Attachment 185878 Details for Bug 221909 – sys/cddl: Add a sysctl to toggle send_corrupt_data

[patch] sys/cddl: Add a sysctl to toggle send_corrupt_data

sys-cddl-Add-a-sysctl-to-toggle-zfs_send_corrupt_data.diff (text/plain), 4.68 KB, created by Fabian Keil on 2017-08-29 13:09:42 UTC

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Creator: Fabian Keil

Created: 2017-08-29 13:09:42 UTC

Size: 4.68 KB

patch

obsolete

>From cbf4e628633d6a760a0744606f2bf58ccd54668f Mon Sep 17 00:00:00 2001
>From: Fabian Keil <fk@fabiankeil.de>
>Date: Sun, 4 Jun 2017 13:22:42 +0200
>Subject: [PATCH] sys/cddl: Add a sysctl to toggle send_corrupt_data
>
>Enabling it allows to send datasets with corrupted blocks
>which is useful to recover data from pools with dying disks.
>
>Blocks filled with 0x'zfs badd bloc' are sent instead of
>the corrupted data. As a result, the receiving side may
>end up with more corrupt data than the sending side.
>
>While it would be preferable to send the corrupt data as is
>(assuming the block can be read but contains flipped bits),
>this would probably have to happen at a different layer and
>currently isn't done.
>
>The ZFSOnLinux people already added an option for this in 2013:
>https://github.com/zfsonlinux/zfs/issues/1982
>
>Usage example:
>
>fk@t520 ~ $sudo zpool status -v wde2
>  pool: wde2
> state: ONLINE
>status: One or more devices has experienced an error resulting in data
>	corruption.  Applications may be affected.
>action: Restore the file in question if possible.  Otherwise restore the
>	entire pool from backup.
>   see: https://illumos.org/msg/ZFS-8000-8A
>  scan: scrub repaired 0 in 11h40m with 10 errors on Sun Jan  1 10:25:26 2017
>config:
>
>	NAME              STATE     READ WRITE CKSUM
>	wde2              ONLINE       0     0     0
>	  label/wde2.eli  ONLINE       0     0     0
>
>errors: Permanent errors have been detected in the following files:
>
>        wde2/backup/t520/tank/home/fk@2011-07-28_04:54:/Mail/Tor/Read/15654
>        wde2/backup/t520/tank/home/fk@2011-07-28_04:54:/Mail/Tor/Read/16411
>        [...]
>fk@t520 ~ $cat /wde2/backup/t520/tank/home/fk/.zfs/snapshot/2011-07-28_04\:54/Mail/Tor/Read/16411
>cat: /wde2/backup/t520/tank/home/fk/.zfs/snapshot/2011-07-28_04:54/Mail/Tor/Read/16411: Input/output error
>fk@t520 ~ $dd if=/wde2/backup/t520/tank/home/fk/.zfs/snapshot/2011-07-28_04\:54/Mail/Tor/Read/16411 bs=1
>dd: /wde2/backup/t520/tank/home/fk/.zfs/snapshot/2011-07-28_04:54/Mail/Tor/Read/16411: Input/output error
>0+0 records in
>0+0 records out
>0 bytes transferred in 0.026960 secs (0 bytes/sec)
>fk@t520 ~ $sudo zfs send wde2/backup/t520/tank/home/fk@2011-07-28_04:54 | mbuffer | sudo zfs receive -v tank/corruption-test
>receiving full stream of wde2/backup/t520/tank/home/fk@2011-07-28_04:54 into tank/corruption-test@2011-07-28_04:54
>in @  0.0 KiB/s, out @  0.0 KiB/s, 1178 MiB total, buffer   0% fullwarning: cannot send 'wde2/backup/t520/tank/home/fk@2011-07-28_04:54': Input/output error
>summary: 1178 MiByte in  5min 44.0sec - average of 3508 KiB/s
>cannot receive new filesystem stream: checksum mismatch or incomplete stream
>
>Toggling vfs.zfs.send_corrupt_data allows to send the whole
>snapshot with the corrupted data:
>
>fk@t520 ~ $sudo sysctl vfs.zfs.send_corrupt_data=1
>vfs.zfs.send_corrupt_data: 0 -> 1
>fk@t520 ~ $sudo zfs send wde2/backup/t520/tank/home/fk@2011-07-28_04:54 | mbuffer | sudo zfs receive -v tank/corruption-test
>receiving full stream of wde2/backup/t520/tank/home/fk@2011-07-28_04:54 into tank/corruption-test@2011-07-28_04:54
>in @ 7193 KiB/s, out @ 7193 KiB/s, 1238 MiB total, buffer   0% full
>summary: 1239 MiByte in 43.6sec - average of 28.4 MiB/s
>received 1.21GB stream in 59 seconds (21.0MB/sec)
>fk@t520 ~ $sudo sysctl vfs.zfs.send_corrupt_data=0
>vfs.zfs.send_corrupt_data: 1 -> 0
>
>On the receiving side the corrupted block now has a valid checksum,
>the 0x'zfs badd bloc' pattern isn't obvious from userland and
>from ZFS's point of view the data is legit (which doesn't seem
>ideal either):
>
>fk@t520 ~ $hd /tank/corruption-test/Mail/Tor/Read/15654
>00000000  0c b1 dd ba f5 02 00 00  0c b1 dd ba f5 02 00 00  |................|
>*
>00001170
>fk@t520 ~ $sudo zfs send tank/corruption-test@2011-07-28_04:54 | dd of=/dev/null bs=1m
>0+198030 records in
>1238+1 records out
>1298720968 bytes transferred in 1.788083 secs (726320368 bytes/sec)
>
>Obtained from: ElectroBSD
>---
> sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_send.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_send.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_send.c
>index 9609761b38f9..a34fafe269df 100644
>--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_send.c
>+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_send.c
>@@ -71,6 +71,11 @@ int zfs_send_set_freerecords_bit = B_TRUE;
> 
> #ifdef _KERNEL
> TUNABLE_INT("vfs.zfs.send_set_freerecords_bit", &zfs_send_set_freerecords_bit);
>+
>+SYSCTL_DECL(_vfs_zfs);
>+SYSCTL_INT(_vfs_zfs, OID_AUTO, send_corrupt_data, CTLFLAG_RWTUN,
>+    &zfs_send_corrupt_data, 0, "Allow to send datasets with corrupt blocks. "
>+    "Blocks filled with 0x'zfs badd bloc' are send as replacement blocks.");
> #endif
> 
> static char *dmu_recv_tag = "dmu_recv_tag";
>-- 
>2.14.1
>

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Attachments on bug 221909: 185878