On 08/08/2014 08:48 PM, Dave Chinner wrote:
> On Fri, Aug 08, 2014 at 12:04:40PM -0400, Chris Mason wrote:
>> xfs is using truncate_pagecache_range to invalidate the page cache
>> during DIO writes. The other filesystems are calling
>> truncate_pagecache_range is meant to be used when we are freeing the
>> underlying data structs from disk, so it will zero any partial ranges
>> in the page. This means a DIO write can zero out part of the page cache
>> page, and it is possible the page will stay in cache.
>> This one is an RFC because it is untested and because I don't understand
>> how XFS is dealing with pages the truncate was unable to clear away.
>> I'm not able to actually trigger zeros by mixing DIO writes with
>> buffered reads.
>> Signed-off-by: Chris Mason <clm@xxxxxx>
>> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
>> index 8d25d98..c30c112 100644
>> --- a/fs/xfs/xfs_file.c
>> +++ b/fs/xfs/xfs_file.c
>> @@ -638,7 +638,10 @@ xfs_file_dio_aio_write(
>> pos, -1);
>> if (ret)
>> goto out;
>> - truncate_pagecache_range(VFS_I(ip), pos, -1);
>> + /* what do we do if we can't invalidate the pages? */
>> + invalidate_inode_pages2_range(VFS_I(ip)->i_mapping,
>> + pos >> PAGE_CACHE_SHIFT, -1);
> I don't think it can on XFS.
> We're holding the XFS_IOLOCK_EXCL, so no other syscall based IO can
> dirty pages, all the pages are clean, try_to_free_buffers() will
> never fail, no-one can run a truncate operation concurently, and
> so on.
> So, I'd just do:
> ret = invalidate_inode_pages2_range(VFS_I(ip)->i_mapping,
> pos >> PAGE_CACHE_SHIFT, -1);
> ret = 0;
Since pos is page aligned I agree this should be fine. I'll leave that
one to you though, since I don't have a great test case for/against it.