Re: [PATCH] vfs: allow custom EOF in generic_file_llseek code

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 4/27/12 5:47 PM, Bernd Schubert wrote:
> On 04/27/2012 06:21 PM, Eric Sandeen wrote:

...

>> +generic_file_llseek_size_eof(struct file *file, loff_t offset, int origin,
>> +		loff_t maxsize, loff_t eof)
>>  {
>>  	struct inode *inode = file->f_mapping->host;
>>  
>>  	switch (origin) {
>>  	case SEEK_END:
>> -		offset += i_size_read(inode);
>> +		offset += eof;
>>  		break;
> 
> Here is the only glitch I can see. As Andreas already said before, it
> might overflow here. Do we need do care about that? As you already said,
> SEEK_END is unlikely to be ever called for directories. But then we also
> cannot keep user space from doing weird calls...

It can happen already today, for a sufficiently large file offset.

# ls -l reallybigfile 
-rw-r--r--. 1 root root 9223372036854775807 Apr 27 18:02 reallybigfile

(that's 2^63 - 1)

so overflow protection may be warranted in here, but I think it's a separate problem.

...

>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index 8de6755..a6ae7a4 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -2402,6 +2402,8 @@ extern loff_t no_llseek(struct file *file, loff_t offset, int origin);
>>  extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);
>>  extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,
>>  		int origin, loff_t maxsize);
>> +extern loff_t generic_file_llseek_size_eof(struct file *file, loff_t offset,
>> +		int origin, loff_t maxsize, loff_t eof);
>>  extern int generic_file_open(struct inode * inode, struct file * filp);
>>  extern int nonseekable_open(struct inode * inode, struct file * filp);
> 
> Another question, wouldn't it be better to entirely move
> generic_file_llseek_size() and generic_file_llseek() into fs.h to make
> sure it gets inlined?

Hm, perhaps.  It wasn't done for generic_file_llseek_size() so I just followed
that example, for now.

-Eric
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux