On Mon, Jan 08, 2018 at 08:29:24AM -0500, Jeff Layton wrote: > On Mon, 2018-01-08 at 14:21 +0100, Krzysztof Kozlowski wrote: > > 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 > > Ok, thanks. If you're seeing hangs then that might imply that we have > some sort of excessive looping going on in the cmpxchg loops. > > Could you apply the patch below and let me know if it causes either of > the warnings to pop? That might at least point us in the right > direction: No new warnings with attached patch (except existing already lockdep: "INFO: trying to register non-static key."). Systemd timeouts on mounting /home but after entering rescue shell there is no problem running mount /home: Give root password for maintenance (or press Control-D to continue): root@odroidxu3:~# mount /home [ 220.659331] EXT4-fs (mmcblk1p2): mounted filesystem with ordered data mode. Opts: (null) Best regards, Krzysztof
