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Commit 4f622938 authored by Jan Kara's avatar Jan Kara Committed by Ross Zwisler
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dax: Allow DAX code to replace exceptional entries 



Currently we forbid page_cache_tree_insert() to replace exceptional radix
tree entries for DAX inodes. However to make DAX faults race free we will
lock radix tree entries and when hole is created, we need to replace
such locked radix tree entry with a hole page. So modify
page_cache_tree_insert() to allow that.

Reviewed-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
parent e804315d

include/linux/dax.h

+1 −0
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 


#include <linux/fs.h>

#include <linux/mm.h>

#include <linux/radix-tree.h>

#include <asm/pgtable.h>



/* We use lowest available exceptional entry bit for locking */

mm/filemap.c

+14 −7
Original line number Diff line number Diff line
@@ -597,14 +597,21 @@ static int page_cache_tree_insert(struct address_space *mapping, 
		if (!radix_tree_exceptional_entry(p))

			return -EEXIST;



		if (WARN_ON(dax_mapping(mapping)))

			return -EINVAL;



		mapping->nrexceptional--;

		if (!dax_mapping(mapping)) {

			if (shadowp)

				*shadowp = p;

		mapping->nrexceptional--;

			if (node)

				workingset_node_shadows_dec(node);

		} else {

			/* DAX can replace empty locked entry with a hole */

			WARN_ON_ONCE(p !=

				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |

					 RADIX_DAX_ENTRY_LOCK));

			/* DAX accounts exceptional entries as normal pages */

			if (node)

				workingset_node_pages_dec(node);

		}

	}

	radix_tree_replace_slot(slot, page);

	mapping->nrpages++;