For DAX inodes we need to be careful to never have page cache pages in the mapping->page_tree. This radix tree should be composed only of DAX exceptional entries and zero pages.
ltp's readahead02 test was triggering a warning because we were trying to insert a DAX exceptional entry but found that a page cache page had already been inserted into the tree. This page was being inserted into the radix tree in response to a readahead(2) call. Readahead doesn't make sense for DAX inodes, but we don't want it to report a failure either. Instead, we just return success and don't do any work. Signed-off-by: Ross Zwisler <[email protected]> Reported-by: Jeff Moyer <[email protected]> Cc: [email protected] --- mm/readahead.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/readahead.c b/mm/readahead.c index 65ec288..a9ba1be 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -8,6 +8,7 @@ */ #include <linux/kernel.h> +#include <linux/dax.h> #include <linux/gfp.h> #include <linux/export.h> #include <linux/blkdev.h> @@ -544,6 +545,9 @@ do_readahead(struct address_space *mapping, struct file *filp, if (!mapping || !mapping->a_ops) return -EINVAL; + if (dax_mapping(mapping)) + return 0; + return force_page_cache_readahead(mapping, filp, index, nr); } -- 2.9.0
