On Sat, Oct 19, 2019 at 09:26:19AM -0700, Dan Williams wrote:
Check for NULL entries before checking the entry order, otherwise NULL is misinterpreted as a present pte conflict. The 'order' check needs to happen before the locked check as an unlocked entry at the wrong order must fallback to lookup the correct order.
Reported-by: Jeff Smits jeff.smits@intel.com Reported-by: Doug Nelson doug.nelson@intel.com Cc: stable@vger.kernel.org Fixes: 23c84eb78375 ("dax: Fix missed wakeup with PMD faults") Cc: Jan Kara jack@suse.cz Cc: Matthew Wilcox (Oracle) willy@infradead.org Signed-off-by: Dan Williams dan.j.williams@intel.com
fs/dax.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c index a71881e77204..08160011d94c 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -221,10 +221,11 @@ static void *get_unlocked_entry(struct xa_state *xas, unsigned int order) for (;;) { entry = xas_find_conflict(xas);
if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))return entry;
if (!entry || WARN_ON_ONCE(!xa_is_value(entry)) ||!dax_is_locked(entry))
if (!dax_is_locked(entry)) return entry;
Yes, I think this works. Should we also add:
static unsigned int dax_entry_order(void *entry) { + BUG_ON(!xa_is_value(entry)); if (xa_to_value(entry) & DAX_PMD) return PMD_ORDER; return 0; }
which would have caught this logic error before it caused a performance regression?