On Jan 19, 2011, at 7:53 AM, Wengang Wang wrote:
> I got the crash when test with fio + (ctrl-C). The panic info is like this:
>
> ------------[ cut here ]------------
> kernel BUG at fs/aio.c:558!
> invalid opcode: 0000 [#1] SMP
> last sysfs file: /sys/devices/system/cpu/cpu0/cache/index0/coherency_line_size
> CPU 0
> Modules linked in: netconsole(U) configfs(U) hidp(U) l2cap(U) bluetooth(U) rfkill(U) ipv6(U) nfs(U) lockd(U) fscache(U) nfs_acl(U) auth_rpcgss(U) sunrpc(U) cpufreq_ondemand(U) acpi_cpufreq(U) freq_table(U) dm_multipath(U) sbs(U) sbshc(U) lp(U) snd_hda_codec_analog(U) snd_hda_intel(U) snd_hda_codec(U) snd_hwdep(U) snd_seq_dummy(U) snd_seq_oss(U) i915(U) snd_seq_midi_event(U) snd_seq(U) snd_seq_device(U) snd_pcm_oss(U) drm_kms_helper(U) snd_mixer_oss(U) drm(U) tg3(U) snd_pcm(U) snd_timer(U) snd(U) parport_pc(U) i2c_algo_bit(U) i2c_i801(U) serio_raw(U) parport(U) iTCO_wdt(U) shpchp(U) soundcore(U) video(U) i2c_core(U) dcdbas(U) iTCO_vendor_support(U) snd_page_alloc(U) pcspkr(U) output(U) pata_acpi(U) ata_piix(U) ata_generic(U) uhci_hcd(U) ohci_hcd(U) ehci_hcd(U) [last unloaded: netconsole]
> Pid: 3112, comm: fio Tainted: G W 2.6.32.21 #3 OptiPlex 745
> RIP: 0010:[<ffffffff8114eb30>] [<ffffffff8114eb30>] __aio_put_req+0x6e/0x150
> RSP: 0018:ffff88006cd7be38 EFLAGS: 00010092
> RAX: 0000000000000038 RBX: ffff880078f2b9c0 RCX: 0000000000007da3
> RDX: 0000000000000000 RSI: 0000000000000082 RDI: 0000000000000046
> RBP: ffff88006cd7be58 R08: 0000000000000001 R09: 0000000000000020
> R10: ffff88006cd7bdb8 R11: 0000000000000001 R12: ffff880078f2b9c0
> R13: ffff880037ef3e40 R14: ffff880037ef3e40 R15: 0000000000000000
> FS: 0000000042eb4940(0063) GS:ffff880001c00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fa172484000 CR3: 000000006ce48000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process fio (pid: 3112, threadinfo ffff88006cd7a000, task ffff88007a7de040)
> Stack:
> ffff880037ef3e40 ffff880037ef3e40 ffff880078f2b9c0 ffff88006cd7bf40
> <0> ffff88006cd7be88 ffffffff8114ec3d ffff88006bc11ed0 ffff880078f2b9c0
> <0> ffff88006bc11ed0 ffff880078f2b9c0 ffff88006cd7bf78 ffffffff81150a15
> Call Trace:
> [<ffffffff8114ec3d>] aio_put_req+0x2b/0x43
> [<ffffffff81150a15>] sys_io_submit+0x56a/0x6f1
> [<ffffffff81011db2>] system_call_fastpath+0x16/0x1b
> Code: 7f 45 81 e8 a9 8d f0 ff e8 32 6d ec ff 83 7b 18 00 7d 1c 48 89 da 48 c7 c6 58 7f 45 81 48 c7 c7 d4 b1 5d 81 31 c0 e8 86 8d f0 ff <0f> 0b eb fe 74 07 31 c0 e9 cd 00 00 00 4c 8d a3 d8 00 00 00 48
> RIP [<ffffffff8114eb30>] __aio_put_req+0x6e/0x150
> RSP <ffff88006cd7be38>
> ---[ end trace 52431c8b3d9e71ba ]---
> Kernel panic - not syncing: Fatal exception
>
> The number 558 should be 552 in original codes. It is the
> BUG_ON(req->ki_users < 0);
> in __aio_put_req().
>
> My analysis is(correct me):
> In the sys_io_submit path, the vfs doesn't hope the FS under ground drop the
> ki_users in "error" case. The error is -ERESTARTSYS, in my test, instead of
> -EIOCBQUEUED. But seems the nfs drops ki_users in error case as well as
> in successful cases too.
>
> So my first attempt is coming for discussion.
> Basically, it makes nfs don't drop(actually it gets then puts) ki_users in error
> cases.
> Let the nfs_direct_req.error records the error from get_user_pages() and
> rpc_run_task() in nfs_direct_read/write path, assuming both the two function
> returns all error they hit.
Yes, get_user_pages() is invoked in both the read and write path, and returns -ERESTARTSYS when a signal is pending. It can return other errors as well, but -ERESTARTSYS seems to be by far the common case.
> And in nfs_direct_complete(), if error occured(per
> nfs_direct_req.error), take another ref on kiocb->ki_users. (and then drop it in
> aio_complete in existing codes).
Reporting error codes via dreq.error is probably a good change for async I/O.
The open-coded equivalent of "aio get iocb" is probably not what we want, however. By my reading of this logic, nfs_direct_write_schedule_iovec() returns a non-zero value in this case, so nfs_direct_complete() is skipped altogether. I think your new code would never be executed.
Currently I agree with Nick: nfs_file_direct_{read,write}() are returning the wrong error codes for asynchronous I/O. Thus the generic aio logic will try to complete a second time NFS I/O that has already failed.
> Signed-off-by: Wengang Wang <wen.gang.wang@xxxxxxxxxx>
> ---
> fs/nfs/direct.c | 21 +++++++++++++++++++--
> 1 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
> index e6ace0d..fa5e5f9 100644
> --- a/fs/nfs/direct.c
> +++ b/fs/nfs/direct.c
> @@ -219,6 +219,17 @@ static void nfs_direct_complete(struct nfs_direct_req *dreq)
> long res = (long) dreq->error;
> if (!res)
> res = (long) dreq->count;
> + /*
> + * vfs doesn't want us drop kiocb->ki_users in error case.
> + * we get an extra ref on it then later drop it in aio_complete
> + */
> + if (dreq->error) {
> + struct kioctx *ctx = dreq->iocb->ki_ctx;
> +
> + spin_lock_irq(&ctx->ctx_lock);
> + dreq->iocb->ki_users ++;
> + spin_unlock_irq(&ctx->ctx_lock);
> + }
> aio_complete(dreq->iocb, res, 0);
> }
> complete_all(&dreq->completion);
> @@ -319,6 +330,7 @@ static ssize_t nfs_direct_read_schedule_segment(struct nfs_direct_req *dreq,
> data->npages, 1, 0, data->pagevec, NULL);
> up_read(¤t->mm->mmap_sem);
> if (result < 0) {
> + dreq->error = result;
> nfs_readdata_free(data);
> break;
> }
> @@ -357,8 +369,10 @@ static ssize_t nfs_direct_read_schedule_segment(struct nfs_direct_req *dreq,
> NFS_PROTO(inode)->read_setup(data, &msg);
>
> task = rpc_run_task(&task_setup_data);
> - if (IS_ERR(task))
> + if (IS_ERR(task)) {
> + dreq->error = PTR_ERR(task);
> break;
> + }
> rpc_put_task(task);
>
> dprintk("NFS: %5u initiated direct read call "
> @@ -748,6 +762,7 @@ static ssize_t nfs_direct_write_schedule_segment(struct nfs_direct_req *dreq,
> data->npages, 0, 0, data->pagevec, NULL);
> up_read(¤t->mm->mmap_sem);
> if (result < 0) {
> + dreq->error = result;
> nfs_writedata_free(data);
> break;
> }
> @@ -789,8 +804,10 @@ static ssize_t nfs_direct_write_schedule_segment(struct nfs_direct_req *dreq,
> NFS_PROTO(inode)->write_setup(data, &msg);
>
> task = rpc_run_task(&task_setup_data);
> - if (IS_ERR(task))
> + if (IS_ERR(task)) {
> + dreq->error = PTR_ERR(task);
> break;
> + }
> rpc_put_task(task);
>
> dprintk("NFS: %5u initiated direct write call "
> --
> 1.7.2.3
>
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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