misc/156241: 'zfs send' does not prevents disks to suspend if no other activity

Mickaël Canévet canevet at embl.fr
Thu Apr 7 07:30:11 UTC 2011


>Number:         156241
>Category:       misc
>Synopsis:       'zfs send' does not prevents disks to suspend if no other activity
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Apr 07 07:30:10 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Mickaël Canévet
>Release:        8.2-RELEASE
>Organization:
EMBL
>Environment:
FreeBSD 8.2-RELEASE FreeBSD 8.2-RELEASE #0: Thu Feb 17 02:41:51 UTC 2011     root at mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64
>Description:
I have a backup server with almost no I/O activity on which I want to export a ZPOOL to a USB disk.

When I do a 'zfs send my_backup_pool| zfs receive my_usb_backup_pool', the process hangs after a few minutes and dmesg reports this error message:

mfi1: COMMAND 0xffffff80004fe268 TIMEOUT AFTER 59 SECONDS
mfi1: COMMAND 0xffffff80004fbcb0 TIMEOUT AFTER 59 SECONDS
mfi1: COMMAND 0xffffff80004fbcb0 TIMEOUT AFTER 89 SECONDS
mfi1: COMMAND 0xffffff80004fbcb0 TIMEOUT AFTER 120 SECONDS
..

The problem solves as soon as I do a read on the source.

Is it possible that 'zfs send' bypasses some low level layers that prevents disks to suspend ?
>How-To-Repeat:
If you do this on a server with no I/O activity:

zfs send a_big_zpool | cat - > /dev/null

after a few minutes, you should have:

mfi1: COMMAND 0xffffff80004fe268 TIMEOUT AFTER 59 SECONDS
mfi1: COMMAND 0xffffff80004fbcb0 TIMEOUT AFTER 59 SECONDS
mfi1: COMMAND 0xffffff80004fbcb0 TIMEOUT AFTER 89 SECONDS
mfi1: COMMAND 0xffffff80004fbcb0 TIMEOUT AFTER 120 SECONDS
..

And as soon as you do a 'ls' for example on the zpool, 'zfs send' continues.
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted:


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