On Fri, Feb 26, 2021 at 08:20:25AM +0800, Shiyang Ruan wrote:
> We replace the existing entry to the newly allocated one in case of CoW.
> Also, we mark the entry as PAGECACHE_TAG_TOWRITE so writeback marks this
> entry as writeprotected. This helps us snapshots so new write
> pagefaults after snapshots trigger a CoW.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
> ---
> fs/dax.c | 37 ++++++++++++++++++++++++++-----------
> 1 file changed, 26 insertions(+), 11 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 748dfb89fb41..ec4b733e0b59 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -722,6 +722,9 @@ static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_d
> return 0;
> }
>
> +#define DAX_IF_DIRTY (1 << 0)
> +#define DAX_IF_COW (1 << 1)
> +
> /*
> * By this point grab_mapping_entry() has ensured that we have a locked entry
> * of the appropriate size so we don't have to worry about downgrading PMDs to
> @@ -729,16 +732,19 @@ static int copy_cow_page_dax(struct block_device *bdev, struct dax_device *dax_d
> * already in the tree, we will skip the insertion and just dirty the PMD as
> * appropriate.
> */
> -static void *dax_insert_entry(struct xa_state *xas,
> - struct address_space *mapping, struct vm_fault *vmf,
> - void *entry, pfn_t pfn, unsigned long flags, bool dirty)
> +static void *dax_insert_entry(struct xa_state *xas, struct vm_fault *vmf,
> + void *entry, pfn_t pfn, unsigned long flags,
> + unsigned int insert_flags)
> {
> + struct address_space *mapping = vmf->vma->vm_file->f_mapping;
> void *new_entry = dax_make_entry(pfn, flags);
> + bool dirty = insert_flags & DAX_IF_DIRTY;
> + bool cow = insert_flags & DAX_IF_COW;
>
> if (dirty)
> __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
I still think the __mark_inode_dirty should just be moved into the one
caller that needs it.
