WT-2693 Check open_cursor error paths for consistent handling (#2859)

* WT-2693 Check open_cursor error paths for consistent handling

There's a problem with cursor functions which don't call their typed
close functions, relying instead on a simple free of the base cursor
type because the __wt_cursor_init() function is the last function called
before successful return. The problem is __wt_cursor_init() doesn't
clean up after itself: for example, it allocates memory to hold the URI
in WT_CURSOR.internal_uri, then has a number of subsequent potential
error returns, and WT_CURSOR.internal_uri won't be free'd unless
__wt_cursor_close() is called. In other words, we should always call
the typed closed function (which in turn calls __wt_cursor_close()).

Specific additional concerns:

cursor/cur_backup.c: __wt_curbackup_open() doesn't turn off backups or
clear the hot-backup flag if __wt_cursor_init() fails, which will hang
the process. Remove the cleanup-on-error code from the __backup_start()
function and rely instead on the backup cursor's close function to do
the work. There's a problem if we fail the initial backup cursor test,
in which case we don't want to do cleanup other than discarding the
cursors themselves. Add the WT_CURBACKUP_LOCKER flag to the
WT_CURSOR_BACKUP structure, which isn't set until we're holding the hot
backup cursor flag, and use it to figure out how much cleanup needs to
be done.

cursor/cur_file.c: the change to call the __curfile_close() function has
a problem with __wt_bulk_wrapup(), which assumes WT_CURSOR_BULK.reconcile
has been initialized, change it to check for NULL.

cursor/cur_file.c: the change to call the __curfile_close() function has
a problem with incrementing the data-source's in-use counter. Instead
of incrementing the counter in __wt_curfile_open() before calling
__curfile_create(), increment it in __curfile_create() after the point
where all failure paths close the cursor.

cursor/cur_log.c: the change to call the __curlog_close() function means
we may be required to clean up a cursor that has not yet acquired the
log archive lock. Add the WT_CURLOG_ARCHIVE_LOCK flag to the WT_CURSOR_LOG
structure so the close function knows if the log archive lock needs to be
released.

cursor/cur_log.c: remove the __curlog_reset() call from __curlog_close(),
we're closing the cursor, resetting it doesn't do anything useful.

cursor/cur_metadata.c: the change to call the __curmetadata_close()
function is slightly tricky, be cautious about closing the underlying
WT_CURSOR_METADATA.file_cursor field, it may not be set when we call
__curmetadata_close().

* comment typo

* fix a comment

* Add explicit comment on the life-cycle of the WT_CURBACKUP_LOCKER flag.

* Review comment, set a specific size on the flags field. Generally, the
cursors all use uint8_t for flags, and I don't think it matters much
what we use, use the same thing everywhere.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/btree/bt_split.c b/src/btree/bt_split.c
index ee9c6ad23e8..ac352b79a25 100644
--- a/src/btree/bt_split.c
+++ b/src/btree/bt_split.c
@@ -1500,7 +1500,7 @@ __split_multi_inmem(
 	 * This code re-creates an in-memory page that is part of a set created
 	 * while evicting a large page, and adds references to any unresolved
 	 * update chains to the new page. We get here due to choosing to keep
-	 * the results of a split in memory or because and update could not be
+	 * the results of a split in memory or because an update could not be
 	 * written when attempting to evict a page.
 	 *
 	 * Clear the disk image and link the page into the passed-in WT_REF to
@@ -2208,9 +2208,9 @@ __wt_split_rewrite(WT_SESSION_IMPL *session, WT_REF *ref)
 	 *
 	 * Build the new page.
 	 *
-	 * Allocate a WT_REF because the error path uses routines that will ea
-	 * free memory. The only field we need to set is the record number, as
-	 * it's used by the search routines.
+	 * Allocate a WT_REF, the error path calls routines that free memory.
+	 * The only field we need to set is the record number, as it's used by
+	 * the search routines.
 	 */
 	WT_RET(__wt_calloc_one(session, &new));
 	new->ref_recno = ref->ref_recno;