linux-kernel - Re: [PATCH v12 09/10] erofs: support compressed inodes for page cache share

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Message-ID: <ee332277-b19f-4c7c-9114-6fc19878ed43@linux.alibaba.com>
Date: Wed, 7 Jan 2026 14:15:29 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Hongbo Li <lihongbo22@...wei.com>
Cc: djwong@...nel.org, amir73il@...il.com, hch@....de,
 linux-fsdevel@...r.kernel.org, linux-erofs@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org, Chao Yu <chao@...nel.org>, brauner@...nel.org
Subject: Re: [PATCH v12 09/10] erofs: support compressed inodes for page cache
 share



On 2025/12/31 17:01, Hongbo Li wrote:
> From: Hongzhen Luo <hongzhen@...ux.alibaba.com>
> 
> This patch adds page cache sharing functionality for compressed inodes.
> 
> Signed-off-by: Hongzhen Luo <hongzhen@...ux.alibaba.com>
> Signed-off-by: Hongbo Li <lihongbo22@...wei.com>
> ---
>   fs/erofs/zdata.c | 37 ++++++++++++++++++++++++-------------
>   1 file changed, 24 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index 65da21504632..2697c703a4c4 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -493,7 +493,8 @@ enum z_erofs_pclustermode {
>   };
>   
>   struct z_erofs_frontend {
> -	struct inode *const inode;
> +	struct inode *inode;
> +	struct inode *sharedinode;

Let's combine these two lines into one for two related inodes?

	struct inode *inode, *sharedinode;

>   	struct erofs_map_blocks map;
>   	struct z_erofs_bvec_iter biter;
>   
> @@ -508,8 +509,8 @@ struct z_erofs_frontend {
>   	unsigned int icur;
>   };
>   
> -#define Z_EROFS_DEFINE_FRONTEND(fe, i, ho) struct z_erofs_frontend fe = { \
> -	.inode = i, .head = Z_EROFS_PCLUSTER_TAIL, \
> +#define Z_EROFS_DEFINE_FRONTEND(fe, i, si, ho) struct z_erofs_frontend fe = { \
> +	.inode = i, .sharedinode = si, .head = Z_EROFS_PCLUSTER_TAIL, \
>   	.mode = Z_EROFS_PCLUSTER_FOLLOWED, .headoffset = ho }
>   
>   static bool z_erofs_should_alloc_cache(struct z_erofs_frontend *fe)
> @@ -1866,7 +1867,7 @@ static void z_erofs_pcluster_readmore(struct z_erofs_frontend *f,
>   		pgoff_t index = cur >> PAGE_SHIFT;
>   		struct folio *folio;
>   
> -		folio = erofs_grab_folio_nowait(inode->i_mapping, index);
> +		folio = erofs_grab_folio_nowait(f->sharedinode->i_mapping, index);
>   		if (!IS_ERR_OR_NULL(folio)) {
>   			if (folio_test_uptodate(folio))
>   				folio_unlock(folio);
> @@ -1883,8 +1884,10 @@ static void z_erofs_pcluster_readmore(struct z_erofs_frontend *f,
>   
>   static int z_erofs_read_folio(struct file *file, struct folio *folio)
>   {
> -	struct inode *const inode = folio->mapping->host;
> -	Z_EROFS_DEFINE_FRONTEND(f, inode, folio_pos(folio));
> +	struct inode *const sharedinode = folio->mapping->host;

Let's drop useless const annotation:

	struct inode *sharedinode = folio->mapping->host;

> +	bool need_iput;
> +	struct inode *realinode = erofs_real_inode(sharedinode, &need_iput);
> +	Z_EROFS_DEFINE_FRONTEND(f, realinode, sharedinode, folio_pos(folio));
>   	int err;
>   
>   	trace_erofs_read_folio(folio, false);
> @@ -1896,23 +1899,28 @@ static int z_erofs_read_folio(struct file *file, struct folio *folio)
>   	/* if some pclusters are ready, need submit them anyway */
>   	err = z_erofs_runqueue(&f, 0) ?: err;
>   	if (err && err != -EINTR)
> -		erofs_err(inode->i_sb, "read error %d @ %lu of nid %llu",
> -			  err, folio->index, EROFS_I(inode)->nid);
> +		erofs_err(realinode->i_sb, "read error %d @ %lu of nid %llu",
> +			  err, folio->index, EROFS_I(realinode)->nid);
>   
>   	erofs_put_metabuf(&f.map.buf);
>   	erofs_release_pages(&f.pagepool);
> +
> +	if (need_iput)
> +		iput(realinode);
>   	return err;
>   }
>   
>   static void z_erofs_readahead(struct readahead_control *rac)
>   {
> -	struct inode *const inode = rac->mapping->host;
> -	Z_EROFS_DEFINE_FRONTEND(f, inode, readahead_pos(rac));
> +	struct inode *const sharedinode = rac->mapping->host;

Same here.
	struct inode *sharedinode = rac->mapping->host;

Thanks,
Gao Xiang