[LTP] [PATCH] tst_device: add new tst_dev_sync

[Petr Vorel]

Hi Li, Cyril,

> This broke build with -Werror=implicit-function-declaration [1]:

> ../include/tst_device.h:78:2: error: implicit declaration of function 'syncfs'; did you mean 'sync'? [-Werror=implicit-function-declaration]
> 2770  syncfs(fd);
> 2771  ^~~~~~
> 2772  sync

> The problem is that syncfs() is guarded with __USE_GNU (in glibc, in musl
> directly _GNU_SOURCE), so this requires to use _GNU_SOURCE (before including
> first header).
> Because it's in tst_device.h, we effectively need to build with -D_GNU_SOURCE.
> Is that what we want? Or should we always use tst_syscall(__NR_syncfs, fd)
> (without conditional check #ifndef HAVE_SYNCFS) ?

Or maybe use tst_syscall(__NR_syncfs, fd) in include/tst_device.h and
keep include/lapi/syncfs.h for tests (which would need to define _GNU_SOURCE?).

Kind regards,
Petr

> [1] https://travis-ci.org/linux-test-project/ltp/jobs/634178861