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Subject[RFC PATCH 6/8] fs/dax: dedup file range to use a compare function
Date
With dax we cannot deal with readpage() etc. So, we create a
funciton callback to perform the file data comparison and pass
it to generic_remap_file_range_prep() so it can use iomap-based
functions.

This may not be the best way to solve this. Suggestions welcome.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
---
fs/dax.c | 60 ++++++++++++++++++++++++++++++++++++++++++++
fs/ocfs2/file.c | 2 +-
fs/read_write.c | 11 ++++----
fs/xfs/xfs_reflink.c | 2 +-
include/linux/dax.h | 5 ++++
include/linux/fs.h | 9 ++++++-
6 files changed, 81 insertions(+), 8 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 12096edb2569..ab6be7749105 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -31,6 +31,8 @@
#define CREATE_TRACE_POINTS
#include <trace/events/fs_dax.h>

+#define MIN(a, b) (((a) < (b)) ? (a) : (b))
+
static inline unsigned int pe_order(enum page_entry_size pe_size)
{
if (pe_size == PE_SIZE_PTE)
@@ -1942,3 +1944,61 @@ 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);
+
+int dax_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)
+{
+ void *saddr, *daddr;
+ struct iomap s_iomap = {0};
+ struct iomap d_iomap = {0};
+ bool same = true;
+ loff_t cmp_len;
+ int id, ret = 0;
+
+ id = dax_read_lock();
+ while (len) {
+ ret = ops->iomap_begin(src, srcoff, len, 0, &s_iomap, NULL);
+ if (ret < 0)
+ goto out_src;
+ cmp_len = MIN(len, s_iomap.offset + s_iomap.length - srcoff);
+
+ ret = ops->iomap_begin(dest, destoff, cmp_len, 0, &d_iomap, NULL);
+ if (ret < 0)
+ goto out_dest;
+ cmp_len = MIN(cmp_len, d_iomap.offset + d_iomap.length - destoff);
+
+ ret = dax_iomap_direct_access(&s_iomap, srcoff,
+ ALIGN(srcoff + cmp_len, PAGE_SIZE),
+ NULL, &saddr);
+ if (ret < 0)
+ goto out_dest;
+
+ ret = dax_iomap_direct_access(&d_iomap, destoff,
+ ALIGN(destoff + cmp_len, PAGE_SIZE),
+ NULL, &daddr);
+ if (ret < 0)
+ goto out_dest;
+
+ same = !memcmp(saddr, daddr, cmp_len);
+ if (!same)
+ break;
+ len -= cmp_len;
+ srcoff += cmp_len;
+ destoff += cmp_len;
+out_dest:
+ if (ops->iomap_end)
+ ops->iomap_end(dest, destoff, len, 0, 0, &d_iomap);
+out_src:
+ if (ops->iomap_end)
+ ops->iomap_end(src, srcoff, len, 0, 0, &s_iomap);
+
+ if (ret < 0)
+ goto out;
+
+ }
+ *is_same = same;
+out:
+ dax_read_unlock(id);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dax_file_range_compare);
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 6cd5e4924e4d..6fa6e1ac6357 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2591,7 +2591,7 @@ static loff_t ocfs2_remap_file_range(struct file *file_in, loff_t pos_in,
goto out_unlock;

ret = generic_remap_file_range_prep(file_in, pos_in, file_out, pos_out,
- &len, remap_flags);
+ &len, remap_flags, vfs_dedupe_file_range_compare);
if (ret < 0 || len == 0)
goto out_unlock;

diff --git a/fs/read_write.c b/fs/read_write.c
index bbfa9b12b15e..e08875f35f10 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1908,7 +1908,7 @@ 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,
+int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
struct inode *dest, loff_t destoff,
loff_t len, bool *is_same)
{
@@ -1989,6 +1989,7 @@ static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
out_error:
return error;
}
+EXPORT_SYMBOL_GPL(vfs_dedupe_file_range_compare);

/*
* Check that the two inodes are eligible for cloning, the ranges make
@@ -2000,7 +2001,8 @@ static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
*/
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)
+ loff_t *len, unsigned int remap_flags,
+ compare_range_t compare)
{
struct inode *inode_in = file_inode(file_in);
struct inode *inode_out = file_inode(file_out);
@@ -2059,9 +2061,8 @@ 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);
+ ret = (*compare)(inode_in, pos_in,
+ inode_out, pos_out, *len, &is_same);
if (ret)
return ret;
if (!is_same)
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 107bf2a2f344..792217cd1e64 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1338,7 +1338,7 @@ xfs_reflink_remap_prep(
goto out_unlock;

ret = generic_remap_file_range_prep(file_in, pos_in, file_out, pos_out,
- len, remap_flags);
+ len, remap_flags, vfs_dedupe_file_range_compare);
if (ret < 0 || *len == 0)
goto out_unlock;

diff --git a/include/linux/dax.h b/include/linux/dax.h
index 1e2e81c701b6..f8143fe24bf5 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -223,6 +223,11 @@ int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
pgoff_t index);
int dax_iomap_zero(loff_t pos, unsigned offset, unsigned size,
struct iomap *iomap);
+int dax_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 4f6f59b4f22a..959173cdeb05 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1924,13 +1924,20 @@ extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
unsigned long, loff_t *, rwf_t);
extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *,
loff_t, size_t, unsigned int);
+extern int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
+ struct inode *dest, loff_t destoff,
+ loff_t len, bool *is_same);
+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);
+ unsigned int remap_flags,
+ compare_range_t cmp);
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);
--
2.26.2


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