RE: [PATCH v5 3/7] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero

-----Original Message----- From: Darrick J. Wong <djwong(a)kernel.org&gt; Subject: Re: [PATCH v5 3/7] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero On Tue, May 11, 2021 at 11:09:29AM +0800, Shiyang Ruan wrote: > Punch hole on a reflinked file needs dax_copy_edge() too. Otherwise, > data in not aligned area will be not correct. So, add the srcmap to > dax_iomap_zero() and replace memset() as dax_copy_edge(). > > Signed-off-by: Shiyang Ruan <ruansy.fnst(a)fujitsu.com&gt; > Reviewed-by: Ritesh Harjani <riteshh(a)linux.ibm.com&gt; > --- > fs/dax.c | 25 +++++++++++++++---------- > fs/iomap/buffered-io.c | 2 +- > include/linux/dax.h | 3 ++- > 3 files changed, 18 insertions(+), 12 deletions(-) > > diff --git a/fs/dax.c b/fs/dax.c > index ef0e564e7904..ee9d28a79bfb 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -1186,7 +1186,8 @@ static vm_fault_t dax_pmd_load_hole(struct > xa_state *xas, struct vm_fault *vmf, } #endif /* CONFIG_FS_DAX_PMD > */ > > -s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap) > +s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap, > + struct iomap *srcmap) > { > sector_t sector = iomap_sector(iomap, pos & PAGE_MASK); > pgoff_t pgoff; > @@ -1208,19 +1209,23 @@ s64 dax_iomap_zero(loff_t pos, u64 length, > struct iomap *iomap) > > if (page_aligned) > rc = dax_zero_page_range(iomap->dax_dev, pgoff, 1); > - else > + else { > rc = dax_direct_access(iomap->dax_dev, pgoff, 1, &kaddr, NULL); > - if (rc < 0) { > - dax_read_unlock(id); > - return rc; > - } > - > - if (!page_aligned) { > - memset(kaddr + offset, 0, size); > + if (rc < 0) > + goto out; > + if (iomap->addr != srcmap->addr) { Why isn't this "if (srcmap->type != IOMAP_HOLE)" ? I suppose it has the same effect, since @iomap should never be a hole and we should never have a @srcmap that's the same as @iomap, but still, we use IOMAP_HOLE checks in most other parts of fs/iomap/.

Other than that, the logic looks decent to me. --D > + rc = dax_iomap_cow_copy(offset, size, PAGE_SIZE, srcmap, > + kaddr); > + if (rc < 0) > + goto out; > + } else > + memset(kaddr + offset, 0, size); > dax_flush(iomap->dax_dev, kaddr + offset, size); > } > + > +out: > dax_read_unlock(id); > - return size; > + return rc < 0 ? rc : size; > } > > static loff_t > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index > f2cd2034a87b..2734955ea67f 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -933,7 +933,7 @@ static loff_t iomap_zero_range_actor(struct inode *inode, loff_t pos, > s64 bytes; > > if (IS_DAX(inode)) > - bytes = dax_iomap_zero(pos, length, iomap); > + bytes = dax_iomap_zero(pos, length, iomap, srcmap); > else > bytes = iomap_zero(inode, pos, length, iomap, srcmap); > if (bytes < 0) > diff --git a/include/linux/dax.h b/include/linux/dax.h index > b52f084aa643..3275e01ed33d 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -237,7 +237,8 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault > *vmf, int dax_delete_mapping_entry(struct address_space *mapping, > pgoff_t index); int dax_invalidate_mapping_entry_sync(struct address_space *mapping, > pgoff_t index); > -s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap); > +s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap, > + struct iomap *srcmap); > static inline bool dax_mapping(struct address_space *mapping) { > return mapping->host && IS_DAX(mapping->host); > -- > 2.31.1 > > >