From: Miklos Szeredi <miklos@szeredi.hu>
To: Alessio Balsini <balsini@android.com>
Cc: Akilesh Kailash <akailash@google.com>,
Amir Goldstein <amir73il@gmail.com>,
Antonio SJ Musumeci <trapexit@spawn.link>,
David Anderson <dvander@google.com>,
Giuseppe Scrivano <gscrivan@redhat.com>,
Jann Horn <jannh@google.com>, Jens Axboe <axboe@kernel.dk>,
Martijn Coenen <maco@android.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Lawrence <paullawrence@google.com>,
Peng Tao <bergwolf@gmail.com>,
Stefano Duo <duostefano93@gmail.com>,
Zimuzo Ezeozue <zezeozue@google.com>, wuyan <wu-yan@tcl.com>,
fuse-devel <fuse-devel@lists.sourceforge.net>,
kernel-team <kernel-team@android.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND V12 5/8] fuse: Introduce synchronous read and write for passthrough
Date: Wed, 17 Feb 2021 15:00:06 +0100 [thread overview]
Message-ID: <CAJfpegtpX93S00LrbChQmC8wc968t5Hd9OFMTrF9g10Hk0E+Zg@mail.gmail.com> (raw)
In-Reply-To: <20210125153057.3623715-6-balsini@android.com>
On Mon, Jan 25, 2021 at 4:31 PM Alessio Balsini <balsini@android.com> wrote:
>
> All the read and write operations performed on fuse_files which have the
> passthrough feature enabled are forwarded to the associated lower file
> system file via VFS.
>
> Sending the request directly to the lower file system avoids the
> userspace round-trip that, because of possible context switches and
> additional operations might reduce the overall performance, especially
> in those cases where caching doesn't help, for example in reads at
> random offsets.
>
> Verifying if a fuse_file has a lower file system file associated with
> can be done by checking the validity of its passthrough_filp pointer.
> This pointer is not NULL only if passthrough has been successfully
> enabled via the appropriate ioctl().
> When a read/write operation is requested for a FUSE file with
> passthrough enabled, a new equivalent VFS request is generated, which
> instead targets the lower file system file.
> The VFS layer performs additional checks that allow for safer operations
> but may cause the operation to fail if the process accessing the FUSE
> file system does not have access to the lower file system.
>
> This change only implements synchronous requests in passthrough,
> returning an error in the case of asynchronous operations, yet covering
> the majority of the use cases.
>
> Signed-off-by: Alessio Balsini <balsini@android.com>
> ---
> fs/fuse/file.c | 8 ++++--
> fs/fuse/fuse_i.h | 2 ++
> fs/fuse/passthrough.c | 57 +++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 65 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 953f3034c375..cddada1e8bd9 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1581,7 +1581,9 @@ 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);
>
> - if (!(ff->open_flags & FOPEN_DIRECT_IO))
> + if (ff->passthrough.filp)
> + return fuse_passthrough_read_iter(iocb, to);
> + else if (!(ff->open_flags & FOPEN_DIRECT_IO))
> return fuse_cache_read_iter(iocb, to);
> else
> return fuse_direct_read_iter(iocb, to);
> @@ -1599,7 +1601,9 @@ 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);
>
> - if (!(ff->open_flags & FOPEN_DIRECT_IO))
> + if (ff->passthrough.filp)
> + return fuse_passthrough_write_iter(iocb, from);
> + else if (!(ff->open_flags & FOPEN_DIRECT_IO))
> return fuse_cache_write_iter(iocb, from);
> else
> return fuse_direct_write_iter(iocb, from);
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index 8d39f5304a11..c4730d893324 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -1239,5 +1239,7 @@ int fuse_passthrough_open(struct fuse_dev *fud,
> int fuse_passthrough_setup(struct fuse_conn *fc, struct fuse_file *ff,
> struct fuse_open_out *openarg);
> void fuse_passthrough_release(struct fuse_passthrough *passthrough);
> +ssize_t fuse_passthrough_read_iter(struct kiocb *iocb, struct iov_iter *to);
> +ssize_t fuse_passthrough_write_iter(struct kiocb *iocb, struct iov_iter *from);
>
> #endif /* _FS_FUSE_I_H */
> diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c
> index cf993e83803e..d949ca07a83b 100644
> --- a/fs/fuse/passthrough.c
> +++ b/fs/fuse/passthrough.c
> @@ -4,6 +4,63 @@
>
> #include <linux/fuse.h>
> #include <linux/idr.h>
> +#include <linux/uio.h>
> +
> +#define PASSTHROUGH_IOCB_MASK \
> + (IOCB_APPEND | IOCB_DSYNC | IOCB_HIPRI | IOCB_NOWAIT | IOCB_SYNC)
> +
> +static void fuse_copyattr(struct file *dst_file, struct file *src_file)
> +{
> + struct inode *dst = file_inode(dst_file);
> + struct inode *src = file_inode(src_file);
> +
> + i_size_write(dst, i_size_read(src));
> +}
Hmm, I see why this is done, yet it's contrary to what's been set out
at the beginning: "All the requests other than reads or writes are
still handled by the userspace FUSE daemon."
Maybe just use fuse_write_update_size() instead of copying the size
from the underlying inode.
> +
> +ssize_t fuse_passthrough_read_iter(struct kiocb *iocb_fuse,
> + struct iov_iter *iter)
> +{
> + ssize_t ret;
> + struct file *fuse_filp = iocb_fuse->ki_filp;
> + struct fuse_file *ff = fuse_filp->private_data;
> + struct file *passthrough_filp = ff->passthrough.filp;
> +
> + if (!iov_iter_count(iter))
> + return 0;
> +
> + ret = vfs_iter_read(passthrough_filp, iter, &iocb_fuse->ki_pos,
> + iocb_to_rw_flags(iocb_fuse->ki_flags,
> + PASSTHROUGH_IOCB_MASK));
Please split this line up into:
rwf = ioctb_to_rw_flags(...);
ret = vfs_iter_read(..., rwf);
> +
> + return ret;
> +}
> +
> +ssize_t fuse_passthrough_write_iter(struct kiocb *iocb_fuse,
> + struct iov_iter *iter)
> +{
> + ssize_t ret;
> + struct file *fuse_filp = iocb_fuse->ki_filp;
> + struct fuse_file *ff = fuse_filp->private_data;
> + struct inode *fuse_inode = file_inode(fuse_filp);
> + struct file *passthrough_filp = ff->passthrough.filp;
> +
> + if (!iov_iter_count(iter))
> + return 0;
> +
> + inode_lock(fuse_inode);
> +
> + file_start_write(passthrough_filp);
> + ret = vfs_iter_write(passthrough_filp, iter, &iocb_fuse->ki_pos,
> + iocb_to_rw_flags(iocb_fuse->ki_flags,
> + PASSTHROUGH_IOCB_MASK));
Same here.
Thanks,
Miklos
next prev parent reply other threads:[~2021-02-17 14:01 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-25 15:30 [PATCH RESEND V12 0/8] fuse: Add support for passthrough read/write Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 1/8] fs: Generic function to convert iocb to rw flags Alessio Balsini
2021-01-25 16:46 ` Alessio Balsini
2021-03-24 7:43 ` Rokudo Yan
2021-03-24 14:02 ` Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 2/8] fuse: 32-bit user space ioctl compat for fuse device Alessio Balsini
[not found] ` <CAMAHBGzkfEd9-1u0iKXp65ReJQgUi_=4sMpmfkwEOaMp6Ux7pg@mail.gmail.com>
2021-01-27 13:40 ` Alessio Balsini
[not found] ` <CAMAHBGwpKW+30kNQ_Apt8A-FTmr94hBOzkT21cjEHHW+t7yUMQ@mail.gmail.com>
2021-01-28 14:15 ` Alessio Balsini
2021-02-05 9:54 ` Peng Tao
2021-03-16 18:57 ` Arnd Bergmann
2021-02-17 10:21 ` Miklos Szeredi
2021-03-01 12:26 ` Alessio Balsini
2021-03-16 18:53 ` Arnd Bergmann
2021-03-18 16:13 ` Alessio Balsini
2021-03-18 21:15 ` Arnd Bergmann
2021-03-19 15:21 ` Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 3/8] fuse: Definitions and ioctl for passthrough Alessio Balsini
2021-02-17 13:41 ` Miklos Szeredi
2021-02-19 7:05 ` Peng Tao
2021-02-19 8:40 ` Miklos Szeredi
2021-03-01 17:05 ` Alessio Balsini
2022-09-08 15:36 ` Amir Goldstein
2022-09-09 19:07 ` Miklos Szeredi
2022-09-10 8:52 ` Amir Goldstein
2022-09-10 13:03 ` Bernd Schubert
2022-09-12 9:29 ` Miklos Szeredi
2022-09-12 12:29 ` Amir Goldstein
2022-09-12 13:03 ` Miklos Szeredi
2022-09-12 13:05 ` Miklos Szeredi
2022-09-12 13:26 ` Amir Goldstein
2022-09-12 14:22 ` Miklos Szeredi
2022-09-12 15:39 ` Amir Goldstein
2022-09-12 17:43 ` Hao Luo
2022-09-12 18:28 ` Overlayfs with writable lower layer Amir Goldstein
2022-09-13 18:26 ` Hao Luo
2022-09-13 18:54 ` Amir Goldstein
2022-09-13 20:33 ` Hao Luo
2022-09-14 3:46 ` Amir Goldstein
2022-09-14 18:00 ` Hao Luo
2022-09-14 19:23 ` Amir Goldstein
2022-09-14 19:33 ` Hao Luo
2022-09-15 10:54 ` Amir Goldstein
2023-05-12 19:37 ` [PATCH RESEND V12 3/8] fuse: Definitions and ioctl for passthrough Amir Goldstein
2023-05-15 7:29 ` Miklos Szeredi
2023-05-15 14:00 ` Amir Goldstein
2023-05-15 20:16 ` [fuse-devel] " Nikolaus Rath
2023-05-15 21:11 ` Bernd Schubert
2023-05-15 21:45 ` Paul Lawrence
2023-05-16 8:43 ` Miklos Szeredi
2023-05-16 10:16 ` Nikolaus Rath
2023-05-16 8:48 ` Amir Goldstein
2021-01-25 15:30 ` [PATCH RESEND V12 4/8] fuse: Passthrough initialization and release Alessio Balsini
2021-02-17 13:52 ` Miklos Szeredi
2021-05-05 12:21 ` Amir Goldstein
2021-05-17 11:36 ` Alessio Balsini
2021-05-17 13:21 ` Amir Goldstein
2021-01-25 15:30 ` [PATCH RESEND V12 5/8] fuse: Introduce synchronous read and write for passthrough Alessio Balsini
2021-02-17 14:00 ` Miklos Szeredi [this message]
2021-01-25 15:30 ` [PATCH RESEND V12 6/8] fuse: Handle asynchronous read and write in passthrough Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 7/8] fuse: Use daemon creds in passthrough mode Alessio Balsini
2021-02-05 9:23 ` Peng Tao
2021-02-05 11:21 ` Alessio Balsini
2021-01-25 15:30 ` [PATCH RESEND V12 8/8] fuse: Introduce passthrough for mmap Alessio Balsini
2021-02-17 14:05 ` Miklos Szeredi
2021-04-01 11:24 ` Alessio Balsini
2021-11-18 18:31 ` [PATCH RESEND V12 0/8] fuse: Add support for passthrough read/write Amir Goldstein
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