Re: [PATCH 2/3] ext4: fix inode rwsem regression

Jan Kara
2019-09-23T10:10:30Z

On Wed 11-09-19 11:45:16, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
>
> This is similar to 942491c9e6d6 ("xfs: fix AIM7 regression")
> Apparently our current rwsem code doesn't like doing the trylock, then
> lock for real scheme. So change our read/write methods to just do the
> trylock for the RWF_NOWAIT case.
>
> Fixes: 728fbc0e10b7 ("ext4: nowait aio support")
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

Thanks for fixing this! The patch looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

BTW, I've also added Ted as ext4 maintainer to CC.

Honza

> ---
> fs/ext4/file.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 70b0438dbc94..d5b2d0cc325d 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -40,11 +40,13 @@ static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
> struct inode *inode = file_inode(iocb->ki_filp);
> ssize_t ret;
>
> - if (!inode_trylock_shared(inode)) {
> - if (iocb->ki_flags & IOCB_NOWAIT)
> + if (iocb->ki_flags & IOCB_NOWAIT) {
> + if (!inode_trylock_shared(inode))
> return -EAGAIN;
> + } else {
> inode_lock_shared(inode);
> }
> +
> /*
> * Recheck under inode lock - at this point we are sure it cannot
> * change anymore
> @@ -190,11 +192,13 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
> struct inode *inode = file_inode(iocb->ki_filp);
> ssize_t ret;
>
> - if (!inode_trylock(inode)) {
> - if (iocb->ki_flags & IOCB_NOWAIT)
> + if (iocb->ki_flags & IOCB_NOWAIT) {
> + if (!inode_trylock(inode))
> return -EAGAIN;
> + } else {
> inode_lock(inode);
> }
> +
> ret = ext4_write_checks(iocb, from);
> if (ret <= 0)
> goto out;
> @@ -233,9 +237,10 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> if (!o_direct && (iocb->ki_flags & IOCB_NOWAIT))
> return -EOPNOTSUPP;
>
> - if (!inode_trylock(inode)) {
> - if (iocb->ki_flags & IOCB_NOWAIT)
> + if (iocb->ki_flags & IOCB_NOWAIT) {
> + if (!inode_trylock(inode))
> return -EAGAIN;
> + } else {
> inode_lock(inode);
> }
>
> --
> 2.16.4
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR