On Fri, Jun 21, 2019 at 05:46:24PM -0700, Darrick J. Wong wrote:
> On Fri, Jun 21, 2019 at 02:28:23PM -0500, Goldwyn Rodrigues wrote:
> > From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> >
> > Introduces a new type IOMAP_COW, which means the data at offset
> > must be read from a srcmap and copied before performing the
> > write on the offset.
> >
> > The srcmap is used to identify where the read is to be performed
> > from. This is passed to iomap->begin(), which is supposed to
> > put in the details for reading, typically set with type IOMAP_READ.
>
> What is IOMAP_READ ?
The lack of flags. Which reminds me that our IOMAP_* types have
pretty much gotten out of hand in how we use some flags that really
are different types vs others that are modifiers. We'll need to clean
this up a bit eventually.
>
> >
> > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> > ---
> > fs/dax.c | 8 +++++---
> > fs/ext2/inode.c | 2 +-
> > fs/ext4/inode.c | 2 +-
> > fs/gfs2/bmap.c | 3 ++-
> > fs/internal.h | 2 +-
> > fs/iomap.c | 31 ++++++++++++++++---------------
> > fs/xfs/xfs_iomap.c | 9 ++++++---
> > include/linux/iomap.h | 4 +++-
> > 8 files changed, 35 insertions(+), 26 deletions(-)
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 2e48c7ebb973..80b9e2599223 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -1078,7 +1078,7 @@ EXPORT_SYMBOL_GPL(__dax_zero_page_range);
> >
> > static loff_t
> > dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > - struct iomap *iomap)
> > + struct iomap *iomap, struct iomap *srcmap)
> > {
> > struct block_device *bdev = iomap->bdev;
> > struct dax_device *dax_dev = iomap->dax_dev;
> > @@ -1236,6 +1236,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
> > unsigned long vaddr = vmf->address;
> > loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
> > struct iomap iomap = { 0 };
> > + struct iomap srcmap = { 0 };
> > unsigned flags = IOMAP_FAULT;
> > int error, major = 0;
> > bool write = vmf->flags & FAULT_FLAG_WRITE;
> > @@ -1280,7 +1281,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
> > * the file system block size to be equal the page size, which means
> > * that we never have to deal with more than a single extent here.
> > */
> > - error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
> > + error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap, &srcmap);
> > if (iomap_errp)
> > *iomap_errp = error;
> > if (error) {
> > @@ -1460,6 +1461,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
> > struct inode *inode = mapping->host;
> > vm_fault_t result = VM_FAULT_FALLBACK;
> > struct iomap iomap = { 0 };
> > + struct iomap srcmap = { 0 };
> > pgoff_t max_pgoff;
> > void *entry;
> > loff_t pos;
> > @@ -1534,7 +1536,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
> > * to look up our filesystem block.
> > */
> > pos = (loff_t)xas.xa_index << PAGE_SHIFT;
> > - error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
> > + error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap, &srcmap);
>
> Line too long?
>
> Also, I guess the DAX and directio write paths will just WARN_ON_ONCE if
> someone feeds them an IOMAP_COW type iomap?
>
> Ah, right, I guess the only filesystems that use iomap directio and
> iomap dax don't support COW. :)
? XFS does iomap based cow for direct I/O. But we don't use IOMAP_COW
yey with this series as far as I can tell.
