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* [f2fs-dev] [PATCH] fs: introduce is_dot_dotdot helper for cleanup
@ 2019-12-02 10:10 Tiezhu Yang
       [not found] ` <20191202200302.GN20752@bombadil.infradead.org>
  0 siblings, 1 reply; 6+ messages in thread
From: Tiezhu Yang @ 2019-12-02 10:10 UTC (permalink / raw)
  To: Alexander Viro, Theodore Y. Ts'o, Jaegeuk Kim, Chao Yu,
	Eric Biggers, Tyler Hicks
  Cc: linux-fsdevel, linux-fscrypt, ecryptfs, linux-kernel, linux-f2fs-devel

There exists many similar and duplicate codes to check "." and "..",
so introduce is_dot_dotdot helper to make the code more clean.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 fs/crypto/fname.c    | 15 ++-------------
 fs/ecryptfs/crypto.c | 13 ++-----------
 fs/f2fs/f2fs.h       | 11 -----------
 fs/libfs.c           | 12 ++++++++++++
 fs/namei.c           |  6 ++----
 include/linux/fs.h   |  2 ++
 6 files changed, 20 insertions(+), 39 deletions(-)

diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index 3da3707..36be864 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -15,17 +15,6 @@
 #include <crypto/skcipher.h>
 #include "fscrypt_private.h"
 
-static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
-{
-	if (str->len == 1 && str->name[0] == '.')
-		return true;
-
-	if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
-		return true;
-
-	return false;
-}
-
 /**
  * fname_encrypt() - encrypt a filename
  *
@@ -255,7 +244,7 @@ int fscrypt_fname_disk_to_usr(struct inode *inode,
 	const struct qstr qname = FSTR_TO_QSTR(iname);
 	struct fscrypt_digested_name digested_name;
 
-	if (fscrypt_is_dot_dotdot(&qname)) {
+	if (is_dot_dotdot(&qname)) {
 		oname->name[0] = '.';
 		oname->name[iname->len - 1] = '.';
 		oname->len = iname->len;
@@ -323,7 +312,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 	memset(fname, 0, sizeof(struct fscrypt_name));
 	fname->usr_fname = iname;
 
-	if (!IS_ENCRYPTED(dir) || fscrypt_is_dot_dotdot(iname)) {
+	if (!IS_ENCRYPTED(dir) || is_dot_dotdot(iname)) {
 		fname->disk_name.name = (unsigned char *)iname->name;
 		fname->disk_name.len = iname->len;
 		return 0;
diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index f91db24..6f4db74 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -1991,16 +1991,6 @@ int ecryptfs_encrypt_and_encode_filename(
 	return rc;
 }
 
-static bool is_dot_dotdot(const char *name, size_t name_size)
-{
-	if (name_size == 1 && name[0] == '.')
-		return true;
-	else if (name_size == 2 && name[0] == '.' && name[1] == '.')
-		return true;
-
-	return false;
-}
-
 /**
  * ecryptfs_decode_and_decrypt_filename - converts the encoded cipher text name to decoded plaintext
  * @plaintext_name: The plaintext name
@@ -2020,6 +2010,7 @@ int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
 {
 	struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
 		&ecryptfs_superblock_to_private(sb)->mount_crypt_stat;
+	const struct qstr file_name = {.name = name, .len = name_size};
 	char *decoded_name;
 	size_t decoded_name_size;
 	size_t packet_size;
@@ -2027,7 +2018,7 @@ int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
 
 	if ((mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES) &&
 	    !(mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)) {
-		if (is_dot_dotdot(name, name_size)) {
+		if (is_dot_dotdot(&file_name)) {
 			rc = ecryptfs_copy_filename(plaintext_name,
 						    plaintext_name_size,
 						    name, name_size);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 5a888a0..3d5e684 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2767,17 +2767,6 @@ static inline bool f2fs_cp_error(struct f2fs_sb_info *sbi)
 	return is_set_ckpt_flags(sbi, CP_ERROR_FLAG);
 }
 
-static inline bool is_dot_dotdot(const struct qstr *str)
-{
-	if (str->len == 1 && str->name[0] == '.')
-		return true;
-
-	if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
-		return true;
-
-	return false;
-}
-
 static inline bool f2fs_may_extent_tree(struct inode *inode)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
diff --git a/fs/libfs.c b/fs/libfs.c
index 1463b03..876b1b6 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1291,3 +1291,15 @@ bool is_empty_dir_inode(struct inode *inode)
 	return (inode->i_fop == &empty_dir_operations) &&
 		(inode->i_op == &empty_dir_inode_operations);
 }
+
+bool is_dot_dotdot(const struct qstr *str)
+{
+	if (str->len == 1 && str->name[0] == '.')
+		return true;
+
+	if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
+		return true;
+
+	return false;
+}
+EXPORT_SYMBOL(is_dot_dotdot);
diff --git a/fs/namei.c b/fs/namei.c
index 2dda552..7730a3b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2458,10 +2458,8 @@ static int lookup_one_len_common(const char *name, struct dentry *base,
 	if (!len)
 		return -EACCES;
 
-	if (unlikely(name[0] == '.')) {
-		if (len < 2 || (len == 2 && name[1] == '.'))
-			return -EACCES;
-	}
+	if (unlikely(is_dot_dotdot(this)))
+		return -EACCES;
 
 	while (len--) {
 		unsigned int c = *(const unsigned char *)name++;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c159a8b..e999826 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3627,4 +3627,6 @@ static inline int inode_drain_writes(struct inode *inode)
 	return filemap_write_and_wait(inode->i_mapping);
 }
 
+extern bool is_dot_dotdot(const struct qstr *str);
+
 #endif /* _LINUX_FS_H */
-- 
2.1.0



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^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [f2fs-dev] [PATCH] fs: introduce is_dot_dotdot helper for cleanup
       [not found] ` <20191202200302.GN20752@bombadil.infradead.org>
@ 2019-12-03  2:07   ` Tiezhu Yang
  2019-12-03  2:39     ` Darrick J. Wong
                       ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Tiezhu Yang @ 2019-12-03  2:07 UTC (permalink / raw)
  To: Matthew Wilcox
  Cc: ecryptfs, Theodore Y. Ts'o, linux-kernel, Tyler Hicks,
	Eric Biggers, linux-fscrypt, Alexander Viro, linux-fsdevel,
	Jaegeuk Kim, linux-f2fs-devel

On 12/03/2019 04:03 AM, Matthew Wilcox wrote:
> On Mon, Dec 02, 2019 at 06:10:13PM +0800, Tiezhu Yang wrote:
>> There exists many similar and duplicate codes to check "." and "..",
>> so introduce is_dot_dotdot helper to make the code more clean.
> The idea is good.  The implementation is, I'm afraid, badly chosen.
> Did you benchmark this change at all?  In general, you should prefer the
> core kernel implementation to that of some less-interesting filesystems.
> I measured the performance with the attached test program on my laptop
> (Core-i7 Kaby Lake):
>
> qstr . time_1 0.020531 time_2 0.005786
> qstr .. time_1 0.017892 time_2 0.008798
> qstr a time_1 0.017633 time_2 0.003634
> qstr matthew time_1 0.011820 time_2 0.003605
> qstr .a time_1 0.017909 time_2 0.008710
> qstr , time_1 0.017631 time_2 0.003619
>
> The results are quite stable:
>
> qstr . time_1 0.021137 time_2 0.005780
> qstr .. time_1 0.017964 time_2 0.008675
> qstr a time_1 0.017899 time_2 0.003654
> qstr matthew time_1 0.011821 time_2 0.003620
> qstr .a time_1 0.017889 time_2 0.008662
> qstr , time_1 0.017764 time_2 0.003613
>
> Feel free to suggest some different strings we could use for testing.
> These seemed like interesting strings to test with.  It's always possible
> I've messed up something with this benchmark that causes it to not
> accurately represent the performance of each algorithm, so please check
> that too.

[Sorry to resend this email because the mail list server
was denied due to it is not plain text.]

Hi Matthew,

Thanks for your reply and suggestion. I measured the
performance with the test program, the following
implementation is better for various of test cases:

bool is_dot_dotdot(const struct qstr *str)
{
         if (unlikely(str->name[0] == '.')) {
                 if (str->len < 2 || (str->len == 2 && str->name[1] == '.'))
                         return true;
         }

         return false;
}

I will send a v2 patch used with this implementation.

Thanks,

Tiezhu Yang

>
>> +bool is_dot_dotdot(const struct qstr *str)
>> +{
>> +	if (str->len == 1 && str->name[0] == '.')
>> +		return true;
>> +
>> +	if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
>> +		return true;
>> +
>> +	return false;
>> +}
>> +EXPORT_SYMBOL(is_dot_dotdot);
>> diff --git a/fs/namei.c b/fs/namei.c
>> index 2dda552..7730a3b 100644
>> --- a/fs/namei.c
>> +++ b/fs/namei.c
>> @@ -2458,10 +2458,8 @@ static int lookup_one_len_common(const char *name, struct dentry *base,
>>   	if (!len)
>>   		return -EACCES;
>>   
>> -	if (unlikely(name[0] == '.')) {
>> -		if (len < 2 || (len == 2 && name[1] == '.'))
>> -			return -EACCES;
>> -	}
>> +	if (unlikely(is_dot_dotdot(this)))
>> +		return -EACCES;
>>   
>>   	while (len--) {
>>   		unsigned int c = *(const unsigned char *)name++;



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^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [f2fs-dev] [PATCH] fs: introduce is_dot_dotdot helper for cleanup
  2019-12-03  2:07   ` Tiezhu Yang
@ 2019-12-03  2:39     ` Darrick J. Wong
  2019-12-03  8:33       ` Tiezhu Yang
  2019-12-03  2:46     ` Matthew Wilcox
  2019-12-04 13:06     ` Jean-Louis Biasini via Linux-f2fs-devel
  2 siblings, 1 reply; 6+ messages in thread
From: Darrick J. Wong @ 2019-12-03  2:39 UTC (permalink / raw)
  To: Tiezhu Yang
  Cc: ecryptfs, Theodore Y. Ts'o, linux-kernel, Matthew Wilcox,
	Tyler Hicks, Eric Biggers, linux-fscrypt, Alexander Viro,
	linux-fsdevel, Jaegeuk Kim, linux-f2fs-devel

On Tue, Dec 03, 2019 at 10:07:41AM +0800, Tiezhu Yang wrote:
> On 12/03/2019 04:03 AM, Matthew Wilcox wrote:
> > On Mon, Dec 02, 2019 at 06:10:13PM +0800, Tiezhu Yang wrote:
> > > There exists many similar and duplicate codes to check "." and "..",
> > > so introduce is_dot_dotdot helper to make the code more clean.
> > The idea is good.  The implementation is, I'm afraid, badly chosen.
> > Did you benchmark this change at all?  In general, you should prefer the
> > core kernel implementation to that of some less-interesting filesystems.
> > I measured the performance with the attached test program on my laptop
> > (Core-i7 Kaby Lake):
> > 
> > qstr . time_1 0.020531 time_2 0.005786
> > qstr .. time_1 0.017892 time_2 0.008798
> > qstr a time_1 0.017633 time_2 0.003634
> > qstr matthew time_1 0.011820 time_2 0.003605
> > qstr .a time_1 0.017909 time_2 0.008710
> > qstr , time_1 0.017631 time_2 0.003619
> > 
> > The results are quite stable:
> > 
> > qstr . time_1 0.021137 time_2 0.005780
> > qstr .. time_1 0.017964 time_2 0.008675
> > qstr a time_1 0.017899 time_2 0.003654
> > qstr matthew time_1 0.011821 time_2 0.003620
> > qstr .a time_1 0.017889 time_2 0.008662
> > qstr , time_1 0.017764 time_2 0.003613
> > 
> > Feel free to suggest some different strings we could use for testing.
> > These seemed like interesting strings to test with.  It's always possible
> > I've messed up something with this benchmark that causes it to not
> > accurately represent the performance of each algorithm, so please check
> > that too.
> 
> [Sorry to resend this email because the mail list server
> was denied due to it is not plain text.]
> 
> Hi Matthew,
> 
> Thanks for your reply and suggestion. I measured the
> performance with the test program, the following
> implementation is better for various of test cases:
> 
> bool is_dot_dotdot(const struct qstr *str)
> {
>         if (unlikely(str->name[0] == '.')) {
>                 if (str->len < 2 || (str->len == 2 && str->name[1] == '.'))
>                         return true;
>         }
> 
>         return false;
> }
> 
> I will send a v2 patch used with this implementation.

Can you make it a static inline since it's such a short function?

--D

> Thanks,
> 
> Tiezhu Yang
> 
> > 
> > > +bool is_dot_dotdot(const struct qstr *str)
> > > +{
> > > +	if (str->len == 1 && str->name[0] == '.')
> > > +		return true;
> > > +
> > > +	if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
> > > +		return true;
> > > +
> > > +	return false;
> > > +}
> > > +EXPORT_SYMBOL(is_dot_dotdot);
> > > diff --git a/fs/namei.c b/fs/namei.c
> > > index 2dda552..7730a3b 100644
> > > --- a/fs/namei.c
> > > +++ b/fs/namei.c
> > > @@ -2458,10 +2458,8 @@ static int lookup_one_len_common(const char *name, struct dentry *base,
> > >   	if (!len)
> > >   		return -EACCES;
> > > -	if (unlikely(name[0] == '.')) {
> > > -		if (len < 2 || (len == 2 && name[1] == '.'))
> > > -			return -EACCES;
> > > -	}
> > > +	if (unlikely(is_dot_dotdot(this)))
> > > +		return -EACCES;
> > >   	while (len--) {
> > >   		unsigned int c = *(const unsigned char *)name++;
> 


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^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [f2fs-dev] [PATCH] fs: introduce is_dot_dotdot helper for cleanup
  2019-12-03  2:07   ` Tiezhu Yang
  2019-12-03  2:39     ` Darrick J. Wong
@ 2019-12-03  2:46     ` Matthew Wilcox
  2019-12-04 13:06     ` Jean-Louis Biasini via Linux-f2fs-devel
  2 siblings, 0 replies; 6+ messages in thread
From: Matthew Wilcox @ 2019-12-03  2:46 UTC (permalink / raw)
  To: Tiezhu Yang
  Cc: ecryptfs, Theodore Y. Ts'o, linux-kernel, Tyler Hicks,
	Eric Biggers, linux-fscrypt, Alexander Viro, linux-fsdevel,
	Jaegeuk Kim, linux-f2fs-devel

On Tue, Dec 03, 2019 at 10:07:41AM +0800, Tiezhu Yang wrote:
> On 12/03/2019 04:03 AM, Matthew Wilcox wrote:
> > On Mon, Dec 02, 2019 at 06:10:13PM +0800, Tiezhu Yang wrote:
> > > There exists many similar and duplicate codes to check "." and "..",
> > > so introduce is_dot_dotdot helper to make the code more clean.
> > The idea is good.  The implementation is, I'm afraid, badly chosen.
> > Did you benchmark this change at all?  In general, you should prefer the
> 
> Thanks for your reply and suggestion. I measured the
> performance with the test program, the following
> implementation is better for various of test cases:
> 
> bool is_dot_dotdot(const struct qstr *str)
> {
>         if (unlikely(str->name[0] == '.')) {
>                 if (str->len < 2 || (str->len == 2 && str->name[1] == '.'))
>                         return true;
>         }
> 
>         return false;
> }
> 
> I will send a v2 patch used with this implementation.

Well, hang on.  If you haven't done any benchmarking, please do so
before sending a v2.  In particular, you've now moved this to being a
function call.  That might slow things down, or it might speed things up.
I also don't know if passing a qstr is going to be the right API --
let's hear from the filesystems affected by the API change that they're
OK with this change.


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Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [f2fs-dev] [PATCH] fs: introduce is_dot_dotdot helper for cleanup
  2019-12-03  2:39     ` Darrick J. Wong
@ 2019-12-03  8:33       ` Tiezhu Yang
  0 siblings, 0 replies; 6+ messages in thread
From: Tiezhu Yang @ 2019-12-03  8:33 UTC (permalink / raw)
  To: Darrick J. Wong
  Cc: ecryptfs, Theodore Y. Ts'o, linux-kernel, Matthew Wilcox,
	Tyler Hicks, Eric Biggers, linux-fscrypt, Alexander Viro,
	linux-fsdevel, Jaegeuk Kim, linux-f2fs-devel

On 12/03/2019 10:39 AM, Darrick J. Wong wrote:
> On Tue, Dec 03, 2019 at 10:07:41AM +0800, Tiezhu Yang wrote:
>> On 12/03/2019 04:03 AM, Matthew Wilcox wrote:
>>> On Mon, Dec 02, 2019 at 06:10:13PM +0800, Tiezhu Yang wrote:
>>>> There exists many similar and duplicate codes to check "." and "..",
>>>> so introduce is_dot_dotdot helper to make the code more clean.
>>> The idea is good.  The implementation is, I'm afraid, badly chosen.
>>> Did you benchmark this change at all?  In general, you should prefer the
>>> core kernel implementation to that of some less-interesting filesystems.
>>> I measured the performance with the attached test program on my laptop
>>> (Core-i7 Kaby Lake):
>>>
>>> qstr . time_1 0.020531 time_2 0.005786
>>> qstr .. time_1 0.017892 time_2 0.008798
>>> qstr a time_1 0.017633 time_2 0.003634
>>> qstr matthew time_1 0.011820 time_2 0.003605
>>> qstr .a time_1 0.017909 time_2 0.008710
>>> qstr , time_1 0.017631 time_2 0.003619
>>>
>>> The results are quite stable:
>>>
>>> qstr . time_1 0.021137 time_2 0.005780
>>> qstr .. time_1 0.017964 time_2 0.008675
>>> qstr a time_1 0.017899 time_2 0.003654
>>> qstr matthew time_1 0.011821 time_2 0.003620
>>> qstr .a time_1 0.017889 time_2 0.008662
>>> qstr , time_1 0.017764 time_2 0.003613
>>>
>>> Feel free to suggest some different strings we could use for testing.
>>> These seemed like interesting strings to test with.  It's always possible
>>> I've messed up something with this benchmark that causes it to not
>>> accurately represent the performance of each algorithm, so please check
>>> that too.
>> [Sorry to resend this email because the mail list server
>> was denied due to it is not plain text.]
>>
>> Hi Matthew,
>>
>> Thanks for your reply and suggestion. I measured the
>> performance with the test program, the following
>> implementation is better for various of test cases:
>>
>> bool is_dot_dotdot(const struct qstr *str)
>> {
>>          if (unlikely(str->name[0] == '.')) {
>>                  if (str->len < 2 || (str->len == 2 && str->name[1] == '.'))
>>                          return true;
>>          }
>>
>>          return false;
>> }
>>
>> I will send a v2 patch used with this implementation.
> Can you make it a static inline since it's such a short function?

Thanks for your suggestion, I will make it static inline and
move it to include/linux/fs.h in the v2 patch.

Thanks,

Tiezhu Yang

>
> --D
>
>> Thanks,
>>
>> Tiezhu Yang
>>
>>>> +bool is_dot_dotdot(const struct qstr *str)
>>>> +{
>>>> +	if (str->len == 1 && str->name[0] == '.')
>>>> +		return true;
>>>> +
>>>> +	if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
>>>> +		return true;
>>>> +
>>>> +	return false;
>>>> +}
>>>> +EXPORT_SYMBOL(is_dot_dotdot);
>>>> diff --git a/fs/namei.c b/fs/namei.c
>>>> index 2dda552..7730a3b 100644
>>>> --- a/fs/namei.c
>>>> +++ b/fs/namei.c
>>>> @@ -2458,10 +2458,8 @@ static int lookup_one_len_common(const char *name, struct dentry *base,
>>>>    	if (!len)
>>>>    		return -EACCES;
>>>> -	if (unlikely(name[0] == '.')) {
>>>> -		if (len < 2 || (len == 2 && name[1] == '.'))
>>>> -			return -EACCES;
>>>> -	}
>>>> +	if (unlikely(is_dot_dotdot(this)))
>>>> +		return -EACCES;
>>>>    	while (len--) {
>>>>    		unsigned int c = *(const unsigned char *)name++;



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^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [f2fs-dev] [PATCH] fs: introduce is_dot_dotdot helper for cleanup
  2019-12-03  2:07   ` Tiezhu Yang
  2019-12-03  2:39     ` Darrick J. Wong
  2019-12-03  2:46     ` Matthew Wilcox
@ 2019-12-04 13:06     ` Jean-Louis Biasini via Linux-f2fs-devel
  2 siblings, 0 replies; 6+ messages in thread
From: Jean-Louis Biasini via Linux-f2fs-devel @ 2019-12-04 13:06 UTC (permalink / raw)
  To: Tiezhu Yang, Matthew Wilcox
  Cc: ecryptfs, Theodore Y. Ts'o, linux-kernel, Tyler Hicks,
	Eric Biggers, linux-fscrypt, Alexander Viro, linux-fsdevel,
	Jaegeuk Kim, linux-f2fs-devel

Please UNSUBSCRIBE ME from this list of tell how to!!!

Le 03/12/2019 à 03:07, Tiezhu Yang a écrit :
> On 12/03/2019 04:03 AM, Matthew Wilcox wrote:
>> On Mon, Dec 02, 2019 at 06:10:13PM +0800, Tiezhu Yang wrote:
>>> There exists many similar and duplicate codes to check "." and "..",
>>> so introduce is_dot_dotdot helper to make the code more clean.
>> The idea is good.  The implementation is, I'm afraid, badly chosen.
>> Did you benchmark this change at all?  In general, you should prefer the
>> core kernel implementation to that of some less-interesting filesystems.
>> I measured the performance with the attached test program on my laptop
>> (Core-i7 Kaby Lake):
>>
>> qstr . time_1 0.020531 time_2 0.005786
>> qstr .. time_1 0.017892 time_2 0.008798
>> qstr a time_1 0.017633 time_2 0.003634
>> qstr matthew time_1 0.011820 time_2 0.003605
>> qstr .a time_1 0.017909 time_2 0.008710
>> qstr , time_1 0.017631 time_2 0.003619
>>
>> The results are quite stable:
>>
>> qstr . time_1 0.021137 time_2 0.005780
>> qstr .. time_1 0.017964 time_2 0.008675
>> qstr a time_1 0.017899 time_2 0.003654
>> qstr matthew time_1 0.011821 time_2 0.003620
>> qstr .a time_1 0.017889 time_2 0.008662
>> qstr , time_1 0.017764 time_2 0.003613
>>
>> Feel free to suggest some different strings we could use for testing.
>> These seemed like interesting strings to test with.  It's always
>> possible
>> I've messed up something with this benchmark that causes it to not
>> accurately represent the performance of each algorithm, so please check
>> that too.
>
> [Sorry to resend this email because the mail list server
> was denied due to it is not plain text.]
>
> Hi Matthew,
>
> Thanks for your reply and suggestion. I measured the
> performance with the test program, the following
> implementation is better for various of test cases:
>
> bool is_dot_dotdot(const struct qstr *str)
> {
>         if (unlikely(str->name[0] == '.')) {
>                 if (str->len < 2 || (str->len == 2 && str->name[1] ==
> '.'))
>                         return true;
>         }
>
>         return false;
> }
>
> I will send a v2 patch used with this implementation.
>
> Thanks,
>
> Tiezhu Yang
>
>>
>>> +bool is_dot_dotdot(const struct qstr *str)
>>> +{
>>> +    if (str->len == 1 && str->name[0] == '.')
>>> +        return true;
>>> +
>>> +    if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
>>> +        return true;
>>> +
>>> +    return false;
>>> +}
>>> +EXPORT_SYMBOL(is_dot_dotdot);
>>> diff --git a/fs/namei.c b/fs/namei.c
>>> index 2dda552..7730a3b 100644
>>> --- a/fs/namei.c
>>> +++ b/fs/namei.c
>>> @@ -2458,10 +2458,8 @@ static int lookup_one_len_common(const char
>>> *name, struct dentry *base,
>>>       if (!len)
>>>           return -EACCES;
>>>   -    if (unlikely(name[0] == '.')) {
>>> -        if (len < 2 || (len == 2 && name[1] == '.'))
>>> -            return -EACCES;
>>> -    }
>>> +    if (unlikely(is_dot_dotdot(this)))
>>> +        return -EACCES;
>>>         while (len--) {
>>>           unsigned int c = *(const unsigned char *)name++;
>



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^ permalink raw reply	[flat|nested] 6+ messages in thread

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Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-12-02 10:10 [f2fs-dev] [PATCH] fs: introduce is_dot_dotdot helper for cleanup Tiezhu Yang
     [not found] ` <20191202200302.GN20752@bombadil.infradead.org>
2019-12-03  2:07   ` Tiezhu Yang
2019-12-03  2:39     ` Darrick J. Wong
2019-12-03  8:33       ` Tiezhu Yang
2019-12-03  2:46     ` Matthew Wilcox
2019-12-04 13:06     ` Jean-Louis Biasini via Linux-f2fs-devel

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