Ever since the conversion of DAX to the Xarray a RocksDB benchmark has been encountering intermittent lockups. The backtraces always include the filesystem-DAX PMD path, multi-order entries have been a source of bugs in the past, and disabling the PMD path allows a test that fails in minutes to run for an hour.
The regression has been bisected to "dax: Convert page fault handlers to XArray", but little progress has been made on the root cause debug. Unless / until root cause can be identified mark CONFIG_FS_DAX_PMD broken to preclude intermittent lockups. Reverting the Xarray conversion also works, but that change is too big to backport. The implementation is committed to Xarray at this point.
Link: https://lore.kernel.org/linux-fsdevel/CAPcyv4hwHpX-MkUEqxwdTj7wCCZCN4RV-L4js... Fixes: b15cd800682f ("dax: Convert page fault handlers to XArray") Cc: Matthew Wilcox willy@infradead.org Cc: Jan Kara jack@suse.cz Cc: stable@vger.kernel.org Reported-by: Robert Barror robert.barror@intel.com Reported-by: Seema Pandit seema.pandit@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com --- fs/Kconfig | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/Kconfig b/fs/Kconfig index f1046cf6ad85..85eecd0d4c5d 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -66,6 +66,9 @@ config FS_DAX_PMD depends on FS_DAX depends on ZONE_DEVICE depends on TRANSPARENT_HUGEPAGE + # intermittent lockups since commit b15cd800682f "dax: Convert + # page fault handlers to XArray" + depends on BROKEN
# Selected by DAX drivers that do not expect filesystem DAX to support # get_user_pages() of DAX mappings. I.e. "limited" indicates no support