Bug#884938: XFS: possible memory allocation deadlock in kmem_alloc

[Salvatore Bonaccorso <carnil@debian.org>]

Control: tags -1 + moreinfo 

Hi Jason,

On Thu, Dec 21, 2017 at 11:30:28AM -0500, Jason Gill wrote:
> Package: src:linux
> Version: 3.16.51-3
> Severity: normal
> 
> Writing a large number of files to an XFS system with a larger
> directory block size causes slow performance and kernel log errors re:
> memory allocation deadlocks.
> 
> On the surface, looks very similar to this ubuntu issue:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1382333
> 
> This has been reproducible on 2/2 systems I've tried so far.
> 
> xfs_info output for the affected filesystem:
> meta-data=/dev/sdf               isize=2048   agcount=55, agsize=268435455 blks
>          =                       sectsz=512   attr=2, projid32bit=1
>          =                       crc=0        finobt=0
> data     =                       bsize=4096   blocks=14648409600, imaxpct=1
>          =                       sunit=0      swidth=0 blks
> naming   =version 2              bsize=65536  ascii-ci=0 ftype=0
> log      =internal               bsize=4096   blocks=521728, version=2
>          =                       sectsz=512   sunit=0 blks, lazy-count=1
> realtime =none                   extsz=4096   blocks=0, rtextents=0
> 
> To reproduce, make an XFS filesystem with a large directory block size:
> # /sbin/mkfs.xfs -n size=64k /dev/sdXX
> 
> Then mount the new filesystem and create a large number of small files quickly:
> $ seq -w 0 10000000 | xargs -P8 -n 256 touch

I have not looked into the fs/xfs history to find potential relevant
changes, but can you still reproduce the issue with recent kernels? In
a testsetup, but only quickly looked, I was not able to reproduce the
behaviour.

But possibly the issue could be still unfixed.

Regards,
Salvatore