Remove cached datatype conversion path table entries on file close (#3942)

Remove cached datatype conversion path table entries on file close

When performing datatype conversions during I/O, the library
checks to see whether it can re-use a cached datatype conversion
pathway by performing comparisons between the source and destination
datatypes of the current operation and the source and destination
datatypes associated with each cached datatype conversion pathway.
For variable-length and reference datatypes, a comparison is made
between the VOL object for the file associated with these datatypes,
which may change as a file is closed and reopened. In workflows
involving a loop that opens a file, performs I/O on an object with a
variable-length or reference datatype and then closes the file, this
can lead to constant memory usage growth as the library compares the
file VOL objects between the datatypes as different and adds a new
cached conversion pathway entry on each iteration during I/O. This is
now fixed by clearing out any cached conversion pathway entries for
variable-length or reference datatypes associated with a particular
file when that file is closed.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/H5Fint.c b/src/H5Fint.c
index 8738026..1feada6 100644
--- a/src/H5Fint.c
+++ b/src/H5Fint.c
@@ -1615,6 +1615,18 @@ H5F__dest(H5F_t *f, bool flush, bool free_on_failure)
         if (vol_wrap_ctx && (NULL == H5VL_object_unwrap(f->vol_obj)))
             HDONE_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "can't unwrap VOL object");
 
+        /*
+         * Clean up any cached type conversion path table entries that
+         * may have been keeping a reference to the file's VOL object
+         * in order to prevent the file from being closed out from
+         * underneath other places that may access the conversion path
+         * or its src/dst datatypes later on (currently, conversions on
+         * variable-length and reference datatypes involve this)
+         */
+        if (H5T_unregister(H5T_PERS_SOFT, NULL, NULL, NULL, f->vol_obj, NULL) < 0)
+            HDONE_ERROR(H5E_FILE, H5E_CANTRELEASE, FAIL,
+                        "unable to free cached type conversion path table entries");
+
         if (H5VL_free_object(f->vol_obj) < 0)
             HDONE_ERROR(H5E_FILE, H5E_CANTDEC, FAIL, "unable to free VOL object");
         f->vol_obj = NULL;