Hi, This patchset fixes two subtle issues discovered while unit testing nr_hw_queue update code using null_blk driver. The first patch in the series, fixes an issue in the sbitmap initialization code, where sb->alloc_hint is not explicitly set to NULL when the sbitmap depth is zero. This can lead to a kernel crash in sbitmap_free(), which unconditionally calls free_percpu() on sb->alloc_hint — even if it was never allocated. The crash is caused by dereferencing an invalid pointer or stale garbage value. The second patch in the series fixes a bug in the null_blk driver where the driver_data field of the tagset is not properly initialized when setting up shared tagsets. This omission causes null_map_queues() to fail during nr_hw_queues update, leading to no software queues (ctx) being mapped to new hardware queues (hctx). As a result, the affected hctx remains unused for any IO. Interestingly, this bug exposed the first issue with sbitmap freeing. As usual, review and feedback are most welcome! Nilay Shroff (2): lib/sbitmap: fix kernel crash observed when sbitmap depth is zero null_blk: fix set->driver_data while setting up tagset drivers/block/null_blk/main.c | 3 ++- lib/sbitmap.c | 1 + 2 files changed, 3 insertions(+), 1 deletion(-) -- 2.50.1
