mdbx: fix regression related to fallocate() and introduce osal_fsetsize() (backport).

This fixes regression after the 2930b304dc as when
a DXB file remains longer than necessary on Mac or Linux when building without `_GNU_SOURCE`.

src/api-copy.c

@@ -479,7 +479,7 @@ __cold static int copy_with_compacting(MDBX_env *env, MDBX_txn *txn, mdbx_fileha
   if (meta->geometry.now != meta->geometry.first_unallocated) {
     const size_t whole_size = pgno2bytes(env, meta->geometry.now);
     if (!dest_is_pipe)
-      return osal_fallocate(fd, whole_size);
+      return osal_fsetsize(fd, whole_size);
 
     const size_t used_size = pgno2bytes(env, meta->geometry.first_unallocated);
     memset(data_buffer, 0, (size_t)MDBX_ENVCOPY_WRITEBUF);
@@ -648,7 +648,7 @@ retry_snap_meta:
   /* Extend file if required */
   if (likely(rc == MDBX_SUCCESS) && whole_size != used_size) {
     if (!dest_is_pipe)
-      rc = osal_fallocate(fd, whole_size);
+      rc = osal_fsetsize(fd, whole_size);
     else {
       memset(data_buffer, 0, (size_t)MDBX_ENVCOPY_WRITEBUF);
       for (size_t offset = used_size; rc == MDBX_SUCCESS && offset < whole_size;) {

src/dxb.c

@@ -532,7 +532,7 @@ __cold int dxb_setup(MDBX_env *env, const int lck_rc, const mdbx_mode_t mode_bit
     if (unlikely(err != MDBX_SUCCESS))
       return err;
 
-    err = osal_fallocate(env->lazy_fd, env->dxb_mmap.filesize = env->dxb_mmap.current = env->geo_in_bytes.now);
+    err = osal_fsetsize(env->lazy_fd, env->dxb_mmap.filesize = env->dxb_mmap.current = env->geo_in_bytes.now);
     if (unlikely(err != MDBX_SUCCESS))
       return err;
 

src/lck-windows.c

@@ -546,7 +546,7 @@ int lck_destroy(MDBX_env *env, MDBX_env *inprocess_neighbor, const uint32_t curr
     if (synced && !inprocess_neighbor && env->lck_mmap.fd != INVALID_HANDLE_VALUE &&
         lck_upgrade(env, true) == MDBX_SUCCESS)
       /* this will fail if LCK is used/mmapped by other process(es) */
-      osal_ftruncate(env->lck_mmap.fd, 0);
+      osal_fsetsize(env->lck_mmap.fd, 0);
   }
   lck_unlock(env);
   return MDBX_SUCCESS;

src/options.h

@@ -350,6 +350,19 @@
 #error MDBX_USE_COPYFILERANGE must be defined as 0 or 1
 #endif /* MDBX_USE_COPYFILERANGE */
 
+/** Advanced: Using posix_fallocate() or fcntl(F_PREALLOCATE) (autodetection by default). */
+#ifndef MDBX_USE_FALLOCATE
+#if defined(__APPLE__)
+#define MDBX_USE_FALLOCATE 0 /* Too slow and unclean, but not required to prevent SIGBUS */
+#elif (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L) || (__GLIBC_PREREQ(2, 10) && defined(_GNU_SOURCE))
+#define MDBX_USE_FALLOCATE 1
+#else
+#define MDBX_USE_FALLOCATE 0
+#endif
+#elif !(MDBX_USE_FALLOCATE == 0 || MDBX_USE_FALLOCATE == 1)
+#error MDBX_USE_FALLOCATE must be defined as 0 or 1
+#endif /* MDBX_USE_FALLOCATE */
+
 //------------------------------------------------------------------------------
 
 #ifndef MDBX_CPU_WRITEBACK_INCOHERENT

src/osal.c

@@ -1592,8 +1592,7 @@ int osal_is_pipe(mdbx_filehandle_t fd) {
 #endif
 }
 
-/* truncate file: just set the length of a file */
-int osal_ftruncate(mdbx_filehandle_t fd, uint64_t length) {
+int osal_fsetsize(mdbx_filehandle_t fd, const uint64_t length) {
 #if defined(_WIN32) || defined(_WIN64)
   if (imports.SetFileInformationByHandle) {
     FILE_END_OF_FILE_INFO EndOfFileInfo;
@@ -1608,31 +1607,48 @@ int osal_ftruncate(mdbx_filehandle_t fd, uint64_t length) {
   }
 #else
   STATIC_ASSERT_MSG(sizeof(off_t) >= sizeof(size_t), "libmdbx requires 64-bit file I/O on 64-bit systems");
-  return ftruncate(fd, length) == 0 ? MDBX_SUCCESS : errno;
-#endif
-}
 
-/* extend file: set the length of a file AND ensure the space has been allocated */
-int osal_fallocate(mdbx_filehandle_t fd, uint64_t length) {
-  assert(length > 0);
-  int err = MDBX_RESULT_TRUE;
-#if (defined(__linux__) || defined(__gnu_linux__)) &&                                                                  \
-    ((defined(_GNU_SOURCE) && __GLIBC_PREREQ(2, 10)) || (defined(__ANDROID_API__) && __ANDROID_API__ >= 21))
-  err = fallocate(fd, 0, 0, length) ? ignore_enosys_and_eremote(errno) : MDBX_SUCCESS;
-#elif defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L && !defined(__APPLE__)
-  err = posix_fallocate(fd, 0, length) ? ignore_enosys_and_eremote(errno) : MDBX_SUCCESS;
-#elif defined(__APPLE__)
-  fstore_t store = {F_ALLOCATEALL, F_PEOFPOSMODE, 0, length, 0};
-  if (fcntl(fd, F_PREALLOCATE, &store))
-    err = ignore_enosys_and_eremote(errno);
-#endif /* Apple */
-#if !defined(_WIN32) && !defined(_WIN64)
-  /* Workaround for testing: ignore ENOSPC for TMPFS/RAMFS.
-   * This is insignificant for production, but it helps in some tests using /dev/shm inside docker/containers. */
-  if (err == ENOSPC && osal_check_fs_incore(fd) == MDBX_RESULT_TRUE)
-    err = MDBX_RESULT_TRUE;
+#if MDBX_USE_FALLOCATE
+  struct stat info;
+  if (unlikely(fstat(fd, &info)))
+    return errno;
+
+  const uint64_t allocated = UINT64_C(512) * info.st_blocks;
+  if (length > allocated) {
+#if defined(__APPLE__)
+    fstore_t store = {
+        .fst_flags = F_ALLOCATECONTIG, .fst_posmode = F_PEOFPOSMODE, .fst_offset = 0, .fst_length = length};
+    int err = MDBX_SUCCESS;
+    if (fcntl(fd, F_PREALLOCATE, &store)) {
+      /* TODO: implement step-by-step allocation in chunks of 16384, 8192, 4094, 2048, 1024 Kb */
+      store.fst_flags = F_ALLOCATEALL;
+      if (fcntl(fd, F_PREALLOCATE, &store))
+        err = errno;
+    }
+#elif defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L
+    const int err = posix_fallocate(fd, 0, length);
+    if (!err && length > (uint64_t)info.st_size)
+      info.st_size = length /* posix_fallocate() extends the file */;
+#else
+    const int err = fallocate(fd, 0, 0, length) ? errno : MDBX_SUCCESS;
+    if (!err && length > (uint64_t)info.st_size)
+      info.st_size = length /* fallocate() extends the file */;
+#endif
+    if (unlikely(err) && ignore_enosys_and_eremote(err) != MDBX_RESULT_TRUE) {
+      /* Workaround for testing: ignore ENOSPC for TMPFS/RAMFS.
+       * This is insignificant for production, but it helps in some tests using /dev/shm inside docker/containers. */
+      if (err != ENOSPC || osal_check_fs_incore(fd) != MDBX_RESULT_TRUE)
+        return err;
+    }
+  }
+
+  if (length == (uint64_t)info.st_size)
+    return MDBX_SUCCESS;
+#endif
+
+  return unlikely(ftruncate(fd, length)) ? errno : MDBX_SUCCESS;
+
 #endif /* !Windows */
-  return (err == MDBX_RESULT_TRUE) ? osal_ftruncate(fd, length) : err;
 }
 
 int osal_fseek(mdbx_filehandle_t fd, uint64_t pos) {
@@ -2085,8 +2101,8 @@ int osal_mmap(const int flags, osal_mmap_t *map, size_t size, const size_t limit
     return err;
 
   if ((flags & MDBX_RDONLY) == 0 && (options & MMAP_OPTION_SETLENGTH) != 0) {
-    err = osal_fallocate(map->fd, size);
-    VERBOSE("ftruncate %zu, err %d", size, err);
+    err = osal_fsetsize(map->fd, size);
+    VERBOSE("osal_fsetsize %zu, err %d", size, err);
     if (err != MDBX_SUCCESS)
       return err;
     map->filesize = size;
@@ -2331,7 +2347,7 @@ retry_file_and_section:
   }
 
   if ((flags & MDBX_RDONLY) == 0 && map->filesize != size) {
-    err = osal_fallocate(map->fd, size);
+    err = osal_fsetsize(map->fd, size);
     if (err == MDBX_SUCCESS)
       map->filesize = size;
     /* ignore error, because Windows unable shrink file
@@ -2411,11 +2427,11 @@ retry_mapview:;
   } else {
     if (map->filesize != size) {
       if (size > map->filesize) {
-        rc = osal_fallocate(map->fd, size);
-        VERBOSE("f%s-%s %zu, err %d", "allocate", "extend", size, rc);
+        rc = osal_fsetsize(map->fd, size);
+        VERBOSE("osal_fsetsize-%s %zu, err %d", "extend", size, rc);
       } else if (flags & txn_shrink_allowed) {
-        rc = osal_ftruncate(map->fd, size);
-        VERBOSE("f%s-%s %zu, err %d", "truncate", "shrink", size, rc);
+        rc = osal_fsetsize(map->fd, size);
+        VERBOSE("osal_fsetsize-%s %zu, err %d", "shrink", size, rc);
       }
       if (unlikely(rc != MDBX_SUCCESS))
         return rc;

src/osal.h

@@ -433,8 +433,7 @@ enum osal_syncmode_bits {
 };
 
 MDBX_INTERNAL int osal_fsync(mdbx_filehandle_t fd, const enum osal_syncmode_bits mode_bits);
-MDBX_INTERNAL int osal_ftruncate(mdbx_filehandle_t fd, uint64_t length);
-MDBX_INTERNAL int osal_fallocate(mdbx_filehandle_t fd, uint64_t length);
+MDBX_INTERNAL int osal_fsetsize(mdbx_filehandle_t fd, const uint64_t length);
 MDBX_INTERNAL int osal_fseek(mdbx_filehandle_t fd, uint64_t pos);
 MDBX_INTERNAL int osal_filesize(mdbx_filehandle_t fd, uint64_t *length);