Fix for bug #9269 : Server spins at 100% CPU in get_buffer() after disk full and doesn't recover when space is freed

src/jrd/cch.cpp

@@ -1088,10 +1088,12 @@ void CCH_forget_page(thread_db* tdbb, WIN* window)
 	BufferDesc* bdb = window->win_bdb;
 	Database* dbb = tdbb->getDatabase();
 
+	fb_assert(bdb && bdb->ourExclusiveLock());
+
 	if (window->win_page != bdb->bdb_page || bdb->bdb_buffer->pag_type != pag_undefined)
 		return;	// buffer was reassigned or page was reused
 
-	window->win_bdb = NULL;
+	window->win_bdb = nullptr;
 
 	if (bdb->bdb_flags & BDB_io_error)
 		dbb->dbb_flags &= ~DBB_suspend_bgio;
@@ -1126,10 +1128,9 @@ void CCH_forget_page(thread_db* tdbb, WIN* window)
 	}
 #endif
 
+	bdb->bdb_page.clear();
 	bdb->bdb_flags = 0;
-
-	if (tdbb->tdbb_flags & TDBB_no_cache_unwind)
-		bdb->release(tdbb, true);
+	bdb->release(tdbb, true);
 }
 
 
@@ -2292,6 +2293,45 @@ void CCH_shutdown(thread_db* tdbb)
 	SDW_close();
 }
 
+bool CCH_try_write(thread_db* tdbb, WIN* window)
+{
+/**************************************
+ *
+ *	C C H _ t r y _ w r i t e
+ *
+ **************************************
+ *
+ * Functional description
+ *   Try to write just faked page to disk. Release buffer if successful.
+ *
+ **************************************/
+	BufferDesc* const bdb = window->win_bdb;
+	BLKCHK(bdb, type_bdb);
+
+	BufferControl* bcb = bdb->bdb_bcb;
+
+	constexpr auto FLAGS = (BDB_writer | BDB_marked | BDB_faked);
+
+	fb_assert((bdb->bdb_flags & FLAGS) == FLAGS);
+	fb_assert(bdb->bdb_writers == 1);
+	fb_assert(bdb->ourExclusiveLock());
+	fb_assert(bdb->ourIOLock());
+	fb_assert(QUE_EMPTY(bdb->bdb_higher));
+
+	bdb->bdb_flags &= ~FLAGS;
+
+	bool result = write_page(tdbb, bdb, tdbb->tdbb_status_vector, false);
+
+	bdb->unLockIO(tdbb);
+	if (result)
+	{
+		bdb->release(tdbb, true);
+		window->win_bdb = nullptr;
+	}
+
+	return result;
+}
+
 void CCH_unwind(thread_db* tdbb, const bool punt)
 {
 /**************************************

src/jrd/cch_proto.h

@@ -63,6 +63,7 @@ void		CCH_must_write(Jrd::thread_db*, Jrd::win*);
 void		CCH_precedence(Jrd::thread_db*, Jrd::win*, ULONG);
 void		CCH_precedence(Jrd::thread_db*, Jrd::win*, Jrd::PageNumber);
 void		CCH_tra_precedence(Jrd::thread_db*, Jrd::win*, TraNumber traNum);
+bool		CCH_try_write(Jrd::thread_db*, Jrd::win*);
 #ifdef SUPERSERVER_V2
 void		CCH_prefetch(Jrd::thread_db*, SLONG*, SSHORT);
 bool		CCH_prefetch_pages(Jrd::thread_db*);

src/jrd/os/posix/unix.cpp

@@ -639,14 +639,18 @@ USHORT PIO_init_data(thread_db* tdbb, jrd_file* main_file, FbStatusVector* statu
 		for (int r = 0; r < IO_RETRY; r++)
 		{
 			if (!(file = seek_file(file, &bdb, &offset, status_vector)))
-				return false;
+				return (initPages - leftPages);
+
 			if ((written = os_utils::pwrite(file->fil_desc, zero_buff, to_write, LSEEK_OFFSET_CAST offset)) == to_write)
 				break;
+
 			if (written < 0 && !SYSCALL_INTERRUPTED(errno))
-				return unix_error("write", file, isc_io_write_err, status_vector);
+			{
+				unix_error("write", file, isc_io_write_err, status_vector);
+				return (initPages - leftPages);
+			}
 		}
 
-
 		leftPages -= write_pages;
 		i += write_pages;
 	}

src/jrd/pag.cpp

@@ -801,22 +801,11 @@ static ULONG ensureDiskSpace(thread_db* tdbb, WIN* pip_window, const PageNumber
 			// one page and handle IO errors if any.
 			WIN window(pageNum);
 			CCH_fake(tdbb, &window, 1);
-			CCH_must_write(tdbb, &window);
-			try
+			if (!CCH_try_write(tdbb, &window))
 			{
-				CCH_RELEASE(tdbb, &window);
-			}
-			catch (const status_exception&)
-			{
-				// forget about this page as if we never tried to fake it
 				CCH_forget_page(tdbb, &window);
-
-				// normally all page buffers now released by CCH_unwind
-				// only exception is when TDBB_no_cache_unwind flag is set
-				if (tdbb->tdbb_flags & TDBB_no_cache_unwind)
-					CCH_RELEASE(tdbb, pip_window);
-
-				throw;
+				CCH_RELEASE(tdbb, pip_window);
+				CCH_unwind(tdbb, true);
 			}
 
 			newUsed = relative_bit + 1;

src/jrd/pag.h

@@ -218,6 +218,12 @@ class PageNumber
 		: pageNum(from.pageNum), pageSpaceID(from.pageSpaceID)
 	{ }
 
+	inline void clear()
+	{
+		pageNum = 0;
+		pageSpaceID = INVALID_PAGE_SPACE;
+	}
+
 	inline ULONG getPageNum() const
 	{
 		// fb_assert(pageSpaceID != INVALID_PAGE_SPACE);