iomap: use a srcmap for a read-modify-write I/O

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@suse.com>
[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@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

diff --git a/fs/dax.c b/fs/dax.c
index 6bf81f931de39e48bc2983a1c901b1a6643443f8..68eef98cd9c4068ffa880aaa7937d34e0052bc15 100644 (file)
--- 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;
@@ -1247,7 +1247,8 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
        struct inode *inode = mapping->host;
        unsigned long vaddr = vmf->address;
        loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
-       struct iomap iomap = { 0 };
+       struct iomap iomap = { .type = IOMAP_HOLE };
+       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) {
@@ -1471,7 +1472,8 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
        unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
        struct inode *inode = mapping->host;
        vm_fault_t result = VM_FAULT_FALLBACK;
-       struct iomap iomap = { 0 };
+       struct iomap iomap = { .type = IOMAP_HOLE };
+       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 7004ce581a328b29eebae9e28e220c9fe5c7bbbb..467c13ff6b40902aea637f2bd7e6fa01df23ec73 100644 (file)
--- 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 516faa280ceda8d8035363f63153bbdac4901002..abaaf7d96ca455a5788fe560b6422b18e3c1bd77 100644 (file)
--- 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 f63df54a08c6c3eb3a4c75aa946936929ce203a3..5161032482725cdbe51901d0a69b822f2e9a7b7d 100644 (file)
--- 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 54c02aecf3cd848825b79a57b57e87e53a1f1e69..484dd8eda861df5408831d3c0f45ebf8cd304e9b 100644 (file)
--- 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 b610768235446cad6e59c0407a9e72f72312e024..c62e807956b6ccecd516093ee6224e54194de2ce 100644 (file)
--- 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 @@ again:
                        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 @@ again:
 
                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 da124cee1783fab256a50760bc4dff9a3a622c5c..49bf9780e3ed225eefccfe6014cfd1584580ac03 100644 (file)
--- 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 f26fdd36e3832b22cbc06a2248b3105e880f20bd..690ef2d7c6c803e802dc4f992eb4687e5994ddd7 100644 (file)
--- 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 c04bad4b2b43f9fbdfc3a3788e36e8dff95ba241..89f61d93c0bcfddad22c6dda6385bdaa4e8da893 100644 (file)
--- a/fs/iomap/seek.c
+++ b/fs/iomap/seek.c
@@ -119,7 +119,7 @@ out:
 
 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 152a230f668d47256f3f27933f757da7380a0c8a..a648dbf6991e4e5307574b7bb207269d7f650321 100644 (file)
--- 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 f7b8b1329ddd108f96bfcc76f3a1a477ceeff808..95719e161286c74a4552c60bc7a1353eb2115173 100644 (file)
--- 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;
@@ -1161,7 +1162,8 @@ 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;
@@ -1247,7 +1249,8 @@ 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 53e6e2275d3d9b74e9df7f1dd0ebcd3fe90a300c..8b09463dae0dba2a4a60ce2372863ba0e8fd16b9 100644 (file)
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -129,7 +129,8 @@ 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.
@@ -145,7 +146,7 @@ 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,