在 2025/7/16 20:14, Amir Goldstein 写道:
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.
Hi, Amir
Thank you for your response. I am performing read/write operations on
a file under a FUSE path opened with O_DIRECT, using code similar to [1].
However, it seems that the FUSE daemon adds FOPEN_DIRECT_IO, as Ed
mentioned. I need to further investigate the FUSE daemon code to confirm
the reason behind this behavior.
[1]
fd_in = open(src_path, O_RDONLY | O_DIRECT);
fd_out = open(dst_path, O_WRONLY | O_CREAT | O_TRUNC | O_DIRECT, 0644);
Thanks,
Qi.
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.
What is your use case? What are you trying to achieve that is not
currently possible?
Thanks,
Amir.
