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6774 lines (6260 loc) · 225 KB
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/*
** 2004 May 22
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file contains the VFS implementation for unix-like operating systems
** include Linux, MacOSX, *BSD, QNX, VxWorks, AIX, HPUX, and others.
**
** There are actually several different VFS implementations in this file.
** The differences are in the way that file locking is done. The default
** implementation uses Posix Advisory Locks. Alternative implementations
** use flock(), dot-files, various proprietary locking schemas, or simply
** skip locking all together.
**
** This source file is organized into divisions where the logic for various
** subfunctions is contained within the appropriate division. PLEASE
** KEEP THE STRUCTURE OF THIS FILE INTACT. New code should be placed
** in the correct division and should be clearly labeled.
**
** The layout of divisions is as follows:
**
** * General-purpose declarations and utility functions.
** * Unique file ID logic used by VxWorks.
** * Various locking primitive implementations (all except proxy locking):
** + for Posix Advisory Locks
** + for no-op locks
** + for dot-file locks
** + for flock() locking
** + for named semaphore locks (VxWorks only)
** + for AFP filesystem locks (MacOSX only)
** * sqlite3_file methods not associated with locking.
** * Definitions of sqlite3_io_methods objects for all locking
** methods plus "finder" functions for each locking method.
** * sqlite3_vfs method implementations.
** * Locking primitives for the proxy uber-locking-method. (MacOSX only)
** * Definitions of sqlite3_vfs objects for all locking methods
** plus implementations of sqlite3_os_init() and sqlite3_os_end().
*/
#include "sqliteInt.h"
#if SQLITE_OS_UNIX /* This file is used on unix only */
/*
** There are various methods for file locking used for concurrency
** control:
**
** 1. POSIX locking (the default),
** 2. No locking,
** 3. Dot-file locking,
** 4. flock() locking,
** 5. AFP locking (OSX only),
** 6. Named POSIX semaphores (VXWorks only),
** 7. proxy locking. (OSX only)
**
** Styles 4, 5, and 7 are only available of SQLITE_ENABLE_LOCKING_STYLE
** is defined to 1. The SQLITE_ENABLE_LOCKING_STYLE also enables automatic
** selection of the appropriate locking style based on the filesystem
** where the database is located.
*/
#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
# if defined(__APPLE__)
# define SQLITE_ENABLE_LOCKING_STYLE 1
# else
# define SQLITE_ENABLE_LOCKING_STYLE 0
# endif
#endif
/*
** Define the OS_VXWORKS pre-processor macro to 1 if building on
** vxworks, or 0 otherwise.
*/
#ifndef OS_VXWORKS
# if defined(__RTP__) || defined(_WRS_KERNEL)
# define OS_VXWORKS 1
# else
# define OS_VXWORKS 0
# endif
#endif
/*
** These #defines should enable >2GB file support on Posix if the
** underlying operating system supports it. If the OS lacks
** large file support, these should be no-ops.
**
** Large file support can be disabled using the -DSQLITE_DISABLE_LFS switch
** on the compiler command line. This is necessary if you are compiling
** on a recent machine (ex: RedHat 7.2) but you want your code to work
** on an older machine (ex: RedHat 6.0). If you compile on RedHat 7.2
** without this option, LFS is enable. But LFS does not exist in the kernel
** in RedHat 6.0, so the code won't work. Hence, for maximum binary
** portability you should omit LFS.
**
** The previous paragraph was written in 2005. (This paragraph is written
** on 2008-11-28.) These days, all Linux kernels support large files, so
** you should probably leave LFS enabled. But some embedded platforms might
** lack LFS in which case the SQLITE_DISABLE_LFS macro might still be useful.
*/
#ifndef SQLITE_DISABLE_LFS
# define _LARGE_FILE 1
# ifndef _FILE_OFFSET_BITS
# define _FILE_OFFSET_BITS 64
# endif
# define _LARGEFILE_SOURCE 1
#endif
/*
** standard include files.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>
#include <errno.h>
#ifndef SQLITE_OMIT_WAL
#include <sys/mman.h>
#endif
#if SQLITE_ENABLE_LOCKING_STYLE
# include <sys/ioctl.h>
# if OS_VXWORKS
# include <semaphore.h>
# include <limits.h>
# else
# include <sys/file.h>
# include <sys/param.h>
# endif
#endif /* SQLITE_ENABLE_LOCKING_STYLE */
#if defined(__APPLE__) || (SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS)
# include <sys/mount.h>
#endif
#ifdef HAVE_UTIME
# include <utime.h>
#endif
/*
** Allowed values of unixFile.fsFlags
*/
#define SQLITE_FSFLAGS_IS_MSDOS 0x1
/*
** If we are to be thread-safe, include the pthreads header and define
** the SQLITE_UNIX_THREADS macro.
*/
#if SQLITE_THREADSAFE
# include <pthread.h>
# define SQLITE_UNIX_THREADS 1
#endif
/*
** Default permissions when creating a new file
*/
#ifndef SQLITE_DEFAULT_FILE_PERMISSIONS
# define SQLITE_DEFAULT_FILE_PERMISSIONS 0644
#endif
/*
** Default permissions when creating auto proxy dir
*/
#ifndef SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
# define SQLITE_DEFAULT_PROXYDIR_PERMISSIONS 0755
#endif
/*
** Maximum supported path-length.
*/
#define MAX_PATHNAME 512
/*
** Only set the lastErrno if the error code is a real error and not
** a normal expected return code of SQLITE_BUSY or SQLITE_OK
*/
#define IS_LOCK_ERROR(x) ((x != SQLITE_OK) && (x != SQLITE_BUSY))
/* Forward references */
typedef struct unixShm unixShm; /* Connection shared memory */
typedef struct unixShmNode unixShmNode; /* Shared memory instance */
typedef struct unixInodeInfo unixInodeInfo; /* An i-node */
typedef struct UnixUnusedFd UnixUnusedFd; /* An unused file descriptor */
/*
** Sometimes, after a file handle is closed by SQLite, the file descriptor
** cannot be closed immediately. In these cases, instances of the following
** structure are used to store the file descriptor while waiting for an
** opportunity to either close or reuse it.
*/
struct UnixUnusedFd {
int fd; /* File descriptor to close */
int flags; /* Flags this file descriptor was opened with */
UnixUnusedFd *pNext; /* Next unused file descriptor on same file */
};
/*
** The unixFile structure is subclass of sqlite3_file specific to the unix
** VFS implementations.
*/
typedef struct unixFile unixFile;
struct unixFile {
sqlite3_io_methods const *pMethod; /* Always the first entry */
unixInodeInfo *pInode; /* Info about locks on this inode */
int h; /* The file descriptor */
unsigned char eFileLock; /* The type of lock held on this fd */
unsigned char ctrlFlags; /* Behavioral bits. UNIXFILE_* flags */
int lastErrno; /* The unix errno from last I/O error */
void *lockingContext; /* Locking style specific state */
UnixUnusedFd *pUnused; /* Pre-allocated UnixUnusedFd */
const char *zPath; /* Name of the file */
unixShm *pShm; /* Shared memory segment information */
int szChunk; /* Configured by FCNTL_CHUNK_SIZE */
#if SQLITE_ENABLE_LOCKING_STYLE
int openFlags; /* The flags specified at open() */
#endif
#if SQLITE_ENABLE_LOCKING_STYLE || defined(__APPLE__)
unsigned fsFlags; /* cached details from statfs() */
#endif
#if OS_VXWORKS
int isDelete; /* Delete on close if true */
struct vxworksFileId *pId; /* Unique file ID */
#endif
#ifndef NDEBUG
/* The next group of variables are used to track whether or not the
** transaction counter in bytes 24-27 of database files are updated
** whenever any part of the database changes. An assertion fault will
** occur if a file is updated without also updating the transaction
** counter. This test is made to avoid new problems similar to the
** one described by ticket #3584.
*/
unsigned char transCntrChng; /* True if the transaction counter changed */
unsigned char dbUpdate; /* True if any part of database file changed */
unsigned char inNormalWrite; /* True if in a normal write operation */
#endif
#ifdef SQLITE_TEST
/* In test mode, increase the size of this structure a bit so that
** it is larger than the struct CrashFile defined in test6.c.
*/
char aPadding[32];
#endif
};
/*
** Allowed values for the unixFile.ctrlFlags bitmask:
*/
#define UNIXFILE_EXCL 0x01 /* Connections from one process only */
#define UNIXFILE_RDONLY 0x02 /* Connection is read only */
#define UNIXFILE_PERSIST_WAL 0x04 /* Persistent WAL mode */
#ifndef SQLITE_DISABLE_DIRSYNC
# define UNIXFILE_DIRSYNC 0x08 /* Directory sync needed */
#else
# define UNIXFILE_DIRSYNC 0x00
#endif
/*
** Include code that is common to all os_*.c files
*/
#include "os_common.h"
/*
** Define various macros that are missing from some systems.
*/
#ifndef O_LARGEFILE
# define O_LARGEFILE 0
#endif
#ifdef SQLITE_DISABLE_LFS
# undef O_LARGEFILE
# define O_LARGEFILE 0
#endif
#ifndef O_NOFOLLOW
# define O_NOFOLLOW 0
#endif
#ifndef O_BINARY
# define O_BINARY 0
#endif
/*
** The threadid macro resolves to the thread-id or to 0. Used for
** testing and debugging only.
*/
#if SQLITE_THREADSAFE
#define threadid pthread_self()
#else
#define threadid 0
#endif
/*
** Different Unix systems declare open() in different ways. Same use
** open(const char*,int,mode_t). Others use open(const char*,int,...).
** The difference is important when using a pointer to the function.
**
** The safest way to deal with the problem is to always use this wrapper
** which always has the same well-defined interface.
*/
static int posixOpen(const char *zFile, int flags, int mode){
return open(zFile, flags, mode);
}
/* Forward reference */
static int openDirectory(const char*, int*);
/*
** Many system calls are accessed through pointer-to-functions so that
** they may be overridden at runtime to facilitate fault injection during
** testing and sandboxing. The following array holds the names and pointers
** to all overrideable system calls.
*/
static struct unix_syscall {
const char *zName; /* Name of the sytem call */
sqlite3_syscall_ptr pCurrent; /* Current value of the system call */
sqlite3_syscall_ptr pDefault; /* Default value */
} aSyscall[] = {
{ "open", (sqlite3_syscall_ptr)posixOpen, 0 },
#define osOpen ((int(*)(const char*,int,int))aSyscall[0].pCurrent)
{ "close", (sqlite3_syscall_ptr)close, 0 },
#define osClose ((int(*)(int))aSyscall[1].pCurrent)
{ "access", (sqlite3_syscall_ptr)access, 0 },
#define osAccess ((int(*)(const char*,int))aSyscall[2].pCurrent)
{ "getcwd", (sqlite3_syscall_ptr)getcwd, 0 },
#define osGetcwd ((char*(*)(char*,size_t))aSyscall[3].pCurrent)
{ "stat", (sqlite3_syscall_ptr)stat, 0 },
#define osStat ((int(*)(const char*,struct stat*))aSyscall[4].pCurrent)
/*
** The DJGPP compiler environment looks mostly like Unix, but it
** lacks the fcntl() system call. So redefine fcntl() to be something
** that always succeeds. This means that locking does not occur under
** DJGPP. But it is DOS - what did you expect?
*/
#ifdef __DJGPP__
{ "fstat", 0, 0 },
#define osFstat(a,b,c) 0
#else
{ "fstat", (sqlite3_syscall_ptr)fstat, 0 },
#define osFstat ((int(*)(int,struct stat*))aSyscall[5].pCurrent)
#endif
{ "ftruncate", (sqlite3_syscall_ptr)ftruncate, 0 },
#define osFtruncate ((int(*)(int,off_t))aSyscall[6].pCurrent)
{ "fcntl", (sqlite3_syscall_ptr)fcntl, 0 },
#define osFcntl ((int(*)(int,int,...))aSyscall[7].pCurrent)
{ "read", (sqlite3_syscall_ptr)read, 0 },
#define osRead ((ssize_t(*)(int,void*,size_t))aSyscall[8].pCurrent)
#if defined(USE_PREAD) || SQLITE_ENABLE_LOCKING_STYLE
{ "pread", (sqlite3_syscall_ptr)pread, 0 },
#else
{ "pread", (sqlite3_syscall_ptr)0, 0 },
#endif
#define osPread ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[9].pCurrent)
#if defined(USE_PREAD64)
{ "pread64", (sqlite3_syscall_ptr)pread64, 0 },
#else
{ "pread64", (sqlite3_syscall_ptr)0, 0 },
#endif
#define osPread64 ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[10].pCurrent)
{ "write", (sqlite3_syscall_ptr)write, 0 },
#define osWrite ((ssize_t(*)(int,const void*,size_t))aSyscall[11].pCurrent)
#if defined(USE_PREAD) || SQLITE_ENABLE_LOCKING_STYLE
{ "pwrite", (sqlite3_syscall_ptr)pwrite, 0 },
#else
{ "pwrite", (sqlite3_syscall_ptr)0, 0 },
#endif
#define osPwrite ((ssize_t(*)(int,const void*,size_t,off_t))\
aSyscall[12].pCurrent)
#if defined(USE_PREAD64)
{ "pwrite64", (sqlite3_syscall_ptr)pwrite64, 0 },
#else
{ "pwrite64", (sqlite3_syscall_ptr)0, 0 },
#endif
#define osPwrite64 ((ssize_t(*)(int,const void*,size_t,off_t))\
aSyscall[13].pCurrent)
#if SQLITE_ENABLE_LOCKING_STYLE
{ "fchmod", (sqlite3_syscall_ptr)fchmod, 0 },
#else
{ "fchmod", (sqlite3_syscall_ptr)0, 0 },
#endif
#define osFchmod ((int(*)(int,mode_t))aSyscall[14].pCurrent)
#if defined(HAVE_POSIX_FALLOCATE) && HAVE_POSIX_FALLOCATE
{ "fallocate", (sqlite3_syscall_ptr)posix_fallocate, 0 },
#else
{ "fallocate", (sqlite3_syscall_ptr)0, 0 },
#endif
#define osFallocate ((int(*)(int,off_t,off_t))aSyscall[15].pCurrent)
{ "unlink", (sqlite3_syscall_ptr)unlink, 0 },
#define osUnlink ((int(*)(const char*))aSyscall[16].pCurrent)
{ "openDirectory", (sqlite3_syscall_ptr)openDirectory, 0 },
#define osOpenDirectory ((int(*)(const char*,int*))aSyscall[17].pCurrent)
}; /* End of the overrideable system calls */
/*
** This is the xSetSystemCall() method of sqlite3_vfs for all of the
** "unix" VFSes. Return SQLITE_OK opon successfully updating the
** system call pointer, or SQLITE_NOTFOUND if there is no configurable
** system call named zName.
*/
static int unixSetSystemCall(
sqlite3_vfs *pNotUsed, /* The VFS pointer. Not used */
const char *zName, /* Name of system call to override */
sqlite3_syscall_ptr pNewFunc /* Pointer to new system call value */
){
unsigned int i;
int rc = SQLITE_NOTFOUND;
UNUSED_PARAMETER(pNotUsed);
if( zName==0 ){
/* If no zName is given, restore all system calls to their default
** settings and return NULL
*/
rc = SQLITE_OK;
for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
if( aSyscall[i].pDefault ){
aSyscall[i].pCurrent = aSyscall[i].pDefault;
}
}
}else{
/* If zName is specified, operate on only the one system call
** specified.
*/
for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
if( strcmp(zName, aSyscall[i].zName)==0 ){
if( aSyscall[i].pDefault==0 ){
aSyscall[i].pDefault = aSyscall[i].pCurrent;
}
rc = SQLITE_OK;
if( pNewFunc==0 ) pNewFunc = aSyscall[i].pDefault;
aSyscall[i].pCurrent = pNewFunc;
break;
}
}
}
return rc;
}
/*
** Return the value of a system call. Return NULL if zName is not a
** recognized system call name. NULL is also returned if the system call
** is currently undefined.
*/
static sqlite3_syscall_ptr unixGetSystemCall(
sqlite3_vfs *pNotUsed,
const char *zName
){
unsigned int i;
UNUSED_PARAMETER(pNotUsed);
for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
if( strcmp(zName, aSyscall[i].zName)==0 ) return aSyscall[i].pCurrent;
}
return 0;
}
/*
** Return the name of the first system call after zName. If zName==NULL
** then return the name of the first system call. Return NULL if zName
** is the last system call or if zName is not the name of a valid
** system call.
*/
static const char *unixNextSystemCall(sqlite3_vfs *p, const char *zName){
int i = -1;
UNUSED_PARAMETER(p);
if( zName ){
for(i=0; i<ArraySize(aSyscall)-1; i++){
if( strcmp(zName, aSyscall[i].zName)==0 ) break;
}
}
for(i++; i<ArraySize(aSyscall); i++){
if( aSyscall[i].pCurrent!=0 ) return aSyscall[i].zName;
}
return 0;
}
/*
** Retry open() calls that fail due to EINTR
*/
static int robust_open(const char *z, int f, int m){
int rc;
do{ rc = osOpen(z,f,m); }while( rc<0 && errno==EINTR );
return rc;
}
/*
** Helper functions to obtain and relinquish the global mutex. The
** global mutex is used to protect the unixInodeInfo and
** vxworksFileId objects used by this file, all of which may be
** shared by multiple threads.
**
** Function unixMutexHeld() is used to assert() that the global mutex
** is held when required. This function is only used as part of assert()
** statements. e.g.
**
** unixEnterMutex()
** assert( unixMutexHeld() );
** unixEnterLeave()
*/
static void unixEnterMutex(void){
sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
static void unixLeaveMutex(void){
sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
#ifdef SQLITE_DEBUG
static int unixMutexHeld(void) {
return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
}
#endif
#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
/*
** Helper function for printing out trace information from debugging
** binaries. This returns the string represetation of the supplied
** integer lock-type.
*/
static const char *azFileLock(int eFileLock){
switch( eFileLock ){
case NO_LOCK: return "NONE";
case SHARED_LOCK: return "SHARED";
case RESERVED_LOCK: return "RESERVED";
case PENDING_LOCK: return "PENDING";
case EXCLUSIVE_LOCK: return "EXCLUSIVE";
}
return "ERROR";
}
#endif
#ifdef SQLITE_LOCK_TRACE
/*
** Print out information about all locking operations.
**
** This routine is used for troubleshooting locks on multithreaded
** platforms. Enable by compiling with the -DSQLITE_LOCK_TRACE
** command-line option on the compiler. This code is normally
** turned off.
*/
static int lockTrace(int fd, int op, struct flock *p){
char *zOpName, *zType;
int s;
int savedErrno;
if( op==F_GETLK ){
zOpName = "GETLK";
}else if( op==F_SETLK ){
zOpName = "SETLK";
}else{
s = osFcntl(fd, op, p);
sqlite3DebugPrintf("fcntl unknown %d %d %d\n", fd, op, s);
return s;
}
if( p->l_type==F_RDLCK ){
zType = "RDLCK";
}else if( p->l_type==F_WRLCK ){
zType = "WRLCK";
}else if( p->l_type==F_UNLCK ){
zType = "UNLCK";
}else{
assert( 0 );
}
assert( p->l_whence==SEEK_SET );
s = osFcntl(fd, op, p);
savedErrno = errno;
sqlite3DebugPrintf("fcntl %d %d %s %s %d %d %d %d\n",
threadid, fd, zOpName, zType, (int)p->l_start, (int)p->l_len,
(int)p->l_pid, s);
if( s==(-1) && op==F_SETLK && (p->l_type==F_RDLCK || p->l_type==F_WRLCK) ){
struct flock l2;
l2 = *p;
osFcntl(fd, F_GETLK, &l2);
if( l2.l_type==F_RDLCK ){
zType = "RDLCK";
}else if( l2.l_type==F_WRLCK ){
zType = "WRLCK";
}else if( l2.l_type==F_UNLCK ){
zType = "UNLCK";
}else{
assert( 0 );
}
sqlite3DebugPrintf("fcntl-failure-reason: %s %d %d %d\n",
zType, (int)l2.l_start, (int)l2.l_len, (int)l2.l_pid);
}
errno = savedErrno;
return s;
}
#undef osFcntl
#define osFcntl lockTrace
#endif /* SQLITE_LOCK_TRACE */
/*
** Retry ftruncate() calls that fail due to EINTR
*/
static int robust_ftruncate(int h, sqlite3_int64 sz){
int rc;
do{ rc = osFtruncate(h,sz); }while( rc<0 && errno==EINTR );
return rc;
}
/*
** This routine translates a standard POSIX errno code into something
** useful to the clients of the sqlite3 functions. Specifically, it is
** intended to translate a variety of "try again" errors into SQLITE_BUSY
** and a variety of "please close the file descriptor NOW" errors into
** SQLITE_IOERR
**
** Errors during initialization of locks, or file system support for locks,
** should handle ENOLCK, ENOTSUP, EOPNOTSUPP separately.
*/
static int sqliteErrorFromPosixError(int posixError, int sqliteIOErr) {
switch (posixError) {
#if 0
/* At one point this code was not commented out. In theory, this branch
** should never be hit, as this function should only be called after
** a locking-related function (i.e. fcntl()) has returned non-zero with
** the value of errno as the first argument. Since a system call has failed,
** errno should be non-zero.
**
** Despite this, if errno really is zero, we still don't want to return
** SQLITE_OK. The system call failed, and *some* SQLite error should be
** propagated back to the caller. Commenting this branch out means errno==0
** will be handled by the "default:" case below.
*/
case 0:
return SQLITE_OK;
#endif
case EAGAIN:
case ETIMEDOUT:
case EBUSY:
case EINTR:
case ENOLCK:
/* random NFS retry error, unless during file system support
* introspection, in which it actually means what it says */
return SQLITE_BUSY;
case EACCES:
/* EACCES is like EAGAIN during locking operations, but not any other time*/
if( (sqliteIOErr == SQLITE_IOERR_LOCK) ||
(sqliteIOErr == SQLITE_IOERR_UNLOCK) ||
(sqliteIOErr == SQLITE_IOERR_RDLOCK) ||
(sqliteIOErr == SQLITE_IOERR_CHECKRESERVEDLOCK) ){
return SQLITE_BUSY;
}
/* else fall through */
case EPERM:
return SQLITE_PERM;
/* EDEADLK is only possible if a call to fcntl(F_SETLKW) is made. And
** this module never makes such a call. And the code in SQLite itself
** asserts that SQLITE_IOERR_BLOCKED is never returned. For these reasons
** this case is also commented out. If the system does set errno to EDEADLK,
** the default SQLITE_IOERR_XXX code will be returned. */
#if 0
case EDEADLK:
return SQLITE_IOERR_BLOCKED;
#endif
#if EOPNOTSUPP!=ENOTSUP
case EOPNOTSUPP:
/* something went terribly awry, unless during file system support
* introspection, in which it actually means what it says */
#endif
#ifdef ENOTSUP
case ENOTSUP:
/* invalid fd, unless during file system support introspection, in which
* it actually means what it says */
#endif
case EIO:
case EBADF:
case EINVAL:
case ENOTCONN:
case ENODEV:
case ENXIO:
case ENOENT:
#ifdef ESTALE /* ESTALE is not defined on Interix systems */
case ESTALE:
#endif
case ENOSYS:
/* these should force the client to close the file and reconnect */
default:
return sqliteIOErr;
}
}
/******************************************************************************
****************** Begin Unique File ID Utility Used By VxWorks ***************
**
** On most versions of unix, we can get a unique ID for a file by concatenating
** the device number and the inode number. But this does not work on VxWorks.
** On VxWorks, a unique file id must be based on the canonical filename.
**
** A pointer to an instance of the following structure can be used as a
** unique file ID in VxWorks. Each instance of this structure contains
** a copy of the canonical filename. There is also a reference count.
** The structure is reclaimed when the number of pointers to it drops to
** zero.
**
** There are never very many files open at one time and lookups are not
** a performance-critical path, so it is sufficient to put these
** structures on a linked list.
*/
struct vxworksFileId {
struct vxworksFileId *pNext; /* Next in a list of them all */
int nRef; /* Number of references to this one */
int nName; /* Length of the zCanonicalName[] string */
char *zCanonicalName; /* Canonical filename */
};
#if OS_VXWORKS
/*
** All unique filenames are held on a linked list headed by this
** variable:
*/
static struct vxworksFileId *vxworksFileList = 0;
/*
** Simplify a filename into its canonical form
** by making the following changes:
**
** * removing any trailing and duplicate /
** * convert /./ into just /
** * convert /A/../ where A is any simple name into just /
**
** Changes are made in-place. Return the new name length.
**
** The original filename is in z[0..n-1]. Return the number of
** characters in the simplified name.
*/
static int vxworksSimplifyName(char *z, int n){
int i, j;
while( n>1 && z[n-1]=='/' ){ n--; }
for(i=j=0; i<n; i++){
if( z[i]=='/' ){
if( z[i+1]=='/' ) continue;
if( z[i+1]=='.' && i+2<n && z[i+2]=='/' ){
i += 1;
continue;
}
if( z[i+1]=='.' && i+3<n && z[i+2]=='.' && z[i+3]=='/' ){
while( j>0 && z[j-1]!='/' ){ j--; }
if( j>0 ){ j--; }
i += 2;
continue;
}
}
z[j++] = z[i];
}
z[j] = 0;
return j;
}
/*
** Find a unique file ID for the given absolute pathname. Return
** a pointer to the vxworksFileId object. This pointer is the unique
** file ID.
**
** The nRef field of the vxworksFileId object is incremented before
** the object is returned. A new vxworksFileId object is created
** and added to the global list if necessary.
**
** If a memory allocation error occurs, return NULL.
*/
static struct vxworksFileId *vxworksFindFileId(const char *zAbsoluteName){
struct vxworksFileId *pNew; /* search key and new file ID */
struct vxworksFileId *pCandidate; /* For looping over existing file IDs */
int n; /* Length of zAbsoluteName string */
assert( zAbsoluteName[0]=='/' );
n = (int)strlen(zAbsoluteName);
pNew = sqlite3_malloc( sizeof(*pNew) + (n+1) );
if( pNew==0 ) return 0;
pNew->zCanonicalName = (char*)&pNew[1];
memcpy(pNew->zCanonicalName, zAbsoluteName, n+1);
n = vxworksSimplifyName(pNew->zCanonicalName, n);
/* Search for an existing entry that matching the canonical name.
** If found, increment the reference count and return a pointer to
** the existing file ID.
*/
unixEnterMutex();
for(pCandidate=vxworksFileList; pCandidate; pCandidate=pCandidate->pNext){
if( pCandidate->nName==n
&& memcmp(pCandidate->zCanonicalName, pNew->zCanonicalName, n)==0
){
sqlite3_free(pNew);
pCandidate->nRef++;
unixLeaveMutex();
return pCandidate;
}
}
/* No match was found. We will make a new file ID */
pNew->nRef = 1;
pNew->nName = n;
pNew->pNext = vxworksFileList;
vxworksFileList = pNew;
unixLeaveMutex();
return pNew;
}
/*
** Decrement the reference count on a vxworksFileId object. Free
** the object when the reference count reaches zero.
*/
static void vxworksReleaseFileId(struct vxworksFileId *pId){
unixEnterMutex();
assert( pId->nRef>0 );
pId->nRef--;
if( pId->nRef==0 ){
struct vxworksFileId **pp;
for(pp=&vxworksFileList; *pp && *pp!=pId; pp = &((*pp)->pNext)){}
assert( *pp==pId );
*pp = pId->pNext;
sqlite3_free(pId);
}
unixLeaveMutex();
}
#endif /* OS_VXWORKS */
/*************** End of Unique File ID Utility Used By VxWorks ****************
******************************************************************************/
/******************************************************************************
*************************** Posix Advisory Locking ****************************
**
** POSIX advisory locks are broken by design. ANSI STD 1003.1 (1996)
** section 6.5.2.2 lines 483 through 490 specify that when a process
** sets or clears a lock, that operation overrides any prior locks set
** by the same process. It does not explicitly say so, but this implies
** that it overrides locks set by the same process using a different
** file descriptor. Consider this test case:
**
** int fd1 = open("./file1", O_RDWR|O_CREAT, 0644);
** int fd2 = open("./file2", O_RDWR|O_CREAT, 0644);
**
** Suppose ./file1 and ./file2 are really the same file (because
** one is a hard or symbolic link to the other) then if you set
** an exclusive lock on fd1, then try to get an exclusive lock
** on fd2, it works. I would have expected the second lock to
** fail since there was already a lock on the file due to fd1.
** But not so. Since both locks came from the same process, the
** second overrides the first, even though they were on different
** file descriptors opened on different file names.
**
** This means that we cannot use POSIX locks to synchronize file access
** among competing threads of the same process. POSIX locks will work fine
** to synchronize access for threads in separate processes, but not
** threads within the same process.
**
** To work around the problem, SQLite has to manage file locks internally
** on its own. Whenever a new database is opened, we have to find the
** specific inode of the database file (the inode is determined by the
** st_dev and st_ino fields of the stat structure that fstat() fills in)
** and check for locks already existing on that inode. When locks are
** created or removed, we have to look at our own internal record of the
** locks to see if another thread has previously set a lock on that same
** inode.
**
** (Aside: The use of inode numbers as unique IDs does not work on VxWorks.
** For VxWorks, we have to use the alternative unique ID system based on
** canonical filename and implemented in the previous division.)
**
** The sqlite3_file structure for POSIX is no longer just an integer file
** descriptor. It is now a structure that holds the integer file
** descriptor and a pointer to a structure that describes the internal
** locks on the corresponding inode. There is one locking structure
** per inode, so if the same inode is opened twice, both unixFile structures
** point to the same locking structure. The locking structure keeps
** a reference count (so we will know when to delete it) and a "cnt"
** field that tells us its internal lock status. cnt==0 means the
** file is unlocked. cnt==-1 means the file has an exclusive lock.
** cnt>0 means there are cnt shared locks on the file.
**
** Any attempt to lock or unlock a file first checks the locking
** structure. The fcntl() system call is only invoked to set a
** POSIX lock if the internal lock structure transitions between
** a locked and an unlocked state.
**
** But wait: there are yet more problems with POSIX advisory locks.
**
** If you close a file descriptor that points to a file that has locks,
** all locks on that file that are owned by the current process are
** released. To work around this problem, each unixInodeInfo object
** maintains a count of the number of pending locks on tha inode.
** When an attempt is made to close an unixFile, if there are
** other unixFile open on the same inode that are holding locks, the call
** to close() the file descriptor is deferred until all of the locks clear.
** The unixInodeInfo structure keeps a list of file descriptors that need to
** be closed and that list is walked (and cleared) when the last lock
** clears.
**
** Yet another problem: LinuxThreads do not play well with posix locks.
**
** Many older versions of linux use the LinuxThreads library which is
** not posix compliant. Under LinuxThreads, a lock created by thread
** A cannot be modified or overridden by a different thread B.
** Only thread A can modify the lock. Locking behavior is correct
** if the appliation uses the newer Native Posix Thread Library (NPTL)
** on linux - with NPTL a lock created by thread A can override locks
** in thread B. But there is no way to know at compile-time which
** threading library is being used. So there is no way to know at
** compile-time whether or not thread A can override locks on thread B.
** One has to do a run-time check to discover the behavior of the
** current process.
**
** SQLite used to support LinuxThreads. But support for LinuxThreads
** was dropped beginning with version 3.7.0. SQLite will still work with
** LinuxThreads provided that (1) there is no more than one connection
** per database file in the same process and (2) database connections
** do not move across threads.
*/
/*
** An instance of the following structure serves as the key used
** to locate a particular unixInodeInfo object.
*/
struct unixFileId {
dev_t dev; /* Device number */
#if OS_VXWORKS
struct vxworksFileId *pId; /* Unique file ID for vxworks. */
#else
ino_t ino; /* Inode number */
#endif
};
/*
** An instance of the following structure is allocated for each open
** inode. Or, on LinuxThreads, there is one of these structures for
** each inode opened by each thread.
**
** A single inode can have multiple file descriptors, so each unixFile
** structure contains a pointer to an instance of this object and this
** object keeps a count of the number of unixFile pointing to it.
*/
struct unixInodeInfo {
struct unixFileId fileId; /* The lookup key */
int nShared; /* Number of SHARED locks held */
unsigned char eFileLock; /* One of SHARED_LOCK, RESERVED_LOCK etc. */
unsigned char bProcessLock; /* An exclusive process lock is held */
int nRef; /* Number of pointers to this structure */
unixShmNode *pShmNode; /* Shared memory associated with this inode */
int nLock; /* Number of outstanding file locks */
UnixUnusedFd *pUnused; /* Unused file descriptors to close */
unixInodeInfo *pNext; /* List of all unixInodeInfo objects */
unixInodeInfo *pPrev; /* .... doubly linked */
#if SQLITE_ENABLE_LOCKING_STYLE
unsigned long long sharedByte; /* for AFP simulated shared lock */
#endif
#if OS_VXWORKS
sem_t *pSem; /* Named POSIX semaphore */
char aSemName[MAX_PATHNAME+2]; /* Name of that semaphore */
#endif
};
/*
** A lists of all unixInodeInfo objects.
*/
static unixInodeInfo *inodeList = 0;
/*
**
** This function - unixLogError_x(), is only ever called via the macro
** unixLogError().
**
** It is invoked after an error occurs in an OS function and errno has been
** set. It logs a message using sqlite3_log() containing the current value of
** errno and, if possible, the human-readable equivalent from strerror() or
** strerror_r().
**
** The first argument passed to the macro should be the error code that
** will be returned to SQLite (e.g. SQLITE_IOERR_DELETE, SQLITE_CANTOPEN).
** The two subsequent arguments should be the name of the OS function that
** failed (e.g. "unlink", "open") and the the associated file-system path,
** if any.
*/
#define unixLogError(a,b,c) unixLogErrorAtLine(a,b,c,__LINE__)
static int unixLogErrorAtLine(
int errcode, /* SQLite error code */