Re: [RESEND PATCH v2.1 07/10] iomap: Introduce iomap_apply2() for operations on two files

[Christoph Hellwig]

On Thu, Mar 04, 2021 at 01:41:42PM +0800, Shiyang Ruan wrote:
> Some operations, such as comparing a range of data in two files under
> fsdax mode, requires nested iomap_open()/iomap_end() on two file.  Thus,
> we introduce iomap_apply2() to accept arguments from two files and
> iomap_actor2_t for actions on two files.

I still wonder if adding the iter based iomap API that willy proposed
would be a better fit here.  In that case we might not even need
a special API for the double iteration.
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[RESEND PATCH v2.1 07/10] iomap: Introduce iomap_apply2() for operations on two files

[Shiyang Ruan]

Some operations, such as comparing a range of data in two files under
fsdax mode, requires nested iomap_open()/iomap_end() on two file.  Thus,
we introduce iomap_apply2() to accept arguments from two files and
iomap_actor2_t for actions on two files.

Signed-off-by: Shiyang Ruan 
---
 fs/iomap/apply.c  | 56 +++
 include/linux/iomap.h |  7 +-
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c
index 26ab6563181f..fbc38ce3d5b6 100644
--- a/fs/iomap/apply.c
+++ b/fs/iomap/apply.c
@@ -97,3 +97,59 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, 
unsigned flags,
 
return written ? written : ret;
 }
+
+loff_t
+iomap_apply2(struct inode *ino1, loff_t pos1, struct inode *ino2, loff_t pos2,
+   loff_t length, unsigned int flags, const struct iomap_ops *ops,
+   void *data, iomap_actor2_t actor)
+{
+   struct iomap smap = { .type = IOMAP_HOLE };
+   struct iomap dmap = { .type = IOMAP_HOLE };
+   loff_t written = 0, ret, ret2 = 0;
+   loff_t len1 = length, len2, min_len;
+
+   ret = ops->iomap_begin(ino1, pos1, len1, flags, , NULL);
+   if (ret)
+   goto out_src;
+   if (WARN_ON(smap.offset > pos1)) {
+   written = -EIO;
+   goto out_src;
+   }
+   if (WARN_ON(smap.length == 0)) {
+   written = -EIO;
+   goto out_src;
+   }
+   len2 = min_t(loff_t, len1, smap.length);
+
+   ret = ops->iomap_begin(ino2, pos2, len2, flags, , NULL);
+   if (ret)
+   goto out_dest;
+   if (WARN_ON(dmap.offset > pos2)) {
+   written = -EIO;
+   goto out_dest;
+   }
+   if (WARN_ON(dmap.length == 0)) {
+   written = -EIO;
+   goto out_dest;
+   }
+   min_len = min_t(loff_t, len2, dmap.length);
+
+   written = actor(ino1, pos1, ino2, pos2, min_len, data, , );
+
+out_dest:
+   if (ops->iomap_end)
+   ret2 = ops->iomap_end(ino2, pos2, len2,
+ written > 0 ? written : 0, flags, );
+out_src:
+   if (ops->iomap_end)
+   ret = ops->iomap_end(ino1, pos1, len1,
+written > 0 ? written : 0, flags, );
+
+   if (ret)
+   return written ? written : ret;
+
+   if (ret2)
+   return written ? written : ret2;
+
+   return written;
+}
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 5bd3cac4df9c..913f98897a77 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -148,10 +148,15 @@ struct iomap_ops {
  */
 typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len,
void *data, struct iomap *iomap, struct iomap *srcmap);
-
+typedef loff_t (*iomap_actor2_t)(struct inode *ino1, loff_t pos1,
+   struct inode *ino2, loff_t pos2, loff_t len, void *data,
+   struct iomap *smap, struct iomap *dmap);
 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);
+loff_t iomap_apply2(struct inode *ino1, loff_t pos1, struct inode *ino2,
+   loff_t pos2, loff_t length, unsigned int flags,
+   const struct iomap_ops *ops, void *data, iomap_actor2_t actor);
 
 ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from,
const struct iomap_ops *ops);
-- 
2.30.1


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