Re: [PATCH v3 08/10] fsdax: Dedup file range to use a compare function

Ritesh Harjani
2021-04-01T11:12:22Z

On 21/03/19 09:52AM, Shiyang Ruan wrote:
> 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 <rgoldwyn@suse.com>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@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);

shouldn't it take len as the second argument?

> + if (ret < 0)
> + return -EIO;
> +
> + ret = dax_iomap_direct_access(dmap, pos2, ALIGN(pos2 + len, PAGE_SIZE),
> + &daddr, NULL);

ditto.
> + 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)

should we consider to check !is_same check b4?
you should maybe relook at this error handling side of code.
we still return len from actor function but is_same is set to false.
So we are essentially returning ret (positive value), instead should be
returning -EBADE because of !memcmp

> @@ -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))

if (!IS_DAX(inode_in)) no?

> + 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);

Is this used anywhere?

> 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
>
>
>