On 15:57 23/06, Dave Chinner wrote:
> On Mon, Jun 22, 2020 at 10:24:52AM -0500, Goldwyn Rodrigues wrote:
> > From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> >
> > Convert wait_for_completion boolean to flags so we can pass more flags
> > to iomap_dio_rw()
> >
> > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> > ---
> > fs/ext4/file.c | 11 +++++++++--
> > fs/gfs2/file.c | 7 ++++---
> > fs/iomap/direct-io.c | 3 ++-
> > fs/xfs/xfs_file.c | 10 ++++++----
> > fs/zonefs/super.c | 8 ++++++--
> > include/linux/iomap.h | 9 ++++++++-
> > 6 files changed, 35 insertions(+), 13 deletions(-)
> >
> > diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> > index 2a01e31a032c..d20120c4d833 100644
> > --- a/fs/ext4/file.c
> > +++ b/fs/ext4/file.c
> > @@ -53,6 +53,7 @@ static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
> > {
> > ssize_t ret;
> > struct inode *inode = file_inode(iocb->ki_filp);
> > + int flags = 0;
> >
> > if (iocb->ki_flags & IOCB_NOWAIT) {
> > if (!inode_trylock_shared(inode))
> > @@ -74,8 +75,11 @@ static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
> > return generic_file_read_iter(iocb, to);
> > }
> >
> > + if (is_sync_kiocb(iocb))
> > + flags |= IOMAP_DIOF_WAIT_FOR_COMPLETION;
>
> The name of the flag conflates implementation with intent. "wait for
> completion" is the implementation, "synchronous IO" is the intent.
>
> Can you name this <namespace>_SYNCIO, please? Read further below for
> comments on the flag namespace issues...
Yes, sure. I just hope it is not confused with RWF_SYNC.
>
> > ext4_journal_stop(handle);
> > }
> >
> > + if (is_sync_kiocb(iocb) || unaligned_io || extend)
> > + flags |= IOMAP_DIOF_WAIT_FOR_COMPLETION;
>
> Then stuff like this is self documenting:
>
> if (any of this is true)
> IO needs to be issued synchronously
>
> > @@ -767,6 +767,7 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to)
> > size_t count = iov_iter_count(to);
> > struct gfs2_holder gh;
> > ssize_t ret;
> > + int flags = is_sync_kiocb(iocb) ? IOMAP_DIOF_WAIT_FOR_COMPLETION : 0;
> >
> > if (!count)
> > return 0; /* skip atime */
> > @@ -777,7 +778,7 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to)
> > goto out_uninit;
> >
> > ret = iomap_dio_rw(iocb, to, &gfs2_iomap_ops, NULL,
> > - is_sync_kiocb(iocb));
> > + flags);
>
> Why do we need a new flags variable here, but not for other
> conversions that are identical?
>
> Hmmm - you use 3 different methods of calculating flags to pass
> to iomap_dio_rw() in this patchset. Can you pick one method and use
> it for all the code? e.g. make all the code look like this:
>
> int flags = 0;
>
>
> ....
> if (is_sync_kiocb(iocb)
> flags |= IOMAP_DIOF_SYNCIO;
> ret = iomap_dio_rw(....., flags);
> ....
>
> So the setting of the flags is right next to the iomap_dio_rw()
> call and we don't have to go searching for them?
>
I agree. Will change this.
>
> > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> > index ec7b78e6feca..7ed857196a39 100644
> > --- a/fs/iomap/direct-io.c
> > +++ b/fs/iomap/direct-io.c
> > @@ -405,7 +405,7 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
> > ssize_t
> > iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> > const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
> > - bool wait_for_completion)
> > + int dio_flags)
> > {
> > struct address_space *mapping = iocb->ki_filp->f_mapping;
> > struct inode *inode = file_inode(iocb->ki_filp);
> > @@ -415,6 +415,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> > unsigned int flags = IOMAP_DIRECT;
> > struct blk_plug plug;
> > struct iomap_dio *dio;
> > + bool wait_for_completion = !!(dio_flags & IOMAP_DIOF_WAIT_FOR_COMPLETION);
>
> 1. the compiler will squash (x & y) down to a boolean state
> correctly without needing to add double negatives.
>
okay, will change this.
> 2. I don't like variable names shadowing core kernel API functions
> (i.e. wait_for_completion()). Especially as this has nothign to do
> with the completion API...
hmm, the change moves the wait_for_completion from function prototype to
a derived variable in the function. This should be a separate patch and
not combined with this change, if really required. wait_for_completion
is also a variable in struct iomap_dio as well.
>
> > diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> > index 4d1d3c3469e9..f6230446b08d 100644
> > --- a/include/linux/iomap.h
> > +++ b/include/linux/iomap.h
> > @@ -255,9 +255,16 @@ struct iomap_dio_ops {
> > struct bio *bio, loff_t file_offset);
> > };
> >
> > +/*
> > + * Flags to pass iomap_dio_rw()
> > + */
> > +
> > +/* Wait for completion of DIO */
> > +#define IOMAP_DIOF_WAIT_FOR_COMPLETION 0x1
>
> Hmmm. Namespace issues. We already have a IOMAP_DIO_* flags defined
> for passing to ->end_io. It's going to be confusing having a set of
> flags with almost exactly the namespace but with an "F" for flags
> and no indication which iomap operation the flags actually belong to.
>
> This is simples, though:
>
> #define IOMAP_DIO_RWF_SYNCIO (1 << 0)
Agree with this one.
>
> And it might also be worthwhile renaming the ->endio flags to:
>
> #define IOMAP_DIO_ENDIO_UNWRITTEN (1 << 0)
> #define IOMAP_DIO_ENDIO_COW (1 << 1)
>
> So there's no confusion there either.
>
This again should be a separate patch.
I will incorporate the changes relevant to this series.
--
Goldwyn
