bk commit into 4.1 tree (holyfoot:1.2688) BUG#31305

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ChangeSet@1.2688, 2007-10-29 11:25:45+04:00, holyfoot@mysql.com +1 -0   Bug #31305 myisam tables crash when they are near capacity.   

  When we insert a record into MYISAM table which is almost 'full',   we first write record data in the free space inside a file, and then   check if we have enough space after the end of the file.   So if we don't have the space, table will left corrupted.   Similar error also happens when we updata MYISAM tables.   

  Fixed by modifying write_dynamic_record and update_dynamic_record functions   to check for free space before writing parts of a record

  myisam/mi_dynrec.c@1.43, 2007-10-29 11:25:44+04:00, holyfoot@mysql.com +45 -0     Bug #31305 myisam tables crash when they are near capacity.     

    now we check space left in table in write_dynamic_record     and update_dynamic_record functions.     If we don't have enough room for the new (updated) record, return with the     error.

diff -Nrup a/myisam/mi_dynrec.c b/myisam/mi_dynrec.c
--- a/myisam/mi_dynrec.c	2006-12-01 19:11:41 +04:00

+++ b/myisam/mi_dynrec.c	2007-10-29 11:25:44 +04:00

@@ -26,6 +26,8 @@
 

 #include "myisamdef.h"  

+#define MAX_HEADER_LENGTH 16
+

 /* Enough for comparing if number is zero */  static char zero_string[]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};  

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@@ -145,6 +147,27 @@ static int write_dynamic_record(MI_INFO

   DBUG_ENTER("write_dynamic_record");  

   flag=0;
+
+ /*
+ Check if we have enough room for the new record.
+ First we do simplified check to make usual case faster.
+ Then we do more precise check for the space left.
+ Though it still is not absolutely precise, as
+ we always use MAX_HEADER_LEGNTH while it can be
+ less in the most of the cases
+ */
+
+ if (unlikely(info->s->base.max_data_file_length -
+ info->state->data_file_length < reclength))
+ {
+ if (info->s->base.max_data_file_length - info->state->data_file_length +
+ info->state->empty - info->state->del * MAX_HEADER_LENGTH < reclength)
+ {
+ my_errno=HA_ERR_RECORD_FILE_FULL;
+ DBUG_RETURN(1);
+ }
+ }
+

   do
   {
     if (_mi_find_writepos(info,reclength,&filepos,&length)) @@ -596,6 +619,28 @@ static int update_dynamic_record(MI_INFO

       {
 	uint tmp=MY_ALIGN(reclength - length + 3 +
 			  test(reclength >= 65520L),MI_DYN_ALIGN_SIZE);

+
+        /*
+           Check if we have enough room for the record.
+           First we do simplified check to make usual case faster.
+           Then we do more precise check for the space left.
+           Though it still is not absolutely precise, as
+           we always use MAX_HEADER_LEGNTH while it can be
+           less in the most of the cases
+           */
+
+        if (unlikely(info->s->base.max_data_file_length -
+              info->state->data_file_length < reclength))
+        {
+          if (info->s->base.max_data_file_length - info->state->data_file_length +
+              info->state->empty - info->state->del * MAX_HEADER_LENGTH <
+              reclength - length)
+          {
+            my_errno=HA_ERR_RECORD_FILE_FULL;
+            DBUG_RETURN(1);
+          }
+        }
+

 	/* Don't create a block bigger than MI_MAX_BLOCK_LENGTH */
 	tmp= min(length+tmp, MI_MAX_BLOCK_LENGTH)-length;
 	/* Check if we can extend this block */

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