Do not compare page sizes on source and destination of backup until

transactions are started and the page sizes are locked.  This is a
fix to check-in [7bd44794c4].

FossilOrigin-Name: ec7157788b16936b4b6e4642107b3c86aa44df24

manifest

@@ -1,8 +1,8 @@
 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA1
 
-C Simplifications\sto\sthe\sSHM\slocking\simplementation\sin\sos_unix.c.
-D 2010-05-05T18:20:07
+C Do\snot\scompare\spage\ssizes\son\ssource\sand\sdestination\sof\sbackup\suntil\ntransactions\sare\sstarted\sand\sthe\spage\ssizes\sare\slocked.\s\sThis\sis\sa\nfix\sto\scheck-in\s[7bd44794c4].
+D 2010-05-05T18:46:45
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in d83a0ffef3dcbfb08b410a6c6dd6c009ec9167fb
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -109,7 +109,7 @@ F src/alter.c a9ff6f14b3935502537e90194b66c7bc79bed317
 F src/analyze.c 8dfd781ac326496746ecdfc3e099250ed5d79be5
 F src/attach.c 7abe1607c2054585377cdba3c219e8572f84ca5e
 F src/auth.c 523da7fb4979469955d822ff9298352d6b31de34
-F src/backup.c 5c2dbddbe97f6bc2c01e3fcde4cfd2385b0c7411
+F src/backup.c de9809091b3b99f69e37261c133f7f8b19f6eca6
 F src/bitvec.c 06ad2c36a9c3819c0b9cbffec7b15f58d5d834e0
 F src/btmutex.c 96a12f50f7a17475155971a241d85ec5171573ff
 F src/btree.c d0414a5f09b0cacb64bd60b91c5a3720585925aa
@@ -812,14 +812,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P 7bd44794c482beee16c684712545275e2bf63dfa
-R a2161c22aa5f81f0774fe4cb87094f8c
+P 9de05bfb09e29bafdf5782263330fe8eefcfaba3
+R 37171b2dee1e2cfb0d4c65563316cb42
 U drh
-Z add6d6f68ea7db2fc288d70b0b6b408e
+Z 23a5102ed1b42825806ab1e4a794b6d7
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manifest.uuid

@@ -1 +1 @@
-9de05bfb09e29bafdf5782263330fe8eefcfaba3
+ec7157788b16936b4b6e4642107b3c86aa44df24

src/backup.c

@@ -288,8 +288,8 @@ static void attachBackupObject(sqlite3_backup *p){
 int sqlite3_backup_step(sqlite3_backup *p, int nPage){
   int rc;
   int destMode;       /* Destination journal mode */
-  int pgszSrc;        /* Source page size */
-  int pgszDest;       /* Destination page size */
+  int pgszSrc = 0;    /* Source page size */
+  int pgszDest = 0;   /* Destination page size */
 
   sqlite3_mutex_enter(p->pSrcDb->mutex);
   sqlite3BtreeEnter(p->pSrc);
@@ -297,17 +297,7 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
     sqlite3_mutex_enter(p->pDestDb->mutex);
   }
 
-  /* Do not allow backup if the destination database is in WAL mode */
-  destMode = sqlite3PagerJournalMode(sqlite3BtreePager(p->pDest),
-                                     PAGER_JOURNALMODE_QUERY);
-  pgszSrc = sqlite3BtreeGetPageSize(p->pSrc);
-  pgszDest = sqlite3BtreeGetPageSize(p->pDest);
-  if( destMode==PAGER_JOURNALMODE_WAL && pgszSrc!=pgszDest ){
-    rc = SQLITE_READONLY;
-  }else{
-    rc = p->rc;
-  }
-
+  rc = p->rc;
   if( !isFatalError(rc) ){
     Pager * const pSrcPager = sqlite3BtreePager(p->pSrc);     /* Source pager */
     Pager * const pDestPager = sqlite3BtreePager(p->pDest);   /* Dest pager */
@@ -340,6 +330,16 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
       rc = sqlite3BtreeBeginTrans(p->pSrc, 0);
       bCloseTrans = 1;
     }
+
+    /* Do not allow backup if the destination database is in WAL mode
+    ** and the page sizes are different between source and destination */
+    pgszSrc = sqlite3BtreeGetPageSize(p->pSrc);
+    pgszDest = sqlite3BtreeGetPageSize(p->pDest);
+    destMode = sqlite3PagerJournalMode(sqlite3BtreePager(p->pDest),
+                                         PAGER_JOURNALMODE_QUERY);
+    if( SQLITE_OK==rc && destMode==PAGER_JOURNALMODE_WAL && pgszSrc!=pgszDest ){
+      rc = SQLITE_READONLY;
+    }
   
     /* Now that there is a read-lock on the source database, query the
     ** source pager for the number of pages in the database.