linux-kernel - 回复: [PATCH 1/7] fsdax: Output address in dax_iomap

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Date:   Tue, 23 Feb 2021 01:32:11 +0000
From:   "ruansy.fnst@...itsu.com" <ruansy.fnst@...itsu.com>
To:     Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>
CC:     "darrick.wong@...cle.com" <darrick.wong@...cle.com>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "willy@...radead.org" <willy@...radead.org>,
        "jack@...e.cz" <jack@...e.cz>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
        "ocfs2-devel@....oracle.com" <ocfs2-devel@....oracle.com>,
        "david@...morbit.com" <david@...morbit.com>,
        "hch@....de" <hch@....de>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "rgoldwyn@...e.de" <rgoldwyn@...e.de>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: 回复: [PATCH 1/7] fsdax: Output address in dax_iomap_pfn() and rename it

> hi,
> 
> > Add address output in dax_iomap_pfn() in order to perform a memcpy() in
> > CoW case.  Since this function both output address and pfn, rename it to
> > dax_iomap_direct_access().
> >
> > Signed-off-by: Shiyang Ruan <ruansy.fnst@...fujitsu.com>
> > ---
> >   fs/dax.c | 20 +++++++++++++++-----
> >   1 file changed, 15 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 5b47834f2e1b..b012b2db7ba2 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -998,8 +998,8 @@ static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
> >        return (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9;
> >   }
> >  
> > -static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
> > -                      pfn_t *pfnp)
> > +static int dax_iomap_direct_access(struct iomap *iomap, loff_t pos, size_t size,
> > +             void **kaddr, pfn_t *pfnp)
> >   {
> >        const sector_t sector = dax_iomap_sector(iomap, pos);
> >        pgoff_t pgoff;
> > @@ -1011,11 +1011,13 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
> >                return rc;
> >        id = dax_read_lock();
> >        length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
> > -                                NULL, pfnp);
> > +                                kaddr, pfnp);
> >        if (length < 0) {
> >                rc = length;
> >                goto out;
> >        }
> > +     if (!pfnp)
> Should this be "if (!*pfnp)"?

pfnp may be NULL if we only need a kaddr output.
  `dax_iomap_direct_access(iomap, pos, size, &kaddr, NULL);`

So, it's a NULL pointer check here.


--
Thanks,
Ruan Shiyang.

> 
> Regards,
> Xiaoguang Wang
> > +             goto out_check_addr;
> >        rc = -EINVAL;
> >        if (PFN_PHYS(length) < size)
> >                goto out;
> > @@ -1025,6 +1027,12 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
> >        if (length > 1 && !pfn_t_devmap(*pfnp))
> >                goto out;
> >        rc = 0;
> > +
> > +out_check_addr:
> > +     if (!kaddr)
> > +             goto out;
> > +     if (!*kaddr)
> > +             rc = -EFAULT;
> >   out:
> >        dax_read_unlock(id);
> >        return rc;
>