see if it is marked as having
+ * 		journaling in progress.  Update the journaling 
+ * 		configuration fields in the cache structure accordingly.
+ *
+ * 		At least initially, the purpose of this function is
+ * 		to examine a newly opened HDF5 file, and determine
+ * 		whether journaling was enabled.  If so, we can presume
+ * 		that the application crashed while journaling, and that
+ * 		we must refuse to open the file until the user runs the
+ * 		recovery utility on it.
+ *
+ * 		Hwever, this logic will be handled at a higher level.
+ * 		In this function, we just get the journaling configuration
+ * 		(if any) that has been saved in the file, and load it
+ * 		into *cache_ptr.
+ *
+ * 		Note that this function assumes that *cache_ptr has
+ * 		no journaling configuration set before the function
+ * 		is called.
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ * Programmer:  John Mainzer
+ *              March 11, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+
+herr_t
+H5C2_get_journaling_in_progress(H5C2_t * cache_ptr,
+                                hid_t dxpl_id)
+{
+    herr_t result;
+    herr_t ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(H5C2_mark_journaling_in_progress, FAIL)
+
+    HDassert( cache_ptr );
+    HDassert( cache_ptr->magic == H5C2__H5C2_T_MAGIC );
+    HDassert( cache_ptr->f != NULL );
+    HDassert( cache_ptr->f->shared != NULL );
+    HDassert( ! cache_ptr->f->shared->mdc_jrnl_enabled );
+    HDassert( cache_ptr->mdj_conf_block_addr == HADDR_UNDEF );
+    HDassert( cache_ptr->mdj_conf_block_len == 0 );
+    HDassert( cache_ptr->mdj_conf_block_ptr == NULL );
+    HDassert( cache_ptr->mdj_file_name_ptr == NULL );
+
+    if ( cache_ptr->f->shared->mdc_jrnl_enabled == TRUE ) {
+	    
+        result = H5C2_load_journal_config_block(cache_ptr,
+                                                dxpl_id,
+                                                cache_ptr->mdj_conf_block_addr,
+                                                cache_ptr->mdj_conf_block_len);
+        if ( result != SUCCEED ) {
+
+            HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                        "H5C2_load_journal_config_block() failed.")
+	}
+    }
+
+done:
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5AC2__get_journal_config_block() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5C2_load_journal_config_block()
+ *
+ * Purpose:     Given the base address and lenght of a journal configuration
+ * 		block, attempt to load it, and store it in the cache structure.
+ *
+ * 		Note that the method assumes that mdj_conf_block_addr is 
+ * 		NULL on entry.
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ * Programmer:  John Mainzer
+ *              March 11, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+
+herr_t
+H5C2_load_journal_config_block(H5C2_t * cache_ptr,
+                               hid_t dxpl_id,
+                               haddr_t block_addr,
+                               hsize_t block_len)
+{
+    size_t path_len = 0;
+    void * block_ptr = NULL;
+    uint8_t version;
+    uint8_t * p = NULL;
+    char * jfn_ptr = NULL;
+    uint32_t computed_chksum;
+    uint32_t read_chksum;
+    herr_t ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(H5C2_load_journal_config_block, FAIL)
+
+    HDassert( cache_ptr );
+    HDassert( cache_ptr->magic == H5C2__H5C2_T_MAGIC );
+    HDassert( cache_ptr->f != NULL );
+
+    if ( cache_ptr->mdj_conf_block_ptr != NULL ) {
+
+       HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, \
+                   "cache_ptr->mdj_conf_block_ptr != NULL on entry?!?")
+    } 
+
+    block_ptr = (void *)H5MM_malloc((size_t)block_len);
+
+    if ( block_ptr == NULL ) {
+
+	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, \
+                    "allocation of in core journal config block failed.");
+    }
+
+    p = (uint8_t *)block_ptr;
+
+    /* read the metadata journaling block from file */
+    if ( H5F_block_read(cache_ptr->f, H5FD_MEM_MDJCONFIG, block_addr, 
+			(size_t)block_len, dxpl_id, block_ptr) < 0 ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "Can't read metadata journaling configuration block.")
+    }
+
+    /* verify the signature */
+    if ( HDmemcmp(p, H5C2__JOURNAL_CONF_MAGIC, H5C2__JOURNAL_MAGIC_LEN) != 0 ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "Bad signature on metadata journaling configuration block.")
+    }
+    p += H5C2__JOURNAL_MAGIC_LEN;
+
+    /* get the version of the config block */
+    HDmemcpy(&version, p, 1);
+    p++;
+
+    if ( version != H5C2__JOURNAL_CONF_VERSION ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "Bad version on metadata journaling configuration block.")
+    }
+
+    /* get the length of the journal file path into the config block */
+    H5F_DECODE_LENGTH(cache_ptr->f, p, path_len);
+
+    /* Verify that the length matches the actual path length.  Also,
+     * make note of p, as its value will be the address of our copy of 
+     * the journal file path.
+     */
+    jfn_ptr = (char *)p;
+    if ( strlen(jfn_ptr) != path_len - 1 ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "Bad path_len in metadata journaling configuration block.")
+    }
+
+    p += path_len + 1;
+
+    /* get the checksum from the block */
+    UINT32DECODE(p, read_chksum);
+
+    /* compute the actual checksum */
+    computed_chksum = 
+	    H5_checksum_metadata(block_ptr, (size_t)(block_len - 4), 0);
+
+    /* verify that the computed and read checksums match */
+    if ( computed_chksum != read_chksum ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "Bad checksum in metadata journaling configuration block.")
+    }
+
+    HDassert( (unsigned)(p - (uint8_t *)block_ptr) == block_len );
+
+     /* finally, if we we get this far, we have read the metadata journaling
+      * configuration block successfully.  Record the data in the cache 
+      * structure.
+      */
+    cache_ptr->mdj_file_name_ptr = jfn_ptr;
+    cache_ptr->mdj_conf_block_addr = block_addr;
+    cache_ptr->mdj_conf_block_len = block_len;
+    cache_ptr->mdj_conf_block_ptr = block_ptr;
+
+done:
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5AC2__load_journal_config_block() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5C2_mark_journaling_in_progress()
+ *
+ * Purpose:     Modify the HDF5 file to indicate that journaling is 
+ * 		in progress, and flush the file to disk.  
+ *
+ * 		The objective here is to allow us to detect the fact 
+ * 		the file was being journaled if we crash before we 
+ * 		close the file properly.
+ *
+ * 		Note that the function assumes that the file is not 
+ * 		currently marked as having journaling in progress.
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ * Programmer:  John Mainzer
+ *              March 11, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+
+herr_t
+H5C2_mark_journaling_in_progress(H5C2_t * cache_ptr,
+                                 hid_t dxpl_id,
+                                 const char * journal_file_name_ptr)
+{
+    herr_t result;
+    herr_t ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(H5C2_mark_journaling_in_progress, FAIL)
+
+    HDassert( cache_ptr );
+    HDassert( cache_ptr->magic == H5C2__H5C2_T_MAGIC );
+    HDassert( cache_ptr->f != NULL );
+    HDassert( cache_ptr->f->shared != NULL );
+    HDassert( ! cache_ptr->f->shared->mdc_jrnl_enabled );
+    HDassert( cache_ptr->mdj_conf_block_addr == HADDR_UNDEF );
+    HDassert( cache_ptr->mdj_conf_block_len == 0 );
+    HDassert( cache_ptr->mdj_conf_block_ptr == NULL );
+    HDassert( cache_ptr->mdj_file_name_ptr == NULL );
+    HDassert( journal_file_name_ptr != NULL );
+
+    /* Can't journal a read only file, so verify that we are
+     * opened read/write and fail if we are not.
+     */
+    if ( (cache_ptr->f->shared->flags & H5F_ACC_RDWR) == 0 ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "File is opened read only.")
+    }
+
+    /* first, create a metadata journaling configuration block */
+    result = H5C2_create_journal_config_block(cache_ptr,
+                                              dxpl_id,
+                                              journal_file_name_ptr);
+
+    if ( result != SUCCEED ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "H5C2_create_journal_config_block() failed.")
+    }
+
+    HDassert( cache_ptr->mdj_conf_block_addr != HADDR_UNDEF );
+    HDassert( cache_ptr->mdj_conf_block_len != 0 );
+    HDassert( cache_ptr->mdj_conf_block_ptr != NULL );
+    HDassert( cache_ptr->mdj_file_name_ptr != NULL );
+
+    /* now, load the base addr and length of the configuration block
+     * into shared, and then call H5F_super_write_mdj_msg() to write
+     * the metadata journaling superblock extension message to file.
+     */
+    cache_ptr->f->shared->mdc_jrnl_enabled = TRUE;
+    cache_ptr->f->shared->mdc_jrnl_block_loc = cache_ptr->mdj_conf_block_addr;
+    cache_ptr->f->shared->mdc_jrnl_block_len = cache_ptr->mdj_conf_block_len;
+
+    if ( H5F_super_write_mdj_msg(cache_ptr->f, dxpl_id) < 0 ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "H5F_super_write_mdj_msg() failed.")
+    }
+
+    /* Finally, flush the file to ensure that changes made it to disk. */
+
+    /* Quincey: Two issues here:
+     *
+     * 		First, there is the simple matter of using H5Fflush().
+     * 		Given the curent plans for implementing beging/end 
+     * 		transaction, we have the problem of a flush triggering
+     * 		a transaction here -- not what we want.  We could get
+     * 		around this by calling H5F_flush(), but presently that
+     * 		function is local to H5F.c
+     *
+     * 		Second, there is the matter of the scope parameter:
+     * 		At present, I am passing H5F_SCOPE_GLOBAL here -- is 
+     * 		this appropriate?  I guess this comes down to how we 
+     * 		are going to handle journaling in the case of multiple 
+     * 		files -- a point we haven't discussed.  We should do so.
+     */
+
+    if ( H5Fflush(cache_ptr->f->file_id, H5F_SCOPE_GLOBAL) < 0 ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, "H5Fflush() failed.")
+    }
+
+done:
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5C2_mark_journaling_in_progress() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5C2_unmark_journaling_in_progress()
+ *
+ * Purpose:     Modify the HDF5 file to indicate that journaling is 
+ * 		not in progress, and flush the file to disk.  
+ *
+ * 		The objective here is to remove the messages indicating
+ * 		that the file is being journaled.  We will typically do 
+ * 		this either on file close, or if directed to cease 
+ * 		journaling.  Once these messages are removed, we will
+ * 		be able to open the file without triggering a "journaling
+ * 		in progress" failure.
+ *
+ * 		Note that the function assumes that the file is
+ * 		currently marked as having journaling in progress.
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ * Programmer:  John Mainzer
+ *              March 11, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+
+herr_t
+H5C2_unmark_journaling_in_progress(H5C2_t * cache_ptr,
+                                   hid_t dxpl_id)
+{
+    herr_t result;
+    herr_t ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(H5C2_unmark_journaling_in_progress, FAIL)
+
+    HDassert( cache_ptr );
+    HDassert( cache_ptr->magic == H5C2__H5C2_T_MAGIC );
+    HDassert( cache_ptr->f != NULL );
+    HDassert( cache_ptr->f->shared != NULL );
+    HDassert( cache_ptr->f->shared->mdc_jrnl_enabled );
+    HDassert( cache_ptr->mdj_conf_block_addr != HADDR_UNDEF );
+    HDassert( cache_ptr->mdj_conf_block_len > 0 );
+    HDassert( cache_ptr->mdj_conf_block_ptr != NULL );
+    HDassert( cache_ptr->mdj_file_name_ptr != NULL );
+    HDassert( cache_ptr->f->shared->mdc_jrnl_block_loc == 
+              cache_ptr->mdj_conf_block_addr );
+    HDassert( cache_ptr->f->shared->mdc_jrnl_block_len == 
+              cache_ptr->mdj_conf_block_len );
+
+
+    /* Can't journal a read only file, so verify that we are
+     * opened read/write and fail if we are not.
+     */
+    if ( (cache_ptr->f->shared->flags & H5F_ACC_RDWR) == 0 ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "File is opened read only.")
+    }
+
+    /* next, discard the metadata journaling configuration block */
+    result = H5C2_discard_journal_config_block(cache_ptr, dxpl_id);
+
+    if ( result != SUCCEED ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "H5C2_discard_journal_config_block() failed.")
+    }
+
+    HDassert( cache_ptr->mdj_conf_block_addr == HADDR_UNDEF );
+    HDassert( cache_ptr->mdj_conf_block_len == 0 );
+    HDassert( cache_ptr->mdj_conf_block_ptr == NULL );
+    HDassert( cache_ptr->mdj_file_name_ptr == NULL );
+
+    /* now, mark f->shared to indicate that journaling is not in 
+     * progress, and then call H5F_super_write_mdj_msg() to write
+     * the changes to disk.
+     */
+    cache_ptr->f->shared->mdc_jrnl_enabled = FALSE;
+    cache_ptr->f->shared->mdc_jrnl_block_loc = HADDR_UNDEF;
+    cache_ptr->f->shared->mdc_jrnl_block_len = 0;
+
+    if ( H5F_super_write_mdj_msg(cache_ptr->f, dxpl_id) < 0 ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, \
+                    "H5F_super_write_mdj_msg() failed.")
+    }
+
+    /* Finally, flush the file to ensure that changes made it to disk. */
+
+    /* Quincey: Two issues here:
+     *
+     * 		First, there is the simple matter of using H5Fflush().
+     * 		Given the curent plans for implementing beging/end 
+     * 		transaction, we have the problem of a flush triggering
+     * 		a transaction here -- not what we want.  We could get
+     * 		around this by calling H5F_flush(), but presently that
+     * 		function is local to H5F.c
+     *
+     * 		Second, there is the matter of the scope parameter:
+     * 		At present, I am passing H5F_SCOPE_GLOBAL here -- is 
+     * 		this appropriate?  I guess this comes down to how we 
+     * 		are going to handle journaling in the case of multiple 
+     * 		files -- a point we haven't discussed.  We should do so.
+     */
+
+    if ( H5Fflush(cache_ptr->f->file_id, H5F_SCOPE_GLOBAL) < 0 ) {
+
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTJOURNAL, FAIL, "H5Fflush() failed.")
+    }
+
+done:
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5C2_unmark_journaling_in_progress() */
+
+
+
+/**************************************************************************/
 /********************** journal file management code **********************/
 /**************************************************************************/
 
diff --git a/src/H5C2pkg.h b/src/H5C2pkg.h
index 6c3a0de..7d12053 100644
--- a/src/H5C2pkg.h
+++ b/src/H5C2pkg.h
@@ -743,6 +743,13 @@ struct H5C2_jbrb_t
  * 		external file, so this field must be defined if 
  * 		journaling is enabled.
  *
+ * 		To avoid allocating extra memory, mdj_file_name_ptr
+ * 		points into the approprite location in the in core
+ * 		image of the metadata journaling configuration block.
+ *
+ * mdj_conf_block_addr:  Address of the metadata journaling configuration
+ * 		block on disk, or HADDR_UNDEF if that block is undefined.
+ *
  * mdj_conf_block_len: Length (in bytes) of the metadata journaling 
  * 		configuration block, or 0 if that block is undefined.
  *
@@ -999,10 +1006,20 @@ struct H5C2_jbrb_t
  *
  ****************************************************************************/
 
-#define H5C2__H5C2_T_MAGIC	0x005CAC0F
-#define H5C2__MAX_NUM_TYPE_IDS	16
+#define H5C2__H5C2_T_MAGIC		0x005CAC0F
+#define H5C2__MAX_NUM_TYPE_IDS		16
 #define H5C2__PREFIX_LEN		32
 
+#define H5C2__JOURNAL_MAGIC_LEN		(size_t)4
+#define H5C2__JOURNAL_CONF_MAGIC	"MDJC"
+#define H5C2__JOURNAL_CONF_VERSION	((uint8_t)1)
+#define H5C2__JOURNAL_BLOCK_LEN(pathLen, f)	\
+	( H5C2__JOURNAL_MAGIC_LEN +		\
+	  1 + /* version */			\
+          H5F_SIZEOF_SIZE(f) +			\
+	  ((pathLen) + 1) +             	\
+	  4 /* checksum */ )
+
 struct H5C2_t
 {
     uint32_t			magic;
@@ -1088,7 +1105,8 @@ struct H5C2_t
  
     hbool_t			mdj_enabled;
     char *			mdj_file_name_ptr;
-    size_t			mdj_conf_block_len;
+    haddr_t			mdj_conf_block_addr;
+    hsize_t			mdj_conf_block_len;
     void *			mdj_conf_block_ptr;
     struct H5C2_jbrb_t		mdj_jbrb;
 
diff --git a/src/H5C2private.h b/src/H5C2private.h
index 4a7c4b9..67d59a9 100644
--- a/src/H5C2private.h
+++ b/src/H5C2private.h
@@ -83,7 +83,7 @@
  * want them on for testing on occasion, but in general they should be
  * off.
  */
-#define H5C2_MAINTAIN_CLEAN_AND_DIRTY_LRU_LISTS  0
+#define H5C2_MAINTAIN_CLEAN_AND_DIRTY_LRU_LISTS  0 /* JRM */
 
 #endif /* H5_HAVE_PARALLEL */
 
@@ -1409,6 +1409,17 @@ H5_DLL herr_t H5C2_validate_resize_config(H5C2_auto_size_ctl_t * config_ptr,
                                          unsigned int tests);
 
 
+/**************************************************************************/
+/***************** journaling function definitions proper: ****************/
+/**************************************************************************/
+
+H5_DLL herr_t H5C2__begin_transaction(H5C2_t * cache_ptr,
+		                      uint64_t * trans_num_ptr);
+
+H5_DLL herr_t H5C2__end_transaction(H5C2_t * cache_ptr,
+                                    uint64_t trans_num);
+
+
 /*****************************************************************************/
 /****************** journal buffer function definitions: *********************/
 /*****************************************************************************/
@@ -1466,5 +1477,33 @@ H5_DLL herr_t H5C2_jb__bin2hex(uint8_t * buf,
                                size_t buf_offset,
                                size_t buf_size);
 
+/*****************************************************************************/
+/********** journal config block management function definitions: ************/
+/*****************************************************************************/
+
+H5_DLL herr_t H5C2_create_journal_config_block(H5C2_t * cache_ptr,
+                                           hid_t dxpl_id,
+                                           const char * journal_file_name_ptr);
+
+H5_DLL herr_t H5C2_discard_journal_config_block(H5C2_t * cache_ptr,
+                                                hid_t dxpl_id);
+
+H5_DLL herr_t H5C2_get_journaling_in_progress(H5C2_t * cache_ptr,
+                                              hid_t dxpl_id);
+
+H5_DLL herr_t H5C2_load_journal_config_block(H5C2_t * cache_ptr,
+                                             hid_t dxpl_id,
+                                             haddr_t block_addr,
+                                             hsize_t block_len);
+
+H5_DLL herr_t H5C2_mark_journaling_in_progress(H5C2_t * cache_ptr,
+                                            hid_t dxpl_id,
+                                            const char * journal_file_name_ptr);
+
+H5_DLL herr_t H5C2_unmark_journaling_in_progress(H5C2_t * cache_ptr,
+                                                 hid_t dxpl_id);
+
+
+
 #endif /* !_H5C2private_H */
 
diff --git a/src/H5FDpublic.h b/src/H5FDpublic.h
index ebf006b..291fc88 100644
--- a/src/H5FDpublic.h
+++ b/src/H5FDpublic.h
@@ -89,6 +89,20 @@ typedef enum H5FD_mem_t {
 #define H5FD_MEM_SOHM_TABLE     H5FD_MEM_OHDR
 #define H5FD_MEM_SOHM_INDEX     H5FD_MEM_BTREE
 
+/* Map metadata journaling configuration block to raw for now, as it is of
+ * arbitrary size, and the metadata cache will be managing it directly, 
+ * without passing it through the metadata cache proper.  
+ *
+ * 						JRM -- 3/11/08
+ *
+ * Quincey:  I suspect this is bogus.  However, I gather that adding a 
+ *           new memory type is a bit of a bother, so I'm trying to avoid
+ *           it until I talk to you.  Please let me know  what you think
+ *           I should do here.
+ *                                                 -- JRM
+ */
+#define H5FD_MEM_MDJCONFIG 	H5FD_MEM_DRAW
+
 /*
  * A free-list map which maps all types of allocation requests to a single
  * free list.  This is useful for drivers that don't really care about