[RFC PATCH 4/7] fs: dedup file range to use a compare function

Shiyang Ruan
2019-07-31T11:52:22Z

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

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>
---
fs/btrfs/ioctl.c | 11 ++++++--
fs/dax.c | 65 ++++++++++++++++++++++++++++++++++++++++++++
fs/ocfs2/file.c | 2 +-
fs/read_write.c | 11 ++++----
fs/xfs/xfs_reflink.c | 2 +-
include/linux/dax.h | 4 +++
include/linux/fs.h | 8 +++++-
7 files changed, 93 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index cd4e693406a0..8f9c749c4aa6 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3936,6 +3936,7 @@ static int btrfs_remap_file_range_prep(struct file *file_in, loff_t pos_in,
bool same_inode = inode_out == inode_in;
u64 wb_len;
int ret;
+ compare_range_t cmp;

if (!(remap_flags & REMAP_FILE_DEDUP)) {
struct btrfs_root *root_out = BTRFS_I(inode_out)->root;
@@ -3997,8 +3998,14 @@ static int btrfs_remap_file_range_prep(struct file *file_in, loff_t pos_in,
if (ret < 0)
goto out_unlock;

- ret = generic_remap_file_range_prep(file_in, pos_in, file_out, pos_out,
- len, remap_flags);
+ if (IS_DAX(file_inode(file_in)) && IS_DAX(file_inode(file_out)))
+ cmp = btrfs_dax_file_range_compare;
+ else
+ cmp = vfs_dedupe_file_range_compare;
+
+ ret = generic_remap_file_range_prep(file_in, pos_in, file_out,
+ pos_out, len, remap_flags, cmp);
+
if (ret < 0 || *len == 0)
goto out_unlock;

diff --git a/fs/dax.c b/fs/dax.c
index 8eb065a1ec51..8111ba93f4d3 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -39,6 +39,8 @@
#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)
@@ -1817,3 +1819,66 @@ 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 inline void *iomap_address(struct iomap *iomap, loff_t off, loff_t len)
+{
+ loff_t start;
+ void *addr;
+ start = (get_start_sect(iomap->bdev) << 9) + iomap->addr +
+ (off - iomap->offset);
+ dax_direct_access(iomap->dax_dev, PHYS_PFN(start), PHYS_PFN(len),
+ &addr, NULL);
+ return addr;
+}
+
+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) {
+ if (ops->iomap_end)
+ ops->iomap_end(src, srcoff, len, ret, 0, &s_iomap);
+ return ret;
+ }
+ cmp_len = len;
+ 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) {
+ if (ops->iomap_end) {
+ ops->iomap_end(src, srcoff, len, ret, 0, &s_iomap);
+ ops->iomap_end(dest, destoff, len, ret, 0, &d_iomap);
+ }
+ return ret;
+ }
+ cmp_len = MIN(cmp_len, d_iomap.offset + d_iomap.length - destoff);
+
+ saddr = iomap_address(&s_iomap, srcoff, cmp_len);
+ daddr = iomap_address(&d_iomap, destoff, cmp_len);
+
+ same = !memcmp(saddr, daddr, cmp_len);
+ if (!same)
+ break;
+ len -= cmp_len;
+ srcoff += cmp_len;
+ destoff += cmp_len;
+
+ if (ops->iomap_end) {
+ ret = ops->iomap_end(src, srcoff, len, 0, 0, &s_iomap);
+ ret = ops->iomap_end(dest, destoff, len, 0, 0, &d_iomap);
+ }
+ }
+ dax_read_unlock(id);
+ *is_same = same;
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dax_file_range_compare);
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index d640c5f8a85d..9d470306cfc3 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2558,7 +2558,7 @@ 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 61b43ad7608e..c6283802ef1c 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1778,7 +1778,7 @@ static struct page *vfs_dedupe_get_page(struct inode *inode, loff_t offset)
* 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)
{
@@ -1845,6 +1845,7 @@ 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
@@ -1856,7 +1857,8 @@ 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);
@@ -1915,9 +1917,8 @@ 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 680ae7662a78..68e4257cebb0 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1350,7 +1350,7 @@ 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 0dd316a74a29..1370d39c91b6 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -157,6 +157,10 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,
int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
pgoff_t index);
+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);

#ifdef CONFIG_FS_DAX
int __dax_zero_page_range(struct block_device *bdev,
diff --git a/include/linux/fs.h b/include/linux/fs.h
index dd28e7679089..0224503e42ce 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1883,10 +1883,16 @@ 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 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);