linux-kernel - Re: [PATCH v2 2/3] fs/file.c: conditionally clear full

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date: Tue, 25 Jun 2024 23:41:30 +0800
From: "Ma, Yu" <yu.ma@...el.com>
To: Jan Kara <jack@...e.cz>
Cc: viro@...iv.linux.org.uk, brauner@...nel.org, mjguzik@...il.com,
 edumazet@...gle.com, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, pan.deng@...el.com, tianyou.li@...el.com,
 tim.c.chen@...el.com, tim.c.chen@...ux.intel.com, yu.ma@...el.com
Subject: Re: [PATCH v2 2/3] fs/file.c: conditionally clear full_fds


On 6/25/2024 7:54 PM, Jan Kara wrote:
> On Sat 22-06-24 11:49:03, Yu Ma wrote:
>> 64 bits in open_fds are mapped to a common bit in full_fds_bits. It is very
>> likely that a bit in full_fds_bits has been cleared before in
>> __clear_open_fds()'s operation. Check the clear bit in full_fds_bits before
>> clearing to avoid unnecessary write and cache bouncing. See commit fc90888d07b8
>> ("vfs: conditionally clear close-on-exec flag") for a similar optimization.
>> Together with patch 1, they improves pts/blogbench-1.1.0 read for 27%, and write
>> for 14% on Intel ICX 160 cores configuration with v6.10-rc4.
>>
>> Reviewed-by: Tim Chen <tim.c.chen@...ux.intel.com>
>> Signed-off-by: Yu Ma <yu.ma@...el.com>
> Nice. Feel free to add:
>
> Reviewed-by: Jan Kara <jack@...e.cz>
>
> 								Honza

Copy that, thanks Honza :)


>> ---
>>   fs/file.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/file.c b/fs/file.c
>> index 50e900a47107..b4d25f6d4c19 100644
>> --- a/fs/file.c
>> +++ b/fs/file.c
>> @@ -268,7 +268,9 @@ static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
>>   static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
>>   {
>>   	__clear_bit(fd, fdt->open_fds);
>> -	__clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
>> +	fd /= BITS_PER_LONG;
>> +	if (test_bit(fd, fdt->full_fds_bits))
>> +	    __clear_bit(fd, fdt->full_fds_bits);
>>   }
>>   
>>   static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)
>> -- 
>> 2.43.0
>>