With dax we cannot deal with readpage() etc. So, we create a dax
comparison funciton which is similar with
vfs_dedupe_file_range_compare().
And introduce dax_remap_file_range_prep() for filesystem use.

Signed-off-by: Goldwyn Rodrigues <rgold...@suse.com>
Signed-off-by: Shiyang Ruan <ruansy.f...@fujitsu.com>
---
 fs/dax.c             | 56 ++++++++++++++++++++++++++++++++++++++++++++
 fs/remap_range.c     | 45 ++++++++++++++++++++++++++++-------
 fs/xfs/xfs_reflink.c |  9 +++++--
 include/linux/dax.h  |  4 ++++
 include/linux/fs.h   | 15 ++++++++----
 5 files changed, 115 insertions(+), 14 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 348297b38f76..76f81f1d76ec 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1833,3 +1833,59 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,
        return dax_insert_pfn_mkwrite(vmf, pfn, order);
 }
 EXPORT_SYMBOL_GPL(dax_finish_sync_fault);
+
+static loff_t dax_range_compare_actor(struct inode *ino1, loff_t pos1,
+               struct inode *ino2, loff_t pos2, loff_t len, void *data,
+               struct iomap *smap, struct iomap *dmap)
+{
+       void *saddr, *daddr;
+       bool *same = data;
+       int ret;
+
+       if (smap->type == IOMAP_HOLE && dmap->type == IOMAP_HOLE) {
+               *same = true;
+               return len;
+       }
+
+       if (smap->type == IOMAP_HOLE || dmap->type == IOMAP_HOLE) {
+               *same = false;
+               return 0;
+       }
+
+       ret = dax_iomap_direct_access(smap, pos1, ALIGN(pos1 + len, PAGE_SIZE),
+                                     &saddr, NULL);
+       if (ret < 0)
+               return -EIO;
+
+       ret = dax_iomap_direct_access(dmap, pos2, ALIGN(pos2 + len, PAGE_SIZE),
+                                     &daddr, NULL);
+       if (ret < 0)
+               return -EIO;
+
+       *same = !memcmp(saddr, daddr, len);
+       return len;
+}
+
+int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
+               struct inode *dest, loff_t destoff, loff_t len, bool *is_same,
+               const struct iomap_ops *ops)
+{
+       int id, ret = 0;
+
+       id = dax_read_lock();
+       while (len) {
+               ret = iomap_apply2(src, srcoff, dest, destoff, len, 0, ops,
+                                  is_same, dax_range_compare_actor);
+               if (ret < 0 || !*is_same)
+                       goto out;
+
+               len -= ret;
+               srcoff += ret;
+               destoff += ret;
+       }
+       ret = 0;
+out:
+       dax_read_unlock(id);
+       return ret;
+}
+EXPORT_SYMBOL_GPL(dax_dedupe_file_range_compare);
diff --git a/fs/remap_range.c b/fs/remap_range.c
index 77dba3a49e65..9079390edaf3 100644
--- a/fs/remap_range.c
+++ b/fs/remap_range.c
@@ -14,6 +14,7 @@
 #include <linux/compat.h>
 #include <linux/mount.h>
 #include <linux/fs.h>
+#include <linux/dax.h>
 #include "internal.h"
 
 #include <linux/uaccess.h>
@@ -199,9 +200,9 @@ static void vfs_unlock_two_pages(struct page *page1, struct 
page *page2)
  * Compare extents of two files to see if they are the same.
  * Caller must have locked both inodes to prevent write races.
  */
-static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
-                                        struct inode *dest, loff_t destoff,
-                                        loff_t len, bool *is_same)
+int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
+                                 struct inode *dest, loff_t destoff,
+                                 loff_t len, bool *is_same)
 {
        loff_t src_poff;
        loff_t dest_poff;
@@ -280,6 +281,7 @@ static int vfs_dedupe_file_range_compare(struct inode *src, 
loff_t srcoff,
 out_error:
        return error;
 }
+EXPORT_SYMBOL(vfs_dedupe_file_range_compare);
 
 /*
  * Check that the two inodes are eligible for cloning, the ranges make
@@ -289,9 +291,11 @@ static int vfs_dedupe_file_range_compare(struct inode 
*src, loff_t srcoff,
  * If there's an error, then the usual negative error code is returned.
  * Otherwise returns 0 with *len set to the request length.
  */
-int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
-                                 struct file *file_out, loff_t pos_out,
-                                 loff_t *len, unsigned int remap_flags)
+static int
+__generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
+                               struct file *file_out, loff_t pos_out,
+                               loff_t *len, unsigned int remap_flags,
+                               const struct iomap_ops *ops)
 {
        struct inode *inode_in = file_inode(file_in);
        struct inode *inode_out = file_inode(file_out);
@@ -351,8 +355,15 @@ int generic_remap_file_range_prep(struct file *file_in, 
loff_t pos_in,
        if (remap_flags & REMAP_FILE_DEDUP) {
                bool            is_same = false;
 
-               ret = vfs_dedupe_file_range_compare(inode_in, pos_in,
-                               inode_out, pos_out, *len, &is_same);
+               if (!IS_DAX(inode_in) && !IS_DAX(inode_out))
+                       ret = vfs_dedupe_file_range_compare(inode_in, pos_in,
+                                       inode_out, pos_out, *len, &is_same);
+               else if (IS_DAX(inode_in) && IS_DAX(inode_out) && ops)
+                       ret = dax_dedupe_file_range_compare(inode_in, pos_in,
+                                       inode_out, pos_out, *len, &is_same,
+                                       ops);
+               else
+                       return -EINVAL;
                if (ret)
                        return ret;
                if (!is_same)
@@ -370,6 +381,24 @@ int generic_remap_file_range_prep(struct file *file_in, 
loff_t pos_in,
 
        return ret;
 }
+
+int dax_remap_file_range_prep(struct file *file_in, loff_t pos_in,
+                             struct file *file_out, loff_t pos_out,
+                             loff_t *len, unsigned int remap_flags,
+                             const struct iomap_ops *ops)
+{
+       return __generic_remap_file_range_prep(file_in, pos_in, file_out,
+                                              pos_out, len, remap_flags, ops);
+}
+EXPORT_SYMBOL(dax_remap_file_range_prep);
+
+int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
+                                 struct file *file_out, loff_t pos_out,
+                                 loff_t *len, unsigned int remap_flags)
+{
+       return __generic_remap_file_range_prep(file_in, pos_in, file_out,
+                                              pos_out, len, remap_flags, NULL);
+}
 EXPORT_SYMBOL(generic_remap_file_range_prep);
 
 loff_t do_clone_file_range(struct file *file_in, loff_t pos_in,
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 6fa05fb78189..f5b3a3da36b7 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1308,8 +1308,13 @@ xfs_reflink_remap_prep(
        if (IS_DAX(inode_in) || IS_DAX(inode_out))
                goto out_unlock;
 
-       ret = generic_remap_file_range_prep(file_in, pos_in, file_out, pos_out,
-                       len, remap_flags);
+       if (IS_DAX(inode_in))
+               ret = generic_remap_file_range_prep(file_in, pos_in, file_out,
+                                                   pos_out, len, remap_flags);
+       else
+               ret = dax_remap_file_range_prep(file_in, pos_in, file_out,
+                                               pos_out, len, remap_flags,
+                                               &xfs_read_iomap_ops);
        if (ret || *len == 0)
                goto out_unlock;
 
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 3275e01ed33d..32e1c34349f2 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -239,6 +239,10 @@ int dax_invalidate_mapping_entry_sync(struct address_space 
*mapping,
                                      pgoff_t index);
 s64 dax_iomap_zero(loff_t pos, u64 length, struct iomap *iomap,
                struct iomap *srcmap);
+int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
+                                 struct inode *dest, loff_t destoff,
+                                 loff_t len, bool *is_same,
+                                 const struct iomap_ops *ops);
 static inline bool dax_mapping(struct address_space *mapping)
 {
        return mapping->host && IS_DAX(mapping->host);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index fd47deea7c17..2e6ec5bdf82a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -68,6 +68,7 @@ struct fsverity_info;
 struct fsverity_operations;
 struct fs_context;
 struct fs_parameter_spec;
+struct iomap_ops;
 
 extern void __init inode_init(void);
 extern void __init inode_init_early(void);
@@ -1910,13 +1911,19 @@ extern ssize_t vfs_read(struct file *, char __user *, 
size_t, loff_t *);
 extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
 extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *,
                                   loff_t, size_t, unsigned int);
+typedef int (*compare_range_t)(struct inode *src, loff_t srcpos,
+                              struct inode *dest, loff_t destpos,
+                              loff_t len, bool *is_same);
 extern ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,
                                       struct file *file_out, loff_t pos_out,
                                       size_t len, unsigned int flags);
-extern int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
-                                        struct file *file_out, loff_t pos_out,
-                                        loff_t *count,
-                                        unsigned int remap_flags);
+int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
+                                 struct file *file_out, loff_t pos_out,
+                                 loff_t *count, unsigned int remap_flags);
+int dax_remap_file_range_prep(struct file *file_in, loff_t pos_in,
+                             struct file *file_out, loff_t pos_out,
+                             loff_t *len, unsigned int remap_flags,
+                             const struct iomap_ops *ops);
 extern loff_t do_clone_file_range(struct file *file_in, loff_t pos_in,
                                  struct file *file_out, loff_t pos_out,
                                  loff_t len, unsigned int remap_flags);
-- 
2.30.1


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