linux-ext4 - Re: [PATCH v2 2/2] [PATCH] xfs: Close race between direct IO and xfs_break

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]

Message-ID: <af6a4411-3362-66a2-5291-4006b56b5441@intel.com>
Date:   Thu, 9 Aug 2018 09:21:25 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Jan Kara <jack@...e.cz>
Cc:     tytso@....edu, darrick.wong@...cle.com, zwisler@...nel.org,
        linux-nvdimm@...ts.01.org, david@...morbit.com,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        lczerner@...hat.com, linux-ext4@...r.kernel.org, hch@....de
Subject: Re: [PATCH v2 2/2] [PATCH] xfs: Close race between direct IO and
 xfs_break_layouts()



On 08/09/2018 01:57 AM, Jan Kara wrote:
> On Wed 08-08-18 10:26:36, Dave Jiang wrote:
>> This patch is the duplicate of ross's fix for ext4 for xfs.
>>
>> If the refcount of a page is lowered between the time that it is returned
>> by dax_busy_page() and when the refcount is again checked in
>> xfs_break_layouts() => ___wait_var_event(), the waiting function
>> xfs_wait_dax_page() will never be called.  This means that
>> xfs_break_layouts() will still have 'retry' set to false, so we'll stop
>> looping and never check the refcount of other pages in this inode.
>>
>> Instead, always continue looping as long as dax_layout_busy_page() gives us
>> a page which it found with an elevated refcount.
>>
>> Signed-off-by: Dave Jiang <dave.jiang@...el.com>
> 
> I think I gave you my reviewed-by tag already for the previous version. But
> here it is again:
> 
> Reviewed-by: Jan Kara <jack@...e.cz>

Yes you did. I forgot to append it when I sent it out the first time. I
resent it. :)

> 
> 								Honza
> 
>> ---
>>
>> v2:
>> - Rename parameter from did_unlock to retry (Jan) 
>>
>>  fs/xfs/xfs_file.c |    9 ++++-----
>>  1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
>> index a3e7767a5715..cd6f0d8c4922 100644
>> --- a/fs/xfs/xfs_file.c
>> +++ b/fs/xfs/xfs_file.c
>> @@ -721,12 +721,10 @@ xfs_file_write_iter(
>>  
>>  static void
>>  xfs_wait_dax_page(
>> -	struct inode		*inode,
>> -	bool			*did_unlock)
>> +	struct inode		*inode)
>>  {
>>  	struct xfs_inode        *ip = XFS_I(inode);
>>  
>> -	*did_unlock = true;
>>  	xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
>>  	schedule();
>>  	xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
>> @@ -736,7 +734,7 @@ static int
>>  xfs_break_dax_layouts(
>>  	struct inode		*inode,
>>  	uint			iolock,
>> -	bool			*did_unlock)
>> +	bool			*retry)
>>  {
>>  	struct page		*page;
>>  
>> @@ -746,9 +744,10 @@ xfs_break_dax_layouts(
>>  	if (!page)
>>  		return 0;
>>  
>> +	*retry = true;
>>  	return ___wait_var_event(&page->_refcount,
>>  			atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
>> -			0, 0, xfs_wait_dax_page(inode, did_unlock));
>> +			0, 0, xfs_wait_dax_page(inode));
>>  }
>>  
>>  int
>>