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Date:   Wed, 19 Oct 2022 17:01:56 -0700
From:   "Darrick J. Wong" <djwong@kernel.org>
To:     Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc:     Dave Chinner <david@fromorbit.com>, linux-kernel@vger.kernel.org,
        linux-xfs@vger.kernel.org, nvdimm@lists.linux.dev,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        dan.j.williams@intel.com
Subject: Re: [RFC PATCH] xfs: drop experimental warning for fsdax
Message-ID: <Y1CP9HOs9Mqlh28X@magnolia>
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On Sun, Oct 16, 2022 at 10:05:17PM +0800, Shiyang Ruan wrote:
> 
> 
> 在 2022/10/14 23:50, Darrick J. Wong 写道:
> > On Fri, Oct 14, 2022 at 10:24:29AM +0800, Shiyang Ruan wrote:
> > > 
> > > 
> > > 在 2022/10/14 2:30, Darrick J. Wong 写道:
> > > > On Thu, Sep 29, 2022 at 12:05:14PM -0700, Darrick J. Wong wrote:
> > > > > On Wed, Sep 28, 2022 at 10:46:17PM +0800, Shiyang Ruan wrote:
> > > > > > 
> > > ...
> > > > > > > 
> > > > > > > > FWIW I saw dmesg failures in xfs/517 and xfs/013 starting with 6.0-rc5,
> > > > > > > > and I haven't even turned on reflink yet:
> > > > > > > > 
> > > > > > > > run fstests xfs/517 at 2022-09-26 19:53:34
> > > > > > > > XFS (pmem1): EXPERIMENTAL Large extent counts feature in use. Use at your own risk!
> > > > > > > > XFS (pmem1): Mounting V5 Filesystem
> > > > > > > > XFS (pmem1): Ending clean mount
> > > > > > > > XFS (pmem1): Quotacheck needed: Please wait.
> > > > > > > > XFS (pmem1): Quotacheck: Done.
> > > > > > > > XFS (pmem1): Unmounting Filesystem
> > > > > > > > XFS (pmem0): EXPERIMENTAL online scrub feature in use. Use at your own risk!
> > > > > > > > XFS (pmem1): EXPERIMENTAL Large extent counts feature in use. Use at your own risk!
> > > > > > > > XFS (pmem1): Mounting V5 Filesystem
> > > > > > > > XFS (pmem1): Ending clean mount
> > > > > > > > XFS (pmem1): Quotacheck needed: Please wait.
> > > > > > > > XFS (pmem1): Quotacheck: Done.
> > > > > > > > ------------[ cut here ]------------
> > > > > > > > WARNING: CPU: 1 PID: 415317 at fs/dax.c:380 dax_insert_entry+0x22d/0x320
> > > > 
> > > > Ping?
> > > > 
> > > > This time around I replaced the WARN_ON with this:
> > > > 
> > > > 	if (page->mapping)
> > > > 		printk(KERN_ERR "%s:%d ino 0x%lx index 0x%lx page 0x%llx mapping 0x%llx <- 0x%llx\n", __func__, __LINE__, mapping->host->i_ino, index + i, (unsigned long long)page, (unsigned long long)page->mapping, (unsigned long long)mapping);
> > > > 
> > > > and promptly started seeing scary things like this:
> > > > 
> > > > [   37.576598] dax_associate_entry:381 ino 0x1807870 index 0x370 page 0xffffea00133f1480 mapping 0x1 <- 0xffff888042fbb528
> > > > [   37.577570] dax_associate_entry:381 ino 0x1807870 index 0x371 page 0xffffea00133f1500 mapping 0x1 <- 0xffff888042fbb528
> > > > [   37.698657] dax_associate_entry:381 ino 0x180044a index 0x5f8 page 0xffffea0013244900 mapping 0xffff888042eaf128 <- 0xffff888042dda128
> > > > [   37.699349] dax_associate_entry:381 ino 0x800808 index 0x136 page 0xffffea0013245640 mapping 0xffff888042eaf128 <- 0xffff888042d3ce28
> > > > [   37.699680] dax_associate_entry:381 ino 0x180044a index 0x5f9 page 0xffffea0013245680 mapping 0xffff888042eaf128 <- 0xffff888042dda128
> > > > [   37.700684] dax_associate_entry:381 ino 0x800808 index 0x137 page 0xffffea00132456c0 mapping 0xffff888042eaf128 <- 0xffff888042d3ce28
> > > > [   37.701611] dax_associate_entry:381 ino 0x180044a index 0x5fa page 0xffffea0013245700 mapping 0xffff888042eaf128 <- 0xffff888042dda128
> > > > [   37.764126] dax_associate_entry:381 ino 0x103c52c index 0x28a page 0xffffea001345afc0 mapping 0x1 <- 0xffff888019c14928
> > > > [   37.765078] dax_associate_entry:381 ino 0x103c52c index 0x28b page 0xffffea001345b000 mapping 0x1 <- 0xffff888019c14928
> > > > [   39.193523] dax_associate_entry:381 ino 0x184657f index 0x124 page 0xffffea000e2a4440 mapping 0xffff8880120d7628 <- 0xffff888019ca3528
> > > > [   39.194692] dax_associate_entry:381 ino 0x184657f index 0x125 page 0xffffea000e2a4480 mapping 0xffff8880120d7628 <- 0xffff888019ca3528
> > > > [   39.195716] dax_associate_entry:381 ino 0x184657f index 0x126 page 0xffffea000e2a44c0 mapping 0xffff8880120d7628 <- 0xffff888019ca3528
> > > > [   39.196736] dax_associate_entry:381 ino 0x184657f index 0x127 page 0xffffea000e2a4500 mapping 0xffff8880120d7628 <- 0xffff888019ca3528
> > > > [   39.197906] dax_associate_entry:381 ino 0x184657f index 0x128 page 0xffffea000e2a5040 mapping 0xffff8880120d7628 <- 0xffff888019ca3528
> > > > [   39.198924] dax_associate_entry:381 ino 0x184657f index 0x129 page 0xffffea000e2a5080 mapping 0xffff8880120d7628 <- 0xffff888019ca3528
> > > > [   39.247053] dax_associate_entry:381 ino 0x5dd1e index 0x2d page 0xffffea0015a0e640 mapping 0x1 <- 0xffff88804af88828
> > > > [   39.248006] dax_associate_entry:381 ino 0x5dd1e index 0x2e page 0xffffea0015a0e680 mapping 0x1 <- 0xffff88804af88828
> > > > [   39.490880] dax_associate_entry:381 ino 0x1a9dc index 0x7d page 0xffffea000e7012c0 mapping 0xffff888042fd1728 <- 0xffff88804afaec28
> > > > [   39.492038] dax_associate_entry:381 ino 0x1a9dc index 0x7e page 0xffffea000e701300 mapping 0xffff888042fd1728 <- 0xffff88804afaec28
> > > > [   39.493099] dax_associate_entry:381 ino 0x1a9dc index 0x7f page 0xffffea000e701340 mapping 0xffff888042fd1728 <- 0xffff88804afaec28
> > > > [   40.926247] dax_associate_entry:381 ino 0x182e265 index 0x54c page 0xffffea0015da0840 mapping 0x1 <- 0xffff888019c0dd28
> > > > [   41.675459] dax_associate_entry:381 ino 0x15e5d index 0x29 page 0xffffea000e4350c0 mapping 0x1 <- 0xffff888019c05828
> > > > [   41.676418] dax_associate_entry:381 ino 0x15e5d index 0x2a page 0xffffea000e435100 mapping 0x1 <- 0xffff888019c05828
> > > > [   41.677352] dax_associate_entry:381 ino 0x15e5d index 0x2b page 0xffffea000e435180 mapping 0x1 <- 0xffff888019c05828
> > > > [   41.678372] dax_associate_entry:381 ino 0x15e5d index 0x2c page 0xffffea000e4351c0 mapping 0x1 <- 0xffff888019c05828
> > > > [   41.965026] dax_associate_entry:381 ino 0x185adb4 index 0x87 page 0xffffea000e616d00 mapping 0x1 <- 0xffff88801a83b528
> > > > [   41.966065] dax_associate_entry:381 ino 0x185adb4 index 0x88 page 0xffffea000e616d40 mapping 0x1 <- 0xffff88801a83b528
> > > > [   43.565384] dax_associate_entry:381 ino 0x804d9d index 0x229 page 0xffffea0013653fc0 mapping 0x1 <- 0xffff88804bd97128
> > > > [   43.566399] dax_associate_entry:381 ino 0x804d9d index 0x22a page 0xffffea0013654000 mapping 0x1 <- 0xffff88804bd97128
> > > > [   43.567343] dax_associate_entry:381 ino 0x804d9d index 0x22b page 0xffffea0013654040 mapping 0x1 <- 0xffff88804bd97128
> > > > [   45.512017] dax_associate_entry:381 ino 0x18192bb index 0x1f page 0xffffea00133f1300 mapping 0x1 <- 0xffff88804bcdb528
> > > > [   45.512974] dax_associate_entry:381 ino 0x18192bb index 0x20 page 0xffffea00133f1340 mapping 0x1 <- 0xffff88804bcdb528
> > > > [   45.513942] dax_associate_entry:381 ino 0x18192bb index 0x21 page 0xffffea00133f1380 mapping 0x1 <- 0xffff88804bcdb528
> > > > [   45.514857] dax_associate_entry:381 ino 0x18192bb index 0x22 page 0xffffea00133f13c0 mapping 0x1 <- 0xffff88804bcdb528
> > > > [   45.515760] dax_associate_entry:381 ino 0x18192bb index 0x23 page 0xffffea00133f1400 mapping 0x1 <- 0xffff88804bcdb528
> > > > [   45.516673] dax_associate_entry:381 ino 0x18192bb index 0x24 page 0xffffea00133f1440 mapping 0x1 <- 0xffff88804bcdb528
> > > > 
> > > > I'm not sure what's going on here, but we're clearly turning COW daxpages
> > > > back into single-mapping daxpages.  I'm not sure what's going on for the
> > > > cases where we're replacing one mapping with another.  My dimwitted
> > > > guess is that dax_fault_is_cow() is incorrectly returning false in some
> > > > cases.
> > > > 
> > > > Replacing the contents of that function with:
> > > > 
> > > > 	if (iter->srcmap.type != IOMAP_HOLE)
> > > > 		return true;
> > > > 	if (iter->iomap.flags & IOMAP_F_SHARED)
> > > > 		return true;
> > > > 	return false;
> > > > 
> > > > Doesn't make the errors go away.  Curiously, replacing the entire
> > > > function body with "return true;" fixes /that/ problem though...
> > > 
> > > I am looking into this error by adding debug message too.  I found that
> > > testcases which execute fsstress will randomly occur this error.  I'm
> > > guessing some concurrent operations caused the cow flag (returned by
> > > dax_fault_is_cow()) to be incorrectly judged.  But still haven't catch the
> > > exactly operation yet.
> > 
> > I have an offhand guess that the following sequence might reproduce it:
> > 
> > <write data to a fsdax file1>
> > 
> > <process 1 maps file1, which sets up the pagecache mapping to pmem, and
> > goes to sleep>
> > 
> > cp --reflink=always file1 file2
> > 
> > <process 2 maps file2, which tries to map the same pmem "page" into
> > file2's pagecache and trips over page->mapping already being set to
> > file1's pagecache>
> > 
> > But I dunno, I haven't had much time for digging into this one.
> 
> I tried this sequence on v6.0 but it didn't reproduce the warning.

I tried it on 6.1-rc1 and ... it seems to have gone away.

It occurs to me -- how do you turn on fsdax mode?

I set MKFS_OPTIONS='-d daxinherit=1 -m reflink=1'

> > 
> > > > ...but generic/649 still fails with things like:
> > > > 
> > > > [  571.224285] run fstests generic/649 at 2022-10-13 11:26:59
> > > > [  571.796353] XFS (pmem0): Mounting V5 Filesystem
> > > > [  571.799059] XFS (pmem0): Ending clean mount
> > > > [  572.378624] ------------[ cut here ]------------
> > > > [  572.379598] WARNING: CPU: 1 PID: 48538 at fs/dax.c:930 dax_writeback_mapping_range+0x2f1/0x600
> > > > 
> > > > Which comes from this warning in dax_writeback_one:
> > > > 
> > > > 	/*
> > > > 	 * A page got tagged dirty in DAX mapping? Something is seriously
> > > > 	 * wrong.
> > > > 	 */
> > > > 	if (WARN_ON(!xa_is_value(entry)))
> > > > 		return -EIO;
> > > > 
> > > > Help?
> > > 
> > > Sorry, no time for this yet...
> > > 
> > > BTW, are these errors still occur when reflink is turned off? (dax on,
> > > reflink off)
> > 
> > Hmm I'll try that later today.
> 
> Forgot to tell you that I have tested dax_on&reflink_off with the Kernel
> Config which you sent to me: no failure case caused by the dmesg warning.

But with reflink turned on, it fails with numerous corruption errors.
I've just barely managed to rebase my dev tree on 6.1, so we'll see how
reflink + dax mode go on 6.1 in a day or two.

--D

> 
> 
> --
> Thanks,
> Ruan.
> 
> > 
> > --D
> > 
> > > 
> > > --
> > > Thanks,
> > > Ruan.
> > > 
> > > > 
> > > > --D
> > > > 
> > > > > > > > Modules linked in: xfs nft_chain_nat xt_REDIRECT nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_tcpudp ip_set_hash_ip ip_set_hash_net xt_set nft_compat ip_set_hash_mac ip_set nf_tables libcrc32c bfq nfnetlink pvpanic_mmio pvpanic nd_pmem dax_pmem nd_btt sch_fq_codel fuse configfs ip_tables x_tables overlay nfsv4 af_packet [last unloaded: scsi_d
> > > > > > > > 
> > > > > > > > CPU: 1 PID: 415317 Comm: fsstress Tainted: G        W          6.0.0-rc7-xfsx #rc7 727341edbd0773a36b78b09dab448fa1896eb3a5
> > > > > > > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
> > > > > > > > RIP: 0010:dax_insert_entry+0x22d/0x320
> > > > > > > > Code: e0 48 83 c4 20 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 58 20 48 8d 53 01 e9 62 ff ff ff 48 8b 58 20 48 8d 53 01 e9 4d ff ff ff <0f> 0b e9 6d ff ff ff 31 f6 48 89 ef e8 72 74 12 00 eb a1 83 e0 02
> > > > > > > > RSP: 0000:ffffc90004693b28 EFLAGS: 00010002
> > > > > > > > RAX: ffffea0010a20480 RBX: 0000000000000001 RCX: 0000000000000001
> > > > > > > > RDX: ffffea0000000000 RSI: 0000000000000033 RDI: ffffea0010a204c0
> > > > > > > > RBP: ffffc90004693c08 R08: 0000000000000000 R09: 0000000000000000
> > > > > > > > R10: ffff88800c226228 R11: 0000000000000001 R12: 0000000000000011
> > > > > > > > R13: ffff88800c226228 R14: ffffc90004693e08 R15: 0000000000000000
> > > > > > > > FS:  00007f3aad8db740(0000) GS:ffff88803ed00000(0000) knlGS:0000000000000000
> > > > > > > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > > > > > CR2: 00007f3aad8d1000 CR3: 0000000043104003 CR4: 00000000001706e0
> > > > > > > > Call Trace:
> > > > > > > >     <TASK>
> > > > > > > >     dax_fault_iter+0x26e/0x670
> > > > > > > >     dax_iomap_pte_fault+0x1ab/0x3e0
> > > > > > > >     __xfs_filemap_fault+0x32f/0x5a0 [xfs c617487f99e14abfa5deb24e923415b927df3d4b]
> > > > > > > >     __do_fault+0x30/0x1e0
> > > > > > > >     do_fault+0x316/0x6d0
> > > > > > > >     ? mmap_region+0x2a5/0x620
> > > > > > > >     __handle_mm_fault+0x649/0x1250
> > > > > > > >     handle_mm_fault+0xc1/0x220
> > > > > > > >     do_user_addr_fault+0x1ac/0x610
> > > > > > > >     ? _copy_to_user+0x63/0x80
> > > > > > > >     exc_page_fault+0x63/0x130
> > > > > > > >     asm_exc_page_fault+0x22/0x30
> > > > > > > > RIP: 0033:0x7f3aada7f1ca
> > > > > > > > Code: c5 fe 7f 07 c5 fe 7f 47 20 c5 fe 7f 47 40 c5 fe 7f 47 60 c5 f8 77 c3 66 0f 1f 84 00 00 00 00 00 40 0f b6 c6 48 89 d1 48 89 fa <f3> aa 48 89 d0 c5 f8 77 c3 66 66 2e 0f 1f 84 00 00 00 00 00 66 90
> > > > > > > > RSP: 002b:00007ffe47afa688 EFLAGS: 00010206
> > > > > > > > RAX: 000000000000002e RBX: 0000000000033000 RCX: 000000000000999c
> > > > > > > > RDX: 00007f3aad8d1000 RSI: 000000000000002e RDI: 00007f3aad8d1000
> > > > > > > > RBP: 0000558851e13240 R08: 0000000000000000 R09: 0000000000033000
> > > > > > > > R10: 0000000000000008 R11: 0000000000000246 R12: 028f5c28f5c28f5c
> > > > > > > > R13: 8f5c28f5c28f5c29 R14: 000000000000999c R15: 0000000000001c81
> > > > > > > >     </TASK>
> > > > > > > > ---[ end trace 0000000000000000 ]---
> > > > > > > > XFS (pmem0): Unmounting Filesystem
> > > > > > > > XFS (pmem1): EXPERIMENTAL online scrub feature in use. Use at your own risk!
> > > > > > > > XFS (pmem1): *** REPAIR SUCCESS ino 0x80 type probe agno 0x0 inum 0x0 gen 0x0 flags 0x80000001 error 0
> > > > > > > > XFS (pmem1): Unmounting Filesystem
> > > > > > > > XFS (pmem1): EXPERIMENTAL Large extent counts feature in use. Use at your own risk!
> > > > > > > > XFS (pmem1): Mounting V5 Filesystem
> > > > > > > > XFS (pmem1): Ending clean mount
> > > > > > > > XFS (pmem1): Unmounting Filesystem
> > > > > > > 
> > > > > > > Yup, that's the same as what I'm seeing.
> > > > > > 
> > > > > > Could you send me your kernel config (or other configs needed for the test)?
> > > > > > I still cannot reproduce this warning when reflink is off, even without this
> > > > > > drop patch.  Maybe something different in config file?
> > > > > > 
> > > > > > 
> > > > > > PS: I specifically tried the two cases Darrick mentioned (on v6.0-rc6):
> > > > > > 
> > > > > > [root@f33 xfstests-dev]# mkfs.xfs -m reflink=0,rmapbt=1 /dev/pmem0.1 -f
> > > > > > meta-data=/dev/pmem0.1           isize=512    agcount=4, agsize=257920 blks
> > > > > >            =                       sectsz=4096  attr=2, projid32bit=1
> > > > > >            =                       crc=1        finobt=1, sparse=1, rmapbt=1
> > > > > >            =                       reflink=0    bigtime=1 inobtcount=1
> > > > > > nrext64=0
> > > > > > data     =                       bsize=4096   blocks=1031680, imaxpct=25
> > > > > >            =                       sunit=0      swidth=0 blks
> > > > > > naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
> > > > > > log      =internal log           bsize=4096   blocks=16384, version=2
> > > > > >            =                       sectsz=4096  sunit=1 blks, lazy-count=1
> > > > > > realtime =none                   extsz=4096   blocks=0, rtextents=0
> > > > > > [root@f33 xfstests-dev]# mkfs.xfs -m reflink=0,rmapbt=1 /dev/pmem0 -f
> > > > > > meta-data=/dev/pmem0             isize=512    agcount=4, agsize=257920 blks
> > > > > >            =                       sectsz=4096  attr=2, projid32bit=1
> > > > > >            =                       crc=1        finobt=1, sparse=1, rmapbt=1
> > > > > >            =                       reflink=0    bigtime=1 inobtcount=1
> > > > > > nrext64=0
> > > > > > data     =                       bsize=4096   blocks=1031680, imaxpct=25
> > > > > >            =                       sunit=0      swidth=0 blks
> > > > > > naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
> > > > > > log      =internal log           bsize=4096   blocks=16384, version=2
> > > > > >            =                       sectsz=4096  sunit=1 blks, lazy-count=1
> > > > > > realtime =none                   extsz=4096   blocks=0, rtextents=0
> > > > > > [root@f33 xfstests-dev]# ./check xfs/013 xfs/517
> > > > > > FSTYP         -- xfs (debug)
> > > > > > PLATFORM      -- Linux/x86_64 f33 6.0.0-rc6 #84 SMP PREEMPT_DYNAMIC Wed Sep
> > > > > > 28 18:27:33 CST 2022
> > > > > > MKFS_OPTIONS  -- -f -m reflink=0,rmapbt=1 /dev/pmem0.1
> > > > > > MOUNT_OPTIONS -- -o dax -o context=system_u:object_r:root_t:s0 /dev/pmem0.1
> > > > > > /mnt/scratch
> > > > > > 
> > > > > > xfs/013 127s ...  166s
> > > > > > xfs/517 66s ...  66s
> > > > > > Ran: xfs/013 xfs/517
> > > > > > Passed all 2 tests
> > > > > 
> > > > > I'm not sure what exactly is going weird here -- I tried it on my dev
> > > > > machine just now and it passed, but the similarly configured testcloud
> > > > > failed it last night.
> > > > > 
> > > > > FSTYP         -- xfs (debug)
> > > > > PLATFORM      -- Linux/x86_64 ca-nfsdev6-mtr03 6.0.0-rc7-xfsx #rc7 SMP
> > > > > PREEMPT_DYNAMIC Wed Sep 28 15:35:58 PDT 2022
> > > > > MKFS_OPTIONS  -- -f -m reflink=0, -d daxinherit=1, /dev/pmem1
> > > > > MOUNT_OPTIONS -- -o usrquota,grpquota,prjquota, /dev/pmem1 /opt
> > > > > 
> > > > > Note that I use libvirt to configure pmem in the VMs.  This is an
> > > > > excerpt of the end of domain xml file:
> > > > > 
> > > > >       <memory model='nvdimm' access='shared'>
> > > > >         <source>
> > > > >           <path>/run/mtrdisk/g.mem</path>
> > > > >         </source>
> > > > >         <target>
> > > > >           <size unit='KiB'>21104640</size>
> > > > >           <node>0</node>
> > > > >         </target>
> > > > >         <address type='dimm' slot='0'/>
> > > > >       </memory>
> > > > >       <memory model='nvdimm' access='shared'>
> > > > >         <source>
> > > > >           <path>/run/mtrdisk/h.mem</path>
> > > > >         </source>
> > > > >         <target>
> > > > >           <size unit='KiB'>21104640</size>
> > > > >           <node>1</node>
> > > > >         </target>
> > > > >         <address type='dimm' slot='1'/>
> > > > >       </memory>
> > > > >     </devices>
> > > > > </domain>
> > > > > 
> > > > > --D
> > > > >