On Tue, Oct 08, 2019 at 09:15:15AM +0200, Christoph Hellwig wrote:
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> The srcmap is used to identify where the read is to be performed from.
> It is passed to ->iomap_begin, which can fill it in if we need to read
> data for partially written blocks from a different location than the
> write target. The srcmap is only supported for buffered writes so far.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
Goldwyn,
Since we've reworked your original patch quite extensively, could you
please have a look at (and if you approve, add an Acked-by) this new(er)
version so we can get this series moving for 5.5?
--D
> [hch: merged two patches, removed the IOMAP_F_COW flag, use iomap as
> srcmap if not set, adjust length down to srcmap end as well]
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/dax.c | 9 ++++--
> fs/ext2/inode.c | 2 +-
> fs/ext4/inode.c | 2 +-
> fs/gfs2/bmap.c | 3 +-
> fs/iomap/apply.c | 25 ++++++++++++----
> fs/iomap/buffered-io.c | 65 +++++++++++++++++++++++-------------------
> fs/iomap/direct-io.c | 2 +-
> fs/iomap/fiemap.c | 4 +--
> fs/iomap/seek.c | 4 +--
> fs/iomap/swapfile.c | 3 +-
> fs/xfs/xfs_iomap.c | 9 ++++--
> include/linux/iomap.h | 5 ++--
> 12 files changed, 80 insertions(+), 53 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 6bf81f931de3..920105457c2c 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1090,7 +1090,7 @@ 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;
> @@ -1248,6 +1248,7 @@ 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 = { .type = IOMAP_HOLE };
> unsigned flags = IOMAP_FAULT;
> int error, major = 0;
> bool write = vmf->flags & FAULT_FLAG_WRITE;
> @@ -1292,7 +1293,7 @@ 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) {
> @@ -1472,6 +1473,7 @@ 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 = { .type = IOMAP_HOLE };
> pgoff_t max_pgoff;
> void *entry;
> loff_t pos;
> @@ -1546,7 +1548,8 @@ 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);
> if (error)
> goto unlock_entry;
>
> diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
> index 7004ce581a32..467c13ff6b40 100644
> --- a/fs/ext2/inode.c
> +++ b/fs/ext2/inode.c
> @@ -801,7 +801,7 @@ int ext2_get_block(struct inode *inode, sector_t iblock,
>
> #ifdef CONFIG_FS_DAX
> static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> - unsigned flags, struct iomap *iomap)
> + unsigned flags, struct iomap *iomap, struct iomap *srcmap)
> {
> unsigned int blkbits = inode->i_blkbits;
> unsigned long first_block = offset >> blkbits;
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 516faa280ced..abaaf7d96ca4 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3407,7 +3407,7 @@ static bool ext4_inode_datasync_dirty(struct inode *inode)
> }
>
> static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> - unsigned flags, struct iomap *iomap)
> + unsigned flags, struct iomap *iomap, struct iomap *srcmap)
> {
> struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> unsigned int blkbits = inode->i_blkbits;
> diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
> index f63df54a08c6..516103248272 100644
> --- a/fs/gfs2/bmap.c
> +++ b/fs/gfs2/bmap.c
> @@ -1149,7 +1149,8 @@ static inline bool gfs2_iomap_need_write_lock(unsigned flags)
> }
>
> static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
> - unsigned flags, struct iomap *iomap)
> + unsigned flags, struct iomap *iomap,
> + struct iomap *srcmap)
> {
> struct gfs2_inode *ip = GFS2_I(inode);
> struct metapath mp = { .mp_aheight = 1, };
> diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c
> index 54c02aecf3cd..484dd8eda861 100644
> --- a/fs/iomap/apply.c
> +++ b/fs/iomap/apply.c
> @@ -23,8 +23,10 @@ loff_t
> iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
> const struct iomap_ops *ops, void *data, iomap_actor_t actor)
> {
> - struct iomap iomap = { 0 };
> + struct iomap iomap = { .type = IOMAP_HOLE };
> + struct iomap srcmap = { .type = IOMAP_HOLE };
> loff_t written = 0, ret;
> + u64 end;
>
> /*
> * Need to map a range from start position for length bytes. This can
> @@ -38,7 +40,7 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
> * expose transient stale data. If the reserve fails, we can safely
> * back out at this point as there is nothing to undo.
> */
> - ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
> + ret = ops->iomap_begin(inode, pos, length, flags, &iomap, &srcmap);
> if (ret)
> return ret;
> if (WARN_ON(iomap.offset > pos))
> @@ -50,15 +52,26 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
> * Cut down the length to the one actually provided by the filesystem,
> * as it might not be able to give us the whole size that we requested.
> */
> - if (iomap.offset + iomap.length < pos + length)
> - length = iomap.offset + iomap.length - pos;
> + end = iomap.offset + iomap.length;
> + if (srcmap.type != IOMAP_HOLE)
> + end = min(end, srcmap.offset + srcmap.length);
> + if (pos + length > end)
> + length = end - pos;
>
> /*
> - * Now that we have guaranteed that the space allocation will succeed.
> + * Now that we have guaranteed that the space allocation will succeed,
> * we can do the copy-in page by page without having to worry about
> * failures exposing transient data.
> + *
> + * To support COW operations, we read in data for partially blocks from
> + * the srcmap if the file system filled it in. In that case we the
> + * length needs to be limited to the earlier of the ends of the iomaps.
> + * If the file system did not provide a srcmap we pass in the normal
> + * iomap into the actors so that they don't need to have special
> + * handling for the two cases.
> */
> - written = actor(inode, pos, length, data, &iomap);
> + written = actor(inode, pos, length, data, &iomap,
> + srcmap.type != IOMAP_HOLE ? &srcmap : &iomap);
>
> /*
> * Now the data has been copied, commit the range we've copied. This
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index ac1bbed71a9b..eb2c6d73a837 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -234,7 +234,7 @@ static inline bool iomap_block_needs_zeroing(struct inode *inode,
>
> static loff_t
> iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> - struct iomap *iomap)
> + struct iomap *iomap, struct iomap *srcmap)
> {
> struct iomap_readpage_ctx *ctx = data;
> struct page *page = ctx->cur_page;
> @@ -382,7 +382,7 @@ iomap_next_page(struct inode *inode, struct list_head *pages, loff_t pos,
>
> static loff_t
> iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
> - void *data, struct iomap *iomap)
> + void *data, struct iomap *iomap, struct iomap *srcmap)
> {
> struct iomap_readpage_ctx *ctx = data;
> loff_t done, ret;
> @@ -402,7 +402,7 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
> ctx->cur_page_in_bio = false;
> }
> ret = iomap_readpage_actor(inode, pos + done, length - done,
> - ctx, iomap);
> + ctx, iomap, srcmap);
> }
>
> return done;
> @@ -582,7 +582,7 @@ iomap_read_page_sync(loff_t block_start, struct page *page, unsigned poff,
>
> static int
> __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> - struct page *page, struct iomap *iomap)
> + struct page *page, struct iomap *srcmap)
> {
> struct iomap_page *iop = iomap_page_create(inode, page);
> loff_t block_size = i_blocksize(inode);
> @@ -605,7 +605,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> (to <= poff || to >= poff + plen))
> continue;
>
> - if (iomap_block_needs_zeroing(inode, iomap, block_start)) {
> + if (iomap_block_needs_zeroing(inode, srcmap, block_start)) {
> if (WARN_ON_ONCE(flags & IOMAP_WRITE_F_UNSHARE))
> return -EIO;
> zero_user_segments(page, poff, from, to, poff + plen);
> @@ -614,7 +614,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> }
>
> status = iomap_read_page_sync(block_start, page, poff, plen,
> - iomap);
> + srcmap);
> if (status)
> return status;
> } while ((block_start += plen) < block_end);
> @@ -624,13 +624,15 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
>
> static int
> iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> - struct page **pagep, struct iomap *iomap)
> + struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
> {
> const struct iomap_page_ops *page_ops = iomap->page_ops;
> struct page *page;
> int status = 0;
>
> BUG_ON(pos + len > iomap->offset + iomap->length);
> + if (srcmap != iomap)
> + BUG_ON(pos + len > srcmap->offset + srcmap->length);
>
> if (fatal_signal_pending(current))
> return -EINTR;
> @@ -648,13 +650,13 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> goto out_no_page;
> }
>
> - if (iomap->type == IOMAP_INLINE)
> - iomap_read_inline_data(inode, page, iomap);
> + if (srcmap->type == IOMAP_INLINE)
> + iomap_read_inline_data(inode, page, srcmap);
> else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
> - status = __block_write_begin_int(page, pos, len, NULL, iomap);
> + status = __block_write_begin_int(page, pos, len, NULL, srcmap);
> else
> status = __iomap_write_begin(inode, pos, len, flags, page,
> - iomap);
> + srcmap);
>
> if (unlikely(status))
> goto out_unlock;
> @@ -740,16 +742,16 @@ iomap_write_end_inline(struct inode *inode, struct page *page,
> }
>
> static int
> -iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
> - unsigned copied, struct page *page, struct iomap *iomap)
> +iomap_write_end(struct inode *inode, loff_t pos, unsigned len, unsigned copied,
> + struct page *page, struct iomap *iomap, struct iomap *srcmap)
> {
> const struct iomap_page_ops *page_ops = iomap->page_ops;
> loff_t old_size = inode->i_size;
> int ret;
>
> - if (iomap->type == IOMAP_INLINE) {
> + if (srcmap->type == IOMAP_INLINE) {
> ret = iomap_write_end_inline(inode, page, iomap, pos, copied);
> - } else if (iomap->flags & IOMAP_F_BUFFER_HEAD) {
> + } else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
> ret = block_write_end(NULL, inode->i_mapping, pos, len, copied,
> page, NULL);
> } else {
> @@ -780,7 +782,7 @@ iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
>
> static loff_t
> iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> - struct iomap *iomap)
> + struct iomap *iomap, struct iomap *srcmap)
> {
> struct iov_iter *i = data;
> long status = 0;
> @@ -814,7 +816,8 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> break;
> }
>
> - status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap);
> + status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap,
> + srcmap);
> if (unlikely(status))
> break;
>
> @@ -825,8 +828,8 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
>
> flush_dcache_page(page);
>
> - status = iomap_write_end(inode, pos, bytes, copied, page,
> - iomap);
> + status = iomap_write_end(inode, pos, bytes, copied, page, iomap,
> + srcmap);
> if (unlikely(status < 0))
> break;
> copied = status;
> @@ -879,7 +882,7 @@ EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
>
> static loff_t
> iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> - struct iomap *iomap)
> + struct iomap *iomap, struct iomap *srcmap)
> {
> long status = 0;
> ssize_t written = 0;
> @@ -888,7 +891,7 @@ iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> if (!(iomap->flags & IOMAP_F_SHARED))
> return length;
> /* don't bother with holes or unwritten extents */
> - if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
> + if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
> return length;
>
> do {
> @@ -897,11 +900,12 @@ iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> struct page *page;
>
> status = iomap_write_begin(inode, pos, bytes,
> - IOMAP_WRITE_F_UNSHARE, &page, iomap);
> + IOMAP_WRITE_F_UNSHARE, &page, iomap, srcmap);
> if (unlikely(status))
> return status;
>
> - status = iomap_write_end(inode, pos, bytes, bytes, page, iomap);
> + status = iomap_write_end(inode, pos, bytes, bytes, page, iomap,
> + srcmap);
> if (unlikely(status <= 0)) {
> if (WARN_ON_ONCE(status == 0))
> return -EIO;
> @@ -940,19 +944,19 @@ iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
> EXPORT_SYMBOL_GPL(iomap_file_unshare);
>
> static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
> - unsigned bytes, struct iomap *iomap)
> + unsigned bytes, struct iomap *iomap, struct iomap *srcmap)
> {
> struct page *page;
> int status;
>
> - status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap);
> + status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap, srcmap);
> if (status)
> return status;
>
> zero_user(page, offset, bytes);
> mark_page_accessed(page);
>
> - return iomap_write_end(inode, pos, bytes, bytes, page, iomap);
> + return iomap_write_end(inode, pos, bytes, bytes, page, iomap, srcmap);
> }
>
> static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
> @@ -964,14 +968,14 @@ static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
>
> static loff_t
> iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
> - void *data, struct iomap *iomap)
> + void *data, struct iomap *iomap, struct iomap *srcmap)
> {
> bool *did_zero = data;
> loff_t written = 0;
> int status;
>
> /* already zeroed? we're done. */
> - if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
> + if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
> return count;
>
> do {
> @@ -983,7 +987,8 @@ iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
> if (IS_DAX(inode))
> status = iomap_dax_zero(pos, offset, bytes, iomap);
> else
> - status = iomap_zero(inode, pos, offset, bytes, iomap);
> + status = iomap_zero(inode, pos, offset, bytes, iomap,
> + srcmap);
> if (status < 0)
> return status;
>
> @@ -1033,7 +1038,7 @@ EXPORT_SYMBOL_GPL(iomap_truncate_page);
>
> static loff_t
> iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
> - void *data, struct iomap *iomap)
> + void *data, struct iomap *iomap, struct iomap *srcmap)
> {
> struct page *page = data;
> int ret;
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 1fc28c2da279..e3ccbf7daaae 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -358,7 +358,7 @@ iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
>
> static loff_t
> iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
> - void *data, struct iomap *iomap)
> + void *data, struct iomap *iomap, struct iomap *srcmap)
> {
> struct iomap_dio *dio = data;
>
> diff --git a/fs/iomap/fiemap.c b/fs/iomap/fiemap.c
> index f26fdd36e383..690ef2d7c6c8 100644
> --- a/fs/iomap/fiemap.c
> +++ b/fs/iomap/fiemap.c
> @@ -44,7 +44,7 @@ static int iomap_to_fiemap(struct fiemap_extent_info *fi,
>
> static loff_t
> iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> - struct iomap *iomap)
> + struct iomap *iomap, struct iomap *srcmap)
> {
> struct fiemap_ctx *ctx = data;
> loff_t ret = length;
> @@ -111,7 +111,7 @@ EXPORT_SYMBOL_GPL(iomap_fiemap);
>
> static loff_t
> iomap_bmap_actor(struct inode *inode, loff_t pos, loff_t length,
> - void *data, struct iomap *iomap)
> + void *data, struct iomap *iomap, struct iomap *srcmap)
> {
> sector_t *bno = data, addr;
>
> diff --git a/fs/iomap/seek.c b/fs/iomap/seek.c
> index c04bad4b2b43..89f61d93c0bc 100644
> --- a/fs/iomap/seek.c
> +++ b/fs/iomap/seek.c
> @@ -119,7 +119,7 @@ page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length,
>
> static loff_t
> iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length,
> - void *data, struct iomap *iomap)
> + void *data, struct iomap *iomap, struct iomap *srcmap)
> {
> switch (iomap->type) {
> case IOMAP_UNWRITTEN:
> @@ -165,7 +165,7 @@ EXPORT_SYMBOL_GPL(iomap_seek_hole);
>
> static loff_t
> iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length,
> - void *data, struct iomap *iomap)
> + void *data, struct iomap *iomap, struct iomap *srcmap)
> {
> switch (iomap->type) {
> case IOMAP_HOLE:
> diff --git a/fs/iomap/swapfile.c b/fs/iomap/swapfile.c
> index 152a230f668d..a648dbf6991e 100644
> --- a/fs/iomap/swapfile.c
> +++ b/fs/iomap/swapfile.c
> @@ -76,7 +76,8 @@ static int iomap_swapfile_add_extent(struct iomap_swapfile_info *isi)
> * distinction between written and unwritten extents.
> */
> static loff_t iomap_swapfile_activate_actor(struct inode *inode, loff_t pos,
> - loff_t count, void *data, struct iomap *iomap)
> + loff_t count, void *data, struct iomap *iomap,
> + struct iomap *srcmap)
> {
> struct iomap_swapfile_info *isi = data;
> int error;
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index c0a492353826..016adcd7dd66 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -928,7 +928,8 @@ xfs_file_iomap_begin(
> loff_t offset,
> loff_t length,
> unsigned flags,
> - struct iomap *iomap)
> + struct iomap *iomap,
> + struct iomap *srcmap)
> {
> struct xfs_inode *ip = XFS_I(inode);
> struct xfs_mount *mp = ip->i_mount;
> @@ -1154,7 +1155,8 @@ xfs_seek_iomap_begin(
> loff_t offset,
> loff_t length,
> unsigned flags,
> - struct iomap *iomap)
> + struct iomap *iomap,
> + struct iomap *srcmap)
> {
> struct xfs_inode *ip = XFS_I(inode);
> struct xfs_mount *mp = ip->i_mount;
> @@ -1240,7 +1242,8 @@ xfs_xattr_iomap_begin(
> loff_t offset,
> loff_t length,
> unsigned flags,
> - struct iomap *iomap)
> + struct iomap *iomap,
> + struct iomap *srcmap)
> {
> struct xfs_inode *ip = XFS_I(inode);
> struct xfs_mount *mp = ip->i_mount;
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 24c784e44274..37af5f9dc722 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -127,7 +127,8 @@ struct iomap_ops {
> * The actual length is returned in iomap->length.
> */
> int (*iomap_begin)(struct inode *inode, loff_t pos, loff_t length,
> - unsigned flags, struct iomap *iomap);
> + unsigned flags, struct iomap *iomap,
> + struct iomap *srcmap);
>
> /*
> * Commit and/or unreserve space previous allocated using iomap_begin.
> @@ -143,7 +144,7 @@ struct iomap_ops {
> * Main iomap iterator function.
> */
> typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len,
> - void *data, struct iomap *iomap);
> + void *data, struct iomap *iomap, struct iomap *srcmap);
>
> loff_t iomap_apply(struct inode *inode, loff_t pos, loff_t length,
> unsigned flags, const struct iomap_ops *ops, void *data,
> --
> 2.20.1
>
