From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout04.his.huawei.com (canpmsgout04.his.huawei.com [113.46.200.219]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 836A47DA66; Wed, 7 Jan 2026 07:17:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.219 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767770268; cv=none; b=iQYlAgAKC/GBiLADlEDOivlKY8iVQOpP0B2OjmEfcPaO1868Vi//PP6ar1GM9iAlHSvsj56krE2QPW8/lkTycAxoz8GaXpJKRSplx0s7z+q1bPrT41o4GtgQDvy4Qr9H2Y3aOdSsoDIqO64SNXat2YEP+x7saVsZheLph1seyGc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767770268; c=relaxed/simple; bh=kgjyUt0uKuW4/iXH+ecR2njM9JOGda83VmKrcTi22P0=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=Glps/5EFc9G9HUxF/Pelb0GMExL3ak599qZdfq6LqE6MLTvpE52U346MdKYY9u4/m6lr285sG5/xi6qjfM3S7ewtmnwM6nZr3LMly0qViSa7jB95gduOJIjMGLxyldGcm3kcBHGUMJsTxtM//qxhp2HYGI4hG0dG6z8uho2ebmE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=YrsYVswX; arc=none smtp.client-ip=113.46.200.219 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="YrsYVswX" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=sQnGWCK1oBv8AuiIVg2UnDEz74VkSVgFsLNjqhNRibQ=; b=YrsYVswXO9O+rfs12KPLUfp7aK7j8liXbZ20rfpBz1qUeB6tRulkjr0ye3194aEfRhmrFKaId fO3H4YI0YpeTE5JR7I56XMQuPH2404pnUZ/z1FMMAENj2YYLr7O6GGLfXvexb57kWgpsRbTv4zn Q5Tpo090xpejsgW1333oEY0= Received: from mail.maildlp.com (unknown [172.19.163.104]) by canpmsgout04.his.huawei.com (SkyGuard) with ESMTPS id 4dmK694m89z1prMm; Wed, 7 Jan 2026 15:14:25 +0800 (CST) Received: from kwepemr500015.china.huawei.com (unknown [7.202.195.162]) by mail.maildlp.com (Postfix) with ESMTPS id F02C64056D; Wed, 7 Jan 2026 15:17:42 +0800 (CST) Received: from [10.67.111.104] (10.67.111.104) by kwepemr500015.china.huawei.com (7.202.195.162) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 7 Jan 2026 15:17:42 +0800 Message-ID: <07212138-c0fc-4a64-a323-9cab978bf610@huawei.com> Date: Wed, 7 Jan 2026 15:17:41 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v12 07/10] erofs: introduce the page cache share feature Content-Language: en-US To: Gao Xiang CC: , , , , , , Chao Yu , References: <20251231090118.541061-1-lihongbo22@huawei.com> <20251231090118.541061-8-lihongbo22@huawei.com> <99a517aa-744b-487b-bce8-294b69a0cd50@linux.alibaba.com> From: Hongbo Li In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems500002.china.huawei.com (7.221.188.17) To kwepemr500015.china.huawei.com (7.202.195.162) Hi, Xiang On 2026/1/7 14:56, Gao Xiang wrote: > > > On 2026/1/7 14:48, Hongbo Li wrote: >> Hi, Xiang >> >> On 2026/1/7 14:08, Gao Xiang wrote: >>> >>> >>> On 2025/12/31 17:01, Hongbo Li wrote: >>>> From: Hongzhen Luo >>>> >>>> Currently, reading files with different paths (or names) but the same >>>> content will consume multiple copies of the page cache, even if the >>>> content of these page caches is the same. For example, reading >>>> identical files (e.g., *.so files) from two different minor versions of >>>> container images will cost multiple copies of the same page cache, >>>> since different containers have different mount points. Therefore, >>>> sharing the page cache for files with the same content can save memory. >>>> >>>> This introduces the page cache share feature in erofs. It allocate a >>>> deduplicated inode and use its page cache as shared. Reads for files >>>> with identical content will ultimately be routed to the page cache of >>>> the deduplicated inode. In this way, a single page cache satisfies >>>> multiple read requests for different files with the same contents. >>>> >>>> We introduce inode_share mount option to enable the page sharing mode >>>> during mounting. >>>> >>>> Signed-off-by: Hongzhen Luo >>>> Signed-off-by: Hongbo Li >>>> --- >>>>   Documentation/filesystems/erofs.rst |   5 + >>>>   fs/erofs/Makefile                   |   1 + >>>>   fs/erofs/internal.h                 |  31 +++++ >>>>   fs/erofs/ishare.c                   | 170 >>>> ++++++++++++++++++++++++++++ >>>>   fs/erofs/super.c                    |  55 ++++++++- >>>>   fs/erofs/xattr.c                    |  34 ++++++ >>>>   fs/erofs/xattr.h                    |   3 + >>>>   7 files changed, 297 insertions(+), 2 deletions(-) >>>>   create mode 100644 fs/erofs/ishare.c >>>> >>>> diff --git a/Documentation/filesystems/erofs.rst >>>> b/Documentation/filesystems/erofs.rst >>>> index 08194f194b94..27d3caa3c73c 100644 >>>> --- a/Documentation/filesystems/erofs.rst >>>> +++ b/Documentation/filesystems/erofs.rst >>>> @@ -128,7 +128,12 @@ device=%s              Specify a path to an >>>> extra device to be used together. >>>>   fsid=%s                Specify a filesystem image ID for Fscache >>>> back-end. >>>>   domain_id=%s           Specify a domain ID in fscache mode so that >>>> different images >>>>                          with the same blobs under a given domain ID >>>> can share storage. >>>> +                       Also used for inode page sharing mode which >>>> defines a sharing >>>> +                       domain. >>>>   fsoffset=%llu          Specify block-aligned filesystem offset for >>>> the primary device. >>>> +inode_share            Enable inode page sharing for this >>>> filesystem.  Inodes with >>>> +                       identical content within the same domain ID >>>> can share the >>>> +                       page cache. >>>>   =================== >>>> ========================================================= >>>>   Sysfs Entries >>>> diff --git a/fs/erofs/Makefile b/fs/erofs/Makefile >>>> index 549abc424763..a80e1762b607 100644 >>>> --- a/fs/erofs/Makefile >>>> +++ b/fs/erofs/Makefile >>>> @@ -10,3 +10,4 @@ erofs-$(CONFIG_EROFS_FS_ZIP_ZSTD) += >>>> decompressor_zstd.o >>>>   erofs-$(CONFIG_EROFS_FS_ZIP_ACCEL) += decompressor_crypto.o >>>>   erofs-$(CONFIG_EROFS_FS_BACKED_BY_FILE) += fileio.o >>>>   erofs-$(CONFIG_EROFS_FS_ONDEMAND) += fscache.o >>>> +erofs-$(CONFIG_EROFS_FS_PAGE_CACHE_SHARE) += ishare.o >>>> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h >>>> index ec79e8b44d3b..6ef1cdd9d651 100644 >>>> --- a/fs/erofs/internal.h >>>> +++ b/fs/erofs/internal.h >>>> @@ -179,6 +179,7 @@ struct erofs_sb_info { >>>>   #define EROFS_MOUNT_DAX_ALWAYS        0x00000040 >>>>   #define EROFS_MOUNT_DAX_NEVER        0x00000080 >>>>   #define EROFS_MOUNT_DIRECT_IO        0x00000100 >>>> +#define EROFS_MOUNT_INODE_SHARE        0x00000200 >>>>   #define clear_opt(opt, option)    ((opt)->mount_opt &= >>>> ~EROFS_MOUNT_##option) >>>>   #define set_opt(opt, option)    ((opt)->mount_opt |= >>>> EROFS_MOUNT_##option) >>>> @@ -269,6 +270,11 @@ static inline u64 erofs_nid_to_ino64(struct >>>> erofs_sb_info *sbi, erofs_nid_t nid) >>>>   /* default readahead size of directories */ >>>>   #define EROFS_DIR_RA_BYTES    16384 >>>> +struct erofs_inode_fingerprint { >>>> +    u8 *opaque; >>>> +    int size; >>>> +}; >>>> + >>>>   struct erofs_inode { >>>>       erofs_nid_t nid; >>>> @@ -304,6 +310,18 @@ struct erofs_inode { >>>>           }; >>>>   #endif    /* CONFIG_EROFS_FS_ZIP */ >>>>       }; >>>> +#ifdef CONFIG_EROFS_FS_PAGE_CACHE_SHARE >>>> +    struct list_head ishare_list; >>>> +    union { >>>> +        /* for each anon shared inode */ >>>> +        struct { >>>> +            struct erofs_inode_fingerprint fingerprint; >>>> +            spinlock_t ishare_lock; >>>> +        }; >>>> +        /* for each real inode */ >>>> +        struct inode *sharedinode; >>>> +    }; >>>> +#endif >>>>       /* the corresponding vfs inode */ >>>>       struct inode vfs_inode; >>>>   }; >>>> @@ -410,6 +428,7 @@ extern const struct inode_operations >>>> erofs_dir_iops; >>>>   extern const struct file_operations erofs_file_fops; >>>>   extern const struct file_operations erofs_dir_fops; >>>> +extern const struct file_operations erofs_ishare_fops; >>>>   extern const struct iomap_ops z_erofs_iomap_report_ops; >>>> @@ -541,6 +560,18 @@ static inline struct bio >>>> *erofs_fscache_bio_alloc(struct erofs_map_dev *mdev) { >>>>   static inline void erofs_fscache_submit_bio(struct bio *bio) {} >>>>   #endif >>>> +#ifdef CONFIG_EROFS_FS_PAGE_CACHE_SHARE >>>> +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); >>>> +#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) {} >>>> +#endif // CONFIG_EROFS_FS_PAGE_CACHE_SHARE >>>> + >>>>   long erofs_ioctl(struct file *filp, unsigned int cmd, unsigned >>>> long arg); >>>>   long erofs_compat_ioctl(struct file *filp, unsigned int cmd, >>>>               unsigned long arg); >>>> diff --git a/fs/erofs/ishare.c b/fs/erofs/ishare.c >>>> new file mode 100644 >>>> index 000000000000..e93d379d4a3a >>>> --- /dev/null >>>> +++ b/fs/erofs/ishare.c >>>> @@ -0,0 +1,170 @@ >>>> +// SPDX-License-Identifier: GPL-2.0-or-later >>>> +/* >>>> + * Copyright (C) 2024, Alibaba Cloud >>>> + */ >>>> +#include >>>> +#include >>>> +#include "internal.h" >>>> +#include "xattr.h" >>>> + >>>> +#include "../internal.h" >>>> + >>>> +static struct vfsmount *erofs_ishare_mnt; >>>> + >>>> +static int erofs_ishare_iget5_eq(struct inode *inode, void *data) >>>> +{ >>>> +    struct erofs_inode_fingerprint *fp1 = >>>> &EROFS_I(inode)->fingerprint; >>>> +    struct erofs_inode_fingerprint *fp2 = data; >>>> + >>>> +    return fp1->size == fp2->size && >>>> +        !memcmp(fp1->opaque, fp2->opaque, fp2->size); >>>> +} >>>> + >>>> +static int erofs_ishare_iget5_set(struct inode *inode, void *data) >>>> +{ >>>> +    struct erofs_inode *vi = EROFS_I(inode); >>>> + >>>> +    vi->fingerprint = *(struct erofs_inode_fingerprint *)data; >>>> +    INIT_LIST_HEAD(&vi->ishare_list); >>>> +    spin_lock_init(&vi->ishare_lock); >>>> +    return 0; >>>> +} >>>> + >>>> +bool erofs_ishare_fill_inode(struct inode *inode) >>>> +{ >>>> +    struct erofs_sb_info *sbi = EROFS_SB(inode->i_sb); >>>> +    struct erofs_inode *vi = EROFS_I(inode); >>>> +    struct erofs_inode_fingerprint fp; >>>> +    struct inode *sharedinode; >>>> +    unsigned long hash; >>>> + >>>> +    if (!test_opt(&sbi->opt, INODE_SHARE)) >>>> +        return false; >>>> +    (void)erofs_xattr_fill_ishare_fp(&fp, inode, sbi->domain_id); >>>> +    if (!fp.size) >>>> +        return false; >>> >>> Why not just: >>> >>>      if (erofs_xattr_fill_ishare_fp(&fp, inode, sbi->domain_id)) >>>          return false; >>> >> >> When erofs_sb_has_ishare_xattrs returns false, >> erofs_xattr_fill_ishare_fp also considers success. > > Then why !test_opt(&sbi->opt, INODE_SHARE) didn't return? > The MOUNT_INODE_SHARE flag is passed from user's mount option. And it is controllered by CONFIG_EROFS_FS_PAGE_CACHE_SHARE. I doesn't do the check when the superblock without ishare_xattrs. (It seems the mount options is static, although it is useless for mounting with inode_share on one EROFS image without ishare_xattrs). So should we check that if the superblock has not ishare_xattrs feature, and we return -ENOSUPP? Thanks, Hongbo > Thanks, > Gao Xiang