On Sat, Aug 09, 2014 at 08:57:00AM -0400, Chris Mason wrote:
> xfs is using truncate_pagecache_range to invalidate the page cache
> during DIO reads. This is different from the other filesystems who only
> invalidate pages during DIO writes.
> 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 read can zero out part of the page cache
> page, and it is possible the page will stay in cache.
> buffered reads will find an up to date page with zeros instead of the
> data actually on disk.
> This patch fixes things by using invalidate_inode_pages2_range instead.
> It preserves the page cache invalidation, but won't zero any pages.
> Signed-off-by: Chris Mason <clm@xxxxxx>
> cc: stable@xxxxxxxxxxxxxxx
I can't say I grok the risk of removing the invalidation entirely, but
this is certainly a more isolated fix:
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> fs/xfs/xfs_file.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 1f66779..023d575 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -295,7 +295,8 @@ xfs_file_read_iter(
> xfs_rw_iunlock(ip, XFS_IOLOCK_EXCL);
> return ret;
> - truncate_pagecache_range(VFS_I(ip), pos, -1);
> + invalidate_inode_pages2_range(VFS_I(ip)->i_mapping,
> + pos >> PAGE_CACHE_SHIFT, -1);
> xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
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