From 2b218f5dbcca5fe728b1852d161d7a21fd02b2f5 Mon Sep 17 00:00:00 2001 From: Fam Zheng Date: Fri, 11 Aug 2017 19:44:47 +0800 Subject: [PATCH 2/2] file-posix: Do runtime check for ofd lock API It is reported that on Windows Subsystem for Linux, ofd operations fail with -EINVAL. In other words, QEMU binary built with system headers that exports F_OFD_SETLK doesn't necessarily run in an environment that actually supports it: $ qemu-system-aarch64 ... -drive file=test.vhdx,if=none,id=hd0 \ -device virtio-blk-pci,drive=hd0 qemu-system-aarch64: -drive file=test.vhdx,if=none,id=hd0: Failed to unlock byte 100 qemu-system-aarch64: -drive file=test.vhdx,if=none,id=hd0: Failed to unlock byte 100 qemu-system-aarch64: -drive file=test.vhdx,if=none,id=hd0: Failed to lock byte 100 As a matter of fact this is not WSL specific. It can happen when running a QEMU compiled against a newer glibc on an older kernel, such as in a containerized environment. Let's do a runtime check to cope with that. Reported-by: Andrew Baumann Reviewed-by: Eric Blake Signed-off-by: Fam Zheng Signed-off-by: Kevin Wolf Upstream-Status: Backport Signed-off-by: Chen Qi --- block/file-posix.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) diff --git a/block/file-posix.c b/block/file-posix.c index f4de022ae0..cb3bfce147 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -457,22 +457,19 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, switch (locking) { case ON_OFF_AUTO_ON: s->use_lock = true; -#ifndef F_OFD_SETLK - fprintf(stderr, - "File lock requested but OFD locking syscall is unavailable, " - "falling back to POSIX file locks.\n" - "Due to the implementation, locks can be lost unexpectedly.\n"); -#endif + if (!qemu_has_ofd_lock()) { + fprintf(stderr, + "File lock requested but OFD locking syscall is " + "unavailable, falling back to POSIX file locks.\n" + "Due to the implementation, locks can be lost " + "unexpectedly.\n"); + } break; case ON_OFF_AUTO_OFF: s->use_lock = false; break; case ON_OFF_AUTO_AUTO: -#ifdef F_OFD_SETLK - s->use_lock = true; -#else - s->use_lock = false; -#endif + s->use_lock = qemu_has_ofd_lock(); break; default: abort(); -- 2.11.0