On Fri, Jul 18, 2025 at 1:32 AM Darrick J. Wong <djwong@xxxxxxxxxx> wrote:
>
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> Implement pagecache IO with iomap, complete with hooks into truncate and
> fallocate so that the fuse server needn't implement disk block zeroing
> of post-EOF and unaligned punch/zero regions.
>
> Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
> ---
> fs/fuse/fuse_i.h | 46 +++
> fs/fuse/fuse_trace.h | 391 ++++++++++++++++++++++++
> include/uapi/linux/fuse.h | 5
> fs/fuse/dir.c | 23 +
> fs/fuse/file.c | 90 +++++-
> fs/fuse/file_iomap.c | 723 +++++++++++++++++++++++++++++++++++++++++++++
> fs/fuse/inode.c | 14 +
> 7 files changed, 1268 insertions(+), 24 deletions(-)
>
>
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index 67e428da4391aa..f33b348d296d5e 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -161,6 +161,13 @@ struct fuse_inode {
>
> /* waitq for direct-io completion */
> wait_queue_head_t direct_io_waitq;
> +
> +#ifdef CONFIG_FUSE_IOMAP
> + /* pending io completions */
> + spinlock_t ioend_lock;
> + struct work_struct ioend_work;
> + struct list_head ioend_list;
> +#endif
> };
This union member you are changing is declared for
/* read/write io cache (regular file only) */
but actually it is also for parallel dio and passthrough mode
IIUC, there should be zero intersection between these io modes and
/* iomap cached fileio (regular file only) */
Right?
So it can use its own union member without increasing fuse_inode size.
Just need to be carefull in fuse_init_file_inode(), fuse_evict_inode() and
fuse_file_io_release() which do not assume a specific inode io mode.
Was it your intention to allow filesystems to configure some inodes to be
in file_iomap mode and other inodes to be in regular cached/direct/passthrough
io modes?
I can't say that I see a big benefit in allowing such setups.
It certainly adds a lot of complication to the test matrix if we allow that.
My instinct is for initial version, either allow only opening files in
FILE_IOMAP or
DIRECT_IOMAP to inodes for a filesystem that supports those modes.
Perhaps later we can allow (and maybe fallback to) FOPEN_DIRECT_IO
(without parallel dio) if a server does not configure IOMAP to some inode
to allow a server to provide the data for a specific inode directly.
fuse_file_io_open/release() can help you manage those restrictions and
set ff->iomode = IOM_FILE_IOMAP when a file is opened for file iomap.
I did not look closely enough to see if file_iomap code ends up setting
ff->iomode = IOM_CACHED/UNCACHED or always remains IOM_NONE.
Thanks,
Amir.
