| Message ID | 20160824221429.21158-1-ross.zwisler@linux.intel.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 11bd969 |
| Headers | show |
On Wed, 24 Aug 2016 16:14:29 -0600 Ross Zwisler <ross.zwisler@linux.intel.com> wrote: > 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 <ross.zwisler@linux.intel.com> > Reported-by: Jeff Moyer <jmoyer@redhat.com> cc:stable [4.5+] ?
diff --git a/mm/readahead.c b/mm/readahead.c index 65ec288..c8a955b 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 +545,14 @@ do_readahead(struct address_space *mapping, struct file *filp, if (!mapping || !mapping->a_ops) return -EINVAL; + /* + * 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. + */ + if (dax_mapping(mapping)) + return 0; + return force_page_cache_readahead(mapping, filp, index, nr); }
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 <ross.zwisler@linux.intel.com> Reported-by: Jeff Moyer <jmoyer@redhat.com> --- Changes from v1: - Added a comment so readers don't have to go putzing around in the git tree to understand why we're doing what we're doing. :) (akpm) --- mm/readahead.c | 9 +++++++++ 1 file changed, 9 insertions(+)