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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: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
This commit is contained in:
Jan Kara 2016-05-12 18:29:17 +02:00 committed by Ross Zwisler
parent e804315dd0
commit 4f622938a5
2 changed files with 15 additions and 7 deletions
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1
include/linux/dax.h
View File

@ -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 */

21
mm/filemap.c
View File

@ -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;
if (shadowp)
*shadowp = p;
mapping->nrexceptional--;
if (node)
workingset_node_shadows_dec(node);
if (!dax_mapping(mapping)) {
if (shadowp)
*shadowp = p;
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++;