linux-kernel - Re: [f2fs-dev] [PATCH 1/1] f2fs: allocate trace path buffer from names

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Date:   Wed, 19 Apr 2023 09:32:15 +0800
From:   Wu Bo <bo.wu@...o.com>
To:     chao@...nel.org
Cc:     bo.wu@...o.com, jaegeuk@...nel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, wubo.oduw@...il.com
Subject: Re: [f2fs-dev] [PATCH 1/1] f2fs: allocate trace path buffer from names_cache

On 2023/4/18 23:51, Chao Yu wrote:
> On 2023/4/14 18:43, Wu Bo wrote:
>> It would be better to use the dedicated slab to store path.
>>
>> Signed-off-by: Wu Bo <bo.wu@...o.com>
>> ---
>>   fs/f2fs/file.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>> index 15dabeac4690..27137873958f 100644
>> --- a/fs/f2fs/file.c
>> +++ b/fs/f2fs/file.c
>> @@ -4361,7 +4361,7 @@ static void f2fs_trace_rw_file_path(struct
>> kiocb *iocb, size_t count, int rw)
>>       struct inode *inode = file_inode(iocb->ki_filp);
>>       char *buf, *path;
>>   -    buf = f2fs_kmalloc(F2FS_I_SB(inode), PATH_MAX, GFP_KERNEL);
>> +    buf = __getname();
>
> How about:
>
> buf = f2fs_kmem_cache_alloc(names_cachep, GFP_KERNEL, NULL,
> F2FS_I_SB(inode));

Using f2fs_kmem_cache_alloc is able to inject malloc error.
But here is a trace event, is it ok to inject error in a trace path?

>
>>       if (!buf)
>>           return;
>>       path = dentry_path_raw(file_dentry(iocb->ki_filp), buf, PATH_MAX);
>> @@ -4374,7 +4374,7 @@ static void f2fs_trace_rw_file_path(struct
>> kiocb *iocb, size_t count, int rw)
>>           trace_f2fs_dataread_start(inode, iocb->ki_pos, count,
>>                   current->pid, path, current->comm);
>>   free_buf:
>> -    kfree(buf);
>> +    __putname(buf);
>
> kmem_cache_free(names_cachep, buf);
>
> Thanks,
>
>>   }
>>     static ssize_t f2fs_file_read_iter(struct kiocb *iocb, struct
>> iov_iter *to)
>
>
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