On Fri, Aug 26, 2022 at 9:23 PM Marc-André Lureau <marcandre.lur...@gmail.com> wrote: > > Hi > > On Fri, Aug 26, 2022 at 5:16 PM Bin Meng <bmeng...@gmail.com> wrote: >> >> On Thu, Aug 25, 2022 at 3:59 PM Marc-André Lureau >> <marcandre.lur...@redhat.com> wrote: >> > >> > Hi >> > >> > On Wed, Aug 24, 2022 at 1:43 PM Bin Meng <bmeng...@gmail.com> wrote: >> > > >> > > From: Xuzhou Cheng <xuzhou.ch...@windriver.com> >> > > >> > > The combination of GENERIC_WRITE and FILE_SHARE_READ options does >> > > not allow the same file to be opened again by CreateFile() from >> > > another QEMU process with the same options when the previous QEMU >> > > process still holds the file handle openned. >> > >> > opened >> > >> > > >> > > As per [1] we should add FILE_SHARE_WRITE to the share mode to allow >> > > such use case. This change makes the behavior be consisten with the >> > > POSIX platforms. >> > > >> > >> > consistent >> > >> > > [1] >> > > https://docs.microsoft.com/en-us/windows/win32/fileio/creating-and-opening-files >> > > >> > > Signed-off-by: Xuzhou Cheng <xuzhou.ch...@windriver.com> >> > > Signed-off-by: Bin Meng <bin.m...@windriver.com> >> > > --- >> > >> > >> > What's the benefit to allow multiple processes write access to the >> > same file? It seems it could easily lead to corruption or unexpected >> > results. >> >> This was triggered by running the test_multifd_tcp_cancel() case on >> windows, which cancels the migration, and launches another QEMU >> process to migrate with the same file opened for write. Chances are >> that the previous QEMU process does not quit before the new QEMU >> process runs hence the new one still holds the file handle that does >> not allow shared write permission then the new QEMU process will fail. >> > > Thanks for the details, that's worth to add in commit message imho.
Sure, I can add this in the commit message. > > But can't we fix the test instead to use different paths? > Yeah, the test case fix is here: https://lore.kernel.org/qemu-devel/20220824094029.1634519-42-bmeng...@gmail.com/ I think this patch is still needed as it makes the Windows char-file behavior be consistent with the posix because there is no lock mechanism in posix. Regards, Bin
