On Wed, 2025-07-16 at 14:14 +0200, Amir Goldstein wrote: > > External email : Please do not click links or open attachments until > you have verified the sender or the content. > > > On Wed, Jul 16, 2025 at 1:49 PM Qi Han <hanqi@xxxxxxxx> wrote: > > > > Hi, Amir > > Hi Qi, > > > In the commit [1], performing read/write operations with DIRECT_IO > > on > > a FUSE file path does not trigger FUSE passthrough. I am unclear > > about > > the reason behind this behavior. Is it possible to modify the call > > sequence to support passthrough for files opened with DIRECT_IO? > > Are you talking about files opened by user with O_DIRECT or > files open by server with FOPEN_DIRECT_IO? > > Those are two different things. > IIRC, O_DIRECT to a backing passthrough file should be possible. > > > Thank you! > > > > [1] > > https://lore.kernel.org/all/20240206142453.1906268-7-amir73il@xxxxxxxxx/ > > > > Reported-by: Lei Liu <liulei.rjpt@xxxxxxxx> > > Signed-off-by: Qi Han <hanqi@xxxxxxxx> > > --- > > fs/fuse/file.c | 15 +++++++-------- > > 1 file changed, 7 insertions(+), 8 deletions(-) > > > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > > index 2ddfb3bb6483..689f9ee938f1 100644 > > --- a/fs/fuse/file.c > > +++ b/fs/fuse/file.c > > @@ -1711,11 +1711,11 @@ static ssize_t fuse_file_read_iter(struct > > kiocb *iocb, struct iov_iter *to) > > if (FUSE_IS_DAX(inode)) > > return fuse_dax_read_iter(iocb, to); > > > > - /* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */ > > - if (ff->open_flags & FOPEN_DIRECT_IO) > > - return fuse_direct_read_iter(iocb, to); > > - else if (fuse_file_passthrough(ff)) > > + > > + if (fuse_file_passthrough(ff)) > > return fuse_passthrough_read_iter(iocb, to); > > + else if (ff->open_flags & FOPEN_DIRECT_IO) > > + return fuse_direct_read_iter(iocb, to); > > else > > return fuse_cache_read_iter(iocb, to); > > } > > @@ -1732,11 +1732,10 @@ static ssize_t fuse_file_write_iter(struct > > kiocb *iocb, struct iov_iter *from) > > if (FUSE_IS_DAX(inode)) > > return fuse_dax_write_iter(iocb, from); > > > > - /* FOPEN_DIRECT_IO overrides FOPEN_PASSTHROUGH */ > > - if (ff->open_flags & FOPEN_DIRECT_IO) > > - return fuse_direct_write_iter(iocb, from); > > - else if (fuse_file_passthrough(ff)) > > + if (fuse_file_passthrough(ff)) > > return fuse_passthrough_write_iter(iocb, from); > > + else if (ff->open_flags & FOPEN_DIRECT_IO) > > + return fuse_direct_write_iter(iocb, from); > > else > > return fuse_cache_write_iter(iocb, from); > > } > > -- > > When server requests to open a file with FOPEN_DIRECT_IO, > it affects how FUSE_READ/FUSE_WRITE requests are made. > > When server requests to open a file with FOPEN_PASSTHROUGH, > it means that FUSE_READ/FUSE_WRITE requests are not to be > expected at all, so these two options are somewhat conflicting. > > Therefore, I do not know what you aim to achieve by your patch. > > However, please note this comment in iomode.c: > * A combination of FOPEN_PASSTHROUGH and FOPEN_DIRECT_IO > means that read/write > * operations go directly to the server, but mmap is done on the > backing file. > > So this is a special mode that the server can request in order to do > passthrough mmap but still send FUSE_READ/FUSE_WRITE requests > to the server. Hi Amir, In most cases, when using passthrough, the server shouldn't set FOPEN_DIRECT_IO, since these two options are conceptually conflicting, unless the server specifically wants this special mode (passthrough mmap but still send r/w requests). Is that correct? It can be confusing. Maybe the documentation could clarify this special case, or the passthrough flags for mmap and r/w could be separate... > > What is your use case? What are you trying to achieve that is not > currently possible? > > Thanks, > Amir. > Hi Qi, I just notice that Android's FuseDaemon doesn't seem to recognize this special mode. It sets both FOPEN_DIRECT_IO and FOPEN_PASSTHROUGH when the user sets O_DIRECT and the server has passthrough enabled. If that's your case, I think Android FuseDaemon may need some fixes. Best, Ed Tsai.
