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Message-ID: <7898bedf-0c02-432b-999a-01437265b51b@linux.alibaba.com>
Date: Wed, 24 Dec 2025 16:15:34 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Hongbo Li <lihongbo22@...wei.com>
Cc: linux-fsdevel@...r.kernel.org, linux-erofs@...ts.ozlabs.org,
linux-kernel@...r.kernel.org, Chao Yu <chao@...nel.org>,
Christian Brauner <brauner@...nel.org>, "Darrick J. Wong"
<djwong@...nel.org>, Amir Goldstein <amir73il@...il.com>,
Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v11 08/10] erofs: support unencoded inodes for page cache
share
On 2025/12/24 12:09, Hongbo Li wrote:
> This patch adds inode page cache sharing functionality for unencoded
> files.
>
> I conducted experiments in the container environment. Below is the
> memory usage for reading all files in two different minor versions
> of container images:
>
> +-------------------+------------------+-------------+---------------+
> | Image | Page Cache Share | Memory (MB) | Memory |
> | | | | Reduction (%) |
> +-------------------+------------------+-------------+---------------+
> | | No | 241 | - |
> | redis +------------------+-------------+---------------+
> | 7.2.4 & 7.2.5 | Yes | 163 | 33% |
> +-------------------+------------------+-------------+---------------+
> | | No | 872 | - |
> | postgres +------------------+-------------+---------------+
> | 16.1 & 16.2 | Yes | 630 | 28% |
> +-------------------+------------------+-------------+---------------+
> | | No | 2771 | - |
> | tensorflow +------------------+-------------+---------------+
> | 2.11.0 & 2.11.1 | Yes | 2340 | 16% |
> +-------------------+------------------+-------------+---------------+
> | | No | 926 | - |
> | mysql +------------------+-------------+---------------+
> | 8.0.11 & 8.0.12 | Yes | 735 | 21% |
> +-------------------+------------------+-------------+---------------+
> | | No | 390 | - |
> | nginx +------------------+-------------+---------------+
> | 7.2.4 & 7.2.5 | Yes | 219 | 44% |
> +-------------------+------------------+-------------+---------------+
> | tomcat | No | 924 | - |
> | 10.1.25 & 10.1.26 +------------------+-------------+---------------+
> | | Yes | 474 | 49% |
> +-------------------+------------------+-------------+---------------+
>
> Additionally, the table below shows the runtime memory usage of the
> container:
>
> +-------------------+------------------+-------------+---------------+
> | Image | Page Cache Share | Memory (MB) | Memory |
> | | | | Reduction (%) |
> +-------------------+------------------+-------------+---------------+
> | | No | 35 | - |
> | redis +------------------+-------------+---------------+
> | 7.2.4 & 7.2.5 | Yes | 28 | 20% |
> +-------------------+------------------+-------------+---------------+
> | | No | 149 | - |
> | postgres +------------------+-------------+---------------+
> | 16.1 & 16.2 | Yes | 95 | 37% |
> +-------------------+------------------+-------------+---------------+
> | | No | 1028 | - |
> | tensorflow +------------------+-------------+---------------+
> | 2.11.0 & 2.11.1 | Yes | 930 | 10% |
> +-------------------+------------------+-------------+---------------+
> | | No | 155 | - |
> | mysql +------------------+-------------+---------------+
> | 8.0.11 & 8.0.12 | Yes | 132 | 15% |
> +-------------------+------------------+-------------+---------------+
> | | No | 25 | - |
> | nginx +------------------+-------------+---------------+
> | 7.2.4 & 7.2.5 | Yes | 20 | 20% |
> +-------------------+------------------+-------------+---------------+
> | tomcat | No | 186 | - |
> | 10.1.25 & 10.1.26 +------------------+-------------+---------------+
> | | Yes | 98 | 48% |
> +-------------------+------------------+-------------+---------------+
>
> Co-developed-by: Hongzhen Luo <hongzhen@...ux.alibaba.com>
> Signed-off-by: Hongzhen Luo <hongzhen@...ux.alibaba.com>
> Signed-off-by: Hongbo Li <lihongbo22@...wei.com>
> ---
> fs/erofs/data.c | 32 +++++++++++++++++++++++++-------
> fs/erofs/inode.c | 4 ++++
> fs/erofs/internal.h | 2 ++
> fs/erofs/ishare.c | 31 +++++++++++++++++++++++++++++++
> 4 files changed, 62 insertions(+), 7 deletions(-)
>
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index 71e23d91123d..cbe7ac194b09 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -269,6 +269,7 @@ void erofs_onlinefolio_end(struct folio *folio, int err, bool dirty)
> struct erofs_iomap_iter_ctx {
> struct page *page;
> void *base;
> + struct inode *realinode;
> };
>
> static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> @@ -276,14 +277,15 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> {
> struct iomap_iter *iter = container_of(iomap, struct iomap_iter, iomap);
> struct erofs_iomap_iter_ctx *ctx = iter->private;
> - struct super_block *sb = inode->i_sb;
> + struct inode *realinode = ctx ? ctx->realinode : inode;
> + struct super_block *sb = realinode->i_sb;
> struct erofs_map_blocks map;
> struct erofs_map_dev mdev;
> int ret;
>
> map.m_la = offset;
> map.m_llen = length;
> - ret = erofs_map_blocks(inode, &map);
> + ret = erofs_map_blocks(realinode, &map);
> if (ret < 0)
> return ret;
>
> @@ -296,7 +298,7 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> return 0;
> }
>
> - if (!(map.m_flags & EROFS_MAP_META) || !erofs_inode_in_metabox(inode)) {
> + if (!(map.m_flags & EROFS_MAP_META) || !erofs_inode_in_metabox(realinode)) {
> mdev = (struct erofs_map_dev) {
> .m_deviceid = map.m_deviceid,
> .m_pa = map.m_pa,
> @@ -322,7 +324,7 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> void *ptr;
>
> ptr = erofs_read_metabuf(&buf, sb, map.m_pa,
> - erofs_inode_in_metabox(inode));
> + erofs_inode_in_metabox(realinode));
> if (IS_ERR(ptr))
> return PTR_ERR(ptr);
> iomap->inline_data = ptr;
> @@ -379,30 +381,44 @@ int erofs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> */
> static int erofs_read_folio(struct file *file, struct folio *folio)
> {
> + struct inode *inode = folio_inode(folio);
> struct iomap_read_folio_ctx read_ctx = {
> .ops = &iomap_bio_read_ops,
> .cur_folio = folio,
> };
> - struct erofs_iomap_iter_ctx iter_ctx = {};
> + bool need_iput = false;
`bool need_iput` is enough, see below.
> + struct erofs_iomap_iter_ctx iter_ctx = {> + .realinode = erofs_real_inode(inode, &need_iput),
> + };
>
> + DBG_BUGON(!iter_ctx.realinode);
just remove this line, since erofs_real_inode() already has this check.
> trace_erofs_read_folio(folio, true);
>
> iomap_read_folio(&erofs_iomap_ops, &read_ctx, &iter_ctx);
> + if (need_iput)
> + iput(iter_ctx.realinode);
> return 0;
> }
>
> static void erofs_readahead(struct readahead_control *rac)
> {
> + struct inode *inode = rac->mapping->host;
> struct iomap_read_folio_ctx read_ctx = {
> .ops = &iomap_bio_read_ops,
> .rac = rac,
> };
> - struct erofs_iomap_iter_ctx iter_ctx = {};
> + bool need_iput = false;
`bool need_iput` is enough, see below.
> + struct erofs_iomap_iter_ctx iter_ctx = {
> + .realinode = erofs_real_inode(inode, &need_iput),
> + };
>
> + DBG_BUGON(!iter_ctx.realinode);
just remove this line, since erofs_real_inode() already has this check.
> trace_erofs_readahead(rac->mapping->host, readahead_index(rac),
> readahead_count(rac), true);
>
> iomap_readahead(&erofs_iomap_ops, &read_ctx, &iter_ctx);
> + if (need_iput)
> + iput(iter_ctx.realinode);
> }
>
> static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
> @@ -423,7 +439,9 @@ static ssize_t erofs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
> return dax_iomap_rw(iocb, to, &erofs_iomap_ops);
> #endif
> if ((iocb->ki_flags & IOCB_DIRECT) && inode->i_sb->s_bdev) {
> - struct erofs_iomap_iter_ctx iter_ctx = {};
> + struct erofs_iomap_iter_ctx iter_ctx = {
> + .realinode = inode,
> + };
>
> return iomap_dio_rw(iocb, to, &erofs_iomap_ops,
> NULL, 0, &iter_ctx, 0);
> diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
> index bce98c845a18..8116738fe432 100644
> --- a/fs/erofs/inode.c
> +++ b/fs/erofs/inode.c
> @@ -215,6 +215,10 @@ static int erofs_fill_inode(struct inode *inode)
> case S_IFREG:
> inode->i_op = &erofs_generic_iops;
> inode->i_fop = &erofs_file_fops;
> +#ifdef CONFIG_EROFS_FS_PAGE_CACHE_SHARE
> + if (erofs_ishare_fill_inode(inode))
> + inode->i_fop = &erofs_ishare_fops;
> +#endif
> break;
> case S_IFDIR:
> inode->i_op = &erofs_dir_iops;
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index a2b2434ee3c8..6930cce8f1fb 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -565,11 +565,13 @@ int __init erofs_init_ishare(void);
> void erofs_exit_ishare(void);
> bool erofs_ishare_fill_inode(struct inode *inode);
> void erofs_ishare_free_inode(struct inode *inode);
> +struct inode *erofs_real_inode(struct inode *inode, bool *need_iput);
> #else
> static inline int erofs_init_ishare(void) { return 0; }
> static inline void erofs_exit_ishare(void) {}
> static inline bool erofs_ishare_fill_inode(struct inode *inode) { return false; }
> static inline void erofs_ishare_free_inode(struct inode *inode) {}
> +static inline struct inode *erofs_real_inode(struct inode *inode, bool *need_iput) { return inode; }
static inline struct inode *erofs_real_inode(struct inode *inode, bool *need_iput)
{
*need_iput = false;
return inode;
}
> #endif // CONFIG_EROFS_FS_PAGE_CACHE_SHARE
>
> long erofs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg);
> diff --git a/fs/erofs/ishare.c b/fs/erofs/ishare.c
> index 09ea456f2eab..634b7ea63738 100644
> --- a/fs/erofs/ishare.c
> +++ b/fs/erofs/ishare.c
> @@ -11,6 +11,12 @@
>
> static struct vfsmount *erofs_ishare_mnt;
>
> +static inline bool erofs_is_ishare_inode(struct inode *inode)
> +{
> + /* assumed FS_ONDEMAND is excluded with FS_PAGE_CACHE_SHARE feature */
> + return inode->i_sb->s_type == &erofs_anon_fs_type;
> +}
> +
> static int erofs_ishare_iget5_eq(struct inode *inode, void *data)
> {
> struct erofs_inode_fingerprint *fp1 = &EROFS_I(inode)->fingerprint;
> @@ -157,6 +163,31 @@ const struct file_operations erofs_ishare_fops = {
> .splice_read = filemap_splice_read,
> };
>
> +struct inode *erofs_real_inode(struct inode *inode, bool *need_iput)
> +{
> + struct erofs_inode *vi, *vi_dedup;
> + struct inode *realinode;
*need_iput = false;
here
Thanks,
Gao Xiang
> +
> + if (!erofs_is_ishare_inode(inode))
> + return inode;
> +
> + vi_dedup = EROFS_I(inode);
> + spin_lock(&vi_dedup->ishare_lock);
> + /* fetch any one as real inode */
> + DBG_BUGON(list_empty(&vi_dedup->ishare_list));
> + list_for_each_entry(vi, &vi_dedup->ishare_list, ishare_list) {
> + realinode = igrab(&vi->vfs_inode);
> + if (realinode) {
> + *need_iput = true;
> + break;
> + }
> + }
> + spin_unlock(&vi_dedup->ishare_lock);
> +
> + DBG_BUGON(!realinode);
> + return realinode;
> +}
> +
> int __init erofs_init_ishare(void)
> {
> erofs_ishare_mnt = kern_mount(&erofs_anon_fs_type);
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