On Montag, 7. Februar 2022 22:07:34 CET Will Cohen wrote: > On Mon, Feb 7, 2022 at 9:21 AM Christian Schoenebeck > <qemu_...@crudebyte.com> > wrote: > > On Montag, 7. Februar 2022 11:57:25 CET Dr. David Alan Gilbert wrote: > > > * Greg Kurz (gr...@kaod.org) wrote: > > > > On Mon, 7 Feb 2022 11:30:18 +0100 > > > > > > > > Philippe Mathieu-Daudé <f4...@amsat.org> wrote: > > > > > On 7/2/22 09:47, Greg Kurz wrote: > > > > > > On Sun, 6 Feb 2022 20:10:23 -0500 > > > > > > > > > > > > Will Cohen <wwco...@gmail.com> wrote: > > > > > >> This patch set currently places it in 9p-util only because 9p is > > > > the > > > > > > > >> only > > > > > >> place where this issue seems to have come up so far and we were > > > > wary > > > > > > > >> of > > > > > >> editing files too far afield, but I have no attachment to its > > > > > >> specific > > > > > >> location! > > > > > > > > > > > > Inline comments are preferred on qemu-devel. Please don't top post > > > > ! > > > > > > > > This complicates the review a lot. > > > > > > > > > > > > This is indeed a good candidate for osdep. This being said, unless > > > > > > there's > > > > > > some other user in the QEMU code base, it is acceptable to leave > > > > > > it > > > > > > under > > > > > > 9pfs. > > > > > > > > > > virtiofsd could eventually use it. > > > > > > > > Indeed but virtiofsd is for linux hosts only AFAICT and I'm not aware > > > > of > > > > > > any work to support any other host OS. > > > > > > > > Cc'ing virtio-fs people for inputs on this topic. > > > > > > Indeeed, there's a lot of Linux specific code in the virtiofsd - I know > > > people are interested in other platforms, but I'm not sure that's the > > > right starting point. > > > > > > Dave > > > > Agreeing with Greg here: i.e. I would have placed this into osdep, but I > > would > > not insist on it either. > > > > Best regards, > > Christian Schoenebeck > > This makes sense. A revised version of this patch, moving qemu_mknodat from > 9p-util to osdep and os-posix, is attached below. I'd appreciate any > feedback from those looped in here, so that the context isn't lost before > resubmitting as a v5 patch, especially since this is starting to touch > files outside of 9p. > > From c9713c87163da7c96b5357d0d85ac318ae3d3051 Mon Sep 17 00:00:00 2001 > From: Keno Fischer <k...@juliacomputing.com> > Date: Sat, 16 Jun 2018 20:56:55 -0400 > Subject: [PATCH] 9p: darwin: Implement compatibility for mknodat > > Darwin does not support mknodat. However, to avoid race conditions > with later setting the permissions, we must avoid using mknod on > the full path instead. We could try to fchdir, but that would cause > problems if multiple threads try to call mknodat at the same time. > However, luckily there is a solution: Darwin includes a function > that sets the cwd for the current thread only. > This should suffice to use mknod safely. > > This function (pthread_fchdir_np) is protected by a check in > meson in a patch later in tihs series. > > Signed-off-by: Keno Fischer <k...@juliacomputing.com> > Signed-off-by: Michael Roitzsch <reactorcont...@icloud.com> > [Will Cohen: - Adjust coding style > - Replace clang references with gcc > - Note radar filed with Apple for missing syscall > - Replace direct syscall with pthread_fchdir_np and > adjust patch notes accordingly > - Move qemu_mknodat from 9p-util to osdep and os-posix] > Signed-off-by: Will Cohen <wwco...@gmail.com> > --- > hw/9pfs/9p-local.c | 4 ++-- > include/qemu/osdep.h | 10 ++++++++++ > os-posix.c | 34 ++++++++++++++++++++++++++++++++++ > 3 files changed, 46 insertions(+), 2 deletions(-) > > diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c > index a0d08e5216..d42ce6d8b8 100644 > --- a/hw/9pfs/9p-local.c > +++ b/hw/9pfs/9p-local.c > @@ -682,7 +682,7 @@ static int local_mknod(FsContext *fs_ctx, V9fsPath > *dir_path, > > if (fs_ctx->export_flags & V9FS_SM_MAPPED || > fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) { > - err = mknodat(dirfd, name, fs_ctx->fmode | S_IFREG, 0); > + err = qemu_mknodat(dirfd, name, fs_ctx->fmode | S_IFREG, 0); > if (err == -1) { > goto out; > } > @@ -697,7 +697,7 @@ static int local_mknod(FsContext *fs_ctx, V9fsPath > *dir_path, > } > } else if (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH || > fs_ctx->export_flags & V9FS_SM_NONE) { > - err = mknodat(dirfd, name, credp->fc_mode, credp->fc_rdev); > + err = qemu_mknodat(dirfd, name, credp->fc_mode, credp->fc_rdev); > if (err == -1) { > goto out; > } > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > index d1660d67fa..f3a8367ece 100644 > --- a/include/qemu/osdep.h > +++ b/include/qemu/osdep.h > @@ -810,3 +810,13 @@ static inline int > platform_does_not_support_system(const char *command) > #endif > > #endif > + > +/* > + * As long as mknodat is not available on macOS, this workaround > + * using pthread_fchdir_np is needed. qemu_mknodat is defined in > + * os-posix.c > + */ > +#ifdef CONFIG_DARWIN > +int pthread_fchdir_np(int fd); > +#endif
I would make that: #ifdef CONFIG_DARWIN int pthread_fchdir_np(int fd) API_AVAILABLE(macosx(10.12)); #endif here and ... > +int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev); > diff --git a/os-posix.c b/os-posix.c > index ae6c9f2a5e..95c1607065 100644 > --- a/os-posix.c > +++ b/os-posix.c > @@ -24,6 +24,7 @@ > */ > > #include "qemu/osdep.h" > +#include <os/availability.h> > #include <sys/wait.h> > #include <pwd.h> > #include <grp.h> > @@ -332,3 +333,36 @@ int os_mlock(void) > return -ENOSYS; > #endif > } > + > +/* > + * As long as mknodat is not available on macOS, this workaround > + * using pthread_fchdir_np is needed. > + * > + * Radar filed with Apple for implementing mknodat: > + * rdar://FB9862426 (https://openradar.appspot.com/FB9862426) > + */ > +#ifdef CONFIG_DARWIN > + > +int pthread_fchdir_np(int fd) API_AVAILABLE(macosx(10.12)); ... drop the duplicate declaration of pthread_fchdir_np() here. > + > +int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev) > +{ > + int preserved_errno, err; > + if (pthread_fchdir_np(dirfd) < 0) { > + return -1; > + } > + err = mknod(filename, mode, dev); > + preserved_errno = errno; > + /* Stop using the thread-local cwd */ > + pthread_fchdir_np(-1); > + if (err < 0) { > + errno = preserved_errno; > + } > + return err; > +} > +#else > +int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev) > +{ > + return mknodat(dirfd, filename, mode, dev); > +} > +#endif