On Fri, Feb 17, 2012 at 08:49:58AM -0500, Anand Avati wrote:
> Implement ->direct_IO() method in aops. The ->direct_IO() method combines
> the existing fuse_direct_read/fuse_direct_write methods to implement
> O_DIRECT functionality.
>
> Reaching ->direct_IO() in the read path via generic_file_aio_read ensures
> proper synchronization with page cache with its existing framework.
>
> Reaching ->direct_IO() in the write path via fuse_file_aio_write is made
> to come via generic_file_direct_write() which makes it play nice with
> the page cache w.r.t other mmap pages etc.
>
> On files marked 'direct_io' by the filesystem server, IO always follows
> the fuse_direct_read/write path. There is no effect of fcntl(O_DIRECT)
> and it always succeeds.
>
> On files not marked with 'direct_io' by the filesystem server, the IO
> path depends on O_DIRECT flag by the application. This can be passed
> at the time of open() as well as via fcntl().
>
> Note that asynchronous O_DIRECT iocb jobs are completed synchronously
> always (this has been the case with FUSE even before this patch)
>
> Signed-off-by: Anand Avati <avati@xxxxxxxxxx>
> ---
>
> Test case:
>
> - concurrent read and write DDs with oflag=direct and iflag=direct set
> in a few writes and a few reads
>
> - artificially decrease 6th parameter to generic_file_direct_write to
> simulate a partial write of the direct IO request and verify proper
> buffered I/O for remaining offset and size with printk's and verify
> write completion at backend
>
> fs/fuse/dir.c | 3 -
> fs/fuse/file.c | 124 ++++++++++++++++++++++++++++++++++++++++++++++++--------
> 2 files changed, 107 insertions(+), 20 deletions(-)
>
All in all it looks good, just one little nit
> diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
> index 2066328..7e5dbd0 100644
> --- a/fs/fuse/dir.c
> +++ b/fs/fuse/dir.c
> @@ -387,9 +387,6 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
> if (fc->no_create)
> return -ENOSYS;
>
> - if (flags & O_DIRECT)
> - return -EINVAL;
> -
> forget = fuse_alloc_forget();
> if (!forget)
> return -ENOMEM;
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 4a199fd..9dd611b 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -194,10 +194,6 @@ int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
> struct fuse_conn *fc = get_fuse_conn(inode);
> int err;
>
> - /* VFS checks this, but only _after_ ->open() */
> - if (file->f_flags & O_DIRECT)
> - return -EINVAL;
> -
> err = generic_file_open(inode, file);
> if (err)
> return err;
> @@ -932,17 +928,23 @@ static ssize_t fuse_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
> struct file *file = iocb->ki_filp;
> struct address_space *mapping = file->f_mapping;
> size_t count = 0;
> + size_t ocount = 0;
> ssize_t written = 0;
> + ssize_t written_buffered = 0;
> struct inode *inode = mapping->host;
> ssize_t err;
> struct iov_iter i;
> + loff_t endbyte = 0;
>
> WARN_ON(iocb->ki_pos != pos);
>
> - err = generic_segment_checks(iov, &nr_segs, &count, VERIFY_READ);
> + ocount = 0;
> + err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
> if (err)
> return err;
>
> + count = ocount;
> +
> mutex_lock(&inode->i_mutex);
> vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
>
> @@ -962,11 +964,36 @@ static ssize_t fuse_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
>
> file_update_time(file);
>
> - iov_iter_init(&i, iov, nr_segs, count, 0);
> - written = fuse_perform_write(file, mapping, &i, pos);
> - if (written >= 0)
> - iocb->ki_pos = pos + written;
> + if (file->f_flags & O_DIRECT) {
> + written = generic_file_direct_write(iocb, iov, &nr_segs,
> + pos, &iocb->ki_pos,
> + count, ocount);
> + if (written < 0 || written == count)
> + goto out;
> +
> + pos += written;
> + count -= written;
> +
> + iov_iter_init(&i, iov, nr_segs, count, written);
> + written_buffered = fuse_perform_write(file, mapping, &i, pos);
> + if (written_buffered < 0) {
> + err = written_buffered;
> + goto out;
> + }
> + endbyte = pos + written_buffered - 1;
>
> + err = filemap_write_and_wait_range(file->f_mapping, pos,
> + endbyte);
> + if (err)
> + goto out;
> + written += written_buffered;
> + iocb->ki_pos = pos + written_buffered;
You need to call invalidate_mapping_pages here to evict the pages from
pagecache, basically copy what __generic_file_aio_write does and you are good to
go. Thanks,
Josef
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