On Wed, Mar 02, 2016 at 02:43:04PM +0800, Xiong Zhou wrote:
mkdir failed IO error on pmem DAX ext2/3 fs mount using ext4 module.
This happends only on -next tree, not on Linus' tree,
at least from 4.5.0-rc5-next-20160224.
I was able to reproduce this and bisect it to the following commit:
commit 1f2d779fed21 ("ext4: optimize group search for inode allocation")
The fact that DAX was enabled in this failure was a red herring - it fails
without DAX as well. The key is just that we're mounting an ext2 formatted
filesystem using the ext4 module, I think.