On Mon, 13 Jan 2014, Mike Snitzer wrote:
> On Sat, Jan 11 2014 at 12:29pm -0500,
> Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
>
> > This patch makes dm_bufio_prefetch return 1 on success and 0 on failure.
> > A prefetch failure may happen in case of temporary memory shortage.
> >
> > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> >
> > ---
> > drivers/md/dm-bufio.c | 8 ++++++--
> > drivers/md/dm-bufio.h | 4 ++--
> > 2 files changed, 8 insertions(+), 4 deletions(-)
> >
> > Index: linux-3.13-rc7/drivers/md/dm-bufio.c
> > ===================================================================
> > --- linux-3.13-rc7.orig/drivers/md/dm-bufio.c 2014-01-09 16:11:31.000000000 +0100
> > +++ linux-3.13-rc7/drivers/md/dm-bufio.c 2014-01-09 16:16:43.000000000 +0100
> > @@ -1068,10 +1068,11 @@ void *dm_bufio_new(struct dm_bufio_clien
> > }
> > EXPORT_SYMBOL_GPL(dm_bufio_new);
> >
> > -void dm_bufio_prefetch(struct dm_bufio_client *c,
> > +int dm_bufio_prefetch(struct dm_bufio_client *c,
> > sector_t block, unsigned n_blocks)
> > {
> > struct blk_plug plug;
> > + int success = 1;
> >
> > LIST_HEAD(write_list);
> >
>
> I'd prefer to see a bool used here. Or an actual error code like
> -ENOMEM.
>
> > @@ -1104,13 +1105,16 @@ void dm_bufio_prefetch(struct dm_bufio_c
> > if (!n_blocks)
> > goto flush_plug;
> > dm_bufio_lock(c);
> > - }
> > + } else
> > + success = 0;
>
> Why do you continue to do work if a prefetch failed? Why not return
> early here?
I realized that the patch for the return values was wrong (it would return
0 if some buffers were already prefetched).
And it's not really needed, if dm_bufio_prefetch doesn't do prefetch
because of memory shortage, we can do nothing as dm_bufio_read will read
that buffer anyway.
So, I am sending next 6-patch series, it's the same without the first
patch.
Mikulas
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