On Sun, Dec 24, 2023 at 12:49 PM Bernd Schubert <bschubert@xxxxxxx> wrote:
>
> This makes the code a bit easier to read and allows to more
> easily add more conditions when an exclusive lock is needed.
>
> Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/fuse/file.c | 64 +++++++++++++++++++++++++++++++++++---------------
> 1 file changed, 45 insertions(+), 19 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 174aa16407c4b..546254aaab19f 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1298,6 +1298,45 @@ static ssize_t fuse_perform_write(struct kiocb *iocb, struct iov_iter *ii)
> return res;
> }
>
> +static bool fuse_io_past_eof(struct kiocb *iocb, struct iov_iter *iter)
> +{
> + struct inode *inode = file_inode(iocb->ki_filp);
> +
> + return iocb->ki_pos + iov_iter_count(iter) > i_size_read(inode);
> +}
> +
> +/*
> + * @return true if an exclusive lock for direct IO writes is needed
> + */
> +static bool fuse_dio_wr_exclusive_lock(struct kiocb *iocb, struct iov_iter *from)
> +{
> + struct file *file = iocb->ki_filp;
> + struct fuse_file *ff = file->private_data;
> + struct inode *inode = file_inode(iocb->ki_filp);
> +
> + /* server side has to advise that it supports parallel dio writes */
> + if (!(ff->open_flags & FOPEN_PARALLEL_DIRECT_WRITES))
> + return true;
> +
> + /* append will need to know the eventual eof - always needs an
> + * exclusive lock
> + */
> + if (iocb->ki_flags & IOCB_APPEND)
> + return true;
> +
> + /* combination opf page access and direct-io difficult, shared
> + * locks actually introduce a conflict.
> + */
> + if (get_fuse_conn(inode)->direct_io_allow_mmap)
> + return true;
> +
> + /* parallel dio beyond eof is at least for now not supported */
> + if (fuse_io_past_eof(iocb, from))
> + return true;
> +
> + return false;
> +}
> +
> static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
> {
> struct file *file = iocb->ki_filp;
> @@ -1557,26 +1596,12 @@ static ssize_t fuse_direct_read_iter(struct kiocb *iocb, struct iov_iter *to)
> return res;
> }
>
> -static bool fuse_direct_write_extending_i_size(struct kiocb *iocb,
> - struct iov_iter *iter)
> -{
> - struct inode *inode = file_inode(iocb->ki_filp);
> -
> - return iocb->ki_pos + iov_iter_count(iter) > i_size_read(inode);
> -}
> -
> static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
> {
> struct inode *inode = file_inode(iocb->ki_filp);
> - struct file *file = iocb->ki_filp;
> - struct fuse_file *ff = file->private_data;
> struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
> ssize_t res;
> - bool exclusive_lock =
> - !(ff->open_flags & FOPEN_PARALLEL_DIRECT_WRITES) ||
> - get_fuse_conn(inode)->direct_io_allow_mmap ||
> - iocb->ki_flags & IOCB_APPEND ||
> - fuse_direct_write_extending_i_size(iocb, from);
> + bool exclusive_lock = fuse_dio_wr_exclusive_lock(iocb, from);
>
> /*
> * Take exclusive lock if
> @@ -1590,10 +1615,10 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
> else {
> inode_lock_shared(inode);
>
> - /* A race with truncate might have come up as the decision for
> - * the lock type was done without holding the lock, check again.
> + /*
> + * Previous check was without any lock and might have raced.
> */
> - if (fuse_direct_write_extending_i_size(iocb, from)) {
> + if (fuse_dio_wr_exclusive_lock(iocb, from)) {
> inode_unlock_shared(inode);
> inode_lock(inode);
> exclusive_lock = true;
> @@ -2467,7 +2492,8 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
> return fuse_dax_mmap(file, vma);
>
> if (ff->open_flags & FOPEN_DIRECT_IO) {
> - /* Can't provide the coherency needed for MAP_SHARED
> + /*
> + * Can't provide the coherency needed for MAP_SHARED
> * if FUSE_DIRECT_IO_ALLOW_MMAP isn't set.
> */
> if ((vma->vm_flags & VM_MAYSHARE) && !fc->direct_io_allow_mmap)
> --
> 2.40.1
>
