4.19-stable review patch. If anyone has any objections, please let me know.
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From: Matthew Wilcox willy@infradead.org
commit c93db7bb6ef3251e0ea48ade311d3e9942748e1c upstream.
If we race with inode destroy, it's possible for page->mapping to be NULL before we even enter this routine, as well as after having slept waiting for the dax entry to become unlocked.
Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()") Cc: stable@vger.kernel.org Reported-by: Jan Kara jack@suse.cz Signed-off-by: Matthew Wilcox willy@infradead.org Reviewed-by: Johannes Thumshirn jthumshirn@suse.de Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/dax.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/dax.c +++ b/fs/dax.c @@ -423,7 +423,7 @@ bool dax_lock_mapping_entry(struct page for (;;) { mapping = READ_ONCE(page->mapping);
- if (!dax_mapping(mapping)) + if (!mapping || !dax_mapping(mapping)) break;
/*