Remove sync_file_range()

After hearing horror stories from a trusted colleague, I don't think
this is the kind of API we want to be supporting. Also SQLite wisdom
regarding fdatasync() has been added to the documentation.

libc/calls/calls.h

@@ -201,7 +201,6 @@ int setresuid(unsigned, unsigned, unsigned);
 int getresgid(unsigned *, unsigned *, unsigned *);
 int getresuid(unsigned *, unsigned *, unsigned *);
 char *get_current_dir_name(void) __wur;
-int sync_file_range(int, int64_t, int64_t, unsigned);
 ssize_t splice(int, int64_t *, int, int64_t *, size_t, unsigned);
 int memfd_create(const char *, unsigned int);
 int execvpe(const char *, char *const[], char *const[]);

libc/calls/fdatasync.c

@@ -29,6 +29,11 @@
 /**
  * Blocks until kernel flushes non-metadata buffers for fd to disk.
  *
+ * NOTE: For `IsXnu()` it's recommended that `fcntl(F_FULLFSYNC)` be
+ * favored instead of this function, and if that fails, the fallback
+ * path should call `fsync()` see the SQLite codebase. In the future
+ * Cosmopolitan might do this automatically.
+ *
  * @return 0 on success, or -1 w/ errno
  * @raise ECANCELED if thread was cancelled in masked mode
  * @raise EROFS if `fd` is on a read-only filesystem e.g. /zip
@@ -37,8 +42,8 @@
  * @raise EBADF if `fd` isn't an open file
  * @raise EINTR if signal was delivered
  * @raise EIO if an i/o error happened
- * @see sync(), fsync(), sync_file_range()
  * @see __nosync to secretly disable
+ * @see sync(), fsync()
  * @cancelationpoint
  * @asyncsignalsafe
  */

libc/calls/fsync.c

@@ -37,8 +37,8 @@
  * @raise EBADF if `fd` isn't an open file
  * @raise EINTR if signal was delivered
  * @raise EIO if an i/o error happened
- * @see fdatasync(), sync_file_range()
  * @see __nosync to secretly disable
+ * @see fdatasync()
  * @cancelationpoint
  * @asyncsignalsafe
  */

libc/calls/sync_file_range.c

@@ -1,44 +0,0 @@
-/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
-│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
-╞══════════════════════════════════════════════════════════════════════════════╡
-│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
-│                                                                              │
-│ Permission to use, copy, modify, and/or distribute this software for         │
-│ any purpose with or without fee is hereby granted, provided that the         │
-│ above copyright notice and this permission notice appear in all copies.      │
-│                                                                              │
-│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
-│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
-│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
-│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
-│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
-│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
-│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
-│ PERFORMANCE OF THIS SOFTWARE.                                                │
-╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/calls/calls.h"
-#include "libc/calls/syscall-sysv.internal.h"
-#include "libc/errno.h"
-
-/**
- * Flushes subset of file to disk.
- *
- * @param offset is page rounded
- * @param bytes is page rounded; 0 means until EOF
- * @param flags can have SYNC_FILE_RANGE_{WAIT_BEFORE,WRITE,WAIT_AFTER}
- * @note Linux documentation says this call is "dangerous"; for highest
- *     assurance of data recovery after crash, consider fsync() on both
- *     file and directory
- * @see fsync(), fdatasync()
- */
-int sync_file_range(int fd, int64_t offset, int64_t bytes, unsigned flags) {
-  int rc, olderr;
-  olderr = errno;
-  if ((rc = sys_sync_file_range(fd, offset, bytes, flags)) != -1 ||
-      errno != ENOSYS) {
-    return rc;
-  } else {
-    errno = olderr;
-    return fdatasync(fd);
-  }
-}

libc/calls/syscall-sysv.internal.h

@@ -108,7 +108,6 @@ i32 sys_sigaction(i32, const void *, void *, i64, i64);
 i32 sys_sigaltstack(const void *, void *);
 i32 sys_symlinkat(const char *, i32, const char *);
 i32 sys_sync(void);
-i32 sys_sync_file_range(i32, i64, i64, u32);
 i32 sys_syncfs(i32);
 i32 sys_syslog(i32, char *, i32);
 i32 sys_tgkill(i32, i32, i32);