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Message-ID: <bf48239c-6850-d33d-e7f6-1a4a15400ae9@linux.alibaba.com>
Date:   Sat, 22 Jul 2023 15:33:11 +0800
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Subject: Re: [PATCH v5 2/2] erofs: boost negative xattr lookup with bloom
 filter
Content-Language: en-US
To:     linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org
References: <20230721104923.20236-1-jefflexu@linux.alibaba.com>
 <20230721104923.20236-3-jefflexu@linux.alibaba.com> <ZLt/oJWa4MoE4F25@debian>
From:   Jingbo Xu <jefflexu@linux.alibaba.com>
In-Reply-To: <ZLt/oJWa4MoE4F25@debian>
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On 7/22/23 3:05 PM, Gao Xiang wrote:
> On Fri, Jul 21, 2023 at 06:49:23PM +0800, Jingbo Xu wrote:
>> Optimise the negative xattr lookup with bloom filter.
>>
>> The bit value for the bloom filter map has a reverse semantics for
>> compatibility.  That is, the bit value of 0 indicates existence, while
>> the bit value of 1 indicates the absence of corresponding xattr.
>>
>> The initial version is _only_ enabled when xattr_filter_reserved is
>> zero.  The filter map internals may change in the future, in which case
>> the reserved flag will be set non-zero and we don't need bothering the
>> compatible bits again at that time.  For now disable the optimization if
>> this reserved flag is non-zero.
>>
>> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
>> ---
>>  fs/erofs/Kconfig    |  1 +
>>  fs/erofs/internal.h |  3 +++
>>  fs/erofs/super.c    |  1 +
>>  fs/erofs/xattr.c    | 14 ++++++++++++++
>>  4 files changed, 19 insertions(+)
>>
>> diff --git a/fs/erofs/Kconfig b/fs/erofs/Kconfig
>> index f259d92c9720..f49669def828 100644
>> --- a/fs/erofs/Kconfig
>> +++ b/fs/erofs/Kconfig
>> @@ -38,6 +38,7 @@ config EROFS_FS_DEBUG
>>  config EROFS_FS_XATTR
>>  	bool "EROFS extended attributes"
>>  	depends on EROFS_FS
>> +	select XXHASH
>>  	default y
>>  	help
>>  	  Extended attributes are name:value pairs associated with inodes by
>> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
>> index 36e32fa542f0..3c1f89d8421b 100644
>> --- a/fs/erofs/internal.h
>> +++ b/fs/erofs/internal.h
>> @@ -151,6 +151,7 @@ struct erofs_sb_info {
>>  	u32 xattr_prefix_start;
>>  	u8 xattr_prefix_count;
>>  	struct erofs_xattr_prefix_item *xattr_prefixes;
>> +	unsigned int xattr_filter_reserved;
>>  #endif
>>  	u16 device_id_mask;	/* valid bits of device id to be used */
>>  
>> @@ -251,6 +252,7 @@ EROFS_FEATURE_FUNCS(fragments, incompat, INCOMPAT_FRAGMENTS)
>>  EROFS_FEATURE_FUNCS(dedupe, incompat, INCOMPAT_DEDUPE)
>>  EROFS_FEATURE_FUNCS(xattr_prefixes, incompat, INCOMPAT_XATTR_PREFIXES)
>>  EROFS_FEATURE_FUNCS(sb_chksum, compat, COMPAT_SB_CHKSUM)
>> +EROFS_FEATURE_FUNCS(xattr_filter, compat, COMPAT_XATTR_FILTER)
>>  
>>  /* atomic flag definitions */
>>  #define EROFS_I_EA_INITED_BIT	0
>> @@ -270,6 +272,7 @@ struct erofs_inode {
>>  	unsigned char inode_isize;
>>  	unsigned int xattr_isize;
>>  
>> +	unsigned int xattr_name_filter;
>>  	unsigned int xattr_shared_count;
>>  	unsigned int *xattr_shared_xattrs;
>>  
>> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
>> index 9d6a3c6158bd..72122323300e 100644
>> --- a/fs/erofs/super.c
>> +++ b/fs/erofs/super.c
>> @@ -388,6 +388,7 @@ static int erofs_read_superblock(struct super_block *sb)
>>  	sbi->xattr_blkaddr = le32_to_cpu(dsb->xattr_blkaddr);
>>  	sbi->xattr_prefix_start = le32_to_cpu(dsb->xattr_prefix_start);
>>  	sbi->xattr_prefix_count = dsb->xattr_prefix_count;
>> +	sbi->xattr_filter_reserved = dsb->xattr_filter_reserved;
>>  #endif
>>  	sbi->islotbits = ilog2(sizeof(struct erofs_inode_compact));
>>  	sbi->root_nid = le16_to_cpu(dsb->root_nid);
>> diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
>> index 40178b6e0688..e9b9ed6b28d2 100644
>> --- a/fs/erofs/xattr.c
>> +++ b/fs/erofs/xattr.c
>> @@ -5,6 +5,7 @@
>>   * Copyright (C) 2021-2022, Alibaba Cloud
>>   */
>>  #include <linux/security.h>
>> +#include <linux/xxhash.h>
>>  #include "xattr.h"
>>  
>>  struct erofs_xattr_iter {
>> @@ -87,6 +88,7 @@ static int erofs_init_inode_xattrs(struct inode *inode)
>>  	}
>>  
>>  	ih = it.kaddr + erofs_blkoff(sb, it.pos);
>> +	vi->xattr_name_filter = le32_to_cpu(ih->h_name_filter);
>>  	vi->xattr_shared_count = ih->h_shared_count;
>>  	vi->xattr_shared_xattrs = kmalloc_array(vi->xattr_shared_count,
>>  						sizeof(uint), GFP_KERNEL);
>> @@ -392,7 +394,10 @@ int erofs_getxattr(struct inode *inode, int index, const char *name,
>>  		   void *buffer, size_t buffer_size)
>>  {
>>  	int ret;
>> +	uint32_t hashbit;
> 
> Why using `uint32_t` here rather than `unsigned int`? We don't use
> `uint32_t` in the kernel codebase.
> 

xxh32() returns uint32_t.


-- 
Thanks,
Jingbo