On Mon, Jun 10, 2024 at 12:57:02PM +0300, Sagi Grimberg wrote: > On 10/06/2024 10:51, Venkat Rao Bagalkote wrote: > > > > [ 140.209777] BUG: Unable to handle kernel data access at 0x18d7003065646fee > > [ 140.209792] Faulting instruction address: 0xc00000000023b45c > > [ 140.209798] Oops: Kernel access of bad area, sig: 11 [#1] > > [ 140.209802] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=8192 NUMA pSeries > > [ 140.209864] CPU: 2 PID: 129 Comm: kworker/u65:3 Kdump: loaded Not tainted 6.10.0-rc3 #2 > > [ 140.209870] Hardware name: IBM,9009-42A POWER9 (raw) 0x4e0202 0xf000005 of:IBM,FW950.A0 (VL950_141) hv:phyp pSeries > > [ 140.209876] Workqueue: nvme-wq nvme_scan_work [nvme_core] > > [ 140.209889] NIP: c00000000023b45c LR: c008000006a96b20 CTR: c00000000023b42c > > [ 140.209894] REGS: c0000000506078a0 TRAP: 0380 Not tainted (6.10.0-rc3) > > [ 140.209899] MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 24000244 XER: 00000000 > > [ 140.209975] NIP [c00000000023b45c] synchronize_srcu+0x30/0x1c0 > > [ 140.209984] LR [c008000006a96b20] nvme_ns_remove+0x80/0x2d8 [nvme_core] > > [ 140.209994] Call Trace: > > [ 140.209997] [c000000050607b90] [c008000006a96b20] nvme_ns_remove+0x80/0x2d8 [nvme_core] > > [ 140.210008] [c000000050607bd0] [c008000006a972b4] nvme_remove_invalid_namespaces+0x144/0x1ac [nvme_core] > > [ 140.210020] [c000000050607c60] [c008000006a9dbd4] nvme_scan_ns_list+0x19c/0x370 [nvme_core] > > [ 140.210032] [c000000050607d70] [c008000006a9dfc8] nvme_scan_work+0xc8/0x278 [nvme_core] > > [ 140.210043] [c000000050607e40] [c00000000019414c] process_one_work+0x20c/0x4f4 > > [ 140.210051] [c000000050607ef0] [c0000000001950cc] worker_thread+0x378/0x544 > > [ 140.210058] [c000000050607f90] [c0000000001a164c] kthread+0x138/0x140 > > [ 140.210065] [c000000050607fe0] [c00000000000df98] start_kernel_thread+0x14/0x18 > > [ 140.210072] Code: 3c4c0134 384282d4 7c0802a6 60000000 7c0802a6 fbc1fff0 fba1ffe8 fbe1fff8 7c7e1b78 f8010010 f821ffb1 e9230010 e9290080> 7c2004ac 71290003 41820008 > > [ 140.210093] ---[ end trace 0000000000000000 ]--- > > > > Issue is introduced by the patch: > > be647e2c76b27f409cdd520f66c95be888b553a3. > > Exactly this was the concern when introducing a behavior change in a > sensitive area of the code > to silence lockdep... No risk, no reward. :) If we really can't figure this out, we can always revert and revisit for the next merge. > I'm assuming that the bad dereference is: > synchronize_srcu(&ns->ctrl->srcu); That would have to be it based on the report. Not sure what the problem could be, though, the ns->ctrl must have been valid or we would have failed earlier, and the srcu struct can't be released while the controller is still in use by any namespace. Anyway, I tested this path quite a bit, but I'll revisit with dynamic attachments instead and see if that helps. > btw, looking at the code again, I'm assuming that synchronizing srcu in > every ns remove > slows down batch removal of many namespaces greatly... I may need to test this out, but I thought srcu sync was pretty quick if there were no active readers, which there shouldn't be here outside unusual cases.
