Required for a coming patch where iohelper will operate on O_DIRECT
fds. There, the user-space memory must be aligned to file system
boundaries (at least 512, but using page-aligned works better, and
some file systems prefer 64k). Made tougher by the fact that
VIR_ALLOC won't work on void *, but posix_memalign won't work on
char * and isn't available everywhere.
This patch makes some simplifying assumptions - namely, output
to an O_DIRECT fd will only be attempted on an empty seekable
file (hence, no need to worry about preserving existing data
on a partial block, and ftruncate will work to undo the effects
of having to round up the size of the last block written), and
input from an O_DIRECT fd will only be attempted on a complete
seekable file with the only possible short read at EOF.
* configure.ac (AC_CHECK_FUNCS_ONCE): Check for posix_memalign.
* src/util/iohelper.c (runIO): Use aligned memory, and handle
quirks of O_DIRECT on last write.
Rather than making the iohelper subject to a race in reopening
the file, it is nicer to pass an already-open fd by inheritance.
The old synopsis form must continue to work - if someone updates
their libvirt package and installs a new libvirt_iohelper but
without restarting the old libvirtd daemon, then the daemon can
still make calls using the old syntax but the new iohelper.
* src/util/iohelper.c (runIO): Split code for open...
(prepare): ...to new function.
(usage): Update synopsis.
(main): Allow alternate calling form.
* src/fdstream.c (virFDStreamOpenFileInternal): Use alternate form.
Enforce the recent flags cleanups - we want to use 'unsigned int flags'
in any of our APIs (except where backwards compatibility is important,
in the public migration APIs), and that all flags are checked for
validity (except when there are stub functions that completely
ignore the flags argument).
There are a few minor tweaks done here to avoid false positives:
signed arguments passed to open() are renamed oflags, and flags
arguments that are legitimately ignored are renamed flags_unused.
* cfg.mk (sc_flags_usage): New rule.
(exclude_file_name_regexp--sc_flags_usage): And a few exemptions.
(sc_flags_debug): Tweak wording.
* src/util/iohelper.c (runIO, main): Rename variable.
* src/util/util.c (virSetInherit): Likewise.
* src/fdstream.h (virFDStreamOpenFile, virFDStreamCreateFile):
Likewise.
* src/fdstream.c (virFDStreamOpenFileInternal)
(virFDStreamOpenFile, virFDStreamCreateFile): Likewise.
* src/util/command.c (virExecWithHook) [WIN32]: Likewise.
* src/util/util.c (virFileOpenAs, virDirCreate) [WIN32]: Likewise.
* src/locking/lock_manager.c (virLockManagerPluginNew)
[!HAVE_DLFCN_H]: Likewise.
* src/locking/lock_driver_nop.c (virLockManagerNopNew)
(virLockManagerNopAddResource, virLockManagerNopAcquire)
(virLockManagerNopRelease, virLockManagerNopInquire): Likewise.
This is needed if we want to transfer a temporary file. If the
transfer is done with iohelper, we might run into a race condition,
where we unlink() file before iohelper is executed.
* src/fdstream.c, src/fdstream.h,
src/util/iohelper.c: Add new option
* src/lxc/lxc_driver.c, src/qemu/qemu_driver.c,
src/storage/storage_driver.c, src/uml/uml_driver.c,
src/xen/xen_driver.c: Expand existing function calls
The O_NONBLOCK flag doesn't work as desired on plain files
or block devices. Introduce an I/O helper program that does
the blocking I/O operations, communicating over a pipe that
can support O_NONBLOCK
* src/fdstream.c, src/fdstream.h: Add non-blocking I/O
on plain files/block devices
* src/Makefile.am, src/util/iohelper.c: I/O helper program
* src/qemu/qemu_driver.c, src/lxc/lxc_driver.c,
src/uml/uml_driver.c, src/xen/xen_driver.c: Update for
streams API change
