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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?kWAi05sFhfO7QtpRupWqTBotrRBkd4vybIOHyJ+9rrpGikvMJoEavcodxnJz?= =?us-ascii?Q?lZGCTg5/AUN6dV0x7BBWlQBQPnYtjGWVWR258tA4tIvRPNPvnvgDQHC0Hid3?= =?us-ascii?Q?tDp9srj6iM93g5Ij21u+oJBtGVsWrUHKu1VnVUG6r0PqloA39jPb7LwVp4qh?= =?us-ascii?Q?01zRDBy+HpI637VXSaq9ySVoEZB6UfTZXzuWb4nes1Nnah9L92wKSUvyRJGd?= =?us-ascii?Q?ynxWP9Z4jO718dza427qIDG6sNNGXjN3bH9icHR4FgGp8tvGEu6U3yGcQ5/K?= =?us-ascii?Q?nGdwDKyJNCnvZrkxVyNaDRljvMGolGudriibUQ6GPBPNBwADZpcXmf+l45Zn?= =?us-ascii?Q?1GiFSBMvwD28ZeQHX6/qSgDnAFc8r1MQdfyU1wfFKlnfy1edMjjkox2vguyC?= =?us-ascii?Q?HHo3hNau5fo7Af3O5BHYwcvhgVM0C/eC63gXmQ6qVtNapehanGI4tS6/YiEd?= =?us-ascii?Q?VHXAwNKjnh13im6F4dy8XouxM3DAyRFlJofZdZJS7Y5GoL7y/1QgvtyaFbhD?= =?us-ascii?Q?TDJAUdwSVeDzSnyIUHgAnySylpw8ZqVyj0QJQfD4pbwj+S1sDshN8UoE6UM9?= =?us-ascii?Q?X1yCH24u7SCZODqoQbvpyaskxozDD0noZ8UIctdiJs3XoGsiJZTEsg9se8o4?= =?us-ascii?Q?9HPNdc+oatvRH5FSj/+cAEN0dPWNdkjYThQf5/F7AFD3DqxBiSqoPDYjZuUQ?= =?us-ascii?Q?jt2ah5kgDA+KoPW5nWpkt/E8SS9b1FwfH+MtyyBxsTRLoZRpNfwgmeGGy5jc?= =?us-ascii?Q?xlIrwuKQWZv6nTcBmdoLtmHbT8uTc4kySfn0aqfZ1RROR/EiLsQB3MZYX6sH?= =?us-ascii?Q?VCQFlk3FX220hUrOF2ER0mvReLeX4wb8YiCKV9kfoj1+IxrEXeNwmq5Qi4+S?= =?us-ascii?Q?fCdmsDcoaQMgmJUht44FOZAht3Ha2AkfGcZEtywBz9C+YwPlEzlVq6qqdmCc?= =?us-ascii?Q?2vFndUDdSDl9M6l+AzmMUkCdNpliVtTrPyMHtcVuYhVVAUlfeFA4tIlV+L0Y?= =?us-ascii?Q?DWUsHMpWVSnXke3C03IgnNcMI60VGR0t3PU10wByV6CdlIzAtapAdz/YblCE?= =?us-ascii?Q?lcjz3+y8wZG/H/wr0DtG9qIv0VVhXAzsXlIM6jn2ea92eWoUggHta46W0j36?= =?us-ascii?Q?pahlGrfZdkZVtuneFHwebG3SXIb1ZXvrSBo4lAWubR8qp89SnqBugT0wJewj?= =?us-ascii?Q?QvpYAVJNz8X/B8REURN4VhuzfXUzJSSkTkn7Uz41Orh1pOuROJaXAlCm+rbD?= =?us-ascii?Q?UprzA8xgYn2IkmnqT2DrdNG41u2+dW4BnOifrx8IeIeVvNGPP6FQyoLGxUVi?= =?us-ascii?Q?bkP7q1SmSmhsEssdnYDSj/dbHzvtUuzgHix9okeb7+maj3zUEyDgFE4ydwGP?= =?us-ascii?Q?9zhSqWmzew+PES/HANiz4VoWc4K1f+fJGE8op1Q8sKZ71qPPRdgMyZkiRoxN?= =?us-ascii?Q?FIW0zcW2mmjokCZnDdmfL0l6SIFLGJDjQw+ru8MUeuaCjpd8UdUejsQ5Fvgb?= =?us-ascii?Q?2r9bqZsxqvfCB343M6KgFozOFRVQWkOuj+EWwOYVQr5Hd0lkr2ABJdc4Y6H+?= =?us-ascii?Q?qnbdtuxGxm8XCHvd9e+piXRfD5WE67kmLcMj6rCNMPFT8G7Ay2Cpl5ql0lFg?= =?us-ascii?Q?xVg9i/Uoj7Qn7LvB7o3dBlLZEAH0naW46PseZRfM18+yyeBZ9rUtfqgEMRhn?= =?us-ascii?Q?wfcgILUY2YE8KNmHjdVi4u/xBUNvy2aDbbpKXakMtaCjNSbOBKAxZwTBPU6Q?= =?us-ascii?Q?N9V87tMZWTlGuw433lcTYvXxRVW9Ohlm/jewZYmKyZ//I4dQRsld?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3974d806-0eed-49a2-02c0-08de811e0362 X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB8800.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Mar 2026 16:31:44.1027 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: id1r2na7q+sNlOu3kI/WYnuCxwm9+4hm3wVjAplEMN/kRsU+REAHsTCZcShB0wEyXreP0kq6m1w/NNyyTddPRQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV2PR12MB5896 On Thu, Mar 12, 2026 at 08:54:29PM -0300, Enzo Matsumiya wrote: > Hi Yury, > > On 03/12, Yury Norov wrote: > > Based on 'sizeof(x) == 4' condition, in 32-bit case the function is wired > > to ffs(), while in 64-bit case to __ffs(). The difference is substantial: > > ffs(x) == __ffs(x) + 1. Also, ffs(0) == 0, while __ffs(0) is undefined. > > > > The 32-bit behaviour is inconsistent with the function description, so it > > needs to get fixed. > > > > There are 9 individual users for the function in 6 different subsystems. > > Some arches and drivers are 64-bit only: > > - arch/loongarch/kvm/intc/eiointc.c; > > - drivers/hv/mshv_vtl_main.c; > > - kernel/liveupdate/kexec_handover.c; > > > > The others are: > > - ib_umem_find_best_pgsz(): as per comment, __ffs() should be correct; > > - rzv2m_csi_reg_write_bit(): ARCH_RENESAS only, unclear; > > - lz77_match_len(): CIFS_COMPRESSION only, unclear, experimental; > > > > None of them explicitly tweak their code for a word length, or x == 0. > > Context for lz77_match_len() case: > > const u64 diff = lz77_read64(cur) ^ lz77_read64(wnd); > > if (!diff) { > ... > } > > cur += count_trailing_zeros(diff) >> 3; > > So x == 0 is checked, however it does assume that > sizeof(unsigned long) == sizeof(u64). I'll have to fix it for when > that's not the case (even with your patch in, as __ffs() casts x to > unsigned long down the line). Thanks for the heads up. Yes, in your case you need __ffs64() (which doesn't exist). Or simply leverage bitmaps API: DECLARE_BITMAP(bitmap, 64); ... bitmap_from_u64(bitmap, diff); cur += find_first_bit(bitmap, 64) >> 3; > > Cheers, > > Enzo So, if you're not objecting to wire 32-bit count_trailing_zeros() to __ffs(), can you please send your ack? Thanks, Yury