Re: [PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero
On Thu, Sep 16, 2021 at 04:49:19PM +0800, Shiyang Ruan wrote:
>
>
> On 2021/9/16 14:16, Christoph Hellwig wrote:
> > On Wed, Sep 15, 2021 at 06:44:58PM +0800, Shiyang Ruan wrote:
> > > + rc = dax_direct_access(iomap->dax_dev, pgoff, 1, , NULL);
> > > + if (rc < 0)
> > > + goto out;
> > > + memset(kaddr + offset, 0, size);
> > > + if (srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) {
> >
> > Should we also check that ->dax_dev for iomap and srcmap are different
> > first to deal with case of file system with multiple devices?
>
> I have not thought of this case. Isn't it possible to CoW between different
> devices?
There's nothing in the iomap API that prevents a filesystem from doing
that, though there are no filesystems today that do such a thing.
That said, if btrfs ever joins the fold (and adds DAX support) then they
could totally COW to a different device.
--D
>
>
> --
> Thanks,
> Ruan
>
> >
> > Otherwise looks good:
> >
> > Reviewed-by: Christoph Hellwig
> >
>
>
Re: [PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero
On 2021/9/16 14:16, Christoph Hellwig wrote:
On Wed, Sep 15, 2021 at 06:44:58PM +0800, Shiyang Ruan wrote:
+ rc = dax_direct_access(iomap->dax_dev, pgoff, 1, , NULL);
+ if (rc < 0)
+ goto out;
+ memset(kaddr + offset, 0, size);
+ if (srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) {
Should we also check that ->dax_dev for iomap and srcmap are different
first to deal with case of file system with multiple devices?
I have not thought of this case. Isn't it possible to CoW between
different devices?
--
Thanks,
Ruan
Otherwise looks good:
Reviewed-by: Christoph Hellwig
Re: [PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero
On Wed, Sep 15, 2021 at 06:44:58PM +0800, Shiyang Ruan wrote:
> + rc = dax_direct_access(iomap->dax_dev, pgoff, 1, , NULL);
> + if (rc < 0)
> + goto out;
> + memset(kaddr + offset, 0, size);
> + if (srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) {
Should we also check that ->dax_dev for iomap and srcmap are different
first to deal with case of file system with multiple devices?
Otherwise looks good:
Reviewed-by: Christoph Hellwig
[PATCH v9 5/8] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero
Punch hole on a reflinked file needs dax_iomap_cow_copy() too.
Otherwise, data in not aligned area will be not correct. So, add the
CoW operation for not aligned case in dax_iomap_zero().
Signed-off-by: Shiyang Ruan
Reviewed-by: Ritesh Harjani
Reviewed-by: Darrick J. Wong
---
fs/dax.c | 27 +--
1 file changed, 17 insertions(+), 10 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 4f346e25e488..ca4308c85988 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1212,6 +1212,7 @@ static vm_fault_t dax_pmd_load_hole(struct xa_state *xas,
struct vm_fault *vmf,
s64 dax_iomap_zero(struct iomap_iter *iter, loff_t pos, u64 length)
{
const struct iomap *iomap = >iomap;
+ const struct iomap *srcmap = >srcmap;
sector_t sector = iomap_sector(iomap, pos & PAGE_MASK);
pgoff_t pgoff;
long rc, id;
@@ -1230,21 +1231,27 @@ s64 dax_iomap_zero(struct iomap_iter *iter, loff_t pos,
u64 length)
id = dax_read_lock();
- if (page_aligned)
+ if (page_aligned) {
rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1);
- else
- rc = dax_direct_access(iomap->dax_dev, pgoff, 1, , NULL);
- if (rc < 0) {
- dax_read_unlock(id);
- return rc;
+ goto out;
}
- if (!page_aligned) {
- memset(kaddr + offset, 0, size);
+ rc = dax_direct_access(iomap->dax_dev, pgoff, 1, , NULL);
+ if (rc < 0)
+ goto out;
+ memset(kaddr + offset, 0, size);
+ if (srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) {
+ rc = dax_iomap_cow_copy(pos, size, PAGE_SIZE, srcmap,
+ kaddr);
+ if (rc < 0)
+ goto out;
+ dax_flush(iomap->dax_dev, kaddr, PAGE_SIZE);
+ } else
dax_flush(iomap->dax_dev, kaddr + offset, size);
- }
+
+out:
dax_read_unlock(id);
- return size;
+ return rc < 0 ? rc : size;
}
static loff_t dax_iomap_iter(const struct iomap_iter *iomi,
--
2.33.0
