Avoid reading or writing the 32 locking bytes at the end of the first

meta-page of an LSM database.

FossilOrigin-Name: 2b5df3e8a80ae5c0415081dd9b29acaad1464be2e7971399e52c1c98408322d9

ext/lsm1/lsmInt.h

@@ -65,8 +65,6 @@
 #define LSM_CKSUM0_INIT 42
 #define LSM_CKSUM1_INIT 42
 
-#define LSM_META_PAGE_SIZE 4096
-
 /* "mmap" mode is currently only used in environments with 64-bit address 
 ** spaces. The following macro is used to test for this.  */
 #define LSM_IS_64_BIT (sizeof(void*)==8)
@@ -154,6 +152,15 @@ int lsmErrorBkpt(int);
 #define LSM_LOCK_READER(i)    ((i) + LSM_LOCK_ROTRANS + 1)
 #define LSM_LOCK_RWCLIENT(i)  ((i) + LSM_LOCK_READER(LSM_LOCK_NREADER))
 
+#define LSM_N_LOCK LSM_LOCK_RWCLIENT(LSM_LOCK_NRWCLIENT)
+
+/*
+** Meta-page size and usable size.
+*/
+#define LSM_META_PAGE_SIZE 4096
+
+#define LSM_META_RW_PAGE_SIZE (LSM_META_PAGE_SIZE - LSM_N_LOCK)
+
 /*
 ** Hard limit on the number of free-list entries that may be stored in 
 ** a checkpoint (the remainder are stored as a system record in the LSM).

ext/lsm1/lsm_ckpt.c

@@ -717,7 +717,9 @@ static int ckptChecksumOk(u32 *aCkpt){
   u32 cksum1;
   u32 cksum2;
 
-  if( nCkpt<CKPT_HDR_NCKPT || nCkpt>(LSM_META_PAGE_SIZE)/sizeof(u32) ) return 0;
+  if( nCkpt<CKPT_HDR_NCKPT || nCkpt>(LSM_META_RW_PAGE_SIZE)/sizeof(u32) ){
+    return 0;
+  }
   ckptChecksum(aCkpt, nCkpt, &cksum1, &cksum2);
   return (cksum1==aCkpt[nCkpt-2] && cksum2==aCkpt[nCkpt-1]);
 }
@@ -870,7 +872,7 @@ int lsmCheckpointLoad(lsm_db *pDb, int *piRead){
     int nInt;
 
     nInt = pShm->aSnap1[CKPT_HDR_NCKPT];
-    if( nInt<=(LSM_META_PAGE_SIZE / sizeof(u32)) ){
+    if( nInt<=(LSM_META_RW_PAGE_SIZE / sizeof(u32)) ){
       memcpy(pDb->aSnapshot, pShm->aSnap1, nInt*sizeof(u32));
       if( ckptChecksumOk(pDb->aSnapshot) ){
         if( piRead ) *piRead = 1;
@@ -879,7 +881,7 @@ int lsmCheckpointLoad(lsm_db *pDb, int *piRead){
     }
 
     nInt = pShm->aSnap2[CKPT_HDR_NCKPT];
-    if( nInt<=(LSM_META_PAGE_SIZE / sizeof(u32)) ){
+    if( nInt<=(LSM_META_RW_PAGE_SIZE / sizeof(u32)) ){
       memcpy(pDb->aSnapshot, pShm->aSnap2, nInt*sizeof(u32));
       if( ckptChecksumOk(pDb->aSnapshot) ){
         if( piRead ) *piRead = 2;
@@ -1085,7 +1087,7 @@ int lsmCheckpointSaveWorker(lsm_db *pDb, int bFlush){
   if( rc!=LSM_OK ) return rc;
   assert( ckptChecksumOk((u32 *)p) );
 
-  assert( n<=LSM_META_PAGE_SIZE );
+  assert( n<=LSM_META_RW_PAGE_SIZE );
   memcpy(pShm->aSnap2, p, n);
   lsmShmBarrier(pDb);
   memcpy(pShm->aSnap1, p, n);
@@ -1120,9 +1122,9 @@ int lsmCheckpointSynced(lsm_db *pDb, i64 *piId, i64 *piLog, u32 *pnWrite){
       u8 *aData; 
 
       aData = lsmFsMetaPageData(pPg, &nData);
-      assert( nData==LSM_META_PAGE_SIZE );
+      assert( nData==LSM_META_RW_PAGE_SIZE );
       nCkpt = lsmGetU32(&aData[CKPT_HDR_NCKPT*sizeof(u32)]);
-      if( nCkpt<(LSM_META_PAGE_SIZE/sizeof(u32)) ){
+      if( nCkpt<(LSM_META_RW_PAGE_SIZE/sizeof(u32)) ){
         u32 *aCopy = lsmMallocRc(pDb->pEnv, sizeof(u32) * nCkpt, &rc);
         if( aCopy ){
           memcpy(aCopy, aData, nCkpt*sizeof(u32));

ext/lsm1/lsm_file.c

@@ -214,6 +214,7 @@ struct FileSystem {
   char *zDb;                      /* Database file name */
   char *zLog;                     /* Database file name */
   int nMetasize;                  /* Size of meta pages in bytes */
+  int nMetaRwSize;                /* Read/written size of meta pages in bytes */
   int nPagesize;                  /* Database page-size in bytes */
   int nBlocksize;                 /* Database block-size in bytes */
 
@@ -635,7 +636,8 @@ int lsmFsOpen(
     pFS->zLog = &pFS->zDb[nDb+1];
     pFS->nPagesize = LSM_DFLT_PAGE_SIZE;
     pFS->nBlocksize = LSM_DFLT_BLOCK_SIZE;
-    pFS->nMetasize = 4 * 1024;
+    pFS->nMetasize = LSM_META_PAGE_SIZE;
+    pFS->nMetaRwSize = LSM_META_RW_PAGE_SIZE;
     pFS->pDb = pDb;
     pFS->pEnv = pDb->pEnv;
 
@@ -2271,7 +2273,9 @@ int lsmFsMetaPageGet(
     }else{
       pPg->aData = lsmMallocRc(pFS->pEnv, pFS->nMetasize, &rc);
       if( rc==LSM_OK && bWrite==0 ){
-        rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, pPg->aData, pFS->nMetasize);
+        rc = lsmEnvRead(
+            pFS->pEnv, pFS->fdDb, iOff, pPg->aData, pFS->nMetaRwSize
+        );
       }
 #ifndef NDEBUG
       /* pPg->aData causes an uninitialized access via a downstreadm write().
@@ -2311,7 +2315,7 @@ int lsmFsMetaPageRelease(MetaPage *pPg){
     if( pFS->nMapLimit==0 ){
       if( pPg->bWrite ){
         i64 iOff = (pPg->iPg==2 ? pFS->nMetasize : 0);
-        int nWrite = pFS->nMetasize;
+        int nWrite = pFS->nMetaRwSize;
         rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iOff, pPg->aData, nWrite);
       }
       lsmFree(pFS->pEnv, pPg->aData);
@@ -2328,7 +2332,7 @@ int lsmFsMetaPageRelease(MetaPage *pPg){
 ** set *pnData to the size of the meta-page in bytes before returning.
 */
 u8 *lsmFsMetaPageData(MetaPage *pPg, int *pnData){
-  if( pnData ) *pnData = pPg->pFS->nMetasize;
+  if( pnData ) *pnData = pPg->pFS->nMetaRwSize;
   return pPg->aData;
 }
 

manifest

@@ -1,5 +1,5 @@
-C Fix\sissues\sin\sthe\sPOSIX\sand\sWin32\sinterfaces\sfor\slsm1.
-D 2017-06-29T19:08:52.350
+C Avoid\sreading\sor\swriting\sthe\s32\slocking\sbytes\sat\sthe\send\sof\sthe\sfirst\nmeta-page\sof\san\sLSM\sdatabase.
+D 2017-06-29T20:13:44.630
 F Makefile.in 081e48dfe7f995d57ce1a88ddf4d2917b4349158648a6cd45b42beae30de3a12
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 4ebb1d257cac7fb1bcb4ba59278416d410ff1c4bf59447a9c37a415f3516056a
@@ -236,9 +236,9 @@ F ext/lsm1/lsm-test/lsmtest_tdb4.c 47e8bb5eba266472d690fb8264f1855ebdba0ae5a0e54
 F ext/lsm1/lsm-test/lsmtest_util.c 241622db5a332a09c8e6e7606b617d288a37b557f7d3bce0bb97809f67cc2806
 F ext/lsm1/lsm-test/lsmtest_win32.c 5605aac3bf3852dcc2509fb1d097f5f11556418c1cc9cf0fdd09f9af53c97fb4
 F ext/lsm1/lsm.h 0f6f64ff071471cb87bf98beb8386566f30ea001
-F ext/lsm1/lsmInt.h 4c07df475dff0c7a718839ed4e87a66779055fbe3eb9c4815a0a4ba944da7e42
-F ext/lsm1/lsm_ckpt.c e7907e782fe2e95de0833675e35e726e487cc4cd
-F ext/lsm1/lsm_file.c 2f0232e2dc0262f60cab1b7010785fb961d566c740fc0370101c14ab085739e0
+F ext/lsm1/lsmInt.h b5d6d073aa5d233614cf4d97d81ba313e9f2c50cfaf12952f7efd9cd945bcd04
+F ext/lsm1/lsm_ckpt.c 239a8442693f1de6a06c9136a235757ab63f5a772ff44e1e81f00d71cc96151e
+F ext/lsm1/lsm_file.c fc95548f8cf8e47fda4120215d2c1fc22dfa85e09294e5656a99a846dc80a62b
 F ext/lsm1/lsm_log.c 5b3e855fcfb85de9fb86fcbf65696cc6886d3231
 F ext/lsm1/lsm_main.c f52eada2910f8a57bd4cafcee39c6c375f6b7ed8
 F ext/lsm1/lsm_mem.c 4c51ea9fa285ee6e35301b33491642d071740a0a
@@ -1627,7 +1627,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 284707a7b3514a55cce24292e45632b7033d6edcff5b27deac5118b27c7b2954
-R 95cb4cb8128c681b43b4c959f1b53467
-U mistachkin
-Z 32c14f0ac7b13bb59a0dfed0d249addc
+P 38ec41416679e8280d77c8a4913aa6a321784b1237a3fe409b8e256c5f4513de
+R b9474a3eab1ca564ebd8be3f19367146
+T *branch * lsm-metapage-fix
+T *sym-lsm-metapage-fix *
+T -sym-trunk *
+U dan
+Z 6a12e4be46d5c11006952d7eec011f51

manifest.uuid

@@ -1 +1 @@
-38ec41416679e8280d77c8a4913aa6a321784b1237a3fe409b8e256c5f4513de
+2b5df3e8a80ae5c0415081dd9b29acaad1464be2e7971399e52c1c98408322d9