Do not do a backup if the number of reserved bytes in the source and

destination do not match.  Try to make the match, but if unable fail.

FossilOrigin-Name: 0ca8a2332b28d88585dc890e5162b095e783fc20

1 files changed, 20 insertions, 2 deletions

diff --git a/src/backup.c b/src/backup.c
index c062744c5..5e45a0025 100644
--- a/src/backup.c
+++ b/src/backup.c
@@ -219,6 +219,10 @@ static int backupOnePage(sqlite3_backup *p, Pgno iSrcPg, const u8 *zSrcData){
   int nDestPgsz = sqlite3BtreeGetPageSize(p->pDest);
   const int nCopy = MIN(nSrcPgsz, nDestPgsz);
   const i64 iEnd = (i64)iSrcPg*(i64)nSrcPgsz;
+#ifdef SQLITE_HAS_CODEC
+  int nSrcReserve = sqlite3BtreeGetReserve(p->pSrc);
+  int nDestReserve = sqlite3BtreeGetReserve(p->pDest);
+#endif
 
   int rc = SQLITE_OK;
   i64 iOff;
@@ -237,11 +241,22 @@ static int backupOnePage(sqlite3_backup *p, Pgno iSrcPg, const u8 *zSrcData){
 
 #ifdef SQLITE_HAS_CODEC
   /* Backup is not possible if the page size of the destination is changing
-  ** a a codec is in use.
+  ** and a codec is in use.
   */
   if( nSrcPgsz!=nDestPgsz && sqlite3PagerGetCodec(pDestPager)!=0 ){
     rc = SQLITE_READONLY;
   }
+
+  /* Backup is not possible if the number of bytes of reserve space differ
+  ** between source and destination.  If there is a difference, try to
+  ** fix the destination to agree with the source.  If that is not possible,
+  ** then the backup cannot proceed.
+  */
+  if( nSrcReserve!=nDestReserve ){
+    u32 newPgsz = nSrcPgsz;
+    rc = sqlite3PagerSetPagesize(pDestPager, &newPgsz, nSrcReserve);
+    if( rc==SQLITE_OK && newPgsz!=nSrcPgsz ) rc = SQLITE_READONLY;
+  }
 #endif
 
   /* This loop runs once for each destination page spanned by the source 
@@ -607,7 +622,10 @@ void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
       ** has been modified by a transaction on the source pager. Copy
       ** the new data into the backup.
       */
-      int rc = backupOnePage(p, iPage, aData);
+      int rc;
+      if( p->pDestDb ) sqlite3_mutex_enter(p->pDestDb->mutex);
+      rc = backupOnePage(p, iPage, aData);
+      if( p->pDestDb ) sqlite3_mutex_leave(p->pDestDb->mutex);
       assert( rc!=SQLITE_BUSY && rc!=SQLITE_LOCKED );
       if( rc!=SQLITE_OK ){
         p->rc = rc;