On Mon, Jan 8, 2018 at 1:56 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > On Sun, 2018-01-07 at 13:44 +0100, Krzysztof Kozlowski wrote: >> On Fri, Dec 22, 2017 at 1:05 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: >> > From: Jeff Layton <jlayton@xxxxxxxxxx> >> > >> > Since i_version is mostly treated as an opaque value, we can exploit that >> > fact to avoid incrementing it when no one is watching. With that change, >> > we can avoid incrementing the counter on writes, unless someone has >> > queried for it since it was last incremented. If the a/c/mtime don't >> > change, and the i_version hasn't changed, then there's no need to dirty >> > the inode metadata on a write. >> > >> > Convert the i_version counter to an atomic64_t, and use the lowest order >> > bit to hold a flag that will tell whether anyone has queried the value >> > since it was last incremented. >> > >> > When we go to maybe increment it, we fetch the value and check the flag >> > bit. If it's clear then we don't need to do anything if the update >> > isn't being forced. >> > >> > If we do need to update, then we increment the counter by 2, and clear >> > the flag bit, and then use a CAS op to swap it into place. If that >> > works, we return true. If it doesn't then do it again with the value >> > that we fetch from the CAS operation. >> > >> > On the query side, if the flag is already set, then we just shift the >> > value down by 1 bit and return it. Otherwise, we set the flag in our >> > on-stack value and again use cmpxchg to swap it into place if it hasn't >> > changed. If it has, then we use the value from the cmpxchg as the new >> > "old" value and try again. >> > >> > This method allows us to avoid incrementing the counter on writes (and >> > dirtying the metadata) under typical workloads. We only need to increment >> > if it has been queried since it was last changed. >> > >> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> >> > --- >> > include/linux/fs.h | 2 +- >> > include/linux/iversion.h | 208 ++++++++++++++++++++++++++++++++++------------- >> > 2 files changed, 154 insertions(+), 56 deletions(-) >> > >> >> Hi, >> >> On recent linux-next my ARM/Exynos boards fail to boot over nfsroot. >> This commit popped up through bisect (log at the end). Systemd >> timeouts on some device-specific services, including mounting ext4 >> /home: >> >> [ *** ] (1 of 4) A start job is running for…ress polling (1min 41s / no limit) >> [ TIME ] Timed out waiting for device dev-ttySAC2.device. >> Jan 07 13:29:38 [DEPEND] Dependency failed for Serial Getty on ttySAC2. >> Jan 07 13:29:38 [ TIME ] Timed out waiting for device >> dev-disk-by\x2dlabel-home.device. >> Jan 07 13:29:38 [DEPEND] Dependency failed for /home. >> Jan 07 13:29:38 [DEPEND] Dependency failed for Local File Systems. >> Jan 07 13:29:38 [DEPEND] Dependency failed for File System Check on >> /dev/disk/by-label/home. >> Jan 07 13:30:02 [ *** ] (1 of 2) A start job is running for…ress >> polling (1min 53s / no limit) >> >> Kernel command line: >> console=tty1 console=ttySAC2,115200n8 >> ip=192.168.1.11:192.168.1.10:192.168.1.1:255.255.255.0::eth0:none >> nfsrootdebug root=/dev/nfs >> nfsroot=192.168.1.10:/srv/nfs/odroidxu3,vers=4,nolock rootwait rw >> smsc95xx.macaddr=00:1e:06:61:7a:93 no_console_suspend >> >> /home is /dev/mmcblk1p2: >> kozik@odroidxu3:~$ tune2fs -l /dev/mmcblk1p2 >> tune2fs 1.43.7 (16-Oct-2017) >> Filesystem volume name: home >> Last mounted on: /home >> Filesystem UUID: 3f9dbeba-2738-45d3-807e-c1b2e21128ed >> Filesystem magic number: 0xEF53 >> Filesystem revision #: 1 (dynamic) >> Filesystem features: has_journal ext_attr resize_inode dir_index >> filetype needs_recovery extent flex_bg sparse_super large_file >> uninit_bg dir_nlink extra_isize >> Filesystem flags: signed_directory_hash >> Default mount options: user_xattr acl >> Filesystem state: clean >> Errors behavior: Continue >> Filesystem OS type: Linux >> Inode count: 1430800 >> Block count: 5717760 >> Reserved block count: 285888 >> Free blocks: 5467576 >> Free inodes: 1428301 >> First block: 0 >> Block size: 4096 >> Fragment size: 4096 >> Reserved GDT blocks: 1022 >> Blocks per group: 32768 >> Fragments per group: 32768 >> Inodes per group: 8176 >> Inode blocks per group: 511 >> Flex block group size: 16 >> Filesystem created: Thu May 21 12:17:05 2015 >> Last mount time: Thu Dec 21 13:31:26 2017 >> Last write time: Thu Dec 21 13:31:26 2017 >> Mount count: 1 >> Maximum mount count: -1 >> Last checked: Thu Dec 21 13:31:25 2017 >> Check interval: 0 (<none>) >> Lifetime writes: 126 GB >> Reserved blocks uid: 0 (user root) >> Reserved blocks gid: 0 (group root) >> First inode: 11 >> Inode size: 256 >> Required extra isize: 28 >> Desired extra isize: 28 >> Journal inode: 8 >> Default directory hash: half_md4 >> Directory Hash Seed: 42e17e23-86b2-4356-ad63-78aa51651d03 >> Journal backup: inode blocks >> >> >> Full dmesg log: >> http://www.krzk.eu/#/builders/1/builds/1258/steps/10/logs/serial0 >> >> The regular boot from rootfs on SD card also fails - but without any >> serial console logs (just "Starting kernel...") so the real cause is >> unknown. >> >> Any hints? >> >> Best regards, >> Krzysztof >> >> >> bisect log: >> # bad: [73005e1a35fd67c644b0645c9e4c1efabd0fe62c] Add linux-next >> specific files for 20180103 >> # good: [30a7acd573899fd8b8ac39236eff6468b195ac7d] Linux 4.15-rc6 >> git bisect start 'next/master' 'next/stable' >> # bad: [c1d290f9ce8daa2b0a79d2fe48c1b7c3c5370f5a] Merge >> remote-tracking branch 'crypto/master' >> git bisect bad c1d290f9ce8daa2b0a79d2fe48c1b7c3c5370f5a >> # bad: [55695d94f0915121d106cd2d1ab94983a32f3e9a] Merge >> remote-tracking branch 'hid/for-next' >> git bisect bad 55695d94f0915121d106cd2d1ab94983a32f3e9a >> # good: [cffae1eead0dd91be1a3069a8348127bb00158f3] Merge >> remote-tracking branch 'realtek/for-next' >> git bisect good cffae1eead0dd91be1a3069a8348127bb00158f3 >> # good: [5f889f1176dc99636c6bf8af7c286decc888c007] Merge >> remote-tracking branch 'btrfs/next' >> git bisect good 5f889f1176dc99636c6bf8af7c286decc888c007 >> # good: [984c35877f36bee305e43a1c58176169854d85cf] Merge >> remote-tracking branch 'xfs/for-next' >> git bisect good 984c35877f36bee305e43a1c58176169854d85cf >> # bad: [f9fec502daea2a869232b6dff33ba3de79dd0d61] Merge >> remote-tracking branch 'printk/for-next' >> git bisect bad f9fec502daea2a869232b6dff33ba3de79dd0d61 >> # good: [c71d227fc4133f949dae620ed5e3a250b43f2415] make kernel-side >> POLL... arch-independent >> git bisect good c71d227fc4133f949dae620ed5e3a250b43f2415 >> # good: [416d20e8c31107f5dfd45d1d80d1e6c8e4871180] Merge branches >> 'work.get_user_pages_fast', 'work.wmci', 'work.sock_recvmsg', >> 'misc.netdrv', 'misc.poll', 'work.mqueue', 'work.whack-a-mole' and >> 'work.misc' into for-next >> git bisect good 416d20e8c31107f5dfd45d1d80d1e6c8e4871180 >> # good: [325a1de4a691512a48c1426b943a7b0b9f8d6744] xfs: convert to new >> i_version API >> git bisect good 325a1de4a691512a48c1426b943a7b0b9f8d6744 >> # good: [a94fe10fb114c169e7ddaecd8251521886409121] checkpatch: add >> pF/pf deprecation warning >> git bisect good a94fe10fb114c169e7ddaecd8251521886409121 >> # good: [6b3911dffd1184fdcd63299a5fee59ac000f2067] btrfs: only dirty >> the inode in btrfs_update_time if something was changed >> git bisect good 6b3911dffd1184fdcd63299a5fee59ac000f2067 >> # bad: [448f8c749a7a0ae03505823910ec45a112678048] Merge >> remote-tracking branch 'iversion/iversion-next' >> git bisect bad 448f8c749a7a0ae03505823910ec45a112678048 >> # bad: [8618bff776758ebff5b55211e7b5a60a0fc119a5] fs: handle >> inode->i_version more efficiently >> git bisect bad 8618bff776758ebff5b55211e7b5a60a0fc119a5 >> # first bad commit: [8618bff776758ebff5b55211e7b5a60a0fc119a5] fs: >> handle inode->i_version more efficiently > > That's really strange. I'm afraid I have no idea what could be going on. > > With NFS, we really just treat i_version as an opaque value, so I'm not > sure how this patch in particular would affect anything there. We _do_ > increment it if you have a write delegation in some cases, but not many > servers hand those out. About the NFS server, Arch Linux on Raspberry Pi (so 32-bit, ARMv6): Linux pi 4.9.70-1-ARCH #1 SMP Mon Dec 18 19:38:00 UTC 2017 armv6l GNU/Linux The /etc/nfs.conf is default except: [nfsd] vers2=n vers3=n The client logs for nfsroot mounts are: Jan 08 14:07:25 :: running hook [net_nfs4] Jan 08 14:07:25 IP-Config: eth0 hardware address ba:17:70:7e:87:d1 mtu 1500 Jan 08 14:07:25 IP-Config: eth0 guessed broadcast address 192.168.1.255 Jan 08 14:07:25 IP-Config: eth0 complete (from 192.168.1.10): Jan 08 14:07:25 address: 192.168.1.11 broadcast: 192.168.1.255 netmask: 255.255.255.0 Jan 08 14:07:25 gateway: 192.168.1.1 dns0 : 0.0.0.0 dns1 : 0.0.0.0 Jan 08 14:07:25 rootserver: 192.168.1.10 rootpath: Jan 08 14:07:25 filename : Jan 08 14:07:25 NFS-Mount: 192.168.1.10:/srv/nfs/odroidxu3 Jan 08 14:07:25 Waiting 10 seconds for device /dev/nfs ... Jan 08 14:07:36 ERROR: device '/dev/nfs' not found. Skipping fsck. Jan 08 14:07:36 Mount cmd: Jan 08 14:07:36 /opt/tools/buildbot/arch-arm-bin/mount.nfs4 -o vers=4,nolock 192.168.1.10:/srv/nfs/odroidxu3 /new_root Only root (/) is froom NFS. The /home comes from sdcard (/dev/mmcblk1). > ext4 will only touch the i_version field if you mount it with '-o > iversion'. Are you doing that here? The /home is mounted by systemd from /etc/fstab: LABEL=home /home ext4 defaults 0 2 > > Have you run the bisect more than once? Is this maybe an intermittent > problem, and the bisect has landed on the wrong commit? I just run tests on commits around again (but not full bisect) on current next (next-20180108): fbf97ece47d66d22 - works 3da7bcdd695bae43 ("fs: handle inode->i_version more efficiently") - fails: http://www.krzk.eu/#/builders/1/builds/1267 Best regards, Krzysztof
