dax: Fix missed wakeup with PMD faults
RocksDB can hang indefinitely when using a DAX file. This is due to a bug in the XArray conversion when handling a PMD fault and finding a PTE entry. We use the wrong index in the hash and end up waiting on the wrong waitqueue. There's actually no need to wait; if we find a PTE entry while looking for a PMD entry, we can return immediately as we know we should fall back to a PTE fault (which may not conflict with the lock held). We reuse the XA_RETRY_ENTRY to signal a conflicting entry was found. This value can never be found in an XArray while holding its lock, so it does not create an ambiguity. Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/CAPcyv4hwHpX-MkUEqxwdTj7wCCZCN4RV-L4jsnuwLGyL_UEG4A@mail.gmail.com Fixes: b15cd800 ("dax: Convert page fault handlers to XArray") Signed-off-by:Matthew Wilcox (Oracle) <willy@infradead.org> Tested-by:
Dan Williams <dan.j.williams@intel.com> Reported-by:
Robert Barror <robert.barror@intel.com> Reported-by:
Seema Pandit <seema.pandit@intel.com> Reviewed-by:
Jan Kara <jack@suse.cz> Signed-off-by:
Dan Williams <dan.j.williams@intel.com>
parent
40cdc60a
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