linux-kernel - Re: [PATCH] ocfs2: Remove custom swap functions in favor of built-in sort swap

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Message-ID: <a4b3ab50-02af-42f2-b937-dcbb92b4f0d2@suse.com>
Date: Sun, 18 Aug 2024 19:36:18 +0800
From: Heming Zhao <heming.zhao@...e.com>
To: Kuan-Wei Chiu <visitorckw@...il.com>, mark@...heh.com,
 jlbec@...lplan.org, joseph.qi@...ux.alibaba.com
Cc: jserv@...s.ncku.edu.tw, ocfs2-devel@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ocfs2: Remove custom swap functions in favor of built-in
 sort swap

On 8/11/24 03:53, Kuan-Wei Chiu wrote:
> The custom swap functions used in ocfs2 do not perform any special
> operations and can be replaced with the built-in swap function of sort.
> This change not only reduces code size but also improves efficiency,
> especially in scenarios where CONFIG_RETPOLINE is enabled, as it makes
> indirect function calls more expensive.
> 
> By using the built-in swap, we avoid these costly indirect function
> calls, leading to better performance.
> 
> Signed-off-by: Kuan-Wei Chiu <visitorckw@...il.com>

Looks good to me
Signed-off-by: Heming Zhao <heming.zhao@...e.com>

> ---
> Note: Build test only.
> 
>   fs/ocfs2/dir.c          | 12 +-----------
>   fs/ocfs2/refcounttree.c | 13 +++----------
>   fs/ocfs2/xattr.c        | 15 +++------------
>   3 files changed, 7 insertions(+), 33 deletions(-)
> 
> diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
> index f0beb173dbba..fa5d0819a997 100644
> --- a/fs/ocfs2/dir.c
> +++ b/fs/ocfs2/dir.c
> @@ -3511,16 +3511,6 @@ static int dx_leaf_sort_cmp(const void *a, const void *b)
>   	return 0;
>   }
>   
> -static void dx_leaf_sort_swap(void *a, void *b, int size)
> -{
> -	struct ocfs2_dx_entry *entry1 = a;
> -	struct ocfs2_dx_entry *entry2 = b;
> -
> -	BUG_ON(size != sizeof(*entry1));
> -
> -	swap(*entry1, *entry2);
> -}
> -
>   static int ocfs2_dx_leaf_same_major(struct ocfs2_dx_leaf *dx_leaf)
>   {
>   	struct ocfs2_dx_entry_list *dl_list = &dx_leaf->dl_list;
> @@ -3781,7 +3771,7 @@ static int ocfs2_dx_dir_rebalance(struct ocfs2_super *osb, struct inode *dir,
>   	 */
>   	sort(dx_leaf->dl_list.de_entries, num_used,
>   	     sizeof(struct ocfs2_dx_entry), dx_leaf_sort_cmp,
> -	     dx_leaf_sort_swap);
> +	     NULL);
>   
>   	ocfs2_journal_dirty(handle, dx_leaf_bh);
>   
> diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
> index 1f303b1adf1a..4f85508538fc 100644
> --- a/fs/ocfs2/refcounttree.c
> +++ b/fs/ocfs2/refcounttree.c
> @@ -1392,13 +1392,6 @@ static int cmp_refcount_rec_by_cpos(const void *a, const void *b)
>   	return 0;
>   }
>   
> -static void swap_refcount_rec(void *a, void *b, int size)
> -{
> -	struct ocfs2_refcount_rec *l = a, *r = b;
> -
> -	swap(*l, *r);
> -}
> -
>   /*
>    * The refcount cpos are ordered by their 64bit cpos,
>    * But we will use the low 32 bit to be the e_cpos in the b-tree.
> @@ -1474,7 +1467,7 @@ static int ocfs2_divide_leaf_refcount_block(struct buffer_head *ref_leaf_bh,
>   	 */
>   	sort(&rl->rl_recs, le16_to_cpu(rl->rl_used),
>   	     sizeof(struct ocfs2_refcount_rec),
> -	     cmp_refcount_rec_by_low_cpos, swap_refcount_rec);
> +	     cmp_refcount_rec_by_low_cpos, NULL);
>   
>   	ret = ocfs2_find_refcount_split_pos(rl, &cpos, &split_index);
>   	if (ret) {
> @@ -1499,11 +1492,11 @@ static int ocfs2_divide_leaf_refcount_block(struct buffer_head *ref_leaf_bh,
>   
>   	sort(&rl->rl_recs, le16_to_cpu(rl->rl_used),
>   	     sizeof(struct ocfs2_refcount_rec),
> -	     cmp_refcount_rec_by_cpos, swap_refcount_rec);
> +	     cmp_refcount_rec_by_cpos, NULL);
>   
>   	sort(&new_rl->rl_recs, le16_to_cpu(new_rl->rl_used),
>   	     sizeof(struct ocfs2_refcount_rec),
> -	     cmp_refcount_rec_by_cpos, swap_refcount_rec);
> +	     cmp_refcount_rec_by_cpos, NULL);
>   
>   	*split_cpos = cpos;
>   	return 0;
> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> index 35c0cc2a51af..0e58a5ce539e 100644
> --- a/fs/ocfs2/xattr.c
> +++ b/fs/ocfs2/xattr.c
> @@ -4167,15 +4167,6 @@ static int cmp_xe(const void *a, const void *b)
>   	return 0;
>   }
>   
> -static void swap_xe(void *a, void *b, int size)
> -{
> -	struct ocfs2_xattr_entry *l = a, *r = b, tmp;
> -
> -	tmp = *l;
> -	memcpy(l, r, sizeof(struct ocfs2_xattr_entry));
> -	memcpy(r, &tmp, sizeof(struct ocfs2_xattr_entry));
> -}
> -
>   /*
>    * When the ocfs2_xattr_block is filled up, new bucket will be created
>    * and all the xattr entries will be moved to the new bucket.
> @@ -4241,7 +4232,7 @@ static void ocfs2_cp_xattr_block_to_bucket(struct inode *inode,
>   	trace_ocfs2_cp_xattr_block_to_bucket_end(offset, size, off_change);
>   
>   	sort(target + offset, count, sizeof(struct ocfs2_xattr_entry),
> -	     cmp_xe, swap_xe);
> +	     cmp_xe, NULL);
>   }
>   
>   /*
> @@ -4436,7 +4427,7 @@ static int ocfs2_defrag_xattr_bucket(struct inode *inode,
>   	 */
>   	sort(entries, le16_to_cpu(xh->xh_count),
>   	     sizeof(struct ocfs2_xattr_entry),
> -	     cmp_xe_offset, swap_xe);
> +	     cmp_xe_offset, NULL);
>   
>   	/* Move all name/values to the end of the bucket. */
>   	xe = xh->xh_entries;
> @@ -4478,7 +4469,7 @@ static int ocfs2_defrag_xattr_bucket(struct inode *inode,
>   	/* sort the entries by their name_hash. */
>   	sort(entries, le16_to_cpu(xh->xh_count),
>   	     sizeof(struct ocfs2_xattr_entry),
> -	     cmp_xe, swap_xe);
> +	     cmp_xe, NULL);
>   
>   	buf = bucket_buf;
>   	for (i = 0; i < bucket->bu_blocks; i++, buf += blocksize)