On Fri, Jul 14, 2017 at 08:22:31AM -0600, Jens Axboe wrote: > On 07/14/2017 07:47 AM, Ming Lei wrote: > >> @@ -156,6 +156,9 @@ static inline void *bio_data(struct bio *bio) > >> /* > >> * drivers should _never_ use the all version - the bio may have been split > >> * before it got to the driver and the driver won't own all of it > >> + * > >> + * Note that cloned bios must not use this as their bi_vcnt may be invalid and > >> + * this could lead to silent corruptions. > >> */ > >> #define bio_for_each_segment_all(bvl, bio, i) \ > >> for (i = 0, bvl = (bio)->bi_io_vec; i < (bio)->bi_vcnt; i++, bvl++) > >> -- > >> 2.13.0 > >> > > > > Maybe we can add a warning here if it is a cloned bio. > > I think that's a good idea, it's easy for people to get this wrong, and > the consequences can be dire. How about something like this? > > diff --git a/include/linux/bio.h b/include/linux/bio.h > index 7b1cf4ba0902..13b6ac6eae29 100644 > --- a/include/linux/bio.h > +++ b/include/linux/bio.h > @@ -155,9 +155,12 @@ static inline void *bio_data(struct bio *bio) > > /* > * drivers should _never_ use the all version - the bio may have been split > - * before it got to the driver and the driver won't own all of it > + * before it got to the driver and the driver won't own all of it. > + * > + * Don't use this on cloned bio's. > */ > #define bio_for_each_segment_all(bvl, bio, i) \ > + WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)); \ > for (i = 0, bvl = (bio)->bi_io_vec; i < (bio)->bi_vcnt; i++, bvl++) > > static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter, > This patch gave me a crash, I'm double checking it.. thanks, -liubo [ 104.140220] BUG: unable to handle kernel paging request at ffffffffa0399c1a [ 104.140675] IP: report_bug+0xc4/0x180 [ 104.140916] PGD 2626067 [ 104.140917] P4D 2626067 [ 104.141089] PUD 2627063 [ 104.141259] PMD 2346aa067 [ 104.141429] PTE 800000023569c161 [ 104.141610] [ 104.141926] Oops: 0003 [#1] SMP [ 104.142137] Dumping ftrace buffer: [ 104.142366] (ftrace buffer empty) [ 104.142602] Modules linked in: btrfs(OE) xor raid6_pq ppdev parport_pc parport serio_raw nfsd auth_rpcgss nfs_acl lockd grace sunrpc [last unloaded$ xor] [ 104.143493] CPU: 0 PID: 144 Comm: kworker/u16:4 Tainted: G W OE 4.12.0+ #801 [ 104.144009] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014 [ 104.144654] Workqueue: btrfs-rmw btrfs_rmw_helper [btrfs] [ 104.145009] task: ffff8802382f8000 task.stack: ffffc90000f80000 [ 104.145393] RIP: 0010:report_bug+0xc4/0x180 [ 104.145668] RSP: 0018:ffffc90000f83ac8 EFLAGS: 00010002 [ 104.146015] RAX: 0000000000000001 RBX: ffffffffa0356cff RCX: 0000000000000001 [ 104.146474] RDX: ffffffffa0399c10 RSI: 0000000000000480 RDI: 0000000000000000 [ 104.146931] RBP: ffffc90000f83ae8 R08: 0000000000000907 R09: 0000000000000000 [ 104.147393] R10: 000000005170b2af R11: 000000002b881219 R12: ffffc90000f83c38 [ 104.147852] R13: ffffffffa038a415 R14: 0000000000000004 R15: 0000000000000006 [ 104.148315] FS: 0000000000000000(0000) GS:ffff88023a600000(0000) knlGS:0000000000000000 [ 104.148836] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 104.149211] CR2: ffffffffa0399c1a CR3: 00000002244fc000 CR4: 00000000000006f0 [ 104.149672] Call Trace: [ 104.149840] fixup_bug+0x43/0x60 [ 104.150060] do_trap+0x18a/0x1f0 [ 104.150276] do_error_trap+0xdf/0x1a0 [ 104.150606] ? index_rbio_pages+0x14f/0x160 [btrfs] [ 104.150929] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 104.151241] do_invalid_op+0x20/0x30 [ 104.151478] invalid_op+0x1e/0x30 [ 104.151787] RIP: 0010:index_rbio_pages+0x14f/0x160 [btrfs] [ 104.152148] RSP: 0018:ffffc90000f83ce8 EFLAGS: 00010002 [ 104.152488] RAX: ffffffffa0421938 RBX: 0000000000000000 RCX: 0000000000000000 [ 104.152947] RDX: 0000000000000003 RSI: 0000000000000001 RDI: ffffffffa0440420 [ 104.153410] RBP: ffffc90000f83d18 R08: 0000000000000000 R09: 0000000000000000 [ 104.153869] R10: 0000000000000001 R11: 000000002b881219 R12: ffffffffa0421960 [ 104.154330] R13: 0000000000000001 R14: ffff880236e00000 R15: ffff880227718080 [ 104.154882] ? index_rbio_pages+0xc6/0x160 [btrfs] [ 104.155286] rmw_work+0x76/0x310 [btrfs] [ 104.155633] btrfs_scrubparity_helper+0xad/0x8e0 [btrfs] [ 104.156070] btrfs_rmw_helper+0xe/0x10 [btrfs] [ 104.156364] process_one_work+0x34f/0x9c0 [ 104.156631] worker_thread+0x34a/0x6b0 [ 104.156879] kthread+0x180/0x190 [ 104.157095] ? create_worker+0x230/0x230 [ 104.157352] ? kthread_create_on_node+0x70/0x70 [ 104.157648] ? kthread_create_on_node+0x70/0x70 [ 104.157944] ret_from_fork+0x2a/0x40 [ 104.158183] Code: 44 89 c7 31 c0 66 83 e7 04 0f 95 c0 48 83 c0 02 48 83 04 c5 18 e6 dc 82 01 66 85 ff b8 01 00 00 00 0f 85 72 ff ff ff 41 83 c8 04 < 66> 44 89 42 0a 48 89 c8 83 e0 01 48 83 c0 02 48 83 04 c5 f0 e5 [ 104.159436] RIP: report_bug+0xc4/0x180 RSP: ffffc90000f83ac8 [ 104.159803] CR2: ffffffffa0399c1a [ 104.160026] ---[ end trace 78686c1f7150bacf ]---
