Commit 11bd969f authored by Ross Zwisler's avatar Ross Zwisler Committed by Linus Torvalds

mm: silently skip readahead for DAX inodes

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.

Link: http://lkml.kernel.org/r/20160824221429.21158-1-ross.zwisler@linux.intel.comSigned-off-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Reported-by: default avatarJeff Moyer <jmoyer@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: <stable@vger.kernel.org>	[4.5+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d0e58455
...@@ -8,6 +8,7 @@ ...@@ -8,6 +8,7 @@
*/ */
#include <linux/kernel.h> #include <linux/kernel.h>
#include <linux/dax.h>
#include <linux/gfp.h> #include <linux/gfp.h>
#include <linux/export.h> #include <linux/export.h>
#include <linux/blkdev.h> #include <linux/blkdev.h>
...@@ -544,6 +545,14 @@ do_readahead(struct address_space *mapping, struct file *filp, ...@@ -544,6 +545,14 @@ do_readahead(struct address_space *mapping, struct file *filp,
if (!mapping || !mapping->a_ops) if (!mapping || !mapping->a_ops)
return -EINVAL; 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); return force_page_cache_readahead(mapping, filp, index, nr);
} }
......
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