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Overview
Comment:Fix an error in the previous commit on this branch.
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Timelines: family | ancestors | descendants | both | readonly-wal-recovery
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SHA3-256: f71dfee06ce1e0eee760cfca19482bdec7729d6c7d28f10f4cfd21e1f92a04b0
User & Date: dan 2017-10-26 17:34:50.823
Context
2017-11-01
06:59
Fix a race condition in os_unix.c that might allow a client to use a *-shm file corrupted by a power failure if another client fails between locking the *-shm file and truncating it to zero bytes. (check-in: d655bfabd1 user: dan tags: readonly-wal-recovery)
2017-10-26
17:34
Fix an error in the previous commit on this branch. (check-in: f71dfee06c user: dan tags: readonly-wal-recovery)
17:05
Instead of extra locks, use F_GETLK to ensure that readonly_shm clients cannot connect to a wal-mode database if there are no writers. (check-in: 5492f457dc user: dan tags: readonly-wal-recovery)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/os_unix.c.
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      rc = SQLITE_OK;
      if( pShmNode->isReadonly ){
        struct flock lock;
        lock.l_whence = SEEK_SET;
        lock.l_start = UNIX_SHM_DMS;
        lock.l_len = 1;
        lock.l_type = F_WRLCK;
        if( osFcntl(pShmNode->h, F_GETLK, &lockInfo)!=0 ) {
          rc = SQLITE_IOERR_LOCK;
        }else if( lock.l_type==F_UNLCK ){
          rc = SQLITE_CANTOPEN_DIRTYWAL;
        }
      }else if( unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){
        if( robust_ftruncate(pShmNode->h, 0) ){
          rc = unixLogError(SQLITE_IOERR_SHMOPEN, "ftruncate", zShmFilename);








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      rc = SQLITE_OK;
      if( pShmNode->isReadonly ){
        struct flock lock;
        lock.l_whence = SEEK_SET;
        lock.l_start = UNIX_SHM_DMS;
        lock.l_len = 1;
        lock.l_type = F_WRLCK;
        if( osFcntl(pShmNode->h, F_GETLK, &lock)!=0 ) {
          rc = SQLITE_IOERR_LOCK;
        }else if( lock.l_type==F_UNLCK ){
          rc = SQLITE_CANTOPEN_DIRTYWAL;
        }
      }else if( unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){
        if( robust_ftruncate(pShmNode->h, 0) ){
          rc = unixLogError(SQLITE_IOERR_SHMOPEN, "ftruncate", zShmFilename);
︙︙
Changes to test/walro.test.
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  do_test 1.1.13  { sql2 "INSERT INTO t1 VALUES('i', 'j')" } {}

  do_test 1.2.1 {
    code2 { db2 close }
    code1 { db close }
    list [file exists test.db-wal] [file exists test.db-shm]
  } {1 1}

  do_test 1.2.2 {
    code1 { sqlite3 db file:test.db?readonly_shm=1 }
    sql1 { SELECT * FROM t1 }
  } {a b c d e f g h i j}

  do_test 1.2.3 {
    code1 { db close }
    file attributes test.db-shm -permissions rw-r--r--
    hexio_write test.db-shm 0 01020304 
    file attributes test.db-shm -permissions r--r--r--
    code1 { sqlite3 db file:test.db?readonly_shm=1 }
    csql1 { SELECT * FROM t1 }
  } {1 {attempt to write a readonly database}}
  do_test 1.2.4 {
    code1 { sqlite3_extended_errcode db } 
  } {SQLITE_READONLY_RECOVERY}

  do_test 1.2.5 {
    file attributes test.db-shm -permissions rw-r--r--
    code2 { sqlite3 db2 test.db }
    sql2 "SELECT * FROM t1" 
  } {a b c d e f g h i j}
  file attributes test.db-shm -permissions r--r--r--








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  do_test 1.1.13  { sql2 "INSERT INTO t1 VALUES('i', 'j')" } {}

  do_test 1.2.1 {
    code2 { db2 close }
    code1 { db close }
    list [file exists test.db-wal] [file exists test.db-shm]
  } {1 1}

  do_test 1.2.2 {
    code1 { sqlite3 db file:test.db?readonly_shm=1 }
    list [catch { sql1 { SELECT * FROM t1 } } msg] $msg
  } {1 {unable to open database file}}

  do_test 1.2.3 {
    code1 { db close }
    file attributes test.db-shm -permissions rw-r--r--
    hexio_write test.db-shm 0 01020304 
    file attributes test.db-shm -permissions r--r--r--
    code1 { sqlite3 db file:test.db?readonly_shm=1 }
    csql1 { SELECT * FROM t1 }
  } {1 {unable to open database file}}
  do_test 1.2.4 {
    code1 { sqlite3_extended_errcode db } 
  } {SQLITE_CANTOPEN}

  do_test 1.2.5 {
    file attributes test.db-shm -permissions rw-r--r--
    code2 { sqlite3 db2 test.db }
    sql2 "SELECT * FROM t1" 
  } {a b c d e f g h i j}
  file attributes test.db-shm -permissions r--r--r--
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  } {1 {unable to open database file}}
  do_test 1.3.2.3 {
    code1 { db close }
    close [open test.db-shm w]
    file attributes test.db-shm -permissions r--r--r--
    code1 { sqlite3 db file:test.db?readonly_shm=1 }
    csql1 { SELECT * FROM t1 }
  } {1 {attempt to write a readonly database}}
  do_test 1.3.2.4 {
    code1 { sqlite3_extended_errcode db } 
  } {SQLITE_READONLY_RECOVERY}

  #-----------------------------------------------------------------------
  # Test cases 1.4.* check that checkpoints and log wraps don't prevent
  # read-only connections from reading the database.
  do_test 1.4.1 {
    code1 { db close }
    forcedelete test.db-shm








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  } {1 {unable to open database file}}
  do_test 1.3.2.3 {
    code1 { db close }
    close [open test.db-shm w]
    file attributes test.db-shm -permissions r--r--r--
    code1 { sqlite3 db file:test.db?readonly_shm=1 }
    csql1 { SELECT * FROM t1 }
  } {1 {unable to open database file}}
  do_test 1.3.2.4 {
    code1 { sqlite3_extended_errcode db } 
  } {SQLITE_CANTOPEN}

  #-----------------------------------------------------------------------
  # Test cases 1.4.* check that checkpoints and log wraps don't prevent
  # read-only connections from reading the database.
  do_test 1.4.1 {
    code1 { db close }
    forcedelete test.db-shm
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