[PATCH v5 0/2] erofs: introduce xattr name bloom filter

[PATCH v5 0/2] erofs: introduce xattr name bloom filter

[Jingbo Xu]

changes since v4:
- patch 2: polish commit message; declare erofs_inode.xattr_name_filter
  as unsigned int instead of unsigned long; rename `bit` to `hashbit`;
  use bitwise and instead of test_bit() to test the hashbit (Gao Xiang)

changes since v3:
- patch 1: add "Reviewed-by" tag (Gao Xiang)
- patch 2: make CONFIG_EROFS_FS_XATTR select CONFIG_XXHASH (Gao Xiang)

changes since v2:
- patch 1: polish the commit message; introduce xattr_filter_reserved in
  on-disk superblock; remove EROFS_XATTR_FILTER_MASK (Gao Xiang)

changes since RFC:
- the number of hash functions is 1, and now it's implemented as:
    xxh32(name, strlen(name), EROFS_XATTR_FILTER_SEED + index),
  where the constant magic number EROFS_XATTR_FILTER_SEED [*] is used to
  give a better spread for the mapping. (Alexander Larsson)
  Refer to patch 1 for more details.
- fix the value of EROFS_FEATURE_COMPAT_XATTR_BLOOM; rename
  EROFS_XATTR_BLOOM_* to EROFS_XATTR_FILTER_* (Gao Xiang)
- pass all tests in erofs-utils (MKFS_OPTIONS="--xattr-filter" make
  check)

[*] https://lore.kernel.org/all/74a8a369-c3b0-b338-fa8f-fdd7c252efaf@linux.alibaba.com/
RFC: https://lore.kernel.org/all/20230621083209.116024-1-jefflexu@linux.alibaba.com/
v2: https://lore.kernel.org/all/20230705070427.92579-1-jefflexu@linux.alibaba.com/
v3: https://lore.kernel.org/all/20230712115123.33712-1-jefflexu@linux.alibaba.com/
v4: https://lore.kernel.org/all/20230714031034.53210-1-jefflexu@linux.alibaba.com/


Jingbo Xu (2):
  erofs: update on-disk format for xattr name filter
  erofs: boost negative xattr lookup with bloom filter

 fs/erofs/Kconfig    |  1 +
 fs/erofs/erofs_fs.h | 10 ++++++++--
 fs/erofs/internal.h |  3 +++
 fs/erofs/super.c    |  1 +
 fs/erofs/xattr.c    | 14 ++++++++++++++
 5 files changed, 27 insertions(+), 2 deletions(-)

-- 
2.19.1.6.gb485710b

[PATCH v5 1/2] erofs: update on-disk format for xattr name filter

[Jingbo Xu]

The xattr name bloom filter feature is going to be introduced to speed
up the negative xattr lookup, e.g. system.posix_acl_[access|default]
lookup when running "ls -lR" workload.

There are some commonly used extended attributes (n) and the total
number of these is approximately 30.

	trusted.overlay.opaque
	trusted.overlay.redirect
	trusted.overlay.origin
	trusted.overlay.impure
	trusted.overlay.nlink
	trusted.overlay.upper
	trusted.overlay.metacopy
	trusted.overlay.protattr
	user.overlay.opaque
	user.overlay.redirect
	user.overlay.origin
	user.overlay.impure
	user.overlay.nlink
	user.overlay.upper
	user.overlay.metacopy
	user.overlay.protattr
	security.evm
	security.ima
	security.selinux
	security.SMACK64
	security.SMACK64IPIN
	security.SMACK64IPOUT
	security.SMACK64EXEC
	security.SMACK64TRANSMUTE
	security.SMACK64MMAP
	security.apparmor
	security.capability
	system.posix_acl_access
	system.posix_acl_default
	user.mime_type

Given the number of bits of the bloom filter (m) is 32, the optimal
value for the number of the hash functions (k) is 1 (ln2 * m/n = 0.74).

The single hash function is implemented as:

	xxh32(name, strlen(name), EROFS_XATTR_FILTER_SEED + index)

where `index` represents the index of corresponding predefined short name
prefix, while `name` represents the name string after stripping the above
predefined name prefix.

The constant magic number EROFS_XATTR_FILTER_SEED, i.e. 0x25BBE08F, is
used to give a better spread when mapping these 30 extended attributes
into 32-bit bloom filter as:

	bit  0: security.ima
	bit  1:
	bit  2: trusted.overlay.nlink
	bit  3:
	bit  4: user.overlay.nlink
	bit  5: trusted.overlay.upper
	bit  6: user.overlay.origin
	bit  7: trusted.overlay.protattr
	bit  8: security.apparmor
	bit  9: user.overlay.protattr
	bit 10: user.overlay.opaque
	bit 11: security.selinux
	bit 12: security.SMACK64TRANSMUTE
	bit 13: security.SMACK64
	bit 14: security.SMACK64MMAP
	bit 15: user.overlay.impure
	bit 16: security.SMACK64IPIN
	bit 17: trusted.overlay.redirect
	bit 18: trusted.overlay.origin
	bit 19: security.SMACK64IPOUT
	bit 20: trusted.overlay.opaque
	bit 21: system.posix_acl_default
	bit 22:
	bit 23: user.mime_type
	bit 24: trusted.overlay.impure
	bit 25: security.SMACK64EXEC
	bit 26: user.overlay.redirect
	bit 27: user.overlay.upper
	bit 28: security.evm
	bit 29: security.capability
	bit 30: system.posix_acl_access
	bit 31: trusted.overlay.metacopy, user.overlay.metacopy

h_name_filter is introduced to the on-disk per-inode xattr header to
place the corresponding xattr name filter, where bit value 1 indicates
non-existence for compatibility.

This feature is indicated by EROFS_FEATURE_COMPAT_XATTR_FILTER
compatible feature bit.

Reserve one byte in on-disk superblock as the on-disk format for xattr
name filter may change in the future.  With this flag we don't need
bothering these compatible bits again at that time.

Suggested-by: Alexander Larsson <alexl@redhat.com>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 fs/erofs/erofs_fs.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
index 2c7b16e340fe..e2944f4a6ff9 100644
--- a/fs/erofs/erofs_fs.h
+++ b/fs/erofs/erofs_fs.h
@@ -13,6 +13,7 @@
 
 #define EROFS_FEATURE_COMPAT_SB_CHKSUM          0x00000001
 #define EROFS_FEATURE_COMPAT_MTIME              0x00000002
+#define EROFS_FEATURE_COMPAT_XATTR_FILTER	0x00000004
 
 /*
  * Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
@@ -81,7 +82,8 @@ struct erofs_super_block {
 	__u8 xattr_prefix_count;	/* # of long xattr name prefixes */
 	__le32 xattr_prefix_start;	/* start of long xattr prefixes */
 	__le64 packed_nid;	/* nid of the special packed inode */
-	__u8 reserved2[24];
+	__u8 xattr_filter_reserved; /* reserved for xattr name filter */
+	__u8 reserved2[23];
 };
 
 /*
@@ -200,7 +202,7 @@ struct erofs_inode_extended {
  * for read-only fs, no need to introduce h_refcount
  */
 struct erofs_xattr_ibody_header {
-	__le32 h_reserved;
+	__le32 h_name_filter;		/* bit value 1 indicates not-present */
 	__u8   h_shared_count;
 	__u8   h_reserved2[7];
 	__le32 h_shared_xattrs[];       /* shared xattr id array */
@@ -221,6 +223,10 @@ struct erofs_xattr_ibody_header {
 #define EROFS_XATTR_LONG_PREFIX		0x80
 #define EROFS_XATTR_LONG_PREFIX_MASK	0x7f
 
+#define EROFS_XATTR_FILTER_BITS		32
+#define EROFS_XATTR_FILTER_DEFAULT	UINT32_MAX
+#define EROFS_XATTR_FILTER_SEED		0x25BBE08F
+
 /* xattr entry (for both inline & shared xattrs) */
 struct erofs_xattr_entry {
 	__u8   e_name_len;      /* length of name */
-- 
2.19.1.6.gb485710b

[PATCH v5 2/2] erofs: boost negative xattr lookup with bloom filter

[Jingbo Xu]

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;
 	struct erofs_xattr_iter it;
+	struct erofs_inode *vi = EROFS_I(inode);
+	struct erofs_sb_info *sbi = EROFS_SB(inode->i_sb);
 
 	if (!name)
 		return -EINVAL;
@@ -401,6 +406,15 @@ int erofs_getxattr(struct inode *inode, int index, const char *name,
 	if (ret)
 		return ret;
 
+	/* reserved flag is non-zero if there's any change of on-disk format */
+	if (erofs_sb_has_xattr_filter(sbi) && !sbi->xattr_filter_reserved) {
+		hashbit = xxh32(name, strlen(name),
+				EROFS_XATTR_FILTER_SEED + index);
+		hashbit &= EROFS_XATTR_FILTER_BITS - 1;
+		if (vi->xattr_name_filter & (1U << hashbit))
+			return -ENOATTR;
+	}
+
 	it.index = index;
 	it.name = (struct qstr)QSTR_INIT(name, strlen(name));
 	if (it.name.len > EROFS_NAME_LEN)
-- 
2.19.1.6.gb485710b

Re: [PATCH v5 2/2] erofs: boost negative xattr lookup with bloom filter

[Gao Xiang]

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.

Thanks,
Gao Xiang

Re: [PATCH v5 2/2] erofs: boost negative xattr lookup with bloom filter

[Jingbo Xu]

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

Re: [PATCH v5 2/2] erofs: boost negative xattr lookup with bloom filter

[Gao Xiang]

On Sat, Jul 22, 2023 at 03:33:11PM +0800, Jingbo Xu wrote:

...

> >> +	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.

we never use (u)intxx_t in the native kernel code.

Thanks,
Gao Xiang