On Mon, Jun 22, 2020 at 5:22 PM Goldwyn Rodrigues <rgoldwyn@xxxxxxx> wrote:
>
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> This is to parallelize direct writes within EOF or with direct I/O
> reads. This covers the race with truncate() accidentally increasing the
> filesize.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> ---
> fs/btrfs/file.c | 25 +++++++------------------
> 1 file changed, 7 insertions(+), 18 deletions(-)
>
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index aa6be931620b..c446a4aeb867 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -1957,12 +1957,18 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
> loff_t endbyte;
> int err;
> size_t count = 0;
> - bool relock = false;
> int flags = IOMAP_DIOF_PGINVALID_FAIL;
> int ilock_flags = 0;
>
> if (iocb->ki_flags & IOCB_NOWAIT)
> ilock_flags |= BTRFS_ILOCK_TRY;
> + /*
> + * If the write DIO within EOF, use a shared lock
> + */
> + if (pos + count <= i_size_read(inode))
> + ilock_flags |= BTRFS_ILOCK_SHARED;
> + else if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EAGAIN;
In the next iteration, please rebase the patchset on a more recent misc-next.
That hunk returning -EAGAIN is buggy and was removed a couple weeks
ago in a patchset fixing several bugs with NOWAIT writes.
Thanks.
>
> err = btrfs_inode_lock(inode, ilock_flags);
> if (err < 0)
> @@ -1975,20 +1981,6 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
> if (check_direct_IO(fs_info, from, pos))
> goto buffered;
>
> - count = iov_iter_count(from);
> - /*
> - * If the write DIO is beyond the EOF, we need update the isize, but it
> - * is protected by i_mutex. So we can not unlock the i_mutex at this
> - * case.
> - */
> - if (pos + count <= inode->i_size) {
> - inode_unlock(inode);
> - relock = true;
> - } else if (iocb->ki_flags & IOCB_NOWAIT) {
> - err = -EAGAIN;
> - goto out;
> - }
> -
> if (is_sync_kiocb(iocb))
> flags |= IOMAP_DIOF_WAIT_FOR_COMPLETION;
>
> @@ -1997,9 +1989,6 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
> flags);
> up_read(&BTRFS_I(inode)->dio_sem);
>
> - if (relock)
> - inode_lock(inode);
> -
> if (written < 0 || !iov_iter_count(from)) {
> err = written;
> goto error;
> --
> 2.25.0
>
--
Filipe David Manana,
“Whether you think you can, or you think you can't — you're right.”
