On Sun, Dec 24, 2023 at 12:49 PM Bernd Schubert <bschubert@xxxxxxx> wrote:
>
> So far this is just a helper to remove complex locking
> logic out of fuse_direct_write_iter. Especially needed
> by the next patch in the series to that adds the fuse inode
> cache IO mode and adds in even more locking complexity.
>
> Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/fuse/file.c | 61 ++++++++++++++++++++++++++++----------------------
> 1 file changed, 34 insertions(+), 27 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 546254aaab19f..abc93415ec7e3 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1337,6 +1337,37 @@ static bool fuse_dio_wr_exclusive_lock(struct kiocb *iocb, struct iov_iter *from
> return false;
> }
>
> +static void fuse_dio_lock(struct kiocb *iocb, struct iov_iter *from,
> + bool *exclusive)
> +{
> + struct inode *inode = file_inode(iocb->ki_filp);
> +
> + *exclusive = fuse_dio_wr_exclusive_lock(iocb, from);
> + if (*exclusive) {
> + inode_lock(inode);
> + } else {
> + inode_lock_shared(inode);
> + /*
> + * Previous check was without inode lock and might have raced,
> + * check again.
> + */
> + if (fuse_io_past_eof(iocb, from)) {
> + inode_unlock_shared(inode);
> + inode_lock(inode);
> + *exclusive = true;
> + }
> + }
> +}
> +
> +static void fuse_dio_unlock(struct inode *inode, bool exclusive)
> +{
> + if (exclusive) {
> + inode_unlock(inode);
> + } else {
> + inode_unlock_shared(inode);
> + }
> +}
> +
> static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
> {
> struct file *file = iocb->ki_filp;
> @@ -1601,30 +1632,9 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
> struct inode *inode = file_inode(iocb->ki_filp);
> struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
> ssize_t res;
> - bool exclusive_lock = fuse_dio_wr_exclusive_lock(iocb, from);
> -
> - /*
> - * Take exclusive lock if
> - * - Parallel direct writes are disabled - a user space decision
> - * - Parallel direct writes are enabled and i_size is being extended.
> - * - Shared mmap on direct_io file is supported (FUSE_DIRECT_IO_ALLOW_MMAP).
> - * This might not be needed at all, but needs further investigation.
> - */
> - if (exclusive_lock)
> - inode_lock(inode);
> - else {
> - inode_lock_shared(inode);
> -
> - /*
> - * Previous check was without any lock and might have raced.
> - */
> - if (fuse_dio_wr_exclusive_lock(iocb, from)) {
> - inode_unlock_shared(inode);
> - inode_lock(inode);
> - exclusive_lock = true;
> - }
> - }
> + bool exclusive;
>
> + fuse_dio_lock(iocb, from, &exclusive);
> res = generic_write_checks(iocb, from);
> if (res > 0) {
> if (!is_sync_kiocb(iocb) && iocb->ki_flags & IOCB_DIRECT) {
> @@ -1635,10 +1645,7 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
> fuse_write_update_attr(inode, iocb->ki_pos, res);
> }
> }
> - if (exclusive_lock)
> - inode_unlock(inode);
> - else
> - inode_unlock_shared(inode);
> + fuse_dio_unlock(inode, exclusive);
>
> return res;
> }
> --
> 2.40.1
>
